catamaran planing speed

Catamaran Hull Speed Calculator For Beginners (Table and Free Spreadsheet)

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Speed is important, it can get you out of harm’s way, and it makes sailing much more fun, but figuring out how fast a catamaran will be able to sail can be tricky. One important aspect is to understand maximum hull speed.

In this article, I have calculated different hull speeds for different lengths of boats; this includes both monohulls and catamarans but focuses on the latter. Here is the catamaran maximum hull speed table:

Table of Contents

Catamaran Max Hull Speed Calculator Table

Length on Water		Displacement Max Hull Speed	Semi Planing Beyond Max Hull Speed
		0%	10%	20%	30%
Feet	Meter	Knots	Knots	Knots	Knots
26	8	6.9	7.5	9.1	11.8
30	9	7.3	8.0	9.6	12.5
33	10	7.7	8.4	10.1	13.2
36	11	8.0	8.8	10.6	13.8
39	12	8.4	9.2	11.1	14.4
43	13	8.7	9.6	11.5	15.0
46	14	9.1	10.0	12.0	15.6
49	15	9.4	10.3	12.4	16.1
52	16	9.7	10.7	12.8	16.6
56	17	10.0	11.0	13.2	17.2
59	18	10.3	11.3	13.6	17.7
62	19	10.6	11.6	14.0	18.1
66	20	10.8	11.9	14.3	18.6
69	21	11.1	12.2	14.7	19.1
72	22	11.4	12.5	15.0	19.5
75	23	11.6	12.8	15.3	20.0
79	24	11.9	13.1	15.7	20.4
82	25	12.1	13.3	16.0	20.8
85	26	12.4	13.6	16.3	21.2

Table Explanation

Length on the waterline (L.W.L.): Length of the boat when measured on the waterline, not to be confused with length overall (L.O.A.), which is the boat’s total length (above the waterline) including bowsprit, etc.
Displacement max hull speed: The max speed of a boat whose L.W.L doesn’t change when underway and where the vessel’s bow wave is the limiting speed factor.
Semi/Light Displacement or Semi planing hulls speed: A boat where the bow waves speed limiting factors can be partially overcome and therefore exceed the displacement hull speed. These hulls usually overcome hull speed by 10-30% .

How to use the Catamaran Hulls Speed Table

Choose your length on waterline in the left-most column, either in feet or meter.
Continue reading to your right and stop either at “Displacement hulls speed” or continue to “10,20, or 30%”, depending on your estimated hull efficiency. This will be your calculated maximum hull speed for a semi-displacement catamaran.

The Formula

First of all, we need to know the maximum hull speed for a displacement hull, and from that number, we will be able to calculate how much faster the semi-planing (or semi-displacement) hull will be. This is the formula for Maximum Hull Speed on a displacement boat:

Now we need to add the increased efficiency (loss of drag) of a semi-displacement hull, usually, this is somewhere between a 10-30% increase.

Note: “1.3” is the increase in efficiency, if you believe you are on the lower end of the scale this would be 1.2 or 1.1.

How to Exceed Hull Speed

This calculator offers a theoretical perspective, but many other factors such as sail plan, weight, and sailor skill, of course, have a profound impact on speed. As we have seen, a semi-displacement hull can exceed maximum hull speed, but we can also see that it isn’t by much. The next step is to reduce drag even further by utilizing a planning hull.

Catamaran Hull Speed Spreadsheet

If you want more info, calculate other lengths, or see the speeds in Km/h or Mph then I suggest you check out this free spreadsheet.

Catamaran Freedom Hull Speed Calculator

Note: If you want your own copy just click, File->make a copy.

Common Questions About Catamaran Hull Design

Below I will answer some of the questions I receive concerning catamaran hull design. The list will be updated as relevant questions come in.

Is a Catamaran a Planing hull?

As we have discussed above, a catamaran can definitely have a semi-planing hull, but can it be designed in a fully planing configuration as well?

Catamarans can be configured as planing hulls, although most sailing catamarans are set up as either semi-planing or hydrofoil. Due to the high speeds needed to get a boat to planing speed, this is only possible on racing sailboats or motor-powered catamarans such as high-speed ferries.

Owner of CatamaranFreedom.com. A minimalist that has lived in a caravan in Sweden, 35ft Monohull in the Bahamas, and right now in his self-built Van. He just started the next adventure, to circumnavigate the world on a Catamaran!

Catamaran Design Formulas

Post author By Rick
Post date June 29, 2010
10 Comments on Catamaran Design Formulas

Part 2: W ith permission from Terho Halme – Naval Architect

While Part 1 showcased design comments from Richard Woods , this second webpage on catamaran design is from a paper on “How to dimension a sailing catamaran”, written by the Finnish boat designer, Terho Halme. I found his paper easy to follow and all the Catamaran hull design equations were in one place. Terho was kind enough to grant permission to reproduce his work here.

Below are basic equations and parameters of catamaran design, courtesy of Terho Halme. There are also a few references from ISO boat standards. The first step of catamaran design is to decide the length of the boat and her purpose. Then we’ll try to optimize other dimensions, to give her decent performance. All dimensions on this page are metric, linear dimensions are in meters (m), areas are in square meters (m2), displacement volumes in cubic meters (m3), masses (displacement, weight) are in kilograms (kg), forces in Newton’s (N), powers in kilowatts (kW) and speeds in knots.

Please see our catamarans for sale by owner page if you are looking for great deals on affordable catamarans sold directly by their owners.

Length, Draft and Beam

There are two major dimensions of a boat hull: The length of the hull L H and length of waterline L WL . The following consist of arbitrary values to illustrate a calculated example.

L H = 12.20 L WL = 12.00

After deciding how big a boat we want we next enter the length/beam ratio of each hull, L BR . Heavy boats have low value and light racers high value. L BR below “8” leads to increased wave making and this should be avoided. Lower values increase loading capacity. Normal L BR for a cruiser is somewhere between 9 and 12. L BR has a definitive effect on boat displacement estimate.

B L / L	In this example L = 11.0 and beam waterline B will be:
Figure 2
B = 1.09	A narrow beam, of under 1 meter, will be impractical in designing accommodations in a hull.
B = B / T	A value near 2 minimizes friction resistance and slightly lower values minimize wave making. Reasonable values are from 1.5 to 2.8. Higher values increase load capacity. The deep-V bottomed boats have typically B between 1.1 and 1.4. B has also effect on boat displacement estimation.

T = B / B T = 0.57	Here we put B = 1.9 to minimize boat resistance (for her size) and get the draft calculation for a canoe body T (Figure 1).
	Midship coefficient – C
C = A / T (x) B	We need to estimate a few coefficients of the canoe body. where A is the maximum cross section area of the hull (Figure 3). C depends on the shape of the midship section: a deep-V-section has C = 0.5 while an ellipse section has C = 0.785. Midship coefficient has a linear relation to displacement. In this example we use ellipse hull shape to minimize wetted surface, so C = 0.785
Figure 3


C =D / A × L	where D is the displacement volume (m ) of the boat. Prismatic coefficient has an influence on boat resistance. C is typically between 0.55 and 0.64. Lower values (< 0.57) are optimized to displacement speeds, and higher values (>0.60) to speeds over the hull speed (hull speed ). In this example we are seeking for an all round performance cat and set C := 0.59


C = A / B × L	where A is water plane (horizontal) area. Typical value for water plane coefficient is C = 0.69 – 0.72. In our example C = 0.71


m = 2 × B x L × T × C × C × 1025 m = 7136	At last we can do our displacement estimation. In the next formula, 2 is for two hulls and 1025 is the density of sea water (kg/m3). Loaded displacement mass in kg’s


L = 6.3	L near five, the catamaran is a heavy one and made from solid laminate. Near six, the catamaran has a modern sandwich construction. In a performance cruiser L is usually between 6.0 and 7.0. Higher values than seven are reserved for big racers and super high tech beasts. Use 6.0 to 6.5 as a target for L in a glass-sandwich built cruising catamaran. To adjust L and fully loaded displacement m , change the length/beam ratio of hull, L .


m = 0.7 × m m = 4995	We can now estimate our empty boat displacement (kg): This value must be checked after weight calculation or prototype building of the boat.


m = 0.8 × m m = 5709	The light loaded displacement mass (kg); this is the mass we will use in stability and performance prediction:


	The beam of a sailing catamaran is a fundamental thing. Make it too narrow, and she can’t carry sails enough to be a decent sailboat. Make it too wide and you end up pitch-poling with too much sails on. The commonly accepted way is to design longitudinal and transversal metacenter heights equal. Here we use the height from buoyancy to metacenter (commonly named B ). The beam between hull centers is named B (Figure 4) and remember that the overall length of the hull is L .

Figure 4


	Length/beam ratio of the catamaran – L
L = L / B	If we set L = 2.2 , the longitudinal and transversal stability will come very near to the same value. You can design a sailing catamaran wider or narrower, if you like. Wider construction makes her heavier, narrower means that she carries less sail.

B = L / L B = 5.55	Beam between hull centers (m) – B

BM = 2[(B × L x C / 12) +( L × B × C x (0.5B ) )] × (1025 / m ) BM = 20.7	Transversal height from the center of buoyancy to metacenter, BM can be estimated

BM = (2 × 0.92 x L × B x C ) / 12 x (1025 / m ) BM = 20.9	Longitudinal height from the center of buoyancy to metacenter, BM can be estimated. Too low value of BM (well under 10) will make her sensitive to hobby-horsing

B = 1.4 × B	We still need to determine the beam of one hull B (Figure 4). If the hulls are asymmetric above waterline this is a sum of outer hull halves. B must be bigger than B of the hull. We’ll put here in our example:

B = B B B = 7.07	Now we can calculate the beam of our catamaran B (Figure 4):

Z = 0.06 × L Z = 0.72	Minimum wet deck clearance at fully loaded condition is defined here to be 6 % of L :

	EU Size factor
SF=1.75 x m SF = 82 x 10	While the length/beam ratio of catamaran, L is between 2.2 and 3.2, a catamaran can be certified to A category if SF > 40 000 and to B category if SF > 15 000.

	Engine Power Requirements
P = 4 x (m /1025)P = 28	The engine power needed for the catamaran is typically 4 kW/tonne and the motoring speed is near the hull speed. Installed power total in Kw
V = 2.44 V = 8.5	Motoring speed (knots)
Vol = 1.2(R / V )(con x P ) Vol = 356	motoring range in nautical miles R = 600, A diesel engine consume on half throttle approximately: con := 0.15 kg/kWh. The fuel tank of diesel with 20% of reserve is then

Tags Buying Advice , Catamaran Designers

Owner of a Catalac 8M and Catamaransite webmaster.

10 replies on “Catamaran Design Formulas”

Im working though these formuals to help in the conversion of a cat from diesel to electric. Range, Speed, effect of extra weight on the boat….. Im having a bit of trouble with the B_TR. First off what is it? You don’t call it out as to what it is anywhere that i could find. Second its listed as B TR = B WL / T c but then directly after that you have T c = B WL / B TR. these two equasion are circular….

Yes, I noted the same thing. I guess that TR means resistance.

I am new here and very intetested to continue the discussion! I believe that TR had to be looked at as in Btr (small letter = underscore). B = beam, t= draft and r (I believe) = ratio! As in Lbr, here it is Btr = Beam to draft ratio! This goes along with the further elaboration on the subject! Let me know if I am wrong! Regards PETER

I posted the author’s contact info. You have to contact him as he’s not going to answer here. – Rick

Thank you these formulas as I am planning a catamaran hull/ house boat. The planned length will be about thirty six ft. In length. This will help me in this new venture.

You have to ask the author. His link was above. https://www.facebook.com/terho.halme

I understood everything, accept nothing makes sense from Cm=Am/Tc*Bwl. Almost all equations from here on after is basically the answer to the dividend being divided into itself, which gives a constant answer of “1”. What am I missing? I contacted the original author on Facebook, but due to Facebook regulations, he’s bound never to receive it.

Hi Brian, B WL is the maximum hull breadth at the waterline and Tc is the maximum draft.

The equation B TW = B WL/Tc can be rearranged by multiplying both sides of the equation by Tc:

B TW * Tc = Tc * B WL / Tc

On the right hand side the Tc on the top is divided by the Tc on the bottom so the equal 1 and can both be crossed out.

Then divide both sides by B TW:

Cross out that B TW when it is on the top and the bottom and you get the new equation:

Tc = B WL/ B TW

Thank you all for this very useful article

Parfait j aimerais participer à une formation en ligne (perfect I would like to participate in an online training)

Planing and the Need for Speed

Surfers require waves in order to move, and windsurfers certainly will hitch a ride on one if they feel like it, but windsurfers can also achieve speed on flat water. The current speed record for any sail-powered craft on water is held by windsurfer Finian Maynard of the British Virgin Islands, who maintained an average speed of 48.7 knots (54 mph) over a 500-m course in April 2005. This achievement beat the previous record of 46.5 knots set by a catamaran in 1993. The nautical mile record is also currently held by Maynard (39.97 knots), according to the World Sailing Speed Record Council; Maynard's record has recently been beaten by Bjorn Dunkerbeck, who reached 41.14 knots, though this speed has yet to be verified. Clearly, over long distances yachts are always going to beat sailboards, and the yacht speed specialists are catamarans.* Equally clearly, over short distances the sprint specialists are now sailboards. The records are falling quickly, and I would be willing to bet that the 500-m and nautical-mile records just quoted will be out of date by the time this book goes to print.

The big advantage that sailboards hold over yachts is that they can plane over the water rather than plow through it (see fig. 7.9; planing is

*You are now in a position to understand why: cats have less wetted surface and so less drag than monohulls . Less drag means more speed. Catamarans have a wider beam and hence greater initial stability, which means that they can fly taller sails without a likelihood of capsizing. More sails mean more drive means more speed.

also evident in figs. 7.1 and 7.4). So how does a sailboard permit planing? It is a simple hydrofoil—a wing that provides vertical lift by presenting itself to the water surface at a controllable angle of attack. This is a particularly simple type of lift to visualize; as with, for example, a water ski or a rudder, we can think in terms of momentum transfer. Water impinging on the lower surface of the board is deflected downward so that the board is pushed up. A modern sailboard with a 6-8 m2 sail will plane when it reaches a speed of 12 knots. If the sail area is increased to 10-12 m2, the minimum planing speed is reduced to 8 knots. Wide boards plane at lower speeds; they do not reach the top speeds of narrow boards because of their greater drag. Boards with a tail rocker—an upward curve at the back, which provides improved maneuverability—require higher speeds before they plane. There is a hull speed barrier to overcome before planing is attained, but this barrier is small for sailboards.

The physics of chapter 4, in which I developed a fairly simple equation of motion for fore-and-aft rigged vessels, can be taken over (with suitable adjustments) to describe sailboard movement. The parenthetic ''with suitable adjustments'' requires some explanation because of the significant differences between Bermuda-rigged yachts and sailboards. Obviously, parameters such as mass and sail area change from yacht values to sailboard values, but the differences go deeper, as we have seen. That is, I cannot just apply the equations derived in chapter 4 with windsurfing parameters substituted for yacht parameters. I must account for these facts: (1) sailboards make significant leeway—they are blown downwind because they lack a keel to resist such motion; and (2) sailboards operate in shallow water.

The island of Tiree off the west coast of Scotland is isolated, barren, beautiful, and full of windsurfers. Those of you who have been to Scotland will know that the climate there is not exactly the balmy, sun-drenched, palm-fringed paradise that windsurfers find in Hawaii, so what is it about this particular island that draws windsurfers on the 8-hour ferry ride from the mainland of Scotland? Like many of the Western Isles, Tiree is buffeted by winds during most of the short summer months, but unlike other islands, Tiree has beaches all around its coast. Consequently, it is always possible to find a beach for which the capricious winds blow onshore. This is important for windsurfers because if they drift on the ocean surface for whatever reason, they would like to drift toward a beach rather than out to sea. In more benign climates with more reliable winds, they may be reasonably sure that a chosen beach will always provide them with a safe onshore breeze (and big plunging waves, as in Hawaii), but the weather in Scotland is harsh and variable— and so Scottish windsurfers go to Tiree.

This last paragraph was not inserted at the behest of the Tiree Tourist Board but instead serves to show that, quite often, windsurfing is carried out on beaches with an onshore breeze. I will assume in my calculations that this is the case. Thus, the wind direction is pretty much the same as the wave direction—recall that waves straighten up when approaching a beach. So, waves will push our sailboard towards the beach, and wind will cause it to drift in the same direction. I can simply add these two effects when accounting for them in my physics calculations. This is most conveniently done by assuming that the effect of wind and water together cause the sailboard to drift with the wind at a speed sw. Recall that w is wind speed, so here I am saying that leeway and wave drift combine to cause the board to move with the wind at some fraction, s, of the wind speed. Of course, the windsurfer may point his board in any direction he pleases and trim his sail to provide maximum speed in this direction, but whatever he does, his board will always have an additional component of velocity, sw, in the wind direction.

When I apply the chapter 4 equation of motion to windsurfing, I must remember that the effective wind velocity experienced by the windsurfer is not w but is instead (1-s)w because of the onshore drift. This will change the apparent wind2 and will result in a different equilibrium velocity over the water (compared with the equilibrium velocity we found for yachts). To see how fast sailboards can go, however, we are interested in determining the equilibrium velocity relative to the land, not the water, and so must add the drift velocity sw to the calculated equilibrium velocity. Before, we made no distinction between velocity relative to the water and velocity relative to land because we assumed that there was no net water movement. Here, we need to account for the fact that our sailboard is on water which is moving toward the shore. Einstein the sailor would approve of all this relativity. Math details are provided in note 3 for those of you who are interested in derivations; for those of you who are not the results will soon be presented conveniently in a graph.3

Before showing you these theoretical results for sailboard equilibrium speed, I need to take into account the fact that sailboards plane. This is easy: the hydrodynamic drag is much reduced, and so I will make the simplifying approximation that it is negligible for the purposes of determining equilibrium speed. Given this simplification, which I made in chapter 4 for iceboats, we start with the equation for iceboat equilibrium speed, already determined as equation (4.4) of chapter 4:

We do not accept this equation as it stands: we must include the consequences of water movement and leeway, discussed above, before it applies to windsurfing. In addition we must use lift and drag coefficients cLD that pertain to sailboards. With a well-trimmed sail it has been found that windsurfers' sails can provide an L/D ratio of 6:1 or 7:1, so I adjust the yacht lift and drag coefficients (fig. 4.4) accordingly and obtain figure 7.10. Next, I substitute these coefficients into equation (7.1) and do the "relativity" thing: include board drift and determine the board speed relative to water and then relative to land. The results are shown in figure 7.11 for three different choices of the drift factor s.

How do I know what this factor should be? Well, I don't, and it will vary with windsurfing circumstances and with sailboard dimensions. So

Figure 7.10. (a) Lift and drag coefficients CL CD vs. angle of attack (AoA) in degrees. These are the coefficient values that I adopt for my sailboard calculations. (b) A comparison with the lift and drag coefficients for yachts given in fig. 4.4 shows the increased peak lift/drag ratio. (c) Sailboard lift coefficient vs. drag coefficient.

120 140 160 180 Heading angle (degrees)

Figure 7.11. Windsurfer's equilibrium speed (divided by wind speed) vs. heading direction, for different "drift factors'' (denoted by s). Dashed lines show the equilibrium speed relative to the water. Bold lines show equilibrium speed relative to land, which is what matters. The simple mathematical model shows that windsurfers can move faster than the wind, when on a beam reach or a broad reach. (A heading angle of 0° corresponds to downwind.) For each case plotted there is a maximum heading angle beyond which the board is effectively going backwards—in other words, the windsurfer is facing into the wind but drift is pushing him back. I assume that the windsurfer doesn't want to go there, so I won't either; I have not plotted this part of the curves.

I have chosen three middling values and plotted the results. If you disagree with my choice, you can substitute different s values in the equation (see endnote 3) and plot your own graph. The point is that it doesn't really matter because the plots show the same broad result; because my simple model is aimed at providing you with understandable physics, it will accept approximate answers. Figure 7.11 shows that windsurfers can go faster than the wind when heading on a broad or beam reach— in other words, when going across the wind or slightly downwind. A beam reach is convenient for those windsurfers (not a few, I suspect) who want to go as fast as possible while riding the front of a wave. Without accounting for board onshore drift, the calculations show that windsurfers' top speed is attained on a close reach—heading slightly to windward, as is shown in figure 7.11. This is not found to be the case in practice.

To summarize, we have seen here how the simple type of analysis used to gain insight into fore-and-aft yacht motion can be adapted and applied to sailboards. The adaptation is required to account for the onshore drift that we expect sailboards to encounter because they are unable to resist leeway and because they often ride waves and so drift with the water. Our results show that sailboards can go significantly faster than the wind that powers them. This observation suggests that sailboards might be able to ''create their own wind'' when on a beam reach, which in fact seems to be the case, as further calculations show.4

Continue reading here: Pumping and the Katzmayr Effect

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Other High-Speed Multihull Craft

First Online: 30 October 2018

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Liang Yun 4 ,
Alan Bliault 5 &
Huan Zong Rong 4

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In previous chapters we introduced catamarans of a displacement or semiplaning type with some information on resistance for the planing hull form as used mainly by wave piercers. We explained that, owing to the catamaran demihull’s slender length/beam ratio aimed at reducing wave-making drag, such craft would not operate in the planing region as the Froude number Fr l remains below around 0.75, even for high service speed (Table 1.1 ), so the hydrodynamic lift proportion would not be more than 20% of displacement, even if a hard chine demihull form is used. In this chapter we will discuss other design alternatives for high-speed vessels, including those targeted at speeds above Fr l = 1.0.

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Yun, L., Bliault, A., Rong, H.Z. (2019). Other High-Speed Multihull Craft. In: High Speed Catamarans and Multihulls. Springer, New York, NY. https://doi.org/10.1007/978-1-4939-7891-5_10

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PERFORMANCE TOPICS

Optimising Hull Lines for Performance

This article was inspired by a question about the rocker line in the new 8.5m cat Design 256 and I want to stick to the point, so we won’t turn it into a book, but I’ll discuss two issues, hull fineness ratio and some aspects of the rocker profile.

When you manipulate the hull form you’re adjusting the lines in three planes, waterplanes (plan view), buttocks (side view including the keel rocker) and the section shapes. So you need to be aware of how the shapes are changing in the other two planes as you manipulate any one of these three, or all three globally as is now possible with computer modelling.

There are two fundamental constants that you start with and don’t change throughout the process. The big one is the displacement or the amount of buoyancy you need.

If you make the hull finer by narrowing the waterlines you have to increase the draft or make the ends fuller to get back to the required displacement number.

If you flatten the rocker line you have to increase the hull width, fill out the ends, or square up the section shapes rather than having a V or rounded V.

The other constant is the longitudinal centre of buoyancy. You really can’t do any meaningful shaping of the hull form until you have settled on the these two constants.

A third number that we can plug in as a constant if we want to is the prismatic coefficient which describes bow much volume there is end the ends relative to the cross section shape in the middle of the boat, but in sailing boats this is of less importance compared to other factors.

The hull lines for Design 256, 8.5m Cat. It's that hump in the rocker line - right under the back of the cabin that brought up the question and is one of the key points discussed here.

Hull fineness.

Fine hulls are fast, but only in the higher speed range. There’s a misconception I come across quite a bit that you can add weight and windage and you’ll still be fast as long as your hulls are fine.

Well you won’t be. Your boat will simply sink to find the new state of equilibrium. If your transoms are submerged you’ll have more drag. If your bridge deck is too close to the water you’ll have slamming. Much better to be conservative with your displacement figure in the design stage than overly optimistic.

And fine hulls have more wetted area so you have more drag in light air where friction resistance is the primary drag factor.

I’ve seen promotional material for catamarans stating that the boat has less wetted area because it has fine hulls. For a given displacement the minimum wetted area is described by a sphere (or a semi sphere in the case of a floating object). The more you stretch it out in length, keeping the displacement constant, the more wetted area you have.

The more you make the section shape into a deep V or a broad U with tight corners, as opposed to a semicircle, the more wetted area you have. Add into the equation finer hulls are slower to tack.

So fine hulls are only an advantage if your boat is light and has enough sail area to ensure you’re travelling at speeds where form resistance is greater than skin resistance.

In my view the advantage of fine hulls is often overrated as it applies to cruising cats.

At the other end of the scale the resistance curve is fairly flat up to about 1:9 which is still quite fast in most conditions. From there the resistance rises steeply as the hull gets fatter and at 1:8 and fatter you’re suffering from some serious form drag.

Illustration of buoyancy distribution in catamaran hull

This is the rocker line isolated from the lines plan above (in blue) and and the red line shows a more moderate rocker line that achieves the same buoyancy and maintains the centre of buoyancy in the same position. The bow is to the right.

In the image lower right I've squashed it up and increased the height to make the difference in the lines more obvious.

The difference in the two lines is quite subtle, but races are often won or lost by seconds.

Rocker Profile

So if we’re looking for low wetted area we would want a rocker profile that was even and rounded, relatively deep in the middle and rising smoothly to the surface at each end. But this would give us a low prismatic which is not ideal in the higher speed range, and it’s not ideal for pitch damping which in my view is the critical design factor that is often underrated.

Pitching is slow. It destroys the airflow in your sails and the flow around the hulls, and your performance is suffering from slamming loads.

The single most effective way to counter pitching is with asymmetry in the water planes. You can achieve that in the with a fine bow and broad transom. Or you can achieve it with V sections forward and a flattened U shape aft. Or you can achieve it in the profile view with a very straight run forward and a bump in the aft sections. A flatter rocker line is better for resisting pitching than an evenly curved one with deeper draft in the middle.

The final result is a combination of all three of these factors.

On a cat like Design 256 the weight is concentrated well aft so we need to get buoyancy well aft.

The kink you see in the rocker profile helps to do this. It also helps to keep the rocker straight for most of its length and smooth the water flow exiting the hull aft at higher speeds, possibly promoting some planing effect.

If we had a more even rocker line we would slightly reduce the wetted area, but we would increase the pitching and the water would exit the hull aft at a steeper angle, increasing form drag in the higher speed range.

How much of a bump can you put in there without creating a flow separation, and how damaging would that flow separation be? I really don’t know. The way all of these factors interplay in the various conditions we sail in is very complex.

Ultimately a lot of this work is gut feel nurtured by experience, observing things in nature and most importantly experimenting and trying new ideas.

Is the new Groupama AC45 a breakthrough that will influence the form of racing catamarans into the future? I don’t think anyone has a computer that can answer that. We have to wait and see.

Catamaran hull lines showing symmetric and asymmetric waterplanes

Symmetric and non symmetric water-planes. The blue line with grey fill is the DWL from the design above. As is typical with modern cat hulls the bow is long and fine, the stern is full and rounded. This is the asymmetry that has a damping effect on pitching. The red line on the other hand is more like you would see on a double ended monohull and quite a few multihulls have also used this shape in the past. It's quite symmetric about the pitch axis and does not have good pitch resistance.

Lines plan for the Livewire 28 Catamaran

The hull lines of the new 8.5m Sports Cat Design 256

Mad Max , Previously Carbon Copy . She was designed in 1997 but she's the current (2016) title holder of the Australian Multihull Chamionships (2 successive years) and the fastest inshore racing boat in Australian waters.

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Yachting World

Digital Edition

Catamaran sailing: expert multihull techniques

Nikki Henderson
February 18, 2022

Moving to a performance multihull can be a leap for even the most experienced cruiser. Nikki Henderson shares expert multihull techniques.

There has been a huge surge in the sales of performance multihulls and with them a need to know how to handle them particularly when it comes to specific multihull techniques. The market for these boats is broadening; multihull cruisers are upgrading, monohull sailors are upsizing, and even virgin boat owners are tempted.

Over the last 12 months, while coaching for Outremer , I’ve met hundreds of these owners, everyone from young families to retired couples moving aboard a new catamaran and setting sail on a circumnavigation. Handling a performance catamaran is achievable even for a novice multihull sailor. But there is a big difference between just ‘getting by’ on such a boat versus sailing efficiently, safely and in style.

The transition for even experienced sailors can be quite a step up. For a seasoned monohull sailor, the differences are obvious: increased volume and speed, and a lack of heel. Even for an existing multihull sailor, the handling and performance is noticeably less forgiving and requires a shift in focus and technique.

This winter, I set sail on a transatlantic with the new owners of an Outremer 55 . They have previously owned another less performance-orientated catamaran but invited me on board to coach them to fine tune the boat, assist with routing, and help them take best advantage of all the performance their new yacht offers. Here are a few of the topics we focussed on:

sailing at higher speeds will change everything from manoeuvre techniques to weather routing. Photo: Robin Christol/Outremer

Most non-planing monohulls will do approximately the same speed on all points of sail. However, a performance multihull might sail at twice, three, even four times its upwind speed on a reach.

For example, the factory polars of an Outremer 55 give its average speed in 20 knots of wind with a true wind angle (TWA) of 50° at 8.5 knots, but in the same windspeed with a TWA of 110° it’s 19.1 knots. That’s more than twice as fast. How do you make the most of this speed advantage? And how do you best manage it ?

In a monohull it often pays to slog it out for days sailing the best course to windward as this normally gives the best velocity made good (VMG). A dead downwind rhumbline route is the usual strategy for longer ocean passages, rather than sailing more miles and wider angles.However, on a performance multihull it is important to prioritise reaching when route planning.

aboard high performance catamarans, such as this TS42, you can race competitively in offshore events. Photo: Jacques Vapillon/Sea&Co

In upwind conditions on a long crossing, consider whether bearing off by even as much as 20° will result in a better VMG, even if it feels counterintuitive. In light winds bearing off to 70° or 80° TWA can be the difference between a totally stalled boat and 5 knots of boat speed .

Faster speeds open up the possibility of keeping up with pressure systems as they move around the globe. For example, if crossing the North Atlantic eastwards, ideally you’d leave the US in clear weather with a depression forecast to leave the American coast a few days later.

You could use its predicted track to decide how much north or south to add to your easterly heading, to ensure that as it catches up with you, you are sufficiently south enough of it to pick up its strong westerlies. As they approach, you will accelerate, and if you can hold the speed you can use that downwind airflow to push you most of the way across the pond.

Handling at speed

Controlling and handling the boat at these higher speeds requires a change in strategy. Increased speeds and acceleration mean that the apparent wind angle and apparent wind speed change much more frequently. So you need adaptable and flexible trimming and driving solutions.

Use twist to balance power and control. Photo: Robin Christol/Outremer

Downwind the boat should be carving S-curves through the water to ensure it achieves the best VMG possible. If you can get this right you will attain the momentous double figure average speeds that a performance multihull offers, while also going the right direction! Instead of allowing the speed to plummet at the end of each surf, as the bow sinks into the bottom of the wave, a performance multihull can just keep on going.

How to maintain speed:

1 Sail at higher angles to build up apparent wind speed (AWS) and boat speed.

2 Soak downwind as the apparent wind angle (AWA) surges forward with the acceleration.

3 Drive the boat back slowly upwind in time to maintain the average speed and continue the surf.

In an ideal world, to achieve this the boat would be hand-steered. But realistically, no cruisers want to be on deck for two weeks straight on a transatlantic crossing. Your best compromise is to invest in a top quality, well set up autopilot, as well as good wind instruments.

Set the autopilot to sail to apparent wind angle and watch how the boat slaloms through the ocean. The quality of the autopilot will really start to show its value when the sea state starts to increase. The best ones improve over time as they collect data and learn the wave patterns. If you aren’t sure exactly which AWA is ideal, choose a day that has very consistent wind and sail in open water. Set the autopilot AWA to 90° and then systematically increase the setting by increments of 5° at fixed time intervals until you get as low as you can before the foresail is shadowed behind the main. Measure the VMG by comparing the distance travelled at each of the different wind angles, and the average A to B course over ground (COG) achieved. This will give you a good starting point, and then it will shift further depending on sea states and wind strengths.

Sail setting

Another solution if you want fast speeds but don’t want to actively sail the boat to within an inch of its life is to use twist. Twist is a compromise between having a hardened sail that stalls when the wind goes aft, or a very eased sail that luffs when it goes forward. The more changeable the conditions, the more extreme the acceleration increases are, or the rougher the sea state is, the more twist you need.

Cats have the space and stability to hoist and douse, so keep weight low by dropping flying sails when not in use. Photo: Christophe Launay

The wide beam of a multihull allows for a long traveller, so most won’t have a vang. Sheet tension and traveller position are your primary controls to create twist in the mainsail. Begin by finding a full power setting in the main.

Set your autopilot to 35-40°AWA; most performance multis should make this upwind. Set your traveller at midships and over-ease your mainsheet so that the sail is luffing. Gradually tighten your mainsheet until the top telltale just flies. Manual winching offers better control here than electric.

Pull your traveller to windward until the boom runs down the centreline. The top telltale of the mainsail will now be flying about three-quarters of the time. If it is closer to 50% you may need to tighten the mainsheet further and then ease the traveller until you have achieved this (or vice versa). This is your full power sail shape, and your default car position upwind.

At this point some people like to mark the mainsheet (this doesn’t work with a continuous mainsheet). To begin with, just take note of the traveller position. If the conditions require more twist, ease the mainsheet, and pull the traveller to windward to keep the boom in the same position relative to the boat. You could keep a note of three traveller positions for each point of sail: full power, mid power, low power.

As the wind moves aft, you can add other ‘go-to’ traveller positions for different wind angles by easing the traveller down to leeward while keeping the mainsail shape set to ‘full-power’ mode. Once the wind goes aft of the beam, your traveller will be all the way down to leeward. Keep an eye on spreader chafe at this point.

Once you are happy with mainsail trim, you can trim the jib in a similar way, using car position and the sheet tension. Bring sheet tension in so that the leech shape looks very similar to the main: flat with a slight curve at the top. Then adjust the cars (if you can) so that the sail is not luffing, and the top telltales are also flying 50-75% of the time. Finally, walk forward to the forestay and view the slot between the sails. Do they look roughly parallel? If not, you may need to open up the slot a touch by moving the car outboard. This is your default jib car position for that point of sail.

Sailing the angles with an asymmetric. Photo: Kinetic Catamarans

When conditions increase, don’t forget to add twist to the jib too. Initially just ease a touch of sheet. Be careful moving the car too far inboard or you might close the slot. Moving the sheet attachment closer to the foot of the clew will open up the leech and create more twist.

Think of twist as the middle ground between sailing fully powered and reefing. Multihulls are much less communicative than monohulls. You do not have the obvious signs that the boat is overpowered, like a submersed toe rail or rounding up as the boat heels.

In time you’ll get to know your catamaran and build a connection to read how aggressively the boat is accelerating, its fore-aft pitching, sounds, and rhythm. But at first it’s useful to have some number guides and wind parameters of when to add twist and ultimately when to reef.

Generally a performance cat will require a reef much earlier because it’s lighter. I’d usually put in one reef at 20-25 knots, two at 25-30 and three reefs for 30-35 knots.

On our transatlantic crossing on the Outremer 55, contrary to my advice on the advantages of sailing angles downwind, we chose instead to sail dead downwind with the symmetric spinnaker up for the entire passage.

taking it easy dead downwind under symmetric Photo: Nikki Henderson

There are costs to taking full advantage of the speed of a performance catamaran. Averaging 15 knots boat speed is not everyone’s idea of comfortable. The hulls are so stiff that every wave that hits the hull sounds like the beating of a drum. The humming of carbon rigging, the swooshing of water screaming past the topsides, the slapping of the waves, the wind: it’s incredibly loud even when averaging 10 knots, let alone 15 or 20.

Performance multihulls are also so lightweight that they are really thrown about in a substantial sea state. Our decision to sail dead downwind rather than heating up and taking full advantage of the performance came down to the following reasons:

1. Lack of adequate autopilot We had one, but it wasn’t able to react quickly enough to the acceleration and resulting rapid change of wind angle that broad reaching would have created. It also struggled in a big seaway, so sailing with the waves square on to the stern was easier to cope with.

2. Sails We did not have a heavyweight asymmetric sail, which is what you need to sail these downwind angles (both our reaching sails were light weight).

3. Safety Akaroa II is hull No2 of a new design by Outremer. This was the first transatlantic crossing that this particular model of boat had ever done, so we were a testing ground and deliberately cautious.

Despite our conservative approach we still achieved 90% of the factory polars averaging 9.6 knots in sustained winds of 20 knots across the entire 2,700-mile route.

The trip took 11 days and 17 hours. The beauty of a performance multihull is that even if you don’t push it, you still manage brilliant speeds in the right conditions.

We calculated how much faster we would have gone, had we sailed the angles instead of running downwind. This assumes we would achieve the same 90% polars. TWA 140° appears to be the sweet spot.

Getting the main down when reefing can be problematic – rig up downhaul lines to help grind it down if needed. Photo: Nikki Henderson

Without any power being dispelled by heeling, performance multihulls will convert additional power into acceleration. With this increased speed comes increased loads on the lines, blocks, rudders, sail cloth and rigging. Winches are upsized. Jammers are used instead of clutches. Halyards are 2:1. You may be sailing on a 50-footer, but the loads are akin to a 70-80ft bluewater monohull.

A future owner recently reminded me of this, when he opened the main traveller jammer while holding the line with only one wrap on the winch. The lack of skin on his hand was gruesome evidence of how surprising the loads can be when a multihull is really powered up.

Interestingly, comparing a standard cruising multihull with a similar sized performance multihull, the opposite is true. A boat that weighs less needs less sail area to power it. For example, a Lagoon 450 has a sail area (main and jib) of 130m2 compared to an Outremer 45 (actually 48ft LOA) at 104m2. So, for the same apparent wind speed, there will be less load on the gear.

Watch out when sailing downwind. Due to a performance multihull’s ability to accelerate and hold high speeds downwind, it is easy to hold significantly more sail area in higher true wind speeds as the apparent stays low. However, if you do hit the bottom of a wave and stop dead in the water, the sail, rigging and lines will feel the full force of that wind.

Another reason to reef earlier than you think on a performance multi is that with swept back shrouds (needed to support the mast without a backstay) and a fully battened mainsail, even with the halyard eased downwind the sail may still not come down. You should be sailing with the minimum amount of sail cloth up to achieve the polars.

Reducing sail

1. Rig up downhaul lines from each reefing point on the luff to help grind down the sail. Keep an eye on chafe on the leeward side on each of the batten pockets.

2. Use the rotating mast to open the sail to the wind more.

3. If that isn’t enough, come upwind to help get the sail down.

Multihull trim

Switching to a performance catamaran may bring new trimming options: daggerboards, a rotating mast, and fully battened square topped mainsail.

Brush up on your fundamentals of sail trim so that you have a solid foundation to build on. When you first start sailing the boat, to avoid getting overwhelmed (which tends to result in people under-sailing their boat), begin by finding a base setting for all points of sail. Forget the rotating rig for now, but find enough twist in the sails that gives you enough height without too much power. Set the daggerboards as you would on a dinghy: down for upwind, up for downwind, mid-way for a reach. Then you fine tune.

Set performance cat daggerboards as you would for a dinghy at first: down for upwind, up for downwind, mid-way for a reach. Photo: Nikki Henderson

When adjusting daggerboards, make sure you have your GPS track switched on. See if dropping a little more daggerboard helps with the COG upwind. Downwind, if you feel like you are on an ice-skating rink, try dropping a little board for better grip. If on autopilot, take note of the rudder angle. If it’s taking the helm from full starboard to full port then it might need some more grip, if not then a reef.

Be cautious of the risk of ‘tripping up’ in big seaways. In sea states much over 3-4m, it’s safest to lift the daggerboards and allow the boat to glide over the waves rather than risk one of the boards digging into a wave and destabilising the boat. While exceptionally unlikely to happen, if a daggerboard digs in, the worst case scenario would be a capsize. If you see any slick in the water that suggests the boat is sliding sideways over a wave, or an increase in heel, or significant water over the deck – these are signs that it’s time to lift the boards all the way up.

Finally, play with the rotating mast. At a basic level, try to get the mast in line with the foremost sail position and curve. The easiest way to see this is actually to stand forward of the mast and look down the line of the sail. It is in itself a foil and when in the right position can add the equivalent of as much as 10% more sail area. In the same way, you can use it to depower by reducing the angle.

With a rotating mast you’ll generally be trying to get it in line with the foremost sail position and curve. Photo: Nikki Henderson

When fine tuning sail trim I’d recommend marking all your tracks and angles of mast rotation, and once you are confident you could mark the sheets and halyards themselves. This is an exercise for the detail-orientated and it pays to be specific. Keep a notebook at the helm station to record your learnings, and over time build up not just ideal trim settings for wind and waves, but also polars.

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Learning a performance catamaran’s sensitivity to weight can be a real learning curve. Compared to cruising catamarans, performance cats tend to be half the weight (or even less). Meanwhile, compared to a monohull the main difference is in the areas where the weight is most concentrated. A monohull’s weight is predominantly in its keel. Almost the entire weight of the boat is concentrated in around 15% of the boat’s length. Conversely, a multihull has no keel, so without that pendulum effect its centre of gravity is higher and less stable. On a multihull the weight is distributed along almost 90% of its length.

In practice, this means that what you carry, both below and above decks, has a big impact on the boat’s performance and safety. The first step is to become minimalists. Summon your inner Marie Kondo and ask yourself “Does this bring me joy? Does this keep me safe?” of every single item that moves from dock to boat. If it doesn’t – don’t take it.

Performance cats are weight sensitive so streamline your possessions onboard. Photo: Carl Newton

Step two is to arrange your belongings evenly around the boat. Ensure you don’t list the boat to port or starboard. Try to keep weight amidships and ideally low down. Avoid loading up the bow lazarettes or aft areas with too much weight.

When sailing, don’t forget that the worst kind place for weight is aloft. Without the keel, you significantly reduce the stability of the boat by having a furled Code 0 (for example) hanging around up the rig. It’s inconvenient to drop it every time, but it’s worth it.

Higher speeds, bigger loads, a lighter boat and higher centre of gravity don’t sound like the safest characteristics, and they aren’t if poorly managed. But you can also use them to your advantage. Being able to sail faster means you sometimes have an option to run away from bad weather.

But there are other safety drills that are worth thinking about ahead of time. What is your MOB recovery plan? With cats’ high freeboard, some owners plan to reverse up to the casualty and pick them up from the steps at the back. But how many have practiced that? Will it involve dropping the mainsail? Could the props injure the casualty? How does the back of the boat behave in a significant sea state? I’d recommend practising this until you have a plan that works for you on your boat with the equipment you have. The same should be said for plans to evacuate the boat, or deal with a fire on board.

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The Planing Power Catamaran: A Different Kind Of Cat

Planing powercats deliver the high speeds dayboaters and weekend anglers crave — but without so much pounding in choppy seas.

Rear view of a dual hull catamaran with two 200 horsepower outboard engines, a bimini top with fishing rods attched to it moored in turquoise blue water

The air cushion created between the two hulls dramatically reduces wave impact at running speeds. (Photo: World Cat)

Powercats are different beasts than sailing cats, and the powercats you're most likely to see on your local waters are those in the 20- to 40-foot range (like my 22-foot Glacier Bay). Unlike the big cruising powercats, which are more like cat trawlers with top ends maybe a little over 20 mph, smaller cats have planing hulls that perform much like today's modern powerboats.

Depending on the engine package, there are a few cats that top out in the lower 30s, lots in the lower 40s, some in the 50s, and a few that break 70 or even 80 mph.

While a similar length monohull may have a 40-mph cruising speed in a 2-foot chop, the monohull captain will pull back the throttles and cruise at 30 to avoid being beaten up. The cat guy, on the other hand, may be able to keep on doing 40 thanks to the smoother ride. But having two hulls underfoot does create some interesting similarities in how these different types of boats react to input from the helm. So you'll see a few of the tips here mirror those used for sailing or cruising catamarans. Whatever type of cat you may be captaining, remember the following:

Center the wheel and use only the throttles to control the boat. Powercats have their engines exceptionally widely spaced apart, and are far more responsive than monohulls when steered via throttles. Generally speaking, turning the steering wheel will only serve to reduce the effectiveness of working the throttles. This, of course, is assuming you have two engines. There are a few rare cats with one engine.
At identical rpm, the engine in forward will create more thrust than the engine in reverse. So even if the throttles are set evenly when opposed, the boat will likely slide forward a bit as opposed to spinning in its own length. As a result, when attempting to speed up the maneuver it's usually best to favor giving the reversed engine extra oomph as opposed to the one in forward (assuming you don't want to move forward while turning the boat).
Check the speed and direction of the wind before docking , and remember that some cats, particularly those with low draft, can be blown around more easily than many monohulls as there may be less hull below the waterline.
When docking in a new slip for the first time with lines that haven't been preset, bear in mind that once you're docked, securing the boat can be difficult in some situations because few powercats have centered cleats. Most will have a single cleat on either side, in some cases obstructed by a bow rail and/or pulpit, which can make crossing lines difficult.
Never shut those engines down until all the lines are secured . Again, remember that many cats can get blown out of kilter faster than the average monohull, and if you don't have lines preset, it may take a moment to figure out how to best secure them. Many a captain has done a perfect docking job and then shut off the engines, only for a gust of wind to push the boat right back out of the slip before the lines can be tied. Keep those engines running until the boat is 100% secure so you can apply power, if necessary, to maintain position.

Why Two Hulls?

Like all boats, catamarans come with distinct advantages (smooth ride, draft), and areas of compromise (docking, turning). Regardless of design aesthetics, the first question is usually: Why two hulls?

Mike Myers, vice president of product development for World Cat explains: "Catamaran hulls experience little to no drag or resistance to get on plane, resulting in greater fuel economy. They have a steady rise in speed and fuel burn with little to no spikes in fuel consumption."Planing powercats have a unique trait — which many cat lovers consider the top advantage over monohulls — the impact-absorbing cushion of air created by a compression tunnel between hulls.

And when it comes to beam, catamarans' parallel hulls create reliable stability, which helps to avoid heeling and capsizing, and greatly reduces the vessel roll at rest and at trolling speeds.

"Many boats are primarily designed around comfort for the captain. This usually means anyone at the front or sides of the boat takes most of the jostling,"Myers says. "The catamaran-style hull delivers ride comfort, smoothness, load distribution, and stability."That stability draws anglers to powercats of typically 20 to 40 feet; and cruisers to sailing cats 40 to 60 feet and beyond.

— Rich Armstrong

Taming The Cat

When it comes to handling powercats in open waters, the most important thing to remember is that all boats are different. Just as you wouldn't lump the handling characteristics of all monohulls together, the same goes for powercats. But many have a few common traits to consider.

Some powercats have relatively low buoyancy in the bow compared to monohulls, as many have very narrow hull entries . As a result, in some cases, idling into a sea can allow waves to break over the bow. Gaining some headway so the bow rises a bit and packs air into the tunnel can alleviate the issue.
Some planing powercats will run smoother at faster speeds than slower speeds, as they compress air in the tunnel between the two hulls. In these cases, speeding up may actually provide a more comfortable ride in some sea states as compared to slowing down. Depending on your boat, its tunnel may result in other differences from the monohull that you may be familiar with. Learning about these will improve you experience.
Some powercats display a "snap roll,"which is a very fast righting motion that can rock the boat uncomfortably, especially when drifting in a beam sea. In these cases, people who may want to drift often (such as anglers) will sometimes deploy a drift sock off the bow to reduce rocking and rolling.

Man wearing a white long-sleeve t-shirt fishing off the bow of a power catamaran as it cruises through the water

Photo: World Cat

In general, powercats are often more weight-sensitive than monohulls, especially when the bow is loaded down . It's always best to be aware of how you're loading your boat, and if the tunnel is slapping or the bow is digging into waves, consider shifting weight aft.
Some powercats, particularly older models, lean out in a turn rather than banking in. There's no way to eliminate this phenomenon (although trimming up an outboard engine when initiating a turn may reduce it a bit), so it's important to give passengers a warning to hold on before making any aggressive maneuvers.
"Sneezing,"or blowing a puff of mist out the front of the tunnel that the boat then runs through (getting everyone aboard damp), is a phenomenon associated with some powercats. In many cases, trimming the bow up a bit will significantly reduce or even eliminate sneezing.

The truth about ceramic coatings for boats.

Our editor investigates the marketing claims of consumer-grade ceramic coatings.

Fine-Tune Your Side Scan Fishfinder

Take your side-scanning fishfinder off auto mode, and you’ll be spotting your prey from afar in no time

DIY Boat Foam Decking

Closed-cell foam flooring helps make boating more comfortable. Here’s how to install it on your vessel

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Top tech writer and accomplished sports fisherman, BoatUS Magazine Contributing Editor Lenny Rudow has written seven practical boating books, won 30 awards from Boating Writers International — many for his marine electronics articles – and two for excellence from the Outdoor Writers Association of America. He judges the NMMA Innovation Awards, and is Angler in Chief at FishTalk, his own Chesapeake-based publication. A great teacher and inspirational writer, Lenny hosts many of BoatUS Magazine’s very-popular how-to videos, which can be found on the BoatUS YouTube channel, or at BoatUS.com

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Croatia: Walking & Island-Hopping Along the Dalmatian Coast

9 days, dubrovnik to trogir.

Full itinerary
Tour details

Croatia’s stunning coastline calls on this nine-day adventure through historic towns and dazzling Adriatic islands. Explore Dubrovnik from every angle — on foot, by kayak, and from a cable car ride to the mountain's peak. Hop on hydrofoils and high-speed catamarans to discover the islands of Korčula and Hvar, then sail by private boat to the Pakleni Islands for a day of walking, swimming, and sun-soaked bliss. Wander Split’s old town and hike to the breathtaking Krka Waterfalls. With a perfect blend of action, culture, and mouthwatering food, Croatia will capture your heart and leave you craving more.

Dubrovnik to Trogir

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Quality accommodations and more inclusions than on other G Adventures tours, like meals, private transport, and activities.

Physical Rating: 3 - Average

Some tours may include light hiking, biking, rafting, or kayaking in addition to walking.

Trip Type: Small Group

Small group experience; Max 16, avg 12

Age requirement: 18+

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Trees planted for this trip: 9

Map of the route for Croatia: Walking & Island-Hopping Along the Dalmatian Coast

Places visited

Day 1 dubrovnik: a gem of the adriatic.

Take in the long stretch of the Adriatic coastline as your plane makes it's descent As the high stone walls and medieval buildings come into view, imagine life here thousands of years ago and perhaps even the occasional dragon beating its wings in the distance. We welcome you to Dubrovnik and to Croatia, and we invite you to unleash your sense of adventure and imagination as you discover the best of the country's coast and islands.

Exclusive Inclusions:

Meals included:, day 2 dubrovnik: from below and above.

Often the best views of the city are actually from outside of it. Put that theory to the test as you paddle a kayak along the historic city walls, exploring hidden caves and stopping to swim and snorkel. Back on dry land, you'll swap the views from the water for views from above as you ride a cable car up nearby Mount Srđ for breathtaking vistas of Dubrovnik and the surrounding islands.

Day 3 Korčula: Along the Dalmatian Coast

Dubrovnik begs to be further explored and you'll have some extra time to do so today on your own. Soak in every last bit of the city's beauty before taking to the sea and heading up the Dalmatian Coast to the island of Korčula for your first taste of life on the Croatian isles.

Day 4 Korčula: Your OMG Day

Discover Korčula today on your own terms. Choose between 2 activities which will get you outdoors and active as well as sampling some of the regions delicacies. Whichever you choose, your body,, mind and stomach will be forever grateful.

Day 5 Hvar: Island Life

The Dalmatian Islands are nothing short of spectacular and each one is quite unique with its own feel. Swap Korčula Island for Hvar and see for yourself, exploring the town of Hvar as well as taking in the island's gorgeous beaches and lively nightlife.

Day 6 Hvar: A Day on the Water

Feel the wind on your face and taste the sea in the air as you head out from Hvar to explore some of the nearby islands. You'll spend the day in and out of the water, exploring hidden coves, swimming from the boat and hiking to a secluded beach. If you. could imagine a perfect day actively exploring and island-hopping in the sun and sand, this would be it.

Day 7 Trogir: Explore Split

Back on the mainland, the city of Split is the largest along Croatia's coast, where you'll be immersed in its history and beautiful architecture in the old part of the city. An important maritime transport hub in the region, Split occupies a strategic position on a peninsula that juts out into the Adriatic Sea, and has been inhabited for over 2000 years.

Day 8 Trogir: Krka Waterfalls and National Park

Immerse yourself in Croatia's natural beauty on a hike through a lush forest, following a river until the sight of a breathtaking waterfall comes into view. Enjoy the moment and the sound of the cascading water before re-entering the forest and allowing the sound of the birds to take over. Back in urban civilization, take in more beautiful architecture and historical landmarks in Sibenik on the way back to Trogir.

Day 9 Trogir

The adventure finishes today, and you can depart at any time.

What's Included

Your Welcome Moment: Welcome Moment - Meet Your CEO and Group
Your OMG Day: Korčula Biking or Hiking and Winery Visit, Korčula
Complimentary arrival transfer
Evening guided walking tour of Dubrovnik's old town
Welcome dinner
Kayaking excursion along Dubrovnik's old city walls
Cable car ride up Mount Srd
Orientation walk of Korčula
Guided walking tour of Hvar town
Full-day excursion by private boat to the Pakleni Islands
Guided Walking tour of the Old Town of Split
Orientation walk in Trogir
Hike in Krka National Park to the Skradinski Buk Waterfall
Guided Walking tour of Sibenik
Farewell Dinner
Transport to/from all included activities and between all destinations

Accommodations

Hotels (8 nts).

8 breakfasts, 3 lunches, 5 dinners Allow USD250-325 for meals not included.

Transportation

Private vehicle, kayaking, cable car, hydrofoil, high-speed catamaran, private boat, walking,

Staff & experts

CEO (Chief Experience Officer) throughout, local guides.

Available extras (Add these to your tour when you book)

My own room - from $1899.00.

If you're travelling solo and would prefer to have your own private room throughout your trip, select this option during the online booking process.

Make it a private tour

Book this tour as a private departure, with your own CEO and all the benefits of a G Adventures group tour.

IMAGES

Planing hull catamaran for high speed operation in a seaway Patent
Catamaran Hull Speed Calculator For Beginners (Table and Free
Planing hull catamaran for high speed operation in a seaway Patent
Planing hull catamaran for high speed operation in a seaway Patent
Catamaran Hull Speed Calculator For Beginners (Table and Free
Optimising Hull Lines for Performance

VIDEO

Building a Catamaran ep.5 #25
Planing system in Lithuania
Planing system in Netherlands
Profab 1200
Planing line in Lithuania
Planing line in Latvia

COMMENTS

Catamaran Hull Speed Calculator For Beginners (Table and Free
Catamarans can be configured as planing hulls, although most sailing catamarans are set up as either semi-planing or hydrofoil. Due to the high speeds needed to get a boat to planing speed, this is only possible on racing sailboats or motor-powered catamarans such as high-speed ferries.
Experimental and statistical analysis of the ...
However, planing catamarans have been taking a bigger role in high-speed vessels for passenger transportation, leisure, or competition due to their high efficiency, roll stability at high speeds, and smoother rides in rough water conditions (Yun et al., 2018).
Catamaran Hull Design
If you have fine hulls you can use a lower Cp. Most monohulls have a Cp of 0.55- 0.57. And that is about right for displacement speeds. However the key to Catamaran design is you need a higher Cp if you want to sail fast. So a multihull should be at least 0.61 and a heavy displacement multihull a bit higher still.
Experimental and statistical analysis of the ...
Yun et al. (2018), in their complete review of high-speed catamarans, argued that asymmetric planing catamarans present higher resistance than monohulls at Froude numbers starting at 2, with catamarans having around 35% more resistance than monohulls. In contrast, the trim angle is slightly higher for the monohull between Froude numbers of 2 ...
Hydrodynamic analysis techniques for high-speed planing hulls
A planing hull is a marine vessel whose weight is mostly supported by hydrodynamic pressures at high-speed forward motion. Its high-speed character has made it popular and thus the interest for planing hulls for military, recreational and racing applications is progressively rising. The design and analysis procedure for high-speed planing hulls ...
PDF Graphs for Predicting the Ideal High-speed Resistance of Planing Catamarans
Figure 3(c) clearly shows that this operating condition necessarily falls in a region of very high resistance. Now consider the operating condition of the catamaran with the 2-ft wide pontoons at the same value of speed coefficient. The trim angle for this case will be 4.2°, and the value of aspect ratio will be 0.13.
High Speed Catamarans and Multihulls
Covers the full range of high speed catamarans and multihull vehicles; ... Previews experimental future vehicles including waterplane twin hull vessels, wave piercing catamarans, planing Catamarans, tunnel planing catamarans and other multihull vessels; 14k Accesses. 10 Citations. 3 Altmetric. Buy print copy ...
High Speed Catamarans and Multihulls: Technology ...
The combination of catamaran length and speed transfers the catamaran from the planing regime with dominant tangential stresses to a transitional speed between the displacement and planing regime ...
PDF Chapter 10 Other High-Speed Multihull Craft
10.3 Super Slender Twin-Hull Vessels. Displacement and semiplaning passenger ferry catamarans have been built for service speeds up to 40 knots with FrL below 0.75, though more commonly these craft have service speeds in a range of 25 to 35 knots due to the obstacle of wave-making resistance at high FrL.
Hydrodynamics of single-deadrise hulls and their catamaran
Abstract. Asymmetric planing hulls are often used on high-speed catamarans. In this study, a linearized potential-flow method is applied for modeling steady hydrodynamics of single asymmetric hulls and their catamaran setups. Numerical results are validated with available experimental data and empirical correlations.
Crouch's Calculator
Crouch's Calculator. The calculated value is indicated by the shaded heading in the table. This useful calculator computes an estimate of boat speed for a modern planing monohull using inputs of the power at the propeller shaft, the total boat weight, and a coefficient called the hull factor. The calculator can also compute any one parameter ...
Catamaran Design Formulas
While the length/beam ratio of catamaran, L BRC is between 2.2 and 3.2, a catamaran can be certified to A category if SF > 40 000 and to B category if SF > 15 000. Engine Power Requirements: P m = 4 x (m LDC /1025)P m = 28: The engine power needed for the catamaran is typically 4 kW/tonne and the motoring speed is near the hull speed.
Planing and the Need for Speed
A modern sailboard with a 6-8 m2 sail will plane when it reaches a speed of 12 knots. If the sail area is increased to 10-12 m2, the minimum planing speed is reduced to 8 knots. Wide boards plane at lower speeds; they do not reach the top speeds of narrow boards because of their greater drag. Boards with a tail rocker—an upward curve at the ...
Experimental and numerical investigation on the resistance
A 1:4 scale model of planing catamaran hull has been built and the geometry of the planing catamaran in this study is shown in Fig. 1.And the main parameters of this catamaran are presented in Table 1.The hull is divided into two demi-hulls arranged aside by a tunnel, so this kind of planing catamaran is also named tunneled planing hull (Roshan et al., 2020).
Other High-Speed Multihull Craft
The tunnel planing catamaran (TPC) is slightly different in that it has asymmetric demihulls formed by a reducing height tunnel along the longitudinal central plane from bow to stern so as to provide some additional aerodynamic and hydrodynamic lift (Fig. 10.1b).The top of the tunnel may be of a V configuration with a dead-rise angle of 10-15°, as in the figure, to reduce wave slamming and ...
Optimising Hull Lines for Performance
A third number that we can plug in as a constant if we want to is the prismatic coefficient which describes bow much volume there is end the ends relative to the cross section shape in the middle of the boat, but in sailing boats this is of less importance compared to other factors. The hull lines for Design 256, 8.5m Cat.
Resistance and Propulsion Characteristics of the VWS Hard Chine
decided the VWS Hard Chine Catamaran Series '89 would consist only of forms with symmetric sections, a transom wedge, and external spray rails. THE LAYOUT OF THE SERIES Basic Requirements The series was initially developed for high speed planing catamarans having waterline lengths of 25 to 35 m and carrying 150 to 200 passengers. However,
Stability Assessment of a Catamaran Using Sea Trials
The evolution of high-speed planing catamarans has developed vessels that can have as many as four 400 kW outboards, with many vessels achieving a Froude number higher than 2 [1,5,6,7,8]. While powered catamarans have several advantages, efficient hull form, stability at rest and an increased deck size for any given length, they are prone to ...
Catamaran sailing: expert multihull techniques
Speed. Most non-planing monohulls will do approximately the same speed on all points of sail. However, a performance multihull might sail at twice, three, even four times its upwind speed on a ...
The Planing Power Catamaran: A Different Kind Of Cat
Mike Myers, vice president of product development for World Cat explains: "Catamaran hulls experience little to no drag or resistance to get on plane, resulting in greater fuel economy. They have a steady rise in speed and fuel burn with little to no spikes in fuel consumption."Planing powercats have a unique trait — which many cat lovers ...
PDF Numerical calculation of the resistance of catamarans at different
Comparing the total resistance curves of ships under different k/b, when Fr =0.2, k/b =3.5, there is a significant reduction in the wave-making interference of the catamaran; And when Fr is between 0.4 and 0.8; When k/b =2.5, there will be a significant decrease; when Fr =1.1, it will gradually decrease when k/b =3.
Hellkats Planning To Unveil First 32-Foot Catamaran Under New Ownership
Its assets included tooling for 30- and 32-foot high-performance catamarans, as well as tooling for a 40-foot catamaran-hull-based center console to be offered in angling-specific and poker-run versions. The new owners of Hellkats Powerboats are excited to showcase their 32-foot cat in Fort Lauderdale next month. Photos courtesy Hellkats Powerboats
Hydrodynamic modeling of planing catamarans with symmetric hulls
Over the last several decades planing catamarans have gained popularity for commercial, recreational and military purposes, yet there is a relatively limited body of literature on the subject of planing multi-hulls. ... CFD validation studies for a high-speed foil-assisted semi-planing catamaran. J. Mar. Sci. Technol., 16 (2) (2011), pp. 157 ...
Experimental and numerical investigation on the resistance
The high-speed planing catamaran is a newly developed tunnel-type planing craft, which is also named tunneled planing hull (Roshan et al., 2020). The air flow enters into the tunnel and generates the aerodynamic force over the hull during high-speed regions. The planing catamaran has similar resistance performance with the planing trimaran, the ...
Croatia: Walking & Island-Hopping Along the Dalmatian Coast
Croatia's stunning coastline calls on this nine-day adventure through historic towns and dazzling Adriatic islands. Explore Dubrovnik from every angle — on foot, by kayak, and from a cable car ride to the mountain's peak. Hop on hydrofoils and high-speed catamarans to discover the islands of Korčula and Hvar, then sail by private boat to the Pakleni Islands for a day of walking, swimming ...