Hmm. Wouter, what I THINK you`re saying is that if you widen a boat`s beam you put more load on the leeward hull in strong breeze, perhaps so much that the bouyancy of the leeward hull is not enough to support the additional load, so the whole hull starts to submerge, never mind the bow ?
So in order to take an existing design & widen the platform, first you would need to re-design the hulls to have more bouyancy in general, preferably with a healthy percentage of it up front, unless the hulls are very bouyant to start with. So in effect you start again, and design a complete new boat. There has to be a limit as to how much width you can put on an existing hull design. Making a Hobie 16 wider will only increase the distance you fly after that inevitable pitch-pole !

Steve

Bill

Did you ever try poling the jib, i.e. using a pole to move the jib in front of the bows? I mention this because in one way the Wave is like the 18 sq, it tends to pitchpole before it flips and this helps

I have been experimenting with Rick's super Wave concept and found if you pole the jib out, the lift from jib torques the bows up and stern down. This makes the Wave sail like a real boat rather than bobbing along like a fishing float.

It is amazing how much lift a jib produces. The little 15 ft2 Wave jib bent the original 8 ft x 1 1/4 in Al pole like it was a batten and a Tornado jib broke it, on lift alone.

The reaction of the boat is different, with a poled jib. Instead of the bows burying in a puff, they stay the same or lift a little.

The main problem is forestay sag. With the pole and the mast bending it is difficult to keep the forestay tight enough to work upwind. The new pole is carbon and a lot stiffer I will have to see how it works.

Steve, …Bill Robert’s had the foresight to address the pitch pole problem right from the outset with his Super Cat designs. They are extremely resistant to pitch poleing. They incorporate the very things you are proposing in your “new boat”.

If the basic platform is flawed (such as the Hobie 16’s, with it’s propensity to pitch pole) then that “flaw” has to be addressed before one can fully take advantage of these other performance enhancements. Widening a Hobie 16 might lead to a totally false conclusion concerning the benefit of increased beam…blaming it (increased beam) instead of the of the Hobie’s innate tendency to pitch pole.

Simon,

Bill answered in previous posts that he did some experimenting using two different hulls in a cat: a normal one and a planing one. He tacked to compare the relative performance in identical conditions.

Apparently there was about 5% gain downwind but the slaming and pounding upwind was terrible.

One solution seems to be a variable geometry hull, with flaps or something alike extending from a normal hull to provide a greater planing area.

Foils are another approach. The inclined foils in open 60s provide only limited lift, but the figures seem to be increasing lately. The Catri 27 foils lift up to 90% of its displacement to assist it in planing. The downside of foils is the poor light wind performance.

Cheers,

Hello 5.8 sailor,
Going from 8.5ft beam to 11ft beam is one big jump in hprsepower, like 29%. This also means the max loads in your boat are going up by 29%. As max righting moment goes up, so does sail force and sail cloth tension especially leech tension. Mast compression goes up. Main beam loads go up. Centerboard bending loads go up. Sheet loads go up. If all the forces acting on the boat didn't go up, then the boat wouldn't go any faster. There are no free lunches.
But, if you want to go faster, do it!
Bill

Wait a minute...I gotta admit, I got lost in all that parent child relationship stuff . It's an easy misconception that making the boat wider loads the leeward hull equally more but it just 'aint so. For the most part (there is a small exception when considering the foward drive of the sails on the bow) I believe the leeward hull's buoyancy is only supporting the weight of the boat and the sailors. The additional righting moment only induces less rotational moment around the leeward hull. The mast, rigging, beams, boards, rudders, etc....just about everything else on the boat DOES carry more loading as the stresses go up but this stress exists between the sail and it's contact points to the windward hull where all the extra righting moment is. The leeward hull is supporting the same weight - it just has more advantage because it's farther out.

Hold on. A wider beam lowers mast compression for the same sail driving force, because the shroud is anchored further out and therefore pulls less "down" for the same "across". Imagine an infinitely wide boat. The shroud would come at the mast horizontally, and there would be no mast compression. Beam windage would be a bitch though.Maybe you could go upwind at the speed of light though? Jake, you could then check your results for RTI before you left, and make your decision to go!

yeak, I stand corrected...but you lost me when you started talking about RTI results???

AHHH, but reread the following phrase again.

“PS. I put a SC20 together once that was 20ft wide and it sailed fine. To windward it was a rocket. Reaching don't trapeze. Downwind same as a normal SC20, watch the bows.”

Don't you notice that little "Reaching don't trapeze" thingy ?

Why is that bit included ? Why can't you trapeze on this course ?

And Steve; I wasn't saying that the total volume of the leeward hulls needs to increase; just that the longitudal pitching restance needs to be increased in order to make effective use of the extra width.

What have you won when you've replaced capsizing with pitchpoling ? Either way you can't transform the sailpower that you have into speed.

But by all means guys, if you believe that you can make boats indefinately faster by making them wider and that no other design aspect will limit you gains to something far less than expected then widen your boats.


Wouter

Hi David,
What you say is true, but that is not the object. The object is to INCREASE SAIL DRIVING FORCE. At the same sail driving force there is no increase in boat speed. Our basic objective is to increase sail driving force by increasing righting moment. This will make the boat go faster. The same sail driving force on a wider boat does nothing to make the boat go faster and it does reduce shroud tension and mast compression.
Bill

Understood, Bill. Just wanted to reiterate that beam and its associated wider shroud stance has that advantage of allowing further rig loadings with not immediately increasing mast buckling load. You can go faster for the same mast compression...

Wouter...the boat was 20'wide X 20' long...what in the world do you need to trap on a reach for? You already have plenty of righting moment...

Bob

Hello Luiz,
The planing hull bottom that I tried was one design, one effort. I do not think it was optimized. I was primarily concerned with getting the boat to plane at all. Therefore I used a planing surface that was probably larger than optimum and easy to build, flat. To plane at lower speeds requires a low planing surface loading, pounds of lift per square foot of planing surface area. The combination of 'flat bottom' and low planing surface loading led to a hull that pounded severely sailing upwind in chop. The pounding problem can be attenuated with a vee shaped hull and less planing surface area, higher planing surface loading. This would lead to a higher displacement speed before planing began. I guess my point is that this planing hull thing is a large study and development program on its own. If I were to put more effort into it, I would try a vee shaped hull with concave surfaces forming the vee, very much like the hull surface of a sea plane. To support two people with a light hull loading, vee shaped hull, might take a longer hull than we are used to seeing for a two person boat. If we can keep the hull narrow. I think the pounding thing can be brought under control.
Bill

>>Wouter...the boat was 20'wide X 20' long...what in the world do you need to trap on a reach for? You already have plenty of righting moment...


So you are actually saying here that a narrow craft with trapezes could be just as fast on this course as their is more righting force available than is needed ? Doesn't this in a way underline the notion that going wider beyond a certain width is useless ?

Now answer the following question ; what will happen if you did trapeze off that 20 ft wide beam in 20 knots of wind and a sailarea to match your width ?

Wouter


(I see only two possible outcomes ; you dive - pitchpole and get beaten by a Hobie 14 as no sailboats sails as slow as an upside down sail boat. OR you let out your traveller and mainsheet to depower you rig which means that you do not make full used of both the available sailarea and width. At 8 knots of wind the extra width is useless as every design is stabil enough.)

Think about it.

I think I have found a better analogy :

Picture two guys facing eachother pulling on a long piece of line. Put a load on the middle of the line pulling down. If the load is small enough than the two guys are both strong enough to lift the load by pulling on the line. Than there is a load where both guys can just pull hard enough to lift it. Lets now put an even heavier load on the line. Both can not pull hard enough. Can we lift the heavier load by replacing just one of the guys by a much stronger one ?

No substitude one guy for "maximum sailforce at which the boat capsizes" ; the other for "Maximum sailforce at which the boat dives" and the load for sailarea. See the system ?

Or here another one ; some people think you can drive harder through a bend when you increase the friction tires have an the road. Others know that at some point you will just flip the car or hit the ground with you foot rest. Either way your not making the bend anymore.


Wouter

Hello Bill,

I simply can't resist comparing your simple statement:


with that of another famous designer when he justifies the absence of foils in his (excelent) designs with one single bad experience a long time ago. It simply fails to recognize that one try is not enough - especially when you do not have access to the best research available.

In my opinion this says a lot about your own idoniety and credibility (but I don't mean he isn't - just that he adopted a more sales-oriented position in this case)

Today many multihulls are experimenting with flat bottoms, steps, foils, etc. The only place I saw a "V" bottom was in the preliminary drawings of a 60 ft cat for a French skipper (Kersauson?). It looked like the float of a hidroplane, exactly as you say.

I guess by now they should already be testing the concept in smaller scale. We will soon find out if it worked.

Thanks for your time,

Question,

How does a Catri 27R's speed

http://www.multicascos.com/ingles/catri_english.htm

compare to an approximate equal size Farrier/Corsair?

Hello Luiz,
I don't follow what what you are saying in your comments.
The thing that stopped me from further testing/developing of the planing beach cat was that I could see it was going to be a long road, possibly without success, and I have other interests to follow.
The real world situation is, at least where I sail, when there is enough wind to plane, the surface of the water has waves on it 2 to 3ft high. Go for a ride in a flat bottom power boat and drive it into these waves even on a slow plane and the ride is very jerky and unpleasant and would probably damage the rigging of a beach cat. Drive a Vee bottom power boat into these same waves and the ride is more tolerable but the vee bottom power boat requires more horsepower to go the same speed as the flat bottom boat on flat water. Here in South Florida when the water is flat, there is no wind. The flat water situation is useless to consider because there is not enough wind to get a boat up on a plane. I'm sure the reason the seaplane has a Vee bottom is because frequently they land and take off on choppy water, real water, and they don't want to pound the bottom out of the airplane. There are many many variables to optimize on a planing beach cat hull shape by itself and I don't have a few years to devote to that.
With my brief experience with planing beach cat hull shapes, I now think the answer is a long slender planing hull shape that does not even attempt to plane to windward but runs displacement mode. Then when the boat speed doubles while reaching and going downwind with a spinnaker, the hull will climb out on a plane and really go fast when it is going along the waves or downwind with the waves and crossing them slowly. I think a narrow Vee hull shape with hard chines and lifting strakes is the way to go.
Bill

Bill
Planing surfaces are of course most efficient as very wide and very short, for much the same reasons wings are. But even power boats have longer and stepped "pads" for more versatility. Foils look a lot more attractive when you bring in the pounding. Also, I spoke to a guy in SA who has an about 30 foot beachcat (Whiplash)I remember him saying something about planing upwind, but bow burying preventing downwind planing. Back to the foils or my personal favorite, Racking hulls, which bring the buoyancy forward when sailing off the wind.

Wouter,
Sailors on a racing beach cat have several things to control. They trim the sails with the sheets. They steer the boat with the helm. They trim the hull out fore and aft by moving their weight forward or aft along the hull and they move their weight athwartship to balance the angle of heel. Which ever team can do these tasks in the best concert usually has the best boat speed.
On the angle of heel point: It doesn't matter how wide the boat is, you always want to barely fly a hull. So if you are on a very wide boat you may not trapeze or you might ever have to sit in the middle of the trampoline to get the hull to fly. In the same wind conditions on a narrow boat the team might be trapezeing to acheive the same goal. The point is to get the most boat speed out of your boat you place your weight where ever you need to to acheive the optimum goal. It is possible to trapeze when you don't need to and that is slow on a wide boat or a narrow boat. It is also possible to overtrim the sails on both boats and that is slow also. The wide boat offers the option to go very fast when the wind blows hard and you can't do that on a narrow boat. I've been there and done that, Wouter.
Bill

Luiz...I dont understand either. It seems to me that it is for Bill to decide what he spends his time and energy researching and to abandon any line of investigation for whatever reason. It says nothing about his idonity (had to look that one up) or his credibility...Dan