Hull type performance questions.

Hey again everyone, I have a few performance questions for the forum gurus.

Which hull type is quicker "over-all" flat bottom? Rounded? V-shaped? What about these "semi planing" types I've been hearing about? Are there "hybrid" types? What advantages/disadvantages do each type offer? Is there a magic do "everything" type?

Thanks,

Wolf

 

you talking
sail boat??
power boat ??
inboard ??
outboard ??
How many motors ??
fishing ??
pleasure ??
cruising ??
fishing ??
go fast ??
How fast ??
lenght ??
Wood ??
fibreglass ??
aluminium ??
steel ??

 

Racing sailing trimarans of the 16' and 33' range. Plywood/fiberglass and foam/fiberglass.

 

Too broad a set of questions to answer quickly, can you refine the questions a bit?

 

In 16 to 33' sailing racing trimarans, what are the stability, performance and handling characteristics differences between a flat bottom design, a rounded bottom and V-Shaped at speeds ranging from 5knots to 20knots? What are the MAJOR advantages and disadvantages to each to each hull type? Is one design by far the "better" choice or does it really not matter all that much?

 

There are no "far better" choices, just some advantages and disadvantages to consider trading off with, in regard to sailing attributes and preformance envelop. In terms of racing, most every aspect is geared to get the best speed, assuming certain safety issues are addressed. Some choices can produce ridiculously fast, craft, that are also fragile and costly, while you can sacrifice some speed potential for a larger safety margin and more durability. It all depends on the way you prioritize your needs and assemble the SOR. If all out speed and preformance are desired, then you'll have a costly likely dainty, but fast vessel, built with exotic materials and clever engineering. If a preformance orientated craft is desired, but with some accommodation to other aspects of the SOR, you'll subtract from the speed and preformance potential for these elements.

Simply put, you establish an SOR and make design decisions around it, best fitting the goals set within. This simply means there's no "best" of anything, just various choices and compromises you have to sort through.

 

This is all very confusing XD

 

Step 1. Write a Statement of Requirement (SOR) for your vessel.
(You need to provide more than the speed range and possible hull shapes.)

Everything else will soon fall into place and make sense.

 

Well the 16 footer is a day sailor/racer and the the designer of the 33 (Crowther) calls it a "performance coastal cruiser". So i guess the questions would be for those two types.

 

Spiritwolf,

is that you want to know more about the performance trade off? compared with the various hull shapes. such as vee bottom, flat bottom and round bottom.

 

V-shape softer riding in rough seas but more wetted surface so light air penalty.
Flat bottom- some turbulence from chines, can be harder riding.
round bottom-least wetted surface for displacement, less hard riding than flat bottom.

And every variable in between to blur the differences. A planing or semiplaning hull would normally use the flat bottom or round bottom shape. For a comparison your Bucc main hull is slender to slice through the waves at speed but with enough round built in to add some carrying capacity . A round hull version might be slightly faster in the light stuff but I doubt you'd notice. My tri has a fuller round main hull for more capacity and to rise up on the water to semiplane. The forward sections rise up on the bow wave keeping the stern in the water. This reduces wetted surface but the boat has more of a speed transition barrier than a thin hull regardless of shape. So every thing is connected, length, width, shape....a wide V will plane if shallow enough as can be seen on chine powerboats etc.....

 

Exactly