bcarpman

Anyone know any good references for learning about the various factors that go into the design of a go fast hull?

I've read Sorensen's guide to powerboats and searched this forum and the internet, but I'm still confused by many issues.

I picked up an issue of Speedboat magazine the other day and every review starts out with "....first step x feet back, 1 inch deep...notched transom....unique pad design x feet long...blah, blah, blah" They make it sound like it's all understandable if you just understood hull design. I'd like to think it's not just black magic, and that there's actually some theory to it all, but I just can't find it.

What makes one hull faster than another? What makes one handle more predictably? Why do some standard V's run just as fast as stepped hulls? What does a notched transom do? etc. etc. etc.

Anyone have any references to material, either technical or not that might help me?

Thanks

TopSpin80

excellent thread.....

to make a hull go faster split the V in half and put a wing between the two halves

actually I am interested in hull design also
www.boatdesign.net
has some stuff, but mostly non-planing hulls

Ernie

bcarpman

Funny!

Actually, that's the problem I keep running into. Everything out there is for slower boats, sail boats, non-planing hulls, etc. Nothing to help us understand the kinds of boats we're interested in.

bcarpman

Yeah, that's what I was wondering. Is it all black magic? Is this guy in the magazine just full of it, trying to interpret what the designer was after by looking at it?

stevesxm

i agree. all those guys with advanced degrees in computational fluid dynamics spending thousands of hours doing pressure gradient studies at speed, tank testing and then a few hundred more hours doing FEA on the results must just all be guessing... you know... sit around under that ol tree and whittle out a shape and say " hey lets spend , oh, about 500 grand to make some molds and the first piece and see ifthis is any good or not......


geeeeeze.....

yup all trial and error and black magic FOR SURE.....

ever wonder why some guys win every race they enter and other always have " bad luck " ? its thinking like this that's the reason

bcarpman

Then how come no one on this forum can even point me to a source of research!!!! If there were a lot of people doing the work then it would actually be out there. Where is it! I'm guessing you obviously know, but just don't think it's worth your time to fill us in??

When someone in any other industry does research, it actually eventually get published somewhere. Maybe not the state of the art, super secret stuff, but at least the basics.

TopSpin80

look up ANSYS and Fluent FEA... there are even FEA analysis' that show the flow rate/patterns of epoxy in a resing infusion.... I think the problem is there really is no way to completely and accurately do a planing hull... most is done for achieving laminar flow on a displacement hull such as a sailboat... what you are asking for is a combination of mostly airflow (aeronautics) and some hydrodynamics.

I think Steve Koss is a guy you might want to write, he may know of a source for information.. his screen name was steve1 but I haven't seen it online in a while

Ernie

bcarpman

Thanks. I've long studied FEA for other uses, and am very aware of it's abilities and limitations (at least as of 5 years ago). I'm just trying to figure out what "engineering method" is being utilized here:

Yes, there's usually three ways things are done in the engineering world.

1. Complete computer predictions using actual accurate computer models. This can be done in SOME cases, but only if the theory is completely understood AND the input is good (hence "garbage in, garbage out). You'll often find the guys
in the laboratories griping over crappy computer models and all the work they have to do to actually "make it work" in the real world after the computer guys provided them with something unworkable. This was the state of IC engine design in the 80's and early 90's. It's much better now, and the computer guys work very closely with the lab rats.

2. SWAG: Scientific Wild Ass Guess - This is when you've got at least a partial understanding of what's going on so at least you continually know which direction to move in each iteration. Most of what you do is predictable, but often not the magnitude. Sometimes something surprises you, but when it does you take a step back and figure out why so that it doesn't happen again.

3. WAG: Wild Ass Guess - "We do it this way because it's the way we've always done it" or "It looked cool so we put it in and ran it. Doesn't seen to hurt anything". Most (but not all) "engineering" in the hot rod parts industry is done this way. They keep doing something till they find something cooler looking to copy.

I'm hoping bottom design at least falls into category number 2. From my experience with FEA I highly doubt they are to number 1 yet, but you never know. I'd at least be happy to see a book, article, white paper, or whatever that talks about the basic assumptions that go into high performance hull design.

vtec

Principles of Yacht Design (Larsson and Eliasson). Has one chapter related to planning hulls.

Donald Blount (nav. arch.) has been published in Professional Boatbuilder. The one article I remember mentions the amount of rocker necessary as speed changes in the hull, also had some interesting hydro/water pressure research results as well, such as the nose of the boat may cause downward suction when immeresed.

Blount is also published by SNAME I believe.SNAME may have other articles of interest


Naval architecture of planing hulls by Lindsay Lord (Unknown Binding - 1954) $194 on amazon. (I haven't read this one).

High Speed Small Craft by Peter Du Cane (Hardcover - April 1974) $214 on amazon (I haven't read this one either).

Hydrodynamics of High-Speed Marine Vehicles -Odd M. Faltinsen


Patents can also be a good source of info. The Hustler Hull patent comes to mind. It mentions CG related to the steps.

Harry Schoell patents are usefull as well(delta conic hull design, and duo-delta conic hull. This guy has done a ton of empiral research as well.

vtec

Design of High Speed Boats: Planing by P. R. Payne (Hardcover - Jun 1988) (I haven't read this) and unavailable