Hull Design for layman/non-engineers

[rdeputy]

I work in the boatbuilding industry and am trying to teach myself Rhino/AutoCAD for marine design. As many of you are aware, the average boatbuilder is neither an engineer nor is he an architect. I have some experience with each program and have gone through the basic lessons of learning to draw lines, curves, points, etc. However, I have little expertise in the actual design of hulls. I've read plenty of textbooks that discusses many of the topics of marine design however, I find myself still having questions.

As I began working on the basic lines I began asking myself how I am supposed to design the running surfaces, chine (reverse or other), number of strakes, and the widths and lengths of each. How do I determine what the chine beam is? None of the textbooks that I've found explains this in simple terms. I'm not an engineer so the detailed algebra and calculus won't help me.

I'm interested in designing a 32' LOA Center Console with Twin/Triple Outboard power with plenty of flare. My basic specs would be a 21-deg transom deadrise, ~60-deg entry deadrise; 2.75 length:beam ratio; 11.6' beam. This process is a learning exercise to test my cad skills and expand my working knowledge of running surfaces. Can anyone provide some insights? During my tenure at my companies, I've consulted with a veteran designer in the industry with more experience then anyone could hope to glean. He has provided some of his tricks and I've watched him work. However, he oftentimes has difficulty communicating with me due to the large generation gap (drafting boards vs. computers).

Also, I've already enrolled in the online training class "Rhino for Marine Design" offered by the IBEX folks. I got kicked out for inability to keep up with the self-paced course. Hmmph, that has to be a first.

RD

[Cian Groves]

Hi RD,
there is a marine tutorial cd done by Cliff over on the Rhino website which would probable be of help in the modelling using Rhino.

Might be of help.

Cheers,
Cian

[stewi]

Both ACAD and Rhino are quite frustrating for beginners. I'm an engineer and learned ACAD just with books and on-line tutorial. Getting from 2 D to 3 D is a leap step even for engineers.
Rhino starts were ACAD is a bit weak, which is in its rendering capabilities as well as creating solid models. Besides that, once you get used to ACAD, you almost start from scratch when you switch to another software. Just the way you select drawing tools and draw a simple line is unique in ACAD and different in other drawing software.
I highly recommend to start with something more simple like this free hull design software: http://www.carlsondesign.com/#Fun_Shareware

[jehardiman]

Originally Posted by rdeputy

As I began working on the basic lines I began asking myself how I am supposed to design the running surfaces, chine (reverse or other), number of strakes, and the widths and lengths of each. How do I determine what the chine beam is? None of the textbooks that I've found explains this in simple terms. I'm not an engineer so the detailed algebra and calculus won't help me.

This is an area where everyone fears to tread. The real answer is to copy what works and have very deep pockets so you can do several hulls until you get it right. While there are several theories out there how to do this, including several standard series, mostly such hulls are evolutionary rather than from scratch. The big companies keep most of thier test data close to their chests because there is a lot of money riding on each new hull mold. Also there is no "magic" configuration, it all depends on other hull prameters like weight, CG, running angle, etc. and the proposed operational environment; i.e. some hulls that do well in flat water are unsuitable for chop, etc. I'd start with parmeters from within the range of one of the standard series and then hedge my bet using expanded theory.

[CMillican]

I'm afraid hull design is a bit of an art. The one tip I would give is, check the weight against the displacement. When you've checked it, check it again, and again. There is almost no bigger fault in any hull than to float too high or too low in the water as it can increase resistance and ruin stability. The other aspects you have mentioned are also important - like jehardiman says, find out what has worked before and try and search out formulae and rules of thumb, as they do exist. But triple-check the weight!

[water addict]

Originally Posted by rdeputy

........
I'm interested in designing a 32' LOA Center Console with Twin/Triple Outboard power with plenty of flare. My basic specs would be a 21-deg transom deadrise, ~60-deg entry deadrise; 2.75 length:beam ratio; 11.6' beam. This process is a learning exercise to test my cad skills and expand my working knowledge of running surfaces. Can anyone provide some insights? ......
RD

If you are looking at good planing hull shapes, the best place to start is the series 62 planing form developed at David Taylor Model Basin in the 60s. Sources: Clement and Blount "Resistance Tests of a Systematic Series of Planing Hull Forms", SNAME Transactions, Vol. 71. This gives the lines. Planing hulls have been tweaked here and there since then, but this is a real good shape to start with.

[Robjl]

Rdeputy,
I found this to be a good article when I first started with a yacht design program,
http://www.newavesys.com/spiral.htm

[Caldera Boats]

check out FREEship.
www.freeship.org