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Old 09-09-2003, 01:58 PM
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Callan did some wind testing in Marathon too. I was talking about manufacturs not race teams I would believe that Victory team has they've spent more money racing than anyone. I can't imagine wind test a 30 foot baja? for what how fast is it possibly going to go? Yes I was talking about Yellowfin no drawings no computers....good running boat. How much does a wind tunnel cost anyway per hour, I think it's easier for some builders to mock up parts and test in the real world.
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Old 09-09-2003, 02:20 PM
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Default Re: Let me be a bit naive....

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Aren't all these designs able to be modeled and tested "in theory" electronically before they are built, which results in these radical designs? There is no way that a couple guys sit around, drink a few beers, and say "hey bob, why don't we throw a step here and a whooziwhatit there and build a severaly hundred thousand dollar boat"? Right??? Just curious. Again, my background is in aviation and there are certainly common aircraft out there with some funky looking packages that certainly upgrade the aerodynamics for greater speed, range, economy, etc. - that all work well and...were all computer designed. I guess one of the biggest factors that makes me ask this is the way old molds are so valuable and continue to pass from hand to hand. I mean, honestly, as great (and classic) as say, a 41 Apache mold is - why wouldn't someone just start from scratch rather than buy an old mold???
First, the biggest problem with computerized hydrodynamics and such is that modeling a planing hull is very challenging. I'm sure it's been done, but I doubt it's widely available. I have two good friends who worked on Oracle's America's Cup team ... they both have graduate degrees from MIT (undergrads from Webb, I went to school with them) ... they had a team of 20 engineers with similar backgrounds working for them and a huge budget. Most powerboat builders do not have that kind of budget, and even the few that do wouldn't spend that kind of money for an extra MPH or two probably. Even then though in the case of Oracle, they still do tank testing and don't trust the results of computer runs. The computer runs will tell you your best bets, but they're still not accurate enough to say for sure one design is better than another.

I actually did my thesis at Webb on step designs (don't ask me about it, I don't remember too much anymore ... too much drinking at powerboat races has killed off all those brain cells), but another problem with testing step designs is they don't scale very well. For instance, if you have very small steps in a boat, you can't scale them down accurately because they become too small and won't scale back up correctly. In the model we built for our thesis to test step configurations we had a huge step relatively speaking to try and avoid the scaling problems to some extent. Because we were only comparing different step configurations relative to each other, that wasn't a big problem.
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Old 09-09-2003, 02:37 PM
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Food for thought:

Okay, so the general consensus, seems to be that most powerboat mfg's cannot, for one reason or another(probably cost and time) perform lengthy analysis on their boats. Does this translate into structure as well.

I would hope, that in the least, some engineering is performed in the creation of these boats; Cad models, Finite element modeling, structural substantiation, running load cases, classical laminate theory, matrix analysis...Yes?/No? This is a minimum.

Who decides on lay-up, material, fiber orientation, resin system, woven/knit/tow, heat range, bag pressure, cure cycle, coring, compression strength, peel strength, ultimate tensile strength, buckling resistance, crippling resistance? Are these factors or wishful thinking?

Is it Marketing, the Builder, or the Engineer? (Or trial and error?)

...Questions I would love answered from some of the more popular builders.
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Old 09-09-2003, 02:55 PM
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Originally posted by Baja Daze
I would hope, that in the least, some engineering is performed in the creation of these boats; Cad models, Finite element modeling, structural substantiation, running load cases, classical laminate theory, matrix analysis...Yes?/No? This is a minimum.
The American Bureau of Shipping and other classification societies publish rules for shipbuilding, which includes rules for fiberglass boats. These rules set out minimum standards for the structural cross-section, spacing of members, and other design decisions for fiberglass boats. These calculations are relatively simplistic compared to what can be done using computers for a specific design, i.e., finite element analysis. I performed such calculations in my first job out of college for a high-speed "thrill-ride" type speedboat my company was working on, they're not exactly rocket science if they had a first-year engineer like me doing them.

While it's not necessarilly required for personal powerboats to be designed to such standards (commercial craft are because they have to be), I'd be willing to bet most larger manufacturers (Baja, Donzi, Scarab, etc.) do design their craft to such standards for insurance purposes, in other words, their insurance companies want to be able to fall back on those known design rules in the case of litigation.

That's not to say Finite Element Analysis can not be used, an in fact it is used on larger vessels instead of the rules these days, but again, many manufacturers probably do not because of cost.

Stuff like laminate theory and coring and bag pressure are not really dealt with in terms of ship design. That's a material design consideration and would be done by someone else. Basically the guy designing the boat knows the material will have certain characteristics and it's someone else's job to know what needs to be done to make material with those characteristics.
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Old 09-09-2003, 03:15 PM
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Thanks for the response, Beckles. That kind of confirmed my thoughts. It just seems to me that in the arena with which we, as performance boaters, are accustomed to some of the more stringent analysis is overlooked. Or maybe not, we just never hear about it.

Then there are those who fall back on the old adage, "This is just the way we've always done it."

Sounds like you may be a Naval Architect or engineer. Ship design is a fascinating science. I wonder how much of it translates into our market.

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Old 09-09-2003, 03:18 PM
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Quote:
Originally posted by Beckles
...Stuff like laminate theory and coring and bag pressure are not really dealt with in terms of ship design. That's a material design consideration and would be done by someone else. Basically the guy designing the boat knows the material will have certain characteristics and it's someone else's job to know what needs to be done to make material with those characteristics.
Very true. But for optimal, concurrent design and maximum efficient weight management, the materials must be carefully and deliberately chosen and oriented. The properties can change drastically with minor modifications to ply laminate schedule. It's best when M&P and design get along well.
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Old 09-09-2003, 03:24 PM
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Originally posted by Baja Daze
Thanks for the response, Beckles. That kind of confirmed my thoughts. It just seems to me that in the arena with which we, as performance boaters, are accustomed to some of the more stringent analysis is overlooked. Maybe it not, we just never hear about it.
It's a cost versus benefit issue. I'm sure some of the large companies have done some basic analyses in terms of hydrodynamics and structure. I'm sure some of them have even model-tested their mass-produced hull forms (where you can spread the cost over enough hulls to make it cost effective). The problem is that even when you do that, the benefit just isn't there in terms of performance ... as Ryan already pointed out, sometimes guys just know. From everything I've heard, the Yellowfin will out-perform any Boston Whaler, Fountain, Mako, Scarab, or other center console, one of which I bet has used some of the fancy tools or model-testing to one extent or another. The guy who designed it used no such tools and is not a naval architect, the design is based on his knowledge from years of boating and experience (though his Dad happens to be a Webb alumn!).

Quote:
Sounds like you may be a Naval Architect or engineer. Ship design is a fascinating science. I wonder how much of it translates into our market.
I didn't come right out and say it, but as I alluded to above, I went to Webb Institute, their only program is Naval Architecture and Marine Engineering. There are certainly plenty of naval architects out there designing powerboats, most of them just aren't using many of the tools they could be for various reasons (cost, cost, and cost).

Note, I myself have been out of the boat and ship design business for seven years, but things don't change that fast in the industry and I have classmates who are still in it of course that I talk to.
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Old 09-09-2003, 03:32 PM
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"Is it Marketing, the Builder, or the Engineer? (Or trial and error?) "
Nick in our small industry I would say a majority of it is Trail and Error. I have seen MANY performanc boats FALL APART that were built with the "LATEST and GREATEST" and I am not alking about small time race teams or builders. I've seen a few huge teams bring "NEW" boats to races and they fall apart. As corny as it sounds racing is the BEST proving ground in our industry. Just a few years ago a VERY well know company had to replace a race boat , becuase the composite company had convincedthem to build the race boat out of there "NEW BEST STUFF" well it fell apart.
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Old 09-09-2003, 03:37 PM
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Quote:
Originally posted by Baja Daze
Very true. But for optimal, concurrent design and maximum efficient weight management, the materials must be carefully and deliberately chosen and oriented. The properties can change drastically with minor modifications to ply laminate schedule. It's best when M&P and design get along well.
It's correct that the naval architect must choose his materials, but the properties (strength and how to construct it correctly) of his materials are basically a given, and someone else is doing the engineering (probably in a materials company somewhere, I doubt any powerboat company is doing this work themselves) to assure those properties are present in the materials when they are actually built. There's really not much reason these guys need to be working "hand-in-hand" on a powerboat.

Certainly there's innovation in materials, but that comes from the materials companies, and then they tell the powerboat companies "hey, we've got this new stuff, it's 20% stronger and 25% lighter, here's the specs." ... fact of the matter is most powerboat companies probably wouldn't use it anyway unless it cost the same or less. It's not like the powerboat makers are calling up the materials companies and saying "We need some stuff that's stronger and lighter, we'll pay for you to develop it and pay more for it." ... after all, such materials already exist (kevlar and carbon fiber) but are usually too expensive already.
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Old 09-09-2003, 03:47 PM
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Ryan, thanks bud. That's what I was thinking, too. We've seen that scenario too many times.
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