Laminate plan composite powerboat

[Neptune010]

Hi guys,

I'm new to this forum and have a question.

Does anyone of you know a general laminate plan of a composite powerboat hull?

Specifications: +/- 28ft
Weight: +/- 1000kg
Power: outboard

Thanks in advance!

[PAR]

The laminate schedule for any boat, especially a composite build is application specific and must be engineered for the design in question. Welcome to the forum and what boat are you building?

[Eric Sponberg]

Neptune,

PAR is correct. There really is no such thing as a "general laminate plan." The laminate of any boat depends on its type, weight, speed, internal structure, equipment installed--many things.

It would help if you tell us what you want the information for? Do you want to build a boat, or do you need the information as a reference for designing a boat?

Eric

[Neptune010]

@ PAR & Eric,

Thanks for your reply!

I want to build a boat, but still have a lot to learn. It's about a catamaran powerboat, like a Skater 28'. (http://brucebullockmarine.com/skater..._outboard.html)

I have a single 300HP Yamaha outboard behind my rib now, but I'm looking for something unique. I have a big workshop near my house, therefore I planned to make an own design.
I have some knowledge in hydrodynamics and structural analysis, but not in composite structures. Hopefully you know more!

[Eric Sponberg]

Really high speed powerboats (anything over 60 mph, and your example from Bullock Marine is for 112-120 mph) have unique behavior which, if the boat is not designed just right, can be fatal. Slamming through waves, of course, is the most obvious one--the loads are huge. Another problem with any high-speed cat particularly is aerodynamics and the potential for the boat to literally fly off the water and flip over. The boat has to be shaped correctly all over, and the structures have to be very strong and stiff in order to withstand the loads. If you are designing this boat yourself, then you would be best served to consult with a naval architect who is familiar with high-speed craft to review your work. Subtle features, good or bad, can have huge consequences, as I said, some of them fatal.

Eric

[cthippo]

Originally Posted by Eric Sponberg

Another problem with any high-speed cat particularly is aerodynamics and the potential for the boat to literally fly off the water and flip over.

Vaguely related question, but why isn't that factored into safety systems for things like hydroplanes? Those big wings on the back should have enough aerodynamic authority to overcome the lifting tendency of the boat and so why couldn't you use a miniature gyroscope to detect the change in pitch and automatically compensate?

[Eric Sponberg]

Originally Posted by cthippo

Vaguely related question, but why isn't that factored into safety systems for things like hydroplanes? Those big wings on the back should have enough aerodynamic authority to overcome the lifting tendency of the boat and so why couldn't you use a miniature gyroscope to detect the change in pitch and automatically compensate?

Obviously, some of them don't have enough authority: http://www.youtube.com/watch?v=DVsng...1&feature=fvwp

I don't know if offshore catamaran or hydroplane powerboats have gyroscopes or not. Even if you had a small one that could operate a computer sensing system that operated a spoiler as positioned at the rear as on the unlimited hydroplanes, would the spoiler change angle of attack fast enough and generate enough load to counteract the upward pitch of the bow??? I doubt it, but I am open to be convinced otherwise.

Since in the video the bow is lifting considerably and fast, that means that the center of lift for the hull is well forward of the center of gravity of the boat. It rotates up pretty quickly. So even if you had a spoiler well forward in the bow, would it work well enough to keep the bow down close to the water? I don't know. Maybe someone should try that.

Eric

[HakimKlunker]

You maybe think of a one-for-all solution?
Size, weight, speed etc influence pressures while operating (and of course, while not operating...)
So you will need to 'input' your individual data, to come to a (here) laminate 'output'.
You have several choices after you supplied yourself with the relevant formulas (most of the time - purchased):
Consider, that a theoretic laminate must not automatically be something that can be produced (i.e. 90% glass contents ) or WILL be produced (this depends on the skills of the maker/s)
Something really safe under all conditions will normally end up too heavy, unless you do sample testing and feed the gained data into your project calculations.
Saying this, I have 'simplified' scantling rules in mind.
One other option is to calculate 'Finite Elements', that is, after you determined your structural set-up (stringers, frames, bulkheads and whatever else) you will find your design split into panel segments that are unsupported.
Next you need to know the pressures there (Dynamic, because they are higher than the static ones - - - of course) and the calculation will bring you to the minimum laminate requirements.however - a minimum weight usually also gives minimum lifetime. Laminates get weaker with time passing.
Your last option would be trial-and-error. But watch out that you stay alive.
At last a boat is a participant in public traffic. You would also not make your own motorbike just so, and go to town on it - would you?

In my eyes, a design is worthless, when it is never built in reality. Or meant to (hope, that some forum members get the message here ).

If you plan a one-off, that will perform really well (or at least stisfying), I am afraid you have no other option than to study further. Here come the (professional) designers into the picture, because they know all this already and will save you a lot of time for learning something that you perhaps will never again need to know during the rest of your life.
If you go on your own - well - go ahead; but you need to be prepared for perhaps less performance, or more investment than necessary (time- AND money- wise)
The nice thing about boats is that they do not fall from the sky if something goes wrong; the remaining risks (emm, statistically) are not much higher than - walking - crossing a town's street. Only make sure that others are off the scene in case that you test something extreme.

[daiquiri]

Originally Posted by Eric Sponberg

So even if you had a spoiler well forward in the bow, would it work well enough to keep the bow down close to the water? I don't know. Maybe someone should try that.

Maybe someone did... Is it my impression or the forward foil of this racing boat actively changes the pitch as the wave action tries to destabilize the boat: http://www.youtube.com/watch?v=6A6XK...ailpage#t=320s ?

Cheers!

[Eric Sponberg]

Originally Posted by daiquiri

Maybe someone did... Is it my impression or the forward foil of this racing boat actively changes the pitch as the wave action tries to destabilize the boat: http://www.youtube.com/watch?v=6A6XK...ailpage#t=320s ?

Cheers!

Hi Daiquiri--Yes, on that and on other videos that I looked at it seems that the forward foil is keeping the bow down. It is not apparent whether this is automatically controlled or manually controlled. Thanks!

Eric