help with fiberglass thicknesses on bass type boat

[mrbaseballny]

Hello there,

I'm new to this forum, I'm glad I found it as have read so much in the last couple of days. I have read a ton of books from my local library on boat building, design, composites, and many others.


however, the one thing that I have not found in all my reading is what thicknesses the final fiberglass boat hulls have? I am wondering if my boat is going to be 18-20 feet long with a beam of 83-90 inches does my fiberglass layers have to end up at such a thickness like 3/8" or so?? I plan on using this on local lakes only. I have done fiberglass car bodies, but never done anything with boats.


Thanks for any suggestions on this or where I can be steered to:) to find my answer to this question.

[FAST FRED]

The problem with GRP is seldome strength , its usually stiffness.

Unfortunatly internal stiffness adds a load of build time .

Simplest is a cored hull where the stiffness comes from an inner and outer layer seperated by a core.

Single hull of glass will be very heavy if the thickness of the glass is the only stiffiner.

FAST FRED

[Eric W. Sponberg]

Dear Mr. BaseBall NY,

Figuring out the thickness of a fiberglass hull is a complex engineering problem. You cannot reduce it to such and such a thickness for any given boat size. The weight, shape, and speed of the boat are important factors. Also, the materials themselves are important--knitted fabrics are stronger and stiffer than woven fabrics, for example. The choice of resin also plays a part--epoxies are better than vinylesters which are better than polyesters for strength and stiffness. But along with that goes cost, with epoxies being more expensive than vinylesters which are more expensive than polyesters. Another important factor is the design of the internal stiffening structure inside--generally the more internal structure, the thinner the hull can be. And it also usually follows, particularly on larger boats, that the more internal structure there is, the lighter the boat will be. This is because the hull skin accounts for about 2/3rds of the boat weight, whereas the internal structure is about 1/3. So you can add more structure inside, and make the boat lighter overall. On a boat you are considering, however, this might not be true, because you do have to deal with certain minimum thicknesses simply to create the structure.

Also, as Fast Fred has mentioned, cores add another dimension to the thickness and weight question, along with strength, stiffness, complexity and cost.

Eric

[cyclops]

A Bass Boat is very complex because they are not deep at all. Are way overpowered. Can sink in the blink of a eye if not carefully filled with enough foam that is designed in. They are by design, speedy, gasoline tanks that are air borne and will flip upside down if forced to jump a 2' to 4' wake at high speeds. They are really racing hydros with fishing rods on them. Please do not build one yourself. Buy new or used and paint or modify it to your hearts content. Remember, the design is already maxed out to safe limits structurally.

[mrbaseballny]

A Bass Boat is very complex because they are not deep at all. Are way overpowered.

I don't plan on overpowering mine, I want just enough power to get going, maybe 40pmh. By day I am a Mechanical engineer, so this would not be tried without proper attention to details. I get more satisfaction out of building my own stuff than buying commercial products, just the way I am:)

I appreciate the comments and suggestions, anyone on this forum that have actually built their own bassboat and posted pictures? I see alot of questions from those that wanted to build a bass boat but no photos:)

[cyclops]

OK Baseball, I feel for your frustrated design and build desire. I am the same . I am doing a 1930's straight bow 2 seat speed boat. Wood WITH a full set of plans. And building instructions. Big difference. Have you tried some of the plans and kit boat companies. It is easier and very sucessfull to modify a known design by asking the company what your changes will do. They do tell you the +&-. Enjoy.

[mrbaseballny]

cyclops,

I've built a wooden canoe, and a wooden motorboat when I was a youth with my dad as a kindof father son project. It turned out to be more of a son project. Both turned out very well:) but I would like to now try my hand at composite building. I decided that I wanted to build a bass boat b/c I love to fish and the bass boats have anice wide beam that usually is very stable when fished from. I'm sure I will over research this boat built, but I would rather have too much knowledge than not enough, so any info anyone is willing to share is much appreciated. Also aif anyone has some books that they would recommend I'll gladly listen.

[cyclops]

Do a web search of --bass boats -- and start emailing every one with what you want to do. Good luck.