What type of hull is right for me?

[asbruce]

My brother and I want to build a boat and are trying to figure out what hull material would be best for us. I am looking for some resources or input on the subject.


Thanks,
Aaron

[Jeff]

Welcome to the forums Aaron!

What size boat are you interested in building?

Do either of you have any previous experience with woodworking, fiberglass, or welding?

[Jeff]

I'm sorry - I just saw your other thread (http://boatdesign.net/forums/showthread.php?s=&threadid=1371) that you are thinking of a Bruce Roberts 434 - quite a big first project!

The sensible advice would be to build a skiff first in the material you choose. (I've always been one to jump right in too though...)

Is cost a large concern when selecting a material for you?

Will you be building inside a shop or outside under a temporary enclosure? Where are you located temperature wise?

Wood/Epoxy doesn't require expensive or sophisticated tools. The encapsulation must be perfect, otherwise the plywood will rot. Once sheathed with glass, it is strong and light. Epoxy is costly and must be painted to resist sunlight. A cold molded wood/epoxy hull isn't very abrasion/puncture resistant though compared to metal. Also any fiber sheathed in epoxy will flex and loose some strength over time.

Fiberglass is strong but building a one-off is not cost-effective if you use a plug-mold-hull method becuase the costs of the tooling, even if built "light-weight" are not spread over a run of boats. FRP is also more brittle than aluminum or steel - it will break instead of giving. Finally, if you use the boat hard, you have to maintain the finish or else you will run into problems with blistering over time.

Cored one-off construction is great for home building resulting in a light stiff hull, but it requires a lot of time and muscle hand finishing. You don't need elaborate tools, but it is time consuming and you are potentially in close contact with a lot of hazardous chemicals and fumes from the resin which you need to protect against breathing. Also it is not impact-resistant and depending on the exact construction, a small puncture can result in major damage. Finally, any water infiltration into the core will spell trouble, so the finish must be maintained well.

Aluminum is strong, light and corrosion resistant. It is expensive and difficult to weld, but you can work with it using lightweight tools and can make repairs with woodworking tools. Welding is more difficult than steel though. It is also susceptible to electrolysis. Aluminum will cost 2.5x - 5x as much for the intial material and welding as steel, but this will even out over time because it doesn't need the repeat coatings that steel hulls do.

Steel is cheaper than aluminum and fast to built with and strong. It is heavy and needs meticulous maintenance though. Because of the minimum plate thickness needed for welding, recreational boats built from steel are typically overbuilt by a considerable margin on the skin thickness and thus they are strong but heavy. Finding people to repair a steel boat is easy though.

Copper-nickel is even more expensive than aluminum, but it resists corrosions. Like aluminum and unlike steel, copper-nickel does not require anti-corrosion maintenance (painting and repainting). Copper-nickel resists bio-fouling and does not suffer aluminum's susceptibility to electrolysis.