Shapes For Fiberglass Trimaran Hull

My next boat will probably be a tiller operated power cat, and then the third I have planed is a small motor tri.... I wouldn't mess with steps. I think a lot of monohull mass market boats include some steps because buyers think they look cool, and in racing applications they've been proven to work, but in a race boat almost all the weight is fixed so the steps can be optimized and functional. In a recreational boat you're going to have weight all over the place and moving around so the steps will probably do nothing or worse except create horrible vortices, etc. If you just do a modified v with most of the buoyancy in the center hull you'll probably get something that works well.... If you're designing in a computer it's easy to make a scale model to establish weight and balance and initial stability.

Another concern is insurance. If you create a cool or unorthodox design on your own it will be the devil to get anyone to insure it, whereas if you go off existing plans (and even smodify them) y0u'll still need a specialty company but it'll probably be painless. I'm dealing with insurance on my current build, Jezebel. At this point, I have the three years I spent building her laboriously timelapsed into 80 minutes; a 42 page operations manual with SOR, reserve buoyancy/weight/balance, Lloyd's Rules scantling calculations; a professional dry marine survey (rated 'above average' and just under 'Bristol quaity'); a perfect track record as a professional OUPV captain and water professional... and I'm feeling like I'll end up needing to strip $15k of brand new electronics and rigging off her and give the hull to a maritime academy as a tax write off. Last resort will be trying to hire a naval architect with experience in cold mold construction, RIBs and true SAR to try and explain her to insurance underwriters. This for a 20' monohull powerboat.

 

Wow! Excellent point and thank you for bringing this up! The insurance aspect is not something that I've considered.

Thanks again

 

Just download free SketchUp and watch a 10 min tutorial of "how to build an aircraft fuselage" that applies to boats, you only make half the hull

Just get out the engine closet and design a sailboat, preferably an engineless boat and you will learn real lake or sea competence and the lighter the boat the easier and practical

 

Total BS and nonsense from the usual source You couldn't buy the mainsail for that money. You should put a turbine on your laptop and take it for a ride outside of your mom's basement.

 

The steps on the hulls on a narrow hull may help at rather high speeds. You should check the designs from Thornycraft. He is, as far as I know, the inventor of stepped hulls. For what you are doing, it would be more of a complication. Also, unless they are properly designed, they will create more drag than anything. Simple is good.