Shapes For Fiberglass Trimaran Hull

Gonzo, I like and prefer your idea of having only two floats instead of three, with less cost to build, less wetted surface and this would reduce the weight of the hull. I could incorporate a recessed area in the center of the deck for my fuel tank, gear storage etc.. By rough estimation, wouldn't I need (2) floats that are approx. 30" wide to provide adequate floatation? I think this would bring the weight down to roughly 6,000 lbs. fully loaded with fuel, gear and max. people aboard.
Thanks again!
 
A flat bottom needs less power to plane, but pounds more in waves. Slim hulls are less prone to pounding. You can have a moderate vee forward, turning into a flat bottom. The one advantage of a tritoon is the installation of a single engine in the center. On the other hand, you could have twin engines that are always good in case one has a problem.
 
Unique Trimaran said:
Gonzo, I like and prefer your idea of having only two floats instead of three, with less cost to build, less wetted surface and this would reduce the weight of the hull. I could incorporate a recessed area in the center of the deck for my fuel tank, gear storage etc.. By rough estimation, wouldn't I need (2) floats that are approx. 30" wide to provide adequate floatation? I think this would bring the weight down to roughly 6,000 lbs. fully loaded with fuel, gear and max. people aboard.
Thanks again!
Click to expand...

1000 lbs reduction is a huge improvement.
 
Am I accurate with using (2) 30" wide floats that would be roughly 26' in length to provide adequate floatation for 6,000 lbs.?
 
That would need about 10 inches of immersion.
 
Would 10" of immersion be considered an ideal amount, or would you consider this to be excessive, or not enough?
 
Also, regarding the 10" of immersion, is this fully loaded at 6,000 lbs. overall weight?
 
Yes. 2.5 x 23 x .9 x 62.4 lbs = 3229 per hull.
 
@Unique Trimaran having a boat design programme can easily give one a false sense of security.
Especially as you admit that you have no design experience.
If you want to build the boat yourself, you will save a lot of money in the long run by buying a set of plans for a boat that is proven to work well.

From what you have said above, one of Richard Woods' small Skoota power cat designs might work for what you want - have a look at the range here -
Sailing Catamarans - Click here for Power Catamarans (8 designs) https://sailingcatamarans.com/index.php/designs-2/6-powercats

Bernd Kohler also has some very neat small sailing and power cat designs, and some of the sailing cats would also work well as power cats on their own.
Plans & Kits - Plans by designer - Bernd Kohler - Page 1 - Duckworks Boat Builders Supply https://duckworks.com/bernd-kohler/
 
Ideally I don't want to go wild with horsepower, so I would like to have the most efficient planing hull possible and yet provide adequate floatation for 6'000 lbs. fully loaded. The attached drawing shows the stepped hull for my boat, but Gonzo had a great point about maybe having a V forward and then maybe transitioning to a flat bottom for planing reasons. Keep in mind the attached drawing is showing my original trimaran style hull, but just in the last day or so, I think it might be a better idea and agree to shift to (2) floats instead of (3) - thank you Gonzo. The (2) floats would need to be larger (roughly 30" wide) to support the 6,000 lb. fully loaded weight but my question is now this: Would staying with the steps in the hull be best for the larger (2) floats? Or would maybe keeping the first step in the hull, and then transitioning to a more flat surface after the step be best? Or, would eliminating the step altogether be best if the bow remained the same V shape and simply transition to a more flat bottom near the middle of each float, while maintaining a chine throughout the length of the flatter area?
Performance aside, I do think the steps look pretty cool!
Please see the attached.
 

Attachments

Saffier24bvi__LMA0253_p-1798x1200.jpg


This boat sells for 170.000, but a replica can be built for 2.000 with second hand gear and plywood without any resin

Any daysailer will do just fine and sailing will give some competence in the water
 
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Unique Trimaran said:
The dreaded Herreshock strikes yet again with unrelated info
Click to expand...

I just love that boat and anybody who says the contrary is lying...lol I just found it the other day, it's the last saffier of 2024 and haven't checked , it's 24 lite

This boat is just an envy and tease treat

Saffier24bvi__LMA0901_p-1000x666.jpg


I could send you a 3d model that you can edit and print for plywood kit, pretty easy and fast to build, i just finished it today I'm going to upload it to grabcad and SketchUpwarehouse
 
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I forgot pulse 600 trimaran, if you want some practical multihull for lakes and fast this is it

49c9ed8c5a9b7664f4aba3bcd741f957.png


trimaran-pulse-600.jpg


Pretty easy to replicate with thin plywood
 
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