# yes another pontoon design...

Discussion in 'Boat Design' started by spencer321, May 31, 2013.

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### spencer321Junior Member

alright, i got a couple cad models to show what i have in mind let me see if i can throw a little description in here to make it worth something.

pontoons:
24" wide by 12" tall by 16' long. 2"x2" lumber skeleton. 45 degree angle on the front. 12" spacing on cross members. 1/4" ply all over. 10oz cloth and epoxy resin.

deck:
16'x8' cross member ever 12" to match pontoon cross members. would like to go aluminum 2"x2" either square or C-channel 6061 cross members. deck in 1/2in ply with 6oz cloth or 1/8th 6061 aluminum

motor would be a 40hp outboard I already have, my goal would be to keep it as light as possible, be capable of shallow draft, carry 3 ppl max and heres the big one... get up on a plane, i don't expect a rocket ship but 20-25mph would be amazing.

by my calculations there are ~11 square yards of surface to each pontoon, 10oz cloth at a 50x50 ratio of glass:resin yields 13.75lbs of fiberglass

the 2x2 skeleton is approx 76lb based on 36lb per cubic foot of timber and 135 linear feet of 1.5"x1.5"

it will take 3 sheets of 1/4 per pontoon estimating ~25lb per sheets yeilds 75lb

75+75+13.75=163.75 I will use 200lb as a safe over estimate per pontoon.

the deck (assuming 17 2"x2" 6061 1/8" square and 1/8th 6061 floor) would weigh approx 365 calculated, use 400lb as safe estimation.

I believe the motor weighs 177lb

total weight should be (163.75x2) + 365 +177 = 869.5
using (200x2) + 400 + 200 Is 1000 giving myself a 130.5lb cushion

2'x1'x16' with the flair should float ~925lb with 6"draft

now... anyone care to input, tell me i'm crazy or great idea or go to hell lol

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2. Joined: Jan 2006
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You will be better served by using thicker ply an fewer frames. You may very well be even better served by abandoning the pontoon notion and going with a barge like boat. You can sit in a boat as opposed to on a pontoon like boat.

Pontoon boats require a rather robust and heavy deck structure that includes a bunch of cross beams. Pontoon boats are also more problematic to trailer, load, unload, store.

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### hoytedowWood Butcher

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### PARYacht Designer/Builder

Agreed with the above, plus if you really want shallow draft, limiting your buoyancy into a couple of narrow 'toons isn't the best way to go. You'll get less draft with a flat bottom, plus you only have to build one hull instead of two. It's also easier to propel this type of hull compared to a pontoon style, which translates into better fuel efficiency too.

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### spencer321Junior Member

what do you mean by "barge like boat" like one large wide flat hull?

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### PARYacht Designer/Builder

Yep . . . I'd make it with some rocker for maneuverability, some flare for spray control and additional deck/interior volume, plus a few other "details", but yes, a "barge like" hull would be a better approach, considering what you're looking for.

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### spencer321Junior Member

sounds like an airboat with a little deadrise, no offence

8. Joined: Nov 2003
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### PARYacht Designer/Builder

Airboats are typically placed on jon boats or garvey style of hulls. The jon boat is sort of barge like, but not really when you really look at them. Barges are slab sided, dead flat bottomed, with a simple inclined bow (if at all) and pretty fat beam/length ratios. Jon boats aren't really. I'm not offended by airboats, which typically have no deadrise, though the garvey hulls do have some in the forward sections.

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### spencer321Junior Member

Obviously im not a naval architect, I am however a comp science senior so I understand what your saying. I read thru all 30+ pages of that build and it really is a scaled down version of what I had in mind, what im still not getting and I couldn't find was why it didnt work. Fiberclass pontoons and catamaran coaches for one example work great and are very close to flat bottom, why didnt that build work?

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### hoytedowWood Butcher

If it(TEOTWAWKI) were longer and the hulls spaced further apart, it would have worked much better. It works in a limited way but is very inefficient. The same shape with one hull instead of two would probably go twice as fast.

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### hoytedowWood Butcher

Lack of flare at the bows makes for a very wet ride in choppy water.

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### spencer321Junior Member

I understand wet and choppy its flat bottom and straight sides but I dont understand why he couldn't get his to hit a plane and move instead of bulldozing thru the water

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### hoytedowWood Butcher

The bow waves cross between the hulls where they pile up, hogging the hull like a suction cup holding it back. Even when I am on the boat alone the speed is less than optimal. If the arrangement allowed the wave cross to be behind the transom you would see a great improvement in performance. messabout will better be able to answer the science of this and please correct me if I got it wrong.

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### spencer321Junior Member

Alright... is there anyway to know if 16ft and a 4ft gap between hulls would sufficiently

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### hoytedowWood Butcher

I think that would work much better. If you had a single hull tunneled you would have more buoyancy at rest.

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