pontoon boat with planing hulls?

[stonebreaker]

As long as it stays level, I'm cool. I just don't want to dig in the outer sponson and roll the boat, that's all. I'd rather figure out some way to add some lift to the outer pontoon so that in a worst-case scenario the boat would spin out, not flip.

[marshmat]

If I recall correctly (someone make note if I'm wrong), Benchmark gets lift on the outboard hull in a turn, by making the outer deadrise of each hull steeper than the inner deadrise. The hull bottom facing the ocean might be 29 degrees; facing the hull tunnel, it might be 22. Thus when the boat turns, the outboard hull tends to push upward more than the inboard hull. These are fairly typical V-bottom hulls, just with asymmetrical deadrise.

[War Whoop]

Originally Posted by stonebreaker

Kelly,

Thanks for the links.

The Clark boats are pretty much exactly what I had in mind, but there's not a lot of info on their website. If you know where I can find out more about them, I'd be grateful. Meanwhile, I'll be surfing the net. The Manitou guys seem to have struck a nice compromise between performance and comfort - the larger center pontoon that allows the boat to bank into a turn instead of turning flat, is a great idea for handling comfort. It helps that there's a local boat dealer that carries them, too.

Of course, being the stubborn damnfool gearhead that I am, now that I know this idea is not only possible but practical, I'm even more determined to build my own boat that's faster and lighter than either of those two. The Manitou system, in particular, to my untrained eye, anyway, appears to have sacrificed a great deal of speed for handling comfort by putting in the central pontoon. This seems like a good solution for a commercial venture. Actually, it seems like an excellent solution from a sales viewpoint because it delivers a very good compromise between speed and handling in a very cost-effective manner.

The Clark boat seems like less of a compromise. I guess I'll have to contact them to get some sort of price list. Still, judging by this picture,



They appear to be using a very simple design that doesn't require a lot of fabrication or custom materials, just aluminum sheet and a simple extrusion. Does this appear to be an efficient shape? Is there some other hull design that, perhaps for reasons of labor cost, they're not using but would provide a performance increase? Dick Cole's cathedral hull, for example, or perhaps a stepped hull? I have an advantage here because I will be getting my labor for free. What I need is help picking a design and/or some pointers towards planing hull design books and software.

Thanks in advance for your help.

Randall Stone

Now that is way cool !

[kagraham]

i would recomend just buying or taking ideas from these guys, http://www.playcraftboats.com/ they seem to have the right idea. I saw some similar with modified V8 I/O motors on tablerock lake in Missouri. I cant find a website for those though..

[stonebreaker]

Nah, that's just another 'toon with lifting strakes attached to standard pontoons. Great solution so far as cost-effectiveness, but like Manitou, they have to add that third pontoon for some reason - I assume the lifting strakes either just don't generate enough lift to work with only two pontoons, or they can't be made large enough for structural/strength reasons on only two pontoons.

[DTVM]

I have a strong interest in your idea about the hickman pontoon system. Have you gone any further with you idea?

[stonebreaker]

Haven't gotten past the model stage so far, due to lack of funds. However, I'm planning on picking up a tig welder with the tax return and then I can get serious. I'm also wondering if any of the free/cheap design programs could produce a set of shapes that I could give to a sheet metal shop to cut out of aluminum sheet, or if I'll have to build a full scale model with cardboard or something and give the cardboard shapes to the machine shop.

[skypoke]

Hang on, Stonebreaker, you don't really want a tig machine, you need to use MIG. The 5052 alloy you spec will work though it's a bit malleable and you would most likely use 5083 or 5085 for more strength and corrosion resistance. But for a recreational duty boat the 5052 will save you lots of money on material and be just fine. Wire for mig filler will be 5356, works with any of these alloys.

Why not TIG? Well, granted it does produce a pretty bead though the new MIG machines can pretty well achieve this too. Problem with tig is it's very slow and heat generated is enormous...because you're going slow and adding filler by hand. With mig you will be running bead really fast though even with this process you will be battling heat. Heat equals distortion and it's the single largest challenge you will face in building. Even though you can lay down several feet of mig bead a minute, you will only be running beads a max of 4-6 inches long at a time. Any more than this and you will have a warped mes on your hands. I'd suggest your first investment be in a book called "Boatbuilding with Aluminum" by Steven Pollard. It's in print, available anywhere, relatively cheap, and the bible as far as I'm concerned. We just finished a 28' alloy pilothouse powercat so have some experience in this. Sounds like a great project!

By the way, if I was building such a simple hull form I wouldn't mess with having your material plasma cut...it's relatively expensive, takes a lot of cad work to generate the files, and most cut services won't have much interest in this small project. A good carbide blade on a skilsaw will easily cut these simple shapes. It's not hard to template plates over your frames and each template will most likely work for 4 hull plates in yer cat. Good luck and let me know if I can help.

Chuck

[stonebreaker]

Thanks for the tips, especially the one about the skil saw. I appreciate the tip about the tig welder too. I'll keep an eye out for a machine that will accept a spool gun.

[stonebreaker]

BTW, I ordered that Pollard book you recommended. Any other reading suggestions would be appreciated. I'd like to find some guidelines on construction - calculating hull thickness, framing, all that stuff. My problem won't be making things too weak - quite the opposite. I tend to over-engineer, which makes things safe, but slow.