pontoon boat with planing hulls?

Some of the faster cats don't bother with a full "V" on each hull. Instead each hull has a slanting flat bottom, angling upward toward the outside. So taken together the two hulls have the same effect as a "V". Step features can be tricky. Cat designs don't have the need for all the gimmicks found on some V-hulls. KISS rules.

Kelly

 

Have you ever heard of a Hickman Sea Sled? I came across a bunch of info here.

It appears to function somewhat differently from a modern tunnel hull in that it generates most of its lift from an inverted bow wave, instead of aerodynamic lift. What air it does trap under the hull is more of a friction reducer than a lift generator.

 

Stonebreaker - Yes, Morley Smith's articles are excellent! You will learn much from reading his material. I have worked with Morley over the years (I now have all of his personal research notes and archive files), as our development interests have always been quite similar. His thoroughness of research and understanding of planing hulls is one of the best in the world.

If you are interested in a power catamaran design, there are several articles on power catamaran design available for download. Also check out "Secrets of Tunnel Boat Design" book.

The short answer to your original question re: "pontoon boat with planing hulls" is that, yes, the tunnel hulled design for such a boat is a very valid design.

 

Jim,

Thanks for the link. I'm really facinated right now with the Hickman design. Do you have any articles on it? Or know where I could find some?

<EDIT> I'm wondering at what speed a true tunnel hull will begin to generate less drag than the Hickman hull. Since I'm not really targeting triple digit speeds (i.e., I can't afford that much speed), I'm wondering if pontoons in a long thin Hickman shape wouldn't be more efficient at 60 mph than a tunnel hull sponson. Since I also want to pull skiers, I'd like to know if the Hickman shape would get on plane faster, as well.

 

Hickman

The Hickman design has very flat deadrise, and normally, has more wetted surface than a typical tunnel hull design....thus, acceleration to plane will normally be quicker with Hickman. Overall drag, however will be more in planing, due to exposed wetted surface area. Also, Hickman bottoms, due to very flat (zero deadrise), tend to have quite a rough ride in heavy waves. Tunnel sponsons can have increased deadrise to "soften wave impacts".

 

A trade-off! Who'd have thought an engineering solution would have a trade-off?

Question: Could I use your tunnel boat design software to analyze Hickman pontoons?

 

Pontoon boat with planing hull

Stonebreaker,

There appears no reason why a pontoon boat could not plan having the correct design. I saw you refereed to my father Dick Cole and his Cathedral Hull design.

 

Yes, I was looking at something like the cathedral hull before I stumbled on the Hickman hull - Sort of progress in reverse. Actually, making two Hickman pontoons would be something like splitting a cathedral hull in half longitudinally, wouldn't it?

 

Planing pontoon boat

I recently designed a planing pontoon boat for Smokercraft. At 22' it did 40 MPH on the first try with a 150 HP outboat. This is almost twice as fast as the cylindrical pontoon hull. This will be a production boat soon, with some features I can't tell you about yet.

It is pretty simple, just a pair of narrow deep-vee monohedrons, very simple but it works a treat. There is a special chine though, which I can't talk about yet and the construction methods are new.

 

http://www.clarkboats.com/

 

The Clark "Performance Pontoon Boats" are indeed similar to the boats I did for Smokercraft, and I imagine the performance is similar too. Our innovations are primarily in the area of construction methods.

 

Great, maybe you can give me some pointers then. Both Clark and Tracker make their boats from .125" 5052 aluminum. I would assume they have good reasons for choosing this alloy, but I haven't been able to find what filler metal to use when welding it.

 

Stonebreaker 5052 welding

That thickness and alloy is pretty standard for these boats. I'm not a welding expert.

Our construction methods do not use welding or rivetting. Also, I'm a Naval Architect, not a builder. I tell builders what shape to make the boat, but in general, they figure out how to build it. Sorry!

 

OK, I have a question on planing hull shape. What part of the hull makes a planing hull bank into the turn like an airplane? I'm assuming that as the boat turns, the vector of the water in relation to the bow changes, such that as you make say, a turn to port, the hull slips a little so that the apparent vector of the water in relation to the boat comes in from the starboard bow instead of head on? And the lift is then generated by the angle of the hull bottom to the water moving past it?

I can picture this easily on a v-bottom, but have trouble with something like a cathedral hull or even a flat bottom. In the case here, I'm considering using a Hickman inverted vee hull, and I don't really understand how that shape would generate the banking lift to turn, either.

 

With prop-driven planing monohulls, part of this 'banking' motion in turns comes from having the thrust on an axis considerably lower than the boat's CG and CB; turning to port will cause that thrust to push the stern to starboard and will also roll the boat counterclockwise as viewed from astern. With jetboats that have their nozzles pointed perfectly parallel to the direction of travel, there's considerably less banking than on a prop-driven boat (most jets angle down a bit though). So the turning of either the drive or rudder contributes to the banking motion; Stonebreaker, you seem to have the right idea as far as the rest of it (the hydrodynamic part) goes but I don't think I can clarify it much without pictures. Once the hull begins to bank, of course, the effective deadrise is higher on the outboard side and lower on the inboard... it is of course a pretty complicated motion to analyze and I'm afraid I can't explain it too well here.
You might notice that with cat and pontoon hullforms, the boat usually stays pretty much level in turns. With asymmetrical hulls it is possible to make a cat bank like a deep-V (a la Benchmark 38) but most cats have very high initial stability and won't carve into turns like V-hulls do.