Thinking ’bout boat hulls

Well
Still don't have the drive perfected or a prop.
I have been in contact with the prop people and it sounds like I CAN get a prop for my purpose, a 62" two blade wooden prop for around $500 to my house.
Now what about a hull?
In My heart I want to try a catamaran type set up.
I think I can Fab it my self.
I can get 4x8 sheets of .10 5052 Aluminum for $118 a sheet here in town.
There about 50 pounds a sheet.
I made a template with card board to use two full sheets with only 4 cuts and three bends, for the entire float.
With that thickness I feel I can bend it gently over a peace of angle iron on my deck. The corners where they have to join I'm thinking 2" angle Aluminum with a rivet or two and Permabond adhesive here the sheets come to gather an over lap of 2" on each a few rivets and Permabond. I would like to try to roll the top edges over a 1" pipe and even glue in a solid peace of AL pipe.
Three strips of AL channel in each Cat.
This will give me a cat 14' long on top and 11'in the water. It will taper from 24" in back to 18" in the very front. That's a 3' rake, I may change it to a 4' rake and a 10 foot bottom , have not set that in my mind yet.
I'm planning on gluing a sheet of 20 gauge sheet metal to the bottom and three strips of 4"x1/2" UHMW plastic glued to that with several nylon screws to help keep it on. Paint it all with GatorGlide to the water line.
I'll spray foam the front 3 feet and the back 4 feet.
I'm planning on using "Expanded" Al covered in airplane canvas leaving the middle 7 feet empty for storage and battery's, and fuel cells, one on each side for balance, and covered in the airplane canvas .
I think I want the "Boat to be 6 to 6 1/2' wide and 5 feet in the front.
I'll make a deck over the cats to hold the seats and motor and prop with it's cage. I'm thinking about using "Gate Panels covered in Chain link fencing and canvas . I'll need some kind of "CAB" too I think it will be AL tubing and said canvas ???
The boat could be around 700 pounds with the VW motor and prop set up.
What'cha think ?

d

bear thanks
I did figure the sq inches , I did not keep the numbers but I compared them to the boys 16' mud boat. Before I made the template. They are very close to the same. 24 inch times the 11 feet timed two ISH. that's 6336 sq inches. the boys boat is around 6500 sq inches.
His runs around 1200 pounds plus people with 3 we float in under 4" of water. Using full 4'x8' sheets of aluminum the sides of the Cats will be 12" hi in the back and 15" at the front.
I did calculate how much foam I needed with your formula on one of the other post and I would have enough to flout 1100 pounds in the event of a problem the only part that can hold water is the center part of the cats.



Edited by d4570

His 16 foot jon boat is only 40 wide and 12 feet in the water the rest never gets wet...
the 11 x 2 is the bottom , each cat is about 30 x 14 on top

Edited by d4570

My thoughts exactaly !

Just a thought.

The prop thrust is ALL high above the hull.
Stationary friction is larger than moving friction.
Remember shouting "keep it moving when pushing a car,
boat, or large box, furniture, etc.

So it is going to take maximum thrust to get it
started, less once it moves and even less on plane.

your sponsons/pontoons are narrower in the front. So
as you power up to get her moving/started The thrust
is going to pull the rear up out of the water.mud.
The high thrust is going to push the bow down (sort of
twisting it). This is going to transfer the weight to
the front section of your boat, further pushing the
bow down.

In soft mud or snow you might not be able to overcome
that high starting friction. A wide sponson in the
front or a solid front would give more surface to
support the front downward pressure on starting.

Just more thoughts, smoking a cigar and having my
first evening vodka.
****************************************

D, unfortunately, there is no way to really check this
out without a build. this is why engineers design
things, then double what they need. better to over
build than be under design and not fly (said the
Wright brothers).

Neither of my bro' are engineers nor scientists. When
I moved away to Buffalo they were clueless. So they
built a pontoon boat out of 55 gal drums; hoping it
would be a duck blind and could move out to hunt with
a 5 hp outboard. Disaster, it didn't move forward,
just flipped upside down and rotated about is self.
they tried it in a 1/4 pond. Again unfortunately, i
wasn't there to witness, but it took them 3 hours to
get it out. LoL
I got stuck rebuilding the outboard.

You've but 10x more thought in to yours than they ever
did. My only fear is that you need more bottom
surface up front. Especially as you want to run on
mud, soft dirt and snow/ice.

Think about it.

What ever you decide, I'll ride volunteer to sit in
the extra seat on the test run (with helmet and ear
plugs).

D, it is 4am here, still working away slowly.

see my post on Handloaders re changing thrust vectors.

Thoughts on the jack method.
for the jack to work the whole assembly will need to
be hinged (3 point suspension at best). A 4 or 6
point rigid suspension would mean no wobble, or
vibration. Vibration will be your biggest enemy.

If the scissors jack is on the front, it would need to
be 'up' while running. Jacks have a LOT of wobble;
and would get more wobble after a half hours use!

Also If you tip the motor/prop upward/downward about a
foot or so, that isn't a big change in thrust. A
'barn door' flap or two would be much, much more
thrust deflection upward.

just thoughts.   looking forward for a ride.

that's OK I'm on a 7 year plan.

I do know a lot of my jet boat guys are shifting the in boards forward 5" to make them plane at half the normal speed .
I plan on shifting it as fare forward as I can just for that reason.
It makes them look a little front heavy when there stopped

Edited by d4570

Yes, that is the idea. Check out a small plane piece.
The horizontal pieces are vee-slotted for the vertical
pieces. So they are not front-back of each other; but
all close to the fan/prop.

Air foils like this are really effective. I've stood on
the brakes of a Cub and lifted the tail off the ground
without moving. Just a little up elevator.

And with the air foils back there it will be super
responsive (no waiting for the jack) and you can trim
from a joy stick as you go fast.