Aluminum 12' twin sponson boat

[Doug Doty]

I am building a 12' twin sponson boat and here is the 1st of two of the sponsons to be welded up. It is made of 5053 aluminum and welding with 5356 filler. It gets a 40 hp. mercury. Will look kind of like a www.craigcat.com boat with 3 wide seating when it is done. The top is still loose as there is stuff going on inside still to come. This is my first major aluminum project other than some small tanks and tabs and such. It did not go with out problems as I learned how plasma cutting leaves an oxidated edge and i made it hard on myself by getting it all tacked up from the inside and not being able to adequatly clean after I realized I needed to dress all the edges that were done on the HD plasma table. The 2nd. one should go much better and only take 1/3 of the time.

Using a Miller Dynasty 300DX TigRunner

[Winger Ed.]

Cool project.
I hope it comes out well. Something you might consider is to pour it full of that 2lb/sqft foam stuff. It'll make it almost indestructible, as well as unsinkable.

After I got off into Alum. boats back in the 80's.....
I'll never go back or build one out of resins or termite bait.

Here's a couple pictures of the 2nd boat I built in Al...
Its a work in progress. I still can't get it over 90mph with the stock Merc. 150.

With a few trips to the scrap yard, and a TIG----
you can make your dreams come true.

http://home-and-garden.webshots.com/album/76082519ymNNLn

..

[fun4now]

thats going to be a realy cool lil boat when you get it finished up. be shore to post us more pic's as it progresses.
Winger Ed.
thats a nice looking boat too, what is the long tube section for??? looks like you were planing on putting in a jet engen. that thing has got to be fun.

do you guys have to get a builders title for them so you can get a boat licence # or some thing like that or can you just use it as a home made boat without any one messing with you ??

[Doug Doty]

I'm in Indiana and it is next to nothing, same as a homemade trailer. Get it inspected, they issue a #, you affix the # to the hull, get it re-inspected and go backe to the DMV for your registration #s

Ed Winger. I feel the same way, I have always dug building stuff, My welder brings me a ton of enjoyment.

Here is a few of the projects I have done in the last 3 years.

[fun4now]

Doug Doty
ok you are oficaly haveing too much fun in that shop.

[Doug Doty]

I have always spent most of my time in my shop but for some reason the last couple of years I have got bound and determined to improve my welding skills. I have a buddy that is an ace welder and that is probably what is driving me to be better. I asked him to come down this evening and he helped me a bunch. i am working with clean raw edges now and things are a ton better. Got another half of a pontoon welded up this eve while I was getting lessons from Vernon House my mentor. This aluminum stuff really makes you buckle down and seperates the men from the boys, I am just coming out of puberty I think.

Doug...

[Winger Ed.]

Winger Ed.
, what is the long tube section for???
do you guys have to get a builders title for them so you can get a boat licence # or some thing like that or can you just use it as a home made boat without any one messing with you ??

I don't want to steal Doug's thread, but its just a cowling that covers a frame to help reinforce the hull's ability to resist a twisting motion.

To title a homemade boat** here you take all the reciets for your materials to the Game Warden/Parks & Wildlife office and they inspect it, make a value judgment that it is what you claim it to be,,,, then issue a title with the manufacturer's box stating 'homemade'.


**
Its the same with a homemade car, you just go to the DMV/license plate office instead.

.

[fun4now]

heck if its that simple i might just make me a car & amd boat, gotta hall it to the watter right.
thanks

[Doug Doty]

Here is the two sponsons set up on horses with the tops just tacked on. I am going to start doing the tubing work in the morning that will tie everything together, create a foundation for the deck, seat mounts and motor mount. The deck will ride 1/2 an inch above the top of the sponsons and I think I will raise the seat pedestles 3-4 inches further above the deck. Low profile is the theme here. It is supposed to be more of a get wet and play toy than a pontoon boat idea.





Doug...

[fun4now]

that thing is looking great, are you just winging it, or did you get a set of plans??
also did you or are you going to fill th pontoons with pore in foam ??
i'm realy wishing i had the $$ for some aluminum more and more every time i see this post.

[Doug Doty]

There is one other boat made kind of like this called a

https://www.craigcat.com

It is my inspiration in general but I hate to admit it but I am winging it otherwise. Got any suggestoins.......

[fun4now]

how much $$ you figure you will have tied up in it at finish ?? are you planing on painting it ? and what about the pore in foam, good or bad idea ??
oh also is the bottom flat ???

[Doug Doty]

I have done a budget and projected $4500.00 with everyyhing except a trailer but the boat I bought for the engine has one I might justify modifing and I haven't allowed anything for that yet. I would like to have a double jetski trailer as they would work out fine. I have kind of been thinking that If I can get it done for close to the cost of buying a new engine that could not be too bad. I scored a crappy doner boat for $2200 but it had an 2003 40hp. Mercury engine in near new condition so that was a huge help. It does have flat bottoms so foam filling would add some stability to the oil canning I might experiance but I don't want to do it right away cause I am sure there will be some modifications before I am done. That stuff is real expensive too.

[Winger Ed.]

foam filling would add some stability to the oil canning .

That foam is amazingly strong. Poured into the sponsons, it will strengthen them the way the new generation styrofoam surf boards are done. US Composites was where I got mine. They were the cheapest and most pleasant to deal with.

Saw a picture years ago of a ultra light airplane wing that was styro. covered with one layer of epoxy resin & cloth. The wing was held up on each end with a milk crate, and had 2 adults standing in the middle. There was no noticable deflection or bending of it.

If you use it, don't try to confine it as it expands. The stuff does generate some pressure, and if you try to trap/confine it as it 'blows', your sponsons will look like footballs when it stops expanding. It has to have a escape route for when you measure too much of a batch at once.

Something to check on is that you may have to have some form or fashion of foam in there as 'perma-float' before you can get it registered. As I recall; The Coast Guard requires that boats below a certain length have to be 'unsinkable'.


When I poured my hydroplane full of the 2 part stuff, I also trapped a bunch of 2 litre soda pop bottles in there with it to take up space, and hold down the amount of foam I needed for it. (save a buck where ya can)


Something else with that thing having so much engine, and the speeds it will be capable of... You're going to have some issues about, and with the center of gravity, pitch, and yaw. If it was me, I'd mount the seats in a braket that can move back & forth. And, you'll need to be able to move the engine up & down on the transom to find where it needs to be also-- or more nearly- how high it has to be to run right.

.

[Doug Doty]

I appericiate you chiming in. I really like the idea of the 2 liters when the time comes in to foam it. I would not be a big deal to make the motor mount adjustable up and down while building from scratch anyway, Have to do that !!!

Thanks,