Personal Submarine Build

Part of the deck side finished

Looks super cool. Great work mr.mod! Interesting about the exhaust drain as well, I would've never thought about the fact that water would enter the exhaust while the engine wasn't running.

Continuing the thought, don't know if it applies to engines, but with guns, when you are underwater, and the barrel is full, it fires just fine.  But if you have the end of the barrel in the water, it will fire just fine until it hits the water then the barrel will explode.

IDK if the same principle applies, might want to think about it though.

The exhaust should work even a foot or two under water as long as the engine keeps running, but for the most part, only waves would wash over it occasionally. I don't think it will be too much of an issue. I've been in deep water with a tractor and the exhaust just bubbles up through the water.

There's a whole bunch of issues to sort out with this thing. Fairly soon I need to mock up a section of the hull with 1/2" electrical conduit to see if 30" diameter propane tanks are big enough to use.

Looking good. Did you ever say what you were gonna use for ballast to prevent her from rolling? Or will that be an issue?

Wheel weights should be easy to find.
I have a buddy who works at a dealership he can get me a 5 gallon buckets worth of weights in a few weeks.

Only downside, not all of them are lead.

Thanks. Yeah there should need to be quite a bit of lead added to keep the submarine down far enough in the water that it will work. That will be attached on the bottom to keep the submarine upright. So far I have between 300 and 400 lbs of lead (mostly wheel weights) saved. A wheel weight filled 5 gallon pail is about 100 lbs (roughly).

Any object lighter than the water it displaces will float while any object heavier will sink. Submarines don't really change how much they weigh when they let water into the ballast tanks to sink. A better way to think about it is that they vary their displacement. Depending on the size of the finished machine, it's going to have to weigh between 2500 and 3500 lbs I think.

Forward dive planes. Still needs the linkage rod under the deck. These will be movable on the model.


Forward deck is almost finished


Fake hatch hinge. Could have a rod or pin across it.


One more side to add to the aft deck, then I need to start working on the tail section, propeller, and rudder.

Change their density you mean? That'd make more sense(I think).

Planning on keeping the wheel weights all in separate pieces? I'd cast them into bigger chunks myself. Your project though lol. Loving it!

Most of the weights I think will be melted down and poured into spaces in the skids on the bottom.

When are you going to start the real one?

Who knows to be honest. Once I make sure what size hull will work I can try to get some propane tanks. Some are about 30" diameter and some are 35" I think. I was hoping to use the 30" ones.

Also I need a bigger space cleared out at the garage and I have a crane to fix up before I start the actual build.

I hope you are being safe. Read a lot and test it well.

Oh yeah, being in a steel can 100' under water is kinda risky, don't want to cut corners lol. Thank you.

I am working with a retired engineer on the project but he didn't specialize in pressure vessels. I would like to talk to someone who does if I can find someone. I know about what to do and not to do as far as building the hull. But there are certain things that I might not know. One thing I read is that your not supposed to place a stiffening ring over a circumferential weld in the hull. That is, the internal rings welded inside the hull shouldn't be over a place where you welded two lengths of the hull together. I need to know the best ways to weld fittings through the hull and that sort of thing. Which piece should be over which sometimes makes a difference in strength.

When I get ready to build the actual hull, I will be sure to find out the best way it should be done. I don't want to guess work something like this.

I'm shooting for a max working depth of 100' But with calculated crush depth at far deeper. Maybe 300' or more. Realistically, I won't need to go below 50' very often. There's not much point.

Yeah I agree. No point in going deeper than 50ft. its kinda risky. That would be really scary if it implodes do make sure you make is solid.

If it implodes I'll be killed instantly lol. So it's a good idea to build it correctly. The good thing is, people have been working on pressure vessel design for over 100 years. So all the info is out there, just need to find out as much as possible and stick to proven ideas.

Hull strength depends on the material used, thickness of the hull, type of stiffening rings used and how far apart they are spaced, diameter of the hull. There's a bunch of stuff. Also any penetration of the hull weakens that area at least somewhat. So things like pipes being welded through or a lever or shaft sticking through, that effects it a bit. The hull thickness can be doubled up around larger weak points. The weakest area would be the part where the hatch and tower goes on. The stiffening rings can't go all the way around there and it's a wide cross section. On other small submarines I have seen, they use a 3/4 or so stiffening ring there with a cross piece joining it to adjacent rings. Here's a pic of what I mean.



The opening marked in blue. The stiffening rings marked in red.

Honestly, since you want to go down 100' I would spend the money and have your design professionally engineered. The pressure and force on the outside of that hull is many times what the atmospheric pressure would be inside the hull. If the hull isn't designed and welded correctly the hull will just crush like a tin can. I would definitely get started by reading up on statics and forces in equilibrium and also ship welding practices like you have been. I would also tour as many ships and submarines as you can and take notes and pictures along the way.

Yeah I'm researching pressure vessels now.

Building the tail section




Tail section complete. The rod is for the rudder which I'm doing next.






Getting closer to paint

Mocking up the rudder


1/2" electrical conduit rings for the full scale skeleton mock up. So far only two done, I'll need about four more this size. These are about 30" diameter.

Finally starting some stuff on the real deal eh? Its getting exiting..

Yeah I'll make a mock up with the 1/2" pipes and that way I can make sure I will have enough room inside with the size propane tanks I want to use. I have to drive a couple hours to a place where I can buy them I think, so no point in going through a lot of trouble, driving, loading, and paying for the wrong size tanks.

Originally, I thought 30" diameter 250 gallon tanks would do the job. But I forgot to factor in the space the internal stiffening rings would take up inside the boat. With a 2" wide ring, that's 4" diameter taken up inside, leaving me with only 26". I marked that out on some cardboard and right away I could see, that's wayyyyy too small to fit anything in there, let alone bolt things together.

So now, the new plan is to use larger tanks of about 35-37" diameter. With 1.5"-2" stiffening rings, that gives me a good 31"+ to work with inside.

There are other things taking up space inside too, like a floor a couple inches off the bottom to keep you from sitting in the bilge water, pipes, and levers for dive planes and rudder. Some pipes might be able to go under the floor.

The final pieces of the deck going into place




Welding should be finished on the entire deck


Linkage rod from rudder to thru hull and exhaust system


Underside of tail section, showing where the rudder linkage rod attaches


Rudder completed

Started welding on saddle tanks. On the real one these will be maybe somewhere around 4-7 gallons each at the mid point in the submarine.
Changing how much water is in these tanks won't effect the balance or trim of the sub, so fine adjustments of buoyancy can be made without
having to re-adjust trim every time.  


Other things which need to be on the center line is the 200lb safety drop weight and preferably the fuel tanks. Although
the fuel may need to be in two separate tanks under the sub forward and aft.


Aft dive planes welded on. These are in a fixed position. Also in this pic the aft main ballast tank vent can be seen, that's the small pipe that sticks up.
On the real one there will be a valve and a linkage rod attached, just like I did with the fwd dive planes and rudder.

Go to 6:00. In this weeks episode of handyman corner red green builds a one-man sub!

Not sure if a water heater is the best building material lol

slow progress on the submarine model. Forward and aft deck painted.
Still one end cap on one of the saddle tanks to weld on and the two port holes in the conning tower.


The laughing sawfish sticker was peeling off my jeep so I taped it on here to see how it would look.
Once this model is done, then it's back to work on the full size mock up again to double check that 35" or so diameter
will work for the hull. Then, I can actually go buy some tanks.

Nice update! I had forgotten about the sub!