Project Design Help Please :)

I am designing and planning to build a personal submarine using a kayak as a base and building around it. my concern : - thick pvc is what I am thinking of using as the housing, but will it be strong enough to with stand two atmospheres of pressure at 30ft underwater?. I don't think ill dive to that but I want to have that room to go deep.

​I wish to keep this as inexpensive as possible.

​any help or suggestions will be great

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Hi Kyle

Welcome aboard The MEW Forum

Gee you have picked a hard project.

I guess you have tried the following Google search?
**LINK**

The words inexpensive and safety are mutually exclusive. If you are not familiar with designing this sort of craft I suggest you seek professional help before starting. Building and using an untested design could be catastrophic.

All commercially designed and built submarines are given extensive and rigorous testing both in the dry dock and at sea before being put into service.

Regards
John

Edited By John McNamara on 24/08/2015 15:19:21

If it does not work you will save the cost of a coffin!

A 'wet' sub (i.e. no pressure vessel - pilot is in standard scuba/dive gear) is a much less risky DIY venture...

**LINK**

Depends how big an area your "thick" PVC will have to span, if its too large an area it will collapse but suitably supported may be OK depending of spacing of supports and what you call "thick"

Truly a Darwinian pursuit! I hope you have no family or dependants.

At 30 feet, the pressure is about 13 PSI (using old units). Thick PVC would make an adequate coffin but to my knowledge nobody has made a submarine from that material.

Plenty of home made mini subs are made and tested in the waters around Florida. Try searching "narco-submarine" for some ideas.

Looks like it can be done with PVC drain pipe which would have more strength than flat sheet

It sounds as if you are planning to have a pressure hull - I wouldn't think a kayak would be much good for that (shape for one thing).

Amongst numerous other issues to consider - PVC can be brittle at low temperature.

If you are actually planning a propulsion device for a SCUBA diver, things may not be so tricky.

This project sounds rather like a life support system, so people may be cautious with giving any advice.

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It was done in WW2 **LINK**

Don't think it was a pressure hull design though. Think I saw a documentary about it years ago. Perhaps it's on youtube.

Regards, Nick

I guess the overall pressure on a kayak will be 20-30 tons or more. at 30 feet deep.

Without wanting to put a damper on this idea, I strongly advise that any design is checked by a qualified engineer as failure will almost certainly have fatal results.

Personally I would go for building an ROV first to get some real experience.

Neil

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Kyle,

Before you do anything dangerous ... Please make a test tank and do some practical experiments.

Note: I have used this method [albeit only to a test depth of about six feet] on some military equipment , so I know that the principle works:

The materials are cheap: A domestic cold-water tank with a lid, and some plastic rainwater pipe. ... plus whatever bracing materials you might need

1. Fit the pipe to the tank, via an elbow, so that it rises vertically [for your test-depth, an adjacent tall-ish building would be a convenient accessory]
2. Make a watertight gasket to seal the lid [you could bolt the tank and lid together, or just put paving slabs on top]
3. Put the test item in the tank and then fix the lid.
4. Top-up with water, via the stack
5. Drain it off, dismantle the tank, and inspect the test specimen [something like one of those aluminium water bottles would be instructive]

You will probably be surprised.

MichaelG.

A cautionary tales near the end of this:

www.cia.gov/library/center-for-the-study-of-intelligence/csi-publications/csi-studies/studies/vol-58-no-4/pdfs/Tale%20of%20Two%20Submarines.pdf

Neil

Also much easier to get to sink. Maybe never coming up again. I knew some one in passing who fished for bass in shallow water and fell over while wearing waders. The weight of water in them prevented him from getting up again. He drowned.

John

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Do you intend to use it for running 'coke' for Columbian drug barons.? If so you will need good sonar fitted to stop you bashing into sunken prams and cars as you go all stealth like on your deliveries up the local canal.

Nick

I hope this project is not a way to bring illegal immigrants into the country?

Judging by the doome and gloome and dire warnings in a lot of the above posts it may actually reduce the number

Just to calm things down, I can remember seeing a TV show (USA origin) and they had 2 man submersibles but they had a moon pool in the bottom of the sub. This sub would carry 2 people and the could exit and enter the sub without any problem. The conning tower was where the person steering and diving controls were There were windows to see where you go. Electric propulsion.

Now, this would not suffer from compression as it had this moon pool which kept the water at bay by a slight over pressure in the sub. More than likely made of fibre glass/resin and they always seemed to be yellow colour. Must have been safe as there was a nubile woman in it!

The passengers/operators used no scuba gear and free dived from it. I am sure it was commercial at that time.

Clive