Requirement for a small thruster?

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Hi there

First post after browsing a while. So many intelligent people on here, so having bigged up your talents, lets see what your thoughts are.

I'm developing a underwater craft that will carry one or two people. Max depth it will go is about 5 metres. Weight estimated to be about 80kg or so.

I need to get a propulsion system into it, and am learning all the time. I know of current models (not brands) that use a propulsion system that is simply an underwater motor with prop, which has an average lifespan of about a year.

I've been looking at lots of different options - willdo in the Netherlands, for example, but the issue with their system is that its max running time is 20 minutes, and I need something that could, potentially, run for hours although in theory 30-40 mins would be the max it would run in one go.

Also been looking at converting a powerful bilge pump with the output converter to a prop, but early days on this line.

Ideally it would run off a 12v supply.

I know there are some items as SeaDoo (the divers aids which pull you through the water) and this is very similar to what I'm looking for in terms of a propulsion unit, but would be grateful if you could advise manufacturers who could support this?

Anyone any websites, or people I can talk to who would be able to help. Max speed of the craft underwater will be about 2 knots, so it's more reliability I'm looking for and good use of power.

Virtually all thrusters seem to be much larger than I need, so am I actually going about this the wrong way and should be looking for an underwater motor supplier, given the limited pressure on the unit, but the requirement for use in sea water?

Your thoughts would be helpful, and if you have technical question, I'll do my best to answer them, but I'm learning about this all the time...

Many thanks

Andy

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Blimey - no-one any ideas at all?

Andy

[Ratch]

You have a couple of starting points 80kg and two people. 80kg will tell you what sort of power capacity you can archive. Li-on will give you one of the best weight to power ratios but will cost you $. Now you need to find out what size motor you will need to get 2 knots that along with power available will soon tell you if your project is even possible. I think for starters your 12v will end up to be 24, 36 or even better 48v.

Some ideas of various motors available google:
Golf buggy motors
scooter motors
PM motors
EV motors

Looking from another angle I would be curious how compressed air would push this craft along esp as the exhaust can be potentially used as an additional air supply. I suspect that it will not have much endurance.