Re: Re:AIPs,WaterJets and Propulsion

["Sean Walinga" <swalinga@telusplanet.net>]

>Mike here,from Malaysia,
>The design I've been working on for a submersible is in the shape of a
>giant manta ray, using a waterjet propulsion system. The intake in
>front and the propulsion from what would be its tail. The air to water
>ratio you mentioned could be taken care of by a vacuum created to
>remove CO2 at the same time and replacing the air in the sub by using
>two large pressurized tanks, one pure oxygen, the other plain
>compressed air (like a regular scuba tank), and both holding about 6
>hours worth. Water flow can also be used for steering with a small
>trolling motor to get water flow started when you start up your dive.
>I noticed a picture of a deep submersible(3000+ ft.) which used
>pressure banding to hold a clear bow dome in place and to seal the
>whole thing to the metal hull. Once I can scan the picture into my
>computer, I'll try to send it as an attachment.

Hi Mike,
It's an interesting thought to use the CO2 for the air portion of the waterjet vacuum. It would be difficult to proportion it properly though considering the amount of air needed for the waterjet changes with the speed. How would you regulate it to match the air needs of the waterjet? My intuition tells me that you would end up using more air than necessary due to the waterjet need...

I have considered the MantaRay (or Stingray) for a p-sub design previously but abandoned it due to the pressure limitations. The design itself creates a problem when you focus on the point between the main body and the wings. It is a weak spot unless you plan to have the main hull as the body and the wings as an ambient pressure attachment. If this were the case, why would you attach them? It increases on parasitic and surface drag for no better reason than it looks good. The wings themselves would increase stability on the surface though...   Anyhow, this is why I didn't go this route. I would be interested to find out why you did and also what you plan to do to overcome the challenges.

Don't bother trying to send the picture unless you send it directly. The listserve has a size limit of 40K per message and some of the members have ISP's that don't support attachments. They would end up sending you nasty messages requesting that you don't do that again. :) 

I think the p-sub you mention is the DeepFlight. It has an acrylic dome with a metal flange. Some of the other members are better suited to discuss these things so I'll back out of this one...

One more thing is the trolling motor used to prime the waterjet? If using a trolling motor, why not just use it for propulsion? If you go to the difficulty of getting a trolling motor working at a depth of more than 30ft, it should just be used. The waterjet shouldn't need to be primed anyways due to the impellor turning regardless of the vacuum. The vacuum simply increases the power of the jet. 

These are my thoughts anyhow. :)
ttfn
Sean