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RE: [PSUBS-MAILIST] K350 Main Tanks



Hi James,
 
I hope you're better. Air compensation vs.. oil is a much hashed thread, with lots in the archives, and the bottom line is that they both work fine. However, in Snoopy's case the implementation of air compensation was troublesome because the air comp line and cables were all routed through the inboard end of the thruster shafts. That is a really small diameter, and as a result the cables were way too thin and would heat up like a toaster. In addition the sealing method was very iffy, just a compressed rubber washer with a number of holes poked in it. The poor sealing meant internal cabin pressure buildup, and should the compensation ever fail, only a compressed rubber washer stood between the cabin and ambient pressure water outside. With the current arrangement, the cables can be thick as pencils and are potted in epoxy, so there's very little to go wrong and no moving parts.
 
Coincidentally, I am taking Snoopy out on a two day dive trip this evening.  If all the new mods work as intended, will be posting photos and videos shortly after my return. She is utterly different these days to what you see on the site or the PSUBS projects page on any of the videos.
 
 
Thanks,

Alec
 
 


From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of James Frankland
Sent: Thursday, September 08, 2011 11:24 AM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] K350 Main Tanks

Hi Alec,
 
Appologes for the late reply, ive been ill. 
 
>1) It looks like you have a flat bulkhead closing off the end of each tank that faces the hull. If that is so,
 
Yes, that is the case but its a thinner piece as it is supposed to be cut off.  I seem to remember you saying somewhere before you thought the strap on tanks were a pain.  I think i'm too late to change it now, might just have to lump it.
 
>2) Use that lip to bolt on a flat cover underneath, and put large diameter pipe downward about a foot. >You can easily attach the down pipe with nothing but a hole saw and nylon bathtub drain fittings. 
 
I think this is a good idea.  Im not sure it will work for the front tank as i have to accomodate the large dome, but for the rear its a distinct possibility.  I wish i'de gone for saddle tanks to be honest like Nemo, but its too late now and i do like the way these look at least.
 
Just out of interest.  I watched the psubs video of the Snoopy build last night.  Ive seen it before but its much more relevant to me now ive done most of the stages.  Anyway, Dale talks about his pressure compensated motor arrangement.  A water feed from the depth gauge line to one side of a diaphram pressure regulator, the other to hp air into the motor.  Bleeds back through itself.  Sounds like a good idea.  Why did you take that off and go for an oil compensated system? 
 
Im going to go for oil, but im just curious.
 
Regards
James
 
 
Both these ideas are part of the design for my next boat, based on K-250 experiences.
 
 
Thanks,

Alec


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From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of James Frankland
Sent: Tuesday, September 06, 2011 12:23 PM
To: personal_submersibles@psubs.org
Subject: [PSUBS-MAILIST] K350 Main Tanks

Hi All,
 
My main tanks are nearly complete.  Ive had them professionally made.  Most of the expence is in the making of the foam plug and then the mould, which ive taken on the chin.
 
Now i have a mould, i can get the company to make a set at any time, so if anyone would like me to get tanks made up for them, contact me off list and i'll see how much it would cost plus postage etc.
 
 
Kind Regards
James