Re: [PSUBS-MAILIST] Fiberglass Hull

Doug,

I'm not qualified to answere your questions about fiberglass composite sub hulls under external pressure, but here is a interesting thred about just that sort of thing. Here is the link and a small quote from the discussion that has the most meat in it.

http://www.eng-tips.com/viewthread.cfm?qid=174497&page=1

"Spend some time looking through ASME III (Unfired Pressure Vessels) for vessels under external pressure. And keep in mind that if you intend to operate at 100 ft (~45 psi) that you'll want a hefty margin against any kind of pressure boundary buckling failure. Think in terms of emergency recovery time from a depth overshoot if you experience horizontal control plane malfunction while descending at some speed and down angle when nearly at your maximum operating depth.

I may be able to find a more specific ASME reference for you, but for a number of reasons I don't think I can provide any hints as regards a design collapse depth, so you're on your own there.

Norm

arto (Mechanical)

12 Jan 07 9:46

also look under ASME PVHO (Human occupancy) & Sec. X {fiber reinforced plastic) pressure vessel codes"

end quote

In the past I saw a web site for a deep diving live aboard submarine project called the Neptune. They were working on a design for a carbon fiber pressure hull that they claimed could be used down to 6000 meters. The web site was www.neptunesubmarines.com but it's a dead link now. I was put onto this site originally by a web site for the Perendev magnetic motor. At one time I thought it might be a great motor for subs in general but there is some serious greed problems with the owner of the company. Neptune Submarines were wanting to put the Perendev magnetic motor in there live aboard submarine to replace a nuclear type power source. Maybe someone here knows what happened to this Neptune Submarines group out of Switzerland? Here is a pic of there submarine design.

http://img224.imageshack.us/img224/7608/24243158bk0.jpg

Regards

Brent

From: djackson99@aol.com
Reply-To: personal_submersibles@psubs.org
To: personal_submersibles@psubs.org
Subject: [PSUBS-MAILIST] Fiberglass Hull
Date: Fri, 26 Jan 2007 00:35:40 -0500

I know it's an old topic but I have mostly ignored the previous post regarding fiberglass because I never thought I was going to give it a second thought. ...wrong again.

1) Did anyone ever come up with a way to calculate even a ball-park working depth given all, or at lease some of the variables for fiberglass construction? If so can you point me in that direction?

2) I know that the externally loaded working psi for a non-reinforced cylinder is lower than it's internal working psi. That makes even more scene to me when thinking about the alignment and tensile strength of glass or carbon fibers compared to their compression strength. However it seems that there would be a ratio that could be used to estimate the reduction in loading ability. Would that be true? For example if pipe section is rated for 1000psi, could it's external load psi rating be stated as x% lower, say 20% lower, based on the type of material?

Thanks --Doug J

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