Re: [PSUBS-MAILIST] mounting acrylic dome in fibreglass

["Alan James" <alanjames@xtra.co.nz>]

Hi Jon,
I haven't got the Stachiwi book but have looked at the diagram on mounting
flanged domes. If I leave a portion of the flange on I will embed the 
critical
weak point of its radius in the fibreglass. The idea of keying it in with a 
tiny
bit of the flange is probably overkill. I've heard that a number of domed 
subs
have strapping over the top, I presume to stop the dome lifting off in the 
first
10 ft before water pressure holds it down. The flange idea was to counter 
the
lifting, but if its embeded in 15mm of epoxy/fiberglass it probably won't go
anywhere. I was doing an ambient sub, but your posting of the plastic 
submarine
got me rethinking the fibreglass issue.
regards Alan.
----- Original Message ----- 
From: "Jon Wallace" <jonw@psubs.org>
To: <personal_submersibles@psubs.org>
Sent: Friday, May 15, 2009 12:27 AM
Subject: Re: [PSUBS-MAILIST] mounting acrylic dome in fibreglass


> Hi Alan,
>
> If by "...leaving a small portion of the flange on..." you are talking 
> about a flange on the acrylic dome as a result of manufacturing, check 
> your Stachiw book for the requirements necessary to use such a flange.  If 
> it doesn't meet certain specs, leaving it intact can weaken the dome when 
> it is under pressure.
>
> Jon
>
>
> Alan James wrote:
> > Hi guys,
> > I'm building a small epoxy/fiberglass 1 atmosphere sub and are wanting to 
> > embed an acrylic dome in a block of epoxy resin/fiberglass. The dome and 
> > fiberglass ring will comprise my hatch. The dome is 25mm thick and 500mm 
> > OD. I'm envisaging I will embed it half way into a ring that is 50mm wide 
> > and 25mm high. The ring has a theoretical crush depth of 4000ft(1,768psi) 
> > The dome (if it was cast wich its not) would have a crush depth of 
> > 3233ft. I have the option of leaving a small portion of the flange on to 
> > key it into the fibreglass. The epoxy fibreglass is about 25% stronger 
> > than the acrylic. I'm designing everything with a crush depth of 2000ft + 
> > but will be happy with a 200ft operating depth.
> > Any thoughts -reservations - comments would be appreciated.
> > Thanks, regards Alan
>
>
>
>
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