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Re: [PSUBS-MAILIST] Dome Calculations

To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Dome Calculations
From: irox <irox@ix.netcom.com>
Date: Wed, 27 Aug 2008 03:40:26 -0400 (EDT)
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Reply-to: personal_submersibles@psubs.org
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Hi Clive,

the full title is:
Handbook on Acrylics of Submersibles, Hyperbaric Chambers and Aquaria
by Dr. Jerry D. Stachiw

More about the book here:
http://www.hydroports.com/Handbook_on_Viewports.htm

And amazon.com link:
http://www.amazon.com/Handbook-Acrylics-Submersibles-Hyperbaric-Chambers/dp/1930536151/ref=sr_1_2?ie=UTF8&s=books&qid=1219822770&sr=8-2

It might seem kind of pricey, but it's well worth it.

Cheers,
  Ian.

-----Original Message-----
>From: Clive Wood <pirate@arach.net.au>
>Sent: Aug 27, 2008 1:33 AM
>To: personal_submersibles@psubs.org
>Subject: Re: [PSUBS-MAILIST] Dome Calculations
>
>Gday Ian.
>
>Could you please tell me the full name of Stachiew's book I have been having 
>trouble finding one for sale.
>
>Thanks and Regards, Clive Wood.
>----- Original Message ----- 
>From: "irox" <irox@ix.netcom.com>
>To: <personal_submersibles@psubs.org>
>Sent: Tuesday, August 26, 2008 11:13 PM
>Subject: Re: [PSUBS-MAILIST] Dome Calculations
>
>
>>
>> Hi James,
>>
>> I'm also planning on using sectional spherical viewport domes.
>> While I've not built any, I'll share what I've found:
>>
>> 1) You could use a neoprene gasket instead of the sealant.
>>
>> Also, in the cross-section, where the viewport, the retaining ring
>> and the frame meet, there is a little triangle shaped void, you could
>> place an O-ring in there to stop water entering the viewport frame
>> and retain the dome.
>>
>> Alternatively, the "flat gasket" you've currently drawn (between
>> the viewport and retaining ring) could be extended so that it's
>> sandwiched between the frame and retaining ring as well as
>> sandwiched between the viewport and retaining.  This would prevent
>> water entering the frame.  Figure 11.76 on page 524 of the Stachiw
>> book has diagrams of both implementations.
>>
>>
>> 2) Yes, you should have an over hang so the inside viewport is no
>> where near the edge of the fame.  The view port will compress
>> slight under operating conditions, fattening the base a little.
>> If the base moves over the edge, then there exists the conditions
>> for notch cracking to start, which means replacing the viewport.
>> In non-normal operating conditions, i.e. the viewport is failing,
>> the base will get much bigger, if it goes over the edge, then
>> notch cracking will make the dome fail much quicker.
>>
>> I think there is a hint at how much over hang to have in the
>> Stachiw book, but I can't find it just now.
>>
>> 3) I've had a hard time finding information about how to design
>> the viewport frame/housing.  Most are designed thick so that the
>> pressure hull moving as it dives deeper will not deform the
>> viewport frame/housing/seat.  If the frame deforms, then the
>> Acrylic will not be against a flat surface and all sorts of other
>> problems will come into effect from that.
>>
>> With a sectional spherical viewport the side walls of the
>> frame/housing/seat will be under pressure as the force pressing
>> on the dome presses the flat surfaces of the dome against the
>> frame.  From looking at examples in the Stachiw book, all the
>> frame walls seems to be at last the same thickness of the
>> Acrylic, in some case 2x or 3x.
>>
>>
>> As for kicking the dome out in an emergency, my guts say that
>> isn't going to work so easily.  Alec Smythe had a hydrolic
>> piston system for opening his dome in an emergency.  Maybe
>> make the dome a hatch, so that the frame swings open and things
>> like retaining rings, O-rings, sealant and gaskets won't be
>> an issue.  Will the dome be above the water when it's getting
>> kicked off?
>>
>> I know at least one person who has/had a sub where the dome
>> didn't have any retaining device other than water pressure.
>>
>> Cheers,
>>  Ian.
>>
>> -----Original Message-----
>>>From: James Frankland <james@guernseysubmarine.com>
>>>Sent: Aug 26, 2008 10:02 AM
>>>To: personal_submersibles@psubs.org
>>>Subject: [PSUBS-MAILIST] Dome Calculations
>>>
>>>Hello Everyone
>>>
>>>Progress on my sub has been slow recently, but i have managed to get a few 
>>>things done including a change to the possible design for the removable 
>>>front dome mounting system that i am adding instead of the 15" flat port 
>>>specified on the plans.
>>>
>>>I have made some changes to my original design as a result of reading 
>>>Staichows book and with some advice from members of the group.
>>>
>>>http://www.guernseysubmarine.com/index_files/Page12229.htm
>>>
>>>I would really appreciate if you could take the time to have a look and 
>>>let me know what you think of this idea.
>>>
>>>Points to note\questions.
>>>
>>>1.  The "O" ring groove has gone and been replaced with a 1mm bead of 
>>>sikaflex sealant.  Bearing in mind the idea of this design change is so 
>>>the dome can come out in an emergency, do you think this amount of sealant 
>>>will stick it permenantly and prevent removal, even with a good kick from 
>>>the inside?  Could make it thinner, 0.5mm?
>>>
>>>2.  The inside diameter of the ring meets exactly the inside diameter of 
>>>the dome.  (The 32mm bit on the second picture).  Should it be a bit 
>>>larger?  35mm?
>>>
>>>3.  I do not have the ability to do FEA on this ring, so based on the 
>>>"rule of thumb" that says you should replace the amount of material you 
>>>remove, i have calculated volumes of the ring and the removed piece.  The 
>>>figures are shown at the bottom of the page.  The endcaps are spun and 
>>>thicker than specified on the plans.  13mm at the rims ranging to about 
>>>10mm at the centre.  So, exact calculations for volume of this are 
>>>difficult.  If based on the worst case scenario of 13mm all over, the 
>>>volume of weld in ring does not cover the "rule of thumb".  Should i add 
>>>an extra 10mm to the thickness of the ring, bearing in mind the endcaps 
>>>are already quite a bit thicker than needed.
>>>
>>>Does that make sense?  I've not done one of these before so i think its 
>>>better to ask silly questions now and avoid mistakes or accidents in the 
>>>future.
>>>
>>>Again, this is still just an idea at this stage and could all change, 
>>>depending on how things turn out.
>>>
>>>I appreciate any advice, good or bad.
>>>
>>>Regards
>>>James
>>>
>>>
>>>
>>>
>>
>>
>>
>>
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>
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>
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