[PSUBS-MAILIST] Foam preperation

Fri Jun 28 10:53:18 EDT 2019

I recently obtained a quote on some machined syntactic components, because I needed to make a custom float assembly in which to embed a ring magnet in order to operate a level sensing instrument inside a corrosive fluid tank subject to 15,000 psi pressure. Granted, the parts were small, but I was still surprised that the cost was reasonable. Perhaps basic blocks wouldn't be too out of reach - particularly at the densities required at PSub depths? Depends how much you need obviously, but it might be worth an inquiry.

Engineered Syntactic Systems:

https://esyntactic.com/products-solutions/syntactic-buoyancy-materials/

Sean

-------- Original Message --------
On Jun 28, 2019, 06:06, Cliff Redus via Personal_Submersibles wrote:

> They don't say much about the manufacturing process.  This could contain micropheres as a filler.  I tend to take Alan's point on this from a safety perspective.
>
> Don't get me wrong, I would love to have a low cost alternative to syntactic foam.  It just that this is such a safety critical item on a manned submersible.  Lets say we use a non syntactic foam for buoyancy, get the boat neutral by flooding MBT and start the dive over a deep trench. Captain has a heart attach because it just so beautiful out the viewport.  With any shrinkage at all of the foam, the boat would go slightly negative and boat would eventually crush unless their were automatic systems on board.  I am just saying if it were my boat, I would do some testing before putting my life and the life in the hands of a product that was not specifically designed for this application or unless I confirmed that it would not shrink by testing.   What you are planning on using may be perfectly fine.  It just seems prudent to do some testing.
>
> Best Regards
>
> Cliff
>
> On Thursday, June 27, 2019, 11:19:31 PM CDT, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
> https://www.generalplastics.com/case-applications/subsea-foam-equipped-rovs-dive-deeper
>
> --- personal_submersibles at psubs.org wrote:
>
> From: Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] Foam preperation
> Date: Fri, 28 Jun 2019 03:16:58 +0000 (UTC)
>
> This could work.  Would need the pressure gauge to confirm that water did not leak out on return to the surface.  It is probably easier just to cast a sample and send it to Hank to video at depth with a ruler behind it.
>
> To get a 16 lbf/ft^3 specific volume at one atm, the foam would have to have over 70% air trapped in the foam at the surface.  I just can't see how this air in not going to collapse at depth to some degree.
>
> What you need is syntactic foam which was designed for this application.  If the foam shrinks during the descent, you are going to have to use your MBT to compensate.
>
> I think you would do better to make a simplified syntactic foam with off the shelf polyester resin plus 3M glass micro-spheres as a filler. Without macorospheres, I think the best specific weight you can expect is 30-40 lbf/ft^3 but at lease you would be assured that this buoyancy  was depth independent because the air filled glass microspheres would be keeping the from collapsing.
>
> Best Regards
>
> Cliff
>
> On Thursday, June 27, 2019, 09:32:28 PM CDT, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
> Maybe I could pour the foam into a large diameter pipe of say 5" x 10" long,  close the pipe up with a bell fitting , plumb in a high pressure check valve, but before that put in a tee with a ball valve.   As the pipe descends water comes in through the check valve as the foam ( allegedly) shrinks in volume.  Then, when it is brought up the check valve keeps the pressure at the max depth pressure (600' depth) .  When the pipe is at the surface it would still have the pressure of say 300psi.  Then you could open the ball valve into a container and measure the amount of seawater that was drawn in .  Maybe put a pressure gauge on there too.
>
> Brian
>
> --- personal_submersibles at psubs.org wrote:
>
> From: Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org>
> To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] Foam preperation
> Date: Thu, 27 Jun 2019 18:23:42 -0700
>
> Cliff,    There is probably a way I can determine if it shrinks or not at depth.   I'm sure some clever person on this list could devise such a way .
>
> Brian
>
> --- personal_submersibles at psubs.org wrote:
>
> From: Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] Foam preperation
> Date: Thu, 27 Jun 2019 18:17:45 -0500
>
> Brian this would only be a good test if you had a camera on it with a ruler.  I believe it would compress significantly then expand when you took back to surface.  Without microspheres and or macro spheres, there is just nothing to keep the entrained air from shrinking .  The pressure rating you need is what pressure you can take without any change in volume.
>
> Cliff
>
> Sent from my iPhone
>
> On Jun 27, 2019, at 5:01 PM, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>> I think what I might just do is just go out in my sailboat , off Pt. Magu,  and drop a test plug down to 600' , bring it back up and check it out.  Need to go out for a sail anyway !
>>
>> Brian
>>
>> --- personal_submersibles at psubs.org wrote:
>>
>> From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
>> To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
>> Subject: Re: [PSUBS-MAILIST] Foam preperation
>> Date: Fri, 28 Jun 2019 08:41:55 +1200
>>
>> Brian,
>> If I had $3million spare I wouldn't spend it on syntactic foam.
>> The danger is that if you were descending you might not know that you
>> were becoming negatively buoyant until you tried to stop. Then when
>> you tried to counter by filling the ballast tanks with air; because of the compression
>> of the air at depth this might be a slow process.
>> Bottom line is not to dive the sub in depths that are beyond your maximum
>> dive depth till you are confident the foam isn't compressing.
>> Alan
>>
>> On 28/06/2019, at 7:41 AM, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>>> Alan,       I don't have 3 million dollars.    In any event I only need it to go to 300 psi, theoretically ,   I also have about 1000 cu ft of air on board and could easily fill my ballast many times over even if the foam were to shrink.  I don't think the foam has an elastic property to it.
>>>
>>> Brian
>>>
>>> --- personal_submersibles at psubs.org wrote:
>>>
>>> From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
>>> To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
>>> Subject: Re: [PSUBS-MAILIST] Foam preperation
>>> Date: Fri, 28 Jun 2019 07:33:33 +1200
>>>
>>> Brian,
>>> as Cliff says it may have a volumetric change under pressure that leaves
>>> you negatively buoyant. I am not sure how you would test this in a
>>> pressure chamber.
>>> As an example, a soccer ball could take a lot of pressure & look perfectly
>>> fine after a pressure test even though it might have been reduced to a
>>> fraction of its original size in the process.
>>> I was told that Alvin's syntactic foam & testing process cost $3 million.
>>> They put it together in segments after testing each individual segment.
>>> It might be perfectly OK though...
>>> Alan
>>>
>>> On 28/06/2019, at 7:03 AM, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>>
>>>> I have a pressure gauge guy who does oil industry work that I think has a small chamber where I could test a plug of foam.
>>>>
>>>> Brian
>>>>
>>>> --- personal_submersibles at psubs.org wrote:
>>>>
>>>> From: Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org>
>>>> To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
>>>> Subject: Re: [PSUBS-MAILIST] Foam preperation
>>>> Date: Thu, 27 Jun 2019 11:37:26 -0700
>>>>
>>>> Cliff,
>>>>               It's rated for 580 psi.
>>>>
>>>> Brian
>>>> --- personal_submersibles at psubs.org wrote:
>>>>
>>>> From: Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org>
>>>> To: Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org>
>>>> Subject: Re: [PSUBS-MAILIST] Foam preperation
>>>> Date: Thu, 27 Jun 2019 15:55:01 +0000 (UTC)
>>>>
>>>> Brian, this is not syntactic foam.  It's made for marine service but not for deep submergence.  It is really for surface buoyancy. I would not use this if you are relying on it for buoyancy at depth.   It is the macro-spheres and microspheres in syntactic foam that prevent it compression at depth.  I don't think this foam has either.
>>>>
>>>> Best Regards
>>>>
>>>> Cliff
>>>>
>>>> On Thursday, June 27, 2019, 10:45:29 AM CDT, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>>>
>>>> Clifff,   Here is the foam, it's the most dense foam , the 16lbs / cu ft
>>>>
>>>> http://www.uscomposites.com/foam.html
>>>>
>>>> suppose to be good to 580 psi
>>>>
>>>> Brian
>>>>
>>>> --- personal_submersibles at psubs.org wrote:
>>>>
>>>> From: Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org>
>>>> To: Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org>
>>>> Subject: Re: [PSUBS-MAILIST] Foam preperation
>>>> Date: Thu, 27 Jun 2019 14:29:12 +0000 (UTC)
>>>>
>>>> Brian, I have been tied up and have not had a chance to follow this thread but I wanted to make sure you understand that unless this pour-able 2 part foam has a filler like 3-M's glass micro-spheres or some kind of incompressible macrosphere, then while the foam may appear rigid, it would compress when subjected to deep water and thus your buoyancy would be reduced.   I don't think this is a replacement for syntactic foam if that is what you are doing.  Can you send a link to the foam you are using?
>>>>
>>>> Best Regards
>>>>
>>>> On Wednesday, June 26, 2019, 10:30:48 PM CDT, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>>>
>>>> Hi everybody,
>>>>                                    I poured a small test piece of that 16 lb foam, man that stuff  gets as hard as a rock !  very dense , and very light.   This pouring of the foam is not going to be as straight forward as I thought,  The barrier to contain the foam is working out good, I'm just using wood and thin  1/8" luan ,  then I'm covering that with 4 mil flexible plastic ( heavy garbage type bag)  so the foam won't stick to it.  But I'm worried that any little gaps I have and the liquid foam might run out the bottom of those areas before it starts foaming, so I'm cramming big blankets ( cheap moving blankets from harbor freight)  in tight to contain any foam.  That way I can get the cavity that I'm trying to fill completely maxed out.  Waiting for an 80 + degree day  .
>>>>
>>>> Brian
>>>>
>>>> --- personal_submersibles at psubs.org wrote:
>>>>
>>>> From: Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org>
>>>> To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
>>>> Subject: Re: [PSUBS-MAILIST] Foam preperation
>>>> Date: Mon, 24 Jun 2019 16:12:46 -0700
>>>>
>>>> My first batch of foam cam today !  yay !   two five gallon pails, A and B,  should be interesting !
>>>>
>>>> Brian
>>>>
>>>> --- personal_submersibles at psubs.org wrote:
>>>>
>>>> From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
>>>> To: Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org>
>>>> Subject: Re: [PSUBS-MAILIST] Foam preperation
>>>> Date: Fri, 21 Jun 2019 17:47:56 +0000 (UTC)
>>>>
>>>> Brian,
>>>> Did you find foam to fill the void?
>>>> Hank
>>>>
>>>> On Thursday, June 20, 2019, 8:30:55 PM MDT, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>>>
>>>> Kind of unnerving drilling holes in my boat !
>>>>
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