[PSUBS-MAILIST] Foam preperation

Tue Jul 9 02:45:16 EDT 2019

Brian,
coating it with epoxy resin or fibreglass & epoxy resin might be a solution.
But as I understand it you just want to squirt it in & fill up a gap.
Alan

> On 9/07/2019, at 6:17 PM, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Alan,
>              Yes it's puzzling the mechanism at work allowing it to take on water.  It could be that the small bubbles of foam that make up the matrix of the foam itself are simply not strong enough to handle the water pressure.  But it's interesting that it can take a rated pressure ( parallel applied pressure) and not be crushed but then on the other hand will absorb water.  From the look of it you would never think that water would penetrate it, the outside of the foam seems nonporous.  Might be instructive looking at it under a microscope.  
> 
> 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: Tue, 9 Jul 2019 16:57:52 +1200
> 
> Brian,
> I am wondering how it absorbed water, seeing it's a marine product.
> Do you think there may have been a break down on a microscopic level through
> the water being forced in under pressure.
> Anyway, good that you got a result. Imagine if it had absorbed water more slowly
> so that it wasn't detectable in the short time that you tested it.
> Alan
> 
> On 9/07/2019, at 1:43 PM, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Bad news,  the test piece that I dropped down to 900'  , it didn't crush , but it absorbed water.  So it lost a lot of its buoyancy.   
> 
> 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: Fri, 28 Jun 2019 16:15:09 -0700
> 
> Alan,              I've done one small test piece so far and it did give off some heat.  I'm planning on doing a larger piece that I'm going to drop in the ocean, it will be interesting to see how that goes.  I'm more inclined to pour larger amounts for a couple of reasons, first I think you get a better and more accurate mix of the A and B, and also where I'm pouring into my cavities I don't want to inadvertently seal off areas that I will not be able to get to to complete the pour.  So I'd rather error on over pouring a bit so I have foam pushing out the vent holes.  
> 
> 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: Sat, 29 Jun 2019 09:18:40 +1200
> 
> All,
> as we are talking about testing this for General Psubs use I'll elaborate
> on something I mentioned earlier.
> In the product specifications below it mentions that in the setting of this product
> the temperature is critical, & that temperatures below 75 degrees F will make a
> denser product. One would assume that temperatures above 75 F would make
> a less dense & hence weaker product. 
> With 2 part chemical reactions there is generally a heat produced & this is 
> exponentially greater the thicker the pour. I used to use casting resins for art
> & they would get very hot on thick casts.
> If this were the case then filling any large voids in one pour may cause the
> centre of the material to be a lot weaker than the outside.
> To check this we could ask the rep about thick pours, do a thick pour & cut it
> in cross section to see if it is less dense in the middle or stick a heat probe in
> the middle of the pour to check for an increased temperature.
> All expansion rates and times given are temperature critical. Temperatures below 75 degrees F will lower the expansion rate therefore requiring more foam. Ideal working temperature is 75 to 80 degrees F or above.
> Accurate measuring of these products is extremely critical.
> Alan
> 
> All expansion rates and times given are temperature critical. Temperatures below 75 degrees F will lower the expansion rate therefore requiring more foam. Ideal working temperature is 75 to 80 degrees F or above.
> Accurate measuring of these products is extremely critical.
> On 28/06/2019, at 11:04 PM, Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Not my forte, but given the hardness of this product when cured is there really an expectation that it is going to deform in a visually measurable way and spring back into shape from a depth test?  Seems like it's more likely to either structurally fail or not with obvious non-elastic results such as cracks, cavities, etc, hence the weight test to see if it absorbs water.  I'm thinking the dunk test from the sailboat is a good first start.
> 
> The cost of this product seems to be on par with trawler floats from a pound to pound buoyancy perspective but it has the advantage of allowing custom shaping.  I'm interested in the results.
> 
> Should we invest in a small amount of this product and put it to some more rigorous pressure testing?
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