[PSUBS-MAILIST] Foam preperation

[Alan via Personal_Submersibles]

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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