More foam questions.

[24flatback]

I just ripped a bunch of NEW foam out of my project today. I'm not sure exactly what went wrong. Everything looked fine at first but over a week or two the foam deflated and broke down.

I may have poured a second batch on top of the first before it fully cured. Or maybe I should have sealed the top where I trimmed the excess. Either way I'm also a bit gun-shy about pouring new foam in until I figure what whent wrong. Does anyone have any tips that may prevent this from happening again?

[Mad Dog]

What type and brand of foam did you use?

MD  

[24flatback]

It's just polyurethane foam from fiberglass coatings. I also did not measure the parts before mixing due to the fast reaction time. Idon't know how sensitive it is, but I think i got it pretty close to 1:1

[Mad Dog]

This is the stuff I used with no problems.  http://boatbuildercentral.com/products.php?cat=56

It is a 1:1 ratio.

You mentioned not measuring due to the fast kick, maybe you poured it too quickly and didn't get a good mixture.  I used three pots in my pour routine.  1 each to measure the two parts. The third was my mixing pot.  With both parts accurately measured I poured the parts into the mixing pot.  Then stir quickly, scraping the sides and bottom, until it just starts to kick (between one and two minutes) and pour it into the cavity AS QUICK AS I CAN, scraping out only what is still flowing.  Then, leave it alone.  Once the foam starts forming the bubbles any more manipulation colapses the bubble and makes a hard non-bouyant film.  

Inless your pur got acetone (or worse) on it not much will disolve it.

MD  

[24flatback]

Thanks MD. It does kick fast. I could barely manage to mix it before it started coming out of the can! I bought some more today so I guess I don't have much choice but to give it another shot. Like I said before I don't knot what went wrong but I suspect a few things so I'll try to be more careful next time.  Thank again, Nick

[LilRichard]

I found that by putting the two parts in the fridge for a few hours, it significantly slowed the reaction.  I think I bought myself 2 minutes or more by chilling the product.  Try it - it works!

[blindmullet]

Poor mix ratio+ hot weather I would think.  This happend to me in one spot.  Mix small amounts in something with a lid so you can shake it and pour it.

[Mad Dog]

Richard has a good idea.  I did my foam pour last winter (well what we call winter in South Texas) so I was working with cooler materials.  I refrigerated my epoxy to buy more pot life, that should work with the polyurethane foam too.  

MD  

[24flatback]

Thanks guys. I was working in the direct sun, so heat was probaly part of the problem. I have the boat in the garage now so maybe heat wont be as much of a problem. I have been useing coffee cans to mix it so I will try capping and shaking it next time and also cooling it down.

                              Thanks again guys,  Nick