Hi, I have finally found a method of hotwiring that is quick! For ages I was useing thin ni-chrome wire conected to a 12v battery witha long lead and it just takes ages and also breaks frequently.
I now use a stainless welding filler rod, conected to a 12v battery via jump leads and it flys!
My question is 'pre gassing eps'. I'm currently installing Gore vents, but the EPS I'm using is fairly high density 150 grade (or 24kg per m 2). I bumped into a guy the other day in the water who pre gasses his blanks so doesn't install a vent. Does anyone know if this is actually works, ie doesn't the gas just get sucked back in when you take the blank out of the hot room? What temperature do you need to heat the blank for and for how long, and are there any adverse effects.
Excuse me if this topic has already been discussed I did look but couldn't find any thing.
I think that your logic is sound but check with the mfgr of the EPS foam you are using. Without doing the conversion from what you are using to what I am using (2lbs per cubic ft) it is hard to tell if they are similar, but most of the higher density foams these days don’t really outgas (at least that’s what my supplier told me). I bought a block of 2# foam from Insulfoam after they assured me that their foam did not outgas and have made a few boards from that. A couple of them sat in the sun all day last summer in San Diego without any ill affects. It was host enough that the red board actually faded some from the sun.
In short you may not have anything to worry about.
Hey Thanks for the replys guys. Either my maths is very bad (possibly) or I have been told the wrong figures but when I tryed to convert 24kg per m 2 into pounds per foot 2, and it was way out. But maths aside it is the dense stuff, they call it extra high density, and the beed size is similar to what you find in disposable EPS drinking beakers. I'm based in the UK thats why its metric. Back to the point, thanks for your reasurances, and I'm making some enqiures as to whether or not this EPS does gas or not, but as its Christmas... well almost, everything seams to be sutting down now, although my mind keeps ticking over....
“Either my maths is very bad (possibly) or I have been told the wrong
figures but when I tryed to convert 24kg per m 2 into pounds per foot
2, and it was way out.”
If you glass in low temps you will get pinholes in your glass job from outgassing, there is always a bit of vapour emitted from the blank, be it gas from the manufacture or simply air expanding due to the heat of the resin and the force of the glass job on the foam core.
a warmer eps blank has has less of this problem than a cold one. Again, this is my experience from a cold climate and having built boards with temperatures between 10 and 15 degrees c. (not an advisable experience trust me)