Yeah I have noticed that too, I was guessing that I am not getting the fiberglass fully wet out in those areas?
I have used qcm's emv-0043 resin and eca-032 for almost all of my skis. In my opinion, its has a pretty high viscosity and it takes a litttle bit of work to get it into the glass. Sometimes it was hard for me to tell though because the more I tried to worked the epoxy around it went from clear to white....Has anybody else seen this?
A fellow snowboard builder recommended resin research to me, he said he had really good results with it. I built my skis and a splitboard out of it, and it is definately a lot easier to work with. Much lower viscosity, wet out the fiberglass really fast. Im a little bit skeptical because its designed for surfboards, but if my skis hold up this year I am going to use it for everyones skis next year.
It left a really nice finish on the topsheet of the splitboard. I didn't see the dry fiber. This is what it looked like out of the press-
n.marshall wrote:...It left a really nice finish on the topsheet of the splitboard...
About that woven carbon topsheet, so it's a structural composite layer wet-out with epoxy, looks great and I bet it holds up well. Did you use some sort of peel-off plastic layer to achieve that smooth surface? I've been using printed cotton fabrics with clear plastic topsheets which really just add dead weight and get all beat to hell too. I may do this using Texalium for that high-tech metal look on a future pair of skis.
n.marshall wrote: Sometimes it was hard for me to tell though because the more I tried to worked the epoxy around it went from clear to white....Has anybody else seen this?
We use the same combo of QCM products. From the best i can tell when it turns white during layup, its the epoxy going off for whatever reason.
jvangelder wrote:... Only way we have avoided it is by working faster
-Jacob
Not so fast. I don't think it's the epoxy "going off" that causes the white appearance. My experience is that it can become white looking when over worked, too much squeege motion trying to encourage fabric wet-out. The white color is actually micro air bubbles or foaming. It can lead to really ugly top sheet graphics and probably a weak composite bond.
So the best solution is to work slower, at least with the squeege.
yeah, I'm with SHIF
If you try too hard moving the epoxy around it goes white and frothy.
It does make fabric graphics look crap.
I think that trying to layup in a warmed environment where your epoxy is nice a thin, or using a resin heater or heated table is a really good idea to improve your process.
I think it leads to faster wetout, better wetout and also reduced layup time. Richuk has also shown that using a heated table and preheating your composites reduced the amount of epoxy he was using by 25% (and when you are building 20+ pairs that's real $)
I agree with SHIF and Falls - micro bubbles! I'm guessing people who are using lower viscosity resins don't see this issue so much.
Epoxy is 'going-off' once it's past it's pot life - usually this means it has started to gel, however, epoxy does increase its viscosity during the time in the pot, but it doesn't suddenly switch from one state to another. Not unless you're sitting it on a hot plate.
I really like the idea of pre-heating composites and resin, thanks Richuk. I have warmed resin in front of a heat lamp before, but never the composites.
There was no peel layer on top of the carbon fiber. Just a smooth, clean, waxed cassette.
What temps are people using to heat composites, resin and hardeners?
I try to get my shop air temp above 70f before a layup to help with this.
I can see that a thinner epoxy would wet out faster and would equal using less total epoxy but Does heating the separate epoxy parts cause it to kick faster? Is there a threshold temp for this?
Vinman, the link posted above should answer your second question, but if you want to look at it in more detail the data you want from your supplier is 'epoxy evolution'.
Because everyone is using different epoxy, I think the question is what viscosity achieved at 40 degrees C (the temp I use currently), the data suggests 320 Mpa.s is what I have been working with (viscosity at prescribed temps should be on the data sheet too)
warm the epoxy not the hardner and warm the dry composite not the wetted fiber. If you do warm the wetted composite dont do it for very long. It wont kick but it will gel and not squeeze out when you press.
The resin should all be at least 70F it works much better.
Bumped into your mate up at Porters ski field today, I saw him carrying the ski's through the car park and then found him up the hill and cornered him for a chat, wicked ski's really cool! Great to see your product all the way down here too.
