what kind of times are you talking?? we were going to pull to 24 for 20-30 min then back it off to 5… we are testing on glass thursday
Just depending on temperatura/hardener.
I´m making complete vacuum.
When I talk about time is focused on resin’s viscosity.
Time: The requested to reach the gel state (acording to temp => hardener, dependent on part size and requested working time.
Only one vacuum. 100% when gel viscosity reached.
well I did 12 tests on glass… with clear and clear with a layer of epoxy brushed… Just the glass and glass with brushed epoxy on it, one with two layers of breather/bleeder and one with only one… my stack was cloth release and breather… I pulled it to 15 and it looked good… I then let pressure off to adjust bag and all hell broke lose… I was never able to get it looking good again…
round two with that info… we used glass again with no brushed epoxy since it didn’t make a difference… this time we did cloth ,release, perf, breather, same with no breather…
cloth, perf, release, breathe, same with no breather.
cloth release and cloth, release, breather… This time we pulled to 5 and let presure off and then to 5 again and waited then to 15… good results… the cloth, perf, release, breather looked the best… almost perfect…
we then pocked a hole in the bag and it still looked good as long as the hole was not so big that we couldn’t over come the leak…
so we heated the glass… (lower viscosity) bad news… I thought it would flow out but no… we actually got a few more voids in between the weave…
so at this point we pulled to 27 and it did help some but it was not a fix all…
The main thing we found at this point was once you pull vac on a wet layup you can’t let vac off… You REALLY need to do all the work on the front end and then pull your bag down to less then 5 and adjust it to your corners and complex shapes (2-3 would be best) then do your big pull of vac…
we never say air bubbles get bigger as we pulled more vac, like to 27 hg… and it did help to make the very few voids get smaller… we were able to back the vac off, like back to 15 and not have bad results but the voids that were there did go back to there original size…
our final test was thicker epoxy ( 12000-15000 cps) the first tests were with 9000 cps
to see if that changed anything… and yes it did… the thicker the epoxy the less voids you have IF you have to let pressure off totally…
so it’s not a bad idea to let your regular epoxy gel some before you pull vac… and don’t heat the epoxy once it’s in the mold. Do a post cure heating… I’m not saying you can’t. I’m sure there are some people that have dialed there process in and can do it with no problem, we are just not there yet… Plus thicker epoxy of more gelled epoxy helps and don’t let vac off once you start pulling… When we prepped right we had a very nice part at 5 hg and have more predictable parts the more vac we put on it…
hope this helps some people