Trial 2; 12.5x35 layup with core
Goals: (I had a bunch I wanted to learn from this test)
Find out how fast resin will move through the entire layup
Find out how far resin will go before gel
Make sure spiral inlet flows fast enough
Make sure double-cut core flows ok with glass layup
Verify resin uptake for glass with double-cut core
See if using self-adhesive Teflon film on melamine works with vacuum
I was struggling to figure out how to do a 13’ long layup of the decks with an air tight layout table – the best answer I could come up with was a couple of 4x8x3/4 sheets of melamine but the joint was a problem. There is a Teflon sheet (roll material, 1m wide) that works really well for hand layups that has a silicone self-adhesive backing and a nice slick surface. I decided to test it on a 2x4 sheet of melamine to see if it works with vac infusion since it would make sealing the joint between 4x8 sheets easy. I put the Teflon down on the melamine and then started doing the glass/core layup just like what I have planned for the decks:
peelply
7725 2x2 twill (top surface but on the bottom for the infusion)
1808 12.5x35 (CSM towards twill)
1400 12.5x35
1400 12.5x35
1808 12.5x35 (CSM towards core)
¾” double cut Corecell (A-500) 9x30 with beveled edges
1808 12.5x35 (CSM towards core)
1400 12.5x35
1808 12.5x35 (CSM towards peelply)
Peelply
It is all topped off with nylon bagging film
The twill is super hard to cut straight even with good glass scissors and tape, so I decided to try some electric cutters – THESE ARE AWESOME!!!! I used ‘em on all the glass, the peel ply, everything.
I laid everything out with spiral wrap for the inlet on one end and MTI tube for the vac on the other. I used a plastic fitting for the spiral wrap from Airtech to connect through the nylon bag to the Tygon infusion inlet tube – they work pretty well and resin does not stick to them. That was sealed through the nylon bag with tacky tape.
I did cut the spiral wrap a bit to let resin get in from the fitting easier (pics of that next time). I taped each end of the spiral down with flash tape to keep it from moving and to keep from getting flow out of the ends which could mess up this test. The test is also supposed to represent how resin would flow into the full deck layup from the perimeter. Having the spiral was on one end and the MTI tube was on the other end was like infusing one side of the deck but with a longer infusion distance (35” instead of ~15”). I had the glass extend 3” between the spiral and the core to mimic how the deck flanges need to be made. The peel ply covered all of the glass and the MTI tube was on top of the peelply – I covered The MTI with a strip breather material. I used tacky tape to stick the nylon bag film down over the whole stack – the tape was right on the edge of the Teflon sheet.
I pulled a vac, patched a leak with help from the leak detector, leak tested it for 15 min, then vac overnight to make sure any water was out.
Based on the first test results, I calculated the max resin uptake with 0.6 oz resin/glass for the 7725 and 1808 and 0.5 for the 1400. I increased the glass weight by 6.4% over spec based on that test too. The resin uptake of the Corecell was a lot harder to estimate. Gurit quotes resin uptake for A500 as 245g/m2 of surface area. I am using double cut core instead of perforated core only because I got a great deal. Perforated cor is better for flat panels and double cut is for curved surfaces. Double cut makes it hard to figure out the surface area but the short version is that ¾” double cut has ~7450 in2/yd2 of surface area including all the cut surfaces and both sides – that was a royal pain to figure out. That works out to a resin uptake of 41.5 oz/yd2. Including the volume for the layup, the feed line, the spiral, peelply on both sides, and 8 oz residual, I came up with 56 oz. My lower bound from using 0.45oz/oz for the glass and everything else the same was 46 oz.
It was about 70F at noon in the garage when I mixed 55 oz of the VE infusion resin and 1.2% MEKP using a drill mixer. I did it slow but could still see tiny bubbles in the resin. I let it stand for about a minute to let some of the entrained air out (it wasn’t enough time), put the tygon infusion tube in the resin and unclamped/unkinked it to start the infusion.
It took about 3 min to reach the core which was pretty close to my calc of 1.1 inches per minute.
The infusion rate through the core started out fast but got progressively slower.
The resin in the tub gelled at ~33 min with 14 oz left (~74F) so I clamped the tube then but it had not gelled completely in the part – resin continued to move for ~5 more minutes. It did a pretty good job of infusing but there were some dry corners at the end that did not infuse.
While it was infusing I noticed that the Teflon sheet was pulling slightly off the melamine around the edges of the layup – I kept pushing it down but was pretty sure the Teflon would not work as planned.
I let it cure under vac overnight (garage was ~80 for several hrs and dropped to 65ish), then removed the wrappings and trimmed with a metal cutoff wheel on an angle grinder.
Bottom (up during infusion)
Top (down during infusion)
I was amazed at how good it came out.
It weighs 6 lbs (2lbs/ft2)
Almost no flex with >300 lbs in the center when supported on the ends only.
The glass in the flange was ~0.175” thick as compared to an estimate of ~0.27” for hand laminating.
The resin moves through the glass flange lots slower than through glass+core.
For my layup schedule it took 15 minutes for 3” of glass flange and 18” of glass+core (21” total) – that should work fine for the decks but I might add some flow media on top of the flange just in case.
Although I was testing to see how far it would infuse before gelling, I think I should shut off the resin before gel since there was a lot of excess resin around the spiral and into the flange. Maybe even pull a vac on the infusion line after saturation.
My resin uptake numbers seem to have enough conservatism (slightly high) – I hope. I could probably get ballsy and use 0.5oz/oz for the glass and 41 oz/yd2 for the core and be fine but I don’t have enough experience yet to risk a $400 failure and do-over to save $20 in resin.
I need to let the resin stand longer after mixing for air to get out – there is a small bubble at the flange/core edge that I think is from entrained air in the resin.
The Teflon sheet does not work with vac for me – it lifted up from the melamine and left creases in the layup around the edge of the core.
For my deck layout table I will go old school and butt joint the melamine then wax it and mist with Partall.
The house did not smell like styrene – I might even be able to do this when the wife is home.