Finally made further progress! On Saturday I tried another layup this time just a flat layup on Acrylic sheet. The acrylic was too thin, it warped once the vacuum was on, but its all I had. I put some weights on the corners of the sheet once it was infused (cordless drill, hammer, that sort of thing
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Before I did this though, on Saturday morning I made a T piece for the inlet to my carbon filter, one always on a hose, one with a ball valve. I was having issues with putting a T piece on anywhere else, the first infusion I put one on the line between the resin trap and the layup, stupid mistake - it filled with resin and that resin got into the Nitto fitting at the end of the T'ed hose, destroying it. That didnt bother me though, as Nitto really do not work at all under a vacuum, only under pressure. I mounted the carbon filter and the T piece on my light support strut on my work bench - it worked out to be a real life saver when it came to degassing things! It would be good to put some sort of one way valve on the line going to the layup, but we'll see. I haven't seen one at the hardware store before. This would stop air that is coming from the degassing chamber going to the layup, only being able to go through the filter and down to the reservoirs.
This will also allow me to do bagging or a second infusion whilst I have one infusion going, or to have two separate bags/vacuums on the infusion.
I also made a couple of other changes. Primarily, I switched the input to the resin trap to a 1/4" hose down from 3/8" (6mm from 10mm.) I was meant to change the resin inlet hose over too, but the monkeys at the hardware store are too incompetent to put parts on the right hook - it took me an hour to re-arrange parts when I was there enough to get the bits I wanted yet still managed to get a 1/4" barb on a small (no idea what size) thread. I need to take that bag and get a 1/4" barb to 1/4" BSP. The smaller hoses are slightly cheaper, use less sealant tape, create less of a bump on the outline of the part (so less of a pleat/wrinkle on the film), and are easy to seal as there is no overhang on the tape.
On to the layup!
First: the shadecloth works wonders. The resin sucked through out of the reservoir so fast I accidentally let some air through. Three times. The flow speed through the layup is much much more rapid with the shadecloth than without, and there is no pooling. The film appears to be completely pressed down on the shadecloth to the point nothing could flow through, but the small gaps it makes are more than enough.
Second: I got the spiral wrap I ordered - it too is fantastic. It's smaller diameter than I have used on wet bagging and smaller than I expected, but its *perfect*
It slides into the 1/4" hose and never quite fully compresses. The resin made its way down the spiral and into the cloth for a fairly linear resin front. In cooking, photography and many other trades they say it's not the tools, it's the operator that makes it perfect, but I've always found having good tools certainly helps - this is no exception. Flow media and spiral wrap make a big difference. I'm sure a master at this could do it perfectly with my prior crude setups but he'd sure have to work at it more than if he had his own high end gear.
The layup was done with the worlds worst fibreglass. Its something I got out of hong kong about 6 years ago and have avoided using ever since. The weave appears to have been done by a relative of the person who painted this road's markings:
It may have been meant to be plain weave, but is more akin to plain drunk weave.
It came folded into squares about 30cm x 30cm (1ft x 1ft) with each of the folds somehow separating the weave to create gaps of 5mm or more, the corners are of course worse. This obviously makes it the perfect candidate for testing things with! It'll make a nice AVBay sled or something very non structural. I did 12 layers of.. whatever weight this happens to be (180-220gsm perhaps was their intention). The cloth was about 0.15mm thick, I havent measured the final layup's thickness.
I did not cycle the vacuum on this part as suggested previously in this thread, I dont care about compaction on this enough and there were no wrinkes anywhere. I did leave the part under vacuum for a good 15 minutes before infusing however to let any moisture boil out, it has been a bit humid.
I degassed the resin prior to infusion, at the strongest vacuum I could get. I actually had to back the switch off a little, as the pressure on saturday it was considerably warmer than when I set the vacuum switch, and it couldnt reach the same vacuum with the change in pressure! At the much greater vacuum level than my previous attempts, and degassing for 5 minutes or more the resin had a slight layer of froth on it after coming out of the chamber (mostly around the edges) and the popsicle stick I left in the cup had a definite high water (resin?) mark about 3cm up. There was no overflow.
So, as I said before, the resin went in FAST without pooling, every time i shot a little more in you could see a definite rush on the resin front. When it slowed down too much I flowed some more in. The crazy bubbling stage did not occur this time, I believe this is due to the proper degassing prior to adding the resin. Bubbles (as mentioned before, resin shot in a bit fast and took some air with it a couple of times) made their way through the shadecloth without going into the layup it appeared which was a positive sign, you could see then flowing nice and linearly from one line of spiral wrap to the other. What did surprise me was how long the layup took to fully wet out. The shadecloth's resin front was FAR ahead of the line in the fibreglass, when it was fully wet out the layup looked darker and a clear line of resin in the shadecloth and resin in the fibreglass was apparent. There are a few spots which did not get fully wet out, however these appear to be only in the bottom most layer, and closest to the vacuum line.
Ignore the iron oxide, thats on the outside of the bag - I had some on my gloves from another project.
Vacuum line was to the right, you can see the lighter coloured sections in the thicker part of the layup where there are voids in the bottom layer of weave.
Another small section with voids.
All in all, it went quite well, and was by far the most successful yet. It's nice to see positive progress each time I do this.
Things I am going to try next time:
* I'm hoping to reuse the sealant tape on this acrylic sheet next time, it appears I can pull the bagging film off relatively easily without damaging its stickyness. I need to try to get away at lunch tomorrow to get some more tape, to use over Easter as I'm almost out. I need to make this stuff last more than one infusion as it's going to get expensive at this rate.
* Maintain the resin flow from the reservoir into the layup at a slow constant flow rather than several jolts of. I think this will make the resin front move better and also improve wetout. When giving shots of resin, the resin front would move rapidly though the shadecloth but take quite awhile to make its way through the fibreglass, this leads to wasted resin.
* Heat the resin as it flows through the layup with a heater or hair dryer, I feel that a lower viscosity will wet out the fibreglass faster and better.
* Wax the acrylic! I didnt, and didn't realise until about 3hrs later - rookie mistake, thankfully the layup came off without any issues what so ever due to this being a virgin piece of acrylic I had just pulled the backing off.
* Double sided tape the acrylic to some plywood or aluminium plate to keep it from warping. Aluminium plate would help even out the heating too.
* Switch to 6mm resin hose, clamping it to stop the flow - those gardening ball valves are all well and good but cost $1.50 and are stuffed at the end of it.
My next infusion will be on the acrylic again obviously, using another bag of the worlds worst fibreglass. I figure I should get the process down on a flat surface before trying to get tricksey with the curves
What are people's thoughts on peelply as the first layer on the acrylic?
