The Shop > Composites & Plastics
Glass fibre mould from the slender plug
PekkaNF:
It is a real gelcoat and it is sopposed to be tacky before lamination, but not mark finger when you touch it. You know the drill. I forgot that gelcoat needs somewhat more hardener than polyester resin...they all are between 1-2%, but mfg. reccomedations varies and they are suposed to give a table that has corrections on air temperature and laminate thikness etc.
Anyway, could not sleep right away and gave a last check to it at 0100....it was perfect. Laminated two chopped strand mats to it with 100g of polyester resin, tooks shower and slept really well.
This morning it was all good, cut out strands, ground edges and ripped it open. It released just normal.
I got the results I wanted.
PekkaNF:
Bottom plate is high peressure laminate over MDF, samples are tongue presser spatulas glued with epoxy.
Different paints and different drying times.
Six layers of release wax and half of the sample plate was covered with very thin layer of PVA.
Interesting notifications:
1: yellow strip, was just normal Pelikan Nakiplast, play dough (much beeswax?), soft and stcks to laminate, but releases fine and renders the shape pretty nice. Fastest.
2: Filler paste, the type that is used indoors to cover dents and holes on the walls before painting. Sandings easy on shapes, but shrinks - needs many layers. Porous and definately benefits from PVA.
3: Blue epoxy filler is expensive but nice. Dries few hours, but shrinks very little, sands just perfect and keeps the shape well. Only filler that is not porous and does not stick to mould.
other were different paints and drying times. I found one 1k epoxy base paint that dries fast, sands well and works out fine when let dry more than 24 hours. 12 hours you need PVA, shows on one sample.
Last sample was the traditional epoxy filler, primer, 2K urethane (dried 6 hours, which 2 hours in 90C in powder coating oven curing) and it worked out perfect ocourse. Looks horible, because I spread it with brush (5 ml of paint and 1 ml of hardener, hassle with sprayer). But the mould repeats the brush strokes beatiful.
Now I have the system (1k base paint, sanded fine, two days of drying (small samples faster when dried in oven) and wax + thin PVA) if I need waster, then beeswax and if I need better results, then 2K urethane, but that adds work and time.
Happy with test results, I actually got results.
Pekka
vtsteam:
That's great Pekka! Good job testing samples and refining what your own needs are. :smart: :dremel: :clap:
PekkaNF:
Thank you.
I had some trouble with this laminate...gelcoat geled faster and then this new polyester resin behaved differently, it did not wet the mat and was not tacky. Made it harder to negotiate around bends and bulges. Rolled a lot but the mat did not settle down and was hard o remove air. Hope there are not too severe rat holes near gelcoat, at the top there are plent of pockets and pools.....it was getting dark and and I was getting tired. Next time I will do only one mold per evening.
Questions:
1) Can I use this normal gelcoat and laminate epoxy over it? Gelcoat seems to produce good surface, but I feel more comfortable using epoxy to laminate thin parts. Handle parts needs paint and such embelishments.
2) If I gelcoat parts of the epoxy laminate, is there any tricks to paint parts of the gelcoated parts. Like if most of the surface is white and then some needs to be painted black or blue. Normal spray can paint is good enenough for few days and does not smudge hands?
Pekka
vtsteam:
Pekka, I think you're going to have to experiment again to answer #1 with the particular gel coat and epoxy you have, since that all varies. I don't know, myself.
Painting over cured gelcoat should be fine. You'll probably want to wipe it down with acetone or MEK. A light hand sanding with extra fine paper or even Scotch-Brite pad to kill the gloss wouldn't be amiss. That's what I would do, anyway.
It always boils down to the specifics of what you have for paint, etc. But cured, hard polyester fiberglass, in general paints well if wax is removed and the surface very lightly sanded.
ps, I'm also a little surprised that you are using mat on these swords instead of cloth. Mat is not easy to conform to short curves -- it has sizing in it. It's okay for large surface curves, like boats.
I would think you'd use cloth for a sword shape. And where there are complex curves, use strips cut diagonally across the bias. These will really conform well to those areas. Tape is not as good because it has a selvedge edge. Cut your own strips out of regular cloth at a 45 degree angle to the weave for difficult areas. The only trick is not over-tooling it when laying it in place, because fibers will get picked up from the edge and make a lump.
I'm guessing that you'd want something 6 oz/yd or lighter for the swords (sorry about the non-metric number, but that's what I'm familiar with). The lighter you go, the easier it will be to conform to curves, but the harder to lay in the mold without it sticking to your tool and pulling back out. And you will want more layers with very light cloth -- it's available down to 3/4 oz/yd which is like tissue.
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