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Glass fibre mould from the slender plug
PekkaNF:
6 coats of release wax + layer of PVA release film
2 layers of 160 g/m2 twil and SP106 laminating epoxy. Hope it works, but it did not go around the corners that great. Hope it does not have exsessive amount of voids.
Pekka
PekkaNF:
All went pretty ok, but:
1: I don't use gelcoat to keep the whole thing translucent, therefore back of blade side corner was not crisp. probably have to laminate veil and think of using a perforated separation film and pressurepad or slight pressure or vacuum on it.
2: Turns out that two layers of 160 g/m2 twill is thinner than I anticipated. Anyway, glued them together on the mould to see if can be done and keeps straight.
The release wax and PVA works, it even gives an early release....now went to other end of the extreme...look and learn I guess. Maybe just a dab of film on the nearly vertical feature of the mould (back of the blade).
Think that I'm going to put just a little mictoballoon or silica thickened resin at the very back of the blade section before veil, to keep it in shape, also very tempted to add some of that micture at the very blade edge to give more surface for gluing it. Might even need to make it two steps.
I got pictures, but they are boring and they donät actually show much....paper thin one meter katana type blade at this point.
Pekka
PekkaNF:
Started working on another sword mold. Can't get my head around it, but think I'm going to build it in two part and need two moulds: blade/handle and cross piece.
Now the interesting part is that I am not very familiar with polyester resin. Information I read is a little confliking.
One major thing is: Some information emphasis putting a veil over gelcoat, let it dry (to various harness, often completely dry and then continue with structural layer. Some videos people seem to build pretty much (or least seemingly) the whole mould laminate on one go.
Which way it is and why? I never build that thich laminate, taht it will heat up.
I get that adding stiffeners to wet laminate will shine trough, but those I could add day later.
Any advice on mould laminiation sequence?
Pekka
vtsteam:
Pekka, general purpose polyester resin (also sometimes called "finishing resin") generally has wax in it so that it will cure hard on the surface. Wax floats to the surface before cure, insulating it from air. Best for all-at-one-go type work, or as a final coat on a molded part IF you don't plan on attaching anything else to it, since a wax surface isn't good to adhere to. Polyester resin is a poor glue to any hard surface or material. Epoxy resin can be used to glue to polyester, if any surface wax is removed. But polyester itself will not work well with an already cured polyester surface, even after wax removal.
Laminating resin doesn't have wax in it, so that it can be added to by subsequent polyester layers or attachments in a mold. Even cured, it is still tacky on the exposed-to-air-surface, so subsequent layers of polyester WILL stick to and and cure it. Polyester without wax is an air-inhibited cure resin.
Gel coat also is air-inhibited cure, for the same reasons. subsequent layers need to adhere to it. However it does cure (harden) against the mold surface, since that side is not exposed to air.
Because laminating resin stays tacky on the surface, even when cured, you can add subsequent layers without having to rush it or build up too much thickness all at once. If too much thickness is built up all at once, all the resin will cure at the same time and get hot and cause other problems.
Is that any help?
PekkaNF:
Thank you Steve very much!
That clear my confusion completely. Now I feel pretty stupid....I had read and "knew" all details, but could not connect the dots.
I knew the difference on gelcoat and topcoat, but never knew the fundamental difference on polyester resins. I was baffled, because when I was young I helped one motobike racer to build fairings and cowlings on my summer holiday...I remember him planning everytihing beforehand, and some stuff had to done when "green", some when hardened and some demended peel off ply. Pretty sure he always used tooling resin, because backside was always stricky and had to topcoat it in the end. I think we were building only molds and remember him showing how different the parts were when laminated from epoxy or polyester.
This was exactly why I had this confusion, because my previous experience did not match my results.
That shop where I bought my resin had only one type of polyester resin. The plan is to use this can of that resin for next mould (will be build on one go then!) and try to find laminating resin for the next week.
Pekka
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