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LaxFriedrichs
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Today (7th July) was a freak day weather wise with temperatures at 26+ Deg. Celsius - this effected my gelcoats and coupling coat. During the second gelcoat, I found that globules/small pieces were forming in my mixing pot, fortunately these are mostly on the flange area. Even with less catalyst, the coupling coat globuled in the same fashion at a later stage of putting it all down. Regardless, I got the CSM to conform well to the 'pattern area', and most of the globules are also on the flange. So the coatings on the 'pattern area' are 95% OK, however the flange bit is a little bumpy (5mm dia max circular bumps). What's my chances of a decent mold for resin infusion (no post-cure for mould, nor in-mould post-cure for laminated CF)? I will be doing the final tooling resin process when it's slighly cooler tomorrow. Would the process work without any catalyst?
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wozza
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Sounds like the elevated temperatures are causing the resin to "gel" in the pot. I don't know the size of area you are covering so therefor don't know what volumes of resin you are mixing? You need the catalyst so try mixing at 1.5% but mix it in several smaller batches. The more resin you have in the pot (especially if the pot is tall and narrow) the quicker the exotherm process will kick in. Without seeing pictures it is difficult to say what effect the "blobs" will have on the surface of the mould. Regards Warren
Carbon Copies Ltd
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LaxFriedrichs
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Warren, I took your advice and did the tooling resin coatings by mixing up three batches (0.75% MEKP catalyst). The temperature was around ~19/20 Deg. Celsius this morning, and there was no 'gelling' from start to finish. Funny you should mention tall and narrow mixing containers - the one I used yesterday was exactly that. Instead, today I used a tupperware container that was rectangular and rather squat. The geometry of the part was relatively complex and required many cuts of the 450gsm CSM to allow it to conform. The tooling resin on the brush tended to pull strands away from the mat along these cuts, and at difficult edges/contours it all got a little messy. It done now, so there's no point worrying.I'll post pictures tomorrow when I pull the mould from the pattern and flange - I'm excited at the prospect! Thanks again!
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LaxFriedrichs
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Second gelcoat, first coat was much smoother...
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wozza
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No problem. Fingers crossed for tomorrow 
Next time don't worry about trying to get the matt down in large pieces around difficult areas, just rip the matt into manageable pieces and lay them with a "dabbing" action rather than a brushing action, it won't effect the integrity of the finished mould any. If you are using cheap brushes( nothing wrong with that) then it helps to cut 20mm or so off the length of the bristles to make them a bit stiffer Around tight internal corners etc I often completely shred bits of matt and lay that in there first just to make sure there is no bridging. Another thing I do with the Tooling Coat is to go over internal and external corners with a 1/2" brush and build up a thicker layer of Gelcoat. That way you have plenty of Gelcoat to sand/polish if required without breaking through.
Regards Warren
Just had a look at the pic, I think you should be ok from what I can tell.
Carbon Copies Ltd
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carboncactus
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Did you use the same pot for each gel layer? that might explain why it happened on your second layer. If you use the same cup, the remains of the first will exotherm since they are at the bottom of the cup, causing a quicker reaction on the fresh resin it come into contact with. At these temperatures, you should be catalizing at around 1.2%, maybe 1.5%. VE resins (like the one used as a skin coat) also tend to have shorter gel times and fizz when used with normal MEKP. Gelcoats are normally ok since they have fillers and pigments which work as retarders. I think I also see some alligatoring towards the right on the flange. This might be a combination of too much MEKP which causes shrinkage or putting the skin coat on too soon. Hopefully its just gelled up resin. wozza, im concerned as to why you winked when you wrote "stiffer"....
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wozza
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Ha Ha !!!!! I am from Todmorden " Where men are men and sheep are scared" Lol
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LaxFriedrichs
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carboncactus (08/07/2013)
Did you use the same pot for each gel layer? that might explain why it happened on your second layer. If you use the same cup, the remains of the first will exotherm since they are at the bottom of the cup, causing a quicker reaction on the fresh resin it come into contact with.
At these temperatures, you should be catalizing at around 1.2%, maybe 1.5%. VE resins (like the one used as a skin coat) also tend to have shorter gel times and fizz when used with normal MEKP. Gelcoats are normally ok since they have fillers and pigments which work as retarders.
I think I also see some alligatoring towards the right on the flange. This might be a combination of too much MEKP which causes shrinkage or putting the skin coat on too soon. Hopefully its just gelled up resin.
wozza, im concerned as to why you winked when you wrote "stiffer"....Yes, I did use the same pot for each gelcoat - I wont be doing that again!
It's a shame the Unimould instructions were more comprehensive (for the complete beginner).
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carboncactus
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No worries. I told you the first couple are scrapers  certainly the first one I made was. The second and third looked fine, until I post cured them. The problem is there's too many variables to list everything that can go wrong. It is, unfortunately, learn by mistakes.
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LaxFriedrichs
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And we have a probable mechanical lock... 
There is a long rectangular channel of the pattern, which I covered with release tape. My thinking is that the surface made from release tape wasn't rigid enough and deformed.
I used lashings of release agent and wax, so I don't think it's adhesion of the gelcoat layer and pattern surface.
If brute force doesn't do it I'll chop the bugger in half to get at the £100 pattern and do a post mortem.
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