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Nice effort , No matter what hardener you use you still have to de pot the resin onto your work or a plate as soon as possible.

Finish one side completely , first one layer , let harden, clean up opposite side early if necessary , then 9 more. Wax the new side a couple times , especially the edges/creases, of part to mold, then light coats of hairspray to perfection and you should be fine. I did another run with just resin when the edges came out really shitty and the mold came out best ever.

A mast takes 2 or 3 hours for me to layup , so time is a factor but multiple batches of medium speed will not get out of control

I still have meltdowns regularly, try not to breath the smoke, I bet it is not healthy! Has anyone seen flames ,really??

Spring is coming

PLA mast mold worked pretty well. I got impatient at the end and the mold warped, but the mast seems good to me. I did overfill the mold so the mast is a good eight inch wider than intended.

Spurred by my success I tried a fuse mold with a little more patience. It came out better but the mold still had a small amount of warping. Small waves formed where I can see the pattern of the support material underneath.

I am printing a plate mold with a thicker outside layer, 1.2 mm to try next.

opie wrote: ↑

Sun Feb 25, 2018 11:24 pm

I have a mold for a mast that is .75 inches/2 cm thick. It's made of PLA plastic that softens around 150 f / 70 c. I am thinking if I lay it all at once it'll exotherm and melt the plastic. Is this a valid concern?
Thanks.

Nice mould Opie,
You could try designing in a water cooling pipe channel next time?
Or print the model and cast the mould in polyurethane or silicon rubber? That's worked well for me.
Or use a slow cure epoxy, some are designed for a post cure to fully harden and won't exotherm much.

No idea what you mean by "water cooling pipe channel", Google was no help.

I expect printing the model and making a mold from that is the most effective method. I just don't have the skills to make molds yet. I've had two or three failure's, I need more practice. The Pla mold is the first method I've been successful with. It is very easy.

I tried slow cure epoxy at first but now I am using 20 minute instead. I do two or three layers at a time, 30 minutes apart, for a few rounds. then the original layer is hard so I can go much faster for the rest of the mold. This worked well on my plate connector.

You're getting there

It does look like a little dry in the middle tho. See, my thinking is that vacuum actually helps a lot with not having a dry spots. You might reconsider your layup and use the epoxy injection. That way all this messy work would be eliminated and no dry carbon.

I see your print is destroyed. Why don't you print a 'male' one and make a mold from that in ie, plaster? Plaster is cheaper than print, but it does shrink a bit, however there are new materials which do not. Bille was writing about it somewhere...

More importantly, that mold would survive a vacuum.

I've got a bag of Fix-it-all in the garage ready for my next attempt at a mold.
I am considering trying to make a copy of my Go Foil mast when it arrives.
I also like Dirk's "dirty mold" method. It seems like I could strengthen them with pour foam.
Anyway, in the meantime, with the PLA molds I am gaining skills and getting something useful.

opie wrote: ↑

Fri Apr 27, 2018 1:13 am

No idea what you mean by "water cooling pipe channel", Google was no help.

It's not a "thing"
Simply subtract an oversized pipe shape from your 3D printed mould design so your printer will print around a pipe cavity. Then when it's printed, feed some clear tubing into the hole with some silicon sealant for heat transfer. so long as either the tubing goes right through each hole or they are properly sealed, then you can slowly run cool water through it to retard an exothermic resin cure melt down. But really, a slower cure resin is easier to work with for a deep pour.

Those moulds are pretty big!
Extra large printer or ABS sections acetone welded together?

Cr10 printer, so 10 or 11 inch sections glued together with acrylic glue. Three sections each for fuse, mast, and the 32" wing I am printing now.

Here, while we discussing took me 20-30 mins to pour gel coat in and now I have perfect mast male mold:
I’ll just wrap this mold with heaps of carbon and that is it. The reason why I’m doing this it’s easier to work with smaller part than 1m long mast.
Other reason is that my DIY mast needs Tuttle as well, so will be the same method but mast will be inserted in the orange Tuttle box, bolted and gel or Epoxy poured in with heaps of carbon. Easy.

downunder wrote: ↑

Sat Apr 28, 2018 3:21 am

Other reason is that my DIY mast needs Tuttle as well, so will be the same method but mast will be inserted in the orange Tuttle box, bolted and gel or Epoxy poured in with heaps of carbon. Easy.

My first mast didn't come out straight. I thought I had it set right but apparently not. I need to work out a fool proof way to get it straight and hold it there for next time. That's why I tried printing the connections, but the tolerances are not perfect, and my mast only fits about halfway into the fuse and plate. It also rocks like there is a high spot. Hopefully I can sand it evenly.