Repairing a mold

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Kez

Well-Known Member
Joined
Feb 27, 2003
Messages
1,230
I have always liked the open cockpit tunnels and I have decided to make my own. The mold came off the plug OK but there is a slight lip where the plug met the parting board. I need to remove the lip or it would lock the layup in the mold.

Question: can I use a file to take out the lip and then wet sand to smooth it out?
 

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Thanks Phil. Do I need to wet sand or use rubbing compound on the mold? Or can I just wax and then PVA before the first layup?
 
if you want perfect finish rub it out, waxing and pva after fine sanding will work ok. if the part is to be painted the mold finish dont have to be perfect.
 
I took a file to it and it worked out well. After taking out the lip, I found a few shallow voids.
I used modelling clay to fill the gap between the parting board and the plug. I am wondering if I can use the same to fill the voids instead of gel coat. If I have to fill the voids, can I use Bondo?
Thanks,
kez
 
Polyester filler works fine i will sand down ok. the mold is harder than the filler so it should level easily. The clay would do the same just not permanent
 
In my experience, pva will not work over bondo. The part will stick on the bondo unless you seal it with polyester primer, duracoat, gel coat etc. Personally, to save work I would use clay if it is just small areas and just replace it with each part.
 
I have had bubbles show on the mold after I pull the plug. If you just fill the hole the parts pull can pull out the patch. I will drill a small hole all the way thru the mold. I make the hole on the outside bigger than on the inside. It tapers to the inside hole. You can tape over the hole on the inside and fill with resin. That way the plug will never get pull out. I use 400 grit to get it sanded after it cures. Then its ready for a nice waxing.
Mike
 
Thanks Mike, I might give that a try. But I will try the modeling clay first.

kez
 
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