Separation Anxiety
by Jake on Feb.27, 2007, under One Meter
I broke the mold and fence away from the support structure underneath and flipped it over to being removal of the parting fence. It went relatively easily and I only had to pick out a couple of the green knobs that created the indentation for the other mold half to lock in place with. Some of them didn’t seem to sit flush with the parting board and they let a little bit of gel coat creep in around the edges so I’ll have to touch up the indentations to ensure they have a nice clean entry. The rest came out quite well so far. I have not tried to remove the plug and I don’t believe I will do so until after the other mold half is complete. I noticed that the plug has a 3″ scratch where it was in contact with one of the cradles so I’ll have to touch that up before I get started with the rest of the mold….it shouldn’t be difficult…a little finishing putty, a squirt of clear, a little wetsanding, polishing, and wax and we’ll be ready to go for round two. I’m a little unsure about how to proceed with the clay that is in the seam of the mold – I think I’ll clean it out as much as possible with a pick and leave it like that. The seam between the hull halves will have to have a bit of cleaning up after molding anyway. I cleaned up the really rough edges of the mold using a carbide cutter in my dremel (another dream accessory for the dremel!) and called it a night.
February 28th, 2007 on 4:09 pm
Jake:
Regarding the clay left on the mold flange. If you used water-based clay you can clean it the same way you had to clean the PVA the first time. With a damp cloth it will all come off. If you used oil based clay you can try a bit of mineral oil on a rag to get it out. As an experiment try putting the clay on a smooth surface, use your thumb to press it hard, and clean it, to see how easily it works.
For the backing of the gel coat I use something to thicken resin and fillet any of the sharp inside corners. I start with a fairly thick coat of gel coat. When that get tacky you can spread on resin thickened with, I use colloidal silica. Make it a consistency that will not flatten out with gravity, short of peanut butter. You can put a layer of glass right on that while it is still in a mood to be formed. This way you will get a good bond to the paste with the backing of fiberglass. If you do not use one or two coats of a fine veil material (glass) right on the gelcoat you should consider using a chopped strand mat instead of weaved fiber, it is less likely to get print through.
I like the shape of the hull! Rounded top to shed water, that is a good idea.
Later,
Dan
February 28th, 2007 on 4:49 pm
Thanks for the advice Dan!
The clay is oil-based and mineral spirits does clean it up nicely (as was the case cleaning my fingerprints off the plug – but I had to re-wax it because the mineral spirits also took off my Partall wax). I used an oil-based clay because I wanted something that wouldn’t dry up on me (and shrink) since the time between setting the parting board and laying the mold was probably going to be days.
I did use thickened resin to fill in the sharp corners just before placing the fiber reinforcements – using both milled glass fibers and micro balloons ( as written about HERE ). I’ve found that the milled glass fibers alone tend to make the mixture very dry but very very solid with terrific adhesion once cured. I added the microballoons to help get it to a more pasty consistency before the milled glass turned it dry. I simply didn’t have any colloidal silica to mix in but I have tubs of the other two. Finally, although I didn’t use veil, I did use a lightweight 3oz satin weave cloth for the first layer. At least on the horizontal surface where the parting board was, there doesn’t appear to be any print through – but we’ll certainly see when I pull the plug!