We have a mold

Yesterday was a very good day in the workshop. It started a little slow as I was working on small tasks on the Legacy. Then Dave arrived, and we decided it was time to release the mold.

I had some discussion with Dave about whether or not to build a rigid structure around the mold prior to release from the tool cowl or after. It was actually kind of nice to have some flex for releasing the mold. So I elected to go ahead and release the mold. Then we would put it back in place and build the structure.

The release went easier than I could have hoped for. When I found a place to put the wedges in, I could easily slide them along the surface and the mold would release 6-8 inches ahead of the wedge with a growing air bubble visible between the tool cowl and the mold.

When I got the perimeter of the mold released along the flange, I then switched to the pneumatic wedge. This was really cool. It was awesome to see the mold “inflate” and release easily. The separation bubble just progressed as consistently as could be. A few strategic places to use the pneumatic wedge, and it was completely released.

Dave and I brought the mold off the airplane, inverted it, and looked at the surface. I was very happy with it. It was, however, more flexible than I wanted. I was concerned that in the heat it would warp. So I wanted to build a wood structure around the mold while it rested in place on the tool cowl.

A quick trip to the aviation isle in the Lowe’s, and I had the materials I needed. I cut some pieces of 1/4″ plywood and 1×2’s to jig up a rigidity structure that would also act as a base for when I am working with the mold. I screwed this structure together and then bondo-ed it to the mold. By the time I had a few blobs of Bondo on, you could shake the whole airplane with the mold. A few more blobs, and I was satisfied.

With other distractions and tasks for the day, it was pretty late by the time I got all the Bondo on that I wanted to. Brian and I remove the mold and base from the tool cowl and put it on the table. I got a better look and removed some of the PVA. It peeled off in a sheet.

To say I am very happy with the surface is an understatement. I will do more evaluation of it tomorrow, but I think it is going to be very easy to prepare this mold for a layup. I was concerned yesterday with air bubbles in the mat plies, but I think we are going to be ok. We will find out soon enough if it will hold vacuum. I think it will judging by the surface.

I did learn a lot yesterday about mold making. Things about using chopped strand mat, epoxy vs polyester, resin quantities for types of fabrics, etc are all things that I need to think about. I really think I got lucky that I pulled of what I did. I will take that into account for the next mold I make. There are a few other things I’ve recently learned about that I would like to try on my next molds too. I will keep learning about mold making and sharing my thoughts as I try new things. Seems they are going to be key to making good, light parts.

Next steps will be dressing the edges of the mold, fixing minor imperfections, polishing to 1000 grit, and waxing. The process from there is all fun.

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