More Cowl Plaster master

When I left off I had just released the Plaster male master from the female plastic splash. The male master had inlet inserts incorporated into it. I removed the inserts and exposed the inlet cavity. This really worked quite well, but I did not like the inside junction near the spinner. So I modified the master by sweeping bondo with a larger circular drag. After a ton of sanding, this is what the inlet now looks like.

inlet

You can see the larger circular fillets I added on the inside with the blue colored Bondo. I set the master on top of my welding table. It has a 1/4" thick flat steel plate for a surface. I coated this surface with carnuba wax and then made a wooden support and using Bondo, I temporarily attached the plaster to the table. I set the spinner plane level, I need to set up a set of waterlines and stations that I can use to scribe the trim line into the plaster. This will transfer to the tool as a positive resin line, which will then transfer to the final part as a negative scribe mark. 

The surface finish of the plaster is perfect. But if it gets scratched, its not the end of the world, scratches will become small resin ridges in the lay up mold, I usually wet sand the molds with 400 grit paper, this will knock off any resin ridges. 

There is quite a gap between the master model and the table. I want to use this space to extend the surfaces. Its always a good idea to have excess tool surfaces that are set beyond the final trim line. In a production environment these would be used for the vacuum bag seal surface. 

Here is a side profile with the old spinner in place. I like the lines!!!  This should end up looking pretty good. The spinner was designed originally for the MZ-34 engine. This engine was a much more compact design and placed the spinner much closer to the firewall. Since I didn't want to remake the spinner and the backing plate lay up tools, I elected to stay with the original. That presented a real challenge when I reset the upper surface contour. It turned out ok, but it basically determined the center line of the crankshaft for this new engine mount position. The real problem was the lower lines blending into the existing fuselage lines. If I had stayed with the original fuselage line, the cowl would have had an inverted curve and looked terrible. So I re-faired the fuselage by creating two false longeron lines and increasing the depth of the cowl. The results however speak for themselves. 

foam block extension surfaces

So here is where I'm at right now. I blocked up the gap at the base with my floral foam.  I will saw and sand the foam until the surface is at or slightly below the extension surface. I will then sweep some plaster over the foam to stabilize it and then follow up with a final sweep of Bondo to finish the surface. Its pretty tough right now getting a lot of work done, in the late afternoon its been over 95 degrees and the heat index is over 106. So I probably wont get this next step finished until this week end when I can get out to the shop early before the heat builds. Texas is a wonderful place to live, 9 months out of the year!!!  From late June until early September however, it's hotter than hell!!!