I am going to be trying something a little different with the blog. A few people have suggested and/or given me advice on how to add video to the blog to make it a bit more engaging for folks. So I am going to give that a try. I took some time lapse video over the last few workshop sessions. To my surprise, it really didn’t take all that much time to edit the video to put it all together. I am not likely to spend the time editing to get a cinematic product, but hopefully for enthusiasts it will be a bit more engaging.
I will try to keep up with more detailed description via text in the blog and posting close-up photos here. I am hoping that adding video content will actually take less time than it usually takes me to write a complete blog post.
Making the diffusers for the rear engine was basically arts and crafts. It started with poster board to get 2-dimensional shapes to bridge from the inlets to the plenums. I start with poster board because it is easy to cut and work with. You can use masking tape to tie pieces together and try different variations pretty quickly.
Then I take a refined poster board shape and turn it into foam core. I typically hot-glue the foam core together and to its mating surfaces. This gives you a skeleton to work with that has approximately the right profile and planform. From there you can add poor foam or pink construction insulation foam and start whittling and sanding to shape.
Lastly, I use some kind of mold release on the plug. It could be aluminum tape, saran wrap, etc. In this case, it was white vinyl tape. Be careful though, you may still want to wax and/or PVA the plug. For whatever reason some of our vinyl tape released super easily, and some didn’t. We spent a day getting the tape to release from our part. A coat of wax would be cheap insurance.
I didn’t show it in this video, but I chose to do each diffuser in two halves. A top and a bottom with an overlap. I did this because it was going to be too hard to do the whole layup at once in the 115 degree plus hangar. Also doing the layup against gravity on the bottom side would be difficult in place. So I did the top sides in place to ensure alignment of the diffuser to both the inlets and the plenum. Then I sawed the plug off the inlets and removed the plenum/diffuser plug/top side layup as a unit. This allowed me to do the underside layup on the workbench.
This update also shows the initial installation of the Air Flow Performance FM150L fuel injection servo and fuel distribution block. I was attempting to keep the orientation shown in the video to allow me to buy off the shelf products for securing the throttle and mixture cable housings. In the end, I decided that making a bump in the cowl, or having to try to hide that in the induction inlet was too big of a cost to be able to use off the shelf parts. The mounts for actuator cables are easy enough to fabricate.