mikebpd221
Active Member
- Joined
- May 9, 2019
- Messages
- 36
- Reaction score
- 20
I'm making my first serious effort at making a diamond airfoil with a similar compound profile as seen on various Nike boosters. The prototype that I made from balsa and plywood laminate did not go terribly well. I had some difficulty getting precise breaks in the compound angles by trying to sand them in. I'm building in a smaller scale than the examples John Coker did in his tutorial. Unfortunately, that magnifies the effect of errors and my hand sanded bevels were pretty inconsistent. I wasn't real happy with the material strength either. Trying something different seemed like the right idea.
I've got a fairly well equipped woodshop, so I'm going for the table saw to make a second effort using canvas phenolic sheet instead of balsa over plywood. I've been able to put pretty decent airfoiled edges on fins using a 10" sanding disc. The compound profile removes a lot more material though. In prior experiments, the heat from sanding off that much stock softens the composite and I get warping. I'm trying to get around that by using a blade this time. First, by stepping down the primary bevel a 32nd at a time with the fin stock flat on the table. The diagonal will finish with the fin to the proper tapered surface. I've got a tenon jig that I can tilt just enough to take the fin from 1/8th at the root to 1/32nd at the tip. If that works, then I cut the leading and trailing edge angles. Their bevels are going to take a little more effort to set as the workpiece will be at both a lateral and vertical angle when it is run past the blade. Knife bevel calculators via Google are good for one plane at a time, combining them for 3D geometry is not what they were intended for. If the process works, each step gets repeated 8 times and I'll have a series of half fins. The pairs will get mated as a final step. Planning on skinning the bonded set with fiberglass to make sure the surface has a uniform finish for paint.
Some feedback would be appreciated. I'm expecting a few failed test pieces along the way but if someone can point out where I can improve the process before I start that would be helpful. Finding someone with a 3d printer or CNC machine to make them for me has already crossed my mind. That's plan B if scratch building my own doesn't work out. I figure this community has enough crazy and stubborn (read creative) minds to relate to wanting to make it on my own bench. Thanks.
I've got a fairly well equipped woodshop, so I'm going for the table saw to make a second effort using canvas phenolic sheet instead of balsa over plywood. I've been able to put pretty decent airfoiled edges on fins using a 10" sanding disc. The compound profile removes a lot more material though. In prior experiments, the heat from sanding off that much stock softens the composite and I get warping. I'm trying to get around that by using a blade this time. First, by stepping down the primary bevel a 32nd at a time with the fin stock flat on the table. The diagonal will finish with the fin to the proper tapered surface. I've got a tenon jig that I can tilt just enough to take the fin from 1/8th at the root to 1/32nd at the tip. If that works, then I cut the leading and trailing edge angles. Their bevels are going to take a little more effort to set as the workpiece will be at both a lateral and vertical angle when it is run past the blade. Knife bevel calculators via Google are good for one plane at a time, combining them for 3D geometry is not what they were intended for. If the process works, each step gets repeated 8 times and I'll have a series of half fins. The pairs will get mated as a final step. Planning on skinning the bonded set with fiberglass to make sure the surface has a uniform finish for paint.
Some feedback would be appreciated. I'm expecting a few failed test pieces along the way but if someone can point out where I can improve the process before I start that would be helpful. Finding someone with a 3d printer or CNC machine to make them for me has already crossed my mind. That's plan B if scratch building my own doesn't work out. I figure this community has enough crazy and stubborn (read creative) minds to relate to wanting to make it on my own bench. Thanks.
