CharlieWaffles
Well Known Member
There have been some threads I've read during my build discuss options for an alternate air door on the FAB other than the stock Van's door that can't be reliable reset without removing the lower cowl. Many builders have worked up a new door design that used hardware such as aluminum guides or delrin to provide a means to slide a door back and forth over an alternate air door. But these have all used additional hardware and weight. Dan Horton had commented an alternative would be to use fiberglass to provide these rails and eliminate the hardware. So I took that challenge.
I didn't like the round door provided by Vans as I wanted a door that could be opened and closed in flight. I was concerned that if I knew I had to remove the cowl to reset it, that I was unlikely to use it unless I had to. That meant it would be on the bottom of my list of engine troubleshooting. I wanted something that could be opened and closed and didn't present any additional items that could be ingested into the engine.
So I made up the fab with the standard approach and drilled a 2.5" hole in the bottom of the fab - towards the forward edge of the inside of the filter. This hole is slightly larger than the intake of the fuel injector body itself. I then made up a 3.5" wide by 4.5" long door out of .040" and a small joggle to be able to mount a push/pull cable end. I also made up a temporary 3.5" wide piece that was longer than the FAB.
I scuffed up the bottom of the FAB and waxed the long temporary aluminum piece and placed it over the alternate air hole in the FAB. I then laid up three layers of 9oz glass with a rough channel in the center.
Once cured, I removed the temporary aluminum piece and trimmed up the glass rails to be even and also ensure the alternate air door was unobstructed.
I fit the actual door in the channel created by the glass and verified the operation of the door. I used a #10 screw and an aluminum spacer to secure the push/pull cable at the same height as the cable nut.
Once verified, I painted the FAB out of vanity and mounted it and verified that the assembly worked as intended. I used the temporary long door to mask the channel from the paint so it didn't cause the channel to bind on the door after painting.
I didn't like the round door provided by Vans as I wanted a door that could be opened and closed in flight. I was concerned that if I knew I had to remove the cowl to reset it, that I was unlikely to use it unless I had to. That meant it would be on the bottom of my list of engine troubleshooting. I wanted something that could be opened and closed and didn't present any additional items that could be ingested into the engine.
So I made up the fab with the standard approach and drilled a 2.5" hole in the bottom of the fab - towards the forward edge of the inside of the filter. This hole is slightly larger than the intake of the fuel injector body itself. I then made up a 3.5" wide by 4.5" long door out of .040" and a small joggle to be able to mount a push/pull cable end. I also made up a temporary 3.5" wide piece that was longer than the FAB.
I scuffed up the bottom of the FAB and waxed the long temporary aluminum piece and placed it over the alternate air hole in the FAB. I then laid up three layers of 9oz glass with a rough channel in the center.
Once cured, I removed the temporary aluminum piece and trimmed up the glass rails to be even and also ensure the alternate air door was unobstructed.
I fit the actual door in the channel created by the glass and verified the operation of the door. I used a #10 screw and an aluminum spacer to secure the push/pull cable at the same height as the cable nut.
Once verified, I painted the FAB out of vanity and mounted it and verified that the assembly worked as intended. I used the temporary long door to mask the channel from the paint so it didn't cause the channel to bind on the door after painting.