Monday, December 14, 2015

FF-1207 Air Shroud - Fitting Begins In Earnest

The last couple of work sessions have involved playing around with fuel tank sealant so have not taken any photos. Basically, the drip trays for the Rotax engine’s carburetors have been sealed and the mechanical fuel gauge was installed in the fuel tank. Time was also taken to apply the fuel sealant to the junction of the instrument panel and longeron per the plans along with sealing the firewall and fuselage seam. This work was done because we have been having warm nights so the tank sealant will cure properly after a couple of days. Of course, the fuel tank and drip trays were placed in the hot box and should cure much quicker.

While the tank sealant was curing, work resumed on custom fitting the FF-1207 air shroud onto the Rotax 912 engine. The shroud was set in position per the plans and areas of interference were marked with a pen and then the fiberglass was removed. After a few cycles of this the air shroud was beginning to fit snuggly.
FF-1207 air shroud is beginning to fit nicely … at this point it needs to drop down approximately another inch but is hitting the engine case where I'm marking with a pen.

A revelation: Thus far, all the cutting was done as suggested in the Van’s instructions …  place the air shroud on the engine and marking where the fiberglass needed to be cut away, cut and then repeating the process as the shroud lowers downward onto the engine. I was always hand filing from outside where the pen marks were placed on the air shroud. At some point I flipped the air shroud upside down and while wiping fiberglass dust off the air shroud discovered the dust illuminated what appears to be a fine scribe line in the fiberglass. Interestingly, Van’s instructions made no mention of trimming to a scribe line, they just said to trial fit, mark with a pen and remove the fiberglass and repeat the process until the desired fit is achieved. I’m thinking this is another case where the instructions have not caught up with the part. This air shroud is a second generation … in that, it has had one corner modified from the original version to make access to one of the motor mount screws much easier. I’m guessing when the mold was re-worked, they added the scribe lines but forgot to tell the builder of the change.

Scribe lines can barely be seen on the inside of the FF-1207 air shroud - these will come in handy and appear to be about right.

So far, the vertical scribe lines appear to be about right … will take my time and sneak up horizontal lines but at this point they also appear to be about right … if not I’ll return from the future and edit this post. Unfortunately, I discovered this at the end of the work session … but the marks will make tomorrow’s session much easier.