Sunday, March 9, 2014

F-1201J Cowl Hinge – Don’t Come Up Short!

As the old adage goes … measure twice (in this case three times) cut once. Verify cut measurement … OK, measures good, job well done! This was the case when cutting the F-1201J upper cowl hinge. The finished hinge looks great, just like the drawing shows it and it measures perfectly … however, it is too short!
Here is the issue - my finger is pointing to where the F-1201J hinge cut to 25 1/2" as per the plans is not long enough to pick up the rivet hole adjacent to the access cutout on the F-1201H doubler.
Close-up of the F-1201J hinge not being long enough to pick up the rivet hole closest to the access port.

The Van’s drawing shown in the photo below, clearly shows barrels at both ends of the F-1201J hinge and the figure 2 detail clearly states the hinge length to be 25 1/2". However, that is too short … the F-1201J hinge needs to be approximately 26" which means the rivet hole closest to the access port will be in a flat spot adjacent to a barrel … NOT under a hinge barrel as shown on the drawing below.
Close up of the drawing that shows the F-1201J hinge installed … my finger pointing to the barrel as shown which is NOT how it works out in real life. Figure 2 shows the length to be 25 1/2" which is not correct … the hinge needs to be just shy of 26" so it clears the nutplate.

A visit to a couple of other builder sites reveled the right most rivet hole on the F-1201J hinge closest to the cutout port is indeed on the flat between hinge barrels and not under a hinge barrel. So the hinge was remade to just a little shy of 26" while mading sure the flat was where it needed to be.
Longer F-1201J hinge made to just shy of 26" with the flat starting at the nutplate adjacent to the cutout. The newly cut hinge is now clamped in position and ready to be match drilled.

As far as I can remember, this is the first measurement that has been given in the plans that has been incorrect … the drawing is even incorrect because technically a barrel can’t be above that first rivet if the hinge is aligned starting on the left side of the firewall as called for in the plans.

This is not that big of a deal and even if a builder does not extend the hinge, it would still work OK. But just wanted to give a heads up to builders so they can add the extra 1/2" to the hinge and not waste 25 1/2" of hinge material as I just did. Not sure at this point if I will need to purchase more hinge material or not … hope not.