I would really find it pretty much impossible for you to make a mistake on how the firewall is placed and it relation to F1. To be honest I wouldnot trust the meter especially since it is all CAD drawn and laser cut. Here are some pictures of the CAD files showing the upthrust amount, right thrust, and even tail incidence.
So on the pictures you will see that there is 2 degrees up thrust verified by both fuse sides, 3 degrees right thrust, 1 degree positive incidence on the tail (which brings the tail up when flying and it looks level), and then the final picture actually shows you the measurements that the firewall is from the front of F1 (this is the left motorbox side).
Kevin
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According to your image showing the cad drawing with measurements, Top measurement of 2.7433 inches is equal to just under 2-3/4 inches or
69.67982 mm (millimeter)
Bottom measurement of 2.8429 inches is equal to just barely under 2 53/64 or more accurately, 72.20966 mm.
As with the firewall being "keyed" to the fuse sides and impossible to assemble incorrectly, it is equally impossible to get the "F1" former assembled incorrectly as it too is "keyed" or locked into the fuse sides.
Top of firewall measurement is 1/16" under what it is supposed to be. Or, 1.5875 mm.
Bottom measurement should be 2.8429 inches or in fraction, just barely under 2-27/32". More accurately measured at 72.20966 mm. As seen in the photo, the bottom firewall measurement is precisely 2-15/16 inches. More accurately measured at 74.6125 mm. For a difference of 2.40284 mm. Added to the top 1.5875 mm., that becomes 3.99034 mm difference from what the actual thrust "should" be. Nearly 4 mm difference. 4 mm is equal to a decimal reading of 0.15748 or in fraction form, right between 5/32 and 11/64 inches.
To me, this does not seem like a lot. In fact, negligible. But when translated through the distance of the firewall to the prop hub, (approximately 7-9/16") that could account for "some" of the extra "up" thrust encountered when attempting to mount the engine. I really am too tired to calculate the angle proximity difference between what the thrust "should" be and the end result of the angle of the firewall. At the length of just under 8 inches, I don't know precisely how much difference 4 mm at the firewall would make in relation to degrees of thrust angle. However this is in part why I chose to account for the extreme up thrust in the firewall and set the angle of the engine as I have.
All the pitts have 2 degrees up thrust in them.
By your cad drawings and calculations, the 2 degrees of "up" thrust is achieved with your measured angles. How much difference in degrees does the extra 4mm make in thrust angle? 0.225 degrees at the firewall??
