Horizontal Stab

[DBeaulieu]

For you other Q/B Patrol builders...did you have to trim much on the bushings that are used on the front stab bracket to set the negative 1 degree angle of incidence relative ot the level datum on the fuselage? Currently I'm measuring a negative 1.8 angle and wondering what to do to correct. File down the bushings, fab new ones, not worry about it. Any thoughts appreciated!

Dave (from Maine)

[Ed Welfred]

Dave those small vertical tubes are there for adjustment. Shorten them to get the horizontal stab to the 1 degree that is required.

Ed

[DBeaulieu]

Ed Welfred Thanks Ed...will continue working on it! Appreciate the response.

[Pbruce]

I just finished setting up the stab. I found that no bushings were required, although some were provided. I was suspicious of my work but it was accomplished with the aid of someone who has built a Patrol from scratch. Then my son and I did it again with the same result. The stabs were about 1/4 of a degree out relative to each other (1* and 1.25* respectively) so I will be inserting one thin washer under one stab. It looks like that’s all that’s required to match them at -1.25*. Either that or I could file one of them for 1* exactly, but I’d rather not. Mark G mentioned that some of the earlier kits had a different sized tubing on the stab spar and leading edge, and the bushings could be for that. My tubes are the same diameter.

You asked about elevator weights. I calculated the weight of Stewarts system required for the elevator at one pound of fabric, glue, and paint. I hope I’m right. I then set a pound of butter mid-chord on the elevator and it still falls slightly horn-down. I’m told this is not rocket science so I’m calling it good as supplied. My kit is #65, produced in late 2019.

Also regarding the elevator, The holes drilled in the elevator horn halves are not exactly the same. If I bolt them together as-is, the elevator hinges bind slightly. I’m not sure whether to run a 3/16 reamer through and hope that bolting the horns tightly together is adequate, or if I should re-drill to 1/4”. Incidentally I have about 1 degree less elevator throw than specified in each direction. I can however adjust the elevator pushrod to get full travel in one direction at the expense of two degrees less travel in the other. I split the difference and called it a day.

[DBeaulieu]

Pbruce Thanks for the reply, I filed my bushings down and got -1.4 and -1.5. Will likely go at them again to bring them closer to the plan spec of negative one. My tube dia for the stab attach are the same. My elevator went on well, though I had a bit of interference of the horn sides with the fuselage tubing at full travel (cannot recall full aft or forward on the stick) which I resolved with a tiny bit of grinding work on the horns. I'm planning Polyfiber process for cover and will figure out balance later this year. Couldn't get anything definite out of Bob Barrow WRT a range of allowable weight variance from neutral when balancing which I understand is typically given for other production aircraft.

[DBeaulieu]

Adjusted bushings on horizontal stab attach bracket to set angle of incidence. Iterative process from original angle of 1.8 negative. Negative 1.1 now and close enough. Refreshed hardware and called it good.
horizontal stab angle of incidence releative to level datum right side.jpg horizontal stab angle of incidence releative to level datum left side.jpg

[jaredyates]

This is something you can fine-tune once you are flight testing. Load up to the configuration that you want to be most efficient for, then establish a cruise speed that you like the best. Look back at the elevator and see if it is in trail with the stabilizer or deflected, and adjust the incidence if it is deflected.

[DBeaulieu]

jaredyates Thanks, that's a good tidbit of info right there!