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Old 05-17-2013 | 10:20 AM
  #53  
Zor
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From: Ontario, ON, CANADA
Default RE: Correcting incidence


ORIGINAL: BillS

I hope to end up with incidence designed for the Kougar, Zero, Zero, Zero.

How I have been adjusting the incidence.

I use a short level and a Robert Incidence Meter and a bunch of shims under the wheels. First I disconnect the aileron linkage and clamp both to centered. I set the airplane wheels on the shims and level the horizontal stabilizer with the shims until both sides of the stabilizer are level and the same. I then tape the shims together as a set for each wheel. Then I check the incidence on each wing and make notes. I remove the wing from the airplane and shim the saddle with a short 1/2 " shim at the appropriate location. I put the wing back on and check the incidence on both sides again. The process is repeated until the incidence is very close. When close I slide soft balsa with glue in the gaps between saddle to wing. The soft balsa is sanded and the saddle gap is checked periodically.

I also have a set of micrometers and vernier calipers. Usually I feel funny measuring wood with a micrometer. Also it is easy to calculate angles from measurements which I usually do with props.

vicman is correct I fly mostly upright but believe that 4 degrees of prop down looked stupid. It also triggered obsessive compulsive tendencies.

Bill
Bill,

It is always nice to read how someone proceeds (method) to accomplish a task.

Complementing your post ___

My dinner table is flat and horizontal. I sit my model on it with the main gear touching the table surface; no shims under the wheels. I then use anything suitable to make the reference line parallel to the table surface. We may call those items "shims" if we like.

I then make my measurements to an accuracy of 1/64 of an inch and make my calculations.
Results are the incidence of the main wing(s) and stabilizer and the decalage between the main wings of a biplane or sesquiplane and the longitudinal dihedral (decalage of main wings to stabilizer).

Any commercial instrument should be checked for accuracy. Even voltmeters have variations.
Example: It is often useful to know that accuracy when measuring battery packs voltage to guess its degree of charge. I always have a laugh looking at a thermometer with a digital readout with one decimal ( 1/10 of a degree) when the degree digit is 2 or 4 degrees out of reality.

Best to you from Zor