One of the most important elements to good flight is equal wing incidence. Without good alignment the two wings will fight each other and keep you from achieving perfect trim.
If you consider that the Hobie Hawk was the first mass produced ARF and RTF kit in the RC world it is amazing that the production quality of the originals was as good as it was, but then Again, Hobie Alter was the master of these processes. Occasionally however, there may have been a shaving or whatever in the jig holding the wing when the wing rod and incidence pin holes were drilled. Add to that the roto-molded poly nose cone had to hold the wing pin and incidence sleeves just perfect and again be held perfectly in the jig when bored to get perfect alignment. One misalignment and your plane would never fly straight because the wings had different incidence... all the more critical in a rudder elevator ship with no ailerons to adjust for level flight.
The Hobie Model Co.'s method (pages 16 & 17 in the Hobie Hawk Manual) is to drill out and reset the wing rod or incidence pin... a task I personally would rather avoid. My solution is just as effective and takes far less time. I will show you how to make a "dogleg" wing incidence pin that will correct for a misaligned fuse or wing.
CLICK ON THE THUMBNAILS TO ENLARGE:
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First, suspend your Hawk on some flat parallel blocks by the wings so that the fuse' does not touch. Place the blocks near the first rib. I used small square "rails" to set this Hawk on. You want to be able to lay the wings flat across the blocks. |
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Looking directly from behind, you can see that these particular wings do not have the same amount of incidence. It does not matter if the misalignment is a wing, or the fuse, the following process will correct it. |
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I always choose to match the two wings by tipping which ever wing's leading edge downward. I pick the wing that must be tipped down in front so I have room to properly countersink/carve away some material that will allow for my dogleg incidence pin. I countersink drill the incidence brass sleeve a little more than 1/8". This is a custom made wing, but the same applies to a stock Hobie wing. You will need to grind a little material from the to side of the root around the tube. |
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Here is an incidence pin with a "dogleg" bent into it. The bend is just outside the fuse 's incidence tube. I make the bend as "short" as possible because the longer the distance between the dogleg bends the deeper you have to countersink the incidence tube in the wing. |
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Here is the dogleg incidence pin partially inserted. It's funny, almost without fail, all the Hawks that have been off are almost exactly the same... about 2 degrees. Maybe that same piece of crud was in the drilling jig for a few days!!?? 2 degrees is about one incidence pin thickness. |
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Now back on the alignment blocks you can see the wings are now equal in incidence. All you have to do now is check wing tip washout!.... and that's for another page!... |
