Astro-Hog Incidences ?
06-30-2007, 03:42 PM
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Astro-Hog Incidences ?
Just finished covering a Sig Astro-Hog that I got from a friend that worked on it a little for 10 years. I bolted the wing on to take a couple of pictures for my friend and then decided to check incidences with my brand new Robart incidence meters. Tailplane was +1 1/2 (+ 1 1/2 recommended) and the wing is +4 (+2 1/2 recommended). I need to make an adjustment to the wing obviously. But wait a minute !! This design dates from the 50's no? The engines were low power and heavy then. I'll be flying a new Saito 72 on this plane. It'll be a tail dragger and the LG will be mounted on the fues in front of the wing rather than using the wing mounted LG wire.
Question-- Since I have to reduce the wing incidence anyway, wouldn't +1 1/2 make more sense than +2 1/2??
Question-- Since I have to reduce the wing incidence anyway, wouldn't +1 1/2 make more sense than +2 1/2??
06-30-2007, 06:29 PM
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RE: Astro-Hog Incidences ?
With neutral trim, the plane will just have to fly faster.
Incidence is set at the angle that gives the lowest drag for that airfoil. The tail incidence corresponds to the downwash angle behind the wing. Unless you know the airfoil's properties better than the designer, it might be best to set it up as it was designed.
Incidence is set at the angle that gives the lowest drag for that airfoil. The tail incidence corresponds to the downwash angle behind the wing. Unless you know the airfoil's properties better than the designer, it might be best to set it up as it was designed.
06-30-2007, 06:37 PM
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RE: Astro-Hog Incidences ?
Turning out to be tougher than I thought. A LOT of cutting and shimming to get it down to +3. So I'll probably stop at +2 1/2 anyway.
07-01-2007, 12:00 PM
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RE: Astro-Hog Incidences ?
Decalage is the difference between the tail and the wing. You will end up with 1 degree between the tail and wing. Will this be enough?
07-01-2007, 12:26 PM
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RE: Astro-Hog Incidences ?
The plans call for +1 1/2 on the stab and +2 1/2 on the wing for a difference of +1. It took a pair of 1/4" blocks in the saddle to get from +4 down to +2 1/2, the stab is at +1 1/2 with the centerline leveled with a bubble level.
I have two incidence meters so I don't have to move one back and forth. Hard to believe the saddle was cut so deep as to be off that much. I didn't build the wing, an engineer did, and you know how picky those guys can be.
No matter how many times or how many places I check it I still get the same answer. I just wondered if anyone else has encountered the same thing with the Astro-Hog. Not that very many people build craftsmen's kits anymore.
I have two incidence meters so I don't have to move one back and forth. Hard to believe the saddle was cut so deep as to be off that much. I didn't build the wing, an engineer did, and you know how picky those guys can be.
No matter how many times or how many places I check it I still get the same answer. I just wondered if anyone else has encountered the same thing with the Astro-Hog. Not that very many people build craftsmen's kits anymore.
