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Building Tips and technical articles. => 1/2 A building. => Topic started by: David Barber on July 18, 2012, 04:52:02 AM

Title: How to Balance a 1/2A size plane.
Post by: David Barber on July 18, 2012, 04:52:02 AM

Hello Guys and Girls.

I have built a Sig Skyray and Sig Derwybird,
How do I go about balancing these little birds, I have a Great planes balancing machine, but it states no plane under 2 pounds.
Whats the balance point for the derwybird? cannot find it on the plans.
I am new to this hobby so any help would be great.

Thanks, David.

Title: Re: How to Balance a 1/2A size plane.
Post by: Bill Heher on July 18, 2012, 05:02:33 AM

On 1/2 a profile / plank wings like the Dewey Bird and Skyray the front lead out is a good starting point.
They usually come out nose heavy, but they will fly fine if a bit nose heavy, and adding lead to the tail to balance them just adds extra weight that doesn't really make them fly better - just heavier.

Title: Re: How to Balance a 1/2A size plane.
Post by: kenneth cook on July 18, 2012, 05:15:48 AM

              David, one thing to be aware with on the Skyray is that they build tail heavy. Bill stated above that most come out nose heavy. This is generally the case with the exception of the SKyray.  The plane will turn quicker than you would expect and things can get pretty touchy. This usually ends up in a loop that breaks the nose off of the plane right at the front of the wing. Ca will put this back on and until you do it approximately another 4-5 times, you get the balance point correct. I don't know if you built it yet or your just asking, but putting a 1/32 ply doubler on the fuse extended back onto the wing about 1-1/2" would certainly be a good idea. The Skyray flies quite well. Keep your pushrod at first in the innermost hole on your bellcrank. The Sig control horn is extremely small. Although it works, a Dubro horn would give you some adjustability over the Sig horn. The Sig horn uses one screw that usually ends up allowing the horn to turn rather than staying put. It also has a tendency to crush into the wood. I always wanted to omit the triangular nose block on the outboard side of the fuse and install a Perfect tank due to the short runs of the Black Widow reedie. The Black Widow is a terrific powerplant coupled with a 5x3. The plane flies better than you would think. Ken

Title: Re: How to Balance a 1/2A size plane.
Post by: Jim Thomerson on July 18, 2012, 06:26:49 AM

A 1/2 stunt airplane will fly well with the CG anywhere from the leading edge back to at most 10% MAC.  The bad reputation of 1/2A airplanes is, in part, due to people balancing them like a big stunter.

Title: Re: How to Balance a 1/2A size plane.
Post by: David Barber on July 18, 2012, 02:45:44 PM

Thanks Bill.Jim and Kenneth,

lots to think about, and a few ajustments needed.

Title: Re: How to Balance a 1/2A size plane.
Post by: Bill Heher on July 18, 2012, 11:04:02 PM

Just remember, Nose heavy planes fly sluggish - Tail aheavy often only fly 1  time!