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Plane is EXTREMELY Tail Heavy!

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Old 05-12-2018, 11:52 AM
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Jack_K
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Default Plane is EXTREMELY Tail Heavy!

I got a Great Planes Super Sportster 46 size low wing at a garage sale. It has an OS 46FX installed, all servos installed, and the battery is located beneath the fuel tank. Light weight Spektrum AR6210 receiver just behind the tank. No obvious things that might make it so tail heavy.

According to the manual I downloaded, the CG is 3-1/8" aft of the leading edge. In order to balance it there would require 14 ounces of weight just behind the firewall. That's an awful lot of lead! I doubt there's room for that much anyway.

Any suggestions (other than using a 61FX)?

Jack
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Old 05-12-2018, 12:59 PM
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The first thing I would do is put on a HEAVY HUB.. and then any more weight you need to add should be as far forward as possible.. Also check to see there isn't some lead or something on the tail for some crazy reason.. Also some tail wheels are fairly heavy and you might be able to add a light foamie one instead.


Sometimes they just get built heavy !
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Old 05-12-2018, 08:19 PM
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I would be tempted to see if the engine could be moved forward, rather than adding weight...even if it meant making a new cowl or extending the fuselage to use the existing cowl. I can't see how it could be built with wood so heavy in the tail feathers that it would need that much lead up front to balance. what does the plane weigh, with engine mounted, right now ?.
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Old 05-16-2018, 02:16 PM
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Default Got it balanced

I used the heavy brass "spinner" nut inside a 3" spinner. It balanced. It weighs 6 pounds and 1/2 ounce. I think the 46FX will fly it. If not, I'll use a 61FX.
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Old 05-17-2018, 05:11 AM
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r ward
 
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6lbs-1/2oz. is fine for a .46, it should have no problem at all. I have yet to build a plane and have it come out at or even anywhere near what the kit or plans say it should weigh. for me it is so common that I have a feeling the weights listed are without engine, but they don't tell you that just to make their plan or kit look better. it seems that I always come out somewhere around the weight of the engine over what is advertised for the plane. I always try to "build to balance", eliminating the need for added weight. usually,.... I can come pretty close just by moving the engine ahead or back a bit without seriously affecting flight moments. the worst case I've ever had was my .46 size high wing coroplast trainer. it came out pretty tail heavy and I had no choice but to add a lump of lead to the nose. it now weighs 6lbs.-8oz. but it flies just fine with a 17.5 oz./ft wing load. I've noticed that a lot of the coro designs come out tail heavy. if you look closely at them, you'll notice that they look short coupled between wing and tail feathers and a little long nosed. I think the designers move the wing back on the prototype fuselage "after the fact", so to speak, to get the balance where it should be eliminating the need for adding large amounts of weight.
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