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Carl Goldbert Ulimate 10-300 Kit Balancing Procedure

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Carl Goldbert Ulimate 10-300 Kit Balancing Procedure

Old 12-28-2019, 10:14 AM
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mirwin
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Default Carl Goldbert Ulimate 10-300 Kit Balancing Procedure

I recently became the owner of a well-cared-for and lightly-used Carl Goldbert Ulimate 10-300. It was built from the Goldberg kit; it is NOT the ARF.

Although the OS 1.20 Surpass III four stroke looks like new it was gummed up from disuse so badly than the engine wouldn't turn over. I completely disassembled and cleaned the engine and it now runs perfectly on the bench.

I'm nearly ready for a test flight, but I must first balance this model. But I'm not sure of the specific balancing procedure for it.

I have the original construction plans so I know exactly where the CG is but the plans show the CG ONLY on the lower wing. The plans and the other Goldberg info that came with the kit surprisingly says nothing about the specific procedure.

Ive had three biplanes and on all, the instructions said to balance those planes at the bottom of the upper wing (with plane upright). However, on this Ultimate the original owner marked the CG on the bottom of the lower wing, and not the upper wing. The original owner, who has not flown in some years, doesn't remember the correct procedure.

Can anybody who is familiar with this particular kit-model tell me for certain if I am to balance the plane from the upper wing, or the lower wing.

Thanks much.

Old 12-29-2019, 07:06 AM
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Yup. Balance that pup by it's upper wing. Just draw a straight line from the CG on the plans from wherever it is to the bottom of the top wing. That is the CG at the center of the top wing (roughly 1 1/2" behind the spar). Strike a straight line on the underside of the top wing that is perperdicular to the center rib. Now just pick it up and balance with your fingers on that line. I have one of these myself with a Supertigre .90 in it. Mine was very tail heavy. I had to pour lead shot and epoxy in the front of the cowl to balance it.

carl
Old 12-29-2019, 09:24 AM
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mirwin
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Many thanks, Carl. You've confirmed everything I was thinking.

Mike
Old 12-30-2019, 08:21 AM
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daveopam
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You got good advice on the balance. I would add that the Goldberg Ultimate will fly well behind the stock CG. I owned several of these. One of my favorite planes of all time. After you get it in the air. Ease the CG back if it lands quick or bounces on landing. Flat spins with an AFT CG are a blast. Just be careful doing a blender. I broke the mounting lugs out of the fuse on one doing it.

David
Old 12-30-2019, 06:50 PM
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Much thanks, David

You're the 4th flyer / builder to confirm my experience. I received no answers contrary to this. Tomorrow, I'll do the final engine test, and then I'll put the wings on and balance it.

I've flown two of these Goldberg Ultimate kits, all belonging to friends, and I agree they're great aerobatic planes. I'm happy to have this one.

Happy New Year
Mike
Old 01-02-2020, 03:52 PM
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daveopam
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Best of luck Mike! One final word of advice. These planes fly great when heavy but dead stick is another story. Even with a 90 2stroke biplanes glide terrible. With the big 1.20 up front it's a different ballgame. Look for a place to land RIGHT NOW if it dies. Do not try and glide it unless you are 500' up. On the plus side, they don's tip stall and will come down flat but the pants go right through the wing.

David
Old 01-02-2020, 05:58 PM
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mirwin
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Dave, thanks.

My (Pica) Waco YMF-3 is a floater even with the engine at idle.. The Super Skybolt (kit) was a sinker without that funny thing on the front of the engine going round-and-round really fast. I once had a Goldberg Ultimate (kit) engine die on me. Based on those experiences, I always fly my biplanes at a higher altitude than my other planes. It also helps that our club runway is 834' long so I don't have to worry too much about running out of room if I bring in a biplane dead-stick and hot.

This 15 year old model is now ready for a test flight as soon as the weather breaks.

Mike
Old 01-07-2020, 08:42 AM
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Originally Posted by daveopam View Post
Best of luck Mike! One final word of advice. These planes fly great when heavy but dead stick is another story. Even with a 90 2stroke biplanes glide terrible. With the big 1.20 up front it's a different ballgame. Look for a place to land RIGHT NOW if it dies. Do not try and glide it unless you are 500' up. On the plus side, they don's tip stall and will come down flat but the pants go right through the wing.

David

WORD!

Lost mine due to the throttle arm coming loose and the throttle closing. No altitude and a hard tail wind meant it came down fast and hard.

I balanced mine upside down, doesn't really matter on a Vanessa rig as long as the tail and wings are level. It flew great up until it could fly no more. Someday I will need to dig up the pdf of parts someone sent me and get them into Coreldraw so I can cut them out on the laser and rebuild the Fuse.
Old 01-09-2020, 05:09 AM
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jescardin
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I own a RTF one and I also bought it second hand.

Mine also was marked on lower wing and, as per instruction manual and "acdii" coments above, I always check balance with model upside down:

gbga1053-manual.pdf (see page 28 "Balancing the Model")

Best Regards
Old 01-09-2020, 07:49 AM
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Either will work, the goal is to get the center of mass below the pivot point so that you a pendulum. If done in reverse the plane will flop to either side of the pivot point.
Old 01-09-2020, 08:46 AM
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Yep, can work either way for a Bipe. My Liberty Sport, since the CG point is located on the upper wing, I balance it upright, but if the CG is located on the bottom, according to the plans location, I balance it upside down.



Balanced perfectly


It would be difficult to balance that plane upside down due to the CG location and the wing type, but the 10-300 is easy to balance upside down. A lot also depends on what you are using to balance it with. The rig makes balancing any plane easy peasy as long as you know where the balance point is.
Old 04-13-2020, 02:38 PM
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equip
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Hello would this top wing balance procedure work with the Goldberg Bucker Jungmann I'm just about finished with my jungmann what do you think.
Old 04-23-2020, 12:42 PM
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Originally Posted by equip View Post
Hello would this top wing balance procedure work with the Goldberg Bucker Jungmann I'm just about finished with my jungmann what do you think.
Of course!
But you have to keep with Jungmann manual C.G. position.
Best Regards and Keep Safe

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