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Yes, another Kougar CG question!

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Yes, another Kougar CG question!

Old 05-09-2021, 01:24 PM
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Hortco
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Default Is anybody currently flying a Sig Kougar?

Ok guys- I’ve read a million Kougar CG posts and I know it is 1/2 inch from the LE of the wingtip BUT do you hold the plane upside down to balance it or right side up because it balances differently upside down than right side up.
PLEASE ONLY REPLY IF YOU ARE FLYING A KOUGAR because
everybody’s gonna say “1/2 inch” or “check the plan or manual” or “I had one that flew great but I don’t know the CG” or talk about how planes are balanced in general.
ALL I WANT TO KNOW IS DID YOU BALANCE YOUR KOUGAR AT THE WING TIPS WITH THE KOUGAR UPSIDE DOWN OR RIGHT SIDE UP.
IF YOU ARE NOT FLYING A KOUGAR DO NOT RESPOND!

Last edited by Hortco; 05-10-2021 at 03:17 AM.
Old 05-09-2021, 05:03 PM
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Top_Gunn
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The balance point is the same whether the airplane is right side up or upside down. But almost every airplane will be easier to balance one way or the other. High-wing airplanes are almost always easier to balance right side up; low-wing airplanes upside down. Try it both ways. One way will be easier to get the model to balance steadily than the other. Use the balance point you get when balancing that way. The difference you think you are measuring is almost certainly due to your not having the airplane exactly level with one or even perhaps both of your methods. While it doesn't work for all models, a plane like the Kougar will probably be level when the stabilizer is parallel to the floor.

Old 05-09-2021, 06:40 PM
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speedracerntrixie
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The reality is just get it close and then adjust according to how the airplane is flying. This applies to every airplane. There is nothing different about a Kougar that requires some sort of magical CG. If you are really interested in dialing it in I would be more then happy to get more specific but it will require several hours of work. If you are willing to rework a few things.

The first step of course is to get the CG right. The flight test for that is to pull to a 45 degree climb at full throttle and roll inverted. Watch what the airplane does hands off. If it holds the inverted 45 degree line you are a tad too aft. If it steepens the line you are way aft and it will most likely be too sensitive on the elevator as well. What you are looking for is about a 5 to 7 second arc to inverted level. Since you most likely have the wing set at zero degrees incidence it will most likely be closer to 5 seconds due to the up elevator trim you need to dial in to get the required positive AOA on the wing to trim out in level flight. With this CG position adjust the elevator throw and expo to suit the sensitivity you like. Never adjust CG to reduce pitch sensitivity once you have the CG set as per above.

In reference to the few hours work I mentioned earlier. The plans have you building the airplane with everything set to zero if I am not mistaken. Many sport and pattern airplanes of that era were. A better setup would be the engine set to zero up or down thrust but a tad of right. The wing set to 3/4 positive degree and the stab at zero. This way the wing has its positive AOA to generate lift and the fuselage is level and the need for up trim is eliminated. This makes knife edge, inverted and vertical much easier. Without the positive incidence all of those will pull to the canopy.
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Old 05-10-2021, 03:24 AM
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Hortco
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I really just wanted to know if you should balance it upside down or right side up at the wing tips (1/2 inch back from the LE)
Old 05-10-2021, 04:30 AM
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speedracerntrixie
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I hope you get your answer, not sure how many guys there are out there flying a 40 year old design. Sig does still sell them so maybe.
Old 05-10-2021, 09:45 AM
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I think the simplest answer to your questions is to balance your Kougar inverted. As a low-wing, the bulk (virtually all) of the model's weight is above the balance point on the wing. thus it would be unstable. Imagine balancing a baseball bat supported from the bottom -- it's only tenuously stable when the CG is directly above the support point. Now turn it over and let it hang -- the CG will be exactly below the point of support and the arrangement will be completely stable.

That said, have you looked at the various Vanessa threads? I find it much easier to balance any reasonably-sized model on this type of rig than any other and you don't have stability problems inverted our upright.

Ken
Old 05-10-2021, 11:57 AM
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Top_Gunn
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Yes, I should have mentioned the Vanessa rig myself. I use one for large models, though for a Kougar fingertips should be OK.
Old 06-10-2021, 12:31 PM
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Hortco, I balanced mine right side up at the wing tips. It flies well at this point but it is a little nose heavy at 1/2 back from the leading edge.
Old 06-10-2021, 04:49 PM
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Make a Vanessa rig for it. When that's done, draw a line from wingtip to wingtip and mark it next to the fuselage. Balance it at that point with the vanessa rig. At that point, it's going to be a little nose heavy and will land a little fast. After you get comfortable with it, start sneaking the cg back a little at a time until it lands like a Kadet Sr., just like what it says on the box. That's how I did mine. Absolutely incredible flyer and lands like a trainer when it's set up correctly.

carl
Old 06-14-2021, 01:52 PM
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jaka54
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Hi!
I just hold my two index fingers under the wing (not inverted) , close to the fuselage . Have done so for the last 46 years on every plane I´ve got . After the first flight I alter the C of G if that is needed.The rule for setting up every R/C plane is: Always go for as small elevator trow as possible and the C of G as rearward as possible.

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