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My landing gear is behind the CG...Help!

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Old 11-07-2005, 12:19 PM
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no1speshal
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Default My landing gear is behind the CG...Help!

Hello All,
I am building an airplane somebody gave me. It was just a fiberglass shell fuselage and a foam core, balsa coated wing when I got it. Since then, I have installed a servo tray inside, and mounted all the servos, minus the ones in the wings. My problem is different than what I have encountered in the past though. The wings had rails already installed for wire gear. So, when I put gear in the supplied openings, the airplane will not sit on the tail wheel. To add insult to injury, it is balanced right now at around 25-30% mac, so it does not need to be any more tail heavy, at least until after the first flight.

So, here is my question: What should I move; the CG or the gear? Or, should I add more weight to the tail to get it to sit on its tail wheel? I am kind of mistified here. I have built a lot of airplanes but seldom from other people. I usually build them from scratch and I take care of all of this when I am building. Therefore, this is the first time anything like this has been facing me on the building board.

As far as what equipment I have in the airplane, I have an old Super Tigre .91 up front (that is kind of heavy, but the airplane is about 90 size from what I can calculate. The configuration of the plane lends me to believe it is a pattern plane, but there are no indications of it anywhere.

Can someone please help me muddle through this? I am hoping I can rely on you all and your exerience to figure this out for me. Meanwhile, it will sit on the bench until further notice. If it would help anyone, I could post a picture of it on here for your examination. Thanks in advance for your help.


Red
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Old 11-07-2005, 12:39 PM
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Default RE: My landing gear is behind the CG...Help!

if they are wire, just bend them forward.... you want the gear raked forward.... usually trying to get the axle even with the LE...



a picture would help
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Old 11-07-2005, 12:44 PM
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Default RE: My landing gear is behind the CG...Help!

<snip>...it is balanced right now at around 25-30% mac, so it does not need to be any more tail heavy, at least until after the first flight.

So, here is my question: What should I move; the CG or the gear? <snip>
What kind of plane? Sounds like it's set up for tricycle gear.

Best wishes,
Dave Olson
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Old 11-07-2005, 12:48 PM
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Default RE: My landing gear is behind the CG...Help!

ditto sounds like it may have been a pattern type which usually are set up as trike gear.
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Old 11-07-2005, 12:59 PM
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Default RE: My landing gear is behind the CG...Help!

I will have to try to rake the gear forward. I did not think it was a tricycle config gear assembly because it was a solid epoxy and fiberglass shell, from the nose to the tail section. The only cut outs were on the underside where the wing and fuel tank go and a small opening for an engine on the side. There was a motor mount epoxied in place too, on its side. So, since there were no gear points in the front, I made it a tail dragger. It did have a nice flat spot in the tail to accomodate a tail wheel, so I concluded that was what it was set up for.

Thanks for the suggestions though. Are there any other things I can do? As it is, it will never taxi. So, I will have to do something prior to flight. As far as the gear rake is concerned, the gear rail that I was telling you about, that is right at about 5 inches aft of the leading edge. The wing chord is 13 inches. Needless to say, that will be a hell of a rake! Is there anything else I should consider before I do that?

Thank you all so far for the comments and ideas though. I really appreciate your help.


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Old 11-07-2005, 01:58 PM
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Default RE: My landing gear is behind the CG...Help!

Can you mount the gear on the fuse? Maybe by adding some internal reinforcement near the wing leading edge in the fuse, you could mount the gear on the fuse ala PiperCub style.
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Old 11-07-2005, 02:10 PM
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Default RE: My landing gear is behind the CG...Help!


ORIGINAL: no1speshal

I will have to try to rake the gear forward. I did not think it was a tricycle config gear assembly because it was a solid epoxy and fiberglass shell, from the nose to the tail section. The only cut outs were on the underside where the wing and fuel tank go and a small opening for an engine on the side. There was a motor mount epoxied in place too, on its side. So, since there were no gear points in the front, I made it a tail dragger. It did have a nice flat spot in the tail to accomodate a tail wheel, so I concluded that was what it was set up for.

Thanks for the suggestions though. Are there any other things I can do? As it is, it will never taxi. So, I will have to do something prior to flight. As far as the gear rake is concerned, the gear rail that I was telling you about, that is right at about 5 inches aft of the leading edge. The wing chord is 13 inches. Needless to say, that will be a hell of a rake! Is there anything else I should consider before I do that?

Thank you all so far for the comments and ideas though. I really appreciate your help.


Red

Just install a nose gear and you will be good to go! If the main gear is 5” back it is setup for trike gear. Shouldn’t be a big problem to do and will be worth while.


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Old 11-07-2005, 02:19 PM
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Default RE: My landing gear is behind the CG...Help!

How about a picture.... Leave the tail wheel and add the trike forward wheel if you can figure a mount. Can the wing be repositioned on the fuse? (Not much help moving the CG as you move the gear as well which is positioned at or aft of MAC)

So much for gifts, prior owner may have already figured out it was a big problem before he gifted it away!
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Old 11-07-2005, 02:49 PM
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Default RE: My landing gear is behind the CG...Help!

It seems to me that 5" behind the LE of a 13" wing is way too far back for a taildragger (See Pic 1)

If the plane were meant to be a Taildragger, the LG Blocks would be in the 2 to 3" range, Not 5"

Check the engine mount. I'd be willing to bet that there is a hole drilled through it for mounting a nose wheel (See Pic 2)
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