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CG = Wheels Up or Down?

Old 06-24-2013, 02:32 PM
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Corsair2013
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Default CG = Wheels Up or Down?

Quick question - do you balance your plane with retracts UP or Down?

I have Hangar 9 F4UCorsair 50 and new retracts. Book shows gear down but is that due to fixed gear?

Thanks

Semper Fi

Keith
Old 06-24-2013, 02:50 PM
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dasintex
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Default RE: CG = Wheels Up or Down?

I have always balanced my Warbirds with the Gear Retracted(up)!
Old 06-24-2013, 02:57 PM
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Corsair2013
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Default RE: CG = Wheels Up or Down?

With the gear down is your plane nose heavy?
Old 06-24-2013, 03:16 PM
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eddieC
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Default RE: CG = Wheels Up or Down?

I would think there's very little change between extended and retracted. If there is a difference, use the position which will allow the CG to move forward when cycled.
Old 06-24-2013, 03:29 PM
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Default RE: CG = Wheels Up or Down?

Gear up is how you will fly it so gear up for balance.
Old 06-24-2013, 03:45 PM
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Default RE: CG = Wheels Up or Down?

I had a DC F20 Tiger shark that had quite a variance between up and down so it can and does happen.

I believe they show and want planes balanced gear down because the gear is down when your going low and slow.
Having the wrong CG low and slow can be disastrous whereas at altitude and at speed is most likely a trim issue.
Old 06-24-2013, 04:25 PM
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ARUP
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Default RE: CG = Wheels Up or Down?

Do both and make sure the balance point stays in the 'safe' ranges. Better a little nose heavy than tail heavy.
Old 06-24-2013, 05:01 PM
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DavidAgar
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Default RE: CG = Wheels Up or Down?

Wheels up is the best way. Good Luck, Dave
Old 06-25-2013, 05:33 AM
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Default RE: CG = Wheels Up or Down?

I vote for checking the CG both up and down for a good baseline . Start with the CG slightly nose heavy for the worst case configuration, then make your CG adjustments after a couple of test flights.
Old 06-25-2013, 05:49 AM
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Corsair2013
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Default RE: CG = Wheels Up or Down?



It seems that some do it UP and some down.

The first flight I balanced gear down and it flew great.  But i later had a "momentary lack of reason" and hit a tree on approach so repaired everything and put in a different heavy duty set of retracts. 

The repaired plane with new heavier retracts is nose heavy with retracts down but very tail heavy with retracts up. 

If i add nose weight then I will get very nose heavy and am concerned about take off plus I don't want to add any weight if I don't have to.

Any other thoughts?

Semper Fi

Keith

Old 06-25-2013, 09:50 AM
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Default RE: CG = Wheels Up or Down?

Balance it for gear up (worst case for your plane). A nose heavy plane on take off is better than a tail heavy plane in flight. A nose heavy plane needs a little more speed, a tail heavy plane will need a lot of repairs!
Old 06-25-2013, 10:35 AM
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Default RE: CG = Wheels Up or Down?

I'd think balancing in the landing configuration should be the way to go.
You are slow for the landing or take off. that is when the CG matters the most.
 
But with a pattern plane or a jet, you might want to balance it in the 'clean' configuration and keep some extra speed
for the landing if needed.

Old 06-25-2013, 11:35 AM
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CanDo
 
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Default RE: CG = Wheels Up or Down?

Important point: aft CG is bad, whether the gear is up or down. Good luck!
Old 06-25-2013, 03:00 PM
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Default RE: CG = Wheels Up or Down?

Keith, what I would suggest is finding a solution to minimize the CG shift. Try to find lighter wheels, replace the piano wire gear leg with Titanium or anything else that will reduce the weight of the gear system. Once you car reduce the amount the CG shifts you can work out a safe flyable CG. Contrary to popular opinion nose heavy is not a good solution. It leads to nose overs, higher landing speeds and high speed stalls.
Old 06-25-2013, 03:02 PM
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Corsair2013
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Default RE: CG = Wheels Up or Down?

I will work on her tonight and post what it takes to balance with Gear Up and Down

Thanks to all for your input

Semper Fi

Keith
Old 06-25-2013, 03:04 PM
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Corsair2013
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Default RE: CG = Wheels Up or Down?

I do have light weight gear I can compare to.  Will change them out and see what the CG ends up at.

Old 06-25-2013, 03:05 PM
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Default RE: CG = Wheels Up or Down?

I would think you would want gear down. Landing is most important to me

ORIGINAL: acerc

Gear up is how you will fly it so gear up for balance.
Old 06-25-2013, 03:23 PM
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Chad Veich
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Default RE: CG = Wheels Up or Down?

ORIGINAL: CanDo
Important point: aft CG is bad, whether the gear is up or down. Good luck!

Listen to what CanDo is saying, he's offering up good advice! Your airplane needs to be balanced in such a way that the aft CG limit is never able to be exceeded even in the worst case scenario. USUALLY, but not always, this means gear up and fuel tank empty but there is no hard/fast rule that works for every airplane. If your landing gear retracts in such a manner that it moves the CG aft then you need to balance gear up, if it moves the CG forward then you need to balance gear down.
Old 06-25-2013, 03:52 PM
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LonnieMcc
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Default RE: CG = Wheels Up or Down?

I currently don't have a plane with retracts, but a very good friend of mine in our club does.

He has told me that when I do, it depends on how the gear is setup.

If I remember correctly, he said that if the gear when extended will be forward of CG the balance with gear down. Otherwise you can balance it with the gear up.
Old 06-25-2013, 04:28 PM
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impulse09
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Default RE: CG = Wheels Up or Down?

Just to pile on, balance your airplane in it's most tail heavy state.
Old 06-25-2013, 05:48 PM
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Default RE: CG = Wheels Up or Down?

With the gear down so you can land with the power off.
A tailheavy plane will fly with power on but not with the power off.
Old 06-25-2013, 05:59 PM
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harley6133
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Default RE: CG = Wheels Up or Down?

One gear up and one gear down. Balance to the center of the range. Then when gear goes up or down the weight shift has
minimal impact on the flight envelope.
Old 06-25-2013, 07:13 PM
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vertical grimmace
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Default RE: CG = Wheels Up or Down?

Keep in mind with a warbird that has gear retracting AFT, the CG is going to change. With your Corsair, if it balances OK with the gear retracted, the CG will shift forward when the gear are dropped.
Old 06-25-2013, 07:34 PM
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Jim Branaum
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Default RE: CG = Wheels Up or Down?


ORIGINAL: Corsair2013

I do have light weight gear I can compare to. Will change them out and see what the CG ends up at.

This is probably the best idea. Balancing with the gear up insures that you will be able to stretch a glide or simply slow down and not loose your aircraft to a snap out of a loop or other not fun unexpected stuff. However nose heavy will make landings more challenging as the nose heavy condition contributes to other problems.

Remember the old RC saw... Tail heavy airplanes will always fly once but they may not make a second flight.
Old 06-25-2013, 07:57 PM
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Corsair2013
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Default RE: CG = Wheels Up or Down?



Everyone,

I took a closer look at everything and moved the battery, receiver, telemetry,  and air valve around and now the plane is balanced "within the Hangar 9 specifications" 95mm to 108mm.  With gear down I am nose heavy at 100mm and with gear up I am just a little nose heavy at 107mm. 

I will probably need lots of trim after I take off but at least I should be safe enough to take off, fly, and land without a serious condition.

I will let you know what I find out after my flight.

Thanks to everyone!

Keith


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