Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

DC F-20 Tigershark CG

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Old 09-29-2004, 09:55 PM
  #1  
jzinckgra
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Default DC F-20 Tigershark CG

I have one of the older (~7 year old) DC F20 kits. I was getting ready to balance the model and read in the manual that the cg should be at 5.75" from the LE. I put the plane upside down on the cg machine and the nose dropped like a lead weight= very nose heavy. I can't imagine how much weight I'll have to add in the tail, but it'll have to be a lot. Is this cg correct? What have you guys used for the DC kit (not ARF)? I've got mech. retracts, so the plane is already a little heavy, so adding dead weight is the last thing I want to do, but looks like i'll need to add some. All of the retracts (elevator, rudder, throttle) are in the rear, so I can't move these. Putting the Rx battery towards the rear will help some, but not that much. Here's a pic:
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Old 09-30-2004, 08:00 AM
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Cyclic Hardover
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Default RE: DC F-20 Tigershark CG

I installed my extra weight in side the tailcone.
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Old 09-30-2004, 12:13 PM
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jzinckgra
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Default RE: DC F-20 Tigershark CG

I installed my extra weight in side the tailcone.
yes, but how much weight. with that jett .50 you have in the front, i'm guessing it was a lot. So the 5.75" is correct then, eh?
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Old 09-30-2004, 07:21 PM
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jzinckgra
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Default RE: DC F-20 Tigershark CG

Actually, I think I might have screwed up alittle. I was using the cg machine and the little balance points on either side were about ~2" out on either side from the wing root. With the swept wing, this was placing the cg more like 7" back instead of the 5.75". I used a regular ruler and measured 5.75" exactly at the wing root then set the cg machine to this. The plane is still a little nose heavy, but not nearly as bad as before.
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Old 09-30-2004, 08:11 PM
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Cyclic Hardover
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Default RE: DC F-20 Tigershark CG

Shoot I don't remember but I stuffed all I needed back their. It's been 5 years since I put it back there. Flying them is great but I love the landings. Thats my best part. I bring it on in an let it roll on the mains for a bit then bring the nose down. Real sweet.
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Old 09-30-2004, 08:42 PM
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Default RE: DC F-20 Tigershark CG

The Kangke/Cermark F-20 is between 5 and 1/2 inches and 6 and 1/4 inches. Mine balances at about 5 and 3/4 and flies great!!
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Old 10-01-2004, 05:38 PM
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Default RE: DC F-20 Tigershark CG

I put a flat battery pack all the way up against the rear bulkhead in my Cermark.
It was relly nose heavy....even with the Rossi .45, and the long pipe. [X(]

FBD.
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Old 10-01-2004, 07:15 PM
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Default RE: DC F-20 Tigershark CG

I did the same thing with my battery........ and I glued 3 ounces in the tail compartment Turns like a Quicke though.
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Old 10-01-2004, 08:19 PM
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Default RE: DC F-20 Tigershark CG

The battery pack alone did the trick on mine....I guess the Rossi is a tad heavier
than the others. I used fiberglass rods to the rear surfaces, and that helped.

I have mine running right at the envelope fo the model....I just got some minor
flutter....Razor heard it....we think it's coming from the rudder, or the nosewheel.

Dave.
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Old 10-01-2004, 08:48 PM
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Default RE: DC F-20 Tigershark CG

Hey FBD, you fly fast enough to generate flutter? HAHAHAHAHAHAHAAHAHAHHAHA

Just kiddin' you Bro'!

Gary
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Old 10-01-2004, 08:59 PM
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Default RE: DC F-20 Tigershark CG

I'm still trying to find a good pipe for the Webra50GT. Anyone ever used a pipe with a Webra 50??
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Old 10-02-2004, 08:25 AM
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Default RE: DC F-20 Tigershark CG

i think my old Tru-turn spinner weighs a lot and is contributing to the nose heaviness, but it sure looks better than a plastic one.
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Old 10-02-2004, 08:14 PM
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Default RE: DC F-20 Tigershark CG

Stick with the aluminium spinner!! One of the plastic jobs cost me mine. If it blows in flight the drag is incredible.
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Old 10-03-2004, 05:13 PM
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Default RE: DC F-20 Tigershark CG

what size wheels are you guys running on your tigershark's? i brought mine over to our grass field today to taxi it around and the gear seems really whobbly. I have the wimpy hobbico mech. retracts with 2" wheels on the plane. I'm thinking of either getting 2.5" wheels or drilling out the retract mounts to accept slightly larger struts. I'm a little hesitant to do this yet because it seems like I'll just make the gear weaker around the plastic housing at the base of the struts.
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Old 10-03-2004, 08:52 PM
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Default RE: DC F-20 Tigershark CG

I use 2 inch Kavans. I use Kavans on all my planes. Mainly for protection. It all but eliminates wheel bouncing which can rip out gear and flip the plane over and get wing damage. The planes just slide around nicely when the end of the runway comes up to quick,
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Old 10-03-2004, 11:14 PM
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Default RE: DC F-20 Tigershark CG

Hello
I am using a Mac pretune pipe system for which it for a Thundertiger pro .46. Now its on my Webra .50 wich you don't need to cut the pipe. Its been doing pretty good for me. Or a mini pipe wich is loud it works too.
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