Polecat ARF kit tail breaks in flight  
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All Forums >> RC Airplanes >> ARF or RTF >> NitroModels Support >> Polecat ARF kit tail breaks in flight
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Polecat ARF kit tail breaks in flight - 3/20/2007 2:02:59 AM   
johnnychimpo



Posts: 386
Joined: 3/17/2005
From: ft rucker, AL, USA
Status: offline 		Almost lost my polecat on the second flight. The tail section got some crazy flutter so I throttled back and landed. Barely... The stab and elevator both broke on the soft balsa. The tip of the elevator and the stab on the right side snapped. The only thing holding the tail together was the covering. Ive tore off the covering, added weight to the elevator tips, and ordered some wire to secure them to the fin.

Does anyone think that adding weight to the elevator will help, if not, eliminate the flutter that caused this? I have beefed up the push rod with carbon fiber tubes as well.

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< Message edited by johnnychimpo -- 3/20/2007 2:13:52 AM >

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RE: Polecat ARF kit tail breaks in flight - 3/20/2007 3:11:29 AM   
nitrostaff1



Posts: 562
Joined: 10/20/2006
From: LA, CA, USA
Status: offline 		Pm me so I can replace the elevtor.

John
Nitro Planes

quote:

ORIGINAL: johnnychimpo

Almost lost my polecat on the second flight. The tail section got some crazy flutter so I throttled back and landed. Barely... The stab and elevator both broke on the soft balsa. The tip of the elevator and the stab on the right side snapped. The only thing holding the tail together was the covering. Ive tore off the covering, added weight to the elevator tips, and ordered some wire to secure them to the fin.

Does anyone think that adding weight to the elevator will help, if not, eliminate the flutter that caused this? I have beefed up the push rod with carbon fiber tubes as well.



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RE: Polecat ARF kit tail breaks in flight - 3/20/2007 3:54:32 PM   
opjose



Posts: 5287
Joined: 11/26/2005
From: Poolesville, MD, USA
Status: offline 		The thing that fights flutter the most on the elevator will be the holding power of your servos and the firmness of the entire associated pushrod assembly.

With the weight as per the picture there is not going to be a lot of effect, as the trailing edge will want to resonate in flight.

A mid stab mounted anti-flutter horn/weight will be of benefit, as would digital servos and beefing up the pushrods to hold the stab firm.

It sounds as if your flying this bird at very high speeds.


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RE: Polecat ARF kit tail breaks in flight - 3/20/2007 4:25:32 PM   
johnnychimpo



Posts: 386
Joined: 3/17/2005
From: ft rucker, AL, USA
Status: offline 		Not flying at high speeds by any stretch of the imagination. I fly Q-500 mainly and i know what speed is. 12x5 break in prop and 11x7. Second flight. The push rods are very weak. i have since put carbon tubing instead of the weak wire Y harnes type push rod. I am using digital servos too except for throttle. My servos are joined by z bends to the rods.

< Message edited by johnnychimpo -- 3/20/2007 4:27:14 PM >

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RE: Polecat ARF kit tail breaks in flight - 3/20/2007 5:00:56 PM   
opjose



Posts: 5287
Joined: 11/26/2005
From: Poolesville, MD, USA
Status: offline 		You may also want to beef up the control horns and adjust the linkages so there is less throw (but more leverage) to help prevent flutter.

Make sure that there is no up/down movement of the elevator what-so-ever when it is not in motion.

After NP sends you a replacement elevator, consider hardening the balsa with thin CA.

I've often pealed back the covering and liberally applied thin CA on many structures w/o problems.

On large tail surface planes, you may want to consider running a CF rod from the outer part of the elevator to the fuselage. You can affix the CF rod either by using strut support fittings ( Dubro has a set ) or by merely drilling a shallow hole in the stabilizer and fuselage, and epoxying the CF tubing in place. I do the latter on smaller (sub .90 sized) planes.

This will make the tail far more durable and less prone to resonate.

Finally don't forget to seal the hinges.








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RE: Polecat ARF kit tail breaks in flight - 3/20/2007 5:12:17 PM   
johnnychimpo



Posts: 386
Joined: 3/17/2005
From: ft rucker, AL, USA
Status: offline 		Thanks, working on thin CA on the stab and getting some wire to secure everything.

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RE: Polecat ARF kit tail breaks in flight - 3/20/2007 10:35:38 PM   
samuel_a15


 

Posts: 3
Joined: 3/18/2007
From: Gothenburg, SWEDEN
Status: offline 		I was thinking about buying this plane since it looks good and is cheap. How is it flying? To land and so on? Is it a good 3d plane and what engine could you recommend? It looks like the engines in the specs are to slow to do 3d, but perhaps Im wrong.

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RE: Polecat ARF kit tail breaks in flight - 3/21/2007 5:29:12 AM   
johnnychimpo



Posts: 386
Joined: 3/17/2005
From: ft rucker, AL, USA
Status: offline 		Its built really good except i think the elevator push rod has too much play. I would get 2 elevator servos and run them independent to avoid flutter. Im putting cable between the fin and stab to stiffen it up a bit. Flew great on the first flight. I put a 52 magnum engine in it and that seems to be the best option. Its a nice kit IMO its no 3d monster though.

Here are some pics of it after repair and addition of wire on the tail section.

I got 5 tanks thru it today. No flutter but the elevator still needs additional support. I think im going to cut the covering off the bottom and make some guides for the elevator push rod so it does not shift from side to side.

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< Message edited by johnnychimpo -- 3/22/2007 2:14:49 AM >

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RE: Polecat ARF kit tail breaks in flight - 3/22/2007 5:12:40 AM   
rcplaneworld



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Joined: 6/17/2006
From: Kissimmee, FL, USA
Status: offline 		I purchased an ME109 arf a few years ago with the same problem. I was running an OS AX .46 and a 10x7 prop. Medium speed down the runway and you could see the tail stab and fin flutter. I used 4-40 rods and horns from the fin to the stabs all of the way around. Fixed the problem fast quick and in a hurry!

It was fluttering enough that I landed the plane..... The tail section was stick built for weight, instead of a solid piece of balsa wood. The tail survived the plane hitting a tree! My BAD.

The ARF was made by Jamara Modeltech in Germany as I thought it would be way cool to own an ME-109 that came from Germany, at least I still have the hat.

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RE: Polecat ARF kit tail breaks in flight - 3/27/2007 8:24:46 PM   
johnnychimpo



Posts: 386
Joined: 3/17/2005
From: ft rucker, AL, USA
Status: offline 		Update, i have around 20 or so flights on this puppy. It flys soo nice. Landing is predictable and the thing just seems like its on rails. The magnum 52 4 stroke has plenty of power and has proven extremely reliable. Not one dead stick or any engine issues what so ever. For $119.00 its great deal. Im running a 11x6 prop on it for ground clearance. The aircraft does sit low to the ground. Maybe a 10x7 would be better to avoid blade strikes on the pavement.

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RE: Polecat ARF kit tail breaks in flight - 3/27/2007 9:24:20 PM   
NJ Georgee


 

Posts: 334
Joined: 10/11/2002
From: Bayonne, NJ, USA
Status: offline 		Hi there ,interesting tread,can I ask you something?I got a new 72 size engine they recomend an 11" to a 13" prop depending on sport ,scale ect. during break in.
what if none of those sizes look right and say you want to use a 8" prop would it hurt the engine as long as you dont max out rpm's?

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RE: Polecat ARF kit tail breaks in flight - 3/27/2007 9:31:20 PM   
opjose



Posts: 5287
Joined: 11/26/2005
From: Poolesville, MD, USA
Status: offline 		Putting on a smaller prop than recommended but using the same pitch will make the engine spin faster (more RPM's) up to it's power curve limits.

The engine will actually run cooler, but may not necessarily over-rev.

You can offset this a bit by increasing the pitch.

Frankly if you have extra prop diameter that you want to bring down, consider going with more blades in the prop.

e.g. instead of an 11x6 use a 10x6 three blade... etc.

This will give you the same loading as the two blade prop.



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RE: Polecat ARF kit tail breaks in flight - 3/28/2007 3:51:06 AM   
johnnychimpo



Posts: 386
Joined: 3/17/2005
From: ft rucker, AL, USA
Status: offline 		Nice hijack of the thread NJ Georgee.

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RE: Polecat ARF kit tail breaks in flight - 4/23/2007 2:13:43 AM   
johnnychimpo



Posts: 386
Joined: 3/17/2005
From: ft rucker, AL, USA
Status: offline 		Got the new elevator and stab last week. NP you people are doing a great job on customer support. I commend your efforts.

< Message edited by johnnychimpo -- 4/23/2007 2:14:13 AM >

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RE: Polecat ARF kit tail breaks in flight - 7/23/2007 8:08:13 PM   
opjose



Posts: 5287
Joined: 11/26/2005
From: Poolesville, MD, USA
Status: offline 		I really like the looks of this plane.

I wish there was a larger version of it.

Do you think I could shoe in a .46 to .60 two stroker?


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