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Old May 28, 2012, 10:20 PM
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McCarthy, Alaska
Joined Jun 2004
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Originally Posted by grovey View Post
Hi all

I got a question about the cg on THIS plane. Should the nose of the plane be exactly level with the tail at perfect cg?

For this, the stock battery needs to be all the forward in the battery tray, the tray does not seem adequate if this is the case
That is a good question. I think the answer is yes, pretty much. Although I find that a space of maybe 3/8" between the battery and the aft bulkhead works out about right with a 180 to 210 mah battery. Mine doesn't need to be too far forward.

I was flying my CC with the battery too far back for some time. It surely flies much better with the CG at the proper location. Too far back exaggerates the "dropping out of the air" sensation. Proper CG is much more stable.

One thing I am finding with this airplane is that it requires quite a bit of stick time to get real comfortable with, at least for me. I am enjoying it more as time goes by.
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Old May 28, 2012, 10:24 PM
Just wanna fly!
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United States, TX
Joined Apr 2008
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Thanks WSEN, looks like I might struggle with CG because with the battery further aft it seems quite tail heavy.

Also for those who have BabbelBats, how are you getting them to fit secure?
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Old May 28, 2012, 10:25 PM
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Sayre,PA
Joined Sep 2002
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Originally Posted by Azrie View Post
Is anyone doing anything to strengthen the foam/control surfaces? They are a little flimsy and I'm wondering if adding tape or laminating film or anything to add stiffness or strength?
By far the best way to do this is with 1/2 or 3/4oz fiberglass applied with Minwax Polycrylic. It's very easy to do, lightweight, adds a lot strength and stiffness and is not all that noticable. Attached is a photo where I added a small strip of 1/2oz fiberglass to strengthen the fin.
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Old May 28, 2012, 10:25 PM
Gopher huntin' stick jockey
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East Bethel, MN USA
Joined Jul 2009
11,954 Posts
Quote:
Originally Posted by grovey View Post
Hi all

I got a question about the cg on THIS plane. Should the nose of the plane be exactly level with the tail at perfect cg?

For this, the stock battery needs to be all the forward in the battery tray, the tray does not seem adequate if this is the case
Grovey,

When balancing, the pitch of the wing should be zero.

BTW - the battery tray extends forward of the main opening. Also, many of us use larger-capacity, higher-power packs in these planes, so it's good that the factory pack needs to be forward of center in the tray. Because of this, we can run packs as large as a Hyperion 320 & still get the CG right.

Regarding the Babbelbatts - I'm using Velcro to secure them, just like the factory pack.

Joel
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Old May 28, 2012, 10:29 PM
220 221 Whatever it takes
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USA, IL, Belleville
Joined Dec 2009
276 Posts
Quote:
Originally Posted by jimsp View Post
By far the best way to do this is with 1/2 or 3/4oz fiberglass applied with Minwax Polycrylic. It's very easy to do, lightweight, adds a lot strength and stiffness and is not all that noticable. Attached is a photo where I added a small strip of 1/2oz fiberglass to strengthen the fin.
Sorry but these 66 yr old eyes can't see where you put on the cloth. That is really cool being so invisible but where did you put it (can you outline it for me please).

Thanks,
Capt. Dave
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Last edited by captdave221; May 28, 2012 at 11:15 PM. Reason: added a pic
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Old May 28, 2012, 10:37 PM
Just wanna fly!
grovey's Avatar
United States, TX
Joined Apr 2008
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Quote:
Originally Posted by turboparker View Post
Grovey,

When balancing, the pitch of the wing should be zero.

BTW - the battery tray extends forward of the main opening. Also, many of us use larger-capacity, higher-power packs in these planes, so it's good that the factory pack needs to be forward of center in the tray. Because of this, we can run packs as large as a Hyperion 320 & still get the CG right.

Regarding the Babbelbatts - I'm using Velcro to secure them, just like the factory pack.

Joel
Thanks Joel, I have the 240s and they seem a bit thick to place forward in the battery cavity.

Lemme grab the plane again and a Hyp 240
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Old May 28, 2012, 10:48 PM
Just wanna fly!
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United States, TX
Joined Apr 2008
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Ok so I placed the battery so that the edge of the battery is about 3/4" from aft in the tray and it "looks" ok, but to get the wing at zero pitch (level?) I would really need to move the battery forward. At that point, if the wing needs to be level, then the tail is really high above the wing.
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Old May 28, 2012, 11:00 PM
Just wanna fly!
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United States, TX
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Here is a pic, with the edge of the battery about 3/4" forward in the tray, with cg being 27mm.
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Last edited by grovey; May 28, 2012 at 11:06 PM.
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Old May 28, 2012, 11:06 PM
If it spins, wear it.
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Northern Nevada
Joined Jan 2011
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Quote:
Originally Posted by grovey View Post
Here is a pic, with the edge of the battery about 3/4" forward in the tray
I usually consider CG correct when the elevator is level? Am I wrong?
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Old May 29, 2012, 12:58 AM
Gopher huntin' stick jockey
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East Bethel, MN USA
Joined Jul 2009
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Grovey,

That should be close enough for the maiden. The optimal CG location is determined by flight-testing.

Joel
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Old May 29, 2012, 01:25 AM
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Joined Aug 2011
807 Posts
Quote:
Originally Posted by captdave221 View Post
Sorry but these 66 yr old eyes can't see where you put on the cloth. That is really cool being so invisible but where did you put it (can you outline it for me please).

Thanks,
Capt. Dave
It would be the red outlined area
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Old May 29, 2012, 03:00 AM
BMFA 190658
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United Kingdom, Yeadon
Joined Mar 2007
4,515 Posts
Quote:
Originally Posted by grovey View Post
Here is a pic, with the edge of the battery about 3/4" forward in the tray, with cg being 27mm.
That looks about right, maybe the tail a little higher to get the wing and tailplane level.

Taildraggers sit with the tail down on the rear wheel, when flying the wheel is quite high up
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Old May 29, 2012, 06:18 AM
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Belgium
Joined Aug 2008
45 Posts
"Complete tail" question?

Hello,

Any "Complete Tail w/Accessories: UMX Carbon Cub
(EFLU1125)" owners out there who could post a picture of it?
I would like to know how complete is complete Do we need a decal sheet set for example in order to get it complete?

I'm making a list of spare parts i will probably need soon or later...
Thanks!

Tom.
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Old May 29, 2012, 06:53 AM
Lost Realist
United States, IL, Chicago
Joined Apr 2012
71 Posts
I'm starting to think the issue might be with the airframe itself, not the brick! My beast 3d brick was 'known good' with 25 good flights. Put it in the Carbon Cub and suddenly the rudder servo motor burns out after two flights. It acted like it was sticking but really the motor no longer had enough torque. Fine. Replaced the motor, working again. 3 more flights and now the elevator servo is getting stupid. Locks up at times and gets stuck stalling. Wont respond to down elevator. Did this a few times, only in flight, not on bench. Finally resulted in a fatal crash that made the plane unable to be recovered (landed on an inaccessible side of a large lake) very dissapointed...
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Old May 29, 2012, 07:02 AM
Just wanna fly!
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United States, TX
Joined Apr 2008
1,012 Posts
I wonder if this is happening as a result of the control rods binding against the horizontal stab. Both rudder and elevator control rods. This coupled with surface hinges which could be a bit stiff.

Most of the failures seem to be elevator and or rudder servos.
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