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Old Yesterday, 10:12 PM
Old Prop Buster
Sir Dumb Thumb's Avatar
United States, CA, Grass Valley
Joined Dec 2009
652 Posts
Quote:
Originally Posted by Venboy View Post
Hi guys, I have a problem with my new Radian.
I finished to assemble my new Radian. I put some monokote colours on the wings for better view. I added clear tape around the wings edge to protect the border of the wings. And finally I added 2 strip of blue clear tape to the back of the elevator.

The manual say that the CG is 2,5 inches from the leading edges and when I put my Radian in the CG balancer that measure is giving me a very TAIL heavy plane !!.

I'm using a park zone 1300 mAh 3cell battery as recommended and a AR400.

I've removed the blue clear tape from the horizontal stabilization and still have Tail heavy plane. I think the CG is around the 2,75 and 2,8 inches...

What can be wrong ?
My plan is to maiden tomorrow !
:-(
My cg is 3.3 to 3.5 inches but everyone likes their plane differently. 2.75 would not be a bad place to start IMO. If you're worried move your battery up to make it 2.5 inches. Remember to do your glide test I told you about on Wednesday, that will give you an idea about cg and trim.
Gary
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Old Yesterday, 10:19 PM
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Venboy's Avatar
Canada, AB, Calgary
Joined Jun 2014
58 Posts
Thanks Lane.
I moved the Parkzone battery full forward and still tail heavy, them I replaced the battery with one nanotech 1300 mAh and it was better.... but still I notice that the balance is very fragile, I means a little touch to the nose or tail and it goes that way.

I have a Super Cub and this is very easy to balance with my "Greatplanes CG balancer".
Does anybody have the same problem ?... My Radian is just out the box !
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Old Yesterday, 10:38 PM
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Venboy's Avatar
Canada, AB, Calgary
Joined Jun 2014
58 Posts
Quote:
Originally Posted by Sir Dumb Thumb View Post
My cg is 3.3 to 3.5 inches but everyone likes their plane differently. ...
Gary
Thank you Sir Dumb Thumb. So you're flying with CG 3.3, you don't have any other modification in your Radian?. I'm affraid of a tail heavy plane

I'll do my glide test tomorrow before my first flight as you recommended me.
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Last edited by Venboy; Today at 06:49 AM.
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Old Today, 04:15 AM
Rookie plane pilot
BWX_'s Avatar
United States, NY, Big Flats
Joined Nov 2013
156 Posts
2.75 will fly great I think. 2.5", for me, is WAY too far forward.. And 3", to me, feels way to far back. I was just experimenting two days ago with it.

It does make a huge difference, especially during slow speed cornering with wing at an angle to ground. At 2.5" I was getting stalls that seems like the nose was falling down before anything else, and at 3" it felt to me like tail was wanting to go first, if that makes any sense at all to you.

My starting point would be to go a little bit further forward or back from 2.75", and see what feels good. I would not want to start out at 2.5", flying the plane for the first time, and I definitely wouldn't want to start out at 3" for the first flights.

Once I get better digital servos in there, and better more precise control rods (maybe some "gold-n-rods?), I think maybe 3" will feel better. My center point on my servos isn't very precise, and the more precise control I have with CG further back just magnifies that problem.

I'd leave it there and give it a shot. If you do a glide test with power off, throw it harder (faster) that you think you need to- level or just a little bit up.. If you don't throw it hard enough it'll be doing a nose-in type landing no matter what.
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Old Today, 06:59 AM
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Venboy's Avatar
Canada, AB, Calgary
Joined Jun 2014
58 Posts
I found that I'm not the only one reporting this "problem" . On June 14th, 2014 Grandpa Fury wrote the report #17796 in this thread, and he said exactly same thing about his new Radian..

But I can't find what he finally did...
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Old Today, 08:10 AM
Rookie plane pilot
BWX_'s Avatar
United States, NY, Big Flats
Joined Nov 2013
156 Posts
What problem? LOL.. Really if you have CG at 2.75in back, I think your golden for maiden. Maybe try for a few mm farther forward, but either way, you're going to like the way it flies once it is trimmed out.

Just be careful before you trim it out, because a poorly trimmed out radian can be a little bit of a handful on your very first flight.
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Old Today, 08:24 AM
1st to the scene of the crash
Laneritc's Avatar
United States, GA, Dalton
Joined Jul 2012
1,141 Posts
Just got back from the field, nice peaceful and quiet. Got two really good flights with the Radian, using a 1250mah battery flew great. Telemetry worked perfect, no dropped signals that I know of. Keep the UMX Radian up for over 20 mins. Storms moving in this evening so got my flying in early.
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Old Today, 08:58 AM
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FabFlight's Avatar
Canada, QC, Saint-Rémi
Joined Sep 2013
473 Posts
I'm wondering if the new pushrods parkzone began to install didn't wacked the CG.
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Old Today, 09:43 AM
Rookie plane pilot
BWX_'s Avatar
United States, NY, Big Flats
Joined Nov 2013
156 Posts
Quote:
Originally Posted by FabFlight View Post
I'm wondering if the new pushrods parkzone began to install didn't wacked the CG.
Interesting that they put heavier pushrods on, and "fixed" the decalage at the same time.

Basically moving CG back, and compensating with decalage just like in that vid.

I have some beefy carbon strips down the top and bottom of fuse, and also a strip of tape down the bottom, and my CG wasn't too far back though. Just a little back past stock.
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Old Today, 10:05 AM
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Venboy's Avatar
Canada, AB, Calgary
Joined Jun 2014
58 Posts
Quote:
Originally Posted by BWX_ View Post
Interesting that they put heavier pushrods on, and "fixed" the decalage at the same time.

Basically moving CG back, and compensating with decalage just like in that vid.
.
Do you think so ?. It's that possible ?
But then they should change the CG value in the manual
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Old Today, 11:54 AM
Rookie plane pilot
BWX_'s Avatar
United States, NY, Big Flats
Joined Nov 2013
156 Posts
Quote:
Originally Posted by Venboy View Post
Do you think so ?. It's that possible ?
But then they should change the CG value in the manual
Yeah.. I dunno. I think it will fly fine at either CG the way it is set up now. Maybe that's why they didn't change it in manual.

They didn't change the control rod type or say anything about decalage either though. So I guess what's in the manual isn't really up-to-date anyways.
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Old Today, 01:20 PM
Registered User
USA, CA, Pismo Beach
Joined Oct 2007
1,342 Posts
It's not unlikely that the new pushrods are impacting where the CG is. The clevises appear to be thread-on so the pushrods need to be large enough to cut a thread. Like a couple of mm diameter. Speculating here, the only other thing that could make big difference in CG because of mass would be a different (lighter) motor.

Venboy - don't worry about a CG at 2.75". Just give it a good test glide and be sure that the battery is secure so it doesn't move around after a rough landing. In fact it's a good idea to check it after every landing; prevents surprises.
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Old Today, 04:30 PM
Registered User
United States, NJ, Fairfield
Joined Jan 2012
81 Posts
i find that my radian flys best with my 2100 venom battery. With this battery it hangs out of the slot about 1" and the cg is pretty close to what it states in the manual. When i fly with the 1300 the plane feels to light and seems to not glide as well. Plus with the 2100 i get an hour plus of flight time.
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Old Today, 10:29 PM
Work....fly, repeat...
AeroRecon's Avatar
Fredericksburg, Virginia
Joined Jul 2008
1,605 Posts
Dang. Dropped mine into the ocean today on the OBX. Was flying fine...tossed around a bit with a little breeze but was fine. Then the rudder quit moving. Bumped the throttle and it worked as did the elevator. Once clear of the few folks on the beach I pushed into the surf about 50 feet out. My son was nearby and he swam out and got it. No camera, just flying around. Washed in clean water when I got home and blew the parts out several times.
Everything feels fine...nothing stripped or loose or broken. Just wet.

What a horrible feeling that is at the moment you realize you no longer have at control..even partial control.

Hopefully everything will work after it dries for a few days. Nothing better than a Radian at the beach.
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