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Glider advice - 9/24/2009 9:43 PM   
flag8r


 

Posts: 119
Score: 105
Joined: 10/30/2006
Last Login: 10/5/2009
From: Jacksonville, FL, USA
Status: offline 		I STILL have the itch to upgrade my glider. Currently "flying" a Hobbico Upstar with the following guts;
-Hyperion G2213-16 motor (no idea if this is large enough)
-Aero naut CF 10x8 folding prop
-JR NES 517 analog servos (I'm guessing they are 10 yrs old!)
-2S 2100 lipo

I am really not happy with this setup. I bought it used obviously. Do you think upgrading to a 3S lipo would make a large difference in performance as well as upgrading the servos?

It also feels very sluggish in turns (rudder control only) and it only "goes" when I apply power. Normal for rudder only gliders?

I am close to ditching it and upgrading, but wondering if I can at least use that motor in my next proper glider. Thanks for all the continued help!



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RE: Glider advice - 9/25/2009 5:13 PM   
flag8r


 

Posts: 119
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From: Jacksonville, FL, USA
Status: offline 		Anyone, Bueller?

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RE: Glider advice - 9/25/2009 5:54 PM   
CBM Racing


 

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From: rhinelander, WI, USA
Status: offline 		I just the allerc site and using their data sheet it looks like the combo would be ok on 3cells. Depends on your esc rating, but at 10.39 volts using a 10x6 prop, it was drawing 24.2 amps. So you should be fine if you are using a 30 amp esc and your batteries can handle the load. You could go up to a 11x6 prop safely and it should really pull you up pretty fast. As to the performance of the glider, not sure if that is how it is supposed fly or not. I have the radian and it seems very very slow moving in calm air, but, if I give some down trim it will move along pretty good. Try a 3 cell battery, and when up to altitude, get it trimmed properly, and just let it glide for a long time. If your balance is to nose heavy it will be hard to trim for level flight as it will want to porpoise up and down. You should be able to get it flying pretty good by checking and setting balance, trims, and just learning how to make it go where you want it. Don't give up yet on it though, just take some time with it and learn to thermal it and then get a better ship. Good luck!

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RE: Glider advice - 9/28/2009 1:59 AM   
glidagida


 

Posts: 34
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Last Login: 11/21/2009
From: AdelaideSouth Australia, AUSTRALIA
Status: offline 		The lack of turning could be due to several reasons including poor design, however let us look at the more obvious ones first, the ones that can be sorted by a bit of tuning.

1. As CBM has already stated the 'handling like a truck' syndrome especially in thermal turns may be the result of a FORWARD cofg.

Also as CBM correctly points out this may manifest itself in a GENTLE porpoising motion when you are flying level and you speed up your glider. This is not to be confused with the LIVELY porpoising motion [stalling] caused by a too rearward cofg, rather we are talking about a gentle slight dive and then nose up attitude which takes place over 10-20 plane lengths or longer. It is still a stall, but not a violent tip stall.

If your glider is nose heavy in essence your glider is trying to carry the excess weight in front of the cofg by compensating with UP elevator. Check your static elevator setting if it is slightly up then this might be a clue to this condition, and it is a single speed condition. The elevator can only truly compensate for that condition at one airspeed where the downward lift of the elevator is just offsetting the additional nose weight. Increase the speed and the system is out of equilibrium. The result is the downward lift of the tail is increased slightly so the plane starts to climb gently until it slows down and .....stalls....gently. So it drops its nose and dives gently until it reaches flying speed again ... and the cycle repeats.

The cure is to do the 'Dive Test' so on a relatively still day, take the model up to a safe height and fly 90 degrees across your line of sight, then put your model into a slight dive, say 30 degrees, and take your hand off the elevator stick [neutralize the controls] and watch the attitude of your plane.

a. If the model keeps going in the same line it is neutrally stable, fine for F3B pilots but not good for a beginner. Add some noseweight until result d is achieved.

b. If the model tucks under and steepens the dive then the cofg is TOO FAR BACK. Add some noseweight until result d is achieved.

c. If the model pulls up from the dive quickly and starts to climb then it is positively stable and the cofg is TOO FAR FORWARD. Remove some noseweight until you reach result d.

d. If the model pulls up gently and recovers in a slight pull out then the model has slight positive stability which is what beginners and most other pilots prefer. This gives a model which will be relatively sensitive to thermals but will eventually recover itself from difficulties if the pilot goes hands-off.


2. The wing Incidence may be out.

Check http://www.rcuniverse.com/forum/m_9053937/tm.htm

for a discussion on what this is and how it may affect your model.

Cheers


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Sailplane.AUS www.rc-sailplane.com.au

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RE: Glider advice - 11/7/2009 2:09 AM   
aeajr



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From: Long Island, NY, USA
Status: offline 		You upstar is probably nose heavy. Try moving the CG back.

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RE: Glider advice - 11/7/2009 5:08 AM   
sailjunky


 

Posts: 13
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Joined: 11/5/2009
Last Login: 11/17/2009
From: flagstaff, AZ, USA
Status: offline 		you can also make the rudder area larger i have done this with a topaz actually seen this done on many topaz gliders to get them to turn tighter..

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RE: Glider advice - 11/8/2009 12:54 AM   
OzMo



Posts: 1842
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Last Login: 11/21/2009
From: OZark, MO, USA
Status: offline 		not enough poly or dihedral can cause poor turning though I think your plane should be fine in that reguard. Experiment with small adjustments of the CofG to the rear. Its fun to do anyway

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