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Old Jul 28, 2006, 09:58 PM
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Australia
Joined Nov 2005
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Hyperion Sukhoi 31 - just can't get it dialed in!!! arrrggghhhh!!!

I have a Hyperion Sukhoi 31, powered by a Hyperion Z2213-20 / 25A ESC. No matter what I do I just can't seem to get it flying well. Have posted here before about rolling motion during loops, slow speed handling, etc.

What is everyone's experience with this aircraft? What props are being used (for Z2213-20), what are the tips to trim it our well for knife edges, what are the tips to get smoother, more aligned loops, etc? Is CG a major contributor to this sort of thing? I'm trying to work out whether this is just a difficult aircraft to get dialed in, or whether its completely the pilots fault! probably the latter, but doesn't hurt to ask...).

I have used props from 8x6, 8x8, 9x4.5, 10x5 ... 20C batteries from 1500mAH to 1800mAH.

What is everyone's experience of this aircraft?
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Old Jul 29, 2006, 02:32 AM
Electric Flyer
San Diego
Joined Jul 2006
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I will be happy to comment on the aircraft performance as soon as I fly it first time. Hopefully I will be able to fly it Sunday.
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Old Jul 29, 2006, 02:55 AM
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Australia
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Lucas - good luck - it is a well constructed aircraft, but I am just having trouble 'getting it all together' (probably just me though). Keen to hear your experience. What motor / prop are you using?
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Old Jul 29, 2006, 03:28 AM
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Sydney, NSW, Australia
Joined Oct 2000
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I've got the Hyperion Extra 300, and also found it needed quite a bit of sorting. Set up with the recommended throws, it was waaaayyyy too sensititive in pitch and roll. On the test flight, I didn't think I was going to get it back down in one piece, it was all over the place.

I was also using Dymond D60 servos, which didnt help, as they were quite non-linear in movement. With reduced throws and 55% expo, it now flies quite well.

I occasionally have a scary moment when doing stalling manoeuvres down low, as it does need a bit of airspeed to be controllable. It can be above stall speed and flying, but be virtually uncontrollable until it gains a few more knots. This is this only aircraft I have ever had to dodge and run away from! I put the low speed tendency down to mine being a bit overweight, due to having 2100 lipo's. From memory, weight is about 590gm, vs the max recommended weight of 550. Not much over, but a bit.

Other than that, well it doesn't fly like a large model, but its not one!
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Old Jul 29, 2006, 03:35 AM
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Australia
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Keith - thanks. What power / prop are you using? Also, do you find any problems with doing loops (ie: rolling motion at the top of the loop?). thanks.
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Old Jul 29, 2006, 05:04 AM
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Joined Mar 2001
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Quote:
Originally Posted by boltor
Keith - thanks. What power / prop are you using? Also, do you find any problems with doing loops (ie: rolling motion at the top of the loop?). thanks.
Keith is right on with the recommendations. The kits should all have an addendum to correct the CG and stridently warn about reducing throws, but some dealers may not have gotten them put in the box.

Set CG to 50mm from wing LE. And set throws to:

HIGH Rate
60% of recommended throw
50% Exponential (less movement at beginning of stick travel)

LOW Rate
50% of recommended throw
50% Exponential (less movement at beginning of stick travel)

Fly on Low Rate first.

Differential throw on the ailerons is a good thing for almost any model. (more travel (say 30%) on the UP aileron than on the DOWN aileron). You can mix differential for any two servo wing if your radio supports it, or set it up mechanically (sometimes tricky).

Too much elevator can cause a stall which appears in a loop as rolling out, but typically this is most noticible at the beginning of the loop, rather than at the top. If, after setting CG and throws as above you still see it, maybe you need to carry a little more speed through the top of the loop. You might try increasing the speed at which you enter the loop - pulling gradually on elevator as you enter - and relax elevator quite a bit at the top... Also double-check to be sure the HOR STAB is lined up properly with the wing. And check to see that the wings both have the same incidence at the wingtips (tape a couple rods along each wingtip and sight down the spar line). You can straighten a wing by flexing the tip in the right direction and shrinking out the wrinkles which pop up in the covering. Twist a bit more than you actully need, as the wing will relax back a bit.

Hope you get it flying perfect, soon.

David
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Old Jul 29, 2006, 08:21 AM
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USA, TX, Trophy Club
Joined May 2002
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Quote:
What is everyone's experience with this aircraft? What props are being used (for Z2213-20), what are the tips to trim it our well for knife edges, what are the tips to get smoother, more aligned loops, etc? Is CG a major contributor to this sort of thing? I'm trying to work out whether this is just a difficult aircraft to get dialed in, or whether its completely the pilots fault! probably the latter, but doesn't hurt to ask...).
The setup I settled on with the Hyperion motor was the 8x6 prop. It likes the speed and needs to be flown fairly quickly.

Just as David mentions - my CG was right at 50mm. I used about 35% expo (high for me) and on low rates the plane won't snap out of anything (unless you use full up at full speed).

Light is better I used the Hyperion 1200 3s pack. It did well at the 15+ amp draws.

You need to fly this plane, all the way down in landings. Do not slow down too much! Keep some speed on in landings and it will live a lot longer....

Mine did perfectly round loops 100 foot loops. Loops are actually hard to do, so don't rush them! I does axial rolls and it snaps better than any plane I have flown (inlcuding Caps!). They are a thing of beauty. It spins well and is a fantastic little bird. But you must fly it allthe time.

KE tucked (I can't remember which way-sadly it meet a chipmunk in a midair) but as I recall it was to the canopy end so it will need some mixing there just as most planes.

A fantastic plane, I think you just need some pitch speed. Practice and burn a lot of batteries.

Mike
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Old Jul 30, 2006, 03:03 AM
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Australia
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323 Posts
Mike, David and Keith - thanks very much for the advice. Well, two things seemed to be wrong - the first was obvious - my CG was 5mm (or so) to the rear of where it should have been. Probably not to much of an issue though (or would it have been?).

The bigger problem only became evident when I suspended the aircraft by a string fastened at the CG (on the CL of the aircraft) - it became very evident that one wing was much lower than the other (by 2cm!). Clearly one wing was heavier than the other (don't ask me how on earth this could have happened with an ARF aircraft). I used some plasticine as a temporary weight on the lighter side and re-tested - now the wings were level.

Well, the difference in flight was remarkable - I had no idea that it could cause so much of a problem. I think the combo of rearward CG (is 5mm a big deal?) and unbalanced wings caused my problems.

Now just have to focus on the flying bit - thanks for the help guys.
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Old Jul 30, 2006, 08:56 AM
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Quote:
my CG was 5mm (or so) to the rear of where it should have been. Probably not to much of an issue though (or would it have been?).
5mm aft for me was not welcome. It needed the 50mm to fly well for me.

And yes a heavy wing can do weird things, mostly for trim. Mine were identical in weight, right to the gram.

The forward CG should help things, it does take a bit or down elevator on inverted. It just became a bit twitchy with the rear CG.

Mike
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Old Jul 30, 2006, 12:02 PM
Electric Flyer
San Diego
Joined Jul 2006
10 Posts
Quote:
Originally Posted by boltor
Lucas - good luck - it is a well constructed aircraft, but I am just having trouble 'getting it all together' (probably just me though). Keen to hear your experience. What motor / prop are you using?
We are using the Hyperion HP-2213-20 with a 9x6E prop. The recomended set up. Unfortunatly now it is raining here so the flight will have to be delayed for 2 weeks (vacation) unless I can go later on today.
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Old Aug 05, 2006, 02:07 AM
SD_Raptor
San Deigo, CA
Joined Mar 2006
685 Posts
Here is my experience to date:

First airframe had a bad glue joint on the innermost wing spar - destroyed on first flight when wing separated from frame - replaced by distributor at no charge. Second airframe still flying. Motor: 2213-20 with 9x4.5 prop gives good combination of thrust and speed. Control throws at recommended settings - rolls great, loops no problem, all maneuvers but knife edge and right snap are fine. I fly with CG 55mm back from leading edge - gives better inverted performance and is more balanced when rolled over 45 degrees. More forward CG makes nose rotate down too fast during rolls. Left/right balance is perfect. Balance checked by screwing a small eyebolt (like used for wing rubber band) into belly spar at desired CG.

To get good straight vertical climb I added more right thrust. This also helped straighten out loops - much less out of plane rotation and slip.

Knife edge is an entirely different matter. With right wing low, adding rudder results in strong rotation toward the landing gear. If I dial this out with rudder/elevator mixing then all other rudder input manuevers respond badly. Left wing low knife edge is far more neutral but still pitches toward the gear. Snap rolls left well, pulls out high when snapping to the right. I am set up with left rudder being the pull side of the servo motion. Testing the linkage, I see the control rod flexing when I give right rudder by staying very true for left rudder, when the rod is under tension. I will add restraint to the control rod sleeve and see if that helps. If this does not improve right-low KE, I will change to pull-pull for the rudder. I also find that the rudder is very flexible compared to the other control surfaces. There is a large open area in the middle of the rudder. I may peel back the covering and add a diagonal brace to stiffen the rudder.

I will try out a bit of flaperons as well to see if that helps with the landings. But now after 15 flights, landings are defintely improving after using a longer glide slope to drop in more gradually. I beefed up the gear by adding a backing plate inside the fuse and using 6-32 nylon screws and mahine nuts. If I have a really bad landing the screw shear off and are easily replaced. The cowl is getting a bit mangled on the bottom side but flies fine.

The weight of the plane does not seem to be a big issue for me - I fly with 2100 or 1700 lipos. But I am moving from a large heavy (80 oz) Multiplex Magister that is highly modified to perform very well. The smaller light SU-31 rolls faster and takes off in much less distance but otherwise seems quite stable in spite of my flying with the CG at around 55 mm.

Once I get the rudder/pitch oupling issue resolved, the little SU-31 will be a great transition to mid-wing aerobatic flying.

Next plane may be a .40 or .60 sized Fliton or other make Extra or Edge.

Any reviews of the .30 sized Hyperion SU-31 out yet???
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Old Aug 06, 2006, 04:16 AM
Registered User
Australia
Joined Nov 2005
323 Posts
I think I have it sorted out now - 3 good flights today.

The list of things I did (they all look fairly obvious with 20/20 hindsight):
1) Took more care over CG (set at 50mm from LE) (used Randy's idea of an eyebolt at the CG / centreline)
2) Added slightly more right thrust (added a thin washer behind the right engine mounting to angle the motor to the right)
3) Balanced weighting of the wings (one was lighter than the other)
4) Sealed the aileron and elevator hinge lines

Together, these seem to have done the trick - I think the additional right thrust was probably the most important change. I have also set up the aileron differential, expo, rudder to elevator mix for KE and flaperons for landing - these all helped to tune the aircraft in.

thanks again Randy, David and Mike - I really appreciate the helpful advice!
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Old Aug 06, 2006, 07:05 PM
SD_Raptor
San Deigo, CA
Joined Mar 2006
685 Posts
boltor,

Glad to hear that the extra right thrust helps.

You should not need any differential with the semi-symmetric wing and mid wing location. If yu use differential set it carefully to minimize adverse yaw during a roll. Ift should take very little. How much rudder/elevator mixing did you need for KE?

Randy
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Old Aug 07, 2006, 07:54 AM
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Australia
Joined Nov 2005
323 Posts
Quote:
Originally Posted by SD_Raptor
How much rudder/elevator mixing did you need for KE?
Randy - set at 35% rudder to elevator mix for KE, and 20% for differential flap (will try this again at 0% and check).
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Old Aug 07, 2006, 10:15 AM
SD_Raptor
San Deigo, CA
Joined Mar 2006
685 Posts
Boltor - yuour rudder-elevator mix is quite close to what I found. I need 40% or knife edge, about 20% for normal flight, and close to zero for doing hammerheads. Very strange! But in more reading about rudder-pitch coupling, it is not all that unusual. The coupling seems to depend on both airspeed and whethe the plane is slideslipping.
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