mass balancing will help a lot and I have my CG at about 150mm so I could take that back to 140mm with a little weight aft, should not take much to balance the very light elevator. I believe CPLR insisted on square trailing surfaces to get better control surface response even though it would make flutter more likely. I do think digital servos with their much better holding power stop flutter before it can start. At our local field we have had 4 ARTFs lose their elevators and or stabs. Two Seagull kits and 2 Flair kits all caused by flying fast and pulling up. Flutter is incredibly violent and powerful, the trick is to stop it starting in the first place, once it starts solid elevators are not going to help.

Yeah, you can notice in the picture that the stab is braced with aluminum. This particular Synergy belongs to Hammbone. Mine has it's stab beefed up with triangle stock. It has done the trick so far. I believe Hammbone's (Jim's) stab failed at a joint. Some gussets here would help. The tail group is mostly balsa sticks with a few gussets but I think there should be more of them.

Patrick

I also observed that Hammbone's tail failure is untypical for the problems we had on a few kits. If there was anything to break it was the stab, not the elevator.

The actual version of the Synergy has a plain balsa stab with modified elevators with some additional triangle reinforcements at the exposed areas.

The problem we had with the tail of the synergy occurred because the quality of the balsa wood was sometimes way under specification. We always ordered 100 Gr. Balsa, but did receive sometimes 70 Gr. quality (this is for the weight basically good, but not for the stability of the construction).

I fly a kit of the very, very first batch - I never had problems, but I a) braced the tail with 2 mm carbon b) reinforced the linkage with carbon tube around the steel linkage and last but not least use top of the range servos with aluminum arms. There is NO play at all on the tail.

Rgds
Alvin

Just when I thought I had my Synergy sorted out, more problems arise...

I was running through the advanced pattern today on the first flight of the day when I noticed my throttle idle setting was higher than normal... I slowed up and did a couple of slow passes to see if I could slow it down enough to land but I decided I could not get it down in the small field we fly off (well not without hitting the fence at the other end..) I tried pulling the trim right back but still to fast - Nothing major but it meant I would have to fly the full tank of fuel. so I carried on flying making sure not to use the throttle too much as I figured the linkage had come loose and the last thing I wanted for a tail flutter prone aircraft was to stuck on full throttle!
Well eventually vibration caught up with the linkage and slowly the throttle was opening with no control. It started getting interesting! I was flying big circuits to use the fuel up and have plenty of time for a dead stick landing but as the model was getting faster the tail reached a point where it decided to flutter. It was rather violent and I thought I was going to loose my model (for the third time..) It was headed down towards the ground at a rapid rate but I was able to pull out of it and slow down enough to stop the flutter. I had to fly in very tight circles to keep the speed from climbing and use up all the fuel.
I was too scared to try pusing the throttle right foward as I thought it may stick on full instead of just above half as it was...
Finally after about 6 minutes of circling the motor stopped and I was able to glide in for a safe landing.

I haven't checked out the throttle problem - that is simple, just change the linkage to one that won't come loose!

As for the more annoying problem of tail flutter... I am not sure what I will do - I have already changed all the linkages and horns and there is no play in the linkages - there is a slight amount in the JR DS-811 servo gears but that shouldn't be a problem. I expect better from $120.00 servos..
I find it hard to justify buying more expensive servos for a .90 sized model.

The elevator that was fluttering is slightly dammaged at the point where the counter balance comes foward - It had been previously repaired from the first tail flutter incident. I think I will make up a solid balsa stab and elevators to try to stop this... I will also add carbon tubes to the pushrods to try to stiffen them up a bit.

Has anyone else fixed their tail flutter problems? If so what did you do?

and has anyone lost a model in the last couple of months due to tail flutter??

Patrick

Hi guys,

For your interests a friend of mine completely reverse engineered the G-Trick and now not only makes it but also improved some of the flaws like the aileron servos are completely hidden in covers in the wings so no more drag from aileron servos and also he his brilliant craftsmanship reduced the weight to 3300 grams is available for $US 280 made entirely of solarbo balsa.

you have other news? you have a link where to order it? Ciao Alfo.

Patrick
plain balsa elevator is today standard - carbon tubing around the 2mm wire is standard, too

JR 811 ?! - should be enough - however I think this servo doesn't have ball bearings...

Rgds
Alvin

Has anybody had problems with the wing mount and checked out the wing incidence?

Kris

My Synergy 90 3D equipped with YS-110 and Hatori pipe comes out quite nose-heavy. I'd like to balance the plane near 23 cm from the trailing edge.

How did you balance your Synergy 90? Has somebody placed the rudder servo in the tail? Where did you place your batteries?

Jean-Claude

I placed the rudder servo right above the elevator servo. There is a nice slot on either side, and you simply have to reinforce the area before mounting. I tucked the battery in the centre of fuselage, under the wing mount, with lots of foam for a snug.

Hallo

it is not a so good idea to install three servos on the tail... the main problem being the weight which is going to have a negative influence on the 3D capacities of the plane. I did on my plane glue horizontaly a piece of balsa in the fuselage (just behind the direction servo) - there I installed the batteries

A merry X'mas to all around the R/C world
Alvin

Hi everyone, Hope your Synergy's are still flying!

I had mine out last night for a couple of flights while the wind was down and the sun was still up.
I haven't yet started to program point mixes into my radio - it won't need a lot.. just a bit of down elevator in knife edge ect.
How has everyone else set up their synergy? is anyone using mixes?
I notice I have to hold a bit of right rudder in to maintain a vertical up line at full throttle - has anyone increased the right thrust from the standard thrust blocks?

Another thing I have noticed on the last couple of flights, when I do a mid throttle, low pass over the strip I am seeing my ailerons fluttering! I have had big problems with tail flutter, but that problem was fixed. has anyone else had this problem?? I am using JR DS-811's on the ailerons, I think It might be time to upgrade all servos - What is everyone else using??

Regards
Patrick

Patrick,

What you mention about holding right rudder at full power in a climb is exactly what a full scale airplane does. I don't know for sure about the model but full scale airplanes are set up with engine thrust (or some of the older stuff has the vertical fin cocked) so it holds heading at cruise power. If you increase the power the airplane turns to the left and if you decrease the throttle you turn to the right. So on a power off decent you hold left rudder. My guess would the thrust in the model is set up for less than full power as you seldom fly a pattern plane, these days, with full power.

Sam

Mine is ready to go once the weather starts to cooperate

I trust you have Braced the tail planecrazy? or have you got a new generation Synergy 90 with the solid balsa tail feathers?

Be sure to post a flight report after your first flight.

Patrick

Nope, I do not use mixes.I just move the centers on the sticks while I am flying,(a habit I have gained from RC-Heli Flying). After a while you will not think about it at all, it just happen. It is less precise but I fly for fun, not competition.

Same thing here also.[]
IMHO it has to do with the flexibility of the ailerons structure , not the servos you are using. I have FUTABA 9252 on Ailerons, solid pushrods with carbon reinforcement tubes. They still flutter. I think I will make some new stiffer ones and try instead.

Regards
Baper[8D]

Frmo what I have seen on this model, the aileron horn plates in the ailerons are inadequate, as are the supplied horns...

If you replace the horns for more suitable items then there is not sufficient meat to locate them to in the aileron... you really need to peel back a square of the covering, inset a block and ply plate, and then re cover, fix superior horns with a large footprint and you should be better off....

Take a close look at where your horn mounts... hold the servo (or with digis just switch on !) and ush the surface back and forth - look closely at the point of contact of the horn to the surface, and that general area - see whats moving !

Ive seen flutter occur on many models with large surfaces where insufficient attention has been given to the proper spread of load from control rod , thru horn, to surface...

Its not your fault - it is in my view a design flaw and one that ZN will hopefully fix - its an easy job. At the same time they need ot move the aileron servo bay over a little to provide scope for large arms and proper geometry of the control rod..

Nice plane through isnt it !

It certainly is a nice plane to fly! I just love the knife edge capability, in a moderate breeze you can set it up in a high alpha knife edge harrier/elevator whatever.. and will just sit as solid as a rock. The ailerons are wicked, on high rates it rolls at nearly 2 rolls per second! and that rudder!! way cool.

Snap and spin recovery is instantaneous and hovering is pretty stable. Mine is setup a bit on on the tail heavy side but still flys a nice pattern.

Archie, I have read about your concerns about the design about the ailerons, I think you are right about the "proper spread of load from control rod , thru horn, to surface" I haven't looked closely at my ailerons, but I feel the triangular ply mount might be a bit inadequate for the size of the surfaces. I will cut the covering off and add some extra bracing if it looks like the mount is coming loose.

Baper, I see where you are coming from thinking the ailerons are too flexible.. Obviously the focus was in keeping the weight down on this model. I feel they have pushed the envelope to its limits, however the craftsmanship is so good it gets away with it. If a chineese model was built this light I feel it would break apart on the first flight!
If you do build stronger ailerons, let us know how they work, and if you still get the flutter. I am really concerned that I might loose an aileron in mid flight, normally this wouldn't be a big problem, but the ailerons on this baby are so big it would be like loosing half a wing!

Safe Flying,
Patrick

I think flexibility in the aileron is of secondary importance and should not be the cause of the problem...

In essence, with the control locked and you force the surface, the top of the surface at the horn point should do exactly the same as the bottom of the surface...

This is achieved one of two ways, a good plate locked into the ribs of the aileron front to back, or a good plate that is attached solid through the aileron to the other side with no gaps in between. with th epower of todays servos and peoples attention to descent control rods, and hopefully control horns (not always !!) the bit that sometimes gets forgotton now is the need for strength and weight distribution in the surface... a chain is as strong as the weakest link and all that !

NZ Scythe


I do have the new generation. I have braced the tail as well. I am kinda hard on planes and push them to the limit. Will let everyone know about the maiden flight

Hallo

just would let everybody know that since a few days, new aluminum horns for the ailerons are available and now part of the kit.

This horns (blue colour) are just fixed with four small screws on the plywood plate that is factory installed (like the larger F3A planes)

Alvin Braeckman

Thats good news Alvin and addresses the control horn quality perhaps but what about the position and support for the ply plate in the aileron ?

I had another 3 flights with my Synergy today, I didn't notice any aileron flutter... I was really throwing it around too.
I have stronger nylon horns on mine, I notice there is still a bit of flex in the horm but nothing major. I will probably replace with something more substantial when I get around to it.

I set up point mixes so it will knife edge straight while only holding rudder input. now it flys really sweet! only needed about 4 clicks of down elevator to hold it nice and straight.

Alvin,

Any pictures of these new horns?

Derek

will do some tomorrow - hope I am too stupid to place them in the web.....

rgds
Alvin