Diabolic and tail flutter
 

I wonder if anyone else has had trouble with the Diabolic (full flying stab) and stab flutter and if you found a solution. I would also like to hear from anyone who has one of these and is not having trouble with flutter.

Thanks

Bill

Diabolic and tail flutter
 

I have one that I have been wringing out and I have not had any problems so far. Make sure that the arm inside the fuse is very secure on the carbon fiber rod. Mine is screwed and glued. I also glued on the stabs, but don't think that will matter. Don't skimp on this servo. Use a very strong servo here. I am using a JR 8411 on 6v which gives me @ 194 in oz torque (if I figured that right)(its 155 in oz at 4.8v).

Mine is set up with 70-80 degrees of throw each way and I have been flying it very agressively. It is amazing what this plane can do.

Use a strong servo and make sure there is no slop in the linkage and you should have no more problems.

Jim

Diabolic
 

I also had an issue with tail flutter. There is another post on this...I came to find out that the carbon spar needs glued to the bearings. That has removed the slop from the spar, however mine still has a bit of flutter. Servo is a Hitec 645, which has plenty of holding power.

After doing some research on the matter, I come to find out that balancing the elevator should solve the problem. I added 1 once of lead to each half to test the idea, however my engine did not want to cooperate...so maybe Wed.

Hammbone...what motor and prop are you using?
Thanks,
Eric

Diabolic and tail flutter
 

I am using a Saito 100 with an APC 15 x 4w prop. I did glue my carbon fiber rod to my bearings, or I should say that I filled the gaps with glue (square rod in round bearing).

Jim

Still Having flutter problems
 

Jim,

I added some weight to the elevator hoping that balancing them would work...however the problem still persists. After reading another post I turned the radio on and flexed the elevator, low and behold, flex in the servo tray, I also noticed the servo itself seams to have some play in it.

My question is...how did you connect the carbon push rod to the elevator servo and how far out is it connected to the servo arm.

Thanks in advance for the help.
Eric

Diabolic and tail flutter
 

Eric,
I connected the rod to the servo arm with the supplied connectors. (ball link)
It is pretty far out on the servo arm so I can get all that throw, If I remember right it is in the last hole on an aluminum 1 1/4" servo arm.

I don't mean to step on any toes here, but the first thing I would do is get rid of that Hitec servo. In my opinion, Hitec is not a very good servo. I have tried them and had nothing but trouble. They strip out easy they don't center well and they aren't very strong.
I know there are lots of people that like them, but in my opinion, you get what you pay for.

One more thought. I never fly this plane fast. I manage my speed with the throttle and fly to have fun and try wild manuevers. I don't fly it like a pattern plane. If you are flying yours at a faster speed, that may be why I'm not getting flutter and you are.
Just a thought.

Regards, Jim

Diabolic and tail flutter
 

Jim,

Thanks for the input.

I am begining to think you may be right on the servo here. I have alot of movement in the shaft of the servo with the supplied connections...it seams to be pretty high relative to the top of the servo which is putting a pretty good load on the the output shaft. The JR's must be stronger here.

As far as speed goes, I am running a Saito 91 with a 14x6 prop and get the flutter just after lift off and at anything above 40% tthrottle...so far all I have been comfortable doing is basic loops and rolls to see how the elevator is going to react.

By the way, how do you have your 100 mounted...sidways or inverted?

Thanks again.
Eric

Diabolic and tail flutter
 

Eric,
My Saito 100 is mounted inverted. It sure fit nicely!

Jim

Diabolic and tail flutter
 

Will a Saito 91 3D good with this plane? What prop should I use?

tail flutter
 

I had a Diabolic (just sold it) with a Saito 100 and an Apc 16 X 4W prop. I never had any tail flutter but I never let it fly fast. And how fast can a 4" pitch prop move it anyway. I put dozens of flights on the plane and loved every second of it. My suggestion is do not use more than 4" of pitch and you will stay out of trouble.

Diabolic and tail flutter
 

Mecam,
A Saito 91 should do great on this plane. I would try a 14 x 4W apc prop.

Maybe Eric will tell you what he thinks since he is using a Saito 91 on his.

Regards, Jim

Diabolic and tail flutter
 

I do have a Saito 91 inverted on my Diabolic.

If / When I get the flutter out of the darn thing I will let you know what you think.

So far I have tried a 15x4W APC and a 14x6, but I can't really say which I like better.

Jim - are you using a glow driver to help start the 100? How does it run inverted? Also, do you have any experience with the 14x4W on the .91 ... is it going to be enough prop?

Thanks,
Eric

Diabolic and tail flutter
 

I tried to order the Diabolic from espritmodel today but none in stock. Although they have a new plane in stock called the Diablotin TOP FG. Same as the Diablotin FG but with full stab elevator. Can't wait to get it and should be here by Tuesday. I'll be using a Saito 91 and Zing pro 15x6 for a start.

Diabolic and tail flutter
 

Eric,
I just use a handheld glow starter to start my engine like normal and it runs fine inverted. I don't have onboard glow.
I don't have any experience with a 14 x 4W on a Saito 91. I just know that the 15 x 4W is working great on my Saito 100 so I would think the 14 x 4W would be good on the Saito 91.
Remember you should only be going to full throttle in vertical manuevers with this plane and even if it is a little under propped, you will be managing the rpm's with the throttle.
On 3D or fun-fly type planes, I like to have a prop that will rev up quickly and respond almost instantly to throttle changes.

Regads, Jim

Diabolic and tail flutter
 

That makes great sense...never really looked at it that way, but you are 100% right.

However, I know I am getting unhealthy flutter at an extremely low speed. I added a brace to the top of the servo mounting plate, I am also going to change out the existing servo and/or arm and give it another try with a 14x4 prop...althought this is what I am using on my Saito 72 I know a 15x4 apc is too much for my 91...takes for ever to spool up.

Again thanks for the help, I am hoping I can get to fly right before I just decide to sell it.

Thanks,
Eric

If you can think of any thing else, all ideas are welcome.

What 2 Stroke?
 

Hi all, what 2 stroke would you recommend for the Diabolic? I was considering a Jett 76 or 90. Would an O.S. 91 FX allow good vertical for hovering etc? It is a bit cheaper than the Jett. I want to do this the right way the first time, and have plenty of hovering power.

Thanks,

John Wells

Diabolic and tail flutter
 

Hi John,
I'm a four stroke man myself. I like the extra torque and running characteristics of a four stroke. I'm just not sure what two stroke to recommend to you, but I would think the O.S. 91 FX should be good.

If I remember right the kit calls for a .75 two stroke.

Hope that helps, Jim

Diabolic and tail flutter
 

Talking about flutter again, I also had flutter and got worse on the 3rd flight, and this is what I found.

The bellcrank in the elevator spar got loose, after tightening it got much better but still flutter at half throttle ,I'm using a Magnum 91 inverted 14/4 on wildcat YS 20/20 and OS F (it works just great),also I'm using a Hitec digital 5246 (I guess ) on 6V but even if they call for about 110+ Tq and 250+ holding power is the backlash on the gears what is causing the slop and thus flutter, so I think the answer is to get a JR servo ,anyway is cheaper than the airplane.So it is not the airplane or push rod,check the backlash(play) in the servo gears.

I'm also having problems to do the Harrier, I also have 6 flights on it all with wind of about 10-20mph, but that's the day a got to fly ,not much of a choice!. :confused:

Any suggestion on CG, etc?

The Kulbuto is a really nice maneuver to see!. :D

By the way on two strokes Stephan Laurens (designer) fly the Diabolic with a Super Tigre 61 in contests.

Diabolic and tail flutter
 

I was doing some looking last night and foung the exact same thing as apereira.

I am going to look into a new server and will report back. I am also going to switch to the 14x4 prop...if that does not give good performance then I will switch to a brand new YS 91 FZ.

What other servos are good, I have more Futaba and Hitec than anything else?

Thanks for all the input.

Eric