Ben Diss

My Feedback: (23)

I wrecked my first DP Extra (due to pilot error). One wing was destroyed outboard of the last two ribs. Rather than fix it, I decided to disect it.

I used the Sullivan horn according to Dave. I drilled the holes, screwed on the horn, removed the horns, thin CA'd the holes and reattached the horn. I tried to rip the horn off the aileron. It did not pull out. In fact I broke the whole aileron while removing it. The plywood mount detached from the aileron taking with it the LE of the aileron. I am convinced that his method for the control horn works.

-Ben

John Wells

My Feedback: (10)

It went fine. I have a Moki 210 and went full throttle, no flutter. I have one question though. How would I use a "mini" servo as Dave mentions, and still get the same throw on the arm?

Thanks,

JW

TheEdge

My Feedback: (788)

For what this information is worth,

I was the very fortunate buyer of Bill Pryors Extra. I might just add that this man is an above and beyond individual. He not only did one stellar job of buidling this kit, he has continued to give an overwhelming amount of information on its set up and characteristics. Never ceasing to go out of his way to give un solicited information.

Now, to the subject of aileron flex.
I have my ailerons set up with 8411's (thanks again Bill)

With the radio on, I have applied normal hand presure, which in the aviation biz, we consider this to be approximatley 5lbs.

I can not get the ailerons to flex at the outb'd edges.

They have about a 1/32 flex at the most Inb'd edges, closest to the fuse.

I could not imagine that based on this test, that mine would deflect enough to induce flutter during flying conditions

Again, that is only my humble opinion.

I must admit, after following this thread I have had extreme concern about my own plane, but, I do have the added confidence that this plane has been to the prooving grounds and passed the test.

My sorrows go out to those of you that have had a loss due to this flutter phenominum.

Fly4Fun2

My Feedback: (25)

I have been following this thread and tend to agree with the theory that some planes are coming with soft balsa in the ailerons. This would explain the flex and flutter.

I am not a big fan of 4721's. I have several and they are the ONLY servo I have ever had to replace the gears on. The torque is there, and they center beautifully, but I don't think the plastic gears stand up to the vibration of a gas engine. I suggest upgrading them to metal gears or saving them for glow planes.

One other note on the 2 vs 1 servo. Aileron SIZE has nothing to do with the need for an additional servo. The new Fiberclassics Yak 54 that was unveiled at Joe Nall flew with ONE servo per wing. This is a BIG 40% plane and Jason Schulman wrung it out pretty hard. Granted, they were the new Voltz servos with over 300 oz of torque, metal gears, and even a metal case that is the same size as a 8411 (expected price around $240 each), but it does prove that if everything else is right, one servo will do.

Well - it is a nice day. I am gonna go fly!

Keith

jelaird

My Feedback: (1)

There seems to be something nobody has discussed here and that's the method DP has you mount the wing servo. This is fine in a Sig 4-Star 60, but when mounting, I noticed the wood in the surrounding area of the servo cover was fairly flexible. I think differences in wood density here and servo weight/vibration may cause your servos to "hop" vertically a bit, thus exciting flutter conditions. There are no stiffeners in this area of thin ply sheeting and the little corners for screw holes on servo bay are just glued up under to this ply wing sheeting. I worried as I installed wondering if this would be a problem later. Also, a lot of the disasters mentioned on this board involved "pin" hinges. I often wonder if those installing them are recessing the bevel to allow the bevel to bevel hinge gap like CA hinges allow. Excess gap throws the aileron's own CG back to an area associated with flutter theory. Meaning, the aileron is back there 3D'ing when the wing is not.
Jack

dirtybird

My Feedback: (5)

Its simple to prevent flutter. Remove the power source for the flutter by static balancing the ailerons. I did this on a H9 Extra and was able to recover the AC after a complete failure of the gears in one of the aileron servos. There was no hint of flutter even with the aileron completely free. All it takes is a few lead wts and some glue.

bpryor

My Feedback: (45)

Anticipating that that will be the next post in response to dirtybird's suggestion of static balancing, here's a good picture on how to do it for a H9 33% Cap 232 that Dick Hanson put single servos on with counterbalance(this plane's stock setup is dual servos):

http://www.concentric.net/~Dhmodels/workshop9.html

C Earnest

Bill,

Correct-a-mundo!! It is my understanding that truly "balanced" ailerons will not flutter due to the balancing stopping the "lagging" action of the aileron following the flexing of the wing t.e. in each "flex direction" of that trailing edge or section of aileron, if the flex mode is limited to that particular aileron. That is one effective way to stop flutter that has been used for years to a great success. It adds a bit of hardware that may be somewhat unsightly, but so is a pile of balsa and engine metal that used to be a beautiful aircraft and powerplant.

IMHO, most flutter is caused by excessive airspeed. Loose hardware follows as a cause, then poor maintenance.

Just my opinion, FWIW. :-))

I oversped my CG Ultimate on one occasion and just barely got the throttle chopped in time to avert disaster due to fairly well-developed flutter. The plane had around 150 flights on it at that time and had another 100 or so on it and I believe the flutter was caused by worn clevises. It was "ultimately" brought down by radio interference. (read: turn-on.)

Regards,

C.E.

KatManDEW

My Feedback: (6)

I too think that the sheeting where the aileron servo's mount is weak. I am going to add a 1/4" wide ply strip spanning from rib to rib near the aft part of the mount. The forward portion isn't too bad because itis close to the wing spar.

mrc100

My Feedback: (4)

Dave Patrick's web site recommends using nothing more than a 8" pitch prop when using a larger motor.

Mike

Dazzler

My Feedback: (6)

Here is a quote from Dave Patricks Website on the Extra 330

"We get asked about using gas engines many times a day. I can only guess that these engines might be too heavy, but we have not tested with gas yet. Again, as we and other modelers try these out, we will forward the information as we get it. If you choose a gas engine, read above again as a reference to help you in your selection".

Seems the gas engines were never even tested in this airplane, their waiting on feedback from customer. Well I guess this is one piece of info they can add to their feeback.

I usually stay within a manufacturers recommendations on engine choices, but if was never tested with gas, they probably didnt put any Big gas engine recommendations on the kit. Daz...

bjw4072

My Feedback: (6)

I have a DP Extra 330 but have not built it yet as I can't decide what engine is best suited foor it. Even before I found this thread I had intended to counter-balance the ailerons. This has been suggested in other model kits I have owned; for example the Midwest Cap instructions suggest counterbalancing the elevators. I had a Byron Sukhoi with instructions to counter- balance the ailerons. The original Byron kit was designed for a Saito-300 twin and no flutter problems were found. Later, those who installed big gas engines, particularly with poor servos and linkages, experienced flutter. Byron later updated their kit to include instructions how to install aileron counter-balancing.

While tight linkages and powerful servos are needed, counterbalancing the surface removes (or minimizes) the aerodynamic source of flutter.

mrc100

My Feedback: (4)

The information from DP web site which I was referring to was in regards to a Moki 1.80. However, the information was also general in nature regarding larger more powerful engines.

Here's the info. from the site:

5/1/02 - THE EXTRAS & 120 ULTIMATES HAVE ARRIVED!

We stand by saying that a Moki 1.8 is too much for our Extra!
BUT

This is an excellent engine of capable of about 4.5 horsepower. There have been reports of modelers successfully using this engine. We also have had a couple modelers use it and it has resulted in aileron flutter.

That being said, it appears that the Moki 1.8 could be used if one is very careful. You must use a prop of no higher pitch than 8 inches. Probably about 20 or 21 inch diameter is best.

The idea here is NOT to go fast but have very high thrust for 3D and so on.

We have a really neat custom muffler made by Bisson that directs the exhaust out the cooling duct. This is much better than making holes in your nice cowl!


Mike

jelaird

My Feedback: (1)

I agree with dirtybirdy all the way. Aileron CG is definitely the root cause and with todays demand for extreme 3D and larger control surfaces, we live on the threshold of experiencing it or not based on all the factors brought up in this thread. I like those counterweights seen on the CAP above. I was wondering if the large flat tip of the aileron of the DP Extra could be modified with a thin ply tiplet plate that extended an inch or so in front of it with an egg shaped lead sinker cut in half and glued to it. Might even look like a navigation light if you painted it. Don't know how IMAAC rules would effect this however.
Jack

bpryor

My Feedback: (45)

Hi Dazzler,

The statement on DP's site about not testing gas engine's is ancient history. It was first put up there almost a year ago and was never taken down. Before the first batch of planes were shipped last September(I think), Dave Patrick had been flying a Taurus 2.6 powered prototype for weeks, with very positive results. I'm pretty sure they keep saying this to limit their liability because putting a gas engine on exceeds their original design criteria, and they don't want to be responsible for problems arising from using gas engines.

drandles

My Feedback: (8)

I have been flying my DP330L for 9 or 10 months now with a Brison 3.2 swinging a 22x8 Menz (and a 22x8 Mejzlik). The fact that I have not experienced flutter in my ailerons may be due to throttle management, stiff ailerons from one of the first batch of planes, good hardware (titanium pro links, etc.), DS8411 servos, luck, or whatever. I do not baby this plane, however. I do make full power shallow dives across the field with no flutter and fly her knife-edge across the field full bore.

My DP330L is actually up for sale as of a few days ago. After flying my new H9 Cap232 33% I am a true believer that bigger is better. There is night and day difference in doing an elevator with a DP330L and a H9 cap232 33%. The latter being extremely stable in decent.

I am thankful to you guys for bringing this flutter issue to my attention. I did find wear in the aileron clevises on my DP330L. I replaced the clevises and put blue locktite on the threads of the aileron linkage. The blue locktite isn't needed to keep the clevis from turning. It usually keeps the clevis from rattling around and becoming sloppy. You guys may have saved me a crash.

http://home1.gte.net/drandles/radioc...iocontrol.html

Bigger is better!

dirtybird

My Feedback: (5)

This is the way my H9 Extra has it. Only I had to go 4" ahead of the hinge centerline and use 2 oz. It don't look much like a nav light.
I think the the way the Cap has it is the better way. All of that wt at the tips might affect the snap roll rate.

krayzc-RCU

My Feedback: (31)

Dale,
"Bigger is better!"

I could not have said it any better. It's night and day difference from big to even bigger.....
gerald

drandles

My Feedback: (8)

The only time I have witnessed flutter and the destruction of a plane was Woody Reynolds' 40% Carden last year - using a pair of 4721's on each aileron.

It was amazing how quickly it happened. He was flying along straight and level when we heard the hideous roar of aileron flutter. It was loud. I started to think, "he better slow down". Before the word "down" got out of my brain the right wing began to flap up and down. I thought, "Holy crap". Before The word "crap" even got out of my brain the right wing half separated from the fuselage. This all took place in the span of about 2 1/2 seconds. Just count one, two, three and before you hit three the plane was heading for the ground.

I don't think Woody ever figured out for 100% sure what caused the flutter. As far as balancing goes, Woody experimented with balancing. He said balancing caused him even greater problems. He now uses Digital servos - DS-8411's.

I was going to sell my DP330L and sell the buyer some 4721's. I need to keep the DS-8411's for the next (bigger) plane. I wish we knew for certain what caused these crashes.

It is most likely a combination of factors. I'm sure people are using 4721's without having flutter.

Has anyone experienced flutter with metal geared servos (and good linkages)????



Dale

dirtybird

My Feedback: (5)

I don't know what other problems might be caused by balancing but are they greater than losing the airplane?
Digital servo's will help due to the tighter servo control loop but they are quite a bit more expensive than a handful of lead sinkers. And the digitals are not a sure cure where balancing is

C Earnest

Dirtybirdy,

Amen to that............

Chuck E.

drandles

My Feedback: (8)

I beleive he had digital servos in the affected plane and the digital servos went bonkers with the balancing. I can incquire further when I catch him at the field.

I know the digitals are expensive, but the more money I put into a plane the more I want to have digital servos (and metal gears) operating that plane.



Dale

ben flyn

Just today, I told the pilot of the problems mentioned here about his Patrick 330L, 5 minutes later his plane crashed due to the same problem. This was his 5th or 6th flight. The builder of his plane took it off and made a pass by at a slightly above 1/2 throttle speed,then slowed down, then it happened, flutter both sides at the same time! bent both of the push rods, and stripped the 2 servos. The builder/ pilot was able (by luck) to put the plane in, flat upright, into a soft wheat field so little damage was done.

Now that I've told you what happen; I will tell what I think caused it. He has a FPE 3.2 gas engine in it, when he taxied by, I could see the wing flex at the ends making the ailerons flutter, one side worse than the other. All of this due to the ruff and slow idle of the gas engine. When the pilot slowed the plane down he threw the throttle in idle, causing the ends of wings to vibrate thus causing the ailerons to flutter. I think it will only happen at a certain rpm to cause a deadly resonance.

bpryor

My Feedback: (45)

Ben Fly'n,

Thanks for adding your theory on this problem, but I really doubt this is what is happening. When you see the wing shaking due to engine roughness at idle, that is not the wing flexing, it is just vibrating/shaking. Every plane that has a single cylinder gas engine on it has vibration at idle to a lesser or greater extent. There would be an awful lot of planes of all types and brands crashing if this could induce aileron flutter. (But if it's true, it's one more reason to own a Taurus. ) Also, not all the DP 330's that have been reported with flutter have gas engines.

Does the person that owns this plane, or his builder, belong to RCU? It would be great if the builder, after inspecting the plane, could report his findings. It would be great to know his complete setup on the plane, and also it would be great if he checked the stiffness of his ailerons and report that too. If you can ask him to do that, it would be great.

Thanks for the report.

ben flyn

Sorry Bill it WAS the wing flexing on the tips during the vibrations of the engine. There was no doubt. It seem it was starting at the end of the wing tubes. I'm very concerned too, I have a DP330L waiting for the new DA50. I had a client's husband who worked for a company that fixed problems dealing with vibration. I was amazed at what vibration can do to large machinery!! Why not balsa wood? Do forget what the roman soldiers did to break bridges!

What I saw was the aileron moving a 1/2" and the wing tips flexing a 1/4"
It just what I saw....

BTW the outer most hinge was lose too! If it was lose before or if the flutter tore it loose, who knows.

What else do want to know how it was set-up?