Dave Patrick 330L Aileron Flutter
 

SEEN THE SAME THING THAT DAVROS INCOUNTERED AT OUR FIELD. VERY SAD MOMENT. THE AIL'S JUST DIDN'T HOLD UP. THE OWNER HAS ADDED 3 EXTRA HINGES TO EACH AIL ALSO.

Stiffner in servo hatch area
 

I'm beefing up the servo hatch area today. Not the root cause but it's definitely not a solid foundation for 140 oz/in servo and it's easy to access and do. A simple spruce/bass wood spar or another 1/16" ply doubler between hatch and trailing edge will eliminate that area as a flexation source. Easy stuff, and when mine goes down, at least I'll know I tried something besides the expensive hardware I put on this bird. Just press your thumb down on the area behind the servo hatch on the TE side and you might see what mine does. To make it worse, with my 1.5" Airwid servo arms, the side of the servo becomes a horn itself against the inside of the wing, do you want your wing sheeting 3D'ing with the aileron?
Jack

Re: Stiffner in servo hatch area
 

Jack

Be sure you do not end up with a servo arm that is longer than the combined length of the hinge center line to the pivot point of the control horn!!!! If this was to occur you could in fact contribute to the the problem of potential aileron flutter. I used 1-1/4" servo arms without a problem and have bevel to bevel throw. From a mechanical concept the best setup is a short servo arm and a long control arm. The concept is known as mechanical advantage. Ideally a control arm combined length of 1-1/2" to 1-3/4" would be preferred, with a 1-1/4" servo arm.

Whoops I lied
 

Mike, my mistake, I did use 1.25" arms, gets me up out of the hatch slot with plenty of throw.
Jack

HInges
 

After looking at my CA hinges, one ailerons hinges looked to be cracking. I believe these hinges were the Greatplanes CA hinges. I had bought more hinges, due to adding additional hinges initially. After noticing this, it gave me good reason to redue the aileron hinges. So, I did the unmentionalable, and ripped off the covering on both wings, and Im now installing Robart hinge points. I had to take covering off, cause Im puttng in hinge mounting blocks for the points. Anyone that is using Robart points, I would recommend doing this, as the leading and trailing edges do not have enough meat to glue too! Yes this is alot of extra work, but Im hoping it will be worth it. My elevator and Rudder will still have the CA hinges that were included within the kit, as they look just fine. Im using 6 hinge point hinges per aileron. One hinge point will be glued within the balsa block of the control horn.

another one bites the dust!
 

One of the better pattern flyers was doing a madien flight on his DP300 extra which was built by one of the better pattren builders and the following happened:

T.O. and level flight was ok. He then slowed down and went to high rates to test the roll rate, first left the right. When he rolled right he heard that dreaded noise. the right ail seperated followed by the left. Powered at idle she flat spun in.
He was running a new moki 2.10.....the ail ca hinges looked like they were cut clean....all still bonded to the wood. Yes the builder knows how to do ca hinges and many new pattern ships use ca hinges so........................?

Ouch
 

Sorry to hear about the crash.

Do you know what the rest of his setup was? Prop, servos, links, etc. I flew mine for the first time last week with NO sign of flutter but I did a great deal of work on it before hand. My setup is below for anyone who is interested.

- ZDZ40 with Menz 22x8
- beefed up ailerons with double cross bracing
- giant scale plastic hinges epoxied from the inside of the wing and aileron ( 1 hinge every 2 inches or so)
- 2 servos per wing (JR 4721's on 6V)
- 4-40 rods with light brass tubes soldered over them for all links
- ball links with stock horns
- sealed gaps top and bottom

Overkill....perhaps but it works. Way too many of these have gone down to take any chances.

Again...sorry to hear about the crash.

T

DP330L flutter (etc)
 

Hi all,

Am about 1/2 done w/my 330L and need some advice. I believe I have the flutter prob. solved with: heavier hardware; beefed-up aileron mount/hatch area; and balanced ailerons. I am installing a ZDZ 40 or BME 50 (have not decided which yet; which do you guys recommend) and need to know if anyone using either of these or any other medium size gasser did anything to strengthen the engine mounting/firewall area. I plan to use a low (8") pitch and need advice as to what dia. pitch prop to use. Thanks in advance for all replies. (Can't wait to start covering my "big" DP Ultimate!!)

Regards, C. Earnest

Engine/prop/mount
 

Hi C. Earnest,

First, with the mods you made I think you have nothing to worry about with flutter.

As far as the engine, it is well know that in this size range I am a diehard Taurus fan. I had a 2.6 in this plane and loved it. Either the 2.6 or the 3.2 work great in this plane.

A 22X8 Zinger Pro would be a good place to start with any of these motors.

As far as the firewall strength you shouldn't have to do much of anything. The only thing I would do is verify that it is well glued.

Balancing the ailerons
 

Has anyone balanced the ailerons with a lead weight on a threaded rod bent forward of the hinge line made to resemble the full scale aerodynamic balance as on the full scale Extra 300s and L?.

I would be willing to add four or even 8 ounces to my plane if it would save it from destruction.

The ailerons will not flutter if they are balanced or so I'm told.

There have been several articles in regards to balancing control surfaces in magazines over the years, one man had attached a wing to a car to test the balanced vs. unbalanced assemblies.

I would imagine that using heavy hardware could make the imbalance even worse.

I have seen most large scale planes with their control surfaces sagging on the flight line when shut off and I'm surprised that more planes don't suffer from flutter.

I am curious about pull-pull set ups. You never hear about a rudder fluttering that is hooked up that way and the linkage doesn't have to be guitar string tight either, at least I haven't yet.

I almost forgot, I don't use CA hinges on planes I want to keep a long time. They will fail at some point long before a robart hinge will.

After going back and reading the whole thread I see that balancing has been addressed and I of course fully agree.

I thought I would mention that the Hitec digital servos actually draw less current that any of the competitors servos, digital or regular for the same torque output and have a lower idle current as well. The Hitec coreless digitals are superior to almost all servos no matter what size in this respect of power to current draw. This was written about in MA and Hitec publishes there current drain. JR and Futaba do not.

I don't know how they did it but they have winners with this product line.

Brian
KB1DTB

DP330L
 

BPryor,

Thanx for the reply. I added 3/16 to the firewall and will leave it at that except for checking all the joints. I have followed this thread and do believe that balancing is the answer to flutter. all else is symptomatic relief.

To SkyPilot One: See a previous post in this thread re: Dick Hanson's 38% (?) CAP. He attached a 4-1/2 rod/fishing weight to the inboard rib of each aileron; no flutter.

Regards to all, C. Earnest

Dave Patrick Extra 330L aileron flutter
 

Davros, You are not alone. I just destroyed my DPM 330L on saturday due to aileron flutter. I built it exactly to specs and even used a Moki 1.35 which isn't enough to do 3D. Level flight, not going fast at all (actually quite slow) and the plane turned into a vibrating blur for about 3 seconds. Idled down and it stopped but roll control was now nonexistent. It nosed over and fluttered for another 3 seconds before augering in with a nice cartwheel ripping the wings off. This was the 7th flight of the airplane. First 6 used Hitec 615 MG set up as per the instructions. 7th and final flight was with JR 8231's. New radio and I didn't want these nice digital servos to sit there unused. Regardless of what Chief Aircraft says, 88oz digitals are no where near enough for these huge ailerons. And no, Dave Patrick did not respond to cordial and informative email concerning their flawed plane and or instructions. Very disappointed. The plane really did fly nice when it wasn't fluttering into destruction. After reading these posts, I am tempted to try again but with twin Hitec 5645 MG per wing and Robart hinges and a Moki 2.10. Its not speed that kills this plane regardless of their website. I think its the size of the ailerons and the critical need to keep them totally stiff with slightly biased twin ailerons. I wish their first rate intruction manual stated that.
Bob

Dave Patrick 330L Aileron Flutter
 

"I am curious about pull-pull set ups. You never hear about a rudder fluttering that is hooked up that way and the linkage doesn't have to be guitar string tight either, at least I haven't yet. "

Unbalanced weight and gravity causes flutter. The rudder hinge is vertical so the rudder is not unbalanced unless the airplane is in a bank.

Dave Patrick 330L Aileron Flutter
 

Hey Bob757FL
Sorry about your loss.
Did you strip the gears in the JR servos & did you use 4-40 push rods?
Thanks
I'm getting scared. :rolleyes:

Dave Patrick 330L Aileron Flutter
 

I believe there is also the issue of aerodynamically balanced control surfaces. The balanced surfaces are those which have control surface movement in front and behind the hinge line.

Dave Patrick 330L Aileron Flutter
 

Was that a nylon gear or metal gear servo?

Dave Patrick 330L Aileron Flutter
 

Bob757FL. Awefull sorry to hear that. How many does this make that we know have gone down due to aileron flutter?

Question(s) for all: Where/how did you mount your ignition switch on your DP Extra? I'm new to gas. I know it needs to stay as far from the flight electronics as possible. I have the BME 44. I was thinking of shock mounting the switch to the front of the firewall and running a wire out through the wood fuselage flange where the cowl mounts, but this would mean that I would need to cut a small slot in the back of the cowl, about 1 inch long, so it would slide over the rod to the switch.

Where can I get those nylon 4-40 bolts for mounting the canopy?

Dave Patrick 330L Aileron Flutter
 

Kat,

I mounted my switch in the flange that the cowl attaches to. I am using a FROMECO switch so I just had to drill a hole in the cowl.

You can get those nylon bolts at most of the big hardware stores. I got mine at the local Home Depot in the screws and bolts section. They work great and look pretty good too.

Oh ya...I looked at your home page and those are some damn enormous kat fish you're catchin there!

Good Work

Try opposing sides of fuselage......
 

Kat, just keep your ignition switch on one side of the fuse and the Rcx switch on the other. Hang your ignition battery on the same side of the firewall box as the ignition switch. Tie-wrap your excess wire in bundles against the fuse sides. The fuse is so wide on this plane you won't have any cross-talk.

Wing Flutter Too...Food for Thought
 

In some posts about flutter associated with the DP Extra, I've noted some observations where the wing trailing edge and tip sections fluttered along with the ailerons. I couldn't believe this when feeling the rigidity of my DP wings. But tonight I was comparing a few things to my latest 80" ARF project (WM Extra 300s) and there is a considerable difference in the wing tube placement chord-wise. Both planes have the same root chord. The DP spar tube is 25% of the root chord (4-5/8")away from the LE and the WM is 33% or 5.5" from the LE. The recommended CG of the WM Extra is 6.5", ...much closer to to the spar than the DP Extra where a 6.5" CG is popular for 3D. If CG is the epicenter (pun) of the wing loading, would a spar so far forward allow more torsional flexing in the wing section aft of that? To think out of the box, maybe the wings flex first, starting secondary aileron harmonics. Flip side is classic - maybe the ailerons start oscillations that move up through the wing structure. The slow speed is starting to be a commonality. I used to wonder if it was gasser vibration at lower RPMs that start the phenomena. Nice thing about the WM Extra, the wing is fully sheeted from LE to TE, out to the middle of each section's span. The ailerons are fully sheeted, and much less flexible. They are only 3" wide compared to the 3.75" DP aileron but still generous. Metal hinges came with the WM kit.....seems like yesterday I was buying a box of crayons for the DP C/A hinges. Not saying one plane is better than the other, both planes better behave or I'm gonna kick and stomp their remains in the presence of sinful, onlooking Parkflyer Gods. You can bend over for them with no flutter-butter required.

DP website ???
 

Well, after all my hard work correcting the mistakes of one DP extra 330, guess what? They have new ones coming in Sept. with the mods done! Check it out on the DP website. The new ones are coming with dual aileron servo bays, and also a more aft wing mounting. They have or are moving the wing back some to get the CG correct and so you can use that lightweight engine you bought for it! Well, I hope that my old DP 330 that is brand new, and carrying the G45 to balance it with per DPs so called approval over the phone, will survive the first flight! Obviously there may be a problem with this aircraft on the first couple runs. Good luck to all, and I will update when i get mine completely modified.....good grief!

DP330L flutter (etc)
 

Jack,

BRAVO; finally some independent (out of the box) thinking! And, BTW, some of the first intelligent analysis of the problem. I wish I had of said that :-) (Note: I said SOME of the first intelligent...... Don't everyone out there get their panties in a bunch ; just count yourself in the "some".)

Since 1/3 of the MAC is normally the CG, which should correspond to the "center of lift" of the wing, I suppose having the wing tube forward of the CG could cause torsion of the wing about the lateral axis resulting in the "non-classic" flutter-mode: "Wag the dog", so to speak. I do not know how much force would be required to initiate this sequence of events, what do you think?

This is a powerful lot of thinking prior to the first cup of coffee in the AM, so I disavow any incorrect conclusions and you can't prove a thing..................

This post will self-destruct in...........

BTW, I like your humor, also.............. Keep it up :-)

Flutter
 

I posted in an earlier thread that you guys may not have seen. I observed the flutter on my DP Extra 300 during initial flights. The wing tips and ailerons fluttered at extremely slow speeds and please, trust me, after 22 years of R/C, "high speed" had nothing to do with it. I am positive that the entire wingtip(s) were fluttering, not just the ailerons. It may have been that "tail wagging the dog" thing. I was making changes and flying it, constantly trying to stop the flutter. Initially, I beefed up the aileron servo rib bays and it didn't help. I had the gaps sealed and used rocket city ball links with JR 120 oz plastic gear servos, carbon rods w/ titanium tips. During a test flight I lost both ailerons and landed it inverted in tall grass with rudder and elevator. No damage. After corresponding with Dave Patrick, and per his recommendation, I got rid of the rocket city ball links and switched to 4-40 sullivan gold'n clevis'. I decided on my own to install the extra servos out towards the tips. I changed the servos from JR's to Hitec 5625 metal gear, digital servos, 4 total in the wing. I was very lucky, no one was injured, and I was afforded a second chance. I've since flown mine with a Moki 2.10 and a 20X10 prop, full throttle, with no flutter. I know some of you have been re-working your aileron framework for rigidity. Some concerned owners stripped their new covering and discovered that their ailerons came with cross-bracing inside, but mine does not have that. I wonder why some have it and others don't? From a consumers position, for example, I watched Horizon handle the wing failure of their H9 Edge very well. I assume they assign someone to monitor the Internet and address dangerous issues such as this. I haven't seen any replies in our threads from DP Models. This is not only a costly and frustrating issue, but a very dangerous one as well. If even "warranty replacement wings" (or ailerons) were offered, I'd be very happy. The DP Extra is a great product but a few of them obviously have a serious safety problem that needs to be addressed. My recommendation is to not do what I did, ie., a little wood work and test it. Go for what's tried and worked, the second servo. If you think this is overkill, contact one of the several owners who lost their Extras on the first slow trim pass. Please be very careful on your first few flights and watch for the flutter.

JW

Dave Patrick 330L Aileron Flutter
 

Just another incident:

A member at our field flew is DP 300L on its maiden flight last week. Three minutes into the flight the left aileron separated and got jammed into the elevator. The plane was a total loss. DP gave him a new one at half price. He has the 1/4 scale dubro hinges spaced about 1 every inch. He has flown the new one 5-6 times with no problems. It still cost him $200 for what I feel is a DP design problem.

Dave Patrick 330L Aileron Flutter
 

It cost that person $200, and the time, and energy, and emotional distress. And fortunately no one was injured....