DP Edge 540
 

I finally got around to flying my DP Edge.

It's setup with the elevators mounted in the tail as well as the rudder pull/pull relocated to approx. 3/4 of the way to the tail. This allowed my specific model to balance at 5" with a Moki 1.80 in the nose and NO lead. Battery is also mounted where I have the rudder servo and "new" servo tray.

Take off was excellent...very smooth and controlled. A few clicks of left aileron trim had it flying hands off. After a few basic circuits and mild aerobatics...including a half throttle 3D throw aileron roll the unexpected occurred. I was at approx 300ft cruising at approx. half throttle at about a 10 - 15 degree dive and then suddenly the left aileron said braaaap. Slammed throttle to idle while hoping airspeed would bleed off before you-know-what. I regained control shortly after hitting idle and made a very slow circuit around the field trying to lose altitude without making any "sudden" moves. Got the airplane positioned the airplane over the runway at 50 feet to check for d-a-m-a-g-e flying at just a bit over idle now. Holy Moly...the aileron servo was hanging, only attached by the 4-40 rod connected to the aileron horn. Nursed the plane around the field so that I could get the idle dialed in so that it would settle in and landed without further damage.

Inspection revealed a bent 4-40 rod; the servo appears to have separated from the servo mounting plate causing – ah, well flutter; aileron hinge points are fine; the servo still operates seemingly without a hitch. The servo did blast through the top of the wings utltracote.

I'm now in the process of reinforcing the servo bay with epoxy and cloth. Additionally I'll be replacing the 18x10 with a 18x8 as well as reinforcing where the mounting blocks attach to the mounting plate with epoxy and cloth.

I think when I’m done with the reinforcing this plane will be a real performer…time will tell.

FWIW .. The servos where Futaba metal geared 100+ oz/in servos

Mike

DP Edge 540
 

Did the servo mount break or did the screws give way?

DP Edge 540
 

Yeah, I'm interested too. My maiden flight for my Edge is going to be this weekend.
What exactly gave way? Do you mean the servo mounting blocks that you are supposed to glue to the backside of the aileron plate covers gave way? If so, how did you originally glue them in?
I glued the blocks in real good with epoxy and of course, screwed the servo to the blocks per instructions. Should I expect problems? Thanks for any help.

Seal the gap in all control surfaces
 

If you didn't do it already, seal all the gaps on the control surfaces. You might also want to get the Hangar 9 titanium rods. 4-40 rods do not seem to have what is necessary.

DP Edge 540
 

fly3Dnyc,
My hinge gaps are sealed and ready to go!
I am also surprised that you say the 4-40 rods aren't enough. As short as they are, I would think they would do fine. I haven't heard of anyone else saying their 4-40 threaded rod links were inadequate.

mrc,
Do you think your 4-40 rod was bent due to the servo coming loose and flopping in the wind? Thanks.
I have 4-40 rods on the ailerons myself, and now you guys have me worried!

DP Edge 540
 

Nothing to be affraid of. It is what it is. When we start to reinforce the other parts you should complete the process with stronger rods. It isn't that the 4-40 don't hold up, but when the flutter occurs for sure the 4-40 will bend.

DP Edge 540
 

I'm pretty sure the blocks broke off of the mounting plate .. causing the servo to blast through the wing. I also think the rod bent as a result of the block seperation.

Mike

DP Edge 540
 

Just another note:

The blocks were epoxied to the mounting plate using 30 minute epoxy. I've now attached the blocks with 30 minute epoxy as well as fiberglass cloth on one side.

The gaps were all sealed prior to the flutter.

The servo still works fine.

I would recommend reinforcing the entire servo bay and mounting block/mounting plate attachment with epoxy/cloth.

Mike

DP Edge 540
 

mrc100.

I have the same plane, with a DA-50 on it. I wasn't sure how the aileron servo mount blocks would hold up as it seemed they would eventually break loose. Not a very strong joint as it's just butt glued together. Cure for the problem is to glue them in as normal, and in addition, screw into the mount blocks from the outside. I figured there's already 4 screws holding the servo tray in place, what's 2 more. I know it won't come apart. I have a picture of how mine are done in my gallery. Looks nice and clean.

Kelly

but glued joints
 

I have found that but glue joint are a weak point if the epoxy is not properly mixed. This is especially true if part of the but joint is hardwood. I have found that it is possible to seperate hard wood from whatever it is glued to with enough vibration and pressure. Whenever I am gluing things with epoxy, I follow a new proceedure. I do it on things like spars, stabilizers etc. I take a dremel and make samll holes in both parts in a random pattern. The holes are not very deep (definitely not drilled "through" anything) Depending on the thickness of the wood at the intened point of gluing, I either make small holes or small indentations. By doing this, the epoxy in the joint will have something to grab on to or "key into" I know this is probably not the greatest description of what I have done. This gives the joint added strenght, especially on but glue joints. When mixing epoxy for the joint, make sure the same amounts of epoxy and hardener are used (I know it seems elementary but I have seen cases where this was not done and it comprimises the strength of the bond) When applying the epoxy, make sure you work it into the indents thoroughly. When the parts are mated and the epoxy cures, it will be much stronger.


Baretta92 :cool:

DP Edge 540
 

I would recommend that after you mount your servos, that you remove them then C/A the mounting block with thin C/A. This will strengthen the block as well as the screw holes.

DP Edge 540
 

I always harden the screw holes with thin CA after the initial servo mount. The screws did not seperate.

I had similar thoughts about adding a screw from the outside...or creating more surface area for the bond. I chose to use cloth and epoxy and it appears to be much stronger. I also used a small amount of cloth and epoxy inside the wing to secure the plywood mounts to the wing.

Mike