box55555

Have one of Alan's, Elans fitted with a super sport.

Had fourteen flights so far. 6 of tarmac and 8 of grass.

It flys great but have a problem with the elevator feeling. The inverted bunt is the worst. It is very vague.

Have the recommended throws and a pair of DS821's. The C of G is somewhere near, as a minimum of push is required upside down.

Anyone else having similar issues and what should the incidence on the rear wing be.

mick15

You’re right they do feel a bit woolly, I think it’s the negative airflow interfering with the tail plane, a humpty bump with a half roll in the up line is even worse the elevator seems to stop working altogether.

This phenomenon is a bit strange as my XL exhibits none of this feel, I can do a horizontal low level square eight with the XL a manoeuvre I certainly would not try with the Elan.

m

gooseF22

It should sit on its tail at landing fuel load on the gear. Even with that the elevator is up 2mm or 3...

Sean raised the tail of the stab for incidence, as did I. I used one washer. It helped a bit. 821's might be a bit light, you could be getting blow. I would increase the elevator to a metal servo with 90oz or greater torque in the elevator. If you strip one, it will cost you the plane.

I used max throw with alot of expo. can never have enough elevator when you need to swap ends... to a degree..

Make sure the tail booms are tight and done move too.

gregg f

My Feedback: (20)

I used 8411's on the elev. 200 flights and a positive feel.......

box55555

Thanks for your imput guys.

Will upgrade the servos and increase the throws slightly. The only problem with that is if you push to hard the airframe will flick out.

Luckly it was very high before giving it a try.

Stobe777

My Feedback: (1)

I have the same servos and a Wren 120 in mine. On an engine test run I noticed the elevator shaking on full throttle, so I did shim the engine front end a bit to direct the jet down and away from the elevator. C of G is as it should be, and I need a bit up elevator to fly level. The servos are carefully installed so that the maximum movement is the maximum elevator throw. So far these servos seem strong enough, when using the whole movement. I may shift the CG still a bit more aft.

TP.

mick15

I don’t believe it’s anything to do with servo power, if I increase the throw of the elevator mine will flick, which proves to me it’s aerodynamic.

m

gooseF22

My opinion for what its worth:

THe servo motor is strong enough but the gear train is still plastic. Thats not the point. Its all about handling flutter. Its not strong enough to handle any flutter at speed. You should be running metal servos on a jet flight surface. or HBs. I like the 821 servo, I run it on my 3d birds and everything else, but not on a jet. When you pull negative G, you are also fighting the venturi effect of the exhaust flow. If you dont believe me, go full elevator down and hit your smoke and watch the turbulence at part throttle, to simulate wind flow. Remember the airfoil is semi symetric so it will always be harder to push out.

I also used 1-2 degree downthrust. I think its about right.

BaldEagel

This has come up on the "Elan has arrived" thread and the opinions have been divided, except that the incidence pins need to be glued into the stub wing, to prove this rig the whole ariframe and grab hold of you tail and move it up and down, it shocked me how much movement there was.

I would not use anything else, but metal geared digital servo's on a main control surface.

I don't use a UAT and all my batteries are in the back under the tank, using a P120SX, my Elan has never flicked out or run out of elevator, all set up as it came out of the box, roll rate is very impresive and so are flick rolls, humpty bumps can be performed very quickly in fact on one reversal according to my GPS I have pulled 9.6G without any flick out or problem, so the long and short of all this is check your incidence pins I think your booms are moving.

My two penny worth.
Mike

madmodelman

I agree with the the guys who say the 821 is NOT the servo for the tail of an Elan, I use them on my Sprint all round except elevator.
They are great servo's but in imo not up to the elevators on an Elan, I know we all seem to go over the top nowadays but I use a couple of 12kg Savox's on my Elan and have no problems whatsoever.

gooseF22

Agree here too... lived it..After my "hard landing", the booms were much sloppier. Had to tighten them. Also make sure your stab is stiff. I had stress cracks in the stab after 50 flights and one hard landing. It twisted easily. Ben burden noticed it in how sloppy the pitch control was and we landed it and found it when pulled apart. Thats something to watch more over time than new.. But the pins might be a little loose.

mick15

If I may say so you guys are completely missing the point of box55555’s post, he is referring to negative elevator performance and I completely agree with him it feels woolly and soft in some manoeuvres and if you keep applying more the model will flick out, I have had two Elans and they are both the same. It has nothing to do with servo power or boom stiffness; it is though an aerodynamic phenomenon.

As I said before my XL will perform full elevator negative manoeuvres and stay perfectly on track, the XL elevator feels the same negative or positive.

m

BaldEagel

There is obviously some difference between airframes, some have this problem and some don't, all we are trying to do is suggest things to check, rather than boom stiffness its the play in the incidence rods that are screwed into the stub wing that cause the tail movement, it has been mentioned before to Hysol them into place especially if you are experiencing elevator problems, like flicking out and a change in trim before and after manouvres.

Mike

madmodelman

With due respect I don't think we are stupid enough to be missing the point Mick, just trying to help the guy out.

As I said, my Elan will do everything in the book with no problems, aerodynamics are influenced by a servo's ability to do the job, what appears to be ok on the ground is not the same thing as flying at 150 mph which exerts considerable loads on the elevator servo's, Mike is quite correct also re the loose boom syndrome.
All Elans come out of the same mould/jigs etc. My Elan is perfect so something else is causing the problem assuming the thing has been assembled correctly.

box55555

Hi Guys

Please do not fall out over this.

Have some fresh ideas to try, which was all I needed. Mick is right though, my intro elevator feel was the same either way up. This airframe is definately not.

mick15

We are not falling out so far as I know, just contributing to a discussion.

What puzzles me in all this discussion is though, I have never experienced the trim change and possible elevator anomalies due to boom/wing rod fit.

The boom wing rods on my XL are so floppy you can lift the back end nearly two inches, the aircraft performs flawlessly, no trim change whatsoever and no woolly feel to the down elevator?

I have a pair of JR 8511s in the tail of my Elan so can rule out servo power I think. The manoeuvre which shows up what is being discussed is for instance a tight negative half loop at the top of a humpty bump where the model tends to want to fly off at a tangent.

This condition I believe is either jet wash under the tail plane sucking it down (this was the problem with the Bobcat) or the wing section, which is not symmetrical behaving differently during sharp negative push. Either way I cannot see this being due to elevator power or boom movement.

m

jmo..

BaldEagel

ORIGINAL: mick15

We are not falling out so far as I know, just contributing to a discussion.
Agreed

What puzzles me in all this discussion is though, I have never experienced the trim change and possible elevator anomalies due to boom/wing rod fit.

Neither have I, but lots of people have, so can not be discounted, have a look on the " Elan has arrived" thread

The boom wing rods on my XL are so floppy you can lift the back end nearly two inches, the aircraft performs flawlessly, no trim change whatsoever and no woolly feel to the down elevator?

Are you saying that your tailplane can move two inches out of alignement i.e. change incidence and you don't notice a difference?

This condition I believe is either jet wash under the tail plane sucking it down (this was the problem with the Bobcat) or the wing section, which is not symmetrical behaving differently during sharp negative push. Either way I cannot see this being due to elevator power or boom movement.

If it is jet wash it should have an effect in straight and level flight by a noticable change from low too high power, as I said some have experienced this, but the majority have not.

m

jmo.

Also just my opinion.
Mike

mick15

Yes Mike I have been following that thread.

The XL has two carbon spars to the Elan’s one but like I said the whole airframe is loose, the booms move up and down the outer part of the wings move and you can “lift the tail two inches! When it takes to the air it is rock solid, which leads me to believe that boom movement on the Elan is something of a myth.

m

BaldEagel

Well the protaganists of the change in trim during flight are some well respected jet flyers, they have said that putting Hysol onto the incidence pins to make them solid had cured the changes in trim that they were experiencing, what else can I say, personally I never experienced this, I have also never experienced a lack of elevator authority either, but I do run the C of G well back from that in the manual perhaps that would account for it.

Mike

reo

My Feedback: (130)

re: the looseness in the incidence pins

is this something that some are experiencing right from the get go or is this something that shows up after a number of flights? If this question has been answered previously and I've missed it I apologize.....Thx...Ron

BaldEagel

Ron

It happens after a number of flights, I suppose it all accords how hard you fly and how much G you pull, but I know play was developing in mine so I used Hysol on them to stiffen them up.

Mike

gooseF22

Its possible that the elans with a more forward CG will flick out of negative G sooner. Its possible at negative g that we are getting some blanking from the intakes. that with the semi sym airfoil just makes it less efficient at negative G.

Its possible. However I did see good negative G performance overall once the stress cracks were discovered in the tail. If you are experiencing this, try sealing the gaps on the tail and see if it helps. Just use servo tape on top and bottom. I wondered about the turbulence on this joint in general.

If I build another, I will seal all the gaps.

BaldEagel

To a certain degree I agree with Goose, it could be a forward C of G that causes the woolly effect on the elevator, any of you guys who have experienced this effect care to let us know where your C of G is?

Mike

The Bush

Mick
i just thought it was my crapy flying , not the same as the intro which is rock solid in inverted flight , intro seams better than all of the newer designs in my opinion.
Neil

box55555

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