Mini Quark build

[johnfireball]

Hi all,
      Broke my quark, one of those unplanned landings due to elevator pitching problems. I had this problem from the start be it motor on or off and was flying in very turbulent winds coming from the east on a westerly slope so was probably flying in rotor. However pitch moment has been a problem even in light winds. I was messing with elevator expo,  dialled in too much,  failed to pull up enough, and took her nose off.
I'm fixing it and have replaced the snake elevator control with a carbon rod with wire ends as I think the snake was bending in the fuse and making control iffy(it was like flying my mini cp heli). I had mixed in down elevator with throttle and it appears to work to control the vertical climb. The ailerons are sorted and work well with lots of expo. Opinion on electric quark so far is, "not for the faint hearted" but will keep trying.
More to come

[Happy Days]

Oh dear.  Never mind John. It is but one set back. May be dual rates might help to tame the beast. I’m thinking that if you used low rate for when the power is being applied (prop-wash over the control surfaces) and a higher rate when in gliding mode.

Of course this does mean you have to keep in mind which switch operates which function on the Tx. I always use the same switches for the same function and have taught myself to “feel” for the position of the switches and whether the switches are on or off.
I found looking down at the Tx to see the switches was too distracting :roll: ….Just an idea!

Another idea might be to fit a smaller prop. If the present one is a 9X5, try a 6X4. The battery would give a longer flight time as a bonus!

Anyway good luck John.

L Keith

[alibodin]

John

Sorry to hear about the Quark. Hope you get it quickly flying again.

I wonder if snakes would be OK if they are secured every so often in the fuselage. Just a thought.

I was planning on using a snake as I have no CF rods around.

Alistair

[EI1638]

I have snakes on my (glider) Quark Micro, and they work fine, certainly for my level of flying ability.

[billscottni]

Snakes need firmly attached at both ends and at intervals along their length. If not they will flex and provide full neutrals and reduced throws.

If it's possible a straight pushrod in either carbon or dowel is far superior

[johnfireball]

Hi all,
      The bellcrank on the Quark amplifies the movement  of the elevator by a factor of about 2. I had to set the servo endpoints at 50% each side to achieve max elevator deflection, so the servo was moving very little each way making any positioning errors critical. Since fixing I have moved the pushrod end into the centre hole of the servo arm whereas it was in the outer hole and used the lower hole in the bellcrank. This I hope will sort the problem.
The snake did work but there was bounce in the elevator (the snakes were moving in the fuse) and with the added airflow over the elevator under power, I wasn't happy with it. The snake will work but I go along with Bill on this.
Model is repaired and now has up ailerons mixed with throttle stick to eliminate the flap effect of the undercambered wing section. Yet to test.

[Fred]

Hey John,

Sorry to hear that, and glad it is already fixed!  :clap:  :clap:

[johnfireball]

A short video of the crash. You can see the pitching problems.
John

[youtube]https://www.youtube.com/v/4-slzgYwv8c[/youtube]

[johnfireball]

Hi all,
       Model is now sorted and is a joy to fly. The elevator is so much better be the model gliding or under power. The aileron up mix with the throttle has cured the pitch up problem. This ones a keeper. Looking forward to flying it some more.
John.

[Happy Days]

The aileron up mix with the throttle has cured the pitch up problem.

This seems strange John, I’ve never heard of it before. :?:  So you’re saying that you have installed a mix so that as the throttle is increased both ailerons deflect upwards slightly do they? And this stops the model from pitching upwards?

L.K.

[johnfireball]

Hi Keith,
           Thats exactly what I did, the reasoning being that the quark airfoil shape has a lot of undercamber at the trailing edge which make it glide well but under power it's like having flaps down, which force the nose up. When the ailerons rise it makes the section a more symmetrical shape. Anyhows it works remarkably well.

John.