Thrust line creates radical nose up under power on Wingo...

[kral27]

I have a modified wingo with a Mega Brushless 400, 5 Turn and a 18-10cm prop. While taking off at appx. 3/4 throttle the plane turns nose up rapidly allmost simular to an airplane configured very tail heavy. I suspect that the prop blast is deflecting the rear stabilizer acting as an alternative elevator up input. I would prefer to arrange things to neutralize this effect. I suspect that setting the thrust line to near or equal to the Wingo's datum, the plane will have better pitch stability under a broader range of power settings. The plane weight is around 950 grams.

I will post a couple of simple illustrations to clarify the situation:

[ArtSvensson]

I think there many Wingo discussions a few years ago. Seems that the boom was not very stiff and deformed in flight leading to instability. You might look into that before chasing thrust line around. Good luck!

[kral27]

The tail boom issue was resolved with an aluminum square (tube) to address that issue. I built this Wingo for days with those omni directional breezes we all have experienced and therefore has a wing loading of appx 11 oz. All tail, wing, and fuselage portions were coated with a stiff yet flexible clear cote that is a hybrid of a myriad of glues and minwax polycrylic. I think that the issue may be to much pitch speed at the factory thrust line since it's spinning a bit more agressive motor-prop combo. After completing the test and proving phazes of this plane it will be used for aerial photography.

Nevertheless discarding the conventional tractor thrust line guidelines typically in practice, I think it's time to consider a new guide line for 'trailor' thrust line recomendations.

If one were to fix he plane on a CG stand in such a way that the plane would be secure I beleive one would find that the prop blast would have a tremendous down force on the rear h-stab. So much so as to have a significant effect even at a broad range of airspeeds.

If anyone on this forum has experimented with this situation (Wingo or any other pusher set up) with a conventional cruciform tail I would appreciate any feedback, links, or anythings...

Thanks for your input.

In addition, my CG is set at appx 5mm ahead of the plywood spar support which is 5mm ahead of manufactures recomendations.

[vintage1]

In addition, my CG is set at appx 5mm ahead of the plywood spar support which is 5mm ahead of manufactures recomendations.

That is probably most of the problem. You will have up trim in to compensate, and the effect of that will cause a power stall under big power.


You can tame his one of two ways..the first is downthrust, which is a bit hard, given that the motor is round the CG anyway. The second is to move the CG back, so less up trim, and less trim change from power to glide, is required.

Or mix down with throttle..if you can ..

Or set the trims down, so that full power gives a rapid climb, and you need to hold up elevator for the glide.

[JetPlaneFlyer]

Krel27....I think you are on the right lines with your proposed solution. Downwash from the prop acting on the tail surface is sure to cause a nose up pitching tendancy. If you allign the thrust axis closer to the fuselage longitudinal axis then this downwash effect should be able to be minimised or removed altogether.

Vintage have a point about the forward CG location however i dont think a 5mm forward CG will really explain the violent nose up pitching you describe. Also if this was the cause you would tend to get nose up pitching as a result of increased speed, not the instant you snapped open the throttle.

I'd be pretty confident that your proposed thrust line change will sort it out.

Steve

[kral27]

i'll try and set the thrust line closer to the datum. This will take a little time since I'll have to remove and replace the engine mount which is just an Astro fiberglass speed 400. These little mounts are outstanding for both in and out-runner electric motors. Mounting can be done on either side of the 'firewall'.

The motor and prop combo makes it a little difficult to do the requiste trim and elevator control inputs especially when you are flying it in a gulf coarse surrounded by very tall trees.

Perhaps this is not the correct thread to ask if it is possible to use a 20x10 (8x4 inches) with the MM16155 Mega Brushless 400, 5 Turn + JESAP18 Jeti Advance PLUS 18 Amp and with a KOKAM 3200 LIPO 3 cell. I have some 2 cells as well but are not heavy enough for the balance. It ould be great if the speed control just limits it to 18 amps and stays within operating temps.

[GaryO]

Stock Wingo's that I have seen are very speed sensitive due to the large incidence difference between the wing and tail. It's intended to be a beginners plane and is trimmed to be very stable, but that makes it speed sensitive.

Since you plane is heavier, and using a more powerful motor, is your flying speed also higher? If so, I'd tend to think that the plane first needs to be trimmed with less incidence. A way to check this is to do what the glider folks call a dive test. Check the hlg forum to find out how this is done. You would want to do this with the motor off.

I'd mix throttle with down elevator, but maybe your xmtr wont do that?