Elipsoid Evolution

[FairviewRCflier]

Repairs... So I couldn't stop from sliding on the ground when coming in for a landing fast enough and met a soccer field post. Both wings got damaged. I have fixed them but here are some pictures.

[Len]

Ahwww. Those damn non-movable objects. That plane seems like a rocket, huh. Sorry you had damage, but glad you got it repaired quickly.

len

[FairviewRCflier]

So the spoilers (Ailerons acting as flaps upward) worked pretty well! Which is good because I didn't want to actually cut spoilers into the wing.

[Len]

No, I agree. It would be easier to build a different airplane with spoilers vs try to modify that one. I'm glad it helped.
Keep moving forward.

[dgliderguy]

FairviewRCFlyer,

UP ailerons is what we call "spoileron". It is an effective way to get a glider down on the ground when you want to avoid ground-effect float. It does not, however, slow the glider down much. Flaps are much better at slowing a glider, with high drag and a higher lift coefficient. Spoilers (hinged or pop-up) do a fairly good job of slowing a glider down, by increasing the drag coefficient, but do not lower stall speed like flaps do. Spoileron, on the other hand, will dump the glider downward, but will not slow the glider or increase the drag much. That is to say, your touchdown speed and rollout distance will be nearly the same as without spoileron. Something to keep in mind.

So,

Flaps = high drag, and increased lift coefficient = slower approach speed, lower stall speed, marked deceleration when deployed, steep glide path with nose-down attitude, short landing rollout
Spoilers = decreased lift coefficient, higher drag coefficient = somewhat slower approach speed, not much deceleration when deployed, steeper glide path, shorter rollout than without
Spoileron = decreased lift coefficient, drag coefficient minimally increased = no noticeable change in airspeed when deployed, steep glide path with level attitude, no reduction in touchdown speed or rollout distance.

Keep in mind also that there will be a pitch trim change with spoileron. In most cases, when you lower flaps, the nose wants to rise and must be countered with down elevator trim (mixing is a big help). When you deploy spoileron, the nose will usually drop, and must be countered with some up elevator trim. I have had some sailplanes where the nose rises with spoileron-- just depends on the effect it has on pitch moment. This is why it is always good practice to experiment with program-mixing trim settings at altitude, and not while on short approach.

Spoileron is a great way to get some approach control out of a glider that does not have flaps or spoilers. Flaperon, on the other hand (lowering the ailerons together) has some really bad adverse effects, such as pronounced adverse yaw (to the point of craziness, I've seen it!), and a high, high propensity to tip stall and roll off to one side (definitely bad).

Hope this helps,

Don.

[Len]

Don,
Excellent information. Thanks for taking the time to lay it all out. Certainly flaps would be the best solution for this glider, and it would seem to be a much easier modification too.

Appreciate the input

len

[stihac]

Great info Don! Thank you.

Petr

[FairviewRCflier]

This is all fantastic information... What I have found is that my ailerons programmed as spoilerons work pretty well. Like mentioned, they do not slow the plane down drastically however, it interrupts the floatiness and allows me to have shorter and more controlled landings