I have a problem that I hope someone can give me some insight. I built an electric Skimmer sailplane kit. I used a Mega 400 5-pole motor, Castle ESC, LiPo battery. I have attempted to launch the plane twice resulting crashes due to the inability to turn left. The rudder has plenty of thow, the motor has about 2 degrees of thrust angle and slightly down. The flight this afternoon started flat and controled until I needed to stick left. I have not a hint of movement of the airgborne plane to the left. Somehow I landed out of control but no damage. The wing is built straight. Can anyone give me thoughts as to where to look for the problem.

I understand this sailplane has no ailerons; hence, any turn is by rudder and dihedral.
Does it show the same non-reaction with the motor on and off?
Has the wing the designed dihedral?
Is the tail surfaces perpendicular and parallel to the wing?

The wing has the dihedral intended and the tail is placed as it should be. I have not tried launchiung without the motor running.

Do you have the rudder servo controlled by the Rudder stick or the Aileron stick? I fly power and gliders and have sometimes about broke the Aileron stick off, forgetting I have to use the Rudder to make the glider turn. Also, be sure you have rudder movement with the motor running pretty fast while holding the glider.

And you definetly placed the balance point where it's called for?

And did you do a "top view" alignment of the wing to the fuselage and fin to the fuselage centerline? By this I mean you lay a centerline lightly along the top of the fuselage. Then you lay the wing on and check that it's equal span on each side of the center line to within 1/8 inch. Then you measure diagonally from the tips to the centerline back by the fin. These diagonals must be the same to within better than 1/8 inch. Within 1/32 inch is what I aim for when I'm doing mine. Then you want to ensure the fin is glued on so that it's exactly in line with the center line. Once you've set the wing on evenly and completley straight you should mark the position so it's easily repeatable or even key it someway. This is a lot more fussing than just putting the wings on and sort of looking at it and saying "close enough".

ALso just for giggles what size and how many rubber bands are you using to hold the wing on? A common beginner's mistake is to attach the wing with far too few rubber bands.

If all these things we're asking about seem to be set right then it's likely that you're not launching it straight ahead in a smooth javelin like push. If you try to toss it haphazardly like a baseball it'll be rotating in your grip strongly and that'll react instantly upon release. A glider of this sort doesn't need much of a throw. Just a firm but gentle push straight ahead.

Yes to all the items mentioned above. The plane was launched smoothly and straight and was on its way until course correction required left rudder (which is set up to the alileron). The plane responded in all axis except turning left. I used six rubber bands which would pull this light balsa apart before it flexed. I hate to make this one a hanger queen because from what I can see it should fly. I quess I could adjust sub-trim to include a little left and see if this give me any control. I will monitor this page if anymore information is offered.

Could you describe the type of control-connection between the rudder servo and the rudder? E.g. pushrod, cable-in-tube,...? If you hold the rudder and operate the rudder-servo, does the control-connectin flex?

The pushrods are wood and do not flex. I am going to put about a degree of left thrust in the motor and see what happens.

I do not believe in mysteries.

In this type of models, the rudder deflection creates a side force that makes the fuselage yaw by reaction against the flow of air.
Then, one wing presents a higher AOA to that flow than the other wing, due to dihedral, lifting more and banking the whole model.
Then, the circular motion starts, and lasts as much as the bank.

If the model cannot turn to the left, is because the deflection of the rudder does not create the lateral force necessary to yaw the fuselage.
If that is true, and all the angles and lateral balance are symmetrical, then a lateral force in the opposite direction must exist.
If that opposite force has nothing to do with rudder deflection, then it must yaw the fuse to the right when rudder is neutral, which is not happening, according to the description.

Fly the model away from you and watch for fuse yaw for left, neutral and right rudder deflections.
Also check rudder alignment with vertical tail, after trimming for hands free straight flight.
Please report your findings; this is very interesting.

This is probably one of those things where you have something that is wrong or that was done wrong where if it was in any of our hands we'd just see it straight away and be able to tell you what to fix. But when you're dealing over the 'net it's impossible to do more than accept what you're told.

Just for the heck of it use the RC system to deflect the rudder over and then try to lightly push it back with a finger. Wood or not sometimes odd things can happen that result in pushrods bowing under load. You won't need much. THe air forces on a rudder that size are not more than a few ounces.

Um... what size diameter of prop is on the motor? I ask this because I had a model that used a prop that was a sizable % of the wingspan and the model was, as I recall, reluctant as heck to turn to the left but would almost snap roll to the right with a hint of control. A friend noticed the same thing but not quite to such a strong degree with another model that had a fairly large prop for the size of model. To confirm this you'll want to test glide with power off out over the slope of a gentle hill so the glide is extended enough to test the rudder response in both directions before landing. If this test glide is successful at least you'll know it's motor and prop related. From there you can add some thrust line compensation secure that you're not hiding some other issue. Of if the thrust line adjustments still leave you with some funky handling issues go the safe route and swap out the motor for one that will work well with a little smaller propellor.