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Old May 23, 2015, 07:26 AM
imrm is offline
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LET Ventus with SLS Compensation Question.

I have two questions regarding the need for elevator compensation associated with the SLS system operation of this glider:
1. At this time the glider is properly balanced with the SLS in the down (stored) position. As expected, the CG moves a significant amount forward when the SLS is raised. Is it necessary to program in up elevator compensation when the SLS is raised? Or is the effect of raising and lowering the SLS insignificant on flight performance?
2. Is it necessary to program in either up or down elevator compensation on throttle up? Is there a tendency for the model to nose over under power?
Input from anyone who has flown this model ( or similar class of model) would be most appreciated.
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Old May 26, 2015, 10:26 AM
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@ 1: You will have to find out by trial and error if the C.G. shift (motor OFF!!!) will have a significant effect for the flight performance, however this is of minor importance as you won`t glide around with the SLS extended and motor off.

Much more important is your question 2:
With the motor ON, the long lever of the SLS will produce a strong nose-down effect which you might want to compensate for with elevator trim. While mounting your SLS in the fuselage, take care to set the motor axis such that the prop blast is directed directly towards the elevator (the angle with reference to the fuselage axis is not relevant - against common believe ... !). However, as the nose down effect will start faster than the counter effect of the elevator and the up trim (after a brisk motor start) be prepared at the elevator control. A slow motor run up will help.

If possible, also add an aero tow hook and make you first flight on aero tow and try the SLS well up in the air ...

Happy landings
Herbert
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Old May 26, 2015, 03:51 PM
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Ventus Elevator Compensation Question

Thank you Herbert for posting your reply, your comments will be helpful. This is a friends Ventus and we expect to fly it within a couple of weeks. i did the radio programming for him and he requested that I post the question, looking to get some guidance. i will let you know how it goes. Marty
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Old Yesterday, 07:46 AM
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Hi,

I have two throttle- elevator mixes on all my up 'n' go SLS gliders (5 now), from foamy DG1000 and Arcus to my glass jobs, DG1001M, DG808, ASH 25, on a three position switch, up position is no mix, middle position is approx 5% up elevator, and the lower position is approx 10% up elevator, with a 1/2 second delay on the mixes. Thus you switch in the most appropriate on your climb-outs, it can be difficult sometimes to get the right up elavator freehand. I set these mixes as seperate modes with the trims as being seperate not global as well, therefore you can trim more up on the power climb-out in positions 2 and three, (remebering to go back position 1 after your climb) you can then adjust the mix on the ground to take into account your fine adjustments from in the air.

Another point is to have the pylon not vertical to the gliders horizontal centreline, between 5 to 15 degrees aft is about the right angle, have a look most full size up 'n' go gliders they all have a lean back on the pylon to counteract pitching forward when under power.

Hope this helps.

Antonia
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Old Yesterday, 03:20 PM
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Hi Antonia
Thank you for your suggestions, I will pass them onto my buddy for his consideration. I like the idea of setting up non-common trim on the three position switch for the elevator compensation.

Regards - Marty
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