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Dlg elevator trim


Mark Evans
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That’s how I’ve set up my wing, I’m just using speed (and zoom) 2mm up, cruise at zero and thermal at 3mm down. 
 

On the field now, bit windy, phone says 11mph and I’m flying empty at 240g but plane seems stable enough so I think my settings and cg are good for me. 
 

Finding all the sink, amazing how the plane just drops out the air, most flights are under a minute, think my best today just nudged 2 minutes. I’m not the best at flying in this kinda wind. 

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terryspence

The mention of the KK Dophin brought memories flooding back as it was my first glider too. Likewise the Caprice flyaway reminded me of my flyaway experience.  The Wharfedale MFC at the time was a predominantly a control line club decided to hold an in club one design glider comp and chose the Mercury Gnome kit. I couldn't make the day of the comp so later took the model to Baildon Moor to test fly it. A very gentle tow on only 20ft of line saw it head of down wind over a low ridge and out of site never to be seen again!  I would add to Mike F's comment about D.T.- make sure there is enough rudder to make circle.
Having been a long time Open and 100S competitor in the past I have found all the information really interesting and more scientific than I ever got to.
I strongly agree the model should be easy to control with a reasonable amount of stability so you can look around at what else is happening. Also any control movement will be causing drag so fighting instability is with extra controls is not a good thing.
Not Going Out - mine is repairing a KK Ajax I built for my son many years ago.
 

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  • 2 weeks later...

Update on my trim issues. Either I had too much up elevator trim before or too rear of a cg but I recently set my plane back up. With the elevator trimmed flat and a coin in the nose it now flies level with zero trim needed and feels like a completely different model. No more pitching up into wind, stable and easy to fly. 
 

After seeing Mike F say he pushed his cg forward on his snipe and felt his turns were better is what go me thinking that maybe I needed to go more forward myself. Well it did the trick, surprised how different it feels. Very happy with it now. 

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  • 4 weeks later...

With the way things are going I can’t see there being a meet up at the BMFA Center so if any of you experts wanna come to Redditch and fly my plane to sort it out for me I’d cover your fuel cost and extra lol.

Im mode 2 and left handed, I’ll throw, you sort the plane out, then hand back the trannie when it feels great lol. 
 

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isoaritfirst

I always think a good starting point is to set the surfaces to the foil design, then adjust how it flies with nose weight.

small amounts of up or down after that are useful in flight modes to allow better thermal or speed options. 

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Plane is set up as per the recommendation. Flies good, but I feel it’s lacking something, I’d like it to feel crisper and take less up elevator to keep the nose up with a roll input. 

I have now put in some snapflap which I think helps a little. Not sure if it’s the right solution but I feel it’s a little step forward. 

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You will always need to hold up elevator in a turn - the tighter the turn, the more up.  Or do you mean something else?

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I use elevator to keep nose from dropping, not sure u will get to holy grail of no nose drop in a turn and still find the model enjoyable to fly.   The elevator is there for a reason 😀 use it.

Fly model level towards you and roll left right. How badly does nose pitch down?  Play around with differential and retest.

Play around with differing amounts of rudder in your turns to see how it affects pitch.  I don't mix A/R.

Someone else's trim might not be right for you, but yes they could identify any major mistakes/issues and observe the way you fly on the sticks.

Shame you never brought and flew your model at previous meet ups.

I remember first time Mike S 'observed' me on the sticks.  He was pretty critical of my elevator usage so perhaps I'm not the best person to respond 🤣. Hopefully I'm a bit better now.

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Without the snapflap I feel like I’m pulling back on the stick quite a bit even though I’m running quite a bit of elevator travel, easily 10mm each way. 
 

Doing the aileron rock test I’ve never been able to see any difference, I’m just running even throws on ailerons, no aileron to rudder mix. 

My plane might be fine then, I guess if I crisp up my elevator response too much I’ll just end up over controlling. 

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isoaritfirst

It sounds like you are just flying too slow. 
perhaps you have the model trimmed to try to climb. 
you should remember a glider flies downwards all of the time, except when zooming up with energy from a downward run. 
of course downward to a glider Is relative to the air not the ground. 
going up relative to the ground requires lifting air not up trim. 
relax and try flying faster, look for good air and don’t try to force the model up 
 

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I think my trim is ok now, i trim so my fuse is slightly nose down in level flight. I feel like my plane is flying at a good speed. 

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Until only the other week I used none, I hated the feel of expo but I have 30% on there now cause I went with more throw and then used some expo to soften it around Center. For me I felt the recommenced throws for the Auri left it feeling a bit soft, I wanted the crisp feeling I felt the NXT had so increased the throws, I think I have about 10mm each way on elevator and 15mm on ailerons. 

But here is something I noticed, yesterday I climbed out in some really strong lift and then dived down from height and back upwind to myself. I then went to pull a loop but even at the speed I was, I almost stalled out at the top of the loop. I had full up elevator held and expected a nice tightish loop, I didn’t have enough speed for another. I have 2mm snap flap in all modes and at that moment I was in my speed mode of 2mm reflex. It really didn’t seem right that it struggled at the top of the first loop and wouldn’t do another. The little lightweight elf would have gone on until it hit the ground. 
 

Again, while my plane feels ok I still think it’s missing something to make it even better but I can’t put my finger on what it is yet. Even though I try different settings, I only make 1 change at a time and ask myself better or worse. In the above posts I said I thought snapflap helped keep the nose up but the more I think about it the more I think it makes the plane feel more buoyant in a turn rather than keep the nose up. The snapflap might end up slowing my plane down a lot, even at small values?
 

 

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DOH!

I just checked my plane and had a lot less elevator throw than I thought, I must of had about 6mm each way, and on top of that I had 50% expo dialled in. No wonder I was using a lot of stick travel. 

I definitely have 10mm each way now and 30% expo. 

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  • 1 month later...

Last question, if running a more forward cg, can you stop the porpoising? 

I trim for a level hand toss into wind, when flying and then going down wind, it's a bit nose down and loosing a far bit of height running downwind the length of my field. Can I stop this or do I just need to be launching higher/finding the lift faster? 

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Thanks Mike, ignore my post, I’m getting too obsessed with trying to find a good set up. Time to put the planes away now and get the mountain bikes back out. 

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