Tony Read Posted August 5, 2014 Share Posted August 5, 2014 Like many people who are flying the Hobbyking Vampire, I get the pronounced change in trim when the throttle is cut. It needs a lot of down elevator to maintain a good attitude at low speed. There must be some sort of issue with the thrust angles. For a quick fix I thought about mixing in some down elevator to the throttle, say 20%. The problem is that this needs to be at no/low speed, reducing as the throttle is advanced. Not sure how to do this. any pointers would be gratefully received. Quote Link to comment Share on other sites More sharing options...
chris Bond - Bondaero Posted August 5, 2014 Share Posted August 5, 2014 What radio are you using ? On the JR you can achieve this by varying the offset in the mixer. Will elaborate if you have JR Quote Link to comment Share on other sites More sharing options...
Tony Read Posted August 5, 2014 Author Share Posted August 5, 2014 Doh! Forgot to say, its a DX8. Quote Link to comment Share on other sites More sharing options...
Pete B Posted August 5, 2014 Share Posted August 5, 2014 It's quite easy, Tony. Go to the Mix menu, select Mix 1, make thr the primary, ele the secondary - and watch the elevator to see which way it trims when you add a value. It should be a linear progression. Any problems, just ask.... Pete Quote Link to comment Share on other sites More sharing options...
Tony Read 2 Posted August 6, 2014 Share Posted August 6, 2014 The problem that I'm struggling with is that I want the required elevator deflection (say 20% down) at zero throttle and none at higher throttle settings. As Chris says, it probably has something to do with 'offset' but I've played around with various settings and have got nowhere. Help! Quote Link to comment Share on other sites More sharing options...
Tony Read 2 Posted August 7, 2014 Share Posted August 7, 2014 I finally sussed it. Putting a negative value in the lower of the rate 'boxes' gives me down elevator at zero throttle. The only problem was that I forgot that this would eat into my up elevator, so I ran out of elevator on landing. Opps! Increased the elevator throw and now all is well. Quote Link to comment Share on other sites More sharing options...
Chris Jones 7 Posted August 7, 2014 Share Posted August 7, 2014 Hey Tony, With mine I noticed that the booms were really flexing so I inserted a strip of flat carbon to stiffen them up. Result was that most of the ballooning went away! I think the horizontal stabiliser was changing its angle of attack with throttle and when throttled back it would return to position. Either way, it's a cheap and simple fix. Chris Quote Link to comment Share on other sites More sharing options...
Trevor Crook Posted August 8, 2014 Share Posted August 8, 2014 I think the effect is to do with the "cheat" ducts underneath sucking the nose down at full throttle. I only notice it as a transient effect on mine, so I've dialed in a 2s "servo slow" on the throttle on my Dx8. Spools up and down more gradually, so de-stresses everything, but is still quick enough to respond when I need it. Quote Link to comment Share on other sites More sharing options...
Tony Read 2 Posted August 8, 2014 Share Posted August 8, 2014 Its not the booms on mine as they got the CF treatment when I put it together. I also spent a lot of time aligning everything so its as close as possible to how it should be. I still think its a thrust line issue. A thrust tube to reduce the outlet size and adjust the angle could be used, but to be honest I like the way it flies now, so probably won't bother. It does like hoovering the grass up though! Other vacuum cleaners are available of course. Quote Link to comment Share on other sites More sharing options...
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