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CoG problem ?

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fly boy313/06/2018 16:52:53
3467 forum posts
18 photos

Hi all, my OD model (similar to Acrowot) flies well and I am pleased with its performance. One little niggle is that it seems I need a lot of elevator in turns compared to my other models. Could this be a CoG problem ? Thanks

Denis Watkins13/06/2018 17:08:46
3671 forum posts
173 photos

Usually, it is too little aileron FB

Are yours t design max?

john stones 113/06/2018 17:36:44
10381 forum posts
1475 photos

Could be that simple, or other reasons, picture of it would help. wink

Could also be that it just needs more elevator, and nothings wrong.

Edited By john stones 1 on 13/06/2018 17:42:47

Percy Verance13/06/2018 17:58:43
8069 forum posts
155 photos

It needn't necessarily be anything *wrong* fly boy. It may just be peculiar to that particular model, in the same way that different cars need more steering input than others etc...

Try moving the C of G back a touch to see if it makes any difference. If that upsets other aspects of the handling - such as the landing approach - then move it back to it's previous position and simply increase the elevator movement a touch.

Biggles' Elder Brother - Moderator13/06/2018 23:13:16
15748 forum posts
1460 photos

If the aircraft generally flies well, is reasonably responsive and flairs OK on landing, then its very unlikely to be a CoG issue.

As Percy says aeroplanes can be quite different about this. Just as one or example among many possible factors one effect at play is the length of the tail moment. If the aircraft has a very long tail then the the elevator has a lot of leverage so small movements do the business. But if on the other hand the tail is very short the elevator has little lever length to work on and so larger elevator forces (and hence movements) are needed.

I'd follow the age old engineering wisdom of "if it ain't broke, don't fix it" in this case!


Peter Jenkins14/06/2018 00:05:39
1203 forum posts
132 photos

FB3, when you fly the aircraft inverted do you need a lot of down elevator to keep it flying level? If yes, then you have a forward CG and could usefully inch it rearwards until you feel the aircraft is flying better. You will know when you have gone a tad too far when you don't need any down elevator to keep level when inverted or even to have to use up elevator to prevent the nose from rising. The aircraft will still fly fine but it just won't feel right at this point. Main thing is to only move the CG by a small amount each time.

fly boy314/06/2018 03:03:02
3467 forum posts
18 photos

Thanks for all the informative gen on my query. As BEB says,if happy leave alone lol.I think I will try the inverted test though as suggested byPeter and see where I go from there. Thank you all. Cheers

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