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Rolling a model twice

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John Privett28/09/2015 23:02:53
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5970 forum posts
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Posted by ben goodfellow 1 on 28/09/2015 22:30:59:

nobody use else use rudder when rolling ?

I do, and a few others have mentioned it already in the thread.

It's not required for the test, but that's not to say you can't do it. But, I s'pose, if you try with rudder and don't get it right then the results could be worse than not bothering with it at all. Practice, I'd say is the key. The more practice then the better the timing of elevator and rudder inputs should become. And why stop at just two rolls? Fly several in a row (that gets you more practice!) or even entire rolling circuits. Maybe that's getting a little carried away though... smile o

Peter Jenkins28/09/2015 23:54:19
1281 forum posts
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If you read the guidance notes to examiners and candidates on the B, which you would be foolish not to, (downloads tab on the BMFA website), regarding the 2 rolls it states:

These should be performed from standard height and line and must be continuous rolls with no straight flight between them. The model should be half way through the two rolls when it passes in front of the pilot although you may allow a little leeway here.

There should be no serious loss of height or direction during the manoeuvre although slight barrelling of the rolls is permissible. The speed of the rolls should be such that the pilot has to make noticeable elevator inputs to maintain the model's height.

'Twinkle rolls' that are so fast that no visible elevator input is required are NOT acceptable, you have to be sure that the pilot is using the elevator. Slow rolls which require elevator and rudder input are acceptable if the pilot can perform them but are NOT a requirement.

Don't forget to note which way the model rolls.

Max5029/09/2015 07:35:46
178 forum posts
8 photos

With my cougar , I fly straight, then roll, and just before inverted apply down elevator. This pushes it up slightly when it comes inverted. Continue the roll, and just before upright apply up elevator. Which again pushes the plane up. From there keep the roll going and do exactly the same thing again.

Start practicing with one roll, and as others said ,with a little up, before you commence the roll, then once you,ve got the timing right , continue with two.

It,s just getting the elevator movement right at the right time in the roll, or you will just push the plane out off line.

Edited By Max50 on 29/09/2015 07:59:27

John Muir29/09/2015 10:02:08
372 forum posts
1 photos

I forgot to mention centre of gravity.

For smooth consecutive rolls it's important not to have the CG too far forward. Turn the plane inverted in flight and if you need a load of down elevator to keep it level shift the cg back a bit. Check again and keep doing it until you only need very gentle pressure on the stick to fly inverted. Be prepared to reduce your elevator throw slightly as the model will become more responsive in pitch. Once this is done you'll find it much easier to do consecutive rolls.

I think lots of people fly with the cg too far forward for 'safety' and it turns a lot of planes into unresponsive dogs. Maybe not in this particular case of course, but worth checking.

MattyB29/09/2015 10:39:58
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1957 forum posts
30 photos
Posted by John Muir on 29/09/2015 10:02:08:

I forgot to mention centre of gravity.

For smooth consecutive rolls it's important not to have the CG too far forward. Turn the plane inverted in flight and if you need a load of down elevator to keep it level shift the cg back a bit. Check again and keep doing it until you only need very gentle pressure on the stick to fly inverted. Be prepared to reduce your elevator throw slightly as the model will become more responsive in pitch. Once this is done you'll find it much easier to do consecutive rolls.

I think lots of people fly with the cg too far forward for 'safety' and it turns a lot of planes into unresponsive dogs. Maybe not in this particular case of course, but worth checking.

Completely agree. As someone who grew up as a glider guider I always CG all of my models (powered or unpowered) for a neutral "carry straight on" response, and as a result I've never needed to input any up during the upright phase of consecutive rolls or rolling circles. However when I go to the power club I frequently see (and am occasionally asked to test fly) models that appear to have the CG set about 1/4" in front of the spinner! wink 2

Unsurprisingly they tend to exhibit some less than desirable handling characteristics, especially when the power is chopped in level flight or during rolling manoeuvres. Get that CG back periodically over a series of flights and check it with the dive test! (the below is for a glider, but it works fine on a powered model at lowish throttle settings):

Edited By MattyB on 29/09/2015 10:42:10

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