Rolling a model twice

[Dave Bond 2]

Hello all,

For the B certificate I see the requirement for rolling the model twice in both directions without pause in the middle.

I am flying a Cougar 2000 and though I appreciate that the B certificate is a measure of skill. I am finding rolling twice maintaining altitude much harder than I feel it should be. I see other people flying models and do not seem to be fighting their model half as much.

I can fly in level flight and inverted with very minimal correction using elevator. When trying to roll I always seem to be loosing altitude at the point of entry into the second roll. The cougar has a very thin sectioned fuselage, so at 90 deg I wonder if as there is no lift from the wings and minimal resistance from the fus I am loosing altitude at the four times the model is in this attitude.

So I am wondering what is the trick in getting this model to preform the roll nicely.

[will -0]

Usually it's a dab of down elevator as you pass through inverted.

Cheers

[Jon Laughton]

I originally had the same issue but to build confidence and control there is a cheat, albeit one recommended by the RC Flight school in the USA: a small dab of up elevator just before the rolls will help and if done correctly is hardly noticeable - also maximising the roll rate (i.e. aileron defection) to the fastest rate where you are comfortable will help but if this results the models rolling in a 'blur' it will not be considered acceptable by the examiners....so experiment if you can.

And good luck!

Edited By Jon Laughton on 28/09/2015 12:16:52

[Andy Green]

What I would suggest is have a low rate set up, and when you are about to do the 2 rolls, switch to the low rate.

This rate should allow the model to roll suitably slowly with the stick hard over, then all you have to worry about is the timing of the dabs of down elevator.

A

[iqon]

Practice doing slower rolls

[Dave Bran]

I think with that model you have as you suggest the issue with the small area of the Fus when on wing tip, and to correct that you'd need to dab correcting rudder just like dabbing corrective elevator when inverted. The issue with the Cougar is that it's rudder is heavily cross linked to elevator, which will require adept stick handling.

Have you experimented with the effect of roll direction?

Bottom Line............The Cougar is a Fun Fly machine, designed to be thrown around, not do smooth aeros in the very specific "B" cert style.

As the country yokel said when asked what the best way was to get to Ashover, "if I were going there I wouldn't start from 'ere"...............................

(I own one)

[Martin McIntosh]

Don`t expect a model to maintain height without using a little down elevator when inverted. The rules state that the use of elevator is demonstrated during the manoeuvre. Practice this doing three consecutive rolls, then two should be easy. Set your roll rate to three in five seconds. Anything quicker is really not acceptable but you may do these as slow as you wish.

[ken anderson.]

hello Dave...don't have too much movement on the controls ail round.....and don't fly too fast.......and a dab of down in when the model is inverted....i have a C2000...and it will roll from one end of the sky to other....bit of practice/standard settings -you will be ok.

ken anderson...ne...1 rolling dept.

[john stones 1 - Moderator]

Models fine for a B test, it's requires same as A test (safe and in control) but to a higher standard, took mine with a clipped wing cub. Sounds like you're not releasing dab of down correctly Dave or you're flying too slowly and it's killing airspeed with first roll. If you can do one roll you can do a dozen, it's just timing the dabs

John

[Dave Bond 2]

Thanks all, I will give it a go. There are some very good points here.

[Mowerman]

As will-O suggests, a dab of down elevator as the model pass through inverted. I practiced this on my sim until I was happy then used it on the real thing success.

[Former Member]

[This posting has been removed]

[Biggles' Elder Brother - Moderator]

John S is right, in essence! If you can do one roll you can do a dozen. But behind that statement lies a bit of an issue! When you do your first roll are you in reality exiting it just a little nose-down? You see in one roll that doesn't matter so much - you can get away with it. But when doing two rolls, one immediately following the other, its a big problem, because now you are entering the second roll slightly nose down and its really all going to go to hell in a hand cart from there on in!

I think the secret (if there is one ) to doing a good double roll is to nail the first one spot on. Get that right and you enter the second roll in level flight - get it even slightly wrong and you have your work cut out to hold it all together.

So, what I would suggest is go back to practicing single rolls in both directions for a flight or two. Concentrate on being sure that you exit the roll absolutely level - don't accept even the slightest nose-down exit. As has been said the well timed "dab of down" when inverted is the key here.

Then add the second roll. Because you are now entering the second roll level you should find it easier. If still having problems consider a tiny dab of up elevator when the model is level bewteen the rolls so you actually enter the second roll very very slightly nose-up.

If the timing of the dabs is causing you problems it a very good idea to practice on the sim - but in slow time - say 50% to start with and gradually increase to 100% (real time).

BEB

[John Muir]

Lots of good advice there.

I'd second cutting the aileron movement right down so that the model rolls at the rate you want with the stick full over. You can then concentrate on getting the up/down inputs right without affecting the roll rate, especially if you're flying mode 2. On a fun-fly model the ailerons are almost certainly massively over-sensitive for smooth flying. I'd also go with a small dab of 'up' on entry, a slightly larger dab of 'down' when inverted, then another dab of 'up' for the second roll and so on for as many rolls as you want.

With a model of this sort I'd stay away from the rudder although, technically, using opposite rudder as the model passes through knife edge is the way to get a nice smooth roll. If the rudder induces a roll as a secondary effect though it won't help. You really want to be using the elevator to lift the nose after each turn through knife edge when it will inevitably drop. For a while the rolls will look 'lumpy' but with practice your timing will improve and it will all start to look smooth.

[will -0]

I could be wrong here, but I don't think the b test is meant to be a pattern competition, so use of rudder during the roll to produce a perfectly axial one is not expected, just the aforementioned elevator correction to prevent a dive developing.

[John Muir]

I only mentioned rudder in response to the OP's first post regarding the nose dropping when the model's on it's side. Top rudder would be the ideal way to compensate for that but it won't be any help if the plane has roll coupling to the rudder, which his funfly almost certainly will. And as I said, I wouldn't use the rudder, I'd stick to elevator in an 'up,down.up down' sequence, the point being that you need to lift the nose after every knife edge part of the roll, not just when the plane is inverted. If you only use 'down' when the plane's inverted you'll need to use almost twice as much input and things really do start to look lumpy then.

[Willyuk]

Hi Dave,

I spent this year practising for the b test and i too found the two rolls difficult. I would recommend reading the thread on aerobatics by peter jenkins( just search for aerobatics and look for " ever thought of getting into......" ) it is really usefull. I too set my transmitter up to have a slow roll rate, i practised with a rate of 6 to 8 seconds to complete the two rolls. That is far slower than called for but does make one work at it! Then of course it has to be centeted. I left that until i had the rolls sorted, then adjusted to get the centre correct. Then adjusted again for wind. As said above the test calls for an obvious use of down elevator when inverted. A small amount of up before commencing the roll is acceptable i believe. MOST IMPORTANT the rolls are performed slowly but the aircraft is NOT flying slowly. I found i had to add speed prior to starting to roll, this stops the plane flopping about. Not too fast but above normal cruise i would say.

Good luck!

[Tim Hooper]

Initially I'd split the procedure into three separate parts;

1. Roll

2. Inverted

3. Roll

Practice this, gradually decreasing the inverted phase until it all merges into one smooth progression.

tim

[ben goodfellow 1]

nobody use else use rudder when rolling ?

[Stuphedd]

the two examiners I had said they would like to see the inputs during the rolls , and afterwards they said try it again and this time DONT make them so obvious.

I spent many months practicing and fine tuning the aircraft so it needed a minimum correction input from the pilot, like the "normal screw" when finishing the "bunt "

it was a pattern type .

cheers

[John Privett]

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...

[Peter Jenkins]

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.

[Max50]

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 Muir]

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.

[MattyB]

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!

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