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Aileron Diff

How to find the sweet spot.

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Alex Leigh21/06/2011 16:01:39
892 forum posts
56 photos
1 articles
Two questions really:
1) On my Bird-60 I set up the diff (which is about 14mmup/9mmdown) using end points rather than diff setting on the TX. No idea why, was quite tired I think! Does this actually matter? Do you lose some of the "proportion" by doing this?
2) What am I looking for here to find the sweet spot. I understand some of the logic behind diff in terms (well maybe I don't!), but with smaller wings is it more important or less? And if must be closely linked to other set up such as cofg, snap flap, running full length ailerons (using flaps etc)
I guess what I want is for lovely grippy turns across the slope. One way always seems to be better than the other. I accept most of this is my thumbs but I'm trying to work out how to focus on set up.
Maybe the answer is "you're starting from the wrong place"! I am happy with the cofg in terms of dive tests and inverted, but otherwise it's all a bit of a mystery.
Isoaritfirst21/06/2011 18:34:47
33 forum posts
Hi Alex,
1) Transmitter differential is just a predefined mix made by the manufacturer to make programming your transmitter a little easier.
If you have curves in your transmitter than that is an alternative place to make a diff, just by re shaping the curve. End points may make the throws reach their end point when the stick is at half way position so may not be a good choice. Should be easy to see if this is happening with your transmitter.
2) If you understand the logic then diff is probably not of a lot of use on a smaller model, But you may like its effect, so really its a suck it and see. Watch closely and you will see how it effect the line of the fuz when ailerons are applied.
Conditions are the biggest variable in turning nice. A small amount of cross wind will change the turn dramatically.
Alex Leigh21/06/2011 18:42:35
892 forum posts
56 photos
1 articles
Thanks Mike. Most of my theory comes from the full size and doesn't always translate. I really need to think more about my setup when I'm flying. Rather than just hooning about.
I'm going to set them to no diff at all then. And will try
1) Flying like that and watching the fuz
2) Then try with some diff dialled in
3) then try it with the diff the "wrong way" just so I can see what that looks like
4) Then try full span
At which point if my head hasn't exploded, I'll start working out the best way to use rudder as well. Although on a v-tail this also seems slightly counter-intuitive sometimes.
Isoaritfirst21/06/2011 21:25:27
33 forum posts
Hi ALex,
On a 60" I would probably settle on around 40% diff. But it is very dependent on what you want from your flying. I like my models to pull slightly around the bank if that makes any sense. Describing it another way - in a f3f style turn the tail lifts slightly pointing the nose through the turn.
Remember that the up going aileron will create less drag than an equally moving down going aileron. So when banking for a turn with no diff the higher wing creates more drag and gets pulled back creating a nose high fuz line.
Dial in more diff than the required amount to even out all the drags and the lower wing will create more drag and the nose will pull down into the turn, and the tail will sit high. I like a small amount of this to push the fus line down through the turn. But when doing straight rolls across the slope it may show as a slight barrel in the roll.
It also means that all this reduction of aileron travel will soften your responses, But most model will perform just as well with less movement than many people set in.
V tail rudders, I have found that most of mine work nicer for being restricted in their throws. adding in lots of rudder when you only have small elevator throws can start to get ugly, as the rudder inputs will also apply some degree of elevator input.
Alex Leigh21/06/2011 22:14:36
892 forum posts
56 photos
1 articles
Cheers again Mike. That's a really useful explanation. I shall experiment and report back.
Tim Mackey21/06/2011 22:49:25
20920 forum posts
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15 articles
Even I understood, after reading it twice
iawnski22/06/2011 20:22:19
1076 forum posts
28 photos
im still reading it
Alex Leigh22/06/2011 21:15:26
892 forum posts
56 photos
1 articles
Reporting back as promised. Well I had a go this evening in not great conditions, but found something close to a sweet spot around 35% diff. Although that could all change as conditions do. But it was interesting trying different diffs, definitely tell the (ahem) difference.
Also found with the diff dialled in, I now prefer to run the ailerons full length with the flaps (although only at about 30% of the movement). V-Tail rudders tho, that's for another day.. too much movement still I think.
I do love that bird tho. Born to Hoon.
I've now a question about Crow but shall start a new post, as I think there's much more to learn/research here.

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