Greetings,

In the 4*40 kit there is a guage to place a small amount of up-trim in each aileron. This is also done in the Sig Fazer.

What is the dynamic purpose of this up-trim?????

Thanks very much.

Art Gladfelter

Is the gauge your talking about in the 4*40 kit called the APG (Aileron Positioning Guide) because that was the gauge in the 4*60 kit?

Rob

I believe the ailerons on the 4*40 are full span as they are on the 4*60. If that's the case, who knows why they want you to trim the ailerons up. If the idea is to rig a little washout into the wing that won't give washout. Washout is when the root airfoil flies with more AOA than the tip airfoil's AngleOfAttack. Washout is supposed to keep the wing from stalling at the tips before stalling elsewhere. If you rig the entire wing, you've not accomplished that.

The wing on that design is a straight one. There is no sweep to the leading edge nor to the trailing edge. That rectangular planform is the wing layout that needs washout the least of any planform shape. It really doesn't need washout to fly better than any other planform. Whether or not it needs it to fly "better" is a matter of opinion.

Another reason might be to lessen the effects of the airplane's cambered wing profile. Guess if they felt they'd put too much "lift" into the wing, reflexing the ailerons was the cheapest way to solve that design problem.

But rigging ailerons on a cambered wing is also a matter of opinion. The fact is that rigging them "straight" gives no problems and rigging them up causes the wing to fly less efficiently (carries "more" drag that is of little value) and aileron deflection gives wider variation in effect (the excess drag on one side drops before normal drag starts).

When the aileron design is full span, rigging them up doesn't give washout to the wing. It's pretty much a waste of time for that purpose. And putting washout into a rectangular planform is also usually a waste of time. And you won't get it with full span ailerons anyway. And reflex profiles give kinky aileron response to some degree.

Why would the designers suggest you rig the ailerons up on that wing? Beats me.

If they felt that the airplane needed a less cambered airfoil, they should have cut the ribs that way.

If they felt the airplane was too prone to tip stall, they should have suggested you warp the wing to actually get a washout that would resist that.

They're basically asking you to fly a reflex airfoil. I got no idea why that would be of value to how the airplane handles. If it did, why didn't they simply make the wing that airfoil.

You guys got me curious now.

Anybody seen in the instructions or on that gauge why the kit designer or mfg suggests you rig the ailerons up?

BTW, when you rig an aileron on a cambered airfoil up......................

You're actually creating a different airfoil. A reflex one.

But the real fun comes when you work the ailerons to roll the airplane.

One aileron is going to go up, right. And one is going down. Let's look at the one going up.

It's already been flying around trimmed up. What it's been doing all that time is reducing the lift the wing would have been able to create. And it's been creating more drag than that wing would have created had the aileron been trimmed to give the original profile of that airfoil design. And it's been causing the wing to create less lift than it would have without that aileron trim. So the wing would have been flying at a greater AOA than "necessary". Any of that sound like a benefit? So now that aileron that's about to move up starts up. It simply does all that stuff but does more of it. On the other hand..... on the other wing...... that aileron is starting down.

The down moving aileron has been killing lift and increasing drag and AOA, but now it starts down.
When it moves, all those things start to lessen. So that side of the wing gets less draggy all of a sudden. And then when the aileron gets past "neutral" it starts to get more draggy. But wait.... Everyone expects the aileron that's going down to create more lift as it moves. Does changing what amounts to a reflex profile into a positive cambered one create more lift? You'd have to check the airfoil plots. So now the aileron finally "down" and moving further. The drag ought to now increase with deflection. Good thing since it just decreased for awhile.

Reflex profiles have pitch moments. Cambered profiles do too. Cambered ones give nose down pitching moments. Symmetrical ones have none. Reflex can have down, but often have up pitching moments. What are we going to get with this cambered airfoil that is being rigged into being a reflex airfoil? Who knows, but for sure it's going to be a maze to figure out theoretically.

BTW, in theory, practice and theory are the same. In practice, they are not.

The reason why-- to setup a "differential"- that is -- when doing a right turn -- --the left DOWN aileron really did not go as far off c/l as the right UP aileron
so there no need to add rudder to get a nice- non skidding turn.
This problem was common on older designs -full size /models
Some were so bad that adding a little right turn input--simply caused a right bank and the plane skidded along merrily
If the operator has a good understanding of geometry -or a radio which can ad differential - the plane can be setup with ailerons trailing on c/l then any turn input adds more UP than DOWN

all this is NFG for a fully areobatic model but the 4* is not in this market --

BTW, reflexed airfoils have substantially reduced max lift coefficients compared to similar non-reflexed airfoils.

Stalling speed and landing speeds are directly related to max CL. Rig the 4* ailerons up and the max CL is reduced, stall speed increased, and landing speed needs to go up.

Personally, I wouldn't rig those ailerons up.

Robflyer 82 & Darock,

Yes...the Gauge is called the APC(Aileron Positioning Guide).

Thanks for your answers.

Art Gladfelter

Actual use -on these planes - -setting the ailerons up a bit really does not hurt lift - the AOA for enough lift is very low

However - preventing th drag on down moving aileron is a noticaeable improvement - so - having done a lot of this crap - I found that simply rigging the aeilerons up a bit - for a gentle sport/aerobat with a 2412 airfoils ( oranything like that) really makes the wing act more like a fully sym section - the plane is easier to fly
for that matter- just plain ol sawing the wings off one bay on each side really improves the responses on that model - been there dun it for a friend- unless someone has added a lot of weight to the 4*, it still has plenty of nice slow flying character.
The full span ones - in a dive- can and will flutter the ailerons so badly that all aileron response ceases, till the model slows - - Fixed that for a guy one day a few years back- he thought the aileron servo was crapping out
basically all of the designs with long flexible ailerons suffered from this and the cure is just to fly more slowly -- and the up trim makes it ll a bit nicer.
It is really a nice gentle sport model when properly trimmed up and flown at a moderate pace.

.

Kewl.....

It's always good to hear from someone who knows.

If I understand what you're saying, reflexing both of them up actually give the airplane "literal" aileron differential. Good deal. There had to be a reason. In practice you get a differential aileron effect.

But why not simply rig the servo/connectorrod/horns to give differential. Seems it's easy enough to get "real" differential if that's what you want. I guess I don't understand why it would be better to get a differential effect that way, when its' simple to get it directly and keep the airfoil shape "pure".

I've been helping a buddy fly his 120 four star. He has an 80 on it. He needs a BIG airplane to be able to see the model, and needs a slower flying model as well. And I wind up getting to fly it a fair amount of time. It really shows how the design handles around the bottom of the envelope. We've recently had reason to recover the wing and in the process needed to setup the ailerons all over again. We wound up having them both rigged down and both rigged up. (obviously, at different occassions ) And with both those riggings, that big old thing flew like a pig. I got no idea how it would have flown with decent power, but I do know the design didn't seem to benefit from either rigging. Truth is, after reading your posts and knowing the quality of the info, I'd really like to fly that big thing with a 120 on it now. And I plan to suggest to him that we rig 'em up a bit and see how it flies.

Art,
That is not up trim, the APG when positioned as the directions indicate will give you the proper neutral aileron, no way you can set the neutral by the "TLAR" method. I've built the 4*40 way back when it was introduced, and my favorite plane now is my 4*60 with a Saito .65 on it, this is the only plane I have built that actually has the engine installed that's shown on the plans, just happened that way[8D], good luck with your 4*40, I'm sure you will enjoy it!
Pete

Pete...Thanks for your response.

What is the TLAR method? Is it....That Looks Alright???(Just guessing)

Actually fellows, I've been flying 4*40 for 5 or more years with APG setting on ailerons and it flies great...especially with a clipped wing.


Real reason for my original question: I just scratch built Das Ugly Stick from original design by Phil Kraft but have no information on where ailerons are to be set(or even the CG location). So......I set aileron trim on DUS using the 4*40 APG. Das Ugly Stick flies great with a few clicks of UP elevator. Not sure where the aileron neutral position is for DUS...and/or if I should possibly try to "lower" EACH aileron-say by two turns on the linkage-and thus may not need the up-trim on the elevator??? Will probably have to just experiment at field.

Thanks again...everybody.

Art G.

Good thing about trimming the aileron settings on the UglyStick is the wing is symmetrical. With most symmetrical wings, it's fairly easy to eyeball the straightback position that usually works best for them.

First priority is to see that the wing isn't warped. Then that the two ailerons are straight and both have the same deflection. Then try to see that they look to be straight back, not up or down. Then fly and sort them from how the airplane handles. They usually are almost invisible from then on with the average sport airplane being flown by the average flyer doing what he wants to do.

A tip about setting ailerons........

I get to check other people's airplanes to "see" what's wrong a lot. One thing that has repeated itself a lot is worth mentioning here.

Wings that don't have 100% span ailerons/flaps usually have fixed sections of Trailing Edge either side of the aileron. I can count on one hand the number of those airplanes I've seen in the last year where those TE pieces were correctly aligned. Heck, very often they aren't even with each other on one side more often than not, much less being even all across the entire wingspan.

But what I almost always hear every time I try to explain what works when eyeballing a wing for warps etc, is a question that repeats again and again. Someone always asks, "which of those things are you supposed to line the aileron up with" or "is it better to line the aileron up with the outside one or the inside one".

The aileron is really supposed to be positioned relative to the wing, not those TE fairings. And with the very few TE fairings I've seen that line up relative to the wing, it really is worthwhile to ignore them. The last couple of ARFs I've assembled, those things were so bad that I felt compelled to straighten at least one of them on every one of those ARFs. If for no other reason than to head off the well meaning suggestions that I didn't have my ailerons "aligned right". chuckle.....

So how do I eyeball a wing to check for warps and to rough check the aileron positioning?

You can use both eyes or one. The idea is to line your eye(s) up "straight back" from the wing and centered to the wing. Centering is easy. When you see both sides of the fuselage equally, you're straight back on that plane. Centering up and down isn't so easy.

If the wing is a symmetrical one, then before you start, look at it's alignment in the fuselage and trace along the fuselage to the rear to see where it's pointing. Start with that "point". If you're aligned up and down when looking at the rear of a symmetrical wing, you're going to see equal amounts of it above and below the trailing edge. Make that judgement by comparing the wing at the roots.

A cambered wing isn't really hard to do if you realize that it doesn't matter too much. You're not measuring the thing. You're just eyeballing, but you do need to establish in your own mind "how much shows above and how much shows below" and stick with it. Once you've got the proportions in mind, the rest is fairly easy.

Keep your eye(s) and the airplane steady and look left and right. Keep looking back straight ahead to check that you've not moved the plane or your head, and you'll start to pick up what's straight and what's not.

It helps to have the sun or lights directly behind your head but if that isn't easy to do, then it works to have light directly down on the top of the airplane. Comparing a solid shadow to a bright image isn't so hard to do because the outlines are sharp. Try to get a contrasting background and whatever the light is doing won't matter much.

Now, simply look to see where the TE of the ailerons goes compared to the TE of the wing. Then look at the TE of the wing and ignore the ailerons alltogether. It helps to adjust whatever you see wrong with the ailerons and then look again.

It's always a surprise to me how few guys have ever done this eyeball check. Or don't really know how to do it.

A couple of things have shown up sort of as a trend over the last year. It's amazing how good and straight most ARF wings are built. After looking at lots of wings from way before ARFs showed up, I gotta admit that the ARF mfg's are doing this hobby a big favor, or at least a favor to a lot of the guys in this hobby. But the other thing I've noticed is that the ARF mfg's are doing a universally lousy job of cutting hinge's into the wing/ailerons. It would seem that they almost always have misalignment somewhere. You'd think they'd use a tool or jig. Actually, you'd think they'd do some quality assurance and then fix their proplem however they chose. But they need to get better at that one detail. This one step isn't close to the quality of the rest that they do.

Darock,

Many thanks for all the information you have shared.

I'm still learning.

Art Gladfelter

Art,
Real close, "that looks about right"

Hey I have my 4*60 set up with flaperons, and even with about 20dg. of flap extension there is very little if any pitch change, but she sure floats, maybe I should try some spoileron just for grins
safe flying everyone[8D]
Pete

Thanks....Pete

Art

Camber control is a really effective way of changing the flying characteristics of an airplane. It is done all the time with pure gliders and motor gliders. For wings with semi symmetrical or flat bottom airfoils, some up reflex of the ailerons improves penetration at the expense of lift, absolutely essential if you are in sinking air and you want to get away from it. Whereas a few degrees of down flap enhances lift while in rising air aka thermals. On windy days a semi or flat airfoil will baloon annoyingly going up wind, some reflex reduces the balooning and enhances penetration at a constant altitude. Some glider guiders will continuously vary the camber during thermalling, reflexing upwind and down flap down wind, with a constant elevator setting and rudder offset to maintain circling. Neat huh? Trust me it takes some practice but it adds to the fun for some people.

ciao -rjf