Hi Guys
How do you measure the correct throws on a control surface.Should I line up a ruler on the top/bottom of the surface and check deflection from there or should it be from the center of surface?I've been flying electrics a couple of years but this is my first glow plane and the surface is already so thick my guess is measure it from the top/bottom not the middle.I'm setting the hi/lo rates on a sig 4*60.

thanks for the help
steve

cloudhopper,

Its a little difficult to explain without a picture (hopefully minnflyer will provide one of his) But you can buy a deflection gauge or use a ruler. Set the surface to be centered by eye first then Stand a ruler up next to it the deflection is measured from the outside edge of the surface. How far up, down or left, right it moves from the centered position is the deflection. Agian in this caase a picture is worth 1000 words hope it helps more then confuses

After I set my control surfaces to neutral with a ruler on the chord length square to the bottom of the wing, I took a large enough protractor, trimmed away the center support and made sure I had the right amount of travel. (see pic)

You'll get multiple ideas here, all great. Even if you use a standard straight edge ruler, you’ll get a rough idea on the amount of travel, albeit it being on a vertical measure.

I used a 6” protractor on my 4*60. Food for thought.

I was just going to amplify on what Kevlar started. Measuring throws with a ruler is quite precise. I know most of the manuals for beginner planes list throws this way, but you should get in the habit of using degrees of throw, not inches of throw.

While not impossible, it is hard to accurately measure throw in inches (linear measurement), not to mention the measurement is meaningless. The degree measuring tools (both for sale and ones you can make) are much more precise.

Throw accuracy is more important than you might think. The actually amount of throw typically isn't real critical, but having identical throws on say both elevator halves typically is important. For example, you probably won't notice much differance in flight if your both your ailerons move 10 degrees or 11 degrees... but you WILL notice if one moves 10 degrees and the other moves 11 degrees.

Most planes of similar type will use similar throws when measured in degrees. Inch measurements will depend upon the size of the plane, where the measurement is taken, etc. This is what makes inch measurements unfriendly. By measuring in degrees, you can measure at any part of the control surface and compare throws to other planes, regardless of scale, location of measurement, etc.

You can make a really big throw gauge by taking a protractor like what Kevlar shows, and then run it through a copier and enlarge it, or scan it and blow it up on your computer, etc. I actually draw very large protractors in autocad and print them. By very large I mean if I made a complete circle, it would have a diameter of about 3 feet.

I tape (or insert into the surface) a very fine music wire that is the indicator for my protractor gauge. It is stiff enough that it doesn't bend much but light enough that it dosen't deflect the control surface. Remember to place the center point of the protractor gauge at the hinge line.

Cheers

Steve,
For $10.99 this tool can't be beat.
Best RC tool investment I ever made and I use it everyday.
Real nice when you start getting fussy with the measurements.
Sold by Tower http://www.greatplanes.com/accys/gpmr2405.html

As Whirley Bird I use the GP gage and the throw meter from Don's Hobby Shop,most measure from the center of the surface,but as long as the controls are the same it doesn't matter.

Personally, I think way too much is made of this issue. The throw recommendations made by the manufacturer are just that... RECOMENDATIONS.

This is by no means a critical measurement. In my lifetime I have never measured my throws with anything more complicated then my eyes.

This really doesn't call for a diagram, but far be it for me to turn down a request, so here's what I would do if I were going to actually measure it.

Block up a ruler so that one of the inch lines is centered on the control surface, then deflect the surface and see what it reads.

To make my point about how little this matters consider a few things: Let's say the MFGR recommends 5/8 throw, and in one hole, you get just under and another, you get just over. Are you going to drill a new hole in the servo arm or just pick one? And how often do you get the maiden flight in and then decide you need more, or less control? So what do you do measure it again? No, you just move a clevis in or out.

The bottom line is, don't be over critical. It's not like an eighth of an inch difference is going to make you crash your plane. If it is, you are not ready to do a maiden flight on your own, and should have a more experienced flier do it anyway. And if you're an instructor who thinks 1/4" difference is going to make you crash, I suggest you hand in your Instructor Certificate right now.

up to a point I agree with MinnFlyer,trainer?,but trying to fly a plane with precision,an 1/8 " mistake in control surfaces can make the plane be a hand full,try a large loop with the elevator half's misaligned or a rolling circle,even trimming a plane for level flight is a headache if the controls don't match. My ,o35 's for the day.

Yes, they GOTTA match, but we're not talking about matching, we're talking about how much they MOVE for an initial flight. After that, their throw will depend on how YOU want it to fly.

Give me ANY 40 - 60 size plane with 1/2" on all throws, and I will safely fly and land it, and then decide if anything needs to change.

All I am saying is that many people are overly concerned with this initial set up. The TLAR (That Looks About Right) system is good enough to get any plane in the air. And as I said before, if it's not, you're not a good enough pilot to do a maiden flight anyway.

For what it's worth I have to completely disagree about the great planes accuthrow. It's very poorly made and is useless on planes bigger than 40 size trainers. It only measures up to 2 inches of throw. I will sell mine to anyone that wants it

Thanks for all the ideas.One of the club instuctors is going to be doing the maiden.Glow is a big step from electric,everything is much bigger in comparison
steve

The lowly ruler works just fine but be sure that you centered your ailerons first with the AGP (or is it APG?) tool that is supplied in the 4*60 kit.

The wings are so bulbous at the trailing edge that one cannot accurately lay a straight edge across the wing and aileron to properly center. Sighting doesn't really work too well, either.

After these are centered, any of the suggestions above will yield the proper throws.

The protractor idea will work for those who want to measure degrees of throw instead of inches but you have to make sure that the radius center point of the protractor is EXACTLY on the center of the hinge line or you'll get a false reading. Obviously the inner portion of the protractor needs to be cut away to hold it over the surface being measured, but trying to judge where the center radius point is becomes pretty hard to do.
In most cases a ruler works just fine.

I fully agree with whoever said throws are just recommendations. That is very true. However, I'd like to emphasize that planes fly better if each control surface moves identical to it's twin. By that I mean if one aileron goes up 1" or 15 degrees or whatever, you want the other aileron to do exactly the same. For this reason, I suggest using a meter that can measure to at least 1 degree. It is just hard (not impossible) to get any sort of accuracy from the ruler method.

The GP throw thingy is better then nothing, but you'd be better off with a meter like this: http://www.centralhobbies.com/Tools/measurement.html

Sitck Jammer: Measuring from the hing line to the protractor is actually very easy There is no need to "judge" the distance... just measure it. Say you are measuring elevator throw. Fix the plane so the stab is at zero incidence. Measure the height of the stab from the table. Set the protractor to the same height (best to use an adjustable stand the the protractor mounts to.) Place the stand such that the hinge line is proper distance from the protractor. Simple.

I figured my post might cause confusion, I just wasn't sure how to fix it without making it needless long and confusing.

What Whirley Bird is covering in the last post is aileron differential. Ailerons produce more drag when in the down position than when in the up position. I won't give a full explanation of why this is, but it has to do with drag caused by generating lift.

If your ailerons are set exactly the same (i.e., same up as down travel) when you roll left, there is more drag on the right side of the plane. This causes the plane to yaw right... probably the opposite of what you want it to do since you are rolling left. This effect is called adverse yaw and the simple solution is to add aileron differential. In other words, the ailerons are set to travel up more than down. Other solutions exist such as mixing aileron to rudder on your radio. All planes suffer from this effect, but it is most noticeable on high lift airfoils, such as flat bottom airfoils.

In Whirley Birds post, the fix is performed mechanically by offsetting the holes in a servo wheel. It can also be done by changing the ATV or EndPoints on a computer radio.

What I meant when I said surfaces need to match is that similar movement needs to be replicated across matching control surfaces. If one aileron goes up/down 15 degrees, then the other one needs to do exactly the same. If you have aileron differential and one aileron goes up 15 degrees but only 10 degrees down, the other aileron still needs to exactly match this, i.e. it needs to go up 15 degrees and down 10 degrees.

Planes really do fly better when surfaces are accurately matched. Just like planes that are built very straight fly better than crooked ones.

Cheers

small point in so far as recommended throws; they are to be measured at the surfaces widest point as I understand it. (irregular shape rudder or elevator) hopes this helps

I agree the the throw meter from central is a nice device. There was a guy selling them on ebay for about $10 a while back which is similar priced to the accuthrow and much better in my opinion. Of course by looking at it you can see that it would be simple to make with a protractor, cloths pin and a few other items.