Adjustable tail surfaces

jpuke · Post by **jpuke** » Tue Aug 16, 2011 12:41 pm

How do you all make adjustments for the elevators and rudders? I know the old Guillows book says to bend and blow on these to make adjustments but I'm looking for a bit more.

What I've done in the past is make the rudder and stabilizer in two pieces and slip thin pieces of aluminum (cut from soda cans) to make the hinge. Unfortunately this makes them a bit heavy.

Maybe a better question is how do you trim models if they don't have adjustable tail surfaces?

ADW 123 · Post by **ADW 123** » Tue Aug 16, 2011 1:19 pm

you can use the clear plastic some kits supply for windshields. the key in terms of the elevator, is to balance the model well. a well balanced model with downthrust and a flat elevator/stab will eliminate the need for any moveable surfaces on the stab. i use the plastic on the rudder especially and bend it for a turn. usually ill have washout on the wings to ensure a flat, smooth turn.

Steve Blanchard · Post by **Steve Blanchard** » Tue Aug 16, 2011 1:38 pm

J,
None of my models have adjustable tail surfaces. There is a tendency for these to get knocked out of trim from handling. There are a lot of articles and discussions on several forums about trimming. I'm going tell you what I do and what works for me.
1. Be sure to put the various parts of the model together in proper alignment with all of the correct incidences and dihedral. I always have the Stabilizer as the zero and the incidence is in the placement of the wing(s) to start off.
2. Get your CG correct per the plan by adding weight on either end.
3. Test glide. This can be done with or without the prop whichever works best for you. Just know that the trim WILL change once the prop goes on.
4. DO NOT remove or add weight to adjust for dives or stalls as this will change the CG.
5. If it dives add a little up elevator and the opposite for stalls. This is where your real question comes in. When you build the fuselage leave an enlarged opening for the stabilizer so you can shim in various incidences as you trim. If you need excessive movement of the stabilizer for a good glide then there would probably be an issue in how the wing is attached.
6. Once you get the glide you then start your powered flights and deal with stalls and turns with thrust adjustments. Do not add weight or move the tail surfaces to make any changes as you have already got a good glide with the proper CG.

I hope this helps. It is very condensed.

Steve

kittyfritters · Post by **kittyfritters** » Tue Aug 23, 2011 1:28 pm

I have done it both ways and I have come to the conclusion that adjustable control surfaces on free-flight scale models are not worth the trouble. It is too easy to knock out trim adjustments just handling and transporting the model. Also, many models are too sensitive to trim adjustments done with control surfaces. Sometimes almost imperceptible changes in rudder or aileron adjustments can cause a stable model to go violently out of control. It's much easier to simply take care and build them straight and trim over tall grass.

Phugoid · Post by **Phugoid** » Wed Aug 24, 2011 4:24 pm

I hate to disagree with kittyfritters but I like to have adjustable tail surfaces as it makes trimming easier, and they are simple to do with the wire bag ties that come with sandwich bags.

Once adjusted and the model trimmed they are simply "frozen" in place with CA, no problems of movement etc......

Andrew

kittyfritters · Post by **kittyfritters** » Wed Aug 24, 2011 7:29 pm

Well, I will have to admit that I would not have gotten my 500 series Stuka to fly without adjustable everything, but I find that an exception.

Arlo DiPasquale · Post by **Arlo DiPasquale** » Wed Aug 24, 2011 8:02 pm

wow... you're ambitious to try and fly the 500 series Stuka!!

kittyfritters · Post by **kittyfritters** » Thu Aug 25, 2011 12:05 am

Yes, pigs can fly!

And, yes, it is in Japanese markings.

Phugoid · Post by **Phugoid** » Thu Aug 25, 2011 2:13 pm

Nice!

mustangman · Post by **mustangman** » Sat Aug 27, 2011 10:50 am

Hi to all! I have used twist ties , i just strip the outside off of the twist tie then you have thin gage wire. did that on my stuka!! Mark

jpuke · Post by **jpuke** » Mon Aug 29, 2011 5:05 am

Thanks for the responses and advice. I'm trying my next model without adjustable tail surfaces. I went back and looked at the Bird Dog that I just made and I glued the stab right where it should be but the angle was all wrong, with the rear of the stabilizer angled upward. Every time I would try to fly it, it'd go for a few seconds and promptly nose dive into the ground. This time I'll pay more attention to the angles.

The frustrating thing was that I did a good job on the model. I kept it very light (for me) at only 23 grams with everything installed (motor, nose weight, prop) so I had hopes that it'd be a good flyer.