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Pull/pull control help

Old 10-09-2018, 05:06 PM
  #1  
jegbflat
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Default Pull/pull control help

Hello, finishing up a little Bleriot slow flier for indoor and stuck on how to secure the pull string(s) from servos to tail. Would someone care to share ideas? I purchased some no-stretch thread but not sure how best to attach it to servo arms and rudder/elevator control horns.

Thank you,

Jerry
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Old 10-09-2018, 05:34 PM
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Rabbitcreekok
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I am not sure what you mean by stretch thread, but if the thread stretches any at all you should not use it for control connections. You will not have positive control of the surfaces. The amount of deflection of the surfaces will be dependent upon the speed of the airplane, as more airflow over the surfaces will cause less deflection for the same amount of control stick movement.


Perhaps that will not make much difference in a slow flyer, but I would just use normal thread that does not stretch. I assume that you are using pull-pull controls.
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Old 10-09-2018, 06:13 PM
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jegbflat
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As stated in my post, the thread i have is "no-stretch" and my question is how to attach/secure it to control arms. Thank you
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Old 10-10-2018, 05:21 AM
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max2112
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Originally Posted by jegbflat View Post
Hello, finishing up a little Bleriot slow flier for indoor and stuck on how to secure the pull string(s) from servos to tail. Would someone care to share ideas? I purchased some no-stretch thread but not sure how best to attach it to servo arms and rudder/elevator control horns.

Thank you,

Jerry
Hi Jerry, WELCOME to Wattflyer! It's always great to see new faces.

I have had two models that used a pull/pull setup before and I was lucky enough to have enough random hardware on the shelf to fit the the bill. Here are some links and pictures that are almost exactly like the setup that I used:

Servo attachment.

Hardware the string attaches to. This is what slides into the servo.
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Old 10-10-2018, 06:03 AM
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jegbflat
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Thanks for your reply John. I wonder if your planes were larger than this one? I like the functionality of what you suggested, but I'm concerned about the weight. Attaching a photo of my Bleriot-youll see it's ultra light, especially in the tail.
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Old 10-10-2018, 07:29 AM
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Rabbitcreekok
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Originally Posted by jegbflat View Post
As stated in my post, the thread i have is "no-stretch" and my question is how to attach/secure it to control arms. Thank you

My bad, Jerry. I just did not see the no part of no-stretch. Sorry for my long dissertation about something you already knew.
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Old 10-10-2018, 01:12 PM
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solentlife
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For adjustable end - a small selftapping screw can be used where the thread is tied to the screw ... touch of CA to lock the thread to stop it slipping ... then screw the screw into the horn / arm .. the thread then winds round the screw as it goes in. Once a few turns are on ... loop other end through ar, / horn hole and tie of. Final adjustment of screw to set.

Nigel
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Old 10-11-2018, 12:51 AM
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quorneng
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For an indoor plane I would have no hesitation in using mono filament fishing line for the pull/pull cables, 7 lb (3 kg) or even thinner.
Yes it ultimately stretches but not at the sort of control loads in a light indoor plane.

This is the rudder pull/pull on my RC scratch built Depron 1020 mm span Super Cub which although a lightweight is definitely an outdoor plane.
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The pull/pull is a single piece of 7 lb filament tied at the servo arm, it passes through the rudder horn, through the rudder, through the horn on the other side and back to the servo arm. A method very popular with early Sopwiths!

Done like this the pull/pull can be tightened and secured at the servo arm without regard to the rudder position. Once the servo is correctly centered the rudder can be finally positioned and secured with a dab of glue where it passes through the rudder.
Very light and simple to set up.
My Super Cub has had quite a hard life but the rudder and elevator mono filament pull/pulls are original.
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Old 10-11-2018, 06:11 AM
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jegbflat
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Thanks to all who've replied. You've given me some great ideas and insight. Installed the rudder/elevator tonight so now time to make the control decisions. I keep coming back to how incredibly light and fragile this thing is. I'll post a pic tomorrorw. You'll see why what i do to link servos and tail must be super simple and lightweight.

I like the idea of string only without additional hardware. Your suggestions are greatly appreciated.

Jerry
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Old 10-11-2018, 08:03 PM
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jegbflat
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Ready for radio and control linkages...
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Old 10-11-2018, 09:39 PM
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Rabbitcreekok
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Jerry, that is a really nice looking airplane. You have done a great job with the build.
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Old 10-12-2018, 03:15 AM
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jegbflat
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Thanks Jim...actually im a bit apprehensive about flying it. The darn thing's so delicate and very different than anything ive had before. But if it flies as slow as advertised it should be a hoot.
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Old 10-12-2018, 07:28 AM
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Are you planning on flying it indoors? If not be sure and fly in in completely calm air. It is so light that even a small movement of the air will move it away from you. It will fly easily in a basketball court, I am sure.
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Old 10-13-2018, 01:42 AM
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jegbflat
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Yes, indoor only...fortunate that local group has access to a middle school gym couple times a month for indoor fliers.
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Old 10-18-2018, 02:30 AM
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max2112
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Originally Posted by jegbflat View Post
Thanks Jim...actually im a bit apprehensive about flying it. The darn thing's so delicate and very different than anything ive had before. But if it flies as slow as advertised it should be a hoot.
She's a beauty for sure, Jerry! Well done on your build.

I did catch that you were aiming for indoor flying but I didn't realize just how light you talking about. You could do a glide test over a comforter to confirm CG.

I bet she flies perfect first time out!
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