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Wing Tubes for Servo Leads

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Wing Tubes for Servo Leads

Old 10-19-2006, 09:15 AM
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WacoOne
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Default Wing Tubes for Servo Leads

What is the best system for routing aileron/flap servo leads through the wing? I've always made a paper tube by wrapping paper around a dowel and sealing it with thin CA after the dowel was removed. There must be something ready made like thin walled plastic tubing, etc. Any suggestions?

Bill
Old 10-19-2006, 09:29 AM
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Texan2
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Default RE: Wing Tubes for Servo Leads

I have used thin wall alluminum tubing from hobby shops or hardware stores. While you are at the hardware store, ask around for something plastic.
Old 10-19-2006, 10:00 AM
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Default RE: Wing Tubes for Servo Leads

I make spiral-wrapped tubes (like a paper towel roll) out of computer paper. Cut the strips about 1 1/2" wide, paint a thin strip of thinned yellow glue (very little glue needed) close to one edge and wrap it around a suitable size peice of brass tubing. As you approach the end of the brass, slide it out a little farther and keep wrapping. When the paper strip runs out, you just start up with another one.
It takes a little while to learn the technique, but once you've mastered it you'll never be stuck for the right size tube again.

An added bonus is that a piece of brass tubing the next size up, sharpened on the inside, will cut perfect holes in the ribs for the paper tube.
Old 10-19-2006, 11:34 AM
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TAZ
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Default RE: Wing Tubes for Servo Leads

i have used a product called plastic pipe snaps that is sold over here in the uk i'm sure you could find something similar over there. Basicaly it is as it sounds... a thin plastic tube that over laps about an extra half and is very light weight that you can rap arond pipes
Old 10-19-2006, 11:46 AM
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Default RE: Wing Tubes for Servo Leads

Hi guys,

Aluminum tubes maybe nice, but I guess it also depends on how big the plane is. Do you really need tubes or just a way to get the servo wire thru the wing. A method that I use that works good is a thin fishing line with a small weight attached. If their is a small hole in each rib, just let the small weight fall thru the holes (holding the wing wing tip down) until it reaches the servo bay. Tie or tape to the servo lead and pull thru the wing. If it's a tube you need again depending on the size of the plane. I just roll a small 1/2inch paper tube and Zap it in a few spots. Remember to keep it light. Again depending on the size of the plane an aluminum or brass tube will add more weight and cost more.


Good Luck
Old 10-19-2006, 12:41 PM
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dmcmike
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Default RE: Wing Tubes for Servo Leads

hit the LHS, look in the model rockets section for lightweight tubes used for rockets. They work great, can get about any diameter you need, easy to cut to length.
Old 10-19-2006, 01:03 PM
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meaden
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Default RE: Wing Tubes for Servo Leads

Rocket body tubes they work great.

http://www2.towerhobbies.com/cgi-bin...?&I=LXF571&P=7
Old 10-19-2006, 01:45 PM
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Tall Paul
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Default RE: Wing Tubes for Servo Leads

Installing the servo leads prior to covering, you don't need sleeves.
Just a keeper on any connections between the servo lead and an extension.
E'eddie's way works well if you've planned ahead and have nice holes aligned in the ribs.
You could also attach the pull-thread to a stick and run it thru the holes, if the configuration permits.
Old 10-19-2006, 02:48 PM
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scratchonly
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Default RE: Wing Tubes for Servo Leads

I roll file folder material into an oval tube with a half inch overlap. This requires appropriate oval holes in the ribs but does not weaken the ribs as much as a round hole. Bit of medium CA here and there holds them to the ribs.
Old 10-20-2006, 04:00 AM
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Default RE: Wing Tubes for Servo Leads

I used paper tubes just once and now don`t use anything at all. I build a drawstring into the wing at covering time and have never had any hassles. When I tie the drawstring to the servo plug, or where there is an extension lead connected, I make sure the connection is wrapped with masking tape rolled to a basic 'arrowhead' shape so it doesn`t hang up at a wing rib halfway through.....

Works fine for me - saves a little weight too.

Alan W
Old 10-20-2006, 07:59 AM
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Newc
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Default RE: Wing Tubes for Servo Leads

I've always made a paper tube by wrapping paper around a dowel and sealing it with thin CA after the dowel was removed.
So why change from what works and is probably the lightest method? This is the technique I use unless it is in a foam wing that's going to be vacuum bagged for balsa sheeting. For these I use thin - 1/64" - balsa wrapped around the same dowel.
Old 10-20-2006, 08:00 AM
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Newc
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Default RE: Wing Tubes for Servo Leads

This requires appropriate oval holes in the ribs but does not weaken the ribs as much as a round hole.
Actually, I think you have it backwards. A round lightening hole is stronger than an oval one.
Old 10-20-2006, 08:28 AM
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Default RE: Wing Tubes for Servo Leads

ORIGINAL: Electriceddie

Hi guys,

Aluminum tubes maybe nice, but I guess it also depends on how big the plane is. Do you really need tubes or just a way to get the servo wire thru the wing. A method that I use that works good is a thin fishing line with a small weight attached. If their is a small hole in each rib, just let the small weight fall thru the holes (holding the wing wing tip down) until it reaches the servo bay. Tie or tape to the servo lead and pull thru the wing. If it's a tube you need again depending on the size of the plane. I just roll a small 1/2inch paper tube and Zap it in a few spots. Remember to keep it light. Again depending on the size of the plane an aluminum or brass tube will add more weight and cost more.


Good Luck
This is the way I re-wired my Waco wing at the field after a servo wire had become un-attached. Works well, but I would like to have installed some type of tubing, There are a couple of sites that sell this cardboard tubbing in different diameters for just this purpose.
Old 10-20-2006, 11:09 AM
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Default RE: Wing Tubes for Servo Leads

I think scratchonly is suggesting a hole that is smaller vertically than would be required with a round shape - to allow passage of the servo connector. So it would make a stronger wing than the (taller) round hole.

ORIGINAL: Newc

This requires appropriate oval holes in the ribs but does not weaken the ribs as much as a round hole.
Actually, I think you have it backwards. A round lightening hole is stronger than an oval one.
Old 10-20-2006, 12:03 PM
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Default RE: Wing Tubes for Servo Leads

Yea I think your right! A squished round hole that is now oval, first started out as round as a hole!!!!

LOL...
Old 10-20-2006, 12:27 PM
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Newc
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Default RE: Wing Tubes for Servo Leads

No matter the reasoning for the oval, it is weaker than a round hole. One reason is that the side with the sharper curve is an open invitation to stress and fracture. If you look at full scale planes and race cars, while there are a lot of spaces where an oval lightening hole would fit nicely, they only put lightening holes in where they can get a round hole.
Old 10-20-2006, 12:30 PM
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Default RE: Wing Tubes for Servo Leads

I kow I get it.

It was a joke, did you get? look at the last word.
Old 10-20-2006, 01:31 PM
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scratchonly
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Default RE: Wing Tubes for Servo Leads

Because the servo plugs are flat, a horizontal oval removes LESS material; use whatever pleases you.
Old 10-20-2006, 05:23 PM
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Default RE: Wing Tubes for Servo Leads

Here is what you are talking about?
I would agree that it is stronger than the circle in this location, for most normal loads.
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Old 10-21-2006, 12:20 PM
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scratchonly
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Default RE: Wing Tubes for Servo Leads

Whew; I'm glad SOMEONE gets it!
Old 10-21-2006, 04:59 PM
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Newc
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Default RE: Wing Tubes for Servo Leads

I kow I get it.

It was a joke, did you get? look at the last word.
My subsequent post wasn't in response to yours.

Here is what you are talking about?
I would agree that it is stronger than the circle in this location, for most normal loads.
Nope - Under all conditions the circle is stronger. And especially under these conditions where all loads are vertical (bending). The fact that 'less material is removed' is immaterial compared to the strength of a round hole versus an oval one since the oval one has greater stress areas. Have any aerodynamic aluminum tubing lying around - like is used for wing supports? If so, see what the force required to bend it is and then compare it to the same size and material round tubing. The round tubing will resist bending much more than the oval, aerodynamic tubing, and it's the bending forces that are of concern with a wing.
Old 10-21-2006, 06:02 PM
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Default RE: Wing Tubes for Servo Leads

Newc said:
"Nope - Under all conditions the circle is stronger. And especially under these conditions where all loads are vertical (bending). The fact that 'less material is removed' is immaterial compared to the strength of a round hole versus an oval one since the oval one has greater stress areas. Have any aerodynamic aluminum tubing lying around - like is used for wing supports? If so, see what the force required to bend it is and then compare it to the same size and material round tubing. The round tubing will resist bending much more than the oval, aerodynamic tubing, and it's the bending forces that are of concern with a wing."
[/quote]

Wrong.
While you are correct that, in some cases, the stress concentration may be detrimental and cause a failure, it is entirely dependent on the situation. Your blanket statement ("under all conditions") goes way too far.
Let me explain.
Here is a sketch of a typical beam under stress. I will not pretend that it is comparable to the wing rib cutout case we are talking about because there are MANY different loads that a wing rib might have to deal with, depending on the circumstances (and some of these will be contradictory to other situations, maybe even the opposite).
The sketch shows lightening hole in a beam, one in the center and one near the end. They are both round holes in this case. The failure of the beam will probably be at a hole. The type and location of the failure is the issue. The stresses in the center of the beam will have maximum compression at the top and maximum tension at the bottom, and the beam will fail at one or the other depending on the material properties. A material with good tensile strength but poor compressive strength (styrofoam with a packing tape skin) will fail in compression - at the TOP of the center hole. A material like plaster (little tensile strength) will fail at the BOTTOM of the hole. There are NO shear loads in the center of this beam and the failure will NOT be at the sides of the hole.
The outboard case is just the opposite, shear loads are at maximum, compressive and tensile loads are minimal. A failure at this hole will be on the sides, as the little cracks show.
Making the center hole a horizontal oval, leaving more material near the top and bottom of the beam, will be stronger than with the circle because the stresses are NOT at the ends of the oval anyway. Making the outer circle a horizontal oval WILL be bad because the already existing stresses are made worse by the shape.
How does this equate to our wing rib? Normal lift loads are very similar to those in this sketch, for the center hole. Other loads, like hard landing, extreme rolling action, rough handling, etc. will be different and all bets are off.
In any case, I have seen lots of places where oval lightening holes are used on structures because, in some cases, they are okay or even better.
Regards,
Allan
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Old 10-22-2006, 07:22 AM
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Newc
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Default RE: Wing Tubes for Servo Leads

How does this equate to our wing rib? Normal lift loads are very similar to those in this sketch, for the center hole.
Actually, I don't believe that this is correct. The sketch shows the bending forces from the front to the back of the wing (ribs), not the longitudinal forces from the wing root to the tip as with a wing with lightening holes. I stand by my engineering materials background that round holes and structures are stronger than oval ones – especially in compression acting on the vertical as in a wing rib – and since it seems that you won't agree with this, and the differences probably won’t ever show up in our over-designed (high safety factor) airframes, I’m going to let it drop.
Old 10-22-2006, 12:02 PM
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Default RE: Wing Tubes for Servo Leads

I apologize to everyone for starting this hole-e-er than thou argument.
Old 10-23-2006, 09:55 AM
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Default RE: Wing Tubes for Servo Leads

Hear ye Hear ye,

Ahole is stronger then an oval! Why because when the hole was a little boy it was an oval, short and weak. But when the boy grew up and became a man, he grew into ahole and got stronger.



Come on it's funny . you know it is.

I can hear you laughing now...........

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