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GLASS OR CARBON TUBES

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Old 08-03-2012, 03:09 PM
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sidgates
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Default GLASS OR CARBON TUBES

I need two tubes that will mount in a fuselage and the wing spars will plug into these tubes. Does anyone know where to buy them or how to make them?

Dimensions are:
.565 I.D. x 8.25" long
6mm I.D. x 8.25" long
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Old 08-03-2012, 03:16 PM
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Default RE: GLASS OR CARBON TUBES

I get mine here, and they are used in all my designs:
http://www.tntlandinggear.com/store/...ne_catalog.htm
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Old 08-03-2012, 04:33 PM
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Default RE: GLASS OR CARBON TUBES

You can use a mold release wax on the tubes and then wrap them in a spiral pattern with fiberglass strips saturated with epoxy resin. After the resin has cured, you can pop the tubes off your original tube.
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Old 08-03-2012, 06:49 PM
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Default RE: GLASS OR CARBON TUBES

I didn't find any that fit my wing spars but they look like a good source for future designs.
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Old 08-03-2012, 08:08 PM
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Default RE: GLASS OR CARBON TUBES

Here is a little video except that I made and uploaded for you. It shows how to make your own perfectly fitting composite sleeves that are more robust that pultruded tubes.

https://vimeo.com/46916322

I would wax a piece of your carbon rod with Part-all paste #2 (3-4 coats) and then dip it into Part-all Film #10 (PVA) and hang it by one end to drip-dry. The PVA film will give you a better/more reliable release and give a little clearance. To start the electrical tape you cut off a piece and stick 1/2" of it sticky-side to sticky-side to the tape on the rest of the roll. This can then be stuck to the mandrel and the rest of the tape on the roll will be wound around the mandrel so the none-sticky side is against the wet fabric. You can then reverse the process on the other end to hold it into position.
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Old 08-04-2012, 07:12 AM
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Default RE: GLASS OR CARBON TUBES

Wyowindworks - Thanks for the video and how to note, your comments are always helpful. I had thought about doing the method you describe but was concerned it would not release after curing.

I have had success on very short sleeves(less than 1") I made out of glass but I was concerned about the release when I make one longer. I will give your method a try.
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Old 08-04-2012, 07:44 AM
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Default RE: GLASS OR CARBON TUBES


Quote:
ORIGINAL: sidgates

Wyowindworks - Thanks for the video and how to note, your comments are always helpful. I had thought about doing the method you describe but was concerned it would not release after curing.

I have had success on very short sleeves(less than 1") I made out of glass but I was concerned about the release when I make one longer. I will give your method a try.
The key is the dip, or double dip, of PVA. Wax alone can make for a pretty difficult release. If the sleeve is difficult to remove you can soak it on some water to soften the PVA. If your mandrel is carbon you can heat the layup to aid in removal since the CTE of glass is much higher than carbon. If the mandrel is aluminum you want to cool it since the CTE of aluminum is greater than the glass.

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Old 08-04-2012, 11:06 AM
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Default RE: GLASS OR CARBON TUBES

I have used these guys in the past for fiberglass and tubing needs

http://www.acpsales.com/OnlineStore.php

and specifically for you

http://www.acpsales.com/Composite-Tubes-and-Rods.html

I just checked and your sizes aren't listed although there was a .5625 tube...how "married" are you to those sizes? Can you substitute other nesting tubes? :-)

Don
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Old 08-05-2012, 07:01 AM
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Default RE: GLASS OR CARBON TUBES

hattend - Thanks for the links. I need the tubes to go through the fuselage on the Modelbau F-86D. The model comes all finished except for hinging the controls and installing both tubes in the fuselage to accept the wing spars.

The wings have tubes that perfectly fit the two wing tubes furnished but no tubing is supplied to go in the fuselage. The existing holes in the fuselage are oversize by almost 1/8".

I will make the tubes as described by WyoWindWorks, it is not too hard since I have all the materials needed.
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Old 08-05-2012, 09:12 AM
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Default RE: GLASS OR CARBON TUBES

Many models utilize a pass-through joiner...meaning that there is no tube in the fuse. The joiner just goes through an oversized hole. Two smaller pins are used to index the wings. One in the front and one in the rear. The joiner carries the bendng load of the wing while the pins keep the wing oriented to the fuse. The indexing pins just carry a small shear load.
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Old 08-05-2012, 10:16 AM
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Default RE: GLASS OR CARBON TUBES

The full width joiner may be over kill but costs so little in weight I plan to go with it. The joiner will be fiber glassed to the inside of the fuselage to transfer the wing lifting force to the fuselage sides.

With a jet where the "G" force can be easily 10-12 I will feel better with the full width joiner. This wing design also has locating pins to maintain alignment.
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Old 08-05-2012, 11:32 AM
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Quote:
ORIGINAL: sidgates

The full width joiner may be over kill but costs so little in weight I plan to go with it. The joiner will be fiber glassed to the inside of the fuselage to transfer the wing lifting force to the fuselage sides.

With a jet where the "G" force can be easily 10-12 I will feel better with the full width joiner. This wing design also has locating pins to maintain alignment.
The joiner needs to be full length. It would go into the joiner tube on one wing half, through the fuse, and into the joiner tube on the other wing half. There is just an oversized hole through the fuse. This often done because the joiner has a dihedral in it which makes a tube in the fuse an impossibility. Dynamic Soaring gliders that are full of lead and pulling 50-60 g's, or higher, are done this way. The lifting load and pitching moment is carried by the shear strength of the indexing pins.

Obvisouly, putting a joiner tube through the fuse isn't going to hurt anything. Did the manufacturer intend for there to be one?





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Old 08-05-2012, 12:02 PM
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Default RE: GLASS OR CARBON TUBES

Just to clarify. I don't have dihedral to deal with. I have a one piece tube that goes into each wing and through the width of the fuselage.

When you use the PVA as a dip coating, do you buff it after the first coat? If I put on two dip coats should I buff the second coat?

I just finished waxing 5 coats and have dipped the first PVA coat.
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Old 08-05-2012, 12:06 PM
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Default RE: GLASS OR CARBON TUBES


Quote:
ORIGINAL: sidgates

Just to clarify. I don't have dihedral to deal with. I have a one piece tube that goes into each wing and through the width of the fuselage.

When you use the PVA as a dip coating, do you buff it after the first coat? If I put on two dip coats should I buff the second coat?

I just finished waxing 5 coats and have dipped the first PVA coat.
No buffing is required, nor is PVA buffable. If you'd try and buff it the PVA would just peel right off.....at least it should. The PVA should look pretty glossy with a continious film after a dip coat.


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Old 08-05-2012, 12:28 PM
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Default RE: GLASS OR CARBON TUBES

OK, back to basement work bench.
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Old 08-07-2012, 08:46 AM
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Default RE: GLASS OR CARBON TUBES

WyoWindWorks - The manufacturer doesn't say what they intended but obviouly to me you need a tube through the fuselage or someway to transfer the wing lift force to the fuselage.

I did the layup on the two spars and now trying to get the glass tubes off. The larger tube is carbon and I am soaking it in water hoping to disovle the PVA. I can see it starting to release in a few spots.

I put the 6mm aluminum tube in the freezer and will try again to release the outer glass tube in a few hours. I am open to any other suggestions. If I don't get a release I can always slit the tubes length wise and remove them then do a layup over the slit and they will be usable.
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Old 08-08-2012, 07:45 AM
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Default RE: GLASS OR CARBON TUBES

I gave up on getting a release for the glass sleeves from my tube spars so I taped a straight edge to the outside of the glass layups and slit them lenght wise. I have now filled the cut slit with epoxy and waiting for them to cure.

I will probably lay two more layers of 3.2oz cloth in the outside of the glass tubes since I deliverately made them a little thin in case I had to cut them off the spar tubes.
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Old 08-08-2012, 10:12 AM
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Default RE: GLASS OR CARBON TUBES

SidGates, what kind of resin did you use to make the tubes?
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Old 08-08-2012, 11:37 AM
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My resin is West Systems 105 and West Hardner 206. That is about all I have used for the past 4 years but plan to buy one of your recommendations when I run out.

My glued seams look good so nothing is lost. As soon as the seams fully cured I will sand the outside with 80 grit and then lay on a couple more layers of cloth. My tubes should then be very functional.

I am suspicious that my PVA isn't the best. It is a "no name" product recommended by a modeler who did a lot of glass work. I watch other part separations on video and my separations are OK if I can pull 90 degrees to the molded part surface, if I am pulling at less than 90 it is very hard to get separation. Of course the tubes I made are a "0" degree pull. I was hoping the double PVA dip would do the job.
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Old 08-09-2012, 12:44 PM
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Default RE: GLASS OR CARBON TUBES

I couldn't find a tail boom or any other tubes that fit the spars so decided to make my own.
First I waxed the spar tubes and a couple of coats of PVA. I wasn't confident I could get the fiber glass to separate so I only wound on 3 layers of 3.2oz cloth.

After curing I couldn't get the glass to separate so I slit the glass length wise with an Xacto careful to not go completely through the glass and scratch the tubes. After scoring the glass 3-4 time I was able to slip the xacto #11 under the glass and finish the cut from the inside.

Next I sanded the outside of the glass with 80 grit and then glued the fiber glass tube back together with epoxy. Next I added 5 more layers of 3.2oz cloth to the outside.

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Old 08-09-2012, 01:13 PM
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Default RE: GLASS OR CARBON TUBES

I have done this before using a single layer of wax paper rolled neatly one and a half times around a tube that has been lightly greased with petroleum jelly (I.e. grease the tube then apply the wax paper). The paper is secured with a small piece of clear tape and the petroleum jelly will cause it to cling to the tube. One it has cured it the new outside tube will slide off and the wax paper pulls out. The fit of the finished article is very neat.

Make sure you sand the cured fiberglass before trying to remove it and wear some decent gloves when removing it.

Good luck,

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Old 08-09-2012, 03:59 PM
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Default RE: GLASS OR CARBON TUBES

yojoelay- Your method sounds easy. I will try it next time. How long a tube have you made with this method.
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Old 08-10-2012, 01:03 PM
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Default RE: GLASS OR CARBON TUBES


Quote:
ORIGINAL: wyowindworks

Dynamic Soaring gliders that are full of lead and pulling 50-60 g's, or higher, are done this way. The lifting load and pitching moment is carried by the shear strength of the indexing pins.
I just read this hilarity. Thanks for making my day. I had a good laugh on the bolded part. Think you meant 5-6g's or higher. =)

PS> forget the tube, just build a carbon fiber molded I-beam. It will be lighter/stronger than a tube as well. Will really want vacuum bagging to get a good result though. Remember don't take the edge of the beam to the skin of your airfoils as it won't be perfectly flat and matching the true shape of the airfoil/bottom/top is danged hard in something other than wood.
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Old 08-10-2012, 01:44 PM
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Default RE: GLASS OR CARBON TUBES

Quote:
I just read this hilarity. Thanks for making my day. I had a good laugh on the bolded part. Think you meant 5-6g's or higher. =)
That wasn't a typo. Dynamic soaring gliders are flown in circles at over 400 mph.

The record DS glider (Kinetic 100DP) has done laps that have gone 498 mph. Here are some accelerometer readings for a 468 mph flight done by an onboard Raven data logger containing two accelerometers: http://www.rcgroups.com/forums/showt...5#post17294421

You can see that there were several circuits that were near 90 g's and many that were above 60 g.

This specific glider has a 100" span and is flown around 12-17 lbs (depending on ballast).

Here is an older but fun video of dynamic soaring at 399 mph: http://vimeo.com/8356047
In this video the lap times are right aroung 3 seconds. If the speed is 399 then the circle radius is 279.41 feet. If the circle was perfect the g-loading would be 38.09. In reality the circuit isn't a perfect circle but oblong which means that the top and bottom turn are tighter resulting in a higher loading.

PS - You don't need a vacuum bag to get good results with composites.



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Old 08-11-2012, 04:03 AM
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Default RE: GLASS OR CARBON TUBES

Bfoote - In post #9 I explain I need the tubes for an existing model, F-86D. I didn't have the option of tube or built up spar. In my scratch build of the F-94C I used a built up carbon spar.

WyoWindWorks know what he is talking about concerning "G" forces. Even in model jets it is not uncommon to get 10-12G pull outs from less than full power dives.
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