Carbon wing joiner: diameter? How make outer tube? - RC Groups
Thread Tools
Jan 23, 2013, 11:46 AM
Registered User
sroge's Avatar

Carbon wing joiner: diameter? How make outer tube?


I am scratch building this 72" (10-11 lbs) aerobatic plane—like an Extra 300. At least in germany it doesn't seem very easy to get a tube wing joiner. There's one shop selling them, but they charge €40 (~$50) for a 40" tube of 1" diameter with an outer tube. I think this is quite expensive.

For a smaller plane I once took a standard aluminum tube from the hardware store and wrapped two sheets of paper around them, continuously applying wood glue. After drying and pushing it from the aluminum tube this was quite a good outer tube.

But now with my new and much bigger plane am thinking about using carbon this time.

2 questions:

—does anyone know a better way of making an outer tube, not using normal paper and wood glue?

—when building an aerobatic/3D plane, what dimension of a carbon wing joiner may be all right? Inner diameter, outer diameter, and how far should a joiner go into the wing (overall wingspan 72")? Half the way? And what dimensions for aluminum might necessary in comparison?

Last edited by sroge; Jan 23, 2013 at 12:11 PM.
Sign up now
to remove ads between posts
Jan 23, 2013, 12:20 PM
Hope to get out of life alive
kenh3497's Avatar
This might be a good question for the guys in the composite forum

Jan 23, 2013, 12:28 PM
Registered User
sroge's Avatar
OK, thought about that, too. But as my question is also about aluminum and making that outer tube I decided that this might be a better place.

Jan 23, 2013, 12:44 PM
An itch?. Scratch build.
eflightray's Avatar
Do you have any fishing tackle shops in your area, they sometimes stock blanks or sections of carbon fishing rod.

Or maybe using carbon arrow shafts, I don't know what diameters they go to, but you could always use two or three.

Actually they probably don't even need to be carbon, just good quality fiberglass would probably do. (Or even hardwood dowel).

Considering we used to fly 6 footers with balsa spars and maybe some ply bracing, I sometimes wonder if we may go a bit overkill these days. I don't think carbon tubes were even available back then.
Jan 23, 2013, 11:50 PM
Leroy G.
Leroy G's Avatar
Im building a bashed Tiger sport plane with slip tube mounted wings which could just as well be a tube joiner for a bolted on wing and my wing is also close, 74" to yours. The tube is 3/4" aluminum, was for a AT-6 90" wing so I know it's strong enough for ours. Outer sleeve is made on the tube of 1.5 oz. fibreglass and resin, there is a thread showing how it's done on my build.

See it here: hope this helps, Leroy
Jan 24, 2013, 12:13 PM
Bleriot's R Us
xairflyer's Avatar
Check out phenolic tubes you normally buy the tube with a matched alum tube for the inside.
I am sure you can get them in Germany, this is a UK supplier
Falcon Aviation
Jan 24, 2013, 12:27 PM
Registered User
Joel K. Scholz's Avatar
Find a kite material supplier like Peter Lynn international. They will have a variety of fiberglass and carbon spars.
Jan 24, 2013, 12:40 PM
Registered User
sroge's Avatar

thanks to all you guys! I will keep the carbon stuff in mind for my next project. This time I based my decision on budget an availability. I don't like it, but felt I had no other choice. I bought a tube of 3/4" with 1.5mm at a hardware store. This was 5, which is about 7. Here in germany I found several manufacturers and distributors and carbon tubes around 1"/1mm cost between $25-$45. Nevertheless the aluminum will give me two or three additional ounces :-/

As for the outer tube I will try several kinds of paper. Normal copy paper works quite well, but maybe brown packaging paper will be better..

Jan 24, 2013, 08:26 PM
Rob H
rph1225's Avatar
I just completed a profile that I did my own outer tube with fiberglass cloth and resin. At first I had thought it was going to be tough to do, but actually was very easy. I took the inner tube that I wanted to use and wrapped wax paper around it about 3 times, using masking tape to hold it in place.

Then I cut a piece of fiberglass cloth, so it would also wrap around the tube 2-3 times and soaked it with resin. After wrapping it around, I took another piece of wax paper and wrapped it around the fiberglass. Then starting at the center of the tube, start wrapping the tape to the end, overlapping at least half of the tape on every wrap. After, flip the tube over around and do the other half.

Once cured for about a day, the inner tube will just slip out and you can then pull out the wax paper.

Here is a site I used that kind of shows the way I did it.
Last edited by rph1225; Jan 24, 2013 at 08:31 PM.
Jan 25, 2013, 02:38 PM
Registered User
sroge's Avatar
Well, this is how I will finally do it: I experimented with several combinations of copy paper, packaging paper, wood glue and epoxy. I wanted to know what I could make out of the stuff I got in my workshop before buying something.

For my test I used am 0.6" aluminum tube and packaging paper. Using epoxy I only had to build up 0.7 mm of layers to give me even more stability as with 1.9 mm of wood glue. For a 5" outer tube the weights are 4g and 11g—quite a difference.

I think that the outer tube only has to stable enough to protect itself from being bent or otherwise broken during handling. Everything else is provided my the inner tube. The photo shows the epoxy tube, the inner aluminum tube and the wood glue tube. Sealed the ends with CA.


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion How to make a disser wing? Sarboy Hand Launch 22 Dec 30, 2016 06:27 AM
Help! Stuffing Tube Diameter jjac Racing Boats - Electric 7 Jan 16, 2013 08:09 AM
Question method for fabricating joiner tube outers soargasm Composites Fabrication 27 Mar 22, 2011 10:45 AM
Help! how to make carbon fiber wing tube MSQ Composites Fabrication 11 Feb 13, 2007 11:50 AM
For Sale PBG 7/16 carbon wing joiner tube Steve H. Aircraft - General - Miscellaneous (FS/W) 1 Nov 05, 2005 01:29 PM