By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by CML

Carbon Fibre Tubes

All Topics | Latest Posts

Search for:  in Thread Title in  
Chris Walby03/07/2020 06:53:18
avatar
1277 forum posts
315 photos

Hi,

I want to use some carbon fibre tube inside another carbon fibre tube (wing tubes) as they are convenient sizes for the model.

The problem I have is that there is a seam on the inside of the outer (must be part of the extruding process) which causes the tubes to bind.

The inner tube needs to slide at least a foot into the outer and probably longer, so normal drill bits are too short. I have tried tipped masonry bits and they don't work. Looked at reams, but there is no easy way of making an extension for a ream.

Any suggestions as to how I can ream the seam out and what works well to lubricate carbon against carbon?

Thanks in advance

Ron Gray03/07/2020 07:39:43
2235 forum posts
978 photos

I had a similar situation a couple of years ago and what I did was to use a bit of alloy tube which was a bit smaller than the carbon one and then stuck some sandpaper to the alloy tube and used that to 'ream' out the carbon tube. Worked OK but I was lucky to have the alloy tube to use! Messy job!!!!

FlyinBrian03/07/2020 07:44:11
645 forum posts
4 photos
Posted by Ron Gray on 03/07/2020 07:39:43:

I had a similar situation a couple of years ago and what I did was to use a bit of alloy tube which was a bit smaller than the carbon one and then stuck some sandpaper to the alloy tube and used that to 'ream' out the carbon tube. Worked OK but I was lucky to have the alloy tube to use! Messy job!!!!

Alloy tubes of various sizes are available from most B&Q stores, not too dear.

Flyer03/07/2020 07:58:29
avatar
623 forum posts
108 photos

If you must use the carbon tubes, could you use a rod of smaller diameter with some glass paper glued around it and use as a reamer? The carbon tube I've used does sand quite easily.

Ade

Piers Bowlan03/07/2020 08:04:18
avatar
2167 forum posts
53 photos

Not too sure why you need carbon outers, I usually buy a K & S Ali or brass tube to fit my carbon wing joiner. Alternatively SLEC sell carbon tubes with phenolic outers specifically as wing joiners.

Peter Miller03/07/2020 08:24:02
avatar
11223 forum posts
1321 photos
10 articles

Stockists of J.Perkins ca get you various carbon tubes and carbon rods which I have used in the past

dscf4100 - copy.jpg

SR 7103/07/2020 08:26:15
avatar
462 forum posts
140 photos

I make my own outer tube from fibre glass

Lima Hotel Foxtrot03/07/2020 08:30:37
avatar
393 forum posts

My LMS Addlestone Models have lots of carbon tubes that are designed to nest. I suspect they come from JP.

Also, what is that interesting looking plane Peter Miller is building? It's not like his usual output.

perttime03/07/2020 08:34:45
avatar
164 forum posts
11 photos

What sizes are we talking about in this case?

Chris Walby03/07/2020 08:41:58
avatar
1277 forum posts
315 photos

Off topic, but if I use phenolic tube it comes out heavier.

Carbon spars

213.00

Card/ali spars

331.53

difference

118.54

OK its 118g on a 6Kg model, but its already heading over 36oz/sq ft wing loading and it does not need to be any heavier for no reason!

Thanks Ron/Flyer, I'll male some rod reamers and give it a go, its just the seam that needs to be removed

Peter Miller03/07/2020 11:19:18
avatar
11223 forum posts
1321 photos
10 articles
Posted by Lima Hotel Foxtrot on 03/07/2020 08:30:37:

My LMS Addlestone Models have lots of carbon tubes that are designed to nest. I suspect they come from JP.

 

Also, what is that interesting looking plane Peter Miller is building? It's not like his usual output.

THat plane is my MAK 15 MP. A russian powered glider from the 50s.The plans are with Kevin and there is a build blog on this forum.

I can tell you that it is a builders model. It flies well and It will do aerobatics

The Red Kite didn't like it

 

dsc_5165.jpg

blog2.jpg

Edited By Peter Miller on 03/07/2020 11:20:13

Manish Chandrayan03/07/2020 12:44:53
avatar
645 forum posts
73 photos

A dowel or alloy tube of suitable size with a slit to take one end of the abrasive cloth/paper.

Glue the end of the abrasive cloth/paper in the slit and tightly wind the remaining on to the dowel/tube to form a reamer.

The tightly wound end should just slide in the carbon tube to be reamed. Once inside, the open end will expand and give a snug fit.

Rotate to sand off the seam line. Carbon dust will get everywhere so take care

Chris Walby03/07/2020 12:46:43
avatar
1277 forum posts
315 photos

Perttime

The outer tube ID is 14mm and I have a cunning plan, more cunning than Baldrick's plan.....Just noticed that Perma-Grit do a 14mm round tube file, I can then turn a plug and Loctite it in the handle. Screw a bit of bar into the plug and get the battery drill out!

Oorrr I feel a Perma-Grit order coming on!

Martin Harris03/07/2020 13:02:18
avatar
9411 forum posts
256 photos

Do be careful with the carbon dust - it's supposed to be very hazardous to the lungs and quite possibly carcinogenic. Best not to get it into the house or workshop...

Bruce Collinson03/07/2020 13:16:42
543 forum posts

Mind the dust, try candle wax between them; we use it on carbon fly rods to prevent binding; maybe try a short section first, as the ferrule even on a 15' salmon rod is about 3". I'm told the worst thing you can do to a stuck ferrule is squirt WD 40 down it. Order new rod.

BTC

perttime03/07/2020 14:39:35
avatar
164 forum posts
11 photos

Posted by Chris Walby on 03/07/2020 12:46:43:

...

I have a cunning plan, ..

Gotta love cunning plans

Being cheap, I would have stuck with the dowel and sandpaper plans.

Whether carbon and epoxy particles are carsinogenous, or not, they are pretty nasty just mechanically. Better keep them away from your insides. I prefer to keep them from embedding themselves in my skin too.

Richard Clark 203/07/2020 15:28:21
424 forum posts
Posted by perttime on 03/07/2020 14:39:35:

Posted by Chris Walby on 03/07/2020 12:46:43:

...

I have a cunning plan, ..

Gotta love cunning plans

Being cheap, I would have stuck with the dowel and sandpaper plans.

Whether carbon and epoxy particles are carsinogenous, or not, they are pretty nasty just mechanically. Better keep them away from your insides. I prefer to keep them from embedding themselves in my skin too.

While a tube, carbon, brass, light alloy, or glass, is fine in the wings you should use a solid rod as the wing joiner. A tube joiner will flatten into an elliptical shape under strain which weakens it in the vertical plane. Thus weakened it flattens even more, weakens further, and eventually breaks.

Barrie Lever03/07/2020 16:26:59
avatar
271 forum posts
50 photos

Richard

Glad you pointed out the inadequacy of the tube.

I would like to add that the sequence you describe usually happens in a short period of time !!!

B.

Erfolg03/07/2020 16:56:00
avatar
11781 forum posts
1340 photos

A lot of +50cc Extra type models (that I see) use a single Carbon spar as a push fit through what appears to be light ply wing ribs, with no trouble.

On the other hand my HK Waco SRE had a aluminium inner wing tube, inside a Carbon outer. Much to my surprise the carbon tube shattered, leaving a wobbly wing. There was a lot more wrong with the model, but that is bye the bye. My repair just used an outer aluminium tube.

wp_20170315_14_16_12_pro.jpg

At the end of the day, there seems to be CF tube and then there is CF tube.

Many of my open gliders used either a GF or CF boom (fishing rod, deep sea type of size), which never broke without my arrivals. On that basis both materials can be great

On that note, I would just observe that like any other component or assembly, the material in itself is not always the answer, it is the detail of how it is used. Also I would be concerned about the potential binding/seizing issue raised.

Edited By Erfolg on 03/07/2020 16:56:58

Chris Walby03/07/2020 17:48:25
avatar
1277 forum posts
315 photos

Off topic again, and I can see your point about load points on the tubes RC2, but IMHO why do E-flight, Seagull, Black Horse, Chris Foss, Motion RC and Century all use wing tubes (either ali or carbon fibre)? These are models I know have wing tubes, in fact I can't think of any 6Kg models that use solid wing joiners.

I shall don the appropriate PPE and carefully remove the seam inside the wing tube (not using WD40) and try either candle wax or Teflon spray.

All Topics | Latest Posts

Please login to post a reply.

Latest Forum Posts
Support Our Partners
electricwingman 2017
Sussex Model Centre
CML
Slec
Sarik
Advertise With Us
Latest "For Sale" Ads
Has home isolation prompted you to start trad' building?
Q: The effects of Coronavirus

 Yes - for the first time
 Yes - but Ive bashed balsa before
 No - Ive existing projects on the bench
 No - Im strictly an ARTF person

Latest Reviews
Digital Back Issues

RCM&E Digital Back Issues

Contact us

Contact us

Magazine Locator

Want the latest issue of RCM&E? Use our magazine locator link to find your nearest stockist!

Find RCM&E!