Preferred Wing Tube/Sleeve
01-22-2019, 03:40 PM
#3
For jets, I would not use a carbon tube. I would use a carbon (or "ceramic") rod if the wings are short, but I'd stick with some type of aluminum tube or blade spar if the wings are longer.
The main issue with a carbon tube is that it can fail catastrophically if its over stressed or damaged. An aluminum tube will generally bend before it breaks - e.g., from a hard landing, and it can then be replaced...
Bob
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bull_plane98 (07-19-2021)
01-22-2019, 06:46 PM
#6
I can speak from direct experience, Last September I went to put my lightning together to fly, and as I was putting the wings on noticed a gap, that was never there, removed the wing and wing tube, and checked it, the wing tube had a large bend in it. I was able to get a new tube for the jet and all is well. HOWEVER, thinking about the bent tube, it must have had some force on it to bend, I'm sure I was probably going to fast, and pulling too hard. I cant help but be grateful for the aluminum tube bending, and giving me the opportunity to find the problem. If the tube had been carbon fiber, it would NOT have bent, it would have broken, and that would have been instant disaster for my Jet. So my personal opinion is aluminum.
01-24-2019, 05:36 AM
#8
The Airbus A350 and B 787 ( and the later Harriers had all composite wings). use carbon composites in over 50 % of primary structure including the wing boxes, the structural heart of the aircraft. Even the GE NX engines are using composite fan blades.
But dont take my word for it, take a look at the Boeing and Airbus ( and Mitsubishi who make the composite wing box for Boeing) websites to see just how extensive is their use of composites and the advantages conferred.
Last edited by David Gladwin; 01-24-2019 at 05:39 AM.
01-24-2019, 06:19 AM
#9
Carbon is perfectly suited for wing tubes or rods, arguably the best you can use, so long as wall thickness and diameter gives the required strength, which should exceed that of the structure to which it is attached.
The Airbus A350 and B 787 ( and the later Harriers had all composite wings). use carbon composites in over 50 % of primary structure including the wing boxes, the structural heart of the aircraft. Even the GE NX engines are using composite fan blades.
But dont take my word for it, take a look at the Boeing and Airbus ( and Mitsubishi who make the composite wing box for Boeing) websites to see just how extensive is their use of composites and the advantages conferred.
As usual, you're trying to apply full scale methods/techniques to model jets - which often isn't appropriate.
Boeing and Airbus have spent millions (billions of taxpayer dollars in the case of Airbus) designing the composite structures for full-scale aircraft based on detailed engineering analysis.
This of course is not the case for 99% of model jets, so unless that has been done and and its been verified by analysis and testing that the tube is strong enough for ALL anticipated loads, a metal tube, that will deform before breaking, is a better solution.
BTW, we all know that composites are used extensively in modern full-scale aircraft, you're not telling us something that we didn't already know...
Bob
Last edited by rhklenke; 01-24-2019 at 06:22 AM.
01-24-2019, 07:05 AM
#10
..and VERY, VERY, often is, an aeroplane is an aeroplane, only the numbers differ !
as you say, B and A have spent billions on composite research. I am more than happy to accept their findings.
The last thing I want is a tube to deform when a composite tube will not fail until the load is far greater than that which caused deformation of the tube. Personally never had a tube to deform or a cf tube to break !
The only reason for using alu tube as against CF is cost, alu is cheaper.
Rather follow the lead from the professional aerospace industry than the “ experts” on these forums.
.... and please don,t start on Airbus funding, Boeing, too, have received massive government funding from overpriced military contracts.
as you say, B and A have spent billions on composite research. I am more than happy to accept their findings.
The last thing I want is a tube to deform when a composite tube will not fail until the load is far greater than that which caused deformation of the tube. Personally never had a tube to deform or a cf tube to break !
The only reason for using alu tube as against CF is cost, alu is cheaper.
Rather follow the lead from the professional aerospace industry than the “ experts” on these forums.
.... and please don,t start on Airbus funding, Boeing, too, have received massive government funding from overpriced military contracts.
Last edited by David Gladwin; 01-24-2019 at 08:06 AM.
01-24-2019, 08:05 AM
#11
..and VERY, VERY, often is.
as you say, B and A have spent billions on composite research. I am more than happy to accept their findings.
The last thing I want is a tube to deform when a composite tube will not fail until the load is far greater than that which caused deformation of the tube. Personally never had a tube to deform or a cf tube to break !
The only reason for using alu tube as against CF is cost, alu is cheaper.
Rather follow the lead from the professional aerospace industry than the “ experts” on these forums.
.... and please dont start on Airbus funding, Boeing, too, have received massiv government funding from overpriced military contracts.
as you say, B and A have spent billions on composite research. I am more than happy to accept their findings.
The last thing I want is a tube to deform when a composite tube will not fail until the load is far greater than that which caused deformation of the tube. Personally never had a tube to deform or a cf tube to break !
The only reason for using alu tube as against CF is cost, alu is cheaper.
Rather follow the lead from the professional aerospace industry than the “ experts” on these forums.
.... and please dont start on Airbus funding, Boeing, too, have received massiv government funding from overpriced military contracts.
I have one jet (F-4) that has carbon ROD wing spars, and another (Eurosport) that has ceramic ROD wing spars. I have never had, nor seen, a jet model that used carbon tube. If I happened to buy one, I'd expect that the designer/manufacturer had at least tested it to be sure that it was strong enough for the job (not a great assumption in the case of some specific jet model manufacturers).
If I was scratch building or designing a jet as the original poster asked about, I would not use a carbon tube because I don't have access to that type of design and analysis capabilities - therefore, an aluminum tube is a safer bet.
Bob
ps. EADS has over-priced military contracts too - in addition to their direct government subsidies (Boeing: Facts About Subsidies to Airbus) The A380, which is a flash in the pan, would never have been built without them (http://www.traveller.com.au/air-fran...erjumbo-h18qoj).
Last edited by rhklenke; 01-24-2019 at 08:07 AM.
01-24-2019, 08:11 AM
#13
You might not, others might, cost again.
I tested my Blanik wings carbon tubes to over 10 g before turbine conversion, no problem.
Real world data, so much better than speculation, guestimation and hearsay.
I rest my case.
I tested my Blanik wings carbon tubes to over 10 g before turbine conversion, no problem.
Real world data, so much better than speculation, guestimation and hearsay.
I rest my case.
01-24-2019, 09:06 AM
#15
Jtec sells them with matching sleeves (www.jtecrc.com)
CST also sells them with matching sleeves (Carbon Fiber Tubes with Fiberglass Sleeves | Page 1 of 1)
The question is, how big, with what wall thickness, and what type of extrusion/materials do you need for your application? I don't know. David knows a lot of stuff, maybe he can tell you...
Bob
01-24-2019, 09:26 AM
#16
RTFQ !
I tested the tubes not the wings !
If yo, or anyone else, does not understand the relative properies of these materials take a look at: www.dexcraft.com.
Last edited by David Gladwin; 01-24-2019 at 09:40 AM.
01-24-2019, 09:59 AM
#17
While I haven't had to do much in the world of composites, through years of flying pattern, jets, working on custom cars and bikes, machining etc, I have to agree with both sides.
personally I would prefer carbon. Given the correct diameter and wall thickness carbon is more than up to the task. In pattern with gear in the wings, big vibrating 4 strokes and violent snaps and pulls (the figure z comes to mind]) after competing for 8 years I saw a few aluminum tube failures but never a carbon tube failure granted there were many more aluminum tubes than carbon ones but even in bad crashes I never saw a carbon tube break. As in all situations if you use a piece too small for the job it will fail.
most lean towards aluminum because it is cheap, easy to work with and it's been used for years. We can say "oh the blah blah blah just used that size, it should be fine. Honestly much of what we do is guesswork based on prior experience.
the tube, no matter whether aluminum or carbon or even steel, should never be a concern of the failure point. That piece should always be designed to be stronger than the structure supporting it. In other words no matter what the material it should be the last part to fail.
personally I would prefer carbon. Given the correct diameter and wall thickness carbon is more than up to the task. In pattern with gear in the wings, big vibrating 4 strokes and violent snaps and pulls (the figure z comes to mind]) after competing for 8 years I saw a few aluminum tube failures but never a carbon tube failure granted there were many more aluminum tubes than carbon ones but even in bad crashes I never saw a carbon tube break. As in all situations if you use a piece too small for the job it will fail.
most lean towards aluminum because it is cheap, easy to work with and it's been used for years. We can say "oh the blah blah blah just used that size, it should be fine. Honestly much of what we do is guesswork based on prior experience.
the tube, no matter whether aluminum or carbon or even steel, should never be a concern of the failure point. That piece should always be designed to be stronger than the structure supporting it. In other words no matter what the material it should be the last part to fail.
01-24-2019, 10:51 AM
#19
While I haven't had to do much in the world of composites, through years of flying pattern, jets, working on custom cars and bikes, machining etc, I have to agree with both sides.
personally I would prefer carbon. Given the correct diameter and wall thickness carbon is more than up to the task. In pattern with gear in the wings, big vibrating 4 strokes and violent snaps and pulls (the figure z comes to mind]) after competing for 8 years I saw a few aluminum tube failures but never a carbon tube failure granted there were many more aluminum tubes than carbon ones but even in bad crashes I never saw a carbon tube break. As in all situations if you use a piece too small for the job it will fail.
most lean towards aluminum because it is cheap, easy to work with and it's been used for years. We can say "oh the blah blah blah just used that size, it should be fine. Honestly much of what we do is guesswork based on prior experience.
the tube, no matter whether aluminum or carbon or even steel, should never be a concern of the failure point. That piece should always be designed to be stronger than the structure supporting it. In other words no matter what the material it should be the last part to fail.
personally I would prefer carbon. Given the correct diameter and wall thickness carbon is more than up to the task. In pattern with gear in the wings, big vibrating 4 strokes and violent snaps and pulls (the figure z comes to mind]) after competing for 8 years I saw a few aluminum tube failures but never a carbon tube failure granted there were many more aluminum tubes than carbon ones but even in bad crashes I never saw a carbon tube break. As in all situations if you use a piece too small for the job it will fail.
most lean towards aluminum because it is cheap, easy to work with and it's been used for years. We can say "oh the blah blah blah just used that size, it should be fine. Honestly much of what we do is guesswork based on prior experience.
the tube, no matter whether aluminum or carbon or even steel, should never be a concern of the failure point. That piece should always be designed to be stronger than the structure supporting it. In other words no matter what the material it should be the last part to fail.
If I'm doing a 40% 3D airplane, or a sailplane, I can look at the myriad number of those that are out there and select a similar carbon tube. For a jet, not so much. You say that you have an F15 and F18 with carbon tubes, and I believe you, but I honestly can't recall ever seeing one myself. The companies out there that sell carbon tubes (and sleeves) for model aircraft sell ones that are intended for the 3D and/or sailplane market, not jets.
We did some work with carbon fiber tubes for a VTOL UAV. It took some looking to find tubes that were readily available and of the right OD and ID. Once we did, we didn't really have any information on their ultimate strength to see if they were up to the job. We resorted to testing one of them to destruction in order to make sure. Not really a viable option for the average modeler with a limited budget.
Now for an aluminum tube, I can look at almost any of my jets and get an idea of what tube I need for that application. I have done that successfully several times when scratch building or modifying jet models.
Bottom line is that what Boeing or Airbus uses for their wing boxes has no bearing on selecting a wing tube of a model jet...
Bob
Last edited by rhklenke; 01-24-2019 at 10:56 AM.
01-24-2019, 11:47 AM
#20
If I'm doing a 40% 3D airplane, or a sailplane, I can look at the myriad number of those that are out there and select a similar carbon tube. For a jet, not so much. You say that you have an F15 and F18 with carbon tubes, and I believe you, but I honestly can't recall ever seeing one myself.
01-24-2019, 12:44 PM
#21
But couldn't you look at those jets and determine that they all have success with aluminum tubes of x diameter and y wall thickness, thus a carbon tube rating for a similar strength will suffice? Or go with the same diameter and wall thickness and get tons more strength for the same dimensions?
We also built a 14' WS large UAV which used a tube wing spar and tube tail booms. We considered carbon fiber, especially for the tail booms, but, we couldn't find much publicly available information on strengths, etc., so we went with aluminum tubes, a TLAR design principal, and some proof loading. Again we figured that we've get some bending first if we were too close to the limit (we didn't) instead of a catastrophic failure.
Bob
01-24-2019, 01:05 PM
#22
as for testing, if you are scratchbuilding a model you are going to put a 2k + turbine in, I would have zero issue spending the 20 bucks and aluminum tube is going to cost to test as a baseline and then buy a $50 carbon tube to destroy and compare. If you spend a couple hundred bucks on wing tubes for piece of mind on a 4k or more model who cares. It's not hard to test to destruction. As much as I hate to sometimes say it, all the calculations in the world dont work much better than the TLAR method (that looks about right). We put a ton of faith in hollow composite wings that have a thin foam core and you cant see any internal structure.
I have destroyed more items than I care to admit by trying to determine if its up to the task or not. The other thing I have done many times if I am concerned a tube may be not quite strong enough is put a dowel into it where the wing meets the fuse. Usually about 4" long. A hardwood dowel that size weighs very little and what it mostly does is makes it so the tube cannot collapse on itself.
01-24-2019, 04:32 PM
#23
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Since I'm a composite fabricator of over 30 years of experience building large UAV's ( up to 1400lbs) and jets and I have built planes with carbon tubes as large as 5" in diameter. I would lean towards the aluminum tubes for serveral reasons all of which Bob K has pointed out. The main reason is that the designer Kerry Sterner has done the engineering for his plans and I know him personally and have built several of his planes all of which use aluminum tubes. That being said there is nothing wrong with carbon tubes , but they can be rolled wrapped style or pultrusions and those vary greatly in bending and shear strengths. Unless you know exactly what you are buying or you can or have someone do the load analysis you could be on the hairy edge of failures just waiting for it to happen. Just this week I flamed a tube we bought at work from a composite supplier to see what the ply schedule was, low and behold there was just one 0-90 ply on the outside and four uni plys at +/-45 degrees under it with 2 length long uni plys drilling through the tube caused it to splinter internally so we are moving to a different style layup.
01-25-2019, 02:46 AM
#25
I think it depends on the application. A carbon tube is OK for giant scale 3D planes where weight is a primary consideration and generally, the structure of the rest of the plane is more fragile than the tube itself.
For jets, I would not use a carbon tube. I would use a carbon (or "ceramic") rod if the wings are short, but I'd stick with some type of aluminum tube or blade spar if the wings are longer.
Bob
For jets, I would not use a carbon tube. I would use a carbon (or "ceramic") rod if the wings are short, but I'd stick with some type of aluminum tube or blade spar if the wings are longer.
Bob
What matters is the wing bending moment of the wing concerned, jet, 3 d or glider.
Consider:
My PST Reaction, 2m wingspan, 10 kg mass. Stall about 40 mph.
And my Eflite Blanik, 4 m wingspan 10 kg mass. Stall about 20 mph. ( which has a carbon tube wing joiner)
Fly the Revision at 3 x vs, say 120 mph, theoretical max G =9
Fly the Blanik at Vs x3 say, 60 mph, max G = 9
Both semi spans are producing 45 Kg of lift at 9 G.
The center of lift of the Reaction wing is .5 m (ignoring taper) x45 kg = 22.5 kg/ m of bending moment.
The center of lift of the Blanik is at 1 m ( ignoring taper) x 45 kg= 45 kg.
So the wing bending moment, which IS what the tube has to carry is TWICE as high on the slow flying, large span glider than on the short span fast jet, so the glider tube needs to be twice as strong !
On the VC 10 airliner wing bending relief ( at weights above 132 t) was created by upsetting both ailerons by 10 degrees, reducing lift on the outer wing sections, therefore moving the center of lift inboard and reducing the wing bending moments, reducing stress and fatigue on the wing roots and center box structure.
Interestingly no one mentions the difference between pultruded and cross weave carbon fibre tubes.