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Carbon fibre tube trusses

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bmcj

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The only serious attempt to use carbon fiber tubes to replace steel tubing in a truss fuselage that I know of is the Loudenslager Shark. It never flew. It can be seen at Oshkosh.



BJC
Wow! Those are some wildly articulated control surfaces. Has this plane flown yet? I’d love to see what that extreme surface movement does for it (to it?).


By the way, this is the thread I was looking for when I posted this about a carbon fiber tube Corsair (sorta) look-a-like:

 

BJC

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Wow! Those are some wildly articulated control surfaces. Has this plane flown yet? I’d love to see what that extreme surface movement does for it (to it?).
Leo died as the result of a motorcycle accident in 1997, and development ended. It never has flown. It was conceived to be light, have lots of HP, and lots of control power, especially at low airspeed (think tumbles, micro loops, rolls at zero airspeed). Sean Tucker’s rudder deflects +/-60 degrees and 4 of the 8 ailerons are in the prop blast.


BJC
 

litespeed

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The idea of a tube carbon fuse has merit esp if all designed in 3d cad first. That would allow the printing to be simpler after optimising the truss. Printed gusset moulds certainly have advantages.

The square tube would be the easiest to do and would also suit been clad in composite or carbon sheets. What about using the truss as a structural combination with the skin? Maybe even a scheme where it is a sandwich with tubes inside, foam in between open spaces and a skin on inside. That could be very strong and not excessive in weight. For the cockpit add a layer of kevlar on inside and back of firewall to stop accident ingress of nasty objects including the splinter effect of carbon.

Naturally that is for a closed fuselage and not really a affordaplane style.

Mike Patey has gone carbon skins to gain some rigidity but they are just bolt on thin skins, so may not be what he seeks in the end stiffness wise.

Sorry for the tangent but just thinking of ways to use it in different cases of structures.

If the addition of a few thousand in carbon tubes makes the best aircraft, I am for it. The cost of tube alloy in Oz is extortion.I love metal but will change for the best solution.

I know we all want fast to build, easy and cheap. sometimes its good to just get two of those.

I like the Corsair but not the price.
 

litespeed

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As a aside the gussets can be done without a printer.

Will suit some gussets better than others.

I say this as some designs might need lots of varied molds for all the gussets. That is a lot of print time. I don't mind too much - my son has two printers. And print time is free time in labor.

Printed gusset molds could even be done in pull apart fashion to allow them to be used to align and hold the truss and gusset when gluing. Could give a impressive looking joint and just pull off after drying. Using them twice to ensure a perfect alignment sounds like a good design point to provide builder confidence and consistent quality.

For outside joins you could have all the gussets flat- so just use simple flat plate carbon/carbon angle with the internal gusset doing all the shapes. The outer ones could just be as simple as alloy sheet bent. This would drop print time and give a nice outside for skinning/covering. Again square tubes, are easiest.

This then brings up the ability to either make the molds available to others on loan/rent/beers or make kit sets of the gussets for fast build. Ideally all the molds are ganged together so are made on one large layup, much faster, easier and cheaper. Then all needed gussets and other small bits can be made in a day, bagged and let set with a diy oven possible for cure.


Which then leads to the logical path of such molds......
If we have it all cnc designed anyway, why not use a high density XPS foam- which is very cheap and cnc carve out the molds in one big thick sheet or series of smaller sheets.

The machine could be a very simple DIY 3d router, cheap and a lot faster by days in machine time. A light sand and a lovely cheap mold set. Spray on PVA after your favourite sauce and sweet to use. It could even have a thin plastic sheet/film vacuumed on top. If we have a vacuum setup why not?

This would make molds that are very quick, light but strong enough and cheap in materials. A small 4' by 4' sized 3d (even smaller could do) router is plenty and would allow much faster prototyping.
Can be changed to do wire cutting as well for wing profiles or ribs etc.

I like the printer idea, but think for overall speed and cost the router is better esp for folks that have not bought a printer or router yet. Having both would be even better, for the bits a printer is best at. Adapting a printer head and feeder to do much bigger stuff on the router 3d/4d machine has been done. Then best of both worlds in a small space.

Just my ramblings on the idea, the beers cold, I need a distraction. Sydney is flanked by fire in the north and the sky is red. High winds and the fires just keep making their own weather. All the smoke has made the sunlight a red glow. Yesterday I drove north 200kms, it was like Mars had parked itself next door and we now orbit much closer to the hell.

Makes sailing the ocean a real good idea.
 

Victor Bravo

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Printed gusset molds could even be done in pull apart fashion to allow them to be used to align and hold the truss and gusset when gluing. Could give a impressive looking joint and just pull off after drying. Using them twice to ensure a perfect alignment sounds like a good design point to provide builder confidence and consistent quality.
That's pretty clever, excellent idea.
 

litespeed

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Thanks VB,

Occasionally the brain cells hit each other in my black box brain.
 

AdrianS

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How about square tube, flat gussets, and foam wedges that fit between tube and gusset, and help locate the tube?

3d needs a bit more thought, but you could glue the tubes together with the foam spacers, then drape cloth over the joint.
 

Geraldc

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I have been pricing square carbon tube and it is over twice the price of 4130 tube.

For a flat panel you could make an outside carbon or glass skin on a layer of something it won't stick to.

On top of that a mesh made of strips of pvc foam in whatever pattern suits. Then cover with another layer of cloth

draped into gaps in foam then vacuum bag.This way the tubes are formed and gaps between filled all in one operation.


upload_2019-12-7_8-28-21.png
 

BoKu

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...For a flat panel you could make an outside carbon or glass skin on a layer of something it won't stick to.

On top of that a mesh made of strips of pvc foam in whatever pattern suits. Then cover with another layer of cloth

draped into gaps in foam then vacuum bag.This way the tubes are formed and gaps between filled all in one operation.
You're almost there! Say you use a piece of waxed 1/8" masonite for your molding surface. Say you curve it slightly by supporting it on arched cradles. Now you can make a fuselage side (or maybe even a wing skin), and you don't need those troublesome bulkheads and stringers. Also, since you have created a continuous web, if you use at least one ply of +/-45 cloth, you no longer need diagonal stiffeners.

As an additional measure, if you put down some 0.05" or so thick strips of tooling wax or aluminum or whatever is handy along the edges of the panel, when you demold the panel you have a joggle where you can put shear tapes that join it to the next panel over.

Wow, these carbon fiber tube trusses are fun when you leave out the "tube" and "truss" parts! :)
 

cheapracer

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I have been pricing square carbon tube and it is over twice the price of 4130 tube.

For a flat panel you could make an outside carbon or glass skin on a layer of something it won't stick to.

On top of that a mesh made of strips of pvc foam in whatever pattern suits. Then cover with another layer of cloth

draped into gaps in foam then vacuum bag.This way the tubes are formed and gaps between filled all in one operation.


View attachment 90995
I actually can't quite remember the exact process I was trying to achieve here.

Think I was trying to make an inner skin mold maybe. Laser cut the steel to shape, 3 lengths of 1" square tube riveted on, and 1" foam cut into strips for the braces.

Like that basketball that kept getting bigger and bigger, it will hit me eventually ...

layup 2.jpg

layup.jpg




Hmm, my 'Lens" layout was my best, but I had a good reason not to follow up on it, and now I have resolved that reason while working on my current plane ... oh well, next plane!
 
Last edited:

Armilite

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As cool as Carbon fiber is, for a Tube/Truss Type Airframe I just don't see the need for it since it Cost probably 5x the Cost per foot of Steel Tube and probably 4x the Cost of 6061. First, you would have to figure the equivalent strength-wise of the most commonly used Sizes of 6061.

Most Common 6061 Tube Sizes used.

1" OD x 0.058" Wall x 0.884" ID Aluminum Round Tube 6061-T6-Drawn. 1ft = $7.68 Weight 0.2020 lbs.

1" OD x 0.065" Wall x 0.87" ID Aluminum Round Tube 6061-T6-Drawn. 1ft = $7.43 Weight 0.2247 lbs.

1.25" OD x 0.065" Wall x 1.12" ID Aluminum Round Tube 6061-T6-Drawn. 1ft = $10.30 Weight 0.2847 lbs.

1.5" OD x 0.065" Wall x 1.37" ID Aluminum Round Tube 6061-T6-Drawn. 1ft = $11.89 Weight 0.3448 lbs.

2" OD x 0.065" Wall x 1.87" ID Aluminum Round Tube 6061-T6-Drawn. 1ft = $15.05 Weight 0.4650 lbs.

2" OD x 0.083" Wall x 1.834" ID Aluminum Round Tube 6061-T6-Drawn. 1ft = $20.42 Weight 0.5882 lbs.

2.25" OD x 0.065" Wall x 2.12" ID Aluminum Round Tube 6061-T6-Drawn. 1ft = $22.59 Weight 0.5251 lbs.
 

delta

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I've been experimenting with joining CF golf club shafts with tow and superglue in the hopes that someday the 1000+ shafts I impulsively bought could somehow be transformed into a magnificent flying vehicle. Still working on it, but haven't mustered the necessary courage to pull the trigger yet. Two of the latest involve nine out-runner 72" models joined to each other and a fuselage containing me and a genset. tt1a1.JPG tt1a2.JPG tt1c1.JPG tt1c2.JPG
 

lr27

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As I recall, some human powered aircraft projects used aluminum tubes joined with Kevlar tow wrapped around them. I don't remember the details.
I think the record setting human powered helicopter is made with carbon trusses, but I don't know how they're joined.
 

wsimpso1

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First thing I have to say is maybe you should pick up a Tailwind or Pitts raw fuselage sometime. Its lack of weight will startle you. That is the benchmark.

I know that you can make an airworthy structure from graphite tubes and wraps... I am skeptical that it will make a lighter airplane than could be made a couple of different ways. The engineering analysis to prove to yourself that it is strong enough while being light enough to justify the cost and man-hours is a whole 'nother level.

Let's talk details. In a fuselage truss, we must use truss theory on any one set of vertices to find the worst case loads in each element and in each joint, then size the tubes and joints to the loads. You not only have to include the positive and negative g flight loads but the FAR Part 23 crash loads for the cockpit is a pretty good idea too. Then you have to figure out everything that is mounted to the truss - everything from engine and wings and seats down to controls and battery box and wiring. Then there are the loads from fabric covering shrunk on. The defining case for the tubes is usually long form buckling (Euler), which drives us to thinnest wall, enough diameter, frequently with some bending and torsional strength too. Then joints have to be checked to make sure they will stay put too.

In steel tubes, we have many tube diameter and many wall thickness to choose the lightest tube for each element. In aluminum, we have less wall thicknesses to choose from, but quite a few.

In Commercial Off The Shelf graphite fiber tubes, there seem to be many diameter, but walls are usually thicker than needed. The ideal tube for this sort of use will be pretty thin wall and braided at small angles to the long axis of the tube. You start with COTS tubes that are PRICEY and perhaps heavier than desired, and then get to consider building or commissioning specific tubes at even more money. In the end you add up all the weights of the tubes, joints, reinforcements, and covering on each option and get an estimate on the weight, cost, and man hours so you can compare the various schemes.

Now let's look at a molded composite fuselage. The shell away from the wing, cockpit and engine can be very light indeed, maybe 2 plies of 6 oz outside and 1 or 2 plies inside a core, or maybe just 3 plies uncored, with substantial laminations added where needed. This can all be laid up in two molds and assembled by gluing them together. Yeah, the mold will require some investment, but so will the fuselage jig you will need for most tube type fuselages.

I know you will have way more money and man-hours in the carbon fiber tube truss than in the metal tube truss or molded shell. I suspect that you will have more weight too, but that will be on a design by design basis. Other knowledgeable folks have come to the same conclusions. See BoKu's post above... Who knows, maybe you will hit a sweet spot where a carbon tube truss is the lightest way to get there. But do your homework to make sure before you build a labor intensive and expensive fuselage that also turns out to be heavy.

Billski
 

Armilite

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I've been experimenting with joining CF golf club shafts with tow and superglue in the hopes that someday the 1000+ shafts I impulsively bought could somehow be transformed into a magnificent flying vehicle. Still working on it, but haven't mustered the necessary courage to pull the trigger yet. Two of the latest involve nine out-runner 72" models joined to each other and a fuselage containing me and a genset. View attachment 94164 View attachment 94165 View attachment 94166 View attachment 94167
======================================
With over 750+ Designs out there Flying to pick from, most are either Tube & Fabric, or Wood & Fabric, or Foam & Fiberglass or Carbon Fiber, and some all Aluminum. Electric for USA Part 103 just isn't feasible since battery Weight is part of the 254lbs. Probably only 35-45min Flight Time Tops. A Slick airplane like the Quickey (Q1) used 18hp. With these 3D Printers and 20+ Materials out on the Market, you will soon be able to 3D Print a Small Plane. You can do Small parts now.

Now if it made with Carbon Fiber vs Fiberglass you could save Weight.
You Electic Motor is lighter than the Onan to Save Weight.
With a Carbon Fiber Spar you save Weight and Gain some strength to maybe raise the MTOW of 485 lbs. Today you have Carbon Fiber Props, lighter Wheels, etc.

If you can't meet the Performace with a Gas Engine, most People won't Buy it either

Specifications (Onan engine) Plans built Foam & Fiberglass.

General characteristics
Crew:
one pilot
  • Capacity: 20 lb (9.1 kg) luggage and 240 lb (108 kg) useful load
  • Length: 17 ft 4 in (5.28 m)
  • Wingspan: 16 ft 8 in (5.08 m)
  • Height: 4 ft 5 in (1.35 m)
  • Wing area: 53.8 sq ft (5.00 m2)
  • Empty weight: 245 lb (111 kg)
  • Max takeoff weight: 485 lb (220 kg)
  • Useful Load: 240 lbs
  • Powerplant: 1 × Onan opposed four-stroke piston engine, 18 hp (13 kW) at 3,600 rpm
Performance

  • Maximum speed: 126 mph (203 km/h, 109 kn)
  • Cruise speed: 115 mph (185 km/h, 100 kn)
  • Stall speed: 47 mph (76 km/h, 41 kn)
  • Range: 570 mi (920 km, 500 nmi)
  • Rate of climb: 420 ft/min (2.1 m/s)
Quickey Q1.jpg
Quickey Q1.jpg3D PRINTED PARTS 29.jpg3D PRINTED PARTS 28.jpg
 

TLAR

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Sep 29, 2020
Messages
59
======================================
With over 750+ Designs out there Flying to pick from, most are either Tube & Fabric, or Wood & Fabric, or Foam & Fiberglass or Carbon Fiber, and some all Aluminum. Electric for USA Part 103 just isn't feasible since battery Weight is part of the 254lbs. Probably only 35-45min Flight Time Tops. A Slick airplane like the Quickey (Q1) used 18hp. With these 3D Printers and 20+ Materials out on the Market, you will soon be able to 3D Print a Small Plane. You can do Small parts now.

Now if it made with Carbon Fiber vs Fiberglass you could save Weight.
You Electic Motor is lighter than the Onan to Save Weight.
With a Carbon Fiber Spar you save Weight and Gain some strength to maybe raise the MTOW of 485 lbs. Today you have Carbon Fiber Props, lighter Wheels, etc.

If you can't meet the Performace with a Gas Engine, most People won't Buy it either

Specifications (Onan engine) Plans built Foam & Fiberglass.

General characteristics
Crew:
one pilot
  • Capacity: 20 lb (9.1 kg) luggage and 240 lb (108 kg) useful load
  • Length: 17 ft 4 in (5.28 m)
  • Wingspan: 16 ft 8 in (5.08 m)
  • Height: 4 ft 5 in (1.35 m)
  • Wing area: 53.8 sq ft (5.00 m2)
  • Empty weight: 245 lb (111 kg)
  • Max takeoff weight: 485 lb (220 kg)
  • Useful Load: 240 lbs
  • Powerplant: 1 × Onan opposed four-stroke piston engine, 18 hp (13 kW) at 3,600 rpm
Performance

  • Maximum speed: 126 mph (203 km/h, 109 kn)
  • Cruise speed: 115 mph (185 km/h, 100 kn)
  • Stall speed: 47 mph (76 km/h, 41 kn)
  • Range: 570 mi (920 km, 500 nmi)
  • Rate of climb: 420 ft/min (2.1 m/s)
View attachment 103945
View attachment 103945View attachment 103946View attachment 103947
Thanks Arm for the nice link!!
That is a very efficient aircraft!!
 
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