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OT? Maybe not? Carbon Fiber construction

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  • OT? Maybe not? Carbon Fiber construction

    Maybe this is on topic, because it is building something...
    Been studying composite aircraft construction and various methods. I want to try my hand with Carbon Fiber sheet and making a plug of a Me262 fuselage in 1/6th scale. From there I will make a 2 part mould. From the mould, I will lay down sheets of Carbon fiber, wetted with resin. Before joining both halves together, will have an air bladder that I inflate once the two halves are bolted together. Will try to create a lap seem the bladder will press together, and should have an extra strong lightweight, cutting edge R/C me262.
    Does my description sound legitimate? The joining of the two halves is a subject I am having a hard time finding info on.

  • #2
    There were several companies that specialized in CF construction, materials, etc. at the AMA Expo show. They also were selling tons of different CF items like sheet, plate, thin strips, round tubes, square tubes, etc. Unfortunately, I didn't take any pictures of all of the CF stuff they were selling.

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    • #3
      Now we're getting into one of my other hobbies....

      Things to consider. By itself carbon cloth composite is stiffer than glass. So you can do more with less. But at the same time you need some minimum thickness to supply the stiffness needed to hold the shape correctly. And that comes down to stiffness of the materials and the distance between the material on the inside and outside of the layup. And in the case of a simple layup like this that filler that holds the surface fibers apart is more of the heavy layup of fibers and resin. Now by rights you can make the layup thinner with carbon and still get decent stiffness. But you can do "more with less" if you use a lighter layer on the outside, then add a segmented filler such as thin foam plastic then another inside layer of carbon and epoxy. The result being very stiff and even less weight.

      Otherwise with a single layup such as you're asking about you can be as stiff as fiberglass for less weight or you can be the same weight as fiberglass and be stronger and stiffer.

      One other factor to figure is that the receiver antenna(s) need to stick out or have a radio transparent hole such as a non carbon wing with the Rx just inside the wing. Carbon glider flyers have had significant issues with trying to use 2.4G receivers with the antennas inside carbon fuselages. Not sure if you've run across that or not in your reading travels.

      Most folks that join the fuselage halves just make two separate side shells. Then working through the wing opening and in this case the cockpit opening which will be reasonably large they use glass (or carbon) tape saturated in resin and rolled up. These rolls are then stuck over the inside of the seam and teased out along the joint with a push stick and then given a roll over against the outer shells with a cut down roller on a stick. And up through the leading edge of the fin a few patches are pushed into place and formed to the shape through the hinge line spar opening.

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      • #4
        Originally posted by 3 Phase Lightbulb View Post
        There were several companies that specialized in CF construction, materials, etc. at the AMA Expo show. They also were selling tons of different CF items like sheet, plate, thin strips, round tubes, square tubes, etc. Unfortunately, I didn't take any pictures of all of the CF stuff they were selling.
        Aircraft Spruce sells CF cloth for full size construction. Think the sheet is only .007" thick. Not expensive either. Think the resin is what costs the money.
        CF is becoming more popular. Only issue I can think about is placing the receiver antenna with an all CF airplane.

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        • #5
          Originally posted by BCRider View Post
          Now we're getting into one of my other hobbies....

          Things to consider. By itself carbon cloth composite is stiffer than glass. So you can do more with less. But at the same time you need some minimum thickness to supply the stiffness needed to hold the shape correctly. And that comes down to stiffness of the materials and the distance between the material on the inside and outside of the layup. And in the case of a simple layup like this that filler that holds the surface fibers apart is more of the heavy layup of fibers and resin. Now by rights you can make the layup thinner with carbon and still get decent stiffness. But you can do "more with less" if you use a lighter layer on the outside, then add a segmented filler such as thin foam plastic then another inside layer of carbon and epoxy. The result being very stiff and even less weight.

          Otherwise with a single layup such as you're asking about you can be as stiff as fiberglass for less weight or you can be the same weight as fiberglass and be stronger and stiffer.

          One other factor to figure is that the receiver antenna(s) need to stick out or have a radio transparent hole such as a non carbon wing with the Rx just inside the wing. Carbon glider flyers have had significant issues with trying to use 2.4G receivers with the antennas inside carbon fuselages. Not sure if you've run across that or not in your reading travels.

          Most folks that join the fuselage halves just make two separate side shells. Then working through the wing opening and in this case the cockpit opening which will be reasonably large they use glass (or carbon) tape saturated in resin and rolled up. These rolls are then stuck over the inside of the seam and teased out along the joint with a push stick and then given a roll over against the outer shells with a cut down roller on a stick. And up through the leading edge of the fin a few patches are pushed into place and formed to the shape through the hinge line spar opening.
          Thank you for describing the techniques, never disappointed by the knowledge on this forum.

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          • #6
            Originally posted by RB211 View Post
            Aircraft Spruce sells CF cloth for full size construction. Think the sheet is only .007" thick. Not expensive either. Think the resin is what costs the money.
            CF is becoming more popular. Only issue I can think about is placing the receiver antenna with an all CF airplane.
            Resin is the cheaper part unless you are doing something super exotic.
            Resin(epoxy) is around-ish 30usd per kg, thin carbon fiber cloth ~30usd per square meter and you need about 2x the fiber weight in resin.
            thin one like 0.007 CF is 6oz/square yard so you need maybbe 0.5kg of resin per square meter.

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            • #7
              Originally posted by MattiJ View Post
              Resin is the cheaper part unless you are doing something super exotic.
              Resin(epoxy) is around-ish 30usd per kg, thin carbon fiber cloth ~30usd per square meter and you need about 2x the fiber weight in resin.
              thin one like 0.007 CF is 6oz/square yard so you need maybbe 0.5kg of resin per square meter.
              It will be interesting once I get ready to try it. Just watched Burt Rutans video on working with Fiberglass. Just wish there was content like that for Carbon Fiber. Seen some PrePreg CF stuff but I don't want to use that.

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              • #8
                Much of what I've seen done in CF is for looks. That has to be a whole 'nuther learning experience. If it's being used for strength and lightness, then learn about the techniques that BCRider is talking about. We once made a canoe with internal ribbing to lend some stiffness, rather than the multiple layers of cloth and resin to achieve the same thing. Though this was done using glass cloth, the canoe weighed in at 25 lbs, rather than the 60 odd lbs that it was in the non-ribbed version. You could reach down below the level of the dock and pick it out of the water with one hand.

                My friend kept it and used it for years without incident- proof of the concept.

                I have very little experience with CF, but apparently it's similar to kevlar when it comes to wetting it out- more difficult to wet out and to see when you're there.
                I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                • #9
                  Originally posted by darryl View Post
                  Much of what I've seen done in CF is for looks. That has to be a whole 'nuther learning experience. If it's being used for strength and lightness, then learn about the techniques that BCRider is talking about. We once made a canoe with internal ribbing to lend some stiffness, rather than the multiple layers of cloth and resin to achieve the same thing. Though this was done using glass cloth, the canoe weighed in at 25 lbs, rather than the 60 odd lbs that it was in the non-ribbed version. You could reach down below the level of the dock and pick it out of the water with one hand.

                  My friend kept it and used it for years without incident- proof of the concept.

                  I have very little experience with CF, but apparently it's similar to kevlar when it comes to wetting it out- more difficult to wet out and to see when you're there.
                  I have a racing drone that I was flying and the flight controller went berserk, lost which way was up. It did a full power inverted dive straight into the ground. Was still in one piece, one or two broken props.
                  For strength, you use the same techniques as for fiberglass in regards to orientation of the threads.

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                  • #10
                    Originally posted by BCRider View Post
                    Now we're getting into one of my other hobbies....

                    Things to consider. By itself carbon cloth composite is stiffer than glass. So you can do more with less. But at the same time you need some minimum thickness to supply the stiffness needed to hold the shape correctly. And that comes down to stiffness of the materials and the distance between the material on the inside and outside of the layup. And in the case of a simple layup like this that filler that holds the surface fibers apart is more of the heavy layup of fibers and resin. Now by rights you can make the layup thinner with carbon and still get decent stiffness. But you can do "more with less" if you use a lighter layer on the outside, then add a segmented filler such as thin foam plastic then another inside layer of carbon and epoxy. The result being very stiff and even less weight.

                    Otherwise with a single layup such as you're asking about you can be as stiff as fiberglass for less weight or you can be the same weight as fiberglass and be stronger and stiffer.

                    One other factor to figure is that the receiver antenna(s) need to stick out or have a radio transparent hole such as a non carbon wing with the Rx just inside the wing. Carbon glider flyers have had significant issues with trying to use 2.4G receivers with the antennas inside carbon fuselages. Not sure if you've run across that or not in your reading travels.

                    Most folks that join the fuselage halves just make two separate side shells. Then working through the wing opening and in this case the cockpit opening which will be reasonably large they use glass (or carbon) tape saturated in resin and rolled up. These rolls are then stuck over the inside of the seam and teased out along the joint with a push stick and then given a roll over against the outer shells with a cut down roller on a stick. And up through the leading edge of the fin a few patches are pushed into place and formed to the shape through the hinge line spar opening.
                    Good info BC and yes I can attest to what you stated about the antenna wire going through carbon fiber - you will have to extend your wire well past the carbon as it insulates the signal,,,

                    Both of my foamies Iv built i used a carbon fiber arrow shaft for the fuselage and I had to learn the hard way after the bird was in the air lol

                    fortunately foam wrapped in packing tape makes for a very durable exoskeleton lol

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                    • #11
                      That's a good call on the resin and fiber compatibility for wetting out the cloth. Last thing you want is any dry spots.

                      Talk to the cloth and resin suppliers both about the proper cloth and resin to use. It's not all equal by a long shot.

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                      • #12
                        Originally posted by BCRider View Post
                        That's a good call on the resin and fiber compatibility for wetting out the cloth. Last thing you want is any dry spots.

                        Talk to the cloth and resin suppliers both about the proper cloth and resin to use. It's not all equal by a long shot.
                        A subject I know nothing about. None of the videos specified any resins. Think I will call Aircraft Spruce and maybe WestSystems.

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                        • #13
                          Here is a list of videos I compiled from YouTube to help educate myself with composite techniques.

                          Making Moulds

                          https://youtu.be/keBwRhkfuOQ

                          Pickings are much slimmer for using a mould for fiberglass and carbon fiber, and also mould-less.

                          Fiberglass
                          https://youtu.be/Ql5ruDn1VA8

                          Carbon Fiber
                          https://youtu.be/T4ZFj4fItWE

                          Mould-less ... Who else, other than Burt Rutan?
                          https://youtu.be/p9GTYsNBiaE

                          Making a Plug
                          https://youtu.be/qStFDcZs5Og

                          and

                          Last edited by RB211; 02-25-2019, 12:24 AM.

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