I created a folder under my name to put photos in. There are some images of the Pitts Model 12 fuselage frame. Curtis Pitts designs have been around for decades and are extremely strong and simple. The M12 ultimate g load is + - 13. 9 g normal use.
Here's the link.
groups.yahoo.com/group/Carbondragonbuild...m/212271473/pic/list
It is amazing how you can take a box truss frame and make it look so good.
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This email address is being protected from spambots. You need JavaScript enabled to view it., Edward Pickens
wrote:
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> Kenny,
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> I own a K-6. The company has been supportive with plans in the past when I was doing repairs. They may even be willing to give us as hand if we ask nicely.Â
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> I believe the reason their sleeves are at the 45 is so that they will pull tight over any surface like a Chinese finger trap. They don't appear to be designed just for tubes. The unidirectional tape would not grab a surface like that. You can purchase pre-made uni directional tube, but it is very expensive.  There would be no savings buying their premade stuff. If you can get good results with wrapping a wide uni tape or cloth, then you may have something.  Â
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> When they were designing the Gossamer Albatross they made a hollow carbon spar. The reason they did not make a foam core is the same reason why we would not want a foam cored wing. The weight. They experimented with stuffing the foam disks down the tube to increase bending load without that much of a weight penalty. It worked. Take a paper towel roll and place some corrugated cardboard inside. Then try to bend. The addition of just a little weight makes a big difference. Because we are wrapping the material around a known dimension it will not be hard to slide the disks down the tube. It will even be polished smooth inside as that is the part against the mould. All you need is a rod with the spacing marked off and you know how far to push each disk.
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> I spent a lot on time considering how I would join the truss members. This is what I came up with.Â
> Imagine the fuselage already tack glued together at each joint. Now we need to add gussets for strength at the point of intersection of the tubes. For this example we will consider a simple case where a horizontal tube meets perpendicular to a longeron and then a perpendicular vertical tube descends from the longeron. This is what we will gusset
> Take to metal plates (.032 or so) and cover them with shrink/heat shrink wrap for a mould release as marske suggests. Butt these two plats against each other.
> Cut out your gusset from CF cloth. Wet it onto the metal plates with the center of the gusset where the 2 plates meet.
> Take the plates and lay the CF face onto the tube. Then clamp the plate to the tube with 2 clamps on the longeron and one on the horizontal.
> Next naturally lay the fabric onto the longeron as you rotate the second plate onto the vertical. Clamp as before.
> From the inside lay tape across the tubes onto the gusset to capture the structure from both sides.
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> The clamps I would use have an offset to allow the tapes underneath to be applies while the gusset is still wet. I would design them to grab the tube in one area from both sides and then have a spring loaded arm to hold the gusset tight against the surface.Â
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> Well, that's it for tonight. Thoughts? -Ed 