Carbon Fiber Tube Fuselage

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wsimpso1

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A cluster or node is easily constructed out of carbon fiber with the introduction of the simple PIN JOINT. Totally changes the node into a much simpler fiber path.
With carbon fiber you gotta think outside the box, and this method requires the introduction of alum or 4130.
you could disassemble the fuselage and make changes as each tube is connected with the pins
Back to metal ends on composite tubes, and now you have clearance at each pin in a hole.

First issue is that hard points always add a bunch of weight to composite structures - with this scheme it is the metal connections at both ends of every tube. That is why we generally work to avoid hard points, not put in dozens of 'em.

Second issue is all the slack that will be built into the airplane everytime there is a reversal of roll or pitch loading. It will sound like train changing direction but fast. A cascade of clunks. This effect might not be too bad if the longerons are solid, but still, all of those uprights and cross pieces and diagonals crashing back and forth through the lash in the system.

That was part of why so many early fuselages were wood and wires and turnbuckles.

Now, none of this is to say that it cannot work, just that it might be heavy and have some odd control tesponses.

Billski
 

Victor Bravo

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Once again, can you explain how you plan on making a proper engineering pin joint (and structural node) at a cluster where several tubes come together from different directions and on different planes?

Regardless of what material is used in the tubes.
 

BBerson

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The struts could be made by winding the carbon tow around the pin end bushings in a jig. Something like the pin end prop blades are made. The connector nodes would be wound around in a jig also with matching node bushings.
This might require a CNC to make the jigs.
 

TLAR

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The struts could be made by winding the carbon tow around the pin end bushings in a jig. Something like the pin end prop blades are made. The connector nodes would be wound around in a jig also with matching node bushings.
This might require a CNC to make the jigs.

That would work well
There is a simpler way without the need for tooling
 

TFF

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There is some off the shelf parts for pin joints. Nothing I would call aviation. I think the stuff is for building camera booms.
 

Tom Nalevanko

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The struts could be made by winding the carbon tow around the pin end bushings in a jig. Something like the pin end prop blades are made. The connector nodes would be wound around in a jig also with matching node bushings.
This might require a CNC to make the jigs.
Once upon a time I contributed to a thread here re a Polish engineer/builder of an ice-sail boat that joined aluminum tubes with fiberglass roving. Did multi-member joints. Very professional and effective but bulky and not elegant looking. Maybe the search function will bring it up?

Best,

Tom
 

BBerson

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joined aluminum tubes with fiberglass roving.
I was talking about making the entire strut with carbon or fiberglass roving by stringing the roving from end to end around fixed bushings. The tube core (mold) could be 1" foam. The one piece roving would wrap at about +60°and -60° to make a geodetic tube with end bushings molded in for bolts.
 
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Aviator168

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The carbon tube corsair claims to be part 103 compliant, yet it is over weight by a few lbs. Whereas the steel tube Badland is under #254. So at least in this case, the carbon tube didn't have a weight advantage. However, the corsair does have a much heavier 4 stroke engine; at 37kg, the engine on the crosair is almost twice as heavy as the one on the Badland.

Sounds like lots of work. Good luck.
Actually, it is quite easy. I have done it with balsa as the core material.
 
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berridos

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Winding with roving is what fischerman use on carbonrods and its easy and fast. I would say it takes less time than welding. Some sort of combs that are left in the joint and afterwards the pins are sanded off, would make life easier in order to match the 45-60º winding. With good gloves and a prewetting device it would make for a fun project.
 

Vigilant1

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Winding with roving is what fischerman use on carbonrods and its easy and fast. I would say it takes less time than welding. Some sort of combs that are left in the joint and afterwards the pins are sanded off, would make life easier in order to match the 45-60º winding. With good gloves and a prewetting device it would make for a fun project.
I would think a joint wound with cloth tapes would have about the same strength as one made with roving, but a neat job done with roving could be a considerably better looking and lighter (but would take longer). Could it be wound/lashed/frapped with dry roving and then reliably wet out? That would be easier, if it works.

It's just a subjective point but I'm having trouble getting past the looks of those taped joints. It might work just fine, and that's the most important thing
 

berridos

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I guess a mixture of both would be ideal. Initially 0º with tape and on top roving in 45 or 60º. May someone remind me the name of the plane out of tubes where the pilots sit in the air on a tube bed and a pusher engine?
 

Vigilant1

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berridos

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Thanks for the breezy link. It was the plane i was thinking about. Calculating those trusses, should be manageable and that plane is a workhorse.
 
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