This note addresses a scheme for the sweep-keeping cross tube or spreader tube of some TPHG designs (tiny-packed hang glider designs).
Left Spreader-Tube Subassembly:
Consists of three tubes: A, B, and A.
The A tubes are each 5 ft in length with an inside diameter of 1.5 inches.
The B tube is 2.5 ft in length, and there are two of these B tubes.
The two shorter B tubes telescope into the larger A tube.
Right Spreader-Tube Subassembly is similar to the Left Spreader-Tube Subassembly. When left and right are coupled over the keel, then one has the Spreader-Tube Assembly.
Joining the left and right spreader-tube subassemblies over the keel:
The left and right spreader-tube subassemblies are joined together over the keel of the hang glider.
This joining is achieved using a reinforced rubber tube coupler.
The coupler is secured in position using pip pins.
Inside the reinforced rubber tube coupler, there is a ball.
During flight, positive loads cause the left and right spreader tubes to compress this ball.
The joint will be lashed to the keel to form a firm node to resist buckling in the macro spreader-tube assembly. Then the left subassembly structure provides its center tube for resisting buckling; same for the right subassembly. The two As fit inside a B tube. At tiny packing there are two seen As holding the four Bs. Inside the Bs might be a queen post.
To set the As to the B, a Joe Strap and ring collar could be used; keep wobble to minimum.
The lengths and diameters may change to fit a particular build.
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Packing note: One option being explored: Inside the packed B tube will be two A tubes; each A tube about half the length of the B tube. Inside the lined-up A tubes may be 5-ft queen post. Thus upon packing seeing two B tubes would be equivalent to seeing the 2B, 4A, and 2Queens. In pack, then, have 3 longs for the 2 LEs and keel, and the 2 longs just described: total 5 longs (5 ft long). Deep inside those 5 visual longs could also be sections of batten-ribs for the Double Castle sail construction. A sixth long position would be available in the pack for more batten-rib sections and a kingpost; then in the 2"x12"x60" pack of longs there will be small spaces outside the longs for some batten-rib insertions. All such could perhaps be settled into a one carried pack, or a one-crutch pack, or a two-crutch pack; such said, be ready for secondary packs: thin back, robust chest, calf-chin, helmet, worn harness,... When off the bus or other vehicle, all gear can be transformed into a wagon for trekking.
Build notes: A second set of mandrels 6-ft long are ordered and on their way to home. Ten pieces of various diameters. When they arrive, I'll have two sets of the ten sizes, all 6-ft long. These tubes are intended to be mandrels for making carbon-fiber tubes for building various experimental tiny-packed HGs. The two queen posts in a mostly CF wing will remain aluminum for safety sake against splintering CF. Aiing: non-rigid base of triangle control frame in some builds. A large learning curve is occurring regarding DIY CF tube making; tooling up is a challenge; curing oven seems to be a big challenge.
Why two sets of mandrels? Plan is to cure at least two tubes per effort; often two tubes of same inside diameter per effort cycle would be nice. It is expected that my DIY CF tubes will not match the quality of tubes that might be purchased from established tube manufacturers.