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| The Front and Rear wing mounts |
In the last week of preparation for our wing load testing in late October, we worked feverishly to get many items completed for the tests. These included the wing mounts on the center wing section, the mating parts for the wing mounts (wing mount cradle and pin tubes) on the pseudo-fuselage, and pseudo-fuselage itself, and all of the wing connection brackets.
The pseudo-fuselage is an aluminum part designed to take the place of the actual carbon fiber fuselage frame during the load testing of the wing, so that if anything goes wrong with the wing during the test, we don't also trash a perfectly good fuselage frame.
Wing Connection Brackets
We put a couple of layers of fiberglass wrap over the cylindrical part of the wing connection brackets, where they get glued into the rear spar and front support tubes, as a way of helping prevent galvanic corrosion between the aluminum and carbon fiber. We wrap the wet layup of fiberglass and epoxy with shrink tape and shrink it with a heat gun.
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| Some of the wing connection brackets prior to wrapping |
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| Spreading epoxy out on fiberglass wrap |
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| Wrapping a wing connection bracket w/ fiberglass and epoxy |
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| Shinking the shrink tape with a heat gun |
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| Shrinking the tape (tape roll visible on table) |
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| Finished parts, curing |
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| The chess pieces face off |
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| Another view of some of the wing connector brackets, prior to fiberglassing |
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| Gluing wing connection brackets in end of rear spar |
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| Gluing wing connection bracket in front support tube |
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| Another view of front wing connection bracket gluing |
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| Three wing sections side-by-side for wing connection bracket gluing |
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| Wing sections clamped in place prior to drilling brackets |
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| Fit of a wing connection bracket prior to drilling |
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| Wing connection brackets with spacer shims in place |
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| Two wing sections clamped in place prior to bracket drilling |
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| Drilling fixture and pins |
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| Drilling instructions |
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| Drilling the wing connection bracket |
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| Reaming hole to final size |
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| After hole drilled, before removing fixture |
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| Pin in place |
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| Front pin in place, rear pin ready for insertion |
Wing Mount Cradles
The half of the wing mounts on the fuselage side consist of two end-grain balsa cradles that are strong enough to support the weight of the wing in compression, topped by an aluminum "pin tube" that the steel pin goes through, connecting it to the other half of the wing mount on the fuselage. The pin tube is held in place by multiple wraps of Kevlar tow infused with epoxy. That Kevlar is all the holds the entire weight of the fuselage to the wing.
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| Raw materials -- a large chunk of balsa and a drawing of the cradle |
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| Rough shapes are cut out on a small tabletop bandsaw |
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| Sanding the groove for the Pin Tube |
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| Oops! |
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| Fixed! |
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| Finished parts |
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| With pin tubes tack glued in place, and ready to glue to Top Tube |
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| Wing Mount Cradles glued to Top Tube of pseudo-fuse |
Wing Mount Brackets
The wing is mounted in two places in the center of the Center wing section, the main mount in front, and a rear mount near the rear spar. The main mount consists of a plywood box covered with carbon fiber, holding two aluminum rings (or "bobbins") that fit around the pin tube at the front of the fuselage. A steel pin joins the pin tube and the bobbins. Those rings are held on by generous wraps of Kevlar tow.
The rear wing mount is an aluminum C shape that the rear wing mount pin goes through, joining it to the rear pin tube attached to the fuselage.
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| Foam core with plywood templates, about to be cut out (templates later form a part of the box around the foam) |
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| Foam core after cutting out |
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| The sides of the plywood box, with extra supports at top for the bobbins |
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| Test fitting the wing mount plywood box |
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| Prepping the box parts |
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| Gluing the box together |
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| Detail showing Rohacell spacers to fit plywood to foam |
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| Wing mount box with bobbins in place |
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| Alignment pin in place to ensure the bobbins are square with the pin |
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| Test fitting placement of main wing mount |
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| Gluing wing mount box in place |
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| Gluing front wing mount using pseudo-fuse top tube for alignment |
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| Gluing rear wing mount |
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| Wing mounts glued in place and drying, with Top Tube as alignment jig |
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| Epoxying carbon fiber cloth on the front wing mount |
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| Vacuum bagging the front wing mount |
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| Lashing the rear mount |
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| Lashing the bobbins on the front mount |
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| The completed wing mounts |
Pseudo-Fuselage (for wing load testing)
The pseudo-fuselage is used to hold the wing during load testing, so that the real fuselage will not get damaged during testing. It's made out of aluminum tubing (much heavier than the real fuselage) and is designed to be picked up with a forklift during testing.
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| Pseudo-fuse parts ready to be glued |
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| Lift points ready to be glued |
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| Rear Tube of pseudo-fuse spliced together |
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| Lashing pseudo-fuse parts |
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| Detail of lashing with clips, prior to epoxy |
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| Epoxying the lashings |
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| The completed pseudo-fuselage, prior to trimming lashings |
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| Closeup of the wing mount cradle and pin tube lashing |
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| Bending the base of the lift wire fitting |
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| Two more pieces of lift wire fitting base |
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| Making the lift wire fitting wire and terminating it |
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| Completed lift wire fitting prior to soldering to brass base plate |
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| Lift wire fitting soldered to brass plate |
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| Gluing the lift wire fitting to the pseudo-fuse (to be lashed later) |
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| In the end the solder broke, and we had to glue the fitting in place |
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| Finished glue joint |
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| Lift wire fitting lashed in place |
Prepping the 2-Liter bottles for the wing load test
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| Measuring the amount of water in the 2-Liter bottles for the load test |
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