Postings about the DaSH Human Powered Airplane project. Our goal is to have fun and learn while building an HPA on a budget of no more than the price of a new car by keeping the design simple and the build time to a minimum.
Covered full-sized test wing section with dummy aluminum spars
We covered the test wing section that we built last year, in order to practice the covering and make sure there were no buckling problems. We did a much more careful job of taping the sides of the foam ribs before applying the Pliobond, and also avoided using Acetone as a solvent, and had not significant foam melting issues this time.
We experimented some more with putting DuraLar over already bent and installed leading edges, and found it was really tough to put it on without significant wrinkles (which kills the whole purpose). So this reinforced our decision to put the DuraLar on the Depron sheets flat, then bend it together in the heat bath.
Getting the Mylar ready
Mylar stuck in place with double stick tape
Applying Mylar tape over front edge of Mylar
Unsuccessful attempt to add DuraLar to existing leading edge can be seen on top of image
Tacking the Mylar
Tacking and shrinking the Mylar
The finished covering (wing mounted upside down to show larger bottom surface)
Making some 2mm jog rib caps for Ribs 25-28 in v6-WE wingtip extension
We put the lightweight spars in the tail surface, to correct for the buckling problem, and covered the tail surfaces to make finished parts. It added 29 grams to the Vertical tail and 50 grams to the horizontal tail. It cured the buckling problem.
We investigated various pultruded rods and wrapped rods. The lightest, strongest were wrapped rods that were only 30 inches long, so we had to splice them with short interior sleeves of pultruded rod, and Kevlar wrap on the outside of the joints.
Pultruded tube pieces for sleeves
Rear spars for Horizontal and Vertical tails spliced, glued and curing
Using a template to mark rear spar holes
Cutting rear spar hole with hot wand
Closeup of cutting rear spar hole
Installing the rear spar
Kevlar lashing reinforcement on outside of joint
U-shaped doublers applied on either side, and glued in place
Sanding the Doublers flush
Partially completed doubler (one side sanded flush)
After the rear spar repair was done, we added the glue (Pliobond), and covered with Mylar.
Applying Pliobond back to new doubler area
Tacking the Mylar
Initial shrink with iron
Final shrinking with heat guns
Carefully avoiding heating the Depron
Success! Vertical tail complete
Almost done
Horizontal tail complete
We got the tail testing rig set up to test the tails, but ran out of time to test them before my trip...
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Hooking everything up
Prepping to program the tail motion
Adding Pliobond to the 7-rib test section
Prepping Center spar for Kevlar patch for area where wing mount will go
Vacuum bagging the Kevlar wrap on the center spar
Sizing and cutting Kevlar wrap for the Middle Spar (where aluminum lift wire clamp will be glued & lashed)
When we tightened the Mylar on the trailing edges, they buckled in several places on each tail surface. We were trying to save weight on the tails by not having separate rear spars, but it didn't work. Fix will be to add lightweight carbon fiber tubes as rear spars a few cm in front of the trailing edge.
More repairs on melted foam area on other tail surface
Hole to fill
Hole filled
Impromptu extra doubler
Taping the seam between DuraLar covering on leading edge sheets
Tightening the Mylar
Waviness
A buckled mess
Attempts to patch the buckled areas (didn't work, just buckled elsewhere)
We got all the rest of the doublers cut on Chris & Tony's Lasersaur home-built laser cutter
All the rest of the doublers, laser cut
Cutting the tabs out to remove the Doublers from the sheets
Some doublers were plywood, and took a bit of extra work to extract
All the doublers, ready to use, both regular rib and end rib/hard rib full doublers
We made all the fittings for the Kevlar cross bracing, by bending 0.041 piano wire over sailing thimbles, and silver soldering with copper wire wrap
Tool for bending the piano wire around the thimble
