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.
Pat Enright of Osprey Studios ( http://ospreystudios.com/ ) is building our new prop design -- designated 175-14-400-Spyd-CF16 in our arcane numbering convention (175 RPM climb (~145 RPM at cruise), 14 mph, 400 Watt climb, Spyder Foam, 16mm dia CF spar).
Pat will be machining the prop out of 2.3 pcf Spyder Foam, a foam that looks like regular blue 2.0 pcf (pounds per cubic foot) styrofoam, but which is a fair amount denser in the height dimension (shortest dimension of the block). We'll be pocketing out some of the thick areas near the root to save a bit of weight (about 50 grams), and we predict that the prop, when covered by lightweight 1.4 oz/sq yd fiberglass cloth and epoxy resin, will come out at about 400 to 450 grams per blade.
Below are some renderings of the prop blade from different angles, and a 3D model of how the blade pieces go together (so we can embed the spar), and finally photos of a machining test he did with somewhat denser polyurethane fold to test his CAM file.
Exploded View (lightening pockets not shown)
Machining test of bottom half using polyurethane foam
The last couple off days, we worked on finishing the pilot seat (lashed version, welded to come soon), did more machining and assembly of prop shaft parts, and prepared to put biscuits in the fuselage frame and assemble it, by planning the biscuit locations and drawing a 1:1 side view of the fuselage to be used to size the actual tubes and help position them for tack gluing prior to lashing.
Finishing the seat lacing
Installing the seat support tubes
Telescoping rear seat support tubes
Gluing the Front Bearing Support to the Fuse Tube
Gluing the Rear Hub Shaft to the Fuse Tube. Both these parts are Titanium for light weight and to avoid galvanic corrosion
Glued Fuse Tube (bearing seats still to be trued to final size)
Lashing the rear support tabs (both broke free the day before when under load)
Closeup of lashed support tab
Drawing the full-sized fuselage side view for use in fuselage assembly
Fuselage side view, full size
zee Flugtagers Laura and Nate stopped by to bend their leading edge sheets
(You get the idea -- an obscure reference no one will get years hence unless they read the headlines from today.. :-)
Over the last week or so, we've done a lot of work on the biscuiting tools and biscuits. We built two biscuiting tools, one 7/8" OD for the 35 mm ID downtube (because the larger stuff wouldn't fit), and one 1 1/4" OD for all the other larger OD tubes.
We (Ron, Gregg, Tammy) developed the process for blowing out the dust and left over release film using an air lance, a way for cleaning the silicone release film off with an acetone wash, then using Scotchbrite to scuff up the interior surface (followed by another acetone wash) in preparation for biscuit gluing. Then we cleaned out all the main fuselage tubes for plane #1, as well as the Prop Shaft Rear part and Fuse Tube part (both parts of the Prop Shaft Assy that Wes is machining parts for).
We (Guru & Smitha) also finished most of the carbon fiber faced biscuits for use in strengthening various parts of the fuselage frame and the prop shaft assembly.
Finally, we worked on getting the seat frame mounted to the test rig, and built the rear supports.
Gluing the prongs to a biscuiting tool (biscuit on end used as a guide)
Prongs glued on both biscuiting tools
Syringes with yolks for biscuiting tool
Syringe before going into biscuiting tool
Syringe poking out of tool (plunger up against stop inside)
Stopper for plungers glued inside biscuiting tools
Carbon fiber faced biscuits ready for finishing
Gregg marking the scale on one of the biscuiting tools
What happens when you leave the cap off of polyurethane glue
Seat rear supports in progress
Seat Frame mounting detail on Test Rig (will be simpler on the real thing with just a round tube...)
Smitha and Guru gluing carbon fiber face sheets to biscuits
Transferring Mylar film from one roll to another
Prepping the clamping bolts with wax
Cleaning inside of a fuselage tube with an air lance
On Monday, August 12th, I visited with Joe King and Jacquie Thomas of UC Irvine's HPA team, started by Jacquie several years ago as a freshman.
UCI has independently arrived at a wing planform almost identical to our v5 design. There are differences, though -- they are considering a sailplane-like midwing fuselage rather than a low-slung fuselage like we are using, their prop RPM is higher (and thus prop smaller), they are using a square spar and are thinking of doing without a lift wire, for some examples.
We had a productive discussion for a couple of hours and I got to see some of their test pieces and sample parts. The molding on their prop is beautiful, and they have come up with a very clever design to be able to cut out their leading edge wing skin from a 3" thick piece of Foamular, so that it unfolds to full size (thicker than 3 inches when unfolded).
We'll definitely be keeping in touch with UCI and helping each other out with tips and tricks as our projects progress.
Trying out their propeller test rig
Entrance to the UCI team lair
Hot wire machine by UCI
Prop molds
Back Side of Prop Mold
Prop skins in various states of manufacture. They are experimenting with different internal spar and rib configurations.
