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.
We got the remaining parts of the prop blade A cut out today, so now you can see much more clearly what it looks like. Next step is finish sanding, then fiberglassing. (Then on to blade B.)
All 12 sections of the new prop blade together on the spar.
Old Prop blade vs. New Prop blade (new blade is longer, but is slightly in front so looks even larger in this view)
Prop Blade A sitting on top of the blocks for Blade B waiting to be cut out
Yesterday we received by FedEx air freight all the shorter tubes that make up the fuselage and drivetrain parts of the airplane. They are incredibly strong and light. Now we'll start testing the drivetrain parts on our static rig, then build a complete fuselage while we wait for the longer tubes that make up the wing, tail and tail boom to arrive by sea freight in about 6 to 8 weeks.
All the tubes, unpacked
The tubes, partially unpacked (still many tubes inside of other tubes...)
We have made some progress on the new propeller, 3.66 m diameter, 147 RPM for climb power, and ~125 RPM for cruise.
We are making this out of white 1 pound per cubic foot foam. It is using a carbon fiber ski-pole spar and light fiberglass cloth and epoxy for covering. Due to the large chord, it is going to be heavier than we'd like and we had hoped to make it in a denser foam, but we will stick for this lighter foam for now to keep the weight down. We'll probably redesign a new prop for higher RPM and smaller chords (and thus volume and weight) in the future.
Hot Wiring the top surface of a prop blade section
The resulting cut
A prop section fully cut out, templates still in place
"147-14" prop, 7 of 12 sections in place on the spar
Sections of the 3.66 m diameter prop next to our existing 3.05 m diameter prop
We cut out the first full size rib templates on the ShopBot today. We'll be using those to cut out 2 to 4 inch wide rib shapes from several different densities of foam. Those will be sheeted with .4 mm plywood, and we'll try several different types of glue for each.
After those pieces dry, 6 mm wide ribs are cut out to make the final rib shapes. We'll be using these ribs in our practice wing section using a dummy alminum wing spar and rear spar, to get practice with building all the parts of a complete wing section prior to trying to build it out of the real carbon fiber parts that we hope will arrive sometime in mid-October.
Yesterday, we cut out some wooden washers we'll use to get more precise on the internal hole size for the foam core pieces of our next prop. The hole we'll hot wire out using these washers is what the circular carbon fiber spar of the prop fits inside.
Also, we heard late this evening from C-Tech that a full set of the under-3 meter carbon fiber tubes shipped by air freight today, so we should get them sometime around Labor Day, and we'll be able to try out drivetrain parts on our static test rig, and then build a full-sized fuselage out of real parts soon after that.
Wes shortened the prop shaft and remounted the prop more securely, so it is ready for our larger prop (3.66 m [12 ft] versus the current 3.05 m diameter prop). We hope to have the first version of the larger prop competed in the next week or so.
C-Tech continues to produce more parts for the plane and we should see some of the first parts here in the next couple of weeks that will let us try out real carbon fiber components in the drivetrain and fuselage.
I visited C-Tech on 2-August-2012 and saw the first of our carbon fiber tube parts being built. Over the next several weeks, some of the fuselage tubes will be built and shipped by air, and following that the larger wing and tail boom tubes will be built and shipped by boat.
C-Tech has an impressive setup and makes carbon fiber tubes and masts for all sorts of purposes -- much of it sailing related (battens, masts et cetera), but also for items as varied as movie cranes and traffic monitoring poles.
Here are some photos of some of our first parts:.
Pull used for removing part from mandrel (with a 2-ton winch)
Half of outer rear spar (20 mm ID), pulled most of the way off the mandrel so second half can be built with a splice in the middle (total part is longer than the mandrel). Aluminum mandrel is visible in the back.
Closeup of the splice area where second half of the part will be overlaid on aluminum mandrel
Tight wind spiral is surface of epoxy marking where shrink wrap tape was. (This part has 45 degree carbon fiber torsion layers, not visible here.)
Adding spar caps to second half of Outer Rear Spar part (spliced area is off of screen and not visible).
Outer Rear Spar with spar caps oriented side-to-side
Outer Rear Spar with spar caps oriented vertically, showing increased stiffness in that direction
Prepping the 76 mm mandrel with release film to produce the Top Tube
Closeup of Release Film
Wall 'O Mandrels
Mandrel for Bottom bracket -- Carbon fiber over steel, the carbon fiber will be ground to 46 mm OD to match ID of BB, then used as a mandrel for the actual Bottom Bracket parts
Finished Support Tube piece (12.7 mm ID), will be cut to smaller lengths and used as supports between main spar and rear spar
Tapered mandrel to be used for Tail Boom. It is a bit hard to see the taper in this photo due to foreshortening, but it is 76 mm OD at the left, and where it becomes lighter colored in the middle of the part between the wooden supports is where the taper starts. At the near end closest to the camera it is 43 mm OD.
