A Whole 'lotta Wood

Tom and I bought all the wood and supplies to build 3 more work tables for DaSH (the same table design as this: http://picasaweb.google.com/alec.proudfoot/30Dec2010_DaSH_Work_Table?authkey=Gv1sRgCIfs3bia5vH5mgE#5558045266940278658 )

It was a LOT of wood.  Just buying it, transporting it, and unloading it took about 5 hours.

I look forward to seeing everyone who can make it at the table build on Thursday night 2/3, starting at 7:30 p.m.!

If you plan to make it, fill out this form so we know how many people to expect.  (Will take 5 seconds, just list your name:  https://spreadsheets.google.com/viewform?formkey=dGRpWUthTkxFOTdDVXJrZGpqZGdOMmc6MQ )


-- Alec



P.S.  All photos:

http://picasaweb.google.com/alec.proudfoot/JanFeb2011DaSHTableBuild#

Airfoil Laser Cutting tests

On Wednesday night, 1/26/11, Matt and I did some laser cutting tests with various materials.

We tried Spyder foam (a form of dense, anisotropic blue styrofoam), to see if we could possibly use the laser method to cut out many thin sheets that we could stack up to make our next propeller.  The laser cut a very precise shape on the surface, but the heat caused an undercut, scalloped edge.  So that method probably wouldn't work too well for stacking many sections on to build up a prop.  However, it is possible to cut foam if we aren't too concerned about the exact dimensions (or only want exact dimensions on the skin and undercutting is what we are looking for on the rest of the part).

However, the laser did a fantastic job of cutting out balsa wood (as previous tests had shown), and also thin spruce plywood -- we tried both 1/32 and 3/32" sheets.  The plywood is perfect for making templates that can then be used to hot wire cut foam for the propeller and for the main wing (we will need to get creative about joining template halves for the full wing templates, since we are limited to a 24 inch working area, and our wing chord for the airplane is likely to be 4 feet or greater...).

We also tried cutting out keyways in the balsa wood ribs.  If we built another built-up wood prop, we would probably use this method to make the alignment of the ribs much quicker, easier and more precise. However, our next prop will probably be foam as described above.  (The spruce keys shown loose here would be glued to the side of the spar in practice).

More photos are available here:

http://picasaweb.google.com/alec.proudfoot/26Jan2011_DaSH_laser_cut_tests#

-- Alec

First Hardware!

Saturday night, 15-Jan-2011, we finished our first DaSH hardware -- prototype prop blades (designed for a 16 mph aircraft -- we still need to finalize the aircraft layout, wing area and speed).

Tom holds the finished propeller blades

We had a lot of fun building these and learned a lot about how to build it better then next time.

These props were built up from Aluminum spars, balsa wood ribs and sheeting, and spruce secondary spars.  We probably won't build the "final" props this way -- more likely they will be built with foam covered by light fiberglass cloth, with either an aluminum or carbon fiber spar.  But these props are fully functional and should work, and they actually aren't too heavy.


Final stats:

- 1.227 kg (Blade A -- 0.6113 kg , Blade B -- 0.6157 kg, 4.4 grams apart)

- 193 man hours 

- 2 weeks build time (1/1/2011 to 1/15/2011)

 
To view more photos of the build, go to:  http://picasaweb.google.com/alec.proudfoot/2Jan2011_DaSH_proto_prop_build#