Make Blades While the Rain Falls

If the Sun was shining I would be on the bike with the flying wing, but it’s grey, windy and drizzling, with the forecast for it to continue that way until mid morning.

Yesterday I started making the blades for my ATOM autogyro. It’s all a bit confusing as the commercial AJ Blades ones are 450mm x 44mm: http://www.ajblades.co.uk/450mm-x-44mm-109-p.asp

There are also a number of PDF documents online at RCGroups which were produced by Rich Harris and which show 450 x 60mm blades: http://www.rcgroups.com/forums/showthread.php?t=2307081

Various people on the RCM&E ATOM thread have different blade designs, but the consensus seems to be to use either the AJ Blades 44mm ones or the 60mm ones. Having decided to go with the 60mm design, the first thing I discovered was that I only had one sheet of 5mm balsa left and it was 100mm wide. The 60mm blades need 450mm x 54mm balsa blanks plus a 6mm spruce leading edge to make the 60mm, so I decided to alter this to three 450mm x 50mm blasa blanks which I could get from my last remaining sheet of wood. It probably doesn’t make that much difference (let’s see it fly first), but using the same sheet to make all the blades must be a better option in terms of density matching rather than using two different sheets. Anyway, from my piece of wood I made four blades, of which I will pick the best matched three. The pictures show the progress so far:

450 x 50mm balsa blanks waiting for the 6mm spruce leading edge to be added

450 x 50mm balsa blanks waiting for the 6mm spruce leading edge to be added

Leading edges epoxied and taped in place waiting for the glue to cure

Leading edges epoxied and taped in place waiting for the glue to set

The finished blade blanks trimmed to length, ready for the profile to be sanded

The finished blade blanks trimmed to length, ready for the profile to be sanded

I now have four square blade blanks waiting for me to figure out how to sand them to the correct profile. The silly thing is I don’t have a printer here, so I can’t print out the aerofoil from the PDF. What I might try is copying it onto a piece of paper by tracing from the computer screen. Not exactly high tech, but without a printer or projector I can’t think of any other way to do it and I would like to get this done today. As for the sanding, I have a number of razor planes I’ve been wanting to try out, along with all my trusty Perma Grit files which I could never do without.

Let’s go create some dust…

(balsa dust is dangerous if inhaled, so always use a mask)

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