30th March 2010 - Bevelling the rear spar

This was a job I was worried about: two 11ft lengths of expensive hard-to-get wood that needed a 9.5 degree bevel along one edge. The options were to plane it, to cut it on the table saw, or to cut it on the bandsaw. I decided to use the bandsaw with a new 4TPI blade. The bandsaw was screwed to the workbench and the bandsaw table was set at the required angle. A jig was constructed to keep the stock in position as it passed the blade. A few test cuts were done on some scrap timber and then it was time to do it for real. Supports were set up for the timber both before and after the bandsaw so there would be no moment trying to lift one end away from the table then the timber positioned and the cut started. The timber was slowly fed through and a perfect cut resulted with the offcut maintaining exactly the same wedge shape and dimensions throughout. The second spar was then bevelled in the same way and I could breathe again! Now I can really make a start on the wing construction.

30th March 2010 - Laminating the Spar

Finally progress!!!

I've been stalled since last year basically waiting for wood for the wing spars. It proved impossible in the UK to get the main spars in single pieces to a suitable quality so the LAA have authorised laminating two sections of Douglas Fir 2.5" * 1.25" to make the 5" * 1.25" main spar. The wood arrived last week and today was the first opportunity to get going. Douglas fir is a bit difficult to glue as it is resinous but I've used the West System epoxy with the slower 206 hardener according to their recommendations, First the surfaces to be glued were sanded with #80 sandpaper to create a key for the glue. The surfaces were then cleaned with acetone to remove grease and resin. Next the epoxy mix was brushed onto both surfaces. Finally, filler was added to more of the epoxy mix (6% by weight of 403 micro-fibres) and this was spread onto one of the surfaces. The two pieces were the aligned and clamped together gently to avoid squeezing out all the glue. 24 hours from now the bond should be cured but will continue to strengthen for the next week.

It has been difficult to get into the workshop over the last few months due to a combination of cold weather and work, but I have spent some time building a CNC router as shown in the second picture. This is based on the design shown on http://www.buildyourcnc.com/ and is amazingly accurate. The spindle is a conventional 1/2" router and you may be able to see the outline of my first test project ( a bird box) in the sacrificial top board. Lots of new things to learn with CNC, CAD and CAM software all required to produce a finished article. The router will cut aluminium and one of the designs done so far but only cut in MDF is a propellor crush plate.