Day 21 - A mistake!      Hours today: 10      Hours so far: 172


Oops. When I fitted the flap and aileron bellcranks last week, I put them on wrongly - they fit between the leading and trailing edges, not on the front edge of the spar tube. This meant I had to replace the spar tubes on one flap and one aileron...

Click on the pictures to enlarge.

Terry supplied me with more spar tube, so I had to remove the old ones. First I cut the tubes into sections to help remove them, then I heated each glue joint carefully with a heat gun. The glue loses its grip so that you can remove it and then gently twist the tube out. I took my time doing this - about 3 hours for both flap and aileron. Now I will have to glue in a new spar tube. As Homer would say, "DOH!"

Next job was to fit the new spar tubes. I made a jig to hold the flap securely, then glued the tube to the capstrips. This was fairly easy, given the trailing edge was already in place.

Once the glue had dried (24 hours) I prepared to fit the leading edge - trial fit the false ribs (a couple need shaping to fit over the hinges), lay out all the different pieces, then mix up some glue. As before, I fitted the false ribs first, waited for the glue to stiffen, then put the whole thing together, holding it in place with tape. When this is dry, I will cut the leading edge as with the ones on day 14. (Note: The aileron bellcrank is in the right position in this picture!)

I have been asked about the glue - it's a two part Loctite Hysol adhesive. I use digital scales to weigh each tin, take out some glue, then weigh the tin again. This way I can ensure an accurate 1:1 ratio. This is mixed on a scrap piece of wood, then put into a regular plastic bag. I snip the corner off the bag and use it like a cake icing bag - after a little practice you can get neat results. Most jobs need (at most) 20 grammes of each part (40gm of glue) - it remains workable for about 40 minutes, depending on the temperature (the warmer the workshop, the less time you have!)

I am surprised that this was my first real mistake, and I am glad it was repairable - a good reminder to read the manual five times before gluing anything! Next page