Picking up the pieces

Sunday 27th July (8hr 10min)

Match-drilled reinforcing plates W-907B, C, D and E to the W-907A left and right aft spars. Deburred and edge-prepped all parts. Cut aileron push rod openings in W907D left and right. Countersunk W907C per plans. Dimpled W-907A top flange in way of W907D doubler fork.

I spent Friday in bed with a very heavy cold - no temperature, just feeling sick and very drowsy. By Saturday afternoon, I was definitely on the mend and I felt pretty good this morning with only a little congestion to suggest that I was ever sick. I think I got off lightly. I made the Michael Bublé gig by the way - really enjoyable.

Despite the good news from Vans regarding replacements, it was a sad business to put away the underbent spars. It would have been an interesting challenge to make the repair that Vans suggested but very hard to go right through the process of building the main wing structure with the fear that the stresses of re-bending would emerge as a result of riveting on the top skins and leave me with 'wrinkly wings' through no fault of my own.

I quickly got back into the swing of things by working on the aft spars. I am continuing my plan of carrying out each process on the parts for both wings at the same time. There were no particular problems here but there are a few things to watch out for. All the builders' sites refer to the need for care in deciding which holes on the W-907C doubler plate to countersink and which holes on all the doubler plates to leave open until later. With the help of the plans and these sites, I did not find those issues difficult.

However, what did make me scratch my head was that I seemed to be missing several pre-punched holes on the spar. These holes are for rivets to attach the lower edge of the flap and aileron gap fairings, where they join the W907-D (mid-span) and E (outboard) doubler plates (not the W-907C - its holes are all present and correct). The plans show all six of these holes but they do not exist on the spars and therefore can't be match-drilled through the doubler plates along with the rest. The holes are all pre-punched on the gap fairings themselves so the only option appears to be to match-drill them in assembly with the doubler plates and aft spar using the fairing holes as a guide. I could have done this on the spot but I thought it might be better if the fairings could be clecoed to the skins at their top edge as well as to the spars at their lower edge. In this way, I can be certain that these tabs are hitting the doubler plates at precisely the right point. I better put it on a 'to-do' list so that I don't forget it while the top skins are on for match-drilling.

The other point that wasn't easy to spot, was the fact that the last three outboard rivets through the aft spar and outboard doubler plate (W-907E) need to be flush on the aft side. they will later be covered by an angle associated with the aileron hinge, which is riveted through the neighbouring row of holes. The plans make clear reference to this (if you are careful about reading ALL the notes) but they do not specify whether dimpling or countersinking is appropriate. Some builders have countersunk the doubler plate (leaving the spar untouched) but I think this material is too thin. I need to research this. Somewhere there must be a table giving minimum plate thicknesses for various sizes of countersink. The top flange of the spar was dimpled for the skins so dimpling should not be a problem as the W-907E is made of the same .040 material UPDATE! Section 5 of the manual specifies .050 as the minimum thickness for #30 countersinks, unless the plate to be countersunk is sandwiched between two others, so I have decided to dimple the doubler and countersink the spar, which will be sandwiched between the doubler and the rib on the opposite side