Sunday, January 21, 2018

Flaps

Moving on to the flaps.
It is after New Years and I still have a little bit left on the wings, namely the flaps and the internal mechanisms.

The normal match drilling and bracket fabrication went as per the instructions, no drama there. The spar is countersunk for AD3 size rivets. The normal method is to go 0.007" deeper to have the spar dimple mesh better with the skin's dimple. However this spar is barely 0.040" thick and this would have enlarge the holes in the spar, so I only went 0.002" deeper.
 I primed and painted  the inside of the flap bracket prior to assembly; I didn't feel this could get painted by the painters once assembled. I also painted the edges of the spacer. When riveting together I found some old hobby spruce that fit very well as a spacer when clamped in the vise.


















When bucking the spar to skin rivets, I used a scrap piece of thin plywood to protect the spar. The plans call out  AD3-3.5 rivets but these are just barely long enough. I used -3.5's on the top spar to skin because these were easy to set and easy to get a precise smash down within spec. However, for the bottom skin to the spar, I used AD3-4's. The extra length made it easy to set within spec without having to really worry about get it exact; these rivet are set blind so are hard to inspect and harder to gauge when being driven. Using the longer rivets and having previously set the spar countersink depth at the low end, the riveting came out nice.
I used tape to hold open the skins while riveting the skins. This helped, but it was too easy to open the skins too wide and create a gap between the skins and the spar.



 
 All that is left is pro-sealing the trailing edges and trailing edge riveting.