When I tried to put the ailerons together I noted a large curve in both spars which made clecoing almost impossible without large force. I made a search on the Vans Air Force forum and found the topic but with no conclusion. My Inspector was away so I contacted Vans support for the first time on the phone and spoke to Gus.
He was most helpful and suggested I place the spar on some raised wood and use the end as a fulcrum for a downward bend making progressive moves. I placed the spar over the edge between the lightening holes, gave two light/medium presses down, moved towards the centre one hole at a time then turned it around to repeat the other end. I did this twice and the spar came out nice and flat.
The ailerons then cleco'd together easily, another reason for choosing Van's - live builder support.
