30/12/2012 - Wing Tip installation

I have been looking forward to this day, but also a little nervous of fitting them.

The first cuts were reasonably easy using snips and hack saw as required.  The first critical step is to get the leading edge and sides back to the elevator as snug as possible.  Measure the width of the over hanging skin to the wing rib and mark that wing tip with the same distance and chop away.

We used a tightening strap to make sure the tips were well pressed home and took out any slack so that the edges fit snug to the skin.  Drilled the holes to #30 for the time being and secured them in position. (make sure the strap tightens on the wing end rib and not on the pod !

Quite chuffed with the fit

Then it gets a bit fiddly cutting away to make sure there is a 1/4" gap between the pods and the elevator and elevator mechanism.

Some sanding with 40 grit was required to get the trailing edges to match up.  It maybe required to add some strengthening into the trailing edge near the pod ribs to strengthen it back up.

Do some research when you are this stage, as a number of people are reporting cracks in the gel coat on the wing tips after 200-300 hours including aeros.  There is a good article by Darwin Barrie on VAF that talks about strengthening using dowel rods.  http://www.vansairforce.net/articles.htm

Here is the article on RV-7 wing tip cracking.  Some get it some don't by the sound of it.

Gel Coat Cracking

A little way into the thread there is also mention from Dan Horton who has used two-part expanding urethane foam into the tail end of the tip cavity.  Which is exactly what we were going to do and spent some time setting up.  We rejected the idea in the end and we might be glad we did as Dan found after a while noticed the surface had developed a bunch of crazy lumps and waves in the area over the foam core.

To strengthen the rivet points vans plans call for a narrow bit of aluminium bonded to the inside.  I have used much wider aluminium to give more support.  The large holes are to allow the epoxy through and create a stronger bond.

At this stage I am considering adding the dowels as per Darwin's process to the inside of the pods to protect them from pillowing in flight and hopefully stop any gel cracks.