Wing Tips (2)

I picked up where I left off yesterday and finished drilling both wing tips to the wings.  They both matched up pretty well with the ailerons in neutral.

A rib is riveted into the wing tip to stiffen up the portion that is open next to the aileron.  The rest of the wing tip will be screwed onto the wing using nutplates. There's no callout for where the rib gets placed - I just slid it into the tip until it was snug and fit the shape of the fiberglass.

I laid out the rivets and match drilled the rib to the wing tip.  

Wing Tips

It's hard to show pictures that look any different than the 100 others of the cowl.  I'm still working on the fit of it all.  I'm at the point where I don't think I can get the gaps to their final state without having the hinges riveted on.  Before I do that I want to spray epoxy primer and paint on the interior though - protection from oil and other nasty engine fluids.  There's gobs of work left to do on the fit and finish, but I need a mental break.  I'm going to move on to some other fiberglass.  I now see why it's common for builders to say the cowl was a morale killer for them.  It's a lot like the canopy - every change you make causes the whole thing to shift and need rework.

I'm going to jump over to the wing tips just for a change of pace.  The first step is to mount the  aileron and find its neutral position so the trailing edge of the wing tip can be matched to it.  I loosely bolted the aileron in place and used a jig to set it at neutral (the jig is just a piece of wood attached to a couple of holes in the outboard wing rib that helps indicate the neutral position of the aileron).

The wing tip has a number of areas that have to be trimmed to fit around the aileron hinge brackets, as well as to give the appropriate 1/4" gap between the fiberglass and the aileron skins.

After a number of iterations, I got a pretty decent fit and started drilling the holes into the fiberglass.  The wingtip will be attached to the wing skin with nutplates and screws.  The wingtip extends aft about 1/8" beyond the aileron.  I haven't decided if I care enough to cut it down so it's even - if I do that, it'll be more than just sanding it down.  It'll crack open and have to be closed back up by laying fiberglass on the inside (not easy to reach into that tight angle).

Death by Sanding

The spark plug wire for the front left cylinder (2) is long enough that it needs some support to keep it from flopping around.  I made a little standoff for an adel clamp and attached it to the clamp that supports the fuel line.

The cowl work is never going to end.  I had a few minutes before I had to leave, so I mixed up some epoxy/flox, scarfed the horizontal fuselage edge of the the top cowl and put the epoxy on to lengthen the edge.  To keep it a little cleaner on the top side, I clecoed on some backer material (thin aluminum and a cereal box with packing tape to make the epoxy release easier) before spreading the epoxy on.  Unfortunately, it turns out I didn't extend the edge far enough towards the center, so I'm going to have to do it again.

The other day I had cut a notch in the bottom corner of the lower cowl so I could pull it into a better shape to match the fuselage.  I pulled the cured cowl off to see how it looked.  Not too bad.  The point of the fiberglass inside was mostly to just hold it in position so I could fill it from the outside.

I used the Dremel to grind in a scarf for the epoxy/flox.

Once it was dry I sanded to smooth it out to a decent curve.  I don't need to get it perfect, since I'll be using either micro or filler to smooth things out before paint anyway.

I put the cowl back in place and sanded the both corners to match up with the fuselage.

Next up, I bent the louvers that will be riveted to the bottom cowl.  I'm not going to rivet them in place until I've finished up with the cowl and sprayed epoxy and paint on the inside.  The finish is just to make the cowl easier to clean.

The nose bowl flanges on the lower cowl that the top cowl nests over are an absolute nightmare to get right.  At first I thought I'd spread a bunch of flox on them and then resand them.  After messing with them for a while, I decided to take the route that a lot of people do and just cut them off!  Once I have the cowls fitting nicely, I'll rivet on a piece of aluminum to act as the flange instead.  The aluminum will be much easier to fit the top cowl to.

I put the cowls back on to test the fit.  This is where I discovered that I still need to extend the top edge about 1/32"+.  I also discovered that I did too much sanding on the right side of the lower cowl where I already extended the edge!  Ughh!  I am positive I sanded it to the right length when I had put the lower cowl on and off, but when I put everything back together, it's too short.  I guess that's the good thing about fiberglass - I can just keep fixing my stupid mistakes.

More sanding on the front end too.  It's still extremely rough, but it's slowly starting to match up.  I will be very happy once I get these cowls finished!  Admittedly, it's taking a while because I only have the energy to do small portions at a time.  Van's always says they don't update parts like this because they want to keep costs low.  I think I speak for every builder when I say I would have gladly paid extra for better fitting parts!