Wingtip Hinge Stops

Time: 3 Hours

I got in the shop today after my weekend breakfast with Glenn for a couple hours. Today’s task was to make the wingtip hinge pin stops. These are made from a scrap plastic cutting board of all things. This is a pilot designed mod that has been used by many builders so I’m just copying their ideas. The idea is to cut the hinge pins so that they are a length that will slide into a chunk of the cutting board. Then that chunk can be screwed into the wingtip rib with a nutplate. Sounds weird but photos will help explain it. First up was to match drill the rib to the wingtip like I did on the right side. 

 Then I drilled for and riveted a not played 2 inches from the tooling hole. I’ve been shaped a piece of the cutting board two inches long into the shape of the rib.
 I clecko’ed the rib in place and reinstalled the wing tip on the wing as well as remove the aileron jigs so I could move them. 
 I removed the block and drilled tow #40 holes in the forward end of the block for the hinge pens to slide into. I marked the depth on the outside edge and return the block to the rib to mark the hinge pins to cut. After the pins were cut I return them to the wingtip and slid the block over each of the pin ends and screwed the block to the rib.

 What an awesome way to secure these hinge pins, I think they look great!

Flap Sensor

Time: 1 Hour

I did some organizing and shop cleanup yesterday and did a little work on the flap position sensor that I had worked on a while ago. My main goal was to clean up the bracket I made and to finalize the wire connections. I decided to use d-sub pins, male on the sensor side and female on the wire run side, to make the connections based on recommendations on the vansairforce.com forums. These are small and light and work well with the very small 26awg wire. To hold them together I used small shrink tube which worked well. I also ran the wire aft and down following the smoke system pressure line. 

I like how clean this looks and will be easy to cut the heat shrink off over the d-sub pins to do maintainance or remove. I also put a nutplate in place for the screw that holds the sensor bracket to the bulkhead rather than a screw and nut. That’s because I forgot that this area will be covered by the baggage floor pan and will make it inaccessible. 

Elevator Tips Riveted

Time: 4 Hours

I had a little time in the shop to secure the elevator tips to the elevator. First up was to countersink the fiberglass to accept the dimples of the elevator skins. I then dimpled all the holes except the four holes that had two overlapping skins where I countersunk them. 

I then cleaned up the elevator edges as well as sand and scuff the finerglass especially the flanges that would be riveted. Based on some other builders I planned on using structural adhesive to help bond the fiberglass to the elevators along with rivets. 

I mixed up this adhesive and applied it to the top and bottoms flanges and slid the tip in place.  These tips are riveted with blind rivets since there is no access to buck solid rivets. 

I plan on closing up the forward ends of the tips where they go over the counterweight. So I mixed up some epoxy and flox to start this process and fill in the gaps around the weight. 

When theses are cured I will cut some fiberglass that will lay over the from and get epoxied in place for structure. I will then be able to sand and shape this end and add balloons as needed to shape them. To finish up the day I grabbed my orbital sander and some 220 grit paper to work on the left wing tip gap. 

Thats where I called it a dusty day. 

Left Tip Looks Great

Time: 6 Hours

I came in the shop and removed the clamps and level to see that the tip stayed in perfect shape. I removed the tip and filled in all the chips and cuts in the aft end from all the cutting I had done on it with epoxy and flox. 

SSince I did all the trimming on the top where the tip met the wing I had a pretty uneven gap between the two surfaces. To fix this my plane was to used epoxy and micro balloons to close that gap. The process was to line the edge of the wing and its hinge with packing tape to act as a release agent. 

I used a putty knife to get the tape tight into the corner as I went. I then put the tip back in place with the hinge pins. Here you can see the gaps I was talking about. I mixed up the epoxy and balloons and applied a liberal amount making sure it was filling the gap. 
I also used it to fill several chips on the tip. 

While I was working on the fiberglass I moved on to the elevator tips that I had skipped a couple of years ago while working on the tail. 


Not hard work just trial and error as you trim and cut to get them to fit right. I will work on securing them in my next shop time. 

Left Wing Tip Problem

Time: 6 Hours

As Glenn and I were talking and looking at the left wing tip as it was installed we noticed a problem. With my installation I didn’t notice how the trailing edge line looked! I was concerned that the trailing edge matched up with the aileron hence the need to split open that edge so I could make it rise or lower as needed. What I didn’t do was sight down the entire length of the wing. What we found was that the wing tip drooped down almost 3/4″ over the run of the tip!

Thats not good, so I thought maybe there will be the same dip in the right wingtip keeping things symmetrical so I grabbed the right wing tip and installed it. Yep that’s right it’s perfectly straight unlike the terrible left tip! 

Ok so now how do I fix the left side. The intial plan was to split the aft end and see what we can do. That didn’t give us much results. So we started splitting the outboard from aft to front a little at a time to see what we could get. No luck every time we moved or manipulated we ended up getting bulges or stresses. So I cleaned up my work area and called it a night to go home and think. I was deflated on what to do and did a bunch of research to come up with some plan. Well this morning I had no idea what to do and was going to order a new wing tip and start over. That was going to be around $300 with shipping and I was looking forward to that. So one option Glenn and I are talking about was to shorten the top edge that runs along the wing skin, where the hinge is. This would require drilling out all the rivets and chiseling off the hinge and fiberglass. I figured it was worth a shot before buying a new one. So I removed the tip and started drilling. It didn’t take too long to get all of them done and removed the hinge. So I marked a line along the top of the tip inset 3/16″ and removed that material with my orbital sander.  Why 3/16″? It was just a guess on my part and I went with it. I then returned the tip to the wing and put the lower hinge pin in and pushed the top up tight. To my surprise it fit pretty good and the outboard tip matched up to the level meaning it was inline with the aileron! Ok so I removed the tip and grabbed a new section of hinge for the tip side and cut it to size. I put it in place on the top hinge of the wing side. With it I place I returned the tip using the lower hinge pin. I then pushed the top up tight and clamped it in place. I drew a line 3/16″ outboard on the top of the tip, this will be the new rivet line since I moved the top that much inboard.



 I drilled one hole at the aft end of the rivet line and put a clecko in to check the trailing edge alignment.  Wow it looked great! So I drilled the rest of the rivet holes and clecko’ed them. So I then made some shims to keep the trailing edge the right thickness since I split it open. I mixed up some epoxy with flox and buttered the split edges and clamped them in place with the level. 



So I will let that cure before unclamping to see how it turned out. What a new experience working with fiberglass. While the left side was sitting I removed the right tip to finish work on it.  First up was to cut the rib that closes the aft end of the tip. Since I decided to use hinges this rib needed a little modification to get it fit.  


Second was to address the flimsy middle section of the top. From what I have read and Glenn told me is that the flimsy top will flex and move a lot in flight potentially causing paint cracks and just looking terrible in flight. Guys have used rigid foam cutbtonshape and epoxied in place.  For me I decided to follow Jason Beavers advice and use some foam backer rod, this is a foam rope that made to fill concrete gaps before caulking. This rod is just used to create a shape for an overlay of fiberglass to make a stiffening layup. The idea is that after the layup cures it acts as a rigid vertical element to the flat part to give it rigidity. So I figured out where the flexing would occur and cut a couple peices to length. Then I used my hot glue gun to tack the ends in place. 

I then cut some 3″ fiberglass to cover the rod with an inch or two overhang to finish the look. I mixed some epoxy and wet the glass into position.

That was enough fiberglass for one day and I cleaned up my messes and called it a day.