389 hours on the hobbs - left elevator and trim tab progress today

Picked up my tools from the chapter 301 auction held recently. Short story about this is that a member of the chapter passed away recently after a losing bout with cancer, and he essentially donated his hangar and it's contents at KFTG to the chapter. After resolving some legal issues, including the sale of his almost completed T-51 kit to a bloke in Australia, a large assortment of tools remained, and these were auctioned off to chapter members by email. This was the first time I had ever done an auction via email, but it was rather fun.

I ended up with a set of nut drivers, 3 impact wrenches, one air drill, and an assortment if impact sockets and other odds and ends. They basically sorted the tools in the drawers of an absolutely humungous tool chest, took photos, sent them to the bidders, and started the auction which ran for about 2 weeks. The tool chest was also auctioned off to the tune of about $450.00.

Thanks Jack for the opportunity to take care of your tools - rest in peace and I won't let ya down. I almost bit on buying the T-51, which is a kit version of a P-51 fighter, but I was already into my own project and did not want to derail that effort. Sad thing is, he was almost finished with it - even had a Corvette engine ready to put in it. Whole thing went for about $35,000.00.

As for the build - I spent time on the trim tab today. Got the skin bent and primed up, and drilled the holes for the hinge on the trim tab side. Also put the lead counterweight back on the drill press after verifying that the drill bit chuck and my work table were at prefect 90 degree angles to each other. Funny thing about that is that one of the lead plugs I had poured into one of the holes the other day was completely pushed out during the drilling, and the other came out as I was final drilling the hole in the E713 counterbalance skin. Oh well, that means my original holes were close enough I guess.The good news is that everything came out OK this time, but I still need to finish match drilling all the holes in the new E704 part. I also had to rebend the flanges to 90 degrees, and flute it just a bit to straighten it out.

All primed up

We pause this trim tab episode momentarily for a trip back to the tip rib assembly. Here is the problem I spoke of in previous posts. The hole on the right is much too close to the bend in the flange. This is the 704 counter balance rib that I had to replace with a new one.

Next is a side view of the trim tab after the bend, with the forward TT spar clecoed in place. As far as I can tell from doing some preliminary fitting to the elevator, everything should line up perfect if I get the hinge placement correct:

Next are the rivet lines I drew on the piano hinge that will attach the trim tab to the elevator. After much research over the past few days, I resolved that the solution to the rivet hole location problem where there would not be enough edge distance if you follow the 1/4 inch measurement in the plans, was to keep the 6/32 edge distance by measuring from the outside edge of the hinge. As it turned out, when I drew the lines per the measurements I just mentioned, the rivet line is pretty much centered in the main part of the hinge flange, just as it should be, and there is also sufficient edge distance for the rivets. Pics are of lines drawn on both sides:

My research on other builder sites regarding the hinge issues revealed so many little tips and tricks to ensure that this gets done correctly, that I will list most of them here to hopefully benefit future builders.

1. Van's drawings showing the hinge assembly are confusing. One drawing seems to show the eyes of the hinges facing upward toward the top of the skin, while others show the hinge eyes facing downward. DOWNWARD is the correct placement. This allows you to adjust the placement of the hinge flange on the elevator side to ensure proper alignment of the trim tab with the elevator, without the eyes getting in the way of the edges of the skin. It also keeps the hinge line flush with the skin and not sticking up into the slip stream, thereby reducing drag.

2. When drilling the holes in the hinge, you have to mark a line, clamp the hinge to the skin and spar under the prepunched holes, and drill complete holes in the hinge flange - they are NOT prepunched. Also make certain that you DO NOT dimple or countersink the holes in the hinge. The dimples and countersinks are in the spar and the skin - NOT in the hinge. Upper skin gets dimples, the top of the spar gets countersunk, and the hinge just gets drilled with a hole to accept the remaining rivet shank.

3. After drawing your reference lines in the hinge flange, remove the piano hinge pin and separate the hinge halves. I use a 3/32 " punch pin for this.Then clamp the hinge half in place lining up the previously drawn reference line and prepunched holes in the skin as a guide.

4. When riveting the hinge flange, remember to put the piano hinge back onto the eyelets (just the pin and not the other half of the hinge). This helps keep the eyelets from bending or distorting during riveting, which may cause binding when you insert the pin and attach the other half of the hinge.

5. Another tip during riveting is to install the other half of the hinge with the hinge pin, and place the other half of the hinge at 90 degrees to the half that you are riveting to provide even more rigidity during riveting.

6. When trimming the end of the hinge on the inboard side of the trim tab, do NOT trim the hinge pin - only the flanges. Leave the pin at it's original length so you can form the bend or at least have something additional to grab on to to remove and insert the pin easily.

Here is the drilled hinge on the trim tab side in progress and almost complete. Use as many cleco clamps as necessary to keep the hinge from moving while drilling the holes. Start at one end of the hinge and drill each hole in sequence until you reach the other end, to ensure that there are no sags in the hinge line. Van's wants the hinge to be placed laterally so that the outboard edge of the hinge is 3/8" from the nearest hole on that side:

And here is the view from the front side of the trim tab after the hinge line has been drilled. All my holes came out right were I expected - centered on each line - both top and bottom. Be sure to keep your drill straight. You have to be patient and have a steady hand because it takes several seconds for the hole to be drilled through the hinge material - even with a sharp drill bit and my super duper and super expensive Sioux air drill running at full speed. Use the mirror technique by aligning the drill bit with its reflection in the alclad trim tab skin - works like a charm every time for drilling straight holes. Let the drill bit do the cutting and don't force it.

And here is the lead counterweight installed in the tip rib assembly. The bolt has been inserted on both sides (only one side showing in this pic). Boy am I glad that is almost over. I say almost because I still need to the following things before it is ready for the next step:
- match drill the 703 to 704 attach holes
- Match drill the 704 flange attach holes to the E702 forward spar
- Dimple the E713 counterbalance skin holes after making sure that they are sized properly and deburred well to prevent cracking when the huge number 10 dimple die is used to make the dimples.
- Countersink the E714 lead counterweight to accept the dimples from the E713 skin

Then I can finally attach everyting to the foward spar so I can final drill the remaining holes in the elevator skin.

Remember - this counterweight does NOT get trimmed like the one on the right side due to the weight differences with the added spar, trim reinforcement brackets, and trim tab assembly all aft of the elevator hinge line. This requires more weight to counter everything added to the left elevator, so you do NOT trim anything from this counterweight.

This shows a much better placement of the screw on the E704 rib side. Still not centered in the flange, but good enough to accept the washer and the nut that will snug it down tight.

Just to recap what I did to fix the problem:
- Filled the holes in the lead counterweight so I could re-drill them after getting a new E704 rib from Van's.
- Attached the new E704 rib to the existing E703 tip rib. I kept the same tip rib since everything seemed to be Ok on that side.
- Attached the counterbalance skin and the counterweight to the tip rib assembly, marked the lead counterweight using the holes on the front side of the E713 with a sharpee, disassembled everything, and step drilled the counterweight on the drill press  - just as I had done before.
- reassembled the counterweight and tip rib/counterbalance skin, and drilled the holes in E713 to size to match the holes in the counterweight. (Drill to Number 12 initially, but will end up being number 10 for the dimple die.) Used my hand held air drill for this part.Tried my best to keep a straight line....
- Verified the hole on the forward flange of the tip rib side aligned with the hole in the counterweight and the counterbalance skin - it did (Whew! was worried about that one)
- Took my number 12 drill bit on the E704 side, slid it through the E713 skin, through the lead counterweight until I felt is stop against the forward flange of the E704 rib. I did not run the drill while doing this - just inserted the bit to verify it would travel all the way up to the point of hitting the solid flange of the new rib.
 - Then I carefully aligned the drill bit - hedging a bit more with pressure toward the outer edge of the rib flange, and HAND TURNED the drill bit to start a reference hole in the flange, being careful NOT to drill all the way through the metal
- Disassembled the counterweight adn ribs one more time, found the mark on the E704 rib, verified that it appeared to be in the correct place to provide a hole with sufficient clearance for the screw, washer,and nut, and finished drill the hole in the rib flange.
- Reassembled everything again to verify that the screws, washers, and nuts on both sides will attach correctly.
 - Now I just ahve to take it all apart again to countersink the holes in the counterweight for the E713 dimples, which also have to be done. Then I put it all back together again, minus the counterweight, so I can attach it to the E702 spar and the skin.

WHAT A PAIN IN THE ASS THIS IS!

Lastly, back to the trim tab. Started measuring for the riblets using the practice kit ribs I got from Mike Rettig a while back.

Here is the outboard or smaller end of the trim tab - will have to fill the areas with the chipped primer - interesting. A very small riblet goes in this end.

Next is a pic of the practice kit rib. I will use 2 of these and the end of a 703 tip rib to make all the necessary riblets.

Next is a pic of some dimesions that I had ruffed out. I will be changing these slightly after reviewing the pics on Steve Riffe's log. The forward spar of the trim tab is a Z shape, and what you end up doing is trimming these riblets so that the rib web coveras as much of the tip area as possible, while making recesses in the flanges of the riblets to ensure clearance from the trim tab spar flanges.

Steves riblet seems to be a bit longer than the dimension I drew up. It is very close to a tooling hole, so I need to be careful about where to cut the tip off.

Next steps for tomorrow, which will finish up my vacation and holiday time off from work - dimple and countersink the spars, fabricate the riblets and drill the rivet holes, and maybe prime all the parts since the weather will finally be somewhat warm again tomorrow. The last part of the left elevator assembly involves aligning the trim tab, drilling the elevator side of the hinge, and then working on the trim servo mounting brackings and nut plates. Then I still have to roll the leading edges....UGHHHH. It just goes on and on and on.......

Have to stay focused on this to get it done, but I really, really, really want to get started on my Wings.