Installed Horizontal Stabilizer Tips – 1.5 hrs

Sunday July 18, 2010

Today I permanently installed the horizontal stabilizer tips. I match drilled all of the holes to #30, then removed the tips and cleaned out all of the chips. Then I dimpled the holes in the skin using my pneumatic squeezer. Next I countersunk the holes in the fiberglass using a countersink head on a manual drive handle. Then I installed the tips using CS4-4 pop rivets.

The fits between the tips and the skins are quite good. The seams are tight and the leading edges line up nicely. So I am thinking about leaving these alone and not filling the seams with dry micro.  I think I’ll move on to the rubber bottom fairing and that will give me some time to think about it.

Hanging the Horizontal Stabilizer – 1 hr

I picked up some straps and hooks from Home depot to hang the horizontal stabilizer from the ceiling of the garage to reduce the risk of accidental damage. At least we won’t trip over it or drop something on that smooth shiny skin with it up there.

Wrapping Up the Horizontal Stabilizer – 6.5 hrs

I was off work today because the contractor was installing our kitchen cabinets and I need to be here to make sure everything was as it was supposed to be. I got started working on the horizontal stabilizer early and the contractor showed up with the cabinets about 9:30 AM. I squeezed the 220 rivets around the perimeter of the skins between checking in with the contractor. Once I had the pneumatic squeezer dialed in with the adjustable set I was getting very consistent nice quality rivets. I had about a dozen that sat slightly high in the countersink so I drilled those out and reset them. Fortunately I am getting good at drilling out rivets and was able to do them without enlarging the holes.

Then I put in the four blind pop rivets from the rear spar into the HS-708 ribs and set the four rivets between the HS-603PP rear spar and the HS-706 ribs. With that done I removed the blue film from the exterior of the skins because Vans recommends not keeping it on long term since it can get hard to remove over time.

Here she is –

That deserves another shot from the other side. The mirror-like skin looks gorgeous!

Here is the center section which eventually will mate to the aft fuselage.

If you look closely you will see 10 missing rivets. That’s not an error. The fairing between the HS and the rudder will install at those locations some day in the future.

At last the horizontal stabilizer is done, or at least I thought it was for a moment. That is when I saw two clecos sticking out of one end from the HS-708 rib. I forgot to put in two AN470D4-4 rivets into the front spar. Drat! The rear spar blocks access to buck those now so I had to use two blind rivets instead. Fortunately the loads are very low there at the tip of the HS so strength won’t be an issue and the fiberglass tips will eventually cover them, but it still bugs me. Again the lesson is that when you break the normal assembly order you run a greater risk of missing a step.

Nearing the Finish on the HS – 1.5 hrs

The finish line is near on the horizontal stabilizer. After priming the VS parts, I started to cleco on the rear spar on the horizontal stabilizer in preparation for final riveting on the perimeter. Then realizing that this was my last chance to check the inside cross rivets so I put on my quality inspector hat and rechecked every rivet. Out of about 120 rivets I found about 8 that were right at the low end of the spec range on diameter on the shop head (.122 dia min) so Denise and I gave those a few more taps with the rivet gun and bucking bar to put them closer to the .135 diameter nominal  for a 3/32 rivet.

Then I made sure the inside of the HS was clean and I cleco’d on the rear spar. Tomorrow I can start riveting the perimeter. And that will complete the horizontal stabilizer (except the tips which get added later).

Back on the Horizontal Stabilizer – 7 hrs

After a long hard week at work and numerous distractions related to our kitchen remodel I was able to get back onto the horizontal stabilizer today – or more accurately, Denise and I were able to do a good bit of riveting. It truly is easier and more accurate to buck rivets with a helper. Denise is getting quite consistent driving the rivet gun with the flush set and I buck on the inside of the airfoil with the tungsten bucking bar taped to a 1×2 about 18 inches long. By leveraging the 1×2 off a stack of scrap lumber on the bench I can get the bucking bar flush to the rivet shank and apply the right pressure to form the shop head in 6 -8 hits of the gun. And the rivets are consistently well formed. The only problem is occasional scratches caused by the bucking bar rubbing against the web. So I have to touch up the primer in a few places after we are done.

We completed what I call the interior cross – that is the rivets along the front spar and the center rib that must be bucked from the inside of the airfoil from the aft end of the open skins. We did the right bottom side, left top side, and left bottom side. Since we had done the right top side a few days ago, that completed all four interior crosses. There are also three blind rivets on the interior between the HS-707 and HS-708. I installed those on the left side only since I had installed the three on the right side last week.

Here is a photo of the horizontal stabilizer with the interior cross rivets completed. Notice that clecos are only on the perimeters. Next will be installation of the aft spar.

I also broke down the parts of the vertical stabilizer which I match drilled last weekend and deburred, dimpled, and countersunk in preparation for priming. Here are the internal ribs and spars after preping.

Tomorrow I hope to get these primed (if I have enough primer on hand). I also still have to dimple the skin. Then I’ll be ready to start final assembly of the vertical stabilizer.

Bucking Rivets in Horizontal Stabilizer – 1.5 hrs

Not much time to build tonite but Denise and I started bucking rivets on the Horizontal Stabilizer right side. These are the internal rivets for the skin before the rear spar is installed. My new nickname for Denise is Rosie (the riveter) because she is doing a great job driving the rivet gun while I buck. Not a single bad rivet in he bunch. That includes the row along the front spar and along the HS-708 rib on the right top side. Ok, that’s only one quarter of the internal rivets but it was a good start and none had to be drilled out and no dings on the skins.

I found that by taping the bucking bar to a 1 x 2 piece of lumber I could align the bucking bar to the deeper rivets easily and apply the pressure needed to buck the rivets in about 6-8 hits at 40 psi. I used a stack of lumber pieces to make a fulcrum to position the bucking bar surface flush to the rivet shank and apply pressure with the leverage. Here is the cheapo bucking bar tool.

We also riveted the HS-707 rib into the left side skin top and bottom. We were able to shoot all solid rivets on both sides by working to get the best angle on the job for the bucking bar. Here is the left side skin with HS-707 installed.

Then I cleco’d the left skin onto the front spar skeleton (hopefully for the last time). Now just three more sets of internal rivets before installing the rear spar.

Horizontal Stabilizer Final Assembly – 6 hrs

Since I completed the riveting the rear spar last night, this morning I started on the final assembly of the front spar.

I squeezed the rivets for the front spar halves to the HS-710 and HS-714 reinforcement angles. Here’s a shot of the aft side showing the four flat head rivets in the center and the other universal head rivets.

I had to keep reminding myself not to rivet where the ribs will attach. Here is the front side showing the shop heads.

Next, the HS-404 and HS-405 ribs were riveted to the front spar. I couldn’t use the squeezer on the inner four rivets so I bucked them with a cupped set and my tungsten bucking bar. That dang cupped set jumped off the head on one rivet and left a few shallow scratches on the HS-702 but nothing major. Gotta watch that. I touched it up with a little primer and now you can barely see it. Here it is before the touch up.

And here it is after.

Next step was to install the HS-702 rib into the skin. This is because the interior of the rivets will not be accessible after the front spar is installed. Installing it first allows access to the interior to buck solid flush rivets. I’ve been a little anxious about bucking my first flush rivets on the skin since I tried the first few on the training kit. I realized that a helper is valuable for bucking so I trained my wife to use the rivet gun with the swivel flush set and we shot the six on the upper skin surface. Five of the six turned out great. One had poor grip on the bucked surface because the rib flange was not flush against the inside of the skin. So I had to drill that one out and we shot it again. But before shooting, I used the pop rivet dimple set to squeeze the skin to the rib. That seemed to help and the replacement rivet looked good.

Here are the six on the top surface of the skin.

Then I flipped the skin over and we shot five of the six. Since there is less room to manipulate the bucking bar on the second side I didn’t see an easy was to buck the one closest to the leading edge so I used a blind rivet on that one hole. Since the instructions permit using blind “pop” rivets for all six of these, I thought five out of six solid is not bad. And the blind rivet is on the under side of the HS.

By the way, since I shot primer inside the skin with the blue film on but strips remove I got a well defined primer pattern which you can see here.

Then I inserted the front spar and installed blind rivets between the HS-707 and HS-708. Here is the end result, ready for more skin riveting which will have to wait until Denise is available again.

Back to the Horizontal Stabilizer – 5.5 hrs

After that little detour to work on the vertical stabilizer, I got back onto the horizontal stabilizer.

1. I took both skins off and disassembled the ribs and spars on the left side.

2. I deburred the edges of the skins and completed dimpling of the left skeleton ribs, spars, and skin.

3. One final check for rough edges and then it was into the sink with the ribs, spars, and stiffeners for a scrub with Simple Green and a scotchbrite pad. A final rinseand dry  prepared them for priming.

4. I primed the left side ribs, spars, splice angle, reinforcement angle, and both reinforcement bars using Dupli Color Self Etching primer from a rattle can. It’s green.

5. I also removed the blue film on the left side skin in strips along the rivet lines. And I shot a light coat of NAPA 7220 Self Etching Primer along those line on the inside of the skins where they will mate with the ribs and spars. This is probably overkill since the skins are Alclad. But I did it anyway. I like the Dupli Color spray pattern better. It seems finer and more uniform.

6. After about 3 hours of drying time I laid out the parts for the rear spar and began riveting the reinforcement bars. Here it is cleco’d together before riveting.

One minor pain was removing all those little stickers Vans puts on the hinge brackets for identification. They won’t hurt anything if I leave them but my conscience won’t allow it. I had to peal each one off with my fingernail then use a little MEK to clean off the residual adhesive.

7. I put the factory heads on the spar side which is the thinner material so all the shop heads are to the aft. Here is a close up of some of the rivets. I used the pneumatic squeezer and the longeron yoke and all but one of the reinforcement bar rivets came out pretty nice. That one had a slanted shop head so I drilled it out a re-shot it.

The first rivet I shot on a HS-413PP bracket buckled badly. When I checked the length of the rivets it was clearly too long. The plans call for an AN470D4-5 but that leaves way too much shank exposed. So I switched to an AN470D4-4 which was still on the long side but worked much better. I had to be really careful squeezing the -4 rivets because one of those bent over also and I had to drill it out.

8. Then I installed the center bearing assembly on the rear spar using the AN bolts, washers and nuts and torqued each one to 25 in-lbs per Vans guidelines. I used the top end of the range because the running torque of the lock nuts reduces the bolt preload a bit.

Here is the completed rear spar assembly ready for final assembly of the horizontal stabilizer.

Match Drilling Left HS Skin – 1 hr

Got home late tonight from work. All I had time to do was cleco the left skin onto the HS skeleton and match drill all the holes into the new HS-702 spar. Jobs do get in the way of progress sometimes.

Received the New HS-702 Spar – 2 hrs

2/2/2010

The replacement HS-702 spar came via FedEx today. It was well packed in a heavy duty cardboard tube. I laid out the markings for the bend line and strain relief notches and checked them against the old spar just to make sure I didn’t measure something wrong. Then I drilled the relief radius with a #30 pilot drill followed by the unibit to 1/4 inch diameter. Then I snipped away excess material leaving at least .060 along the border which I cleaned up with the belt sander followed by the scotchbrite wheel.

I clamped it to a wood block and after measuring three times the location of the hole and checking the drawing four times, I drilled the hole for the trim cable.  That is where I screwed up last time. I clamped it between two wood blocks and made the 6 degree bend. Last but not least I dimpled the two inboard most holes.  Here is the result.

That funny band down the center is where I removed the blue film and deburred it with a scotchbrite pad. The areas to either side are the pristine areas after I removed the rest of the blue film.

I removed the old HS-702 from the horizontal stabilizer skeleton and put in the new one. Everything seems to line up perfectly so I match drilled the rest of the holes to the skeleton. Finally I removed the HS-710 and HS-714 angles and countersunk the aft side of one hole on each to match the new spar dimples. Here is a shot of the reassembled skeleton.

All that remains on this vignette is to put the left skin on and match drill skin holes to the new spar. Then I’ll be ready to disassemble the left side, final deburr, clean and prime.

For the record, here is a close-up of the center spar region showing the trim cable hole right where it should be. Note the green primer on the right HS-702 spar and rib.