Monthly Archives: September 2014

It’s beginning to look like an elevator again…

Rivet count: 1833 + 71 new = 1904

I left off getting ready to assemble the trim tab.  Well, I’m still there!  Two issues: I wanted to mix just one batch of pro-seal to glue this up and I didn’t have a #33 bit to final drill the close out tabs and I didn’t have a dimple die to dimple for flush pull rivets.  Sigh.

I did get some work done however before putting the trim tab aside.  I riveted the bottom trim tab skin and the trim tab horns to the front spar.  I primed underneath the horns (a bit of overspray on the blue plastic will disappear when I do final prep).  I did cleco the trailing edge wedge into place to see how much play I had left to see if I can set the trailing edge and then dimple the close outs.  One builder suggested final drilling the close out tabs last to help eliminate twist.  I’m not sure how to do that (drilling is easy, but dimpling would be tough).

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With the trim tab on the bench, I started assembling the left and right elevators.  I had the parts sorted onto my left and right bench to help keep it straight in my head which parts went with which elevator.  I also cleco first the left side and then the right before I go crazy with the riveting in case I did a dyslexic number on the parts.

The first step is to rivet a small gusset onto the left root rib (where it intersects the rear spar).  I had the part and direction marked, so it was pretty easy to drop a couple of 1/8″ rivets in there.

Then the two pairs of tip ribs get riveted together.  Two rivets are 426 flush rivets to accommodate the lead counterweights, but the rest are domed.  I put the domes on the visible interior face since this will be more visible.  It was actually a bit of a tough squeeze to get the rivets there done.  There are two facing flanges (one for each part of the tip rib), so you can’t quite get the yoke over both with the rivet sets in place.  I solved it by sliding the squeezer over the flanges and then inserting the rivet set.  Kept it clecoed to keep the two parts aligned and tight.  Final product seems OK.

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The tip and root ribs then get riveted to the main spar.  The root ribs are a bit tough since they bend inward.  The left one wasn’t to hard (I used my longeron yoke), but I could not get the right one to set.  I switched to my 4″ thin nose yoke which fit in nicely.  You need to watch the rivet call outs in the plans.  The flange on the tip rib requires  a 3/32″, not a 1/8″ rivet.

The front spar gets four doubler plates each of which hold a big K1000-6 (not a K1000-06) nut plate.  I hadn’t prepped these parts, but they were very easy to prepare.  A couple quick passes with a file, a pass through the Scotchbrite wheel, and a quick coat of primer and it was done.  Not as easy was finding the K1000-6 nut plates.  I really bugged me as I could not find it in any of the bags of nut plates.  If you recall, I had the problem before…. With the same part!  That’s because the nut plates (really huge ones) are in the empennage hinge parts bag.  Sigh!

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I had foolishly promised my wife that I wouldn’t work too late tonight, so I just got the next step started.  The tip rib skins wrap around the counter balance and eventually fit under the skins.  I eased the edges beneath where the front spar and tip rib stack on top of each other so that the tip rib skin wouldn’t show a ding where it bend over the edge (and then added a quick shot of primer to cover the bare metal).  The top skin goes on top of this whole stack too!  So I used a file to ease these skins as well (and primed).  Hopefully, I’ll get a nice smooth transition when all is said and done.

So, now at last, the elevators are re-emerging from the pile of parts:

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Next up:  The elevator horns get added to the front spar, the rib halves get riveted to the rear spar, and then the skins start getting back riveted to the rib halves.  The trim tab will wait until I do the pro-seal on the main elevator bodies.  I did some research online and a couple people found that a #40 dimple works well for the #33 pop-rivets (though I still need a 25mm drill bit).


Disassemble both elevators…

Rivet count: 1819 + 14 new = 1833

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Those two little instructions… disassemble and deburr…. It seems like I’ve been doing nothing but that the last couple of build days.  In reality, I’m was also scanning ahead to do the dimpling and priming specified on the next couple of pages, but it seems like my entire routine was to uncleco a part, finish the deburring, dimple, and prime.

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I had pretty much finished the left elevator (except the trim tab) except for the skins and countersinking the trailing edge.  How much work could it be to finish it all up?

The answer, of course, is more than I thought.  As I started to go through the parts more closely, I realized that I hadn’t dimpled the ribs yet.  So I got those done.  The skins had to be smoothed and dimpled, but they also had to be scuffed and masked before priming to leave an area for bonding the foam ribs.  Just lots of details!

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Getting the trailing edges countersunk was a chore because you couldn’t use a standard countersink bit because the cut had to be perpendicular to the face.  Vans suggests grinding down the standard pilot on a countersink.  Instead, I put my 5-bladed deburring bit in a cage and carefully cut each countersink.  The cage kept it perpendicular, but with no pilot I had to watch each cut carefully.

Finally, by mid-day, I had both elevators done.  Yay!

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With all that done, I flew through the next few pages making sure that I had appropriately dimpled and countersunk all the pieces during my look ahead.

At last it was time to do a bit of assembly!  You start with the nut plates in the trim tab motor bracket.  The instructions call for dimpling the skin and countersinking the plates, but the conventional internet wisdom is to use NAS 1097 “oops” rivets.  The rationale is that the only purpose of the rivets is to keep the plate from rotating.  Since they aren’t required for structural strength, anything will do.  The  3/32″ rivets have a tiny head, almost no bigger than the shaft.  I used my deburring bit in a handheld deburring tool to cut the very small countersinks.  The interwebs said “a few turns” would cut it sufficiently.  I found it took some effort to get the cut deep enough (though I was checking depth often with a rivet).  The AD3-3.5’s seemed the right length (confirmed with my rivet gauge).  I found that these were much easier to hand squeeze than to pneumatically squeeze.  The part is very light and a bit awkward to clamp and the rivets are so lightweight that it just worked easier that way.

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The next step is to assemble the trim tab motor arm.  You rivet this using the “double flush” back riveting technique.  The instructions call out a AN426AD3-3.5 rivet, but that was very much too short, so I used 3-4 rivets instead.  The flush look was very easy to achieve on my back rivet bar.

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Looking ahead to how it is actually used, though, it is supposed to have two small bends in the attachment arm (they are marked in the plans).  On my part, they are not bends, but rather a gentle spreading.  I will contact Vans to see what they think.  I can either make the bends myself on my brake (my father-in-law just gave me his old mini-brake.  Thanks Dad!) or get Vans to send me a new one.  Cutting and re-doing is a trivial task.

Then, just when you get back into the swing of assembly, you have to go back and prep the parts for the trim tab.  I pulled out the skins and spars and trailing edge and did the finish work.  Not much to do, actually, just measure and cut the trailing edge and deburr/mask/prime/dimple the other parts as before.

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At this point, the trim tab is mostly ready to go.  Next up, I will continue the assembly up to the point where I need to use the Pro-seal bounding to hold the foam ribs and trailing edge in place.  I would like to do that in one messy batch if possible.