I took a little break from the trim tab to try my hand at some fiberglass work. Here, I’ve fit the vertical stabilizer tip into place and drilled the holes to full size. The tip was too long, so I had to cut off about 1/4″ (you can just see the blue line near the bottom edge) to line up with the vertical stabilizer joggle.
I also cut a piece of 1/4″ last-a-foam to fill the gap. This stuff is really light, but it’s a bit brittle. This piece snapped while I was trying to fill it. It will epoxy back together though.
Here is the foam epoxied into place in the tip. I left a slight reveal (less than 1/8″) to allow for some filler here since this area needs to be slightly concave to allow for the swing of the rudder.
After researching this issue on vansairforce.net, I decided not to follow the plans again when it comes to the trim tab. The trim tab and left elevator skins come with little ears that are supposed to be folded together to close in the end of the surfaces. The problem is that many (most?) people end up not happy with these bends and either redo them (which would be expensive with the elevator skin) or live with it. The consensus seems to be to just cut off the ears and fabricate little riblets to fit in there. If you’re not happy with how these come out, you’re only wasting a few cents worth of scrap aluminum.
Here, I’ve cut off the ears on the trim tab and I’m ensuring that the cut line is perpendicular to the trailing edge.
I clecoed the top of the trim tab to the bottom of the elevator to mark where the cut line should be on the elevator skin.
Then moved 3/32″ away (the minimum gap between the trim tab and elevator), and marked the elevator skin. You can see that I stuck a couple of extra rivets loosely in the holes for the trim spar to ensure these lines stayed perpendicular to it.
I started by riveting the hinge reinforcement plates and platenuts to the elevator spars. I’m still working on both elevators to save time.
Here is the trim servo supports, back-riveted to the trim cover plate.
And here is the servo, mounted to the supports.
I riveted the root ribs onto the spars. This is the root rib for the left elevator. You can see it has a blunt end where the trim spar attaches.
The instructions are definitely not in the best order here. They have you rivet E-703 (end rib) to E-704 (counterbalance rib) before riveting them both to the spar. The problem with that is that these rivets can’t be squeezed if you do that and must be shot/bucked (probably with a double offset set). Instead, I squeezed these now while they’re easy to reach.
And then squeezed the rivets holding E-703 to E-704.
The elevator horns can now be riveted on.
I added a dab of RTV to the back end of each stiffener pair to tie them together. This helps prevent cracking here according to Van’s.
And the right elevator is complete except for the leading edge rolling.
The right elevator counterweight (shown here on the left) has to get trimmed because the right elevator is lighter (the left elevator contains the trim system, so the counterweight needs to be heaver to balance the left elevator. Trimming this was a pain. I tried the bandsaw, but the counterweight jammed in the blade (and bent the blade). I also tried a hacksaw, grinder, chisel, and file. Nothing worked great, but I eventually got all the metal removed.
Here are all of the parts cleaned and primed, ready to be assembled. I have no idea why Van’s has you build the elevators separately. It’s going so much faster to just build them at the same time.
I haven’t had much time to work on the plane the last few days because work’s heating up. We’re working 7 days a week to get the new iPhone 3.0 software out the door. I need a little break though, so I managed to get a few of the elevator parts ready for priming. Here’s the counterweight skin. I beveled the side and back edges where the main skin overlaps to prevent a bulge in the skin at this spot.
There’s not enough room between the trim spar flanges (partly visible in the upper left) to get a normal squeezer to dimple the rivet holes, so I tried the pop rivet dimple dies. I only got one done before the nail broke (expected at some point). The female portion of the die shot off with blinding speed and it took me about 5 minutes of searching the garage to find it. I think I’ll look for another way to dimple these holes.
A few of the holes in the elevator spars have to be countersunk, but the spar flange is too close. I took one of my extra countersink cages that I picked up on eBay and ground off part of the foot to allow it to get up close to the flange.
I didn’t like the idea of routing the trim servo wires through the hole on the left since the servo shaft (which is threaded) extends through this hole in the full nose-up trim condition. I’d much rather avoid the potential for chafing and drill another hole. Since there was already a lightening hole in the elevator horn, I just drilled a 3/8″ hole in the center of that. I’ll put a snap bushing in that hole later.
These pictures look the same as yesterday, but all of the holes have been drilled. Here’s the left elevator.
And the right…
For a little diversion, I fit and drilled the elevator trim mounts to the trim cover plate. Ignore the left/right measurements in the plans, just visually center the trim servo arm over the cutout and clamp it in place.
I clecoed the counterbalance rib to the end rib and attached both to the spar. Getting the last holes in the spar flange to line up with the holes in the counterbalance rib was a real pain and required several iterations of adjusting the bend of the counterbalance rib flange for that last hole.
Here is the counterbalance skin clecoed on with the counterweight in place. I drilled through the holes in the end for the counterbalance weight attach bolts.
Here is the elevator skin clecoed on. This is the left elevator.
And this is the right elevator.
While I was at it, I clecoed the elevator horns on so that they could be drilled at the same time.
I fabricated a simple bending brake out of a 2×8 and a bunch of hinges. I’ve heard other builders complain that they didn’t get a crisp bend between hinges, so I went a little overboard on the hinges. They were on sale for 96¢, so it didn’t cost much.
After reading the experiences of others on vansairforce.net
, I put the trailing edge up against the hinges and bent the skins basically flat (until the stiffeners were touching the opposite skins). They spring back to roughly where they will sit once the spar is attached. You have to put a surprising amount of force on this. I basically climbed up on top of it and bounced (and I weigh 230lbs). The whole process for both skins only took about 5 minutes.
Here’s what you’re looking for. The skin stays flat right up until the trailing edge radius.
Since I couldn’t rivet last night because of the noise, I got up early and riveted the elevator stiffeners on before work this morning. Here’s the left elevator.
And here’s the right. Near the trailing edge, it was difficult to get the skin bent out of the way enough and still keep everything flat on the back rivet plate. I ended up having to drill out a couple of rivets that didn’t end up flush with the skin.