More Trim Tab Work

August 17, 2010

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Well, before I can dive into the wing, I need to finish up the trim tab. All that’s left is to fabricate two riblets, get everything prepped and primed, and then rivet the tab together.

First, let’s get some riblets made up. Just like the elevator riblet, I started with some thick paper.

I used the packing list envelope from the wings, because it was literally right in front of me when I started.

I got the larger one cut out of 0.025″ aluminum sheet pretty easily, and the first try fit like a champ. I moved on to the smaller one, hoping for similar luck.Fast forward a couple minutes (many minutes!)…

Can you say "third time is a charm?"

Nope. Third one wasn’t good either.

Let's try again (fourth time). I just couldn't get the bends right.

That one worked. And of course I forgot to take a picture.

I drilled a couple holes in each riblet through the skin.

Finally, fourth time is a charm.

Wuhoo, let's get this tab finished.

But, it was getting late, and there were a couple of puppies somewhere that needed attention. (Turned out, they were asleep when I went inside, and I got growled at. Thanks, puppies.) Before I headed inside, I disassembled the tab and pulled out the wing spars to inspect.

Tab components, ready for cleaning and priming.

After looking the spars over, I found many places where the spars had been “polished” with a scotchbrite bad to work out small scratches. It seems that everyone has these, and is no cause for alarm.

On the other hand, I found some bad juju. This is a closeup of a couple dings that look like something bounced on the spar. Keep in mind, that hole is a #40 (3/32″), so these are really small.

Still, that's not good.

Whoa. What. Is. That!?

Holy frijoles, Batman! That is a huge dent in my spar flange!

Here's a closeup of the dent with a straightedge held over it.

Another angle.

I took a couple pictures of the underside of the flange. I tried to use the light to demonstrate the distortion.

That curved white streak is actually the light reflecting off of some spider cracks in the anodizing.

Here's another angle.

Not really related, I just snapped a picture of the spars laying on the table.

At least they look pretty.

1.5 hours on the trim tab today. I’ll email Van’s first thing in the morning about the spars and then post what they say.

I’m pretty disappointed though. Nothing could create that dent without making a big noise, maybe something being dropped or falling over. Which means someone probably knew it happened and didn’t say anything, or the inspection process didn’t catch it. Either way, I’m not super excited. I’m guessing it wasn’t Vans’ fault, but hopefully they will make it right.

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Posted by Andrew

LH skin dimpling, some HS riveting

January 9, 2010

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This morning, I snuck out into the garage and starting dimpling the left hand HS skin with my new (borrowed) c-frame.

After thinking about the setup and trying a few things, I quickly realized I wanted the female dimple die underneath and the male dimple die on top.

I set up the skin on 3 2x4s (I haven’t built a dimpling table yet because I wanted to see how I liked doing it) which was less than a 1/4″ above the female dimple die. Then I basically moved the c-frame around until the male dimple die was lined up (this way I don’t scratch the skin with a male dimple die while trying to locate the hole from underneath, like some builders do). Then I held the male dimple die down into the hole and…WHACK! Perfect dimple. I am far happier with these dimples than the pop-rivet dies. Keep in mind here, I am dimpling with the standard spring-back dies here, not the tank (deeper) dies.

Here's my setup for now. I like this because you move the c-frame, not the skin.

After finishing each row, I put a line of blue painters tape on the outside of the skin. I learned on the practice kit to protect whatever I didn’t want to scratch. The tape will come off just before riveting.

Blue tape on the outside of the skins. Hooray protection!

After I finished both sides, I scuffed up the internal lines, cleaned, then primed the inside of the left HS skin.

Here's the inside of the left skin, all suffed up, ready to prime.

While I waited for skins to dry, I riveted together HS-705, HS-702, and HS-704, but only the middle two holes. The rivets didn’t bend over, per se, but set a little crooked. (My fault for not keeping the squeezer steady.) I drilled them out perfectly, and then decided shooting them might be a better idea. After practicing with a piece of scrap for a minute, I actually ended up shooting these rivets. They look really good.

Shop head picture. Rivets 7 and 8.

Machined head picture. This just looks good.

This is not the order the directions has you rivet, but I was getting antsy to get some primed pieces together. Notice I didn’t slide in the HS-710 and HS-714 yet (still need to finish those), as you can set HS-404 to HS-702 to HS-405 without them. Then, it is off to run some errands.

When we got home from running some errands, my latest Avery tool order had arrived. Finally, a scotchbrite wheel! 6″x1″x1/2″ CP-7AM “Cut and Polish” Medium wheel. Also, I’ve heard some good things about the Permagrit line of products, so I picked myself up one of the 12″(?) ones. Fine on one side, coarse on the other, flat (I heard not to get the curved (convex) one.. Much better for making a straight edge than my regular file.

More tools!

First thing after mounting the scotchbrite wheel, I finished the edges of HS-710 and HS-714 with the wheel. So easy. I should have ordered the wheel at the beginning. (Serves me right for trying to piece together a toolkit instead of buy one all at once. I thought the scotchbrite wheel was a luxury. It is not.) Then I countersunk the holes in HS-710 and HS-714. I had done this before, but sized the countersinks perfectly for a AN426AD4- rivet. When you cleco the dimpled HS-702 front spar to either piece, the spar doesn’t sit flush, so you have to enlarge the countersinks.)

Enlarge countersinks. Check.

Then I finished surface prep, cleaned, and primed those two.

While waiting for the primer to dry, I clecoed HS-707 (leading edge “middle” rib) and HS-706 (tip rib) to the left skin to get in the mood for riveting. The girlfriend and puppies are taking a nap, so I’ll have to come back to this later, but I’m getting excited to start skin riveting.

HS-707 and HS-706 all clecoed to the left skin and such.

Anyway, I put in a few minutes of right HS skin deburring, scuffing, and dimpling before coming in for the day. (Notice I decided to scuff the interior of the right skin before dimpling? It’s easier to scuff the skin without all of the dimples getting in the way. It’s these little things that will save me time the second time around.)

Let’s see. 9am to 11am, 2pm to 4pm. 4 hours today.

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Posted by Andrew