After trying to adjust the skins to eliminate the “banana” curve at the end of the right skin, I discovered other builders had also run into this, and it was because the skin was bent incorrectly. Worse, you can’t really fix this either.
As it turns out, I had another right skin that came with my original kit that I rejected for missing a line of rivet holes for a stiffening channel (it looks like my kit had a Sling 2 skin instead of a Sling 4 skin, since the Sling 2 doesn’t have this stiffening channel). I decided to test fit this skin to see how the end lined up. As luck would have it, this one lines up much better than the replacement skin.
So, I decided to measure where the missing holes needed to be, and simply drilled the original right skin.
With that problem out of the way, I was able to finish clecoing and riveting up the skin. I finished one side and will complete the other side next.
At the moment, I have the elevator temporarily attached to the horizontal stabilizer with some 1/4″ bolts, and I’m using clamps on the ends to keep the elevator horns lined up perfectly while I rivet the skin.
One of my fellow builders (Thanks Pascal!) recommended temporarily attaching the elevator to the HS to make sure the “horns” (end part of the elevator) line up perfectly with the HS skins before nailing the elevator skins down. The correct hardware to attach these two parts is AN4 bolts, which I don’t have yet, but I used some common 1/4″ bolts I had on hand. I then used some clamps to line up the horns to the horizontal stab.
I found that I need to adjust the skin to make things fit right. One of the folded ends of the skin doesn’t look quite straight, it looks like the bottom-left diagram in the picture below. The manual says to remove the clecos, adjust skin and try again. I’m not quite sure how this will help though – the holes are drilled pretty tight, and don’t leave much room for adjustment. I’m thinking that I will use a reamer to open the holes up to #31 size and then try again.
Here’s an in-process photo. This thing starts to look much bigger when you put the parts together!
I’m continuing with closing out empennage tasks; like the rudder skin issue I described last week, I also had a problem with one of the elevator skins from the original kit I bought. The skin was missing a row of pre-drilled holes for a stiffening channel, and I couldn’t see an easy way to match-drill in the right place, so TAF sent me a replacement skin a few months ago. After prepping and priming the skin Tuesday night, I clecoed it together Wed night. So far, so good, but I have to pay attention to the alignment of the left and right ends to make sure they align perfectly – I’ve seen other builders use a laser level and/or a digital inclinometer to achieve this, and I’ll do the same.
These empennage parts go together so much faster than the fuel tank! With that being said, I’m anxious to get back to the wing. I’m ready to complete the close out of my left tank, after which it must be attached to the wing so that the sealant sets in place correctly. We’ve had a long stretch of cold weather in NH lately so it’s too cold to work in the garage right now. The data sheet for the Flamemaster CS3204 sealant doesn’t list an acceptable temperature range for curing, it just says that it cures at room temperature and will take longer at colder temperatures.
Good productive weekend! I primed and started assembly of the elevator, starting with the trim tab.
I ran into a hole misalignment with rib #1 on both sides, looks like other builders have encountered this too.
I decided to use a #20 drill bit to fix this – the hole misalignment was too great to use a reamer.
After drilling the holes, rivets went in ok.
I goofed up a little riveting together these clevises to the elevator brackets (see pic below). It seemed like it didn’t really matter which way to put the rivets in, even after I had everything clecoed together. But after I did one side, l discovered the “shop” side of the rivet sticks out quite a bit on these stainless steel rivets, so I switched direction for the other clevis. In the next step, the AN3 bolts go into the other holes as seen in the photo, but getting the bolts tightened was a little tricky on the side where the shop side of the rivet was sticking out, making it harder to get a socket on it, but ultimately a non-issue.
Next, it took me a little bit to figure out the right way to fit this channel into place – it’s a really tight fit! After looking at photos from other blogs, I figured out the way I originally thought was correct – it fits over the channel that joins the spars, but under the lip of the spar. I had to use a C-clamp to squeeze it in so that the holes would line up with the spar and doublers – and even then I still had to use a reamer to get the holes clean enough to install rivets.
Once all together, this is a pretty stout/strong structure.
A few more parts to rivet on, then I’ll be ready for skins.
This little plate is to mount the trim servo, which I already purchased from Aircraft Spruce.
I’m considering buying a second rivet gun. As much as I like my Milwaukee, it would be nice if it were easier to change the nose piece bit – it’s threaded and uses different sizes for different rivets, just like other rivet pullers. The assemblies I’ve done so far use both 3.2 and 4.0mm rivets, and I find myself having to switch the nose piece pretty frequently. It only takes a minute to switch, but it would be even faster to just reach for a different tool.