Empennage

Short night. After thinking things over from last time, I did decide to go with temporarily blind riveting the tip in place for the next batch of micro. First I removed the tip and applied clear packing tape to the inside of the rudder flange, wrapping it around to the outside to protect the metal surfaces here. Then I poked through the rivet holes and installed my cheap hardware-store rivets. One bit of fun I had from this was that about half the rivets had their stems break off above the rivet head. I was able to trim those off with my flush cutters, to avoid them poking through another layer of tape I put on top of the rivet heads.

Here it is all taped up and ready to roll:

Then I got another batch of micro mixed up. Learning from my last attempt, this time I didn’t try so hard to make the mixture super stiff, in the hopes that it would go on better. Working the mix into the interface gap went pretty well, but trying to put a good layer on top of the tip went about as well as last time. It’s just really hard to spread this stuff out without having it stick to the squeegee and come off the workpiece. I ended up having better results spreading it with a wide popsicle stick, and then I ended up sort of massaging it around with a moistened finger to make things look a little less horrific. But I think I have enough material here to work this down to final shape once it cures, even if it does still look atrocious right now:

Finally, before calling it a night, I peeled off my top layer of tape, leaving a nice clean line at the edge of the tip. This interface should look good with just a little sanding touch-up:

So now I wait until I can sand some more. And maybe next time I’ll try keeping the micro mix even wetter; I think there just still be a middle ground here I’m not finding yet. Though I also kind of feel like trying to spread the stuff on a tight curve like this tip maybe doesn’t help.

OK, the arctic front is behind us and I can no longer use the cold as an excuse not to go work outside. Finally, it was time to take that globby mess I made last time around and see if I could turn into something nice. I’m starting to wonder if this is just a normal part of the process, that everything looks horrific when the micro is applied.

Anyway, just like last time it took quite a bit of time sanding and checking and sanding some more and rechecking, but eventually (ie after about an hour and a half) I had a nice pleasing shape:

In the course of all that sanding I removed all the major surface voids, but there were still a fair number of smaller air bubbles and pinholes that had been exposed. So for the last part of the night, I mixed up another batch of micro and applied a skim coat over everything to get all those holes filled. While I was at it, I did the same thing to the back of the stab tip, since it had the same issue and I was going to have a ton of extra micro. So this gets to cure overnight and get sanded again tomorrow, then hopefully it’ll be time for filler primer and one last sanding:

The odyssey of the rudder tip continues! I’m starting to become amused by how much time I’m spending on this, though I figure future parts work should go much faster since I’ll know better what I’m doing.

Tonight I sanded the tip down yet again, after last night’s attempt at filling pinholes. Unfortunately, by the time I sanded it back to shape, I uncovered…more holes. It would seem that using micro to fill pinholes isn’t the best approach. So I went back and reviewed a bunch of threads on VAF and decided to take a different approach, namely using a few raw epoxy skim coats to fill the holes. This ought to work better since the epoxy will be a lot less viscous and more apt to fill holes rather than just bridging them.

So over the course of a few hours I applied three skim coats, allowing each one to tack up for about an hour before adding the following coat. Hopefully this will give me a nice hard shell that I can sand down (again) to a nice smooth finish and maybe then I can finally spray some high build primer and think about finishing these things up.

In the meantime, things are looking nice and smooth after the third and final coat:

So tonight after doing a bit of post-work flying, I got to sanding down my newly-epoxied tips. One immediate problem I had were some runs in the epoxy; it seems my attempts to squeegee off all the excess weren’t good enough. One recommendation for this procedure was to use a nappy paint roller to remove excess, but I didn’t have one so I tried the squeegee method. That, in turn, made sanding a little more fun than it needed to be, and I definitely went through the epoxy shell in a few places. Still, everything felt nice and smooth, so after fine-tuning and doing a final fit check, I decided it was time to shoot filler primer.

Here are the pieces after I shot a couple coats. One thing you might notice on the far left of the rudder tip is…a good-size pinhole. And it’s not the only one. The stab tip has a couple as well. Looks like I’ll be sanding this primer right back off and doing even more epoxy work. Maybe a trip to the hardware store for some paint supplies is in order tomorrow…

OK, so yeah, the fun times keep on coming. First thing today I set about sanding off all that filler primer I shot Friday evening. That turned out to be more fun than I expected – that stuff really loves to clog sandpaper. I was taking lots of pauses to knock the crud off my paper, over and over again. But finally I got it all removed from both fiberglass pieces – well, mostly. There were some low spots where a layer of primer remained, and I decided that was fine since I’d be covering the whole thing with an epoxy skim coat again.

And so the epoxy dance began again. The idea here is to lay on a series of coats to build up a little thickness, and also to end up with a textured surface to provide a sanding guide (eg you sand the skim coat until the texture goes away). So you mix a batch of epoxy, coat the piece, squeegee most of it off, and then use a roller to even everything out and apply some texture. Then you let that coat tack up (about an hour or so in the current cool temperatures), then repeat this a couple more times.

Now, here’s the fun I had with this procedure today. First off, my nappy paint roller shed a fair bit of junk into the epoxy. That was almost enough to make me call it a day again, but I decided to soldier on, figuring I’d be sanding this down anyway. I guess there are worse things in the world than having odd fibers under the primer. Worst case, I sand it all off (again) and repeat this process (again). I think part of the problem was that the low temperature made the epoxy a lot sticker than it would have been otherwise.

The real fun came when I went out to apply my third and final epoxy coat of the day. I’d mixed up a batch, painted it onto the stab tip, and was just getting started on the rudder tip when…I bumped the stab tip accidentally, sending it off the workbench and onto the floor. Which meant that that epoxy I’d just laid on picked up all the dirt and random stuff on the floor where it landed. At first I tried wiping it off with a dry paper towel, but that wasn’t removing stuff too well, so then I switched to a towel soaked in acetone – which works well for cleaning up uncured epoxy. That did a good job of removing the epoxy I’d just put on, but I think it also removed some of the previous two coats. Kind of hard to tell. In any case, about all I felt I could do was to go ahead with that final coat of epoxy and hope it was enough for sanding later on.

Later, I went and reread some of the VAF fiberglass info, and another recommendation from Dan Horton (a guru-level composite guy) was to skim coat with a different product instead of raw epoxy. System Three Clearcoat is mainly used for waterproofing wood, but according to him a single coat goes in nicely, lays itself down smooth, and has a long enough pot life to have good working time. So I ordered some of that stuff, and will probably try it out the next time I need to shell out a fiberglass part. The whole half-day odyssey of multiple epoxy skim coats just isn’t doing it for me.

Now, let’s just hope that I won’t be trying that stuff on these same stupid tips. I’m really hoping that I can finally get these parts done and mounted, and move on to something else, maybe try that new epoxy stuff on the rubber bottom cap. At least with all this learning I know that the micro I’ve put on there needs more finishing before I shoot primer or anything like that.

Not much to write about tonight. I spent about an hour sanding down the epoxy skim coat on the two tip pieces. So far it looks like the bits of fiber embedded in the coat aren’t a problem, everything sanded down nicely to a slick finish. I wanted to go ahead and shoot primer again, but it’s been super humid today and so conditions aren’t really that great. I’ll wait until it dries out some tomorrow instead.

I also poked at the horizontal stab tips some more too. I think I’m going to try just drilling the mount holes, clecoing the tips in, and see if they get pulled decently into alignment. If that doesn’t work than I may see about adding a rib further forward in the tip to spread it out, in addition to the rib closing out the rear of the tip. Getting just the right fit won’t be a lot of fun but I think it’s a better option than something like splitting the tip and rebuilding it. Hopefully it won’t be necessary though…

Notably, this entry actually covers work done over a couple days – I did bits of work on the rudder tip over the weekend, but at some point it seems absurd to keep making short entries and having to invent new title variations. Hence me combining them instead.

After sanding the epoxy skim coat, I shot filler primer on the tips once again. This revealed a few remaining pinholes in both pieces, but this time, instead of doing a big sand-down operation, I mixed slightly wetter micro and worked it into each pinhole just using a finger, leaving a bit of excess around each spot. After that cured for a day, a quick bit of sanding smoothed everything out, and I shot primer yet again. Finally, at this point, the vertical stab tip was pinhole-free, but I found a few more stragglers on the rudder tip, so I repeated the same procedure again.

As of tonight, the rudder tip was also pinhole-free, but I wanted to do a bit of touch-up on the flanges. The “step” where the flanges begin was uneven in some spots due to buildup from my multiple epoxy coat applications, so I went to work with a bit of 120-grit on a popsicle stick to clean those up a bit and make sure the flanges were nice and crisp. With that done, I shot primer…yet again.

As primer tends to do, it highlighted a new problem I created during my flange work. Looks like I got a little overzealous with the paper here, and now I’ve got a new groove to deal with:

That’s probably fixable with a touch of micro – or maybe I should just go ahead and get some regular old filler for this stuff instead of continuing to make batches of micro and then throwing away 99% of them. Anyway, the rudder trip farce keeps going…

On the other hand, I’m feeling good enough about my fiberglass learning to get going on the horizontal tips. I laid out the rivet holes on the stab and got those drilled in assembly with the tip pieces. For the most part, they seem to fit pretty decently with just the cloches holding them in place, but I think I’m still going to end up adding some support further forward to help them conform a bit better. I also expect that I’ll end up building them up a bit to get a nice smooth transition from fiberglass to aluminum…here’s hoping that process goes a lot more smoothly than the vertical stuff.

Next up will be trimming the horizontal tips and adding the closeouts on the aft ends…then there’s glassing in the elevator counterweights…plus continuing to bang on that rudder tip…

So it’s been another batch of cold days, which has kept me from really getting into any work, but I did find time a couple nights ago to pick up some actual body filler to use for pinhole filling and other minor touch-up work. Tonight I made the first use of that by mixing up a small batch and using it to restore that groove I accidentally cut in the rudder tip. Also, another nice touch with the filler is that it sets up a lot faster than micro – the touch-up I did was sandal within an hour or two. That, in turn, allowed me to get my sanding done a lot sooner, and I even shot a light coat of primer just to get a better look at any imperfections. The whole piece needs maybe one more overall sanding and another coat of high-build, but I think at that point these will finally be ready to rivet.

In the meantime, I got back to work on the horizontal tips. The stab tips that I drilled last time needed to be trimmed to length; I made some starting marks last session and tonight extended those around the pieces and got them rough-trimmed and sanded to shape. A test-fit on the actual stab allowed me to finalize the shape and check fit against the elevator tips as well.

Next I worked on cleaning up the elevator counterweights. These are going to get wrapped in fiberglass, but before that can be done the shape needs some fine-tuning to match the counterweight skin. I spent some time working on those with a file, giving them some nice rounded edges, as well as a little inset compared to the counterweight skins, to allow for the eventual glass layup.

Then it was time to prep the elevator tips for glassing in the counterweights. As provided, these pieces are a bit long, actually extending past the counterweight itself. Some trimming is required here before getting to the glassing; here you can see the mark I made about 1/4” back to use as a trim reference:

After extending that line all the way around, I trimmed the tips, then went to work sanding a nice taper to the cut edge. This taper will allow for a good solid scarf joint with the glass plies I’ll be adding:

Now that the counterweight is exposed, I can also see that I’m going to want to work on the stab tips a bit too. The gap is nice in the skin area, but tapers a bit with where the actual weight is. I suppose I could trim the counterweight a bit, but I think it’ll be easier to get a nice edge by working on the tip instead. I’ll be wanting to get that done before I go to work adding glass here.

Also, I still need to drill the elevator tips to the elevators; obviously I’m going to want those clecoed in place before I start adding glass plies. Having the whole thing move around wouldn’t exactly make for a nice shape…

The good news is that it’s warming up again this week, so the weather should be good for getting this glass work done.

That title’s not entirely accurate, or at least it’s not the full story, but hey, it captures the broad strokes. I started off giving the vertical tips some attention again, giving them a good sanding to remove the last few imperfections, then shooting some more primer. For once, I didn’t immediately see a new flaw with fresh primer, so I think that odyssey is finally coming to an end. Once the primer has had a day or two to cure, I’ll drill the mount holes to final size, dimple and countersink as needed, and get the blind riveting done.

But the real work tonight was on the horizontal tips. First, I turned my attention to the gap issues I mentioned last night. Rather than simply sand the horizontal tips to match, I decided to take a close look at the elevator counterweights. I used a square to evaluate how well the counterweights matched the profile of the counterweight skins, and there were some irregularities. This probably isn’t too surprising, as the lead weights don’t exactly seem to be precision cast or anything.

Anyway, I ended up doing some more filing on the weights to shape them more to my liking, both getting the profiles to match and rounding the edges a bit more. Once I was satisfied with those, only then did I sand the horizontal tips a bit more to get the gaps nice and even. It’s also worth noting that this sanding still won’t be setting the final gap. As I did with the vertical, once I’ve built up the elevator tips and closed out the stab tips, I’ll wrap sandpaper along with gradually increasing backer material around the front of the elevator, and swing the elevator to get a really nice and even gap, as well as a slight concave profile to the back of the stab tip.

That’s down the road, though, for now I have a nice-looking gap as things sit:

Also visible in this photo are clecos in the elevator tip. I clamped those and drilled the initial mount holes tonight as well. For the most part I’m OK with the gap at the base of the tip, but I think I’m still going to add some micro along the interfaces to make things nice and tight. it also looks like I’ll need to work the elevator skins a bit to get them to mate better with the tips.

It was still too cold to really do any glass work tonight, but I did decide to go ahead and make the balsa inserts that will close out the stab tips. I discovered that, while folks seem to recommend cutting balsa wood with a hobby knife, in fact a metal blade on the bandsaw does a much nicer job. As before, after rough cutting the pieces it just took some trial and error, removing material with 40-grit sandpaper, to get a nice snug fit. Hopefully tomorrow it’ll be nice enough that I can get these closeout pieces bonded into the tips.

Well, I almost talked myself out of working on the horizontal tips tonight, since it’s dropping into the 40s later, but eventually I decided to do it, and just bring the heat lamp into play if necessary. First up, I actually needed to fine-tune my balsa inserts a bit more. One thing I noticed as I was finishing up last night was that the horizontal tip profile didn’t match the elevators very well – it was a bit fatter not too far from where it joined the stab.

One thing I’ve learned is that these gelcoat pieces can be coaxed into a more permanent shape change by stressing them and leaving them that way for a bit. This is, in fact, how I handled these same pieces not fitting the stab curve very well – I stuck little popsicle-stick spacers in to spread the pieces to fit, and found that after a few days they were staying in that shape.

So last night, before quitting, I put a clamp on each stab tip to squeeze the open end to better match the elevator, and left those overnight. Today when I removed the clamps the tips stayed where they were, and matched the elevator profile much better. But that did change the shape of the open end, so I had to tweak the balsa plugs a bit.

After that was done, I got to work bonding the plugs into place. One thing I learned after closing the vertical stab tip was that it would have been better to lay up the glass cloth reinforcement over the wet flox mixture, rather than doing two separate work sessions. Makes sense – having the still-runny flox mixture under the glass means it’ll make much better contact, rather than trying to shape it around dried flox.

The concern I had with this was that without the plugs bonded in place, I was worried they’d move around as I was working the glass plies into place and wetting them out. That was easily solved by using a spring clamp on the open end of each tip after placing the plugs with the flox around them. The clamp also provided a handy handle while working with the pieces:

The fun part about working inside these tips is trying to wet the glass out without making too big of a mess. It seemed unavoidable to have an excess of epoxy end up inside, even when I tried hard to use the excess for wetting out. If I’d let the tips cure in the position shown above, that wouldn’t have been too bad, just a bit of extra epoxy weight – but these needed to be clecoed to the elevator while curing, to ensure that the whole assembly cured up nice and square. The last thing I wanted was epoxy running out for the tips and gluing these unfinished tips to the stab, which is why I topped everything with the peel ply. This isn’t really required here but it’ll help keep the excess epoxy from going anywhere it’s not supposed to.

The last step for the tips was to clamp the open ends again just to make sure they held snug against the plugs while curing:

With that done, I moved on to permanently mounting the (finally) finished vertical stab and rudder tips. These needed to be clecoed in, the mount holes drilled up to #30, then everything dimpled or countersunk as appropriate. Once that was done, the tips went back on one last time, and I went to town with the blind rivets. In spite of a weird hangup partway through – the pop rivet tool I was using spontaneously disassembled itself – I still got it done. Good thing I have two pop rivet tools, I guess.

Anyway, it’s been a long road but now I have the vertical closed out. Well mostly..there’s still the rudder bottom cap to finish out and put in place. But that needs far less work than the tips, so hopefully it’ll go a lot quicker…