Matt's RV-7 Project

After one last round of sanding, I'm finally happy with the shape of the doghouse:

Remember how I cast a recess out of flox for the plastic slider seal block to perfectly fit inside the doghouse? Yeah, that wasn't such a good idea. Well, it actually was a good idea, just poorly executed. I should never have tried to cast something like that without all the parts in their final positions – when I put it all on the plane, nothing fit together. So, I had to laboriously grind out most of the flox with my Dremel tool.

I put tape down to protect the fuselage, slide track, and seal block, then stuffed a new batch of flox into the open end of the doghouse and set it down over the plastic block. It's only inserted halfway because I haven't trimmed the front end per the plans yet. As long as the exterior surface is cast correctly I can dremel away any excess flox buildup inside the cavity.

While the flox is curing, the skirt is clecoed to the canopy, and the doghouse is weighted down with a bucking bar that I taped in place. This time around, everything should be in its final position while the goop dries.

But just look at the profile of that canopy skirt, eh? Eh?

More sanding, and the slider seal doghouse shape is starting to appear. I like the way Superfil sands – it's a little easier to contour than straight micro.

Another layer of filler to help build up the shape:

I smeared Superfil all along the bottom aft edge of the skirt, so I can sand it down to a nice flat surface for better sealing against the fuselage skin.

While the above was curing, I played with the side skirts a bit, using my shrinker to try to get them to fit the fuselage better at the aft ends. The fit is marginally better now, although since I only have a minimal grasp of what I'm doing with the shrinker I probably wouldn't try this approach again. Still, it seems to fit okay and it looks fine after I buffed out the marks left by the shrinker jaws. There is still a gap of 1/16"-3/32" but I am going to leave it alone and seal it against air leaks using a different method (stay tuned for a future installment).

After 10 hours or so, the filler from this morning was cured enough to sand.

I applied a little more filler in order to fine tune the shape of the doghouse area a little more.

Here's a little detail that may or may not help seal the canopy against leaks, but I think it will at least end up looking cool. I covered the C-679 slide track seal with packing tape, then pressed it down into a bed of flox inside the doghouse:

After letting it cure for an hour, I popped the seal out of there, leaving a perfect impression behind in the flox. Once this is fully cured, I will sand and fill as necessary to give a nice surface. The goal here is to make the C-679 seal perfectly and leave no path for cold air to leak past.

I spent the morning sanding Thursday's application of filler, then sprayed it with another guide coat of primer and sanded that off too. The result was pretty good – the light grey areas shown in this photo are actually historic low spots that are now filled and sanded level. The dark grey spots are the only remaining low areas still needing filler. Most of these are in the area of the slider seal "doghouse" which I have yet to do much with.

Since I am running low on micro, I mixed up a batch of Superfil from a quart kit that I'd bought a while back. I've never used this stuff, but people seem to rave about it. Each of the two components is the consistency of peanut butter, and you mix them 2:1 by weight or volume. I eyeballed three plastic spoonfulls of blue goo to one and a half of tan goo.

Since I had a little extra mixed up, I started applying filler to some of the more egregious areas on the underside of the canopy skirt. I don't intend to go for a perfect finish on the bottom, since it will be hard to see from inside, but I do want to at least fill in the voids.

I finished sanding off all the high spots on the canopy skirt:

Then I smeared on more micro filler, thus making more high spots to be sanded off later.

Hopefully the remaining low spots will become smaller after each fill/sand cycle. Eventually this should converge on a nice-looking surface, but there's a lot of work between now and then…

I sanded on the canopy skirt for about an hour tonight, making a big dusty mess of my garage:

After I did all the sanding I thought I could possibly do, I shot a coat of grey primer on the skirt.

Once the primer was dry (which was pretty quick since micro filler is so porous) I sanded the entire thing some more. The spots that remained grey are the low spots that I'll need to put more filler on. I'll have to do that later since I'm too tired to mess around with gooey stuff tonight.

By the way, I've become a convert to Norton 3X sandpaper. It's significantly more expensive than the no-name stuff, but cuts better and is way more durable. To me, anything that makes fiberglass sanding go quicker is worth it.