More Wood!

Ok, so I got the necessary braces installed. I also set up the seat well enough to take some measurements with a laser level simulating the horizon from my height when seated, and used that to generate templates for the canopy. However, in the meantime, there were a few more pieces of woodworking to attend to. The first is that, because of the way the fuselage is built, the plywood that stretches over the crossmembers behind the seat doesn't have a good way to glue to the longhorns.

The solution the previous builder used was to glue on more spruce to build the sides up to level, and it makes sense to me. So I went ahead and did the same. First I shaped some pieces of wood to follow the contours of the plane:

Then I glued them on, came back a day later, and started planing. I had to build up the center crossmember as well, because of the compound "dip" in the fuselage (Only needed about .02" or so, but it was easier to glue on a much thicker piece and plane it down later.) I used a hand plane held at an angle, so that the center x-member was being cut while the plane used the forward and rear x-members to set the height. Once the x-members were all co-planar, I planed the sides to match.

I didn't get a picture of the finished product, apparently. I was about ready to glue the plywood on, when I realized I'd want all of the gussets in place first; they'd be hard to add later! So I spent some time sanding tiny wood blocks to the right compound angles. It's not very difficult, but it was a little time consuming. I ended up needing 12; I was able to finish and glue 9 before I ran out of time.

The next time I was down, I finished making the gussets I needed and glued them overnight.

After everything had time to set, I planed and sanded everything down and cut the plywood to fit. This is pretty thin stuff, and I've found that by using a utility knife to cut through it, I can usually avoid sanding it except to break the sharp edges.

After several passes with the knife, it usually only needs a touch with sandpaper to get the edges smooth, and as long as you marked it right, it's bound to fit. All that was left was to glue it all together and clamp it down.

Next time I'm down, I'll pull the clamps off and start re-working the fiberglass seat backs. They need to be trimmed a little bit in order to fit the new angle. I'll probably cut the holes for the control sticks too, which will allow me to install those again and start fiddling with their location. I'm gearing up for all of the non-fiberglass things, since winter is almost upon us here. I've been working on designing a prop in CAD, as well as a control stick grip. Unfortunately, it looks like the canopy/aft deck/front deck is going to have to wait another winter... at least I have a plan for that now.

Seats (Part 4)

Continued from Seats (Part 3)
I got a call a couple of days ago that my canopy was being molded, so I expect it to be here in the next couple weeks. That reminded me that I hadn't finished my seats yet, which I'll need to help me decide how tall to make the plane. So I started working on the seat back. It's built the same way the seat pan was, and the same way as the wing walks are. But I do have a few pictures of the process.
Here's the second layup:

I build the foam and wood board larger than I'd need, so once the fiberglass was all cured I cut the seat to size. I'll be cutting it in half once the hinges are attached so each side can flip down independent of the other. I'm running out of space in the garage with the wings being worked on, so I had to stick it in place for now.

Continued in Seats (Part 5)

Outer Wings (Part 6)

Continued from Outer Wings (Part 5)
Today I finished sanding the wing to shape. My micro trailing edge is nice and solid, and I sanded the overlapping fiberglass on the leading edge down nice and smooth for the next couple of layers. I hand planed the spars down to slightly below the airfoil contour, which was much easier after I took five minutes and sharpened the blade. I didn't take many pictures, but I did document how I'm prepping the sump drain as well as the WAF cut-outs in the foam. The cut-outs each get some one-on-one time with a Dremel, so that the foam is slightly recessed. Next I take a piece of pre-layed-up fiberglass and cut it to fit the cut-out.

Once I've got all four cut to fit, I mix up some micro and apply it to the foam, then set the fiberglass in the cut-outs. I'm not too picky about how it lays, but generally I try to make it as close to the airfoil contour as possible, erring below rather than above.

For the sump drain, I start by attaching a circular piece of duct tape over the hole. Then I use a really thick micro to build up from the aluminum block to the airfoil contour. While the micro is in the "green" stage, I use a Forstner bit to generate a nice circular hole down to the aluminum block where the duct tape is, which gets removed (because it's now all gummy and may not keep the resin out during the big layup.)

I'll replace the duct tape before I do my layup. I'm prepping for that by cutting templates out of plastic 2 mil drop cloth, then cutting the fiberglass from that. If everything goes well, by this time tomorrow the wing will be finished and off the plane.

Wing Walks!?

I've ordered and received a whole bunch of foam from Dynamic Systems (aka SunMate), which I chose as a crash safety measure as much as I did as a comfort aid. I've been cutting away and shaping, but I've gotten to a point where I need to be doing a lot of sitting in the seat and seeing if it's comfortable yet. Only problem is, the plane has no wing walks.... and as challenging as it was to get in the plane standing just on the rear spar, that was preferable to setting up a makeshift seating setup outside the plane. I decided, since I need wing walks eventually, I might as well get them knocked out now so I can get this seating stuff taken care of.

The previous builder had glued and shaped the foam for the top of the inboard wing, and laid what appeared to be one layer of FG on it. I didn't want to disrupt the shape of the wing, and I didn't want to completely start over, so I decided to try and add a wing walk structure without disrupting anything I didn't have to. First step was to flip the plane over and get a good look at the underside.

The previous builder had used a single sheet of 1" foam, and cut slits halfway through it about every 2 inches in order to allow an easy curve to the shape of the wing. This was about how far apart I wanted to put supports, so I started by using a razor blade to extend the slits all the way to the fiberglass skin. I made my wing walk 12" wide, and it runs from the front spar to the rear spar. I dug out the foam in the slots, then cut another slot for a support to run lengthwise from spar to spar. I used ⅜" a/c plywood for the long support, and 3/32" a/c plywood for the rest of the supports. All the supports are 1" wide.

The last step before epoxy(or so I thought...) was to cut slots in the foam for two ½" spruce blocks to (drastically) increase the gluing area for the ⅜" main support.

When I test fitted the supports, I noticed that my long stringer (which was cut very, very precisely to the airfoil contour) didn't touch the skin in a lot of places. As in, ¼" to ⅜" gap. A closer inspection of the wing showed the problem; the foam and fiberglass had sunk, or had been attached too low at the rear spar, and the wing shape was not preserved except at the two wooden templates. I had to think for a couple days to come up with a solution to that one, but I think I came up with a good one. 

I used my hot wire foam cutter and two wooden templates to cut two 12" wide foam templates, one for each side of the wing skin. The outside template I left long enough to rest on the spars, while the inside template I cut about 1" too short so it'd be able to easily drop in place once epoxy was curing. I used some highly sophisticated and carefully calibrated bracing structures (read: spare tires) to support the outside template and, once it was in place, I mixed up my epoxy with some micro to fill in gaps and started inserting all of the supports. Once the supports were all in place, I placed the inside template (with plastic trash bag to isolate it from the epoxy) on the wing, and added a good amount of weight.

When I came back the next day, I was *very* happy to find that the setup had worked perfectly. My wing was now the shape it should've been (or, much closer to it) and the supports were all in place and holding. I mixed up more micro/epoxy and filled more gaps, then laid up two layers of FG and placed them over the structure. Although I'm not sure it was entirely necessary, I repeated the process of weighting the template over this to make sure it all cured with the right shape.

I did the other side the same way, and although the previous builder cut a few more slots in the other side, the results were similar:

The final result was solid. I'll be adding one or two more layers of FG to the top of the inboard wing, but it's already strong enough for me to stand on unsupported with no perceptible give. I'd call this a success.

Seats (Part 1)

After two solid months of doing little nothing projects here and there and generally not accomplishing very much, the weather finally got nice enough to start doing some fiberglassing. So I decided to build my seats next, because 1. it's a smaller fiberglass project to get me back in the swing of it before I tackle the wings, and 2. once I have the seats in place I can set my rudder pedals, my control sticks height, canopy and therefore aft deck height, and also sit on it and make airplane noises. I'm using carbon fiber for its strength to weight ratio, and because the seat giving way in flight would cause the airplane to be uncontrollable, so I want it as strong as possible. At this point I intend to build as much of the plane with vinylester resin as possible, because it cures very fast compared to just about every viable epoxy I've tried. However, there's some solid research that suggests vinylester doesn't bond well with carbon fiber, so I'm using West Systems epoxy instead. West Systems is fantastic stuff, but it takes about 6 hours to cure at 70* F, and that time goes up dramatically as temperature goes down. This week is all warm days, so I'm gonna try to knock this out before the end of the week.

I started with ½" foam, sliced into 2" strips. I epoxied 3/32" plywood in between each strip, so the strips of wood and foam are oriented length-wise in relation to the aircraft.

Once that had cured, I cut the panel into two pieces, one to match the seat back, and one to make up the flat bottom of the seat. I also built about the crummiest looking jig you could imagine to get the angle of the two pieces right, but it worked out just fine for my purposes.

I didn't get a good picture of it, but I cut slots right next to each of the wooden stringers in both panels, then used that same 3/32 plywood to make biscuits to fit in them to really strengthen the joint. Once I had them all prepped and trial-fitted, I mixed up my epoxy and went to work. Obviously no pictures of the process, but it was messy and the epoxy gets hot in the cup pretty quick when it's 80 degree weather. No misadventures, however, and with a carefully calibrated weight on top, and carefully calibrated heat lamps in place, the curing process could begin. Tomorrow I hope to begin laying my carbon fiber and start making this look more like a fancy seat for a composite aircraft (and less like I have no idea what I'm doing.)
Continued in Seats (Part 2)