Chapter 7 - Fuselage Exterior
I held the heat duct parts vertical during cure using a cured bid tape spring. This is a device you can make for free when you prepare too many BID strips for the taping in Chap 6.
Much, much later in the process I wish I'd known to make a slight modification here. The triangular birch inserts which hold the fuel valve are also used to support the hard point for
the landing brake mechanism. When I came to add my electric landing brake actuator [$89 and it replaces lots of prefab hardware for the mechanical system] I realized that the
hard point is about 5 inches too low down. If I'd know then what I know now I would have extended the birch
supports about 1 1/2 inches further aft (which would also make them reach up to the map pocket). This way I could have
made a new hard point for the LB actuator, once I knew where it should be, by just drilling and inserting some al tubing.
I got around the problem (see my Chapter 9), but it would have been better to have extended the birch triangles in the first place.
I put a piece of cardboard under the plan and made needle holes all along the lines. Join the dots and cut with scissors. I made opposite patterns but you dont really need them. I used the first one and just flipped one pattern over the centerline on the fuselage. I used a hacksaw blade to cut the foam squares, then Bill's band saw to cut the curves. (Promised him a ride for the use of it). I cut a little wide of the line and sanded to shape.
Cutting and sanding and cutting and sanding ....
[Later note: I wish I'd learned about spline sanding (or Oreste's little sanding trick) before doing the shaping of the fuselage sides. It seems so easy now, but then, I've had a lot of practice.]
I sanded the scoop to size. Messy work and you gotta be REAL careful with that 2 * 4 sanding rig. Just nudge it the wrong way and it lifts chucks of foam from the wrong place. While sanding one side I accidentally bumped the other (completed) side with the sanding board. Took a out a nice lump I didnt want to take out. Repaired with more foam & micro and moved on more carefully. Next tapering the sides and curving the bottom. Hard work. Didn't feel like it was going well till the very end when everything seemed to curve nicely. I tried a variety of tools. Sabre saw, belt sander, hacksaw blade, 22 inch 2 * 4 sanding thing per plans, surfoam, hand held 36 grit. Another of my favorite tools is a belt sander belt fitted over a piece of plywood just the right size to hold it tightly. Used the sabre saw and the 2 * 4 most. Then came the belt sander. Next time I do this it will be easy!
Glassing the Scoop
I read Marc's chapter 7 and decided to try a few tricks of my own to get the joggle glassed. I mixed some flox, micro and pure epoxy. Micro'd the foam, then floxed in the corners. Brushed the flox with a brush slightly wet with pure epoxy to get a smooth surface and reduce the curve of the corners. Layed the BID and used saran wrap per plans (just on the edges. Peel ply on the rest. No air that I can see, and everything joggled and wrapped as needed. We'll see better when it cures. I did the rear portion seperately. Didnt bother with the flox and had all kinds of problems trying to get the air out. Move the cloth one way and air pops up somewhere else. Eventually I lifted the wet cloth, did my flox thing and layed it back down. Air problems went away.
Antenna and Radio Stuff
Ordered NAV antenna from RST. Took a while to find them. They're number is 530-272-2203 and they also have a web site. Apparantly the "antenna" comes as a roll of copper tape, some fittings and instructions. I'm considering putting a marker beacon antenna in the belly per archives. Why do plans recommend the Nav antenna there? I'll take a guess. Nat is mainly a VFR man. His MB antenna is in the wings and he says it works just fine. I think I'll follow the RST recommendations on this. I hope this change doesn't bite me. I've been looking at intercom systems since I'll need to do some wiring in the headrests soon. When I found the RST web site I saw they're Audio Panel / Intercom system. The specs sound great and its cheaper than the sigtronics I was considering. Unfortunately its not stereo, but then I wasn't planning on relaxing to stereo music while flying. I'll live with mono music which cuts out automatically when one of the other channels has audio. Maybe I'll fit stereo speakers for use on the ground. The RST unit lists lots of features I like.... until I got to the last feature - build time 15 - 20 hours! Aghhhh! Ah well. I guess I might as well build it. I'm building everything else.
While waiting for the antenna parts I decided to move ahead with other stuff. I made the A frames. Sort of like an airplane rotisseri. Didnt want to drill holes in anything, so a rigged a wood clamp at the front and used the blind screws at the back.This is fun. Now I can fly the airplane. I contoured the sides, sawed off the tabs from F22, prepared the sight gauges and did some general clean up work. The sight gauges (per Vance) were a little bigger than the flat area I'd prepared. No excuse - I had the gauges when I did the sides. I had to trim the white gauge backs a little and radius the corners a little to get them to fit flush. Didnt flox them in yet. I'll do that later when the strakes are built.
Adding the step reinforcement was interesting. I seem to be chopping holes in this plane everywhere lately. I used a belt sander to contour both inside and outside. I'm a bit concerned about the shape of my (plane) bottom. It has a bit of a bump in it where the softer foam sanded away before the hard longeron. Asked the maillist for advice and got seven messages in a matter of hours. Best advice seems to be to get some instafoam, brush a little on, then recontour. The alternative seems to be "Don't worry. No one will notice". Ah, but I will. Every time I look at the plane I'll see that poor shaping and wish I fixed it.
My Pour Foam Experience
Well, my pour foam arrived. Looks just like the "great stuff" in hardware stores but
it comes in two bottles. Its interesting stuff. I tried "brushing a little on".
After 30 seconds my 1 inch brush became a 4 inch lump of foam. Hmmm.
Next I tried pouring it on using foam guides to keep it where I wanted it.
Worked better. You can't mess with the stuff once it starts to foam or it
turns to goo and stops expanding. Just pour it and let it alone.
I tried brushing a little of the A bottle, then brushing some of the
B bottle on top. Worked ok so long as I completely matched the brushings
and "stirred it up a little" in place. This way I got 1/8 inch of depth.
Pouring gave me about 1/2 depth. Later I found that stuff I brushed on
in two stages stayed rubbery and rolled off when sanded. Hmmm. I tried holding
the stuff down as it expanded using saran wrap. Helped a little. After an hour
of two of experimenting I had a very ugly shape. Another couple of hours
of sanding (uggh) and I was back to the required shape in the areas
where I'd got enough foam down. I'd already micro'd one side of the bottom
curve, so I carried the sanding onto that area. Wow! This is much easier.
The micro may be harder to sand, but there MUCH less of it and its much
closer to shape. Micro works a lot like the filler I used when helping at
my brother's auto shop many years ago. I must have learned some of my
brother's "eye" for shape and his quest for perfection. Thanks, Mike,
I think! Later, during finishing, high standards will be appropriate.
Right now I'm wasting my time, adding weight and messing with areas which
will be under the strake anyway. But - I'm learning in a place where it
wont hurt. So much for my pour foam experiment. Micro works better if
you're dealing with a shape issue of 1/8 inch or less. I'll put the foam away till the plans call for it. End result - I'm now happy with my fuselage shape, and a learned a little about how pour foam and micro work.
I finally got my antenna kit from RST complete with copious educational material about antenna theory. Apparantly RST's Jim Weir was the guy who did the antenna for Rutan's voyager. Interesting. I plan to put an MB antenna in the belly. The length of each dipole is listed as 34.3 on the drawing and the length from tip to tip is shown as 78 inches. Hmmm. 2 times 34.3 is 68.6. Which is right? There follows a multimessage discussion in the mailist. Marc kindly calculates the lenghts for me - from a formula which is different from that in the instructions. Confusion. Some joker politely tells me I could use a coat hanger and stop worring about inconsequential details. Yes - but I'd still like to know which is right. I'd bet there are lots of Cozy's flying around with 78 inch MB antenna which should be 68 (or vice versa). I'm sure they all work fine, but I'd prefer to know which is right and why there are two formula, just for the sake of consistancy. I sent email to RST for clarification. Still waiting for a reply. In the meantime I built the antenna 78 inches, dug the channel, soldered the joints, added the baluns and 5 min epoxied the rig in place. I was gently pushing the connections down into the channel when one of the antenna leads just broke near, but not in, the solder. I must have nicked the wire when I trimmed the coax. Stripped it back some more and soldered again. Everything seemed solid so I put it back in the channel and filled the channel with micro. Had a lot of trouble getting the connections to stay down in the channel. In the end I used small pieces of foam to hold them in place till the micro started to set up, then removed the foam and added more micro. I now have 1 (one) cable behind my instrument panel. Checked my email again. Marc Zeitlin quoted an article by Jim Weir which agreed with the shorter length. Nat replied that I should call Jim Weir. Problem is that I don't want to wait till Monday on this minor issue. The consensus on the length seems to be 34.3, so I cut 5 inches off each end before glassing. I'm sure it'll work either way, but I'd still like to know which was right.
footnote: message from Jim Weir: "34.3, Jim". Not a man to waste words is he?
Glassing the bottom
The plans say this will take 3 hours. I wonder why it took me almost 8. It's not that I took breaks or was working slowly. I was rushing around like crazy. Just finished the first ply of UNI when a thunderstorm rolled in. I thought I was in trouble. In 20 minutes the sun was back. Temp never dropped below 80f. Did the reinforcing layups on wax paper first. Ended up with a hair dryer squeegeing excess epoxy out of the layup. Had some trouble keeping the edges straight along the sides. Washed my hands half way through (you can figure out why) and totally forgot to put the protective gell back on. After a couple of hours of hand smoothing cloth & stippling my hands were covered in epoxy. No sign of allergy yet, but lets not tempt fate. I'll remember the gel next time.
How to get epoxy off your hands
I've tried various approaches to this on the occasions I've got epoxy on my hands without the gel. I was always left with sticky hands (and arms) no matter how much I washed and scrubbed with acetone, soap etc. This time I used acetone first, rubbed it round quickly, then immediately added washing up liquid. Mixed these together on my hands for a couple of minutes, then washed off. Bingo. No sticky residue - but much better to use that no 9 gel stuff ahead of time.
WARNING - Don't try this at home
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I received a comment from Marc Zeitlin about the above paragraph. Marc says he used No 9 gel and still developed an allergy. Now he recommends Butyl rubber gloves with vinyl throw-aways over them and cotton liners inside. I'm concerned about Marc's comments and plan to do some research on epoxy allergy statistics, symptoms etc. Marc also comments that a solvent like Acetone is the very worst thing to use to get epoxy off your hands because it is giving the epoxy a highway right through your skin. Given Marcs comments I don't think I'll use this technique any more.
I now use the thin latex gloves and I've learned to like them. Its wonderful to rip them off and have your hands totally clean. On long layups I sometimes do this a couple of times. You can use your gloved hands to stretch the fibers and manipulate the layup.
Glassing the sides
It took me a total of 7 1/2 hours to glass the sides. On the first side I didn't think to cover the blind screws in the firewall. Spent 20 minutes scraping epoxy off the threads. For the second side I wrapped them in box sealing tape first. A lot of stippling and "laying on of the cloth" but finally I have a fuselage.