Chapter 7, Smooth as a baby's bottom...

Shape the foam, build the NACA scoop, glass the exterior.

Start out by gluing four pieces of ultra soft urethane foam to the aft portion of the tub, cut to profile as a form for the NACA scoop. There's no picture, it's nothing new. Others have said it before, I will too. If you look at the urethane long enough it'll sand itself, it's really soft. It cuts easy, so grab your large kitchen knife (mentioned in the plans) after the micro cures and whittle it down to approximate size. Keep in mind it's soft, real soft. I made a spline sander from everyone's favorite, MDF. Ripped to 2.75" on the table saw and a strong-back dado'd in. It'll use third sheets of sandpaper, the plans suggest a 2x4 and use half sheets. Vacuumed the dust of frequently (there will be lots) as micro flakes from the joints will score the foam, it's real soft. You can see four pieces of the chapter 5 masonite I ripped to 1/4" wide and tacked to the LG bulkheads as spacers for the joggle.

Made the plywood fillers at the LG sides per plans, you can see an under brace I used to keep the two "D" pieces in line while the flox cured in the picture. They do sit at an angle from horizontal. The small "A", "B", and "C" pieces cured without clamps... I live on the edge. You'll be adding foam on the outside pieces, and a two ply BID layup on the "D" piece, so watch your flox squeeze out. The workflow for adding the foam in the NACA scoop area, aft of the LG, seemed out of sequence, but it worked out. Watch the angles and overlaps, and cut the foam as close as you can before glueup.

Using a variety of tools, whack the foam on the sides off. A hacksaw frame with the blade turned 90° in the frame worked for me. I also used a draw knife sharpened razor sharp. Go slow, don't try to hit the "1/4" of longeron showing" in one pass. I progressed to the spline sander above, then made my own "Tim Lumpp" contour tool to get everything nice and even. Use a ton of caution when near the NACA scoop urethane foam, it's real soft.

I postulated over the shaping at the aft end, the instructions leave room for interpretation. Do mark a 24" start mark on the longeron, and spline sand a gentle curve from there to the firewall. Don't forget to remove all the foam on LWY and the upper longeron too. I also made a small tool to sand the 3/4" x 1/8" Joggle for the LG cover. It's just a couple of short boards with a piece of 80 grit 'stik-it' sandpaper in the recess, cut flush. You may have to trim the bulkheads to fit the angle of the scoop (I did), instructions say this is OK.

Last pix shows the aft foam. Note the black tick mark on the longeron at 24", visualize the lack of foam at the upper longeron and LWY, and the small divot. I told you to go slow ;-) I should be able to sand most of it out, I'm not quite at final contour yet.... the boyz on the forum wanted a progress report...

Purist, I'm doing "the joggles". Take some scrap foam (I used 3/8" H-45) and layout a male plug of the NACA scoop, cut it 1/4" small on the sides and 1" or so short at the aft end. Make up some wood cauls for the joggles like the picture. The dark brown stuff is Masonite left over from chapter 5, it's 1/8" thick, the same as the joggle step. How about that! A piece of junk MDF ripped at 6° on the top to hold the flag end of the glass in. Glue the pieces up to fit the joggle unglassed.

Do a dry run. Wet out the glass between two sheets of poly on the workbench, apply to the sluried scoop, work it into the corners. Now put the peel ply on, cover with a sheet of vacuum bag breather (non woven polyester batting about 1/8" thick uncompressed) cut to the shape of the scoop plus enough to wrap up the sides. Put the foam plug down, shove it forward to get the glass tight to the sides, add some weights to conform to the fuselage foam. At the aft end, use all three hands to add the cauls mentioned above. Use more junk pieces of foam cut in strips as 'springs' between the firewall and the cauls. Take a picture (I didn't), have a beer and relax in front of the tube while it cures.

Oogered out the recess around the landing brake with the Binford router and a 3/4" router bit... freehand, built up the edge with quack tape. I should put something along the landing brake to belly foam joint to keep the epoxy out when I do the bottom layup, but I'm not sure what... if anything. Oh, I used match head sized drops of 5-minute to hold the LB in place every 4-5 inches around the perimeter, and two in the middle. Seemed to work well when I made the sides, should here too. Blue masking tape is about where the fuse will get cut for the front LG wheel.

A buddy stopped by to take a look at my progress (first inspection?) mentioned "Belize" and "fly" in the same sentence. I said I'm a couple of years out and a 40 hour test period, then maybe.

Postulated over antenna placement for the better part of the afternoon. Decided on one NAV and the marker on the fuse bottom, a glide slope and a second NAV in the canard. My logic was to keep the coax runs short (less loss), and a bit of weight savings (coax isn't exactly light weight). Note the MB is curved like a piece of wet spaghetti, apparently this is all that's needed (wet spaghetti), and the NAV is pointed to the north. The NAV in the canard will be pointed east, big whoop. Note also where the coax enters the interior (lower longeron), and how close the MB foil is to the non existent wood step reinforcement. The spacer foam is pretty thin near the lower longerons, I buffed the inner glass routing the coax channel on the MB side, it's approx 1/4" deep. Note I'll be doing something else in place of the plans step.

Bottom layup. Plans say "about three hours", plan on four or five with help, six or more if working solo. Wear your trash shoes; and make sure you have plenty of nitrile gloves, brushes and paper towels. Not much to say, radius all the joggle corners (F22, speed brake, ...) and have at it. Don't squeegee real hard on the NACA scoop foam, it's real soft (see above), and slurry the side a bit further down than you'll be laying the glass. Trim the bottom glass real nice near the "A" wood pieces at the LG cover, as the three ply UNI reinforcement may get in the way. I also slit the glass at the speed brake, as there was no way I could get the glass to lay in the depression. The X-acto came in handy. There's a couple of bubbles in the picture (I can see them), and small ripples in the glass (I can see them too). Notice the rudder bracket screws are covered with heat shrink. Do cover them with something. Don't forget the flox corners at the NACA scoop, forward and aft.

Flipped the fuse, cut the rectangles out for the canard, used my draw knife to remove the bulk of the foam at the top longeron curve. My little block plane came in handy to trim the longeron near F-28. The spline sander I made for the NACA scoop foam was handy to sand the canard cutout flat, level, plumb, and parallel. I did the glass layup the next day (what a job), and was reasonably pleased. I did rip the two ply BID reinforcement at the firewall / aft LG bulkhead off before cure, I just didn't like it.

A local builder came up today, helped me do the second (last!) side layup, it really helped. In the picture you can see two white [micro] buttons in the lower longeron. These are what remains after recessing the seat belt attach bolts. I put them in (and the plywood square, and seven ply BID reinforcement) before glassing up the outside of the fuse.

First flight. Safety helmet on, Mary Poppins in the aft seat with the safety umbrella. Winds calm, visibility 30' (to the garage door), density altitude eight thousand niner hundred. Zoom zoom, putt-putt. .875" AGL was the best I could do, I needed to use the pillow for under my butt.

Stick a fork in it :-)