Mar 15, 2024     Center section drain fairings-- Revisited       Category: Fuselage

So this has been another "educational" moment for me. As a review, the first four pictures below outline the fabrication process for the fiberglass fairings to fit the fuel drains under the center section, done in Feb and Mar 2022.
A few days ago while searching the loft for something else I had squirreled away, I blundered across these fairings I had stuffed up there last year. Nope. It was two years ago! Anyway, they're all warped now!? WTF? They are proper fiberglass/epoxy layups and not supposed to act this way, as far as I know.

Pretty sure the culprit is the high-build primer I had sprayed on them to fill the fabric finish on the outside of the layups. It was a two-part, catalyzed PPG primer, so I figured it was going to be pretty stable. Guess I should have read the fine print, or the FULL instructions.
Everything was fine spraying and wet-sanding them out, but over time, the primer layer must have shrunk some as some polyester layups will. The fiberglass was thin enough and the primer thick enough, that the one overpowered the other.

Anyway, what to do about it? A simple fix would be to blob a bed of flox around the inside of the flanges, then press them onto a flat release surface... and wait.
Following their release, wait again for nice enough weather (non-life threatening) to take them outside and grind off all the unwanted bumps and lumps. (very, very dusty).
Losing my enthusiasms for making chemistry play nice with others, I instead made a shout-out to my son to see if he may be interested in a 3-D printing project.
I sent him some basic dimensions, and he launched back the two "Fairing" images below in about an hour. Pretty much exactly what I'm looking for. Since it apparently wasn't much of a challenge for him, I suggested he work up a teardrop shaped set... No, these are fine. Really. He said something about PLA, carbon fiber mix should paint well.... k?
I told him I wasn't in any hurry and could pick them up the next time we meet up. He's in the UK, so I should update this when we get back from his house in Sept.

The beautiful red Hatz pictures below show these in situ under the center section fuel tank. Pictures are of John Hanson's Hatz Classic.

  Mar 14, 2023     Bending the acrylic - (6.5 hours)       Category: Fuselage

Built the acrylic bender (see 11/11/22 Tools entry). I had been practicing bending .090" plexi scraps I had laying around and seemed to achieve some basic understanding of the process. Notably, how best not to screw things up. Didn't have any 1/8" (0.125") scraps until I cut out the windscreen blanks.
Once I tried bending this slightly thicker stuff, my wee little transformer and hot wire just were not quite up to the task. This thicker stuff is covered on both sides with a coated, craft-paper like sheeting to prevent scratches (good) and the IR temperature sensor works better with the paper surface (also good) but it also requires just a bit more heat to get it up to temp and it's hard to see if/what is going on underneath approximates where we're trying to go with this (bad).
As the transformer fell a bit short and I don't have a Variac-type device to run more amps through the wire, a heating rod would have likely been the next best choice. Sadly, my interweb search skills failed to turn up any suitable options, although I'm sure they're out there somewhere.
I observed quite a number of YouTube-sters using heat guns to bend acrylic.... I have a heat gun! Testing on sheet metal first, I found the low setting would only get it to about 300F. On some plastic scraps, it would gradually get there if you concentrated it and maybe a bit more. I believe I read the bending temp is about 320F. Anyway, that works.
Once the blank was in the jig, I placed a couple 1/4" plywood (heat-masking) strips either side of the strip I wanted to bend. In only a few minutes the bending was done.
The bends and angles were very close in the initial bends, but not quite a perfect fit in the frames. I subsequently squeezed them into the frames and used the heat again to finish forming them into the frames.
Final steps included final edge trimming and polishing and the installation of nutplates in the fuselage topskins as the windscreens will be screwed in place.

  Mar 08, 2023     Windscreen Acrylic       Category: Fuselage

Used the tagboard templates trimmed to fit the frames to layout an initial cut pattern on my Home Depot acrylic sheet.
Cut the 1/8" thick acrylic from a 24 X 60" sheet. After I laid out the patterns using the templates, made the cuts on a sheet of polystyrene foam insulation. Makes a nice flat backstop for cutting. Clamping was done using 9-lb sandbags.
I used a cutoff wheel chucked in an electric drill to saw the plastic. Usually chuck that cutoff wheel in my angle die grinder, but the die grinder spins too fast and tends to melt the plastic edge (bad). So, in the drill, it spins slower, no melting, more torque and still cuts well through the acrylic.
The edges will require filing, sanding and polishing before final install. Also they will need a relief notch at each rear corner to clear the welds there.

  Mar 05, 2023     Windscreens cont'd...       Category: Fuselage

Welded the inside corners of the top flange to the side flanges. This stiffened the frames up nicely, making them more stable for the fitup on the fuselage.
Fitted tagboard templates into into the frames in order to establish reliably-shaped templates to cut out the acrylic.
Finally, centered and aligned the frames on the fuse, drilled and clecoed same in place.
Next, I plan to install the windscreens using #8 machine screws which will require nutplates riveted to the fuselage skin. There is potential to screw up this step too. Getting the nutplates installed concentrically with the holes in the frame flanges means the flanges will lie nice and flat on the skin, if not... well, lets take the time to get them concentric.
Also, fitting the acrylic may go a little quicker if I can use clecoes instead of nuts and screws. May fit that before launching down the nutplate trail.

  Feb 25, 2023     More windscreen frame fabrication       Category: Fuselage

I decided to just go ahead and cut out the windscreen openings as they are (bowed) and see how it goes. It might get better on it's own? Either way, this step has to get done, just get on with it. Drilled holes in the corners with a unibit to connect the straight cuts to start. Initially planned to cut the straight parts using the angle die grinder with a cutoff wheel. But since I didn't want to blow grinding dust from that all over the hangar and everything else in it, the other option was to take it outside... Not an option. Not this February, even equipped with long underwear.
Chose instead to use the vibrating, oscillating tool with a cutoff saw. Saw this technique on a "Hints for Homebuilders" EAA video. Seemed like a viable option. And, Waay less dust. Marked the cut lines with masking tape and followed same. Worked okay.
Of note: I used a fresh steel blade (noted for "wood & plaster") to cut this soft aluminum (probably okay). The carbide-toothed variety of the same blade was 3-1/2 times the price and I was only going to use it this once... That might have been a better choice but I was too cheap to go for it. I think the steel blade began to dull right away as it required increased pressure to continue cutting as I went.
Also of note: It may be due to the increased hand pressure this required as I mentioned above, but in the hour or so all this cutting required my hands developed and continued to "buzz" for the next three days. I hadn't noticed this before, but usually this tool is used for a couple minutes and then you're done. I'll approach a big job with this tool differently next time.
Once cut out, I filed and sanded the edges smooth and readied for the next steps.

  Feb 11, 2023     Bending Windscreen Frames       Category: Fuselage

The windscreen frames are each bent from a single sheet of 0.032" 3003-H14 aluminum. Once bent, openings are cut into each face of the 3-pane framework. Following that, a single piece bent acrylic sheet will nest inside the bent framework, then screwed to the fuselage topskin.
The first two straight bends forming the edges between the center and side panes were done on the bending brake using a formed radius block (3/8" radius round-over routed edge) clamped in place instead of the stock brake shoe. This formed a nicer, radiused edge instead of a just a simple bent edge.
Next up, the trailing edges need 180 degree bends to form a "cupped" edge into which the acrylic trailing edges will nest. Bent to 90 using a short length of 3/4" square steel (it has nice, radiused corners). Used a short piece of 1/8" birch plywood clamped into the trailing edge corner to form the last 90 degrees of bend, forming the 1/8" pocket for the acrylic trailing edges.
Forming the bottom, flanged edges I used Scott's 4-roller flanging tool. The tool worked great, allowed the varying bend angles around the curves required on the sides and produced really smooth, curved flanges. Much smoother than I could have done another way. Of note: The side flanges on the aft frame has a little more curve than the forward one. Sooo, when I bent the flanges on that curvier edge, it kind of put a bow in each side pane of the rear windscreen frame.
There's a coupla fixes available for the bow. One way, I could use a stretcher to stretch the flanges which would take out the bow but also beat up the flanges which would need sanding and cleanup. Option B is to simply forge ahead, cut the openings in the side panes and see how the bow looks after removing most of the metal on those sides. If the bow is still problematic at that point, might be able to massage the lower edge (the only part retaining the bow), or worst case, go back to the stretcher and beat up on it. More to follow.

  Oct 07, 2022     Windscreen frames       Category: Fuselage

Plans contain drawings for the one-piece windscreen frames at 1/4"=1" scale. Blew the drawings up at Kinko's by 400% to save some time sketching same.
Transferred to tagboard and cut out to form templates to transfer to the trick aluminum called for in the plans. Plans call for 3003-h14 aluminum I assume because of all the curved flanges and bends required to form from a single piece as this is a very malleable alloy.
The front three edges get a flange bent into their curves to allow the frames to contact flush and attach to the topskins. The rear three edges get straight bends but they are two 90 degree bends each forming a "cup" into which the rear edge of the acrylic nests. The acrylic is also a single piece, bent same as the frames and will nest into the frame. Once the two are assembled together and screwed to the topskins the acrylic is captured in position. Plans call for Lexan, but I think I'm going with acrylic (plexiglass) as it is a bit more scratch and fuel resistant. Plans also differ depending where you look regarding acrylic thickness; 1/8" or 3/16".
Probably going with 1/8" depending what and where I can find it. Hopefully, it will only need to stop an 80 mph booger from the front cockpit.
First attempt to mock up windscreens I used cardboard, but it was difficult to work with making small changes. Plan Bravo used 1/8" foam-core project boards to cut into windscreen panels. This stuff works easier, stays flat and makes those necessary small adjustments more clear. Looks like about 120 to 122 degrees adjusts the panels to the right shape. The foam-core shape is ultimately the finished shape of the acrylic inserts.

  Oct 01, 2022     Cockpit coaming       Category: Fuselage

Installed the metal-cored, PEX tubing around the cockpit openings. Used a fiber cutoff wheel chucked in the air drill to slot a length of tubing. Initially tried the angle die grinder, but it spun too fast and tended to melt the PEX and bog down. Air drill runs slower, doesn't melt the stuff and has more torque.. worked better.
Slipped the tubing over the cockpit edges, then snipped the ends to fit, butting together at the forward edge. Except where they are butted together, the tubing is held very rigidly in place and really needs no hardware or lacing at this point to hold it moreso. Where they are butted, I plan to bond them in place and call it good.
After paint, a layer of foam pipe insulation will be wrapped around the tubing and a stitched leather cover laced in place.

  Sep 30, 2022     Fwd. Topskin       Category: Fuselage

With enough fiddling, evenly concentric holes around the cabane tubes look to be good enough. Similarly, the access holes for the roll wires cleaned up well to be large enough to permit any reasonable vibration and still unobtrusively small enough. Planning to use a leather disk to separate the wires, it will be laced in place during final assembly.

  Sep 23, 2022     Fwd. Topskin (cont.)       Category: Fuselage

Forward topskin fitted and drilled. The cockpit sides were reinforced the same as the aft cockpit ( see 8/15 entry).
Still more fitting to go for the cabane access holes.

  Sep 03, 2022     Forward Topskin Fabrication       Category: Fuselage

Cut the forward topskin blank from the tagboard template. Cabane access holes and roll wire holes were opened to a minimum size reference the template. Rolled the skin over the same PVC tube, centered and strapped into position.
Opening the cabane access holes presents a couple challenges. The cabanes need to be test-fitted multiple times to iteratively open the access holes to an even and adequate size. To prevent any skin drift during this process, the skin had to be first drilled in place and clecoed down.
The cabanes fit over the welded "ears" on the top longerons, which angle the same as the cabane legs. They fit perfectly in place over these ears, when bolted in position. However, until they are in place, they do not. The cabane legs need to be flexed together in order to fit over the tops of the ears and then allowed to un-flex (spread) as the cabanes are lowered down into position over the ears. Accomplishing that while working through a teardrop-shaped hole in the topskin requires another tool.
First picture below shows the cabane and a safety-wired turnbuckle arrangement. Tightening the turnbuckle draws the cabane legs together allowing them to fit over the longeron ears and slide into position.

  Sep 02, 2022     Cockpit Coaming       Category: Fuselage

The cockpit coaming is layered up from the sheet aluminum edge surrounding the cockpit opening. First layer is a unique PEX tubing that contains an internal layer of aluminum between PEX layers. It can be shaped and formed around the opening, slotted and installed in place. Method of attachment TBD.
Foam pipe insulation will layer over the PEX and a layer of leather will be stitched over that.

  Aug 15, 2022     Top Skin side stiffener panels       Category: Fuselage

Once I got the top skin clecoed in place, this .032" skin became surprisingly stiffer around the cockpit opening. But, it's still not stiff enough on it's own. The plans call for an unspecified steel tubing laid out under the opening to support it and welded to the longerons and aft hoop. It would only be now that I could figure where/how to bend and locate that tubing in place around the opening. So I didn't. Different plan is to stiffen these side skins by adding a curved plate to the insides. Intention is to make the sides stiff enough for someone to plant their butt cheeks on without damage. Initially considered a solid plate, something like 80-90 thousands thick but decided I could make/design something as strong but a little lighter.
First made tagboard templates to fit the locations. The inner skin is the same thickness as the topskin (.032") and are spaced off of one another by strips of .050" X 5/8" aluminum. The .050" strips will be sandwiched between the skins and riveted in place as well as around the perimeter of the inner skins. This forms a series of five closed cells or torsion boxes along the interior of the topskin hopefully stiffening them up enough to pass the "cheek test".
Outer skins will be dimpled and strips countersunk to accept flush rivets, producing a smoother finish so the rivets will be less visible from the outside.
Update 8/30/22: Instead of .050" strips along the top and bottom perimeters of the stiffener panel, I joggled those edges. The bottom, straight edge I did on my bending brake. The curved upper edge I used a cheap Chinese auto body tool that produced a joggle one inch at a time. It was good enough to do the limited amount I needed. It was also more controllable than the pneumatic version my neighbor offered up to use.
Once they were completely riveted together I have little doubt they'll pass the "cheek test".

  Jul 30, 2022     Top Skins (The ongoing saga)       Category: Fuselage

After trimming the .032" thick sheets to size for the cockpit top skins, I busied myself transferring all the required cutouts from the templates to the skins with the exception of all the screw mounting holes. Next, I proceeded to cut these openings into the sheets using a collection of saws, snips, files and sandpaper. This seemed like a good idea at the time.
As a "howgozit" measure, I set the aft cockpit skin in place to size up the fitment. The now glaringly obvious stiffness of these thicker sheets may be a problem and will need to be dealt with. I had been using the thinner .025" thick sheets which draped nicely around the bottom and sides of the fuselage and hadn't considered how flexing these stiffer sheets may be affected around the large cockpit cutouts.
Suffice to say, they flex okay around a bulkhead that can be clamped to, but that's about as far as the flex goes. Even then, they don't lay nice on the bulkheads, lifting off the flatter portions of the curves. I will need to roll some curvature into these skins in order to solve that.
Additionally, the areas around the cockpit sides remain flat and will require the same curvature rolled into them. I'm thinking this rolling may have been better accomplished before cutting the large cockpit cutouts. We'll see how this goes... hopefully not another do-over.
Update 8/2/22:
Put some curve into the forward topskin. Not too tough, found the biggest diameter PVC pipe I had laying around the shop and laid it across a pair of sawhorses. Just hand pressure alone rolling the sheet across the tube introduced a gentle curve to the piece. Biggest challenge was keeping the curve consistent with no kinks or flat spots. Gradually worrying this thing into shape.
The portion of skin that goes over the hoop aft of the cockpit opening needs to be split and a filler strip added. Once I finalized where the skin was going to be anchored, I cut a small strip, joggled it's ends to overlap the skin ends and riveted it in place with flush rivets.
The trailing edge didn't lay quite as nice as I wanted over the aft hoop and the scalloped skin I had tucked under the hoop flange. I first shrunk the trailing edge to match the turtledeck slope, then added some sandable filler to blend them together.

  Jul 22, 2022     Top Skins shearing       Category: Fuselage

These top skins are laid out on four-foot wide sheets of aluminum and are nearly as wide as they are long. A clean cut is necessary since most of these edges will be showing perpetually. My 30" shear on the 3-in-one machine can be made to make these long cuts with a little adaptation. It has an open throat of about 1-3/4" so I trimmed the sheets to within about 1-1/2" of the required cut with a cutoff wheel.
Using the shear and starting at one edge of the sheet I trimmed along the cut line approx 3/4 the way across the shear blade then opened it back up much like a hand shear would be operated to take another bite. Then I slid the sheet (to the right in this case) to get the remainder of the cut under the shear blade, aligned and then complete the cut.
Thought I was going to need to find a wider shear again but this technique worked perfectly.

  Jul 08, 2022     Top Skins (cont.)       Category: Fuselage

Okay, so the fuselage top skins require an accurate template in order to fit around the numerous protrusions and fittings. There are two skins, so two templates. The forward one over the passenger cockpit needs holes for the cabane attachments and also the roll wires. These roll wires come up from the firewall fittings, criss-crossing in front of the passenger and attach overhead to the center section cabane attach fittings. Where those wires poke thru could be determined analytically I suppose, but I'm thinking I'll have better results just hooking everything up and see where they come thru. Should produce accurate holes in the template.
Doing it this way will require mounting and dismounting the center section several times. Don't have an overhead hoist, couldn't come up with a free-standing mounting jig and already re-purposed the longeron mounted jig I used earlier. In a brief moment of clarity, it dawned on me I could extend the reach of my engine hoist by simply mounting a longer arm to it. Cobbled together an old six-foot oak hand railing, some hardware and other scrap steel bits. I don't think the center section weighs any more than 25-30 lbs so this should be stout enough to do the job.
I got so excited putting the hoist together, I kinda forgot about the order of build and just hoisted everything up and pinned it in place... At least it all fit so far.
What I forgot about is the top of each roll wire needs to attach to a fitting which in turn attaches to the center section. So I can't hook up the wires until I fabricate those fittings. So some steel cutting and welding is in order while the center section waits in position.
Notably, the center section is quite rigid in position even without the wires in place yet. But if I shove on it, it will rock side to side a bit.
Update 7/11/22. Got the roll wire attach tabs fabbed and installed the wires. Center section is absolutely rigid in position with these wires installed.
Wire holes located, and taped into the template, everything comes apart to remove the template and lay it out on the aluminum sheet. .032 6061-T4. It's a little heavier than the cheek cowls and belly pans but hopefully more fatigue resistant.

  Jun 24, 2022     Cockpit rear panels       Category: Fuselage

Fabbed wood panels to fit behind both the passenger and pilot cockpits. Used 1/8" birch acft ply. Access holes were installed to allow Shoulder harness restraints to strap to the crossbar behind each seat. The aft panel also features the access to the aft storage bin behind the pilot. The current plan is to cover this hole using a sewn leather cover held in place with snaps. That should allow full access to the bin, the harnesses to emerge under it's lower edge and still be secure enough for inflight storage. Considered velcro, but I'm not confident with the drumming and air loads that velcro would hold it in place. Snaps seemed the better option.

  May 13, 2022     Top Skins       Category: Fuselage

Started with the forward-most panel first as it seemed the better constrained since it included two bulkheads (the firewall and the aft pax hoop). Taped up four sheets of tagboard from the office supply place lacking awareness of any better options available. Seems to work okay.
That was a bit premature... consulted the drawing depicting these top skins which is more of a guideline than a plan. Of note, the tops of these skins are parallel to the longerons. First picture shows how the skin sloped down toward the firewall bulkhead. Second and third pics show the next attempt, leveling the top and splitting the aft edge to go over the hoop between the cockpits. The skin over the aft cockpit is also parallel to the longerons and similarly requires the aft edge split to go over the hoop aft of the cockpit.

  Mar 05, 2022     Scallops - (4.5 hours)       Category: Fuselage

I dunno, it's just how I was feeling that day, seemed right... Added some scallops to the fuselage sides at the forward end of the side stringers. Will be covered with fabric, but after shrinking, should give a subtle reveal depending on lighting. Plan is to prime the inside of them white.
Yup. Had an above-freezing day (one) so brought them back to the house to warm up the garage-cum paint booth. Etched, alodined and epoxy-primed the inside (visible) surfaces of the scallops. They're also drilled and dimpled and ready for install, but will wait until the side stringers are final-installed for the last time. The pointy ends of these .020" aluminum scallops are ideal candidates for snagging everything and anything on while going about the business of fabrication. Install could be sooner rather than later, still monkeying around with the throttle quadrants and a couple of interference issues there. Primer instructions state although dry to handle in a couple hours, full cure is 7 days... Special dispensation allowed their placement near an out-of-the-way heat vent for a few days during this unusually cold (even for us) week in March.

  Dec 22, 2021     Headcomb Antenna Farm       Category: Fuselage

The purpose of the composite headcomb is so I can mount GPS antennas under it. These antennas seem to add up for the different avionics boxes installed, so I have room for them out of the way yet convenient enough to wire them to the panel. Hence the term, "Antenna Farm". Also included is the ELT antenna. Fabbed a small fixture to fit the aft end of the farm which the ELT antenna fits into. The antenna then extends into the aft pointy end of the headcomb. A small piece of pipe insulation foam will keep it from banging around inside.
For those who may be concerned with the horizontal mounting, it should be ideally oriented (near vertical) post-impact.

  Dec 12, 2021     Turtledeck Headcomb construction       Category: Fuselage

Glued the hot-wired foam core for the headcomb to a board. Then used the core as a male mold for a fiberglass wet layup. Coating the core with bondo, sanding and shaping was followed by covering it with packing tape. Epoxy will not stick to the mylar tape, so the finished wet layup should release once cured. Once completed, the composite headcomb will be screwed to two aluminum angles along the top of the turtledeck.
The original plans called for a metal headcomb design, folded in a "V" shape. I think a rounded, shape fits the character a bit better and molding it from fiberglass should be a simple matter. As a bonus, fiberglass is transparent to GPS signals, so it should make a good location for the assorted GPS antennas for ADS-B in and out and any navigation boxes antennas. Round top at the forward end is a tuna-can radius which met the pleasing and eye-catching criteria well. Chose the male mold method as I was only going to make one of these. Doing a wet layup over foam, I would dig out/melt the foam afterward then fill and finish the outer surfaces for the completed product.
Later design change involved filling imperfections in the foam core with bondo, then covering with packing tape before the wet layup. Did you know that the solvents in bondo attack polystyrene foam? Me neither. Fortunately, I'd bought the gallon-size bondo can since it was only 5 bucks more than the quart-size (which wasn't a quart) and wasn't sure a quart would do it. After enough iterations chasing my tail filling and sanding, smoothing, filling and sanding some more I got the plug about where I needed it. Trying to keep my options open, figured I'd slather on some finish to fill any pores in the bondo and if I went with the wax/mold release method it would produce a better finish for those (kinda spendy) products. Had an old can of spray varnish of some sort and sprayed a nice wet coat onto the bondo surface... Sadly, whatever is in that stuff also eats foam. That resulted in multiple more craters anywhere the bondo was thin enough the solvents would get through. Yet more filling and sanding. Sheesh!
Finally, I'd had enough of chemistry not playing nice with others so just stuck the tape on it and called it good. It's probably ok.
The bottom edges of the layup form a flange to attach it to the top of the turtledeck. this required forming an inside radius, and I don't have a vacuum pump to suck the layup into it. Next best thing, I cut some strips and clamped them over the flanges and into that radius. Similar clamping setup as I used during rib construction.
Another do-over. After the first wet layup cured, I removed the peel ply to discover gobs of voids and air bubbles in the layup. It looked ok before I laid down the peel ply but I must have somehow worked them in smoothing that out. Any self-respecting Rutan-builder or composite guy would have had kittens looking at the finished layup. I took a more pragmatic look at it and realized it will take more work to smooth out the visible flaws in this first prototype than to just do another wet layup. (And try not to screw this one up.)
Headcomb 2.0: Second attempt used the exact same jig, setup, ingredients and all the rest of it with the lone exception of how I went about it (technique). This time I wetted out all three laminations on a single piece of poly and laid them as a single wet blanket onto the jig instead of one at a time. Next, my hangar neighbor had seen my stubby stipple brush, shook his head and loaned me his composite rollers (I didn't know that was even a thing). The rollers were just the thing to work out any bubbles and ensure the plys were completely wetted out. I left off the peel ply so I could see if any bubbles magically appeared while it cured. Worked like a champ. I will need to surface fill the weave, but this should be a minor fill and sand step compared to fixing prototype 1.
I cut 1" strips of some heavier glass and added two layers of this to the bottom flanges to help thicken them up and add a bit more strength where they're screwed to the turtledeck. Added a forward bulkhead set an inch back to help stiffen things up a little and anchor a future headrest. At three plys the sides are still pretty flexible, so I glassed a pair of 3/8" foam strips on each side back to about the ELT antenna mount (21"). Three plys encapsulate these foam strips which is probably overkill. Yeah, the sides are very stiff now. Could've used 1/4" foam which would have form fitted the interior better and still been more than rigid enough.
Filling the weave now covering the outside of the layup presented lots of options. First tried Poly-fiber Super Fill (the blue stuff) it's nice stuff to work with, but a bit thick for what I was trying to do... took more sanding. Next up was PPG K36 high-build primer. This stuff works nice too. Sprayed on the first coat, then wet-sanded it out expecting to be done. After drying it off and inspecting for pinholes and such, discovered lots of small areas of weave that needed some more. Second coat did the trick. Wet-sanded it out and it's ready for topcoats. I think we're done here.
The "headrest" at the forward end of the headcomb will be upholstered in the same stuff as the cockpit combing, stuffed into the forward end and anchored with screws through the fiberglass. A wood block would have sufficed, but anybody could do that. Besides, Think how heavy that would be. So, the plan is a 1/16"ply framed with 3/4" spruce strips around the perimeter for the anchor screws and upholstery staples to sink into. A quasi-loose fit will allow room for the upholstery covering and still fit the open end of the headcomb. It's probably ok... for now.

  Nov 01, 2021     storage Cabinet - (38.0 hours)       Category: Fuselage

Decided to fabricate the storage cabinet behind the pilot's headrest from 1/16" ply and 1/8" ply base. Scarfed the 1/16" ply top together from five scraps left over from the wing leading edges. Made a paper template by wrapping around the foam buck to determine the required shape/size of the 1/16" top. Likewise, I created a paper template for the 1/8" ply bottom by taping together sections fitted on top of the aft longerons in the desired location. Transferred the templates shapes to the two plywood pieces. In order to keep the structure as light as possible I wanted to minimize any unnecessary structural support. I formed tabs on the bottom edges of the top and corresponding slots in the bottom. Flexing the 1/16" ply around the foam buck, I fitted the tabs into the bottom slots and the structure became self-supporting, even though it was only dry-fitted in place.
Epoxying and clamping the two halves together required some creative clamping using cargo straps. Object was to clamp the glued joints tightly without deforming the very lightweight and flexible structure in the process.
The aft bulkhead is also 1/16" ply and is glued in place utilizing 1/4" capstrip.
For those who like to keep score, I weighed the completed box after it was completely finished... 3 lb, 10 oz. plus another ounce and a half for the attach hdwe.
Didn't think to weigh it before finishing, but I wouldn't have guessed it weighed nearly four pounds! I mixed up two batches of epoxy varnish during the finishing steps: an 8 oz and a 6 oz batch. Some share of it flashed off and any that wasn't stuck to the box either fell to the floor as overspray or was disposed of, but it wasn't much more than a dribble in the bottom of the spray cup.
The structure is fitted around the shoulder harness support tubes and held in place on the longerons by four screws through the bottom and threaded inserts on the forward edge of the top piece will be used to hold it to the formed steel angle behind the pilot's seat. There is also a single D-ring tiedown lug located in the center of the box for securing items.
After epoxy varnishing, the unit is secured to the longerons under the rest of the turtledeck structure.

  Oct 26, 2021     Foam cores - (8.5 hours)       Category: Fuselage

Cut a pair of foam cores from pink construction foam (polystyrene). Used the hot-wire technique used by Rutan-style builders and modelers for decades. Borrowed the cutting frame constructed of EMT conduit. Nichrome cutting wire was broken, so replaced with 0.020" stainless safety wire. Tensioning was accomplished with a turnbuckle on the top wire. Power source was a 16VAC model train transformer ca.1963 borrowed from another neighbor. A 19V computer power source would have also worked. The foam was cut from a full sheet, the cut pieces stacked and glued together with spray adhesive.
Templates were cut from scrap 1/8 and 1/4' fiber board and attached with large nails pushed into the foam. The preparation process took the majority of the time to complete these steps. Once heated, the wire cutting process took only a few minutes.
The wider core will be used as a buck to fabricate a 1/16" plywood box to fit behind the pilot seat on top of the longerons under the turtledeck. The longer, tapered core will be used as a male mold forming a wet layup fiberglass headcomb. The last photo shows their relative positions on the aft fuselage.
The plan is to locate the GPS antenna "farm" under the headcomb, out of sight, as it will be fiberglass and transparent to the gps signals.
Ultimately, everything in the pictures will be tossed out and only the shapes will be retained (hopefully) in the completed components.

  Sep 21, 2021     Belly access panels - (32.0 hours)       Category: Fuselage

Decided to run sheet metal on the belly aft from the firewall, past the forward gear attach as shown on the plans, all the way back to the point where the aft wing spar attaches. This comes in the form of two additional panels aft of the one in the plans attaching to the firewall.
I started with the aft-most belly pan constructing a framework of 3/4 X 3/4" .063 angle to frame the opening and attach the pan. These will allow access under the cockpit floors without removing them or standing on ones head to service systems located there. The middle pan is the smallest, just over a foot length fore-aft and will locate just aft of the forward gear mounts. The fabric covering on the fuselage will wrap down the sides, over the lower longerons and then glue down onto the 3/4 angle framing these openings. Nutplates will be installed along their length to allow #8 machine screws to hold the panels in place.
I installed two transverse stiffening "ribs" across the aft-most pan and antenna attach doublers for ADS-B installation. Two pads for two xpndr antennas- one for "In" or receive and one for "Out" or transmit. I don't know why, just what.
The smaller, now middle pan got a larger doubler for an external VHF Comm antenna. I intend to install a VHF Comm dipole antenna inside the aft fuselage and out of sight, but in the event it doesn't work, that pad will be available. More about that later.
The forward-most belly pan attaches to the lower firewall and requires some shrinking along the aft edge to conform to the fuselage bottom former it meets there. Also installed a pair of longitudinal stiffeners in this forward belly pan. This should complete the bottom of the fuselage pre-covering work.

  Apr 15, 2021     Fuselage top skin attach - (10.5 hours)       Category: Fuselage

The fuselage top skins are attached to the square tubing outboard of the top longerons. The mystery (to me) of why these 1/2" square tubes are specified to be 0.065" thick material is clarified by numerous builders utilizing "nutserts" (there is nothing in the plans about this or the attach hardware). Nutsert threaded inserts are installed similar to a pop rivet using a heavy duty install tool, and the thicker wall tubing allows the nutsert to grip better. There is a similar product called a rivnut, which I have used before and would characterize as "LAME", not recommended for installation in anything traveling higher or faster than a skateboard.
I am given to understand Nutserts are more robust than the aforementioned rivnuts, but I'm not willing to trust. So, I am welding 0.035" tabs to the square tube which will accept #8 machine screw tinnerman-style nuts. This choice is likely to be heavier, more expensive and take longer to fabricate the first prototype than if I had sucked it up and just used the Nutserts...
Another reason I went with the tabs is that they can be angled to match the contour of the top skins as they meet the fabric covered fuselage sides, allowing the machine screws to insert normal to the skin surface instead of at a slight angle. Hopefully, this would improve the appearance of the longitudinal line of screws along these seams. A smart guy (read Murray Marien of Saskatoon) would have simply installed these square tube side stringers rotated at the slight angle required for the hardware to attach normal to the skin surface going directly into the Nutserts. Way to go Murray, nice job!
Twenty-six tabs later I have attach points, but not all the way to the firewall... I tabbed the square tube as far as it goes but it stops at the point where the steel side formers meet it. I am presuming at this point that the side skins just aft of the firewall meet the top skins along that line at that location and nutplates are installed in the top edge of the side skin to which the top skin is screwed. Therefore, no longeron-like square tube with tabs or Nutserts is required beyond this point.

  Apr 03, 2021     Aft Fuselage Bottom Cover - (5.5 hours)       Category: Fuselage

Fabbed the fuselage aft bottom cover. Three screws along the forward edge hold it in place along with the aft bracket that slips over the forward tailspring mount tube. Shamelessly copied the design from D. Simmons' Hatz Classic #006.

  Jan 09, 2021     Blue Tape - (3.2 hours)       Category: Fuselage

Progress as of lately has been slow. Goes like this: Determine location for a selection of postage stamp sized tabs which are generally not in the plans, establish dimensions for same including thicknesses, do some homework reviewing other designers biplane plans to try to figure out what they did, evaluate if two tabs in a select location are adequate or would one be better? Once the aforementioned has been completed/determined, begin fabrication in preparation to weld in place onto the fuselage structure. This process includes cutting the steel, be it plate, angle or tube, round or rectangular, then machining, drilling or other processes. Not necessarily in that order. Once complete, cleaning is necessary to ensure a proper weld, buffing the component to bare metal and wiping off with acetone to ensure no contaminates remain on the part to be welded. That's half the job. Next up the location on the fuselage structure needs the same cleaning process. Buffing top bare metal, chemically cleaning.
But wait! Should these tabs include riveted/welded nutplates or is it possible to install them once welded in position? Oh yeah, are there possible interference issues locating them here since everything seems to intersect everything else in an airplane. Take a moment to be sure... as sure as one can be at this point.
Once fabbed, drilled/machined, deconflicted and presumably located correctly they need to be jigged in position. Since holding with ones fingers a small tab while welding with white-hot plasma less than an inch away is largely impractical, they need a fixture to hold them in place. Just about every one of these requires a different combination of clamps, bars, threaded rod or other fixture. Even symmetrical tabs will each require a different setup due to access issues a right-handed rookie welder faces while contorted within a steel tube truss structure. Once jigged in place, aforesaid welder will also likely need some level of support as well. Often as not there is no place to brace ones hands using fine motor skills to perform the weld, usually necessitating clamping a board or other fixture in place for such support... for each such weld.
So today I stuck a labeled piece of blue masking tape at each location on the fuselage where each of these tabs should be welded in place, and a number of other weldments such as tubes, angles and frames. When I couldn't think of any more I stepped back looking at the cumulative process remaining. The fuselage structure was festooned top to bottom in little blue swatches of tape. Each one (or pair) requiring the process outlined above.
The above exercise is to prepare the fuselage for painting/powder coating. Since I don't wish to discover I need to add some weldments AFTER having painted or powder coated the structure.

  Nov 21, 2020     Raising the shoulder harness restraint Level - (9.5 hours)       Category: Fuselage

Okay, it's not in the plans but I think I need to do this. Being 6'-2" I don't fit a lot of things and from the second picture below one can observe my sitting height (without a seat cushion in this case) places my shoulders a few inches above the upper longeron level. The design shoulder harness position has them coming across the upper longeron crosstubes which is too low for me. The concern is if they are ever required in extremis and they are mounted too low relative to the shoulder level, then excessive spinal compressive loads may cause more injuries. Reviewing Tony Bingelis books Aircraft Construction Methods, Dave Russo's book "Construction of Tubular Steel Fuselages" and Van's Aircraft builders manual recommends a range of angles from no lower than 5 degrees below shoulder level to avoid this problem.
The structure pretty stout. The crossmembers are 7/8"X .058" (most of the fuse structure is 3/4"X .035") and the four support legs and braces are 3/4"X .049". The only other structures using this dimension stuff are the landing gear legs, engine mount and tailpost. Probably okay.

  Nov 15, 2020     Fuselage bottom stringer construction - (22.0 hours)       Category: Fuselage

The bottom of the fuselage will be fabric covered from about the rear spar attach point aft to a point forward of the tail spring. Stringers will extend between steel hoops anchored at those locations. These stringers are the same hat-section aluminum material used on the upper turtledeck. There are four, requiring additional support between the two steel formers at each end, similar again to the upper turtledeck. Soft, 3/8" aluminum tubing formers attached to 1/4" dia steel tube stubs welded to the lower longerons, located approx 16-18 inches apart.
Forward of the aft spar attach, the center 18" of the belly will receive removable aluminum panels to access systems and areas below the cockpit floors. The openings for these panels are framed in 3/4" .063 aluminum angle

  Nov 14, 2020     Turtledeck construction - (42.0 hours)       Category: Fuselage

Okay, so this portion of the build is going to take a while completing and will be coming back to it periodically. Starts with the steel "hoop" welded to the top longerons behind the pilot's seat, to which aluminum "hat section" stringers are attached which taper aft towards the tail. The "hoop" starts as 4130 steel plate approx 1-1/2" wide, is bent into a 3/4"X3/4" angle then one edge is "shrunk" forming the curved shape. I formed it in two halves because I couldn't bend up a single piece in my brake and didn't have a long enough piece anyway. Will weld the two together after shrinking. This chromoly 4130 steel in condition N is remarkably tough and springy. This is a good thing when building race cars or airplane fuselages one intends to strap their soft, pink butt into someday. However, shrinking it as-is can make for a long day. Shrinking a 2-ft piece every inch will result in about a 1/4" bow in the piece (this is not much). As a casual observer of most things metallurgical, on a functional level I reasoned annealing the flange to be shrunk may soften it enough to achieve the shaping I required. I did so with a Mapp-gas torch (O-A would work too) and the first picture below shows the results of the first pass through the shrinker for both halves. Much improved results. The part quickly work-hardens and may need additional torch work if not completed on the first pass.
Small, bent up V's with welded tabs were fabbed and welded to the aft side of the completed hoop, which is then welded in it's entirety to the top longerons. These V's are used to mount the aluminum hat-section stringers via blind rivets.
The top turtledeck aluminum stringers are supported aft of the tabbed steel hoop by four aluminum hoops fashioned from 3/8" soft aluminum tubing as seen in the fourth picture. Each progressively smaller, these aluminum hoops are anchored to top longerons by short lengths (approx 3/4") of 1/4" X .035 steel tubes. The hoops slip over the top of these stubs and will be drilled & pinned in place with cotter pins. The hat-section aluminum stringers rest on top of the aluminum hoops where the plans call for 1/16" pop rivets - haven't found any such pulled rivets yet- maybe they exist, but I think I can use 3/32" pulled rivets, those I can find. Interestingly, the stringers do not project aft in a straight line as they collectively converge, but have a very slight outwards bow similar to the side stringers. As the fuselage side fabric comes up from the wood side stringers onto the aluminum turtledeck stringers, it bridges the upper longerons leaving a flat spot in the curved side. To eliminate the flat spot a shaped mahogany strip will be bonded to the longerons aft of the tabbed steel hoop at station 84, terminating at station 151, just under the horizontal stab leading edge. This strip will act as another side stringer shaping the fabric as it comes up around the fuselage.
Finding the right shape for the aluminum tubing formers is becoming a bit of an iterative process. Initially bent the four to the shape shown in the drawings after blowing them up 400%. Good concept, bad in practice. Only three of them would fit the fuselage at the alleged locations and their sorta elliptical shape, though looking good on paper, don't taper properly behind the welded hoop at the front which is essentially a semicircle. Also, there is the matter of bellying out the stringers similar to the wood stringers below... not observed. Established cardboard templates for each tubing location to achieve said tapers, then re-bent tubes to match. Complicating matters, the headcomb yet to be fabbed screws to the top of the turtledeck into two 3/4 X 3/4" aluminum angles which run along the top of the turtledeck on either side of the headcomb. The angle's flanges point down from the surface of the turtledeck top interfering with the bent aluminum tubing formers. To avoid cutting or notching the angle's flanges, I bent a flat spot at the tops of each former to allow clearance for the angle.
I'm thinking now it really doesn't matter notching the lower flange on these top angles and will now re-form the tubing formers back into a curved top shape, notching the angle as necessary. The angles will be pop-riveted to the formers like the hat section stringers and the resulting structure plenty strong along the top even with the notched flanges on the angles.

  Oct 05, 2020     Side stringer construction - (71.0 hours)       Category: Fuselage

Began construction of the side stringers earlier with full size templates of the wood formers/spreaders required at four locations along the fuselage sides. The forward end of these side stringers anchor to a formed steel angle welded to the fuse. It is 0.035" 4130 steel formed into a 3/4/ x 3/4" angle and shrunk along one side to form the required curve. Tabs are welded in six spaced locations along each steel former to which the wood stringers will attach. First photo shows initial curve developing after a few passes through the shrinker. The topmost penciled curve is the required curve for these pieces. The piece work hardens after multiple passes through the shrinker. I heated the edge that had been through the shrinker, effectively annealing it which allowed me to continue to shrink to the required curve. Began the wood side stringers construction by picking up 8', clear, straight-grained 3/4" mahogany boards on the aviation aisle at Menards. Ripped the boards into 1" strips then ripped again the strips into two 1"X5/16"strips each. Next, routed a roundover along the edges. The stringers are something like 14 feet long, so each stringer requires two of these strips scarfed together end-to-end using a 12:1 minimum slope on the scarfed ends. The stringers are spaced (6 each side) along the side by four wood formers and the formed, curved steel angle at their forward end.
Used foam-core tagboard to lay out the side former templates and fabricate them from 1/4" birch veneer aircraft plywood. Also used in determining/confirming the stringer layout and spacing along the sides. Once fabbed, the wood side formers are attached to the fuselage with two welded steel tabs each... Sixteen steel tabs each requiring individual jigging to locate and hold them in place while welding. No specifications for these tabs in the plans. I used 0.065" X 5/8" X 1" 4130 steel tabs and #8 machine screw hardware.
Wood stringers and formers will receive three coats of PloyFiber epoxy varnish prior to assembly.

  Sep 06, 2020     Systems installation - (15.5 hours)       Category: Fuselage

With the majority of the structure completed, time to turn to internals. Trim system install, brake system, floors, controls, fuel, etc, etc. Also included will be multiple (as in LOTS) of tabs and angles for stuff to attach to the structure. Formers to support the fuselage stringers and turtle deck structure, cockpit coaming supports. As these will require all-aspect access to fab and weld in place, am planning to remove the gear and mount the fuse on a rotisserie. Following that process, I am planning to either paint the fuse with an epoxy primer or get the structure powder-coated. TBD. Hopefully I won't have forgotten to weld some extraneous tabs or angles in place. First up was the elevator trim system, cable mount, handle and mount etc. Can't put the floor in without first putting in the floor supports. Generally fiddly channel bits fabbed from 3/4" rect tube split down the middle and inserted #8 nutplates before welding usually in outboard corners of each floorboard panel. Started the brake master cylinder mounting bracket but ran out of the size tube required to weld into the fixture so it's on hold until more shows up. Guess I'll put pictures of that in the wheels/brakes section. A couple more systems install include the fuel shutoff valve and ELT bracket mounting tabs.

  Aug 16, 2020     Engine Mount - (88.0 hours)       Category: Fuselage

I have a Lycoming O-320 with a dynafocal I mount, but the plans only included drawings for a conical mount Lycoming or a Rotec radial. Studied the Dynafocal mount drawings of Pitts, Acrosport, Skybolt and Starduster which are all similar. I essentially copied the designs, inserting the Hatz tube sizing and engine CG location. Initial steps included building/repurposing the former C/S support box from the cabane saga into an engine support and prepping the firewall wrapper gussets to accept the 3/8" mount bolts. The engine support box holds the engine level with the longerons at the proper height when both are blocked on the table. Plans call for zero downthrust and zero cant (usually right, if any) with the engine CG 2" below the longeron centerline. I purchased a Dynafocal ring from ACS&S and bolted it to the engine using the required rubber isolation pucks. Located the engine CG fore-aft per the plans and aligned the engine and fuse C/Ls using taut lines and a laser line. Sandbags on the fuse enhanced mean ol Mr Gravity's ability to keep everything in position while fabricating the mount. Fabbed the four lugs at the aft of the mount that bolt to the firewall using steel bushing mat'l and 1/8" 4130 steel, Then bolted them to the firewall using the modified 3/8" bolts shown in the last photo. (The bolt shanks were ground with three flats along their length to minimize the chance of welding them into the bushings while tacking the mount tubes to the bushings.) All that remained from this point was to connect the dots from the aft lugs to the dynafocal ring. Bob's yur uncle. A couple of points; I didn't want to cook the rubber pucks while tacking all that tubing to the dynafocal ring structure, so several small, quick tacks and wet rags to help keep them cool. Finish welding would be off the engine. The X-brace on the lower half of the mount is concaved aft to clear the oil sump and allow access to the sump screen. There is also a finger strap gusset added to the center of the X to reinforce same. Finish welding was completed off the engine and finally off the fuse. Using the same techniques on the tube clusters as the fuse, by moving around from point to point and not concentrating too much heat at any point at any one time. The gods of mutually-offsetting errors allowed the completed mount to fit back on both the engine and fuse. Finally, the firewall wrapper gusset holes were enlarged to 1/2" to accept steel bushing and plate weldments. These were welded to the firewall forming the firewall hardpoints/landing pads for the mount and accept the 3/8" mounting bolts.

  Jun 23, 2020     Cabanes - (111.7 hours)       Category: Fuselage

Began fabricating the cabanes which effectively connects the fuselage to the upper wing center section structure. The process began by welding tabs or "ears" to the top longerons at the specified locations and the proper angles (both fore-aft and laterally). Inner and outer layers were then added which also act as finger strap gussets and were heated, formed and welded to the adjacent tube structure. The three layers were then edge welded together, bored to accept bushings which were in turn welded into the tips of each ear. Once complete, a box was built to hold the center section on top of the fuse at the specified height. Ultimately, six plumb bobs were used as well as digital and spirit levels to locate the center section in the five remaining axis' (fore-aft, lateral, pitch roll and yaw). Once located, sandbags and straps were added to hold it while strut fabrication began. Steel tube bushings were fabbed and inserted with temporary bolts to the C/S plates at the cabane attach points. Streamline tubing was fitted between the fuse "ears" and C/S attach bushings, tacked in place, removed for more complete welding, reinstalled for more fitting, tacking, removed again for more welding and repeated as necessary until complete. Once the forward cabane V's were welded, built a drilling jig to accurately drill the base of the V's to the fuse "ears". Reinforcements were welded to the forward legs and attach straps/reinforcements were added to the aft V legs. The aft cabane struts were constructed much the same with the addition of threaded inserts at the bottom to accept threaded forks which in turn attach to the aft leg base of the forward cabane V's.

  Sep 21, 2019     Fuselage structure - (259 hours)       Category: Fuselage

Fuselage structure began by bending lower longerons. Filled and packed with fine grain pool filter sand, plugged both ends and bent on worktable around dimensional lumber bending blocks. Templates for bend angles were drawn on the table and tubing was bent cold to match. Fuselage jig table was painted with white primer paint and fuselage side drawing was laid out in pencil. 3/4 X 3/4 X 2" blocks were screwed in place to hold tubes in place for jigging and tacking. For repeatability, the second side will utilize all the same jigging. The majority of the required fishmouthing of tube intersections were 3/4" cuts and the majority of them could be done with the 'ol Joint Jigger. Worked like a champ! Was concerned the only 3/4" hole saw (required) I could find was a bimetal Milwaukee unit with eight teeth! Was looking for something maybe carbide or something like 14-15 TPI but no luck. Anyway, completed the majority of the fuselage cuts with this one holesaw and its still working (go slow, lots o cutting fluid). After the sides were tacked together except at the tailpost, the sides needed a bend to match the aft fuselage taper. This was done by clamping and heating the longerons aft of the cockpit while lifting and blocking the end of the structure a measured amount (used the sine/cosine thing) to achieve the required taper angle. Standing up the sides, cutting and fitting all the crosstube structures presented the challenge of keeping everything not only located properly but square, plumb and level. The plywood jig "bulkheads" were inserted, screwed to the table square and safety wire with turnbuckles was tightened to the longerons diagonally across the bulkheads to hold everything square. Ultimately I used four of these bulkhead jigs. Saw the technique in the EAA Acrosport fuselage drawings. Prior to cutting off the excess length of forward longeron, I recommend the tennis ball intervention. This, after performing the no-notice punch biopsy on my own head. These will help minimize the amount and locations you leave your DNA around the project... functionally checked them multiple times after, ops checked ok. Keep a few bandaids around anyway. The tailpost presented not only the problem of getting it in square, but also once installed it would complicate rolling the fuse around on the table for other welding/fabrication duties. Some have installed a stub tailpost to which the vert fin would bolt later eliminating that problem but potentially creating more. I figured anybody could do that... so I went with a surrogate 7/8" tailpost as a stand-in for the real deal. Fishmouthed and welded the tube structure meeting at the tailpost with the exception of the welds to the tailpost proper which will come later. Used the online fishmouthing templates from metralgeek.com to get the proper shaping on the longeron ends... made a potentially nerve-wracking process just a simple deal. The rolled-up paper template can be seen next to the test-fit longeron ends picture. Big THANK YOU to the metalgeeks, sure glad there's people around like them can figure stuff like this out and make it simple enough for mouth-breathers and knuckle draggers like me to use. After more internals are fabbed and installed, will mount the vertical fin with the proper offset (1"). So on to seats, controls, landing gear and wing mount fittings.