April 30, 2005

Clasps



Finished drilling the holes for the stiffeners and canopy frame/skin. Since I NC drilled the six little clasps called for in the plans to tie up the notched stiffener webs, I can interchange them with one another after everything is prepped for final riveting... (i.e. I won't have to individually mark the little rascals and their respective locations.

April 29, 2005

Splice Plate









Details, details... After tweaking the rib positions to get the fit just right with the canopy, it was time to finally drill the splice plate. I took advantage of the NC drilling of the plate to put it on the front side, drill the holes and cleco it in place on the back side where it belongs.

I originally was thinking of making a huge dimple like die to do the shallow stiffener formation around the 2 inch holes on the canopy stiffeners. Vans suggestion to use a wooden block, cut a notch in it and do them by hand works just fine... Take your time and don't try to do the full bend all in one shot.

With that done, I found using some short sections of wood worked fine to pinch and hole the various tabs so you can bend them into position. Takes a little fiddling with getting the angles close enough for clamping and then drilling. I found it was better to drill the stiffener to the canopy frame, put the assembly back on the fusalage, and then drill the stiffener to the skins in place. I have a couple holes yet to do, but boy those three little pieces of sheetmetal sure stiffen up the assembly.

April 28, 2005

Experiments







Been a little under the weather with a cold, so it's a good time to get some Spring Cleaning done. Now that I can get in the shop without having to use a shovel I moved things around and lo and behold the cowling just fits on the fusalage. Accoringly the moose mascot is getting a little closer to the door.

I have ordered the special drills needed to drill plexiglass. I did some experiments with the scrap pieces and yep, a regularly ground drill "dinner plates" the surface where the drill exits. By dinner plating I mean the surface gets a plate-like chip to fracture away at the suface (an ice climbing term for what happens with water ice when you use an ice tool and get lousy placements).

Grind a 1/4 and 5/16 drill to plexiglass specifications and you get a nice burrless hole. Still, I'll wait for the drills to arrive that have been ground on a properly equiped tool and cutter grinder, as to do things right I would have to take my Bridgeport's head out of square with the table and that means spending quite some time fiddling with a dial indicator to re-square the head. Besides, there is the few odd drilling and riveting tasks yet to do before drilling the canopy to the frame.

April 25, 2005

Greyscale

It's been raining and I got a sour throat... A good time to do some more snooping on terrain database issues for the artificial vision software:

Took a little finagling, but courtesy of my freind John Babiarz of Intergalactic Software I am now the proud owner of downloaded one arc second terrain data from one of the early shuttle missions courtesy of NASA... Took about 14 CDs to burn the files for the United States.

The grayscale jpeg is the result of some quick and dirty brewing of a C program to read the data and generate an (originally) xpm formatted image file (xpm files are human readable... i.e. debuggable). One degree of arc longitude and latitude in the data corresponds to a 3601 by 3601 matrix of sixteen bit elevation data points in meters. At my location that looks to be about one data point overaging radar returns for a 90 foot by 90 foot patch of lawn.

April 23, 2005

Contour









Friday I got the canopy to about its final trim state. I found it useful to take the front skin off so you can develop the trim lines on the front of the canopy consistent with the surfaces of the underlying weldment. Note, the weldment starts off as a vertically oriented triangular section which then transitions to the rounded section over the top of the fusalage. This transition and flat area make clecoing and drilling the shit to the lower edges difficult due to the significant springback force put out by the sheet.

I elected to use my homemade break to bend in the the transition line to follow the surfaces of the weldment. When you do this, the sheet fits much easier and has a nicer fit on the canopy frame. With the canopy and sheet trimmed and the break line in the sheet, the required fitting for the canopy to pass through the "ears" on the sheet becomes a bit more obvious. I found so far most of the "ear" fitting can be accomplished with a duct taped bucking bar foot and a few raps of a mallet. I'll file the final contour later.

April 22, 2005

Masking





Left the side skirt trimming until after the canopy was cut. Now to prep for the cuts... Peeling back the vinyl and taping adjacent to the cut lines works well here as you can use a Sharpie to mark the cut line on canopy frame and look through the canopy to mark your lines.

April 21, 2005

Slicing











Cutting the canopy turned out to be a non-event. What made the final cut almost trivial was the plywood and stiff cardboard (from the shipping crate) bulkheads I cut using the rollbar as a template. I figured the canopy would become a wiggling mess and invite problems if I didn't stiffen the two sections prior to cutting them. I've always figured out a lot of technical and tooling problems in my sleep and this idea was no exception.

I first tried making a stiffener out of 1/4 diameter steel rod but concluded it was too flimsy. Duct taping the temporary bulkheads about 2 inches from the cut line worked great. I also supported the overhanging end of the rear window with widges to keep the stresses down and avoid problems with binding. Finally I duct taped the cut as I went along to keep the pieces together until the end to keep from wedging the cut line and risk generating a crack.

April 20, 2005

Preparing







I used the rear of the canopy's initial trim as a warm-up for ultimately splitting the canopy into its front and rear halves. What I found to be more accurate, easier, and less likely to loose track of my line was to strip the vinyl adjacent to the intended cut, then mark the plexiglass directly with a Sharpie. I then place masking tape just short of the cut line and use it to secure the vinyl down, so no chips get burrowed in underneath and cause scratches or gouges later. You have to be careful even with the vinyl coating on, I scratched the vinyl when I flipped the canopy over for some trim work, luckily I didn't scratch the plexi. It was a wake up call and I've put a protective pad on the top of the canopy.

Getting ready for the splitting, I found you have an interesting parallax problem lining up with the line on the roll bar. Since they are seperated by a 1/4 inch you have to keep yourself lined up along the line so to speak. I started with a bunch of dots then went over them with a ruler to draw the line. By the end of the day we had the canopy marked and taped for the split, and the boundaries approximated for the rear window.

April 19, 2005

Transitions





Vans plans call for tweaking the transition area at the front corners of the canopy plexiglass/frame contact point. My strategy was to continue the bend line based on the front weldment. Bending the tab for the plexi transition was a bit of a pain. It takes a lot of oomph and you do not have a good set up to work with. I found the welding clamps with the flat faces could be improvised into working as mini-seaming plyers. At this juncture, early in the day I had the front of the canopy pretty much initially trimmed... Now for the back.

April 18, 2005

Fitting


Light day today, but I committed to doing the trimming of the front of the canopy. I found you can use these scotchbrite pads (green) to round the edges and remove the nicks inherent in the cutting process.

Nice and toasty in the house at 85 degrees. The dog wanted out and the cat just loved sprawling out on the floor. I was sort of tied to the bathroom in preparation for a colonoscopy. Since I'm 50 my doctor suggested it as a screening tool.

I thoroughly support the concept of testing, and everybody at Dartmouth Hitchcock was great: I fell asleep while they were prepping and didn't wake up until I was back in the recovery area. The hard part is drinking the solution the day before.

All clear on the test. Still, before you do it you do get some anticipation anxiety, wondering what the then unknown results will be. Sure beats getting some really bad news because you waited until your 60s or 70s...

April 17, 2005

Trimmings








I'm starting off slowly on the canopy. My first trimming was just of the flash outside the clamping area used to form the canopy. Learned that you can peel back some of the coating and trim it away from the cut area using masking tape to seal the edge. This way you do not get any particles stuck under the vinyl and you also inhibit the vinyl from peeling back.

Cathy and I put it on the plane just to get are bearings. The front is now taped and marked for cutting. I want to think about it a little more. Vans calls for cutting plexiglass at 75-80 degrees. I got the dining room up to 80 with the wood stove.

April 15, 2005

Easy Street










"When life looks like easy street, there is danger at your door" Uncle John's Band, the Greatful Dead

It was just one of those days. Riveting went nicely, but then uh-oh... The one tab is on the wrong side of the assembly - Argh! Okay, drill em out and re-do em right this time, BOZO!

I use a scrap barrel for a short barreled M16 to back-up the rivet being punched out. After drilling the head off, whack it with a punch using a quick snapping motion with the hammer. It takes a little practice but when you do about 10,000 rivets or so you occasionally get to work on the ...skillz.

Important Safety Tip: Don't own one of these barrels if you only own an AR15 :)

The end result came out pretty good and I'm happy with it. Then it was onward and upward to figure out how to wrestle the canopy plexiglass into the house. I figure with it on the dining room table adjacent to the wood stove we can crank up the heat to do the initial trimming Van's calls for.

Wish us luck on the trimming and fitting!

April 14, 2005

Recycle




I like to use a file to remove the shear marks from parts, rather than just relying on a scotchbrite wheel, to inhibit fatigue cracks. The parts for the canopy frame by evening are hanging in the back room to cure. We should be able to rivet the frame together tomorrow and possibly take a first peek at the canopy plexiglass on the fusalage. Have a tooling issue to look into for doing some forming on the canopy stiffeners that come with the tip up option.

April 13, 2005

Tooling












Started with a quickie piece of tooling to line the holes up on the side rails. I initially pieced the parts together and eyeballed the fit for a quick check. That was a good exercise in seeing how much trouble you can get in if you check everything. What I found helped systematically set up the parts for drilling was to start with the two ribs forming the arch.

I scaled the print to figure out the theoretical position of the ribs to the side rails and started with that as a starting point. Set the ribs to 3/8 inch above side of the fusalage and inboard by 5/32. I also used a straight edge to get the side rails in line. Once I worked out all the positions and clamps to hold everything, the drilling was then fairly straight forward.

By the end of the day I had completed all the necessary drilling and now it's debur dimple/countersink prime and rivet the framework together to the point of starting to fit the plexiglass. I didn't expect the canopy frame to work out to where I would be drilling it today.

April 12, 2005

Workstation








I figure if Kelly Johnson could build the F-80 shooting star prototype in a tent, riveting off the wood stove is an acceptable work environment. Besides, the work height was perfect.

The real fun today was doing the checking, checking, tweaking, and checking before drilling the canopy hinge. My approach was different than Vans proceedure in that I clamped the aft end of the canopy frame in a position simulating the finished height and then gingerly unclecoed the front top skin and clamped the hinge parts together. Then it was just a matter of running an undersize drill through the hinge blocks to serve as a drill jig. With a pilot hole drilled then you just run the 1/4 ream through to set the final hinge hole location.

I then took everything back apart and reconfigured the drill press so I could then locate the 1/4 ream in the hole, clamp everything in place and then drill/ream out to the 3/8 bore, then just press the bushings in place and ...Voila, done! This approach avoids drill walking and drilling at an odd angle, inherent in using just a hand drill. The first stage drilling and reaming uses the thick side of the fusalage blocks as a drill jig and the drill press setup maintains a straight hole. This is a variation on the approach I used to drill and ream the hole in the rear spar of the wings.

Killed the whole day on the hinge drilling and reaming, but the results paid off. The only "oops" was some minor interference (too good a fit) between the skins just above the hinge and I had to use an 0.020 shim to lift the canopy skin.