ISON Tandem AirBike Builder's Log

September, 2000 -- Visible progress!

 

I've been working on the aileron portions of the left wing lately, and am happy to be making progress again. It is interesting and weird to find that going from a life of relative leisure back to the 8-5 working grind helped me make better use of my time and get busy in the workshop again...

Cutting the 1/16" x 1 1/2" x 1 1/2" TE gussets with the little Makita carbide blade (as described in my gussets section). I'm using a piece of 1/8" plywood with two 90° faces as a guide to keep the workpiece square as it traverses the blade.

Here the square gusset blank is chamfered on all four edges with a sanding jig that I resurrected from my last airplane project. The blank rides on the small ledge as it is guided across one of the rollers of my 6" vertical edge sander. Exposing as little of the sanding belt as possible is key to making this a safe operation.

Here's the ass end of the chamfering jig so you can see how it's made (quick and dirty). The metal bracket which secures the angle of the top platen is a wing attach fitting from an old Sky Pup project.

On the right is the TE gusset as it comes off the chamfering setup. On the left is the gusset installed, with the staples removed and a light hand-sanding which rounds all of the corners nicely for the fabric.

Here's Robert using the thicknessing attachment I made for the edge sander. He first resawed the spruce with the bandsaw setup at right, and now he's sanding off the irregular bandsawn edge while controlling the thickness at the same time.

I haven't raved about my 6" edge sander in these pages yet, but I've been meaning to. It is by far one of the most useful tools in my shop, and if I had to choose three power tools that I couldn't be without, this would be one of them. Got an irregular curve to profile in a 5" thick piece of oak? Put on a 40 grit belt and you won't believe how fast this puppy will "hog off" the material. Got a piece of 2 x 4 with a severe twist? Hold it up against the platen for a few seconds and now it's flat. Got a delicate little chamfer to cut in 1.5mm aircraft plywood? Put on a 80-100 grit belt and you can remove a gnat's ass with this thing. As long as you keep in mind that heat = death and act accordingly (just as with engines), your belts will last a long time. (I've used those Craftsman stationary belt sander things which go vertical or flat, but they don't begin to match the usefulness of this rig. If you could orient the belt as shown here and build a work table around it, you might have something.)

I can't recommend this tool highly enough. It is unbelievably powerful and versatile, and I use it constantly for fitting parts. It is so easy and fast to cut something oversized with the bandsaw (or whatever) and then quickly sand it to the pencil line with the sander. Mine is a "low-end" model imported by Belsaw, and I got it years ago for a little over $400 (the automatic dust collector lying on the floor is extra). Grizzly has a nice-looking model on sale for $420, but I can't vouch for its quality as I haven't seen one "in the flesh". I bought a cheapie, removed the table attachment and added my own wrap-around work surface. This makes the tool more versatile as you can attach jigs in any position relative to the platen or spindles, and this also helps manage large workpieces such as large sheets of plywood. Here you can see the ever-useful 90° fence clamped to the table...

...and the suction hood I've developed over the years. The hinged flipper swings out of the way for sanding long straight edges.

This detail shows a small addition I made to the aileron spar web slot in the hinge ribs (ribs 5 & 9). The arrows point to fillers that are not specified in the plans. This is one of those things that isn't necessary, but I feel a lot better having the hinge bushing bolts supported all the way around in this manner. These fillers started out as one piece of 1/8" plywood (spar web material), and then the 1/4" bolt hole was transferred through as shown in the July update. As far as I can tell, this gap doesn't ever get filled when built by the plans.

Cutting the slots in the ends of the aileron spar webs. I drilled 1/2" holes to create the specified 1/4" radius and then finished the cut with the bandsaw. These slots will wrap around the gap fillers I described above.

Here's a view of the hinge assemblies in place. The large AN washers conceal the gap fillers I added. Now it's time to slide in the 3-piece aileron spar webs. I got a little ahead of the game previously and prematurely glued the root rib to the wing assembly, so now I find that the webs can only be inserted from the tip of the wing... but with my clever little gap seals in the way, only the outer web will go in now. Robert sagely suggested that I cut the two inner spar webs in half, so that I could wiggle them in and then scab them back together. This turned out to be an excellent plan. It added a few grams of weight, but turned out to be a very convenient way to fit the webs to the ribs.

With the aileron spar webs in place, it was time to make aileron box ribs, which surround the hinged areas of the ailerons, making a box structure. The plans say "Use existing rib jig to make (8) aileron box ribs -- (4) with plywood on right side, (4) with plywood on left side." I couldn't figure out how to use my rib jig to produce these short assemblies and hold the curve on the top cap, complicated by the plywood being on alternating sides, so I punted and made this box rib mold from 1/4" plywood. The caps are fitted into the mold, and the 3 sticks in the middle are temporarily wedged in to force the caps into the mold's profile. The 1.5mm ply face is glued and stapled to the caps, and the assembly is removed from the mold to start another one.

I love getting to the wing assembly stage of the project, but I hate losing my work table for all other uses! I finally got smart and made this little 4-legged table that just clears the rib tops. Now I have a work surface again, and I'm thinking about making one or two more.

The oversized ply faces are trimmed to the box rib caps with the laminate trimmer on the router table.

The box ribs are glued into place between the aileron spar web and the TE, using waxed paper beneath and aircraft nails to temporarily hold everything into place. Also in this photo are the 1/4" x 1/2" aileron web caps being glued into place. Clothespins provide ideal pressure here -- pony clamps might squeeze too much glue out with too much pressure. I had to trim a little wood off one surface of the clothespin jaws to achieve pressure directly where it was needed.

This cicada buzzed my shop and landed on my spar to see if I knew what I was doing. It seemed to be saying that my contraption would never get off the ground, but I'm quite sure that I'll be able to achieve flight that is much more controlled than this critter is capable of (although my plane will not be as nice to listen to!).

I just added up my hours so far, and found that I am 206 hours into the project.

As I was making this sanding fixture I was thinking "People are really gonna think I'm too anal-retentive over this one!" But once again, a little setup time saves a lot of overall time and accomplishes much more consistent work.

There are 26 aileron diagonals to fit in each of my wings, and one end needs a compound angle sanded onto it. After hand-fitting the first diagonal I thought to myself, "Self, these diagonals are gonna be a real pain in the butt. We'd better find a way to automate this a little or we might just have to go watch a movie instead."

So instead of running back and forth from the far side of my 17' table to the sander (probably 6-8 times per diagonal) and hand-fitting each one, I set up this simple fixture which finishes the ends at the correct angle in seconds. Above, the compound angle that mates with the TE is sanded as the workpiece is guided by two... well... guides...

...and here the other end has a simple angle sanded onto it. You guys with a sander that still has the adjustable work table can probably do the same thing by simply tilting the table to the correct angle and clamping a fence to it. But doing both ends in one setup might be tricky.

Here the first set of diagonals is glued and clamped into place with scraps of wood and the good ol' clothespins. Before the opposing diagonals can be installed we have to flip the wing over and add the 1/4" x 1/2" caps to the bottom edge of the aileron spar.

You know how happy I was to have finalized my choice of engines? It ain't over yet, I'm sorry to report. There should be more on that in the October edition.

 

 

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