Rudder Rib and Brace Assembly

 

The aluminum rudder frame has been acetone-cleaned, 80 grit sanded and re-cleaned in preparation for Aeropoxy attachment of ribs and braces. Clear shipping tape was used on the table to prevent sticking, though I've read that two coats of paste wax on the melamine surface will yield the same effect.

Dry fit prior to cleaning

The foam is easily sanded by wrapping sandpaper around a tube to create the groove needed to mate with the rudder torque tube and trailing edge tube.

Making Multiple Parts

To increase efficiency (and decrease boredom), some changes are needed when making lots of copies of the same part. In this example, the Strut Fixture (reference B4W5) requires thirty-four copies.

The normal procedure for one or two-off parts is to individually measure and mark each part, center-punch all holes, manually set the x/y coordinates on the drill press table once the part has been clamped in the vise and drill. Follow that by grinding, hole deburring, hand-filing and hand polishing with a ScotchBrite pad. However, that all gets a bit tedious after the first five, twenty or more parts.

My solution involved setting up a simple backstop guide on a wooden table that I clamped into my drill press vise. A chunk of walnut and oak that were laying around were clamped in place and a toggle clamp screwed down to hold the work in place.

With the 6061 aluminum being a relatively soft metal, the lack of a center-punched hole did not prove to be a problem. It doesn't hurt either that the designer allows for a generous 1/16" tolerance. Also, close examination of drilled holes shows a slightly triangular shape - evidence of a drill chuck taper/quill runout problem that I need to fix some day. Anyway, this method made pretty quick work of the drilling of the 104 holes (left)

The next step required making a 3/8" radius on the four corners. I started by clipping off a small amount of each corner with the band saw (one part in each hand, alternating and flipping), then grinding a smooth curve on the grinder.




















I forget to mention, I used a small flat file after the hole drilling operation to knock off any burrs, allowing the part to sit flat on the grinder table.

The next step was to hand-file the burr created by the radius grinding, knock off the burr around the radius and smooth the grind marks a bit.

The final smoothing and polishing was carried out on the drill press using a ScotchBrite aluminum oxide wheel at about 1,500 rpm.

There, 34 pieces. Almost time to go over the pre-flight checklist.

Parts Fabrication - Tail and Wing

That virus that's going around has slowed things down a tad - that and helping my wife survive after she shattered her right arm/elbow in a fall. When I'm not making meals, doing laundry, cleaning, dressing or bathing my wife, doing the finances or working my regular job, I'm darn sure working on the Bloop!

The primary focus the past two months has been small part fabrication for the tail and wing:

Rudder Styrofoam

One inch wide strips of Dow Styrofoam are required for the rudder. There are many ways to cut it (e.g., hot wire, various saws and knives), but I chose the easiest considering what I had on hand: a thin, break-away blade cutter. This method produced no mess and avoided a potential ventilation issue, too.

I found the best method was to be patient and start with the blade extended out only about 1/2", taking three or four increasingly deep cuts till I reached the underlying cardboard protecting my work surface. The final cuts required the extended blade to be less supported by its handle, so slowing down prevented chip-outs and errant cuts.

1" Thick Foam, Drywall Square and Cutter.

Foam Strips Ready for Final Sizing

With some small foam scraps, I experimented with filing and sanding to get the contour for the 1" Rudder Tube. After some trial and error, the best approach was to cut a small 'V' on the end of the foam then use some 80-100 grit garnet paper wrapper around a piece of scrap 1" tubing to get to the desired final shape.

Note: the two 24" x 48" tables above had to be leveled to fit together for a suitably long work surface. My basement and garage floors are very uneven. I found a YouTube video that had a variation on what I ended up doing. I used an old (as in early 1990's-old) 2" x 10" waterbed frame board to cut out 7" diameter circles. Next I attached them to the table legs with 3/8" x 3" long hex head bolts and tee nuts. I offset the hole in the 'wheel,' about 2" off the outer circumference,  to provide an eccentric movement, giving me lots of room to play with for leveling:

Rudder Frame Taking Shape

Taped a multi-drawing, 1-to-1 scale paper template to the tabletop again for the bottom trailing edge rudder tube bending (removed in picture below). Next, took advantage of the square, flat, straight-edged table top to align the two trailing edge tubes. This allowed me to cut the lower half of the trailing edge tube to final length for the rear edge splice (just to the right of the B4T1 drawing), and measure the angled cut where the tube joins the bottom of the torque tube.

...need a bigger table?

Rudder Tube Bending

After some small bit of trepidation, I determined to do something I have little experience with; tube bending. I started by making a 1-to-1 scale model in SketchUp (imported the Sandlin plan drawing, B4T1, then scaled it) and printing it out on multiple sheets. Masking tape held the sheets in place to act as a bending guide. Next, two scraps of wood, drywall screwed to the sacrificial table surface, acted as the bender:

Trial and error...

The top half of the rudder trailing edge tube.

Now, more printouts for the bottom part of the rudder trailing edge tube and repeat the process. Finally, I'll be joining the two somewhere in the vertical section.

Tail Time

My original plan, after completing the nose, was to build the lower center wing section. However, I was unable to find the spar tube (1.75 x .035) in stock at Aircraft Spruce, and available, but pricey at TW Metals ($388 for two 96" long tubes, about $13.00 for shipping). That's about $2,500 for the wing spar tubes alone. I was unable to find those dimensions in 6061-T6 aluminum tubing anywhere else on line. (Update: don't tell anyone, but Wick's has this tubing for $6.15/ft. An 11-hour road trip and I can save the shipping cost, too).

So, instead I began on the tail. I started with a few parts seen in the pics below. Since the shipping cost for anything over seven feet skyrocketed about eight months ago (at least for UPS), I bought shorter lengths and will connect them with an internal splice.

Temporary nuts.

Internal splice for trailing edge tube.

I was thinking of using an external sleeve on the trailing edge, but I saw what looked like an internal splice on one of Mike Sandlin's photo gallery pictures:

Splice?

My method was to cut a two inch piece of 3/8" tubing, put it in a vise and cut lengthwise on one side. I then tightened the vise to close the gap and repeated six to eight more times. I filed and rounded the piece to get the result in the picture. I plan to place two rivets about 1/2" apart on each side of the cut - facing inward.

I was able to find a very good price for pultruded (epoxy impregnated) carbon rods, 1.5mm x 1000m at a place called https://www.racedayquads.com. I'm hoping the very slightly smaller diameter is aceptable as the plans call out .063"