The Problem

... was that the default B&C's pivot arm did interfere with the front baffle hookup brackets.

Interference!

That did actually make me pay attention to the very unusual old pivot arm.

Old one

Nice dogleg, isn't it?

Well, this bracket did not involve any bending, just needed to make the correct one to fit around all the other stuff there on the nose.

Hmm... so how do we do that? Well, first, we need...

The Template

This is not the real template, because (.. read on ;) ). It's the template for the Template.

Start with a piece of heavy paper

Cut around the alternator

All we need to do with this template is show the location of the hookup hole (top hole, the one that attaches the bracket to the motor); the location of the slot for the alternator to hook up to, and the general outline of the alternator

Alternator bolt location is being marked

Bolt imprints along the "pivot arc"

..and finally, some more "no go" zones to prevent interference with other brackets there:

Done!

Notice I also added some "imprints" of the B&C-supplied pivot arm in there, just in case I'd need them.

Okay. I'm lying to you. This template is not the one I used. It was done with the long belt that ended up not working out, so I had to redo the template (thanks God, just the template). The new one was done in the same manner as the one I described above.

Here it is:

The *actual* template used

Okay. So now, we know critical locations of things and where not to go - so, cue in...

Solidworks!

It's magic, I keep telling people.

So, we take our template, and scan it on a scanner, along with a little metal ruler to give us physical dimensions. Then, we go to Solidworks, start a sketch, and insert the scan as "sketch picture". Using the image of the ruler that was scanned in, we tell Solidworks what "one inch" on this picture is. Boom! The image is now dimensionally accurate.

Then, we start drawing around it.

Initial sketch

Above, I positioned the top hole, and the four 5/16" holes around bolt imprints. I then sketched a large circle and made it tangent to three out of four of those holes - it defines the "pivot arc". Then, offsetting it 5/16th gives me the other "side" of the slot; and offsetting it more gives me the "sides" of the bracket in the "pivot arc" area.

I also started sketching the "no go" lines around the top portion of the bracket.

More circles

More circles and lines are added, and off-set. They are not positioned or dimensioned - just made tangent to "no go" lines. You can almost see the outline of the pivot arm, yes? ;)

Now, we take this master sketch; and add arc elements with real lines that we care about.

The arm!

Tada! We got the Solidworks Part.

By the way. How do you "measure" the round over of the B&C arm? Radius gauge? Calipers? Hmmm.. Or...

Measuring with Solidworks

Nice, isn't it?

Next, we print the drawing of our new part; making sure our holes' centers are marked (we'll use that later to drill them)

Done!

And, we got ourselves the actual template!

Now, the final test (Many thanks to USPS for providing material for this test)

Spray glue and cardboard

I wish I could cut 1/8" steel with X-Acto...

The mockup

Tadaa!!

Okay, we have the real template now, and we know it'll work. And now, comes...

The Grind

1/8" steel is no joke

Nice little sheet of 1/8" 4130 showed up from Spruce some time earlier... I used spray glue to put the print out of the bracket on top of it.

Template on steel

First, all the holes had to be drilled. The drill press I have at the moment is severely underpowered, so I had to step-drill them in four steps.

Curlies!

I got to admit, I am starting to become very fond of pretty steel curlies made by nice drill bits.

Also, lesson number one learned: drilling oil (I used TapMagic) gets under the template, and messes up the glue (and unglues it). I need to figure out a better glue.

I drilled the slot's "start" and "end" holes slightly undersized, and reamed the main attachment hole to 5/16ths exactly.

Reamer!

Next, the slot... I rough-drilled small holes around it's perimeter, thinking that a 1/8" shank carbide burr in an air die grinder (basically, Dremel) would work... Ha! It did... for a second ;)

Slot in the making

Boo!

Okay, time to go old school... where's that...

Hacksaw!

I cut it out, and cleaned it out with a bastard file.

Cut out

.. and cleaned up

And then, more and more hacksaw...

.. my right arm

.. is beginning to feel...

.. it ..

Yeah. The last few inches, I gave up, and used the jig saw. It did cost me 3 blades, but I was too ... done with the hacksaw. I figure, about a blade per 1 inch of cut in 1/8" 4130 with a jigsaw...

.. gave up.

Cutting done.

Looks very ugly, right? Well.... to the grinder!

Grind...

.. grind ..

.. grind away ..

Three belts I believe is what it took.

Well, now, the final cleanup on the slot. Yes, Dima, I used the rotary file here :).

Cleaning up the slot

..and, test fit

Tadaa!

That was two evenings, folks; but I wasn't done.

The Three Brackets

Next, I had to prep the edges and sand out all the scratches, and paint. A deburring wheel on a bench grinder helped; and the most nasty marks were filed out and then polished out with the deburring wheel.

Clean edge

It has to be done because every scratch is a stress riser - on fittings, every edge needs to be rounded over, and polished.

Finally, to....

Paint

Every airplane "paintjob" I've done so far was in my makeshift "paintboots". Like this one.

Paintbooth!

I sprayed both the pivot arm, and the baffle support bracket I made earlier, with self-etching primer, and some Rustoleum paint. White will make cracks more visible, if they show up.

Painted!

So there we go. With this done, I can now install the alternator. Just measly 30 hours to get ready to install the damn alternator! ;)

Drag Wires: done.

Finished all the drag wires. Initially I did an incorrect layout from the standpoint of which wire passes over which (or under which, depends on how you look at it). Apparently, I came across a definition of drag/anti-drag that's exactly the opposite of how the plans define them... Sigh.

Wires have to cross inside the drag wire blocks and inside the spar; so one has to go over and one under, like this (lots of transparency here):

Drag/Anti Drag Wires Crossing

That's the pattern I did wrong; causing some interference with the bellcrank and heavy interference with rib diagonals.

Thanks to my original post on drag wire blocks interference in the aileron bay, and the picture Ward posted in that thread, I figured the wires pattern out. Switching it around made for much better clearance!

Also, my original problem with aileron interfering with the drag wire blocks is apparently no problem at all - I'll just relieve them (rasp, file, sandpaper, whatever) to provide clearance.

So, here's what the wing looks like right now:

Latest wing with all the drag wires

Aileron Bay and Drag Wires

... and then, something I spent quite a number of hours on. You see, I want to sheet the inside of the aileron bay with curved piece of 1/16th plywood, supported on braces joining ends of the ribs together.

A few pictures below show the idea:

Aileron Bay Sheeting. Grain orientation is off, I know :)

This shows the support brace between ribs, just one for now.

Aileron Bay Sheeting, showing the support brace.

This is all very rough. The problem though was this.

Here's how it looks from the wing tip side:

Aileron Well, looking from the tip, zoomed out

Aileron Well, zoomed in.

See that clearance??? 7/64ths between the aileron tip and the nut! So even before I started figuring out the best spline curve for that sheeting, it was obvious that it won't clear... 1/16th ply + 1/16th gap is already a 1/8th, or 8/64ths!

Asked the Biplane Forum folk in the same thread... And, separately, actually figured it out - it was suggested to use two thin jam nuts there instead of a thin + regular nyloc.

That cleared a lot of space up!

Finally, some clearance!

I was thinking about modifying the tails of the wing ribs in the bay area to support this sheeting.. But, even with thin jam nuts, the bay is still very tight. Given that I won't be able to build exactly to perfect dimensions, I finally decided not to bother, and just build in place (and then we'll see what clearance I really will be able to get :)

Backup plan? Have some drag wire hardware protrude into the bay, and sheeting be not "in front of it", but somewhat behind it (closer to the main wing spar). Something like this.

And with that, I moved on to

Cleaning a lot of things up

Added all the hardware to the aileron hinges. Cleaned up most of the compression plates (doublers) to go around the compression struts and drag wires.

Oh, and apparently, my aileron hinges were drawn a bit wrong (and had that unsightly early model of Fafnir rod end I have thrown together). Fixed that. Made them pretty green color to celebrate the occasion :).

All pretty and correct hinges with HW

Compression plates relieved for the struts and drag wires

Interference

As I expected. Drag wires don't clear rib's diagonals in some places.

Station 24 vertical and diagonal interference.

Hale Wallace in his notes suggested to relocate station 24 vertical to 23 3/4, 1/4 inch forward (or "left" in the above picture). This will make the diagonal more steep, and clear the drag wires. I'll have to do that.

Another nasty. I was ready for this, and, sure enough, the bellcrank/idler pushrod doesn't clear the compression struts. The idler will have to be made lower; Steen bends them downward and I will see if I can avoid that by just moving it down a bit (and moving the idler arm down on it's bushing).

Pushrod not clearing compression struts.

Ribs

So, I started looking at relocating that vertical first.

My ribs' models are the first ones I did in Solid Works; and they suck. They are made off of sketches created from converted AutoCAD files, with lots of ugly things in them. They are practically unmodifiable. Back then I thought it was easier to draw things in AutoCAD and import them to SWX - oh, what an idiot I was :).

Also, while looking at things, it became clear that they also are not sitting right on spars (not symmetrical to spars' center plane basically).

It feels like I will end up re-drawing them from scratch, and doing them as proper assemblies this time. We'll see.

It might well be that the problem I was having with aileron-to-other-ribs-alignment will go away, and no holes will need to be relocated...

It's annoying, but at this time I am so much better with SWX than back a year ago when I was doing ribs. Still, Le Sigh.

Aileron Tip Rib, Wing Tip Rib, and Tip Bow

I've been putting this off, since those tip ribs are not dimensioned on the plans, and aren't a standard airfoil. They're supposed to create a nice transition from the main wing panel into the tip bow, creating some nice curvature.

I had the wing tip rib drawn up approximately, just as a placeholder.

Yesterday, I did an approximate aileron tip rib as well. Cutting it out of the plan and super-imposing two patters on one another helped! Plans are off (dimensions marked on them are not matching the dimensions measured off of them), but at least they're off uniformly within one sheet; allowing me to do this. It shows what's where.

Tip Rib, cut out - finally, some physical work on the "plane"!

Well, for one, it became obvious that the top aileron skin on the leading edge will have to create a compound curve going to the tip rib.

Searching thru the Forum, and reading things showed that apparently it's not that big of a problem. Gradual gluing and lots of clamping pressure should solve that one. :)

And then, there's the overall tip rib shape.

Overall setup.

This is all very early with no "trimming cuts" made, obviously.

If you think about it, the aileron tip rib is supposed to be a bit "beefier" ("taller") than the wing tip rib. The tail of the aileron tip rib in the place where it's touching the bow should be 3/4 inches tall (so that it's flush with the bow).

All that will create nice smooth "flow" of curves from the last "full size" airfoil section (created by the wing rib and the aileron rib) into the tip ribs and tip bow.

So, first thing I'm not sure about is how good my tip rib (wing rib that is) is. I think the aileron tip rib should "play off" the wing tip rib's shape... In fact, if you lay a straightedge between the tip rib and the aileron rib with aileron positioned at 0 degree deflection, moving that straightedge should define the form of the aileron tip rib. I will do just that, later, lofting the surface that will "cut" the aileron tip rib out (and use a real straightedge with some sandpaper glued to it to shape the actual aileron's tip rib). I love it how CADing makes you think about these things!

But! That requires me to have a nice wing tip rib. Which I don't have. So to that task then, first.

Skybolt plans have the general outline and no grid on them. It's not a standard airfoil. Hmmm...

Last time I did it, I took dimensions off of plans. It turned out a bit off shape-wise if compared visually to the plans, so I tweaked it a bit. I still don't like that tip rib.

To the Firebolt!

Firebolt, by the way, is Skybolt, "improved" (and by that I mean added weight). Fuselage is a few inches longer, and hardware is all different; but basic wing design and overall things are the same. It makes it a great reference to read thru and see how things are done there.

Firebolt's wing tip rib is located at the same station as Skybolt's. That gives me some hope :).

Firebolt plans are also off (print dimensions not matching actual on sheets), but at least they have the grid -- amount of error accumulated over 1 inch of measurment hopefully is negligible. We'll have to see.

Dimensioning the Firebolt plans

And after going thru about half of that dimensioning, I decided that it's actually time to write this B-Log post, and take a break :).

I'll be bending some more sheet metal tomorrow. Post on that coming up!

Incidence and Fittings: Finishing Up

First, the incidence. Last time, I was trying to figure out how to deal with vertical fittings having to align with spars angled at 1.5 degrees up (incidence). A good discussion on the Forum ensued, and I figured (aside from me having to buy a +/- .0001 Precision Axe), to drill the hole at 1.5 degree angle in the front fitting, and forget about the little gap that shows up there, and weld the rear fitting in place. So something like this (you're looking at the fitting pair from the side, the CL is the hole centerline).

A pair of fittings, with the hole drilled at an angle

Gap that shows up when fittings are vertical, and hole is at an angle.

Note to self: When building / finish welding, I might reconsider and bend the tops of that fitting 1.5 degrees back to make everything flush. I probably will.

Back to the Control System

Next item on the list was bellcrank-to-aileron pushrod, which is tricky. See, if it's straight, it doesn't clear all the hardware.

Pushrod is not clearing hardware if straight

So it had to be slightly bent to make the bellcrank side rod-end a bit more "horizontal", if you will, while not "horizontal" enough to hit the spar above.

This sounds easy; and probably is -- but tweaking splines, checking, re-checking and tweaking again while checking for full range of aileron's motion took up most of the time here.. I think I spent a good 10 hours or so just tweaking that one pushrod... And finally, here it is -- notice a slight bend in it. Just a touch less bend and it hits the washer under the bellcrank side rod end, just a touch more, and it gets dangerously close to the spar.

Aileron pushrod, tweaked to fit

Finally, I was able to move the aileron linkage on the wing model and check the idler - bellcrank pushrod for ribs' verticals clearance. It clears! There's another clearance issue though - by the looks of it, it won't clear the compression struts (3/4 x 3/4 inch struts go in the middle of the ribs, forming wing bays along with drag/anti-drag wires) by the looks of it. So struts and wires it is, next, amongst other things..

Control system looking from the wing butt: won't clear the compression struts

Fitting Wings To the Fuse

For some reason, Solid Works gods decided to start hating me here. Remember the note about angled hole in the front wing fittings pair? Assuming that pair is mated to the fuse (lower longeron); front spar butt hole (ha.. ha ha.. haha..) mated to that angled hole in the fittings' pair should produce correct incidence; and dihedral can be set with wing spar centerline mated to, say, one of the fuselage's crossmember's centerlines, at required 1 degree angle? Ha! Yes; that worked -- but for some reason, would cause all kinds of shenanigans the moment I would make the SWX assembly flexible (== allowing me to move control surfaces of the wing sub-assembly as a part of the overall assembly).

Yeah-right. -3 hours of my life until I gave up.

Instead, I made a virtual "jig" -- another sub-assembly containing planes at correct dihedral and incidence angles. Wing's "Top" plane would mate to the "wing" plane of the "jig"; latter ("wing" plane) would be at 1.5 degree incidence / 1 degree dihedral. That worked.

The virtual "jig" made of planes.

Dihedral of the lower right wing

That same "jig" assembly contains fittings mated to the wing spar -- and then, that "jig" subassembly is mated to the fuse via fittings - to - longerons mates.

That, for whatever reason, worked. After that, 10 more minutes of making one final pushrod connecting idler to Actuator Arm on the Torque Tube, and..

Control system all hooked up and working!

Happy me, making virtual airplane noises moving virtual torque tube moving virtual control system actuating virtual ailerons... Who says CAD isn't fun? :)

Now, back to those compression struts, only to find out that the pushrod does NOT clear... Le sigh.