When I test fit the elevator ribs, I found then much to tight. This is always a problem hammering over a formblock. The radius of the formed metal is always a bit larger than the formblock radius thus if you make it to the plans, the resulting part will become a bit too large.
Another disadvantage of the flange hammering mathod is that you always get a slight banana shape (because the hammering stretches the metal).
My latest procedure is this:
I use now both, formblock and bending press. The press alone cannot be used, because the two 90deg bends are too close together.
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Sonex Parts Arrived (all I had bought previously were the plans and formblocks), Apr. 28th, 2001
Some weeks ago I ordered some material from Sonex. Main reason is that there is no local firm that can bend the tirangular envelopes of the control surfaces. Constructing a own press is too much trouble. furthermore I ordered sparcaps, the rudder horn and the tailwheel mount.
Here's a short report about my impressions of the parts:
The large cardboard box of the control surfaces was demaged at several places (several holes the size of about 1" x 2"). I think that the ship loaders have hit hooks into the box to carry it around, even that Sonex had 'Fragile' labels pasted all around. However this was not a problem, because the parts were nicely padded with cardboard inserts and paper strips and survived the abuse.
At my first glance at the flap skin I almost got a heart attack of all the scratches. But at a second closer look these scratches were on the vinyl covering. The sheet metal was O.K. except one scratch at one flap skin over the whole width. This can probably be polished out.
The sparcaps were not so nice. I was one of the last customers who could get the raw material. Sonex now sells ready machined sparcaps (for double the price). So I probably got leftovers which looked as if they were kicked around on the concrete floor.
Precision
I'll start with the evelators. When I measured the overall length I read 939.0 mm. The plans say 939.8mm. So the part is 0.8 mm too short. That's way over my personal precision limits - not so nice (Iwould have appreciated it a little larger).
Since 20 years I didn't touch a welding torch, so I also ordered some welded steel parts. The weld beads are good workmanship. The parts are black powder coated (I would prefer white: easier to find cracks and easier to paint in another colour). The pieces are welded together as they came from the cutting brake (or laser cutter). Edges are not rounded. Maybe I will rework this parts a bit and then repaint them.
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Instrument Panel, Part II, Apr. 16th, 2001
If you like a flat, smooth panel like this (stainless steel)...
... then you have to dimple and flush-rivet the panel to the cross-tie. BUT if you already have made this...
...(cross tie, F07-05) then you got a problem now...
... this dimple die won't fit into the 60 deg corner ( I only use 'real' dimple dies). That means scrapping another good part and start all over again.
The cross-tie sheet has to be pilot-drilled, drilled and dimpled BEFORE the 120 deg. bend is made. Additional effort for the second instrument panel so far: 20 hours.
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Alumiprepping & Alodining Apr. 11th, 2001
Today I purchased two one meter long roof drain??? (don't know the English word for this). Also four end-pieces with rubber seal inserts. This makes very good chemical baths.
The watery substance is Alumiprep(R) 33 from Parker Alchem (a Henkel Corp.), Madison Heights, MI 48071. It's quite a strong acid which will be diluted with water in a ratio of 1:4. You can see gas-foam developing at the alumn surface. Even that the label claims to remove dirt and contamination I will intensively scrub all parts before starting this treatement.
After rinsing, the part will be alodined (Alodine(R) 1201 from Henkel Surface Technologies). I use the Alodine type which makes this nice golden coat (there's also a transparant version).
This coating process will not add any significant weight.
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What I learned about Corrosion -the hard way-. Apr. 10th, 2001
Springtine is coming, outside temperature rises to comfortable levels - so it's time to prime the aluminum parts. But before this the parts have to be cleaned thoroughly. Michel Colomban (the famous designer of the MC 15 Cri-Cri) recommends using household scrubbing powder. So I started the black art.
This is a very dirty job. At first I worked without rubber gloves. Afterwards it was almost impossible to get the finger clean again. The next problem was that it would take several days (weeks?) to clean all parts. But when I would have finished the last part, the first one may already have been oxidyzed again. So I developed the genial (which turned out later stupiud) idea to store the cleaned parts ~under water~. The idea behind this was that the water would prevent the air's oxigen to corrode the metal.
The third day I took a part off the water which I made the first day. -SHOCKING- this part and all the other three day old ones showed the typical aluminium corrosion marks!
So guys, this is the true story about the famous 6061-T6 corrosion reststance! Lemme say that this is not the cheap stuff from the scrapyard, but high-quality QQA-250 aircraft-grade material!
My explanation so far is that the bare sheet with its shiny surface really shows some kind of corrosion resistance (also the high-gloss polished surfaces will). BUT once you start to sand the surface (for example when using Scrotch Brite pads or the like) then all the resistance is gone (and honestly who of us has not removed small scratches that way?)
I removed the alum-oxide spots as good as possible. But small discolorations are still visible. Then I alumi-prepped and alodined the first parts.
Initially I intended to prime directly the cleaned bare aluminum. But now after I have learned my lesson it looks as if I will apply this cure to all parts (except the outside skins which will be polished and waxed). The alodyne should be sufficient to protect the metal before the epoxy-primer will be applied.
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New Instrument Panel. Apr. 9th, 2001
The decision is made! I'll build a completely new instrument panel. These are the modifications/deviations from the original:
- No central rectangular cutout. This weakens the panel too much.
- Built-in recessed inserts to clear cross tie.
- Panel will be mounted all around using round headed phillips screws and self-locking nutplates. This will ease servicing a lot.
- Instead of riveting the lower front to the cross tie I'll make another lower horizontal bend and mout the panel from the ~bottom~ to the cross tie. This way there will be no visible rivets heads at the panel's front (see sketch below)
- Bolt (instead of rivet) the panel/crosstie assembly to the left and right corner plates in order to make the whole panel-cross-tie assembly removable
- Install glareshield ontop of forward longerons (instead below as the plans show) This will provide another 1/4" clearance for the fuel tank (several builders struggeled with a too tight tank fit)
- And finally: I ran short of 0.032" sheet alumn, BUT I have still left over about one square meter of STAINLESS STEEL from the firewall construction. THIS will become my second instrument panel. (remember Lindbergh's Spirit of St. Louis's polishing pattern? That's the way my panel will look like - just Grrrreat!
Sketch of new instrument panel (side view)
The panel will receive a small center subpanel and two small brackets right and left accepting the headset jacks.
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More about Switches and Fuses. Apr. 8th, 2001
My switch/fuse setup was quite nice (for the eye), BUT this @&$%§ Instrument Panel Cross Tie was in the way. A big disadvantage of the 60 deg. slanted instrument board is that you have very limited space behind, particularily if you mount something at the lower half of the board.
After some more thinking and headscratching the following solution came out:
It's a piece of 0.032 with three horizontal bends. This thing gives restores a decent 90 deg mounting angle.
The assembly weights about 350 grams, so you weight concious per-the-plans builders forget everything you saw here ;)))
Side view. The three horizontal bends can be all made with a simple bench-mount brake, the triangles right and left I hammered over a form block.
P.S.
If I would have to do the panel again, I would build a rounded panel/glareshield. This would limit the forward view a little bit , but I would trade this inconvenience in for some more panel space.
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Switches and Fuses. Apr. 6th, 2001
From time to time I have to take a break from metal bashing. So I fiddeled a bit around with the instrument panel.
At the far left Strobe, Avionics and spare switches, dual ignition switches (guarded), battery & alternator switch (guarded). Above the starter switch, at the right side resettable circuit breakers and a power outlet socket.
Switches are heavy-duty 15A types with silder-plated contacts. Microswitches would also have done the job, but my switches got such a nice 'click-feeling'.
Circuit breakers are 5 and 10A Potter & Brumfield, also good stuff. What I wouldn't recommend is cheap stuff from the automotive corner-shop (at least not for the 'mission-critical' circuits).
This is the main buss. Maybe I'll do later galvanic silver plating the copper bus bar.
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Current Status of Apr. 5th, 2001
I'm still working at the tailcone. Have rounded all 90-deg edges at all those sheet metal parts. Waiting for higher outside temperatures for priming.
