Oct. 30th, 00
400 hours spent, 383 parts made so far...
More Bananas
I don't know why I alwas make bananas. I'm currently closing and opening various 'L'-extrusions (SNX-F14-08,-09 etc.). Opening means put a solid round bar inside the angle, then squeeze in the vise until the angle opens up. This works moderately well, except that the angle doesn't come out straight after this torture. The sketch below may show what I mean:
Question: is it allowed to file the angle straight (remove hatched section, deformation is shown exaggerated in picture for clarity)
Answer (thanks David, Tony): NO filing recommended.
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Perfect Fit, Oct. 28th, 00
it's always easier on the second try...
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Destructive Testing, Oct. 25th, 00
Today, just for fun I tried to flute the banana former #2. SURPRISE, only four small flutes straightened the flange perfectly. Soooo follow plan B and use this part? - I want to know for sure what effect these flutes have. So I started to bend the former by hand more and more... not much force was necessary to produce this result:
The part failed as expected at the fluting location.
But what's with the other, unfluted part? I have to know how much better straight flanges are. So I destroyed also the other #2 former, this time using much more force (also as expected).
The story is not finished here. I put the defective, fluted part on the edge of my worktable and tried to bend back to the initial shape. You won't believe it - the wrinkle almost completely disappeared!!!
Would someone fly with such an junk part? - definitely not me. Makes me shudder to think on a ground-loop situation when the plane becomes inverted and the turtledeck is almost the only protection to be squeezed to a pancake.
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Bananas, Oct. 24th, 00
This are right and left turtledeck formers #2
watch the outside bend/gap of the upper straight flanges! this is not good craftmanship. David Koelzer knew the reason: I overworked the flange. This overworking comes from hitting the flange even if the flange is already almost 90 deg. (forget exact 90 deg., this is impossible with Sonex'es forming tools). An idea for newbies: the forming tool could propably be improved by filing the edge to about 95 deg. With a little experimenting the exact 'springback' angle could be worked in the forming tool.
I considered now the alternatives what to do:
1. ignore the bend and proceed as usual
2. fix it by fluting/shrinking or whatever else
3. make completely new parts
the consequences for the upper decisions will be:
1: the Sonex will never get a beauty price :((
2: fluting is not good because I don't like the idea of reducing the stiffness (stiffest is straight flange, second is fluted flange, almost no stiffness is a notched flange). A shrinker - I dont have one, it's expensive and probably not available in Germany
3. so new game, new chance
This time I will make the straight flange at the bending brake first. After this I will bend the fluted flange traditionally using forming tool and hammer method. This drawback will cost me at least three to four days (but because I own more time than money I can live with that).
After this experience my suggestion for all beginners: use the bending brake wherever possible. Even the small flaprib-flanges can be bent with the brake. Wherever try to avoid hammering straight bends.
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All about Lightening Holes, Oct. 22nd, 00
The gussets and angles are complete so far. The wing and fuselage ribs i had already banged months ago, but the lightening holes are still to do, so I choose this for my weekend project.
beware of the fly-cutter
All the holes I made with a flycutter. If you use this tool, be careful this animal may ~bite~ you. The problem is when the sheet to be cut is not clampled flat on the drill-table then the flycutter may bind and if you hold the piece with your bare hands, blood may flow. So I developed a safe procedure: I used the flycutter to cut holes of about 10mm larger than the lightening holes into the rib forming tools. Then I used the forming tools to hold down the rib.
If this assembly is clamped properly to the drill-table then no bad things can happen. Before each cut I sprayed a bit WD-40 on the sheet. Drill-speed I set to 150rpm. This is slow enough to control the cutting easily.
square edges
If you use a V-shaped chisel then the hole will get no sqare edges. So I re-grinded my flycutter chisel.
I hope the picture above is self-explanatory.
The following picture shows the result of the weekend's work.
Deburring is next.
the weigh of holes?
The purpose of lightening holes is two-fold: weight reduction and increase in stiffnes (caused by the hole's flanges). After cutting all the holes I had this box full of cutouts:
All this holes make a weigh reduction of about 1700 grams.
the beauty of technics
I couldn't resist to take this picture
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QUIZ OF THE MONTH, Oct. 2nd, 00
...only for Sonex newbies, all old-farts stand back...
What is this?
(a) German hunting trophy (hunting season is on, guys)
(b) artist's expression of my daughter's favourite horse
(c) rudder drive horn
first winner earns a dull 3/23 cobalt drill bit (very rare collector's item;)
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... 300th part completed (Oct. 2nd, 2000)
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