Author: "gsuit_2000" <gsuit@...> Time: Thu Oct 17, 2002 7:59 am PDT Link
Ok. I've read and re-read Section 5B in the RV7/7A Construction
Manual where it discusses Edge Finishing, Hole Deburring, and
Scratch Removal. And I know that everything must be smooth so
that "you can't feel any roughness and there is no chance of drawing
blood."
My question is, how smooth is that?! Really? For instance, I just
radiused and 'smoothed' the edges of the Emp Rear Spar stiffners.
It seems that I'm smoothing so much that I'm rounding the edges
quite a bit. And again on the Emp HS stiffners that come as stock
square pieces of angle (the ones you bend to 6 degrees).
I can understand the importance of smooth edges to avoid stress
concentration points, but I don't want to waste time or more
importantly, "over smooth" any parts and make them structurally
weak. At the SportAir Workshop I attended, we did radius a stiffner
or two, but there was no checking or emphasis on this topic by the
instructors, so I have no idea if I did it right. I just need an
eyeball calibration on this, and then I'll be good.
Thanks for hearing me out,
Clayton
Author: "Dennis O'Connor" <doconnor@...> Time: Thu Oct 17, 2002 10:06 am PDT Link
If the stock is less than .032 just knock the edges over with the deburring tool, or a bastard file (my method), and give it a few polishing swipes with Scotchbrite... If your skin doesn't catch or tear when you run your thumb across it, it's fine...
If the stock is thicker, like the HS609, then use a file to put a 1/32 radius on the edges, and then polish the the flats and the radiused edges until nothing catches on your fingernail... A mirror finish is not required...
Of course, on the 609 the corner that lays down against the inside radius of the 603 requires a more generous radius of ~1/16 to 1/8, so you will see shavings on the bench... I use a bastard file to whack it down to a rough radius shape, then use scotchbrite metal polishing pad (Lowes paint department) to smooth the file marks and leave a relatively rounded edge...
The guideline is that if you slide a finger down the edge of the sheet/part and you can feel little burrs grabbbing your skin, it's too rough... So, knock down any points or projections, and take any V scratches and turn them into a U... But, don't take a sixteenth of metal off the entire side of a part trying for a mirror...
After a while sheer fatigue will bring you to the same level of finish that we all do....
Denny
----- Original Message -----
From: gsuit_2000
To: RV7and7A@yahoogroups.com
Sent: Thursday, October 17, 2002 10:11 AM
Subject: [RV7Yahoo] Edge Smoothing Question
Ok. I've read and re-read Section 5B in the RV7/7A Construction
Manual where it discusses Edge Finishing, Hole Deburring, and
Scratch Removal. And I know that everything must be smooth so
that "you can't feel any roughness and there is no chance of drawing
blood."
My question is, how smooth is that?! Really? For instance, I just
radiused and 'smoothed' the edges of the Emp Rear Spar stiffners.
It seems that I'm smoothing so much that I'm rounding the edges
quite a bit. And again on the Emp HS stiffners that come as stock
square pieces of angle (the ones you bend to 6 degrees).
I can understand the importance of smooth edges to avoid stress
concentration points, but I don't want to waste time or more
importantly, "over smooth" any parts and make them structurally
weak. At the SportAir Workshop I attended, we did radius a stiffner
or two, but there was no checking or emphasis on this topic by the
instructors, so I have no idea if I did it right. I just need an
eyeball calibration on this, and then I'll be good.
Thanks for hearing me out,
Clayton
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Author: Jim Duckett <rivetsqeezer@...> Time: Thu Oct 24, 2002 5:31 pm PDT Link
Clayton,
The easiest way I've found is to use the "rule of thumb" you use when breaking (bending) material... Minimum Radius 1 1/2 times thickness. The same holds true of edges. We try to stay with Maximum Radius = 1/4 thickness per side unless other call outs are specified. Like was stated in other replies, If it feels good to you...it probably is!
Two really good guides are AC 43.13 and the Standard Aircraft Workers' Manual.
Jim DuckettYahoo! Groups SponsorADVERTISEMENT
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