Built in scale for the Polish rubber stripper - RC Groups
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Feb 04, 2013, 12:45 PM
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slebetman's Avatar

Built in scale for the Polish rubber stripper

So, I got myself a rubber stripper. It's the Ciapala stripper - also known as the Polish rubber stripper. The Polish stripper has a very nice design feature of being able to set the width of the rubber and the thickness of the cut separately. After some thinking I figured out how to install a scale so that I can accurately set the stripper to cut various thickness of rubber without trial and error guesswork.

The key to the whole thing is finding the center of the blade. Took me a while but I figured out a fairly simple way to do it.

So, the first step is to actually make an accurate small scale ruler. I drew a 1 inch square box and positioned it exactly 1 inch form the edge of the page in the drawing program. This allows me to then position all the other lines accurately. Attached below is a PDF file of a small ruler in 0.01 inch increments. Since the black lines and the white space between them are roughly the same thickness you can use the white areas to measure 0.005 inches. In this way you can set up your stripper to cut anywhere form .010 (if your stripper is up to it) all the way to .320 in 0.005 increments.

The first step, before doing anything else is to verify that the printed ruler is correct. I happen to have a steel ruler with .020 ticks. So I compared the printed ruler against that.
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Feb 04, 2013, 12:52 PM
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slebetman's Avatar
Next is to install the ruler on to the stripper. I eyeballed the cutting blades through the guide hole to figure out the approximate center and installed the ruler to the left of the center. The reason for that is so that we can install a cursor tick mark above it. Otherwise, if the ruler is installed with it's zero exactly at the blade center, you'd have to use the edge of the plastic guide as the cursor. But on my stripper, the guide holes didn't have good, definite edges. So a separate cursor was needed.

I simply used double sided tape to stick the ruler on. Align the ruler carefully so that the top is flush with the top of the metal bracket holding the plastic guides.

BTW, all through this procedure I used my phone camera as a magnifying glass. Didn't have anything on hand that was as powerful. I did have to tape my phone to some bits of wood to hold it in place. Couldn't get my hands steady enough to get clear images at this level of magnification.
Feb 04, 2013, 01:03 PM
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slebetman's Avatar
Next we find the center. The trick is fairly simple. Just cut a piece of rubber. Don't need to set it to an accurate size, just cut it. We'll be using it to measure where to install the cursor.

The measured rubber is actually the one that comes out on the left of the stripper. The bit of rubber on the right is the leftover.

Once you have a sample cut it's time to measure it. Measure it at several different places several times to find the actual size of the cut. You can either average the result of your measurement or simply take the majority if an obvious majority emerges form the measurements.

I don't have a caliper so I use a copy of the printed ruler to measure.
Feb 04, 2013, 01:08 PM
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Now that you know the size of the sample cut, install the cursor above the ruler to indicate the measured size. In this case, .065. Which means the cursor should be on the white line instead of the black.

Again, I simply used double sided tape. But delrin is non-stick. So the tape has just enough tack to stay in place and nothing more. Which means that once you've adjusted the position of the cursor DON'T TOUCH IT EVER AGAIN.
Feb 04, 2013, 01:12 PM
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slebetman's Avatar
So, it's basically done. One last thing to do is to confirm that the thing works as advertised. So strip some rubber and confirm that the cut size is correct. I made two cuts for the test: .010 just to see if the stripper can do it, and .020

The result was good. Both were fairly accurate when measured against the spare printed rulers. At least it's good enough for sport flying.
Feb 04, 2013, 01:46 PM
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Jimmy JFlyer's Avatar
Very cool stuff. I must say, I have learned a lot in the last week about FF since your Portable Plane afflicted me with this addiction.
I wonder if the LHS will have rubber at the size I'll need.
I certainly can't get a stripper atm.
Feb 06, 2013, 05:25 AM
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Yak 52's Avatar
Nice work Slebetman!

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