Coopering warm-up

I've got a project to repair an item for an uncle to, essentially, replace a missing panel in a barrel. As a warm up for that I decided to make a pentagon shaped structure.
The angles came out close, but it does not fit well and I'm trying to look for clues.
The test material was a strip of plywood about 30 inches long and 40 inches wide.
I set the angle of the table to be 36 deg off of center and ran both side of the strip through. I then ripped the strip into similar length pieces.
Using my digital angle gauge, the angle of the beveled edges ranges from 53.6 to 54.4 degrees. When I put pieces together, there's always one piece that does not fit.
The third attempt worked better than the second, with some slight tweaking of the angles. (The first was a complete mathematical mistake.) Are there any suggestions for improving this process?
The barrel pieces will be done in mahogany when I feel confident in being able to do this work without ruining the wood. Although I'll probably move up to poplar, or something similar, as a final dry run.
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Scott Zrubek wrote:

Don't you mean 18 degrees?
I don't know if this will help, but it's something I do when I make stave drum shells.
Let's say I need 10 pieces for a 6 inch deep shell. I don't cut 10 pieces, 6" long, then run the bevel on each piece. I run the bevel on a 5' long piece, then cut it into 6" pieces.
I apologize if this sounds like I'm talking down to you, but you'd be surprised at how easy it is to not get that.
I also don't leave the final cut to the saw. I rough cut the angle and get the final bevel on a router table or jointer. And you'd be surprised at how much help stationary sander can be at getting that *last* piece to fit just perfectly. But in all honesty, I've only had to use a sander the first time.
You can cut very small pieces just for testing to see if you have the perfect angle set on your tool.
I hope some of that might help you with your particular challenge.
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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-MIKE- wrote:

I've never had that luxury on the drums I've made; I had precious little material at my disposal and I had to eek out the pieces from all different sections of a rough board in order to get enough to do a drum. Once the rip width and blade angle on the table saw were set correctly I've been able to rip 20 short little boards with good enough consistency to get it wrapped into a perfect circle. Of course, it helps that I have a very nice and accurately tuned Delta Unisaw that could rip down the length of an RCH (if only I could figure out how to get it to hold still while I was pushing it past the blade...)

Sounds like a lot of trouble.

Which, depending on the application, may be all you really need to do. If you're fitting 10 pieces into a circle, is anybody really going to notice if you make 9 consistent pieces, then custom cut the 10th to fit the remaining opening? I wouldn't want to do that on a snare drum, but for other applications it may not matter. However, it sounds like the OP only has to replace one stave in an existing barrel, so I'm not sure why there is a need for a level of accuracy that doesn't map onto the problem at hand.
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Steve Turner wrote:

I don't have a Delta Unisaw. :-)
Nor did I have the great blade I now have, last time I did a shell.
--

-MIKE-

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I only have to replace one stave, but that stave will have to be multiple pieces glued up and rounded off so I'm working on general knowledge and then tailoring it for my task.
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I tried it with 18 degrees on the first attempt. Got me half of a circle.

That's what I did.

Ah. Thanks. I had not thought about that.

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Brainfart. I had 20 on my mind.
Let us know how it goes.
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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According to this chart with the blade set to 36 degrees you should get what you want (if you want a flat pentagon) otherwise you must take "slope" into account and adjust your bevel and tilt accordingly.
http://www.woodcraftplans.com/compound_miter.htm
Might find it interesting to see the tools used in making a barrel
http://www.rootsweb.ancestry.com/~flbbm/heritage/cooper/barrelmaking.htm
Might want to check that blade tilt - might be about 1/2 degree off the mark.
P D Q

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wrote:

Thanks. No slope necessary for my final task. It's a vertical barrel. It actually the housing for a piece of navigation equipment, the name of which escapes me at the moment, for a ship.

I think it's actually about 0.2 degrees off the mark, but I do agree it's off. My digital gauge does not appear to be precise enough, nor accurate enough. I measure the angle of the blade twice and get two different readings. I'm having to sneak up on the proper angle. So, the next time I work on this, I'll set the Unisaw's angle for the bevel and use a circular saw for the crosscut so I can just tweak the Unisaw instead of having to set it up completely again.

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