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Forum topic by jake36 posted 07-14-2009 12:23 AM 1152 views 1 time favorited 10 replies Add to Favorites Watch
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jake36

4 posts in 2729 days


07-14-2009 12:23 AM

I THINK that somewhere I have seen a formula which will allow me to make a staved cylinder of a certain diameter. I cannot seem to find it anywhere. If any of you know where I might find and copy this information I would sure appreciate it. I am trying to make some birdhouses for Christmas.

jake1936@bellsouth.net

Jake

-- Jake Caldwell


10 replies so far

View barlow's profile

barlow

129 posts in 3207 days


#1 posted 07-14-2009 02:47 AM

you take the number of staves you want to use and diviide it into 360, then take that number to get the degree of angle you need to cut, for example, I use twelve sides for alot of my segmented turnings, you would take 360 divided by 12=30 degrees, divide that by 2 which equals 15, that is the number of degrees that you need to set your saw for. An improtant thing to remember is that the fewer sides the more forgiving the tolerances, the more pieces the greater chance that even being off a fraction of a degree can add up fast to being off by several degrees at the end.

-- barlow

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dwinkel

6 posts in 2801 days


#2 posted 07-14-2009 05:25 AM

I did a little searching and couldn’t find anything so I decided to try to figure it out.

Disclaimer: I have only tested this on paper and I’m no mathematician but here’s what I came up with. Use with care!

d = diameter of vessel
n = number of staves
s = stave length

d • sin(180/n) = s

For example if you want a 4 inch diameter vessel with 12 staves each stave would be:
4 • sin(15) = 1 inch

-- Dan

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TopamaxSurvivor

17676 posts in 3143 days


#3 posted 07-14-2009 09:38 AM

pi x R (radius) squared will give you the circumference.

3.14×4 = 12.56 / 12 = 1.04”

Looks like ignoring that .035” in the trig calc is going to leave you about 1/2” short on the circumference. :-))

I doubt if the birds will ever know, As long as the staves are cut with the correct bevel, it will still come out.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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degoose

7196 posts in 2822 days


#4 posted 07-14-2009 11:04 AM

Bob.. Pi R squared equals area.. for the circumference.. it is 2 x Pi x R
Btw barlow is closest to the answer.. 12 staves need a 15 % angle on each side,
so ergo a 4” diameter is near enough 12 and a bit circumference aso as the outer width need to be a little over the 1 inch mark IFN u use 12 bits.,
I almost understand what I just typed.
Larry from downunder,,

-- Drink twice... and don't bother to cut... @ lazylarrywoodworks.com.au For lovers of all things timber...

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TopamaxSurvivor

17676 posts in 3143 days


#5 posted 07-14-2009 11:21 AM

You’re right!! :-(( Guess I’d better use pi x Diameter, eh? :-)) I wonder why the 2 calcs are .14” off?

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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jake36

4 posts in 2729 days


#6 posted 07-21-2009 10:09 PM

Thanks for all your help. Barlow seems to have one I can understand. Jake

-- Jake Caldwell

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DrDirt

4169 posts in 3209 days


#7 posted 07-21-2009 10:43 PM

Sorry I couldn’t miss the opportunity for a little pun

The roundest knight at King Arthur’s round table was Sir Cumference. He acquired his size from too much pi.

-- 'Political correctness is fascism pretending to be manners' ~George Carlin

View reggiek's profile

reggiek

2240 posts in 2737 days


#8 posted 07-22-2009 12:19 AM

I’ve used this reference for a couple of items – which pretty much says what Barlow did

http://www.woodmagazine.com/woodworking-tips/techniques/intermediate/staves-and-segments/

-- Woodworking.....My small slice of heaven!

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TopamaxSurvivor

17676 posts in 3143 days


#9 posted 07-22-2009 01:08 AM

That ’s a handly little table, Thanks.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View jake36's profile

jake36

4 posts in 2729 days


#10 posted 07-22-2009 08:41 PM

Gota thank you Reggick this is solving all my problems. Be sure to take your flea meds. Its a hot summer.

J

-- Jake Caldwell

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