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So, I want to make an 1/2 oval shape base for a 1/2 oval shape top.

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Forum topic by mahdee posted 07-15-2015 12:09 AM 696 views 0 times favorited 16 replies Add to Favorites Watch
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mahdee

3553 posts in 1232 days


07-15-2015 12:09 AM

Topic tags/keywords: question

Hi,
In doing so, how do I determine the angle of vertical boards that make the base?
I am assuming to do that, I can’t just use a string and two nails to draw the oval. As far as the angle cuts, I am clueless at this point. Any ideas?
Thanks

-- earthartandfoods.com


16 replies so far

View distrbd's profile

distrbd

2227 posts in 1910 days


#1 posted 07-15-2015 01:25 AM

Maybe this video will help?:
https://www.youtube.com/watch?v=J48e1mVQ_Sg

-- Ken from Ontario, Canada

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mahdee

3553 posts in 1232 days


#2 posted 07-15-2015 01:35 AM

Thanks Ken. That will be a good reference for cutting the top. I thought I should make the base first. It is going to be made with vertical 2×4 or 2×6’s. In doing so, I have to figure out the angle cuts that follow the half eclipse. Very much like a whisky barrel sitting on its end. So, there may be a 15 degrees cut on both sides to create the curve for example. I wasn’t sure if there was a math formula that could figure the angle based on the X or Y axis.

-- earthartandfoods.com

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DIYaholic

19178 posts in 2139 days


#3 posted 07-15-2015 02:05 AM

Since the ellipse is not a circle…
I think all the angles would be different.

Yeah…. the calculus, that I can’t remember comes into play, I’m sure.
I would think a line, perpendicular….
to the slope of the varying curve….
would give you each angle.
That’s the best I can come up with….

Now my head hurts!!!

-- Randy-- I may not be good...but I am slow! If good things come to those who wait.... Why is procrastination a bad thing?

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mahdee

3553 posts in 1232 days


#4 posted 07-15-2015 10:39 AM

Thanks Randy. I think that might be the best bet. Cut the curve on a piece of cardboard, measure 4” increments and connect them to the center, place the boards on top and mark the lines inside and out.

-- earthartandfoods.com

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TopamaxSurvivor

17671 posts in 3140 days


#5 posted 07-19-2015 06:51 AM

It should be easy to do with the trig function tangent if you know how big both the top and bottom will be and the height.

-- 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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mahdee

3553 posts in 1232 days


#6 posted 07-19-2015 02:51 PM

Thanks Bob,
Assuming the top and bottom are 3’ wide and height is 32” How would the formula gets plugged-in?

-- earthartandfoods.com

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distrbd

2227 posts in 1910 days


#7 posted 07-19-2015 03:27 PM


Cut the curve on a piece of cardboard, measure 4” increments and connect them to the center, place the boards on top and mark the lines inside and out.

- mrjinx007


This the simplest way imho.I would try it first, the more complicated ways gives me a headache.

-- Ken from Ontario, Canada

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mahdee

3553 posts in 1232 days


#8 posted 07-19-2015 04:01 PM

I know Ken.. I think that is the way to go as well. Nevertheless, I like to see the formula as well. So many things can go wrong when I comes to wood and precise measurements.

-- earthartandfoods.com

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TopamaxSurvivor

17671 posts in 3140 days


#9 posted 07-19-2015 06:24 PM



Thanks Bob,
Assuming the top and bottom are 3 wide and height is 32” How would the formula gets plugged-in?

- mrjinx007

Maybe I don’t understand what you are trying to do? I envisioned a half an old fashioned coal bucket shape with the base and top being 2 different lengths and widths.

-- 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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mahdee

3553 posts in 1232 days


#10 posted 07-19-2015 08:01 PM

No sir, both top and bottom would be same size and shape and the “wall” would be flush with the edges of top and bottom.

-- earthartandfoods.com

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TopamaxSurvivor

17671 posts in 3140 days


#11 posted 07-19-2015 11:56 PM

so you want the intersecting angles of the boards that will make up the vertical sides. Sorry about the false hope. I probably could have figured those varying angles on the edge of the ellipse 45 years ago when I was a math wiz ;-) but that is beyond me now;-(

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

View ChuckV's profile

ChuckV

2880 posts in 2991 days


#12 posted 07-20-2015 12:33 AM

Determining the angles for just a quarter of the ellipse is enough. So, I would probably draw it out and use a bevel gauge to get the angles.

-- “Big man, pig man, ha ha, charade you are.” ― R. Waters

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jerryminer

528 posts in 905 days


#13 posted 07-20-2015 12:40 AM

Formula? Ellipses can vary so much and the size of the “sides” can vary, too, so a formula would be quite complex, with variables for length/width/number of facets/side width/thickness …

But if you draw it out full-size, you can take off the angles. Here is one example with approximate 4” sides:

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TopamaxSurvivor

17671 posts in 3140 days


#14 posted 07-20-2015 12:43 AM

Depending on how critical the fit needs to be the individual pieces will need to be custom coopered, then each angle custom fit. This could get quite tedious.

-- 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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mahdee

3553 posts in 1232 days


#15 posted 07-20-2015 01:54 AM

jerryminer, yes. It is too complex for a woodworking project and I should have known that before conceiving such a project. Bob, I totally agree. I think the beast course of action is to make the base and worry about the surface last. I went ahead and deviated from my original thought and am going to use a natural edge table to incorporate what
I had in mind originally. Next project, if this one is successful will be a stump. It is going to take me at least 4 months to figure this one out. I have already spent the last two weeks so far to get the natural edge at a 45 degrees using a sassafras board 3” thick. Thank you for all the input.

-- earthartandfoods.com

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