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Mocking up an irregular part of a project

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Forum topic by CharlesA posted 07-06-2015 08:34 PM 630 views 0 times favorited 7 replies Add to Favorites Watch
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CharlesA

3021 posts in 1260 days


07-06-2015 08:34 PM

Topic tags/keywords: question

I’ve posted a few times about a couple of baptismal fonts I am building. Well, the bowls are finally done so I can make the wooden stands. Because these are custom bowls, they are slightly irregular. I have thought I might mock-up the bowls out of layers of foam insulation b/c I really don’t want to be using the, quite expensive, bowls in my shop as I shape the wood. However, I can’t quite figure out the best way to shape the foam to the exact (close?) shape. How would you do that?

I’ve attached a sketchup drawing of the font and a pic of one of the bowls (they’re quite different shapes).

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson


7 replies so far

View pintodeluxe's profile

pintodeluxe

4854 posts in 2276 days


#1 posted 07-06-2015 09:33 PM

I would use the real bowls, and mock up the angles with scrap wood.
A large diameter hole cut in plywood can suspend the bowl safely. The plywood can rest on sawhorses.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View gfadvm's profile

gfadvm

14940 posts in 2153 days


#2 posted 07-07-2015 12:21 AM

Charles, I saw a contour “duplicator” some where (HD maybe). It was basically a rectangle with a BUNCH of pins through it. You pressed it against the contour you want to copy and the pins mirrored the contour. Probably could describe this better but maybe someone will weigh in with a name or picture of this gizmo.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View tyvekboy's profile

tyvekboy

1337 posts in 2476 days


#3 posted 07-07-2015 01:47 AM

Here’s two methods for you to consider.

METHOD #1:

Assuming the bowl is symmetrical all around and not hand made.

Construct a BIG block of foam bigger than the bowl by about 2 inches wider and 4 inches taller using spray adhesive to glue the blocks together.

Rough out the foam to the approximate shape of the bowl but a little smaller.

Then stick some PSA sanding strips (about 8 of them) to the bottom side of the bowl – starting from the middle of the bottom and ending at the top lip of the bowl.

Then take the bowl with the sand paper strips and turn it into the roughed out hollow in the foam till it sits snuggly in the foam.

From this point you have several options.

OPTION #1:

You can cut slots in the foam where the legs would be attached to the bowl. Then you can use the shape of the foam to mark where the legs need to be cut.

OPTION #2:

You can find the center of the bowl shaped foam and cut 3/8 inch on either side of that center line and remove 3/4” of the pattern. Then Using the shape of the 3/4 piece of foam that you cut out of the pattern and trace the bowl shape on to a piece of 3/4 inch plywood. Cut out the bowl shape from the 3/4 inch plywood. Now apply PSA sandpaper strips to the plywood.

Using spray adhesive, attach the the 2 halves of the pattern to either side of the plywood even with the sandpaper.

Now glue up more foam blocks roughly the size of the bowl. Roughly shape this second foam block to the shape of the bowl, leaving extra foam on it.

Now using the foam and plywood glue-up, rotate the roughed out bowl shape in it and the sandpaper will make you a mock-up of the bowl.

=================

METHOD #2:

You could also make a plaster cast of the bowl after you coat the bottom of the bowl with some crisco to serve as a release agent. This could be done with solid plaster.

The container could be made out of foam that would leave about 2 inches around the bowl and about 2 inches higher. I would also make 3 or 4 pyramid blocks to place on the bottom of this container on which the bowl could sit. Place the bowl on the pyramids and pour plaster around the bowl till it is level with the top of the bowl. Be sure to vibrated it (use a ROS) to get the bubbles out if any.

When the plaster hardens you could then coat the plaster mold with crisco and mix up another batch of plaster and pour it into the greased mold. Vibrate to get bubbles out. When it hardens, you will have a duplicate of the bowl.

I think this method will give you a closer mock-up of the bowl.

If you mix some vermiculite into the 2nd batch of plaster that will duplicate the bowl, it will be lighter.

====================

Hope this gives you some ideas of how to do it.

-- Tyvekboy -- Marietta, GA ………….. one can never be too organized

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TheFridge

5765 posts in 949 days


#4 posted 07-07-2015 01:54 AM

Use the real ones. I know a guy that makes those too sometimes. He’s pretty awesome. Hand carved and gold leafed. Thought you might appreciate it.

Edit: I definitely did not do this.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

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CharlesA

3021 posts in 1260 days


#5 posted 07-07-2015 02:19 AM

Thanks for all the great responses. gfadvm, it’s a contour gauge or contour duplication gauge. I may use a bit of each idea.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

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CharlesA

3021 posts in 1260 days


#6 posted 07-07-2015 02:39 AM

This woodcraft product looks interesting. http://m.woodcraft.com/aHR0cDovL3d3dy53b29kY3JhZnQuY29tL1Byb2R1Y3QvMTQ4NDU1L1dvb2RSaXZlci1DdXJ2ZS1UZW1wbGF0ZS0zNy5hc3B4

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

View gfadvm's profile

gfadvm

14940 posts in 2153 days


#7 posted 07-07-2015 02:54 AM


This woodcraft product looks interesting. http://m.woodcraft.com/aHR0cDovL3d3dy53b29kY3JhZnQuY29tL1Byb2R1Y3QvMTQ4NDU1L1dvb2RSaXZlci1DdXJ2ZS1UZW1wbGF0ZS0zNy5hc3B4

Good find! They are somewhat proud of it though.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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