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Repeatable curve in wood

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MattStolton View Drop Down
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    Posted: 18 April 2017 at 12:37pm
I want to redesign my hi-fi mid top boxes, so looking for aesthetic as well as sound!

Rather than just a cubic box, I fancy going a bit curvy to the sides. I am happy to laminate up thin sheets to achieve this.

However, I am stuck in forming the actual curves.

So, I need to put identical curves (not radiuses, some form of "aerofoil" shape) on the bottom and top of my box, but also the same curve on a couple of braces. Imagine the normal rectangle for a bottom and top of a box, but sides are curved.

As per this - how do I form the MDF top and bottom panels, with a consistent curve, repeatable enough to make minimum 4 panels (2 tops, 2 bottoms, for a stereo pair, and probably a few more to form braces)



I haven't got a band saw, or CNC, so how do I go about creating a consistent curve (both LHS and RHS the same) to cut out multiple pieces. I have a decent 10" table saw and router, but stuck how to get a machined consistency to the curve, that is repeatable to cut both LHS and RHS

I reckon hand sawing, or even jigsaw, will not be repeatable enough or accurate

Answers on back of postcard, etc....
Matt Stolton - Technical Director (!!!) - Wilding Sound Ltd
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Panda View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Panda Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2017 at 12:57pm
Here is how I would do it in the absence of the CnC etc.

To get accurate curves you can always use sketchup or other cad / vector freeware to create a printable scale shape to trace. Draw / trace accurate pencil lines onto a spare piece of MDF. Rough cut with a jigsaw and carefully make a template by sanding to the line with a (friends) belt sander. You now have a template that you can rout more copies around with a flush trim bearing router bit. Even if not totally perfect you can be sure that each copy will be the same as the template!




Edited by Panda - 18 April 2017 at 1:02pm
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bob4 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bob4 Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2017 at 1:02pm
assuming you want a symmetrical shape, you would need to make only one router jig with the desired curve/shape. Simply flip the jig or the panel to do the second curve
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Post Options Post Options   Thanks (0) Thanks(0)   Quote colinmono Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2017 at 1:30pm
I used a FISCH Flexi Curve (from Axminster) recently to cut some curves with a router, worked well for me. Not cheap, but I didn't have a belt sander and hand sanding curves to make a template sounded like a pain in the proverbial.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2017 at 1:36pm
Why not go the whole hog and do it like these beauties?

http://philharmoniabyjeannouvel.com/en/
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MarjanM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2017 at 1:37pm
Find a local cnc place. Cut one template and do the rest with a router.
Marjan Milosevic
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MattStolton View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MattStolton Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2017 at 2:25pm
Originally posted by toastyghost toastyghost wrote:

Why not go the whole hog and do it like these beauties?

http://philharmoniabyjeannouvel.com/en/

Wow. Insane.

I have seen someone do layers of 1" ply, layered up to make the side walls, but not from individual plys!
Matt Stolton - Technical Director (!!!) - Wilding Sound Ltd
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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2017 at 2:49pm
As someone else said, jigsaw/cnc the template. Adjust till you are happy vs a printout or whatever. Then use flush trimming bits to make a whole bunch and form the sides against them.

Made some curved spice rack sides like this a few years back, still got the jig that I used to create identical pieces as opposed to trying to cut out no 2. same as the first. Worked perfectly.
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MattStolton View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MattStolton Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2017 at 2:54pm
OK, so spend 2 days making the perfect jig, to save 1 day of free hand cuts! Wink

I just wondered if I had missed something obvious, but looks I will make a jig up, to router the panels up then.

MDF worthy enough to make jig from? Shouldn't wear from doing a short fun of panels?

Matt Stolton - Technical Director (!!!) - Wilding Sound Ltd
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2017 at 3:38pm
Trial and error I'm afraid, Laminated curves will always spring back slightly. I would begin by creating a former made up of multiple templates spaced equally apart until youre at the same height as the panel you want to make (ideally spaced the same distance as the thickness of the template) Make the templates with excess width so they can be reworked to alter the curve if need be. I would start with a curve that ends 5-6mm tighter than you want it to be. Laminate your sheets togther and use a vacuum bag and pump to clamp to former. make sure you use breather material from the bag hose entry point across the length of the former to the opposing side. Repeatability with this method is good. You may just find yourself cutting your top and bottom panels to the curve it creates.

Make one template and use a flush router to make others. Need to use 18mm ply with a vac bag really.

Edited by SouthwestCNC - 18 April 2017 at 3:40pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2017 at 3:47pm
Just reread the brief ^ this may be a bit ott just for 4. MDF will work for a few. If you make a former for the outside of the curve as well you can hinge the two formers and just clamp instead of a bag.

Print the curve on paper and stick it to the template will give you a line to follow.

But to me you are working backwards. You make the curve panel and then cut the top and bottom panels to suit.

Edited by SouthwestCNC - 18 April 2017 at 5:36pm
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SamV View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SamV Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2017 at 5:21pm
Draw/sketch onto perspex, cut out using a scroll saw/jigsaw/sharp blade, hand sand down, use a bearing guided router.

Wanna borrow my ancient scrollsaw? I'll dig it out and see if it's still working.
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