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 Post subject: caul making tips?
PostPosted: Tue Sep 24, 2019 1:19 pm 
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Joined: Wed Aug 28, 2019 7:00 pm
Posts: 11
Hi I need to make some radiused cauls for my stewmac 000 model back. I don't own a band saw and I am not planning to get one anytime soon, so I was wondering if there are any recommendations for creating these?

My current approach is to roughly cut with a hand jig saw and then plane and sand it.


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 Post subject: Re: caul making tips?
PostPosted: Tue Sep 24, 2019 5:36 pm 
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Joined: Fri Mar 03, 2006 7:09 pm
Posts: 5968
Location: Hegins, Pa
you can use a deck of cards and fan them out for the radius

_________________
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com


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 Post subject: Re: caul making tips?
PostPosted: Tue Sep 24, 2019 9:06 pm 
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Joined: Mon Jul 28, 2014 7:50 am
Posts: 678
Location: Chadds Ford, PA
Before getting the concave sanding dishes, I used 1/8" steel cable (doesn't stretch), 16', anchored one end and drew the curve on both sides of boards then used a coping saw to cut the curve. I did a couple of boards and made a lamination. Belt sander made quick work of smoothing. Now don't use it except for backing when gluing braces sometimes (mostly use the dishes on the go-bar deck).


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 Post subject: Re: caul making tips?
PostPosted: Wed Sep 25, 2019 8:03 pm 
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Joined: Thu May 24, 2012 8:03 am
Posts: 1131
Location: Chestertown Maryland
You need 2 things go make an arc of a circle without having a 29 foot string

First is sagitta of the arc = the distance off a baseline the arc will be. And to get that, use this :

https://www.mathopenref.com/sagitta.html

Second is an easy way to make the arc. Here you go (sorry - the forum only allows one URL - piece this one together):

flickr dot com slash photos/ruby1638/9566635434/in/album-72157635172644427/[/url]

and here is a batten in use, both as a sanding batten and as a caul. I just cut these out of an older (stable) 2X4 on the bandsaw and then 60 grit sandpaper on a rubber block to even them out. Stick sandpaper on the batten for a sanding batten, leave the sandpaper on for help in gluing when you use it as a caul.

1) shows the amount of "sagitta" or offset in a 15' radius, 24" long beam. Note the 1/2" bolt/pivot

2) shows sanding - the bolt that comes up out of the baseboard is not installed in this shot

3) shows clamping against for back braces

Sorry - this forum only allows 3 pictures or I would show you how the braces are shaped against the same batten. After 9 instruments I still don't have a dish or a go-bar deck and won't pursue either. It just take a minor amount more time to do it this way

Ed


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 Post subject: Re: caul making tips?
PostPosted: Thu Sep 26, 2019 11:41 am 
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Joined: Wed Aug 28, 2019 7:00 pm
Posts: 11
Thanks for the comments - actually drawing the arc isn't the problem as I can just trace the shape from the pre-cut braces that I am using.

The issue was really is there a way without a full band saw to cut cauls to the shape of the arc.


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