Official Luthiers Forum!

I am nearing the end of my first build but I have a question that has been on my mind for a while, and would like to get some confirmation from experienced builders before I start another.

I made my braces by cutting close to the final radius on the band saw then used the radius dishes to sand them. When I sanded them on the dish, I tried to sand the brace near it’s actual location holding it as straight vertically as possible on the dish. I was thinking that if I just sanded a radius on the braces then when installed the braces would need to be normal (90 degrees) to the radius surface and each brace depending on its final location would be on a different vertex. But maybe this is acceptable. Would like to get this figured out before the next build.

No need to cut them on the band saw. A bench hook and a few strokes with a plane, then clean up in the dish. You may not need the dish if you're good with the plane.

_________________
Good judgement comes from experience. Experience comes from poor judgement.

If I’m understanding right, you’re worried about the angle between the brace bottom and the side of the brace?
The radius is so big that you don’t really need to worry about it. Sand it wherever you want in the dish and just keep the brace perpendicular as best you can.



Sent from my iPhone using Tapatalk

_________________
My Facebook Guitar Page

"There's really no wrong way, as long as the results are what's desired." Charles Fox

"We have to constantly remind ourselves what we're doing....No Luthier is putting a man on the moon!" Harry Fleishman

"Generosity is always different in the eye of the person who didn't receive anything, but who wanted some." Waddy Thomson

To add to this
Sand a certain number of strokes then flip it around and do the same number.
I do this to keep the bottom of the brace flat and avoid leaning to one side or another. It’s terribly hard to get a flat bottom for me unless I do that


Sent from my iPhone using Tapatalk

Sand them in the dish in pairs. This widens the collective bottom to prevent tipping...

I rough in braces on a router jig and sand in pairs similar to Ed, and also flip them round like SnoManSnow.
Maybe it's OCD, but I use shop made radius blocks with increasing grades of abrasives because my radius dishes have 60 grit in them.
The blocks go 100, 120, 180 to 240 grit, and I lightly mark the braces bottoms with pencil to see when they are done on each grit.
Also use the radius blocks to sand the rims to the higher grits for the plate domes.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I used to worry sanding each brace in its approximate location, but only for the back braces. I think I saw this on some web site and thought it was good idea. I found it difficult to do consistently and ended up with poor fits to the top when gluing up. Now I do what meddlingfool does, and sand them in pairs or three's and it works great. I also hit them with a plane first to get the basic curve, only finalizing in the dish.

_________________
Tony Thatcher
Bozeman, Montana

Was always curious about how the back brace 'should' be radiused. Perpendicular to the center of the dish where they all basically sit 'vertical' to that center? or should they be radiused perpendicular to the edge of the dish where they will be located?

Bad drawing attached

_________________
Thank You and Best To All

The difference is minimal and inconsequential.

Thanks Barry, was thinking the same thing but sometimes thinking can be my worst enemy...

_________________
Thank You and Best To All

For me it's inconsequential due to my process.

First I cut the rectangular brace. Then I use a jig that get it really close on the edge sander but with a spline curve. Then I sand the ends to thickness on the drum of the edge sander. Then I mark the center width of the brace and taper the sides on the edge sander. The likelihood of getting them exactly symmetrical is pretty slim, so worrying about whether they're slightly tilted by a smidgen one way or the other is pointless...

I radius braces using a hand plane setup that makes the gluing surface perpendicular to the side of the brace. Thus the brace is 'normal' to the surface of the arch when it's glued up. As my calculus prof used to say: "As the djangle goes to djero, the sine of the djangle also goes to djero. What I mean I am now explaining" He was from India... Anyway, the point is that when you're within about 3 degrees of perpendicular, it hardly matters. What's really important, though is getting that surface flat across the width of the brace, and making sure there is no twist from end to end. Yeah, I know, technically the bottom of the brace should be radiused across the width too, but the difference between 'flat' and a 15' radius over 5/16" is, as they say, 'small'. Making that surface perpendicular to a flat face of the brace ensures that there's no twist, and, of course, it's easy to check for roll on a flat surface.

You can also set up a fence in your radius dish if you're really concerned about rolling them...

Yes, this was the intent of my original question. Guess I couldn’t find a way to word it. So from what I gather here it really doesn’t matter much if the braces are tilted a little as shown in the first DWG.

The brace is going to be carved anyway, so I would think that it doesn't matter if isn't quite perpendicular...

_________________
Steve Sollod (pronounced sorta like "Solid")
www.swiftcreekguitars.com

I recall a thread or two on this in the archives, and the two views expressed seemed to sort as a) it does not really matter, as the loads are normal to the back so anything close to square is fine, and b) my OCD is really kicking in today, so the only acceptable solution is (fill in blank). We come down closer to a) than b), with Mr. Sollod's observation highlighting the related task of - having glued the braces on square or at some angle - maintaining that desired angle in the carved and voiced brace.

_________________
A constellation only takes shape when one maps the whole.
- Beth Brower