Hello All:
regarding the issue of go bars flipping over braces.
This has never , I repeat NEVER happened to me....
and please note that the above statement is a complete lie.
I have found out a few things though which REALLY help here.
I do buy the go bars from Luthiers Merchantile , they are fiberglass / cabon
fiber or something like that , with yellow rubber tips on the ends.
I find that :
1 If I leave the top of the braces a little taller and most importantly
flat on top , and remove the yellow tips from the end of the bar which goes
onto the brace, the sharp edge of the bar sort of digs into the brace a
little bit and stabilizes itself and doesn't slide off so easily. I can then
plane down the tops of the braces after the glue is dried.
2 If the bend in the go bar is too much, due to it being too long, I
alternate the ends of the go bars (the tips which articulate to the roof of
the box ) right and left of the brace, so the bends in the bars (I usually
use 5 bars per brace) oppose one another - thus equalizing out the sideways
pressure.. This helps prevent the braces from being knocked over on their
sides.
The Process I use works in this order .
The go bars on the ends of the brace go on first . As these bars go on one
MUST hold the brace in place
I usually sort of bow these first bars inward toward the brace so they
mirror image one another making sure that the tops of the go bars as they
touch the roof of thebox are absolutely directly above the brace itself so
that there is NO sidways pressure at all, only a for and aft pressure which
is compensated by the mirror imaging of the braces.
. The next 2 bars go on as close to simultaneously as possible with each
bowed as described above in a mirror image of each other right and left of
the brace .
These bars are for the middle of the brace.
I do this while still holding the brace in place with my free hand .. The
remaining go bars are easier as the brace is now pretty well stabilized in
4 directions and the glue is setting in.
The main thing one can do , of course, is to have MANY go bars and then cut
them into sets of sizes ... I use 3 sizes myself .
The thing to remember is that you want the go bars to bend only as much as
is needed to create the clamping force and no more. The least amount of
bend in the bar will help concentrate the force DOWNWARD instead of toward
the side as will be the case if the go bar is too long and therefore forced
to bend a great deal (like a bow) and for these excessive bends, I don'
think we gain all that much more clamping force anyway - for that, its
better to use more bars. . I feel that anything more than 1/2 inch
deflection of the bar is going to require equalizing the forces as
described above by having the bent go bars alternating right left as
described above and is border line too much of a bend in any case .
The three general lengths are to get a good bend at the aforementioned 1/2
inch max for various heights of materials under the bar.
The longest length is of course for small pieces .(this length is good for
the tiny braces over the rose area of a top )
The next shortest length is for holding down braces onto a top and is
perhaps 1/2 half to 5/'8s of an inch shorter , this is for general clamping
of braces onto the top.
The shortest go bar set is for clamping down bridges onto tops in which the
braces have been glued and which tops are being supported underneath by a
flat jig cut to lift the top up a little higher than the braces underneath
and supply a flat surface under the area of the bridge (as described in
David Van Edwards Course) these go bars are around 3/4 of an inch or so
shorter than the second set. The 3/4 measurement is dependent of the
thickness of the jig.
hope this helps ...
r
----- Original Message -----
From: <tam...@buckeye-express.com>
To: <dem...@suffolk.lib.ny.us>
Cc: <chagorra...@yahoo.com>; <rel...@sbcglobal.net>;
<lute-buil...@cs.dartmouth.edu>
Sent: Thursday, December 03, 2009 10:04 AM
Subject: Re: [LUTE-BUILDER] Re: Go-bars
Dana,
I've had a devil of a time using go-bars with lute bracing. Lute braces
are narrow and it's difficult to position the go bar so it doesn't flip a
brace over. If the pressure is even a little bit off-axis, there goes
your brace. I would imagine it's different with the wider bracing found
on guitars. The reason I use go-bars when re-gluing bridges is because
bridges are wider; then all of the advantages you cite come into play.
I would love to hear if anyone on the list has advice for using go bars
with lute bracing. Do you use the commercial fiberglass go-bars or
shop-made wooden ones? I think the original versions were hazel rods.
Tim
--- dem...@suffolk.lib.ny.us wrote:
From: dem...@suffolk.lib.ny.us
To: "Santiago Ramos-Collado" <chagorra...@yahoo.com>
Cc: rel...@sbcglobal.net, lute-buil...@cs.dartmouth.edu
Subject: [LUTE-BUILDER] Re: hide glue gram strength
Date: Thu, 3 Dec 2009 11:07:15 -0500 (EST)
having an appropriate jig to be able to carry this out as
fast as possible (forget about go-bars; I do not think they are a good
idea at all, unless one could tension several at the same time!)
try it before you give up, I think you will find it a popular solution
with many luthiers. The pressure possible from a gobar is just right for
the work, the space available is appropriate, and every gobar is a
deep-throat clamp with no reach problems.
The only faster setup would involve pneumatic plungers, which means a low
ceiling to attach them to and the risk there is an inability to see when
things have gone wrong inside (a small rib mispositioned tipping over for
example).
When I have it done, I shall share the
photographs.
they would be welcome by us, but not sure the list will forward
attachments.
--
Dana Emery
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