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bridge plate - - - footprint & x-brace
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Author:  phavriluk [ Wed Aug 30, 2017 3:07 pm ]
Post subject:  bridge plate - - - footprint & x-brace
I'm building up a pair or scratchbuilt steelstring guitars. I can leave the bridge plates rectangular, relieving the x-braces where they pass over corners of the bridge plate, or I can trim the bridge plate ends to nest the bridge plate inside the x-brace. Seeing as there is no difference in materials cost, just the time needed to relieve the x-brace to pass over the bridge plate - - - or not, is one technique preferable over the other? I can see why a manufacturer would want to avoid the extra effort to relieve the braces, but would the job be better done if that was done?

Thanks very much.
Author:  SteveSmith [ Wed Aug 30, 2017 3:15 pm ]
Post subject:  Re: bridge plate - - - footprint & x-brace
I prefer to leave the X-braces uncut and trim the bridge plate. Others may have a different preference.
Author:  Hesh [ Wed Aug 30, 2017 3:26 pm ]
Post subject:  Re: bridge plate - - - footprint & x-brace
The word is serviceability.

Inlet bridge plates can be far more difficult to service if they ever need it because of being inlet into the X-legs. The additional time and heat required may very well split a top's center seam and that will ruin your week.....

What Steve said, leave the X-brace alone and just butt the contact area of the plate to the legs. I beveled my bridge plates all around too.
Author:  phavriluk [ Wed Aug 30, 2017 3:33 pm ]
Post subject:  Re: bridge plate - - - footprint & x-brace
Much appreciate the advice, folks. Thanks. We learn one piece of information at a time, one technique at a time.
Author:  kencierp [ Wed Aug 30, 2017 3:33 pm ]
Post subject:  Re: bridge plate - - - footprint & x-brace
Another master repair person "Don Teeter" wrote exacty what Hesh stated, in his view tucking served no real purpose and indeed presented a repair person's nightmare.
Author:  jfmckenna [ Wed Aug 30, 2017 3:59 pm ]
Post subject:  Re: bridge plate - - - footprint & x-brace
Devils advocate:

I imagine the same could be said for tucking in the brace ends to the linings?
Author:  kencierp [ Wed Aug 30, 2017 4:19 pm ]
Post subject:  Re: bridge plate - - - footprint & x-brace
jfmckenna wrote:
Devils advocate:

I imagine the same could be said for tucking in the brace ends to the linings?


Not the same as a trapped bridge plate, if I had to replace an "x" brace likely I'd be pulling the top and there are work arounds like chipping out a section of ribbon lining --- I always inlet the upper "x" legs
Author:  Pat Foster [ Wed Aug 30, 2017 5:11 pm ]
Post subject:  Re: bridge plate - - - footprint & x-brace
jfmckenna wrote:
Devils advocate:

I imagine the same could be said for tucking in the brace ends to the linings?


IMO, tucking the upper arms of the x-brace is a different animal. The major force on the upper x-brace arms is downward in an area of the top that wants to sink due to string tension. In my book, that area needs to be pretty stiff, and without the support from tucking, the upper x-brace ends could be subjected to peeling away from the top, given that they're stiff enough in that area to prevent sinking. In the bridge plate case, most of that force is upward (at the tail end of the bridge plate) and tucking the plate wouldn't provide as much resistance to that force as tucked upper x-brace arms.

Pat
Author:  doncaparker [ Wed Aug 30, 2017 5:56 pm ]
Post subject:  Re: bridge plate - - - footprint & x-brace
On a steel string, I never knew anyone cut away parts of the X braces to make room for the bridge plate. I must have led a sheltered "guitar making" life until now. I have always seen the X braces intact, and the bridge plate cut to fit the space.

I tuck the upper legs of the X braces into the linings, but not the lower legs. They end before making it that far.
Author:  Hesh [ Wed Aug 30, 2017 11:39 pm ]
Post subject:  Re: bridge plate - - - footprint & x-brace
jfmckenna wrote:
Devils advocate:

I imagine the same could be said for tucking in the brace ends to the linings?


It's not the same thing. Brace ends are not intended to be removable in time or a known, known..... ;) of things that we may need to replace.

OTOH bridge plates do split, crease and because of lousy moulded plastic pins become damaged requiring servicing with possible replacement.

Tucking brace ends does seem to at least keep the thing in place making regluing easier and more precise since there is no lateral movement.

Some of the A-list Luthiers couple braces with the bridge plate as well. Somogyi does this. He's looking for vibrational transfer and addressing bracing and the guitar top as one connected structure and not individual parts. He gets bad marks for his "serviceability quotient" (I invented this term...;) ) but who's going to argue with someone who can get north of $25K for an instrument. His stuff sounds awesome too! As such perhaps it's prudent to put guitars with coupled bracing, not inlet bracing in their own category as far as serviceability.
Author:  phavriluk [ Thu Aug 31, 2017 8:07 am ]
Post subject:  Re: bridge plate - - - footprint & x-brace
"Couple braces"? Wuzzat?
Author:  jfmckenna [ Thu Aug 31, 2017 8:24 am ]
Post subject:  Re: bridge plate - - - footprint & x-brace
So now I'm hearing that some of you don't tuck in the lower X-Braces. I always did but started experimenting with just feathering them to zero. Well, I feather them to paper thin then put the lining on top of that thinking that it will help tack it down. I'm not sure what to think about the results yet. Sorry to hijack the tread :D

I'm reading Somogyi's first book now and he likes to think of that area as the 'Bermuda' triangle hahahha. I think a lot of what he says makes sense but I do wonder how much of a difference a bridge plate butted up to the X-braces VS one that is let a bit in really makes? In fact I can't imagine that a bridge plate that ends 1mm away from the X-Brace would really make that much of a difference. In the end though I guess a tiny difference here could make a big difference there.
Author:  Hesh [ Thu Aug 31, 2017 9:54 am ]
Post subject:  Re: bridge plate - - - footprint & x-brace
phavriluk wrote:
"Coupled bracing"? Wuzzat?


Imagine tone bars glued to the underside of the top as usual but notched so that they transition over the bridge plate and are then glued to the bridge plate too. The idea is better vibrational transfer. Does it work? Who knows, tone is very subjective.

Now with that image in your mind's eye imagine a bridge plate issue, wear, crease, the pin holes worn away permitting string balls to migrate upward through the plate, etc. and how difficult it would be to remove and replace the plate with 1) it being inlet into the X legs and/or 2) those tone bars spanning the top and plate in one pop.....

Not exactly a great example of serviceability. I'd post a pic but the Luthiers who I know who do this are 1) friends and 2) they consider their bracing scheme proprietary. We would have to lower the cone of silence.... and then scream at each other....;)

But it's the kind of thing that results in lots of colorful language when repair Luthiers have to deal with it AND the client will pay far more to have any repair done because of the increased difficulty and risk. As previously mentioned tops can split wide open too if unbridled heat on the inside of the box is required beyond a prudent degree and duration.

I know a guy who spit the center seam trying to remove an inlet bridge plate. He no longer works on guitars.....
Author:  phavriluk [ Thu Aug 31, 2017 10:07 am ]
Post subject:  Re: bridge plate - - - footprint & x-brace
Hesh, thanks for your comments. Got it. And all I did was try to find out (backhanded, I guess) whether a bridge plate works better (a) covering the entire bridge footprint or (b) could we end the bridge plate at the 'x' brace legs. Sounds like the consensus is 'b', for serviceability reasons.

The comments about Somogyi remind me about Ettore Bugatti and his wonderful and exotic automobiles. No design of his ever compromised design for serviceability. My guess is that there are some artistic parallels.
Author:  Hesh [ Thu Aug 31, 2017 10:29 am ]
Post subject:  Re: bridge plate - - - footprint & x-brace
Hey Peter, my pleasure and good questions on your part too.

Bugatti had one rule if I recall my manufacturing design education - use the very best! Where he may have gotten into questionable territory is the best by who's measure and what measure with serviceability as you said not that high on the list.

Regardless Bugatti automobiles are extraordinary examples of the highest caliber of human design and artistry in the automotive industry. Very cool cars!
Author:  Alan Carruth [ Fri Sep 01, 2017 3:22 pm ]
Post subject:  Re: bridge plate - - - footprint & x-brace
Ervin makes a really nice guitar, but he does so many things that are non-standard that it's impossible to say what the impact of any one of them is by itself. Although some folks are adamant about the tonal cost of having a gap between the braces and the bridge plate it's pretty hard to see why that would matter. It would be incredibly difficult to do any sound scientific testing on this, so what's out there is all opinion, more or less informed.

Back when I did more repairs I ran into the same problem on two pre-WW I Martin 0-17s. These had mahogany tops, and narrow pyramid bridges. The bridge plates were small, exactly the same width as the bridge, in fact, and they ended at full thickness right at the front and back edges of the bridge. This produced a whopper of a stress riser. As the bridges twisted forward over time the compression force concentrated along the front edge of the bridge on the top surface crushed the wood there, causing a crack that ran across the top right at the front edge of the bridge. Not a fun thing to fix.

Since then I've been extending my bridge plates beyond the bridge outline in the front and back. Since, IMO, the function of the plate is to keep the ball ends of the strings from chewing up the soft top I only leave it full thickness over the area that runs from the pin holes forward to the line of the saddle. Forward and aft of that area I taper it out to nearly nothing at the leading and trailing edges. This cuts down the weight and minimizes the stress riser. There's nothing like some repair experience to teach you what doesn't work.
Author:  phavriluk [ Fri Sep 01, 2017 3:46 pm ]
Post subject:  Re: bridge plate - - - footprint & x-brace
What a wonderful set of comments here. I'm grateful for everyone's time and willingness to share. Mr. Carruth's mention of tapering the bridge plates, and their overall footprint, too, might well be put to use on my projects. That's the sort of insight I was hoping to stir up. And they fit into my hope to find details that don't make their way into factory-made instrument, one reason or another but are easy enough to apply, if they're known.

Thanks, everybody.
Author:  Bryan Bear [ Fri Sep 01, 2017 3:49 pm ]
Post subject:  Re: bridge plate - - - footprint & x-brace
Thanks Alan! I never really thought about the plate only needing full thickness from pins to saddle. I bevel the edges to (hopefully) reduce the stress riser but I now see the wisdom in a longer taper/feathering out. I'll definitely keep that in mind.

Speaking of stress risers. . . I have often thought that letting the bridge plate under the X would create a stress riser at the glue joint between the edges of the plate and the endgrain edges of the braces. The torque of the strings will be trying to peel the back of the bridge and collapse the front and some of that force would concentrate at those weak joints effectively encouraging the glue line from the brace to the top to start to peel. I'm no engineer so I could be all wet here but it seems like it would make a bump to the bridge area more likely to pop a brace loose.
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