Official Luthiers Forum!

I have a few tops waiting to be glued on to their respective rims and I noticed something. I think my bridge plates maybe a little too far forward. In fact, I feel like I may have been doing this wrong in general. I've recently started thinking a lot about the role that the bridge and bridge plate play in the system. I've been using the saddle location as the center of the bridge plate instead of the pins. The good news as I haven't glued these tops on yet. I'm just wondering if it's worth all the time & effort to remove the old plates, make new ones and put them in the correct location. Am I going to see that much of an improvement as far as driving the top? I looked all over the net and found pictures of it done both ways. My own personal logic on it tells me that as long as the bridge is making solid contact with it and the X Brace, it shouldn't be that different. But then there is also the "rocking" factor. Curious to hear opinions on this point however subtle it may be.

Thanks,
-Aaron

_________________
"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

NOT AT ALL AN EXPERT HERE:

I have been using the saddle location to determine the front of my bridge location and putting the front of the bridge plate slightly forward of that and making it wide enough that the back of the bridge plate is slightly behind the bridge. I'll be following this discussion with interest since I don't really know what the right answer is.

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Depends on how thin the soundboard is and what kind of wood. If the soundboard is thin, it will flex more sharply behind the bridge, and concentrate stress there, like peeling off a strip of tape. But if the bridge plate extends behind the bridge, then the point of highest curvature will be behind that, so the back edge of the bridge joint is protected. Cedar and redwood have particularly low peeling strength.

Having some bridge plate in front of the bridge can be good too, to spread out the stress. I've heard of mahogany soundboards developing cross-grain cracks along the front edge of the bridge. Presumably they were very thin, so it would curve sharply there and concentrate stress. Not an issue on thicker soundboards, except maybe curly redwood which has short grain that will split very easily.

I'm not sure if large bridge plates have much effect on tone beyond adding mass.

I'm much the same as Brian, except I use maybe a slightly wider bridge plate, and try to leave the front of it at least 3/4mm ahead of the bridge(edit) and 6mm behind it, bevelling the edges of the bridge plate.
I think grain orientation is worth watching too. I like rift sawn, with the grain at at about 20 degrees to it's length, so it doesn't line up with the bridge pin holes.

_________________
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.

Thanks Colin, I should have added that I bevel the edges of my bridge plate so there is less stress concentrated at the edges. It sounds like you do go a little wider than I do. I would guess I am around 2 mm beyond the bridge location. I think I'll start going a bit wider and having a shallower bevel. The brigdeplate is thin so I don't see a few extra mm in width adding much stiffness relative to the whole bridge plate and bridge in that area. I would think the biggest effect would be added mass but I'm just thinking out loud.

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

I make mine about 1/2" wider than the bridge, with 1/8" in front and 3/8" behind, and the grain skewed 20°to 30°. Mine are very thin, less than 1/16".
I've been using maple, mostly because it works OK and I have a lot of scrap.
I bevel the front edge, but I frequently put a PTME brace along the back edge. The PTME is rosewood about 1/16"wide and 1/4" tall and extends to the X braces.

_________________
A man hears what he wants to hear, and disreguards the rest. Paul Simon

This is strictly anecdotal but I own a couple of Martin guitars from the 70's that had the large rosewood b/p's that extend almost all the way into the X. There is a well know Martin repair person who is known for removing these plates and replacing them with smaller spruce plates as the pre war guitars had. I had this person reset the necks on both my 1974 D-18 and 1980 D12-28 and on both guitars I had him replace the plates with the smaller ones. When the D-18 was returned to me my wife's comment was "you are playing louder tonight". I didn't think I was doing anything differently.

I build mostly small bodied guitars with pyramid bridges and make the plates pretty small. No problems so far....

I don't know what using the saddle or pins as the center is going to do. You just want the plate to extend past the front and back edges of the bridge. How much? I would say at least 1/8. But, keep in mind if your Bridge position shifts do to setting the neck you could eat up that much pretty easily.

_________________
Pat

Spruce!?! Does it not get chewed up by the ball ends? I have been using thin osage orange rift sawn and skewed.

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

The plate is there for strength and durability so the pins wouldn't chew it up-
hardwood would be best.
Although I don't think that its position matters as long as it does the job structurally.
To avoid possible belly bulge, often when re-purposing old nylon parlours to steel string the plate is enlarged
toward the tail block.
My opinion;
would be; next time, move toward the tail-block.

_________________
You just pick up a chord, go twang, and you're got music. -Sid Vicious

I've been making my plates about like what's being described here. Maple, 3/32" thick. I did bevel the edges on these. I just see this done a lot and figured it was an attempt to remove mass. Never thought about it as a gradual way to make a transition from stiff to loose. Love hearing the various perspectives on this subject.

_________________
"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

They replace the huge rosewood bridge plates with smaller maple units.... The only people using spruce are classical guitar makers...

The switch from Maple to Rosewood was most likely simply a cost thing - as they use cutoffs/reject Rosewood back and side wood. And they just weren't making maple guitars in the 70's....

Martin does a lot fewer maple guitars than in the 20's/30's.. Why buy a pile of maple lumber when you don't use it for anything else in the guitar....

Probably made sense.... Sourcing wood and holding inventory all costs money..

The huge dimensions were a response to warranty... Customers will complain about an awesome sounding/playing guitar that has a belly... Those same folks won't make a peep over a dead sounding guitar with no belly at all....

Luckily - some time has passed and we have had the wisdom of several prominent luthiers which stated "never trust a guitar without a belly"... Words to live by!

IMHO, the most critical part of the top on an x-braced guitar is just below the bridge. In that area, adding even a small amount of mass will make a difference in the sound. For that reason, I never extend the bridgeplate below the bridge. I use 1930's Martins as my pattern. The bridgeplate is 1 3/8" wide, and belly bridges are 1.400". The bridgeplate is centered under the bridge, so the bridge actually extends past the bridgeplate very slightly.
I would not worry about a bridgeplate that is a bit too far forward, as long as you have at least 1/4" of bridgeplate below the lower edge of the bridge pin holes for structure.

_________________
John

John, you believe the plate makes a big difference, so I would like to know your thoughts on pinless bridges. Is a plate required with this style of bridge? Is there potential for better results without a plate?

_________________
Wake up and smell the rosewood!

George Lowden designed and sells some mighty fine guitars, a pinless bridge is one of the key features. They do have bridge plates which are oriented with the grain 45 degrees to the plate center line.

_________________
Ken Cierp

http://www.kennethmichaelguitars.com/

"IMHO, the most critical part of the top on an x-braced guitar is just below the bridge. In that area, adding even a small amount of mass will make a difference in the sound. For that reason, I never extend the bridgeplate below the bridge."

Hi John,
Like you, I believe the most critical part of the top is the area below the bridge. Could you comment on what the difference in sound might be as you add mass or stiffness to this area?
Mario Proulx sometimes adds a small brace directly below the bridge plate (PMTE) and says the added mass can improve the tone. I know what works for one person may not work for another, and the "sound" one luthier wants may be different than another's. Both Mario's guitars and your guitars are highly regarded (I have not heard either) yet you seem to have opposite views on this part of the soundboard construction. Any thoughts on this?