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cornfedgroove
10-18-2009, 11:43 AM
Does this kind of thing increase vibration transfer. I got a pretty tall saddle and I dont figure it will be a problem, but it might look cool if I drilled a few holes in it for kicks. Thought that the decrease in saddle surface area might increase the transfer into the bridge regardless of how minute. Anyone got some technical jargon they'd like to share about this.

http://cgi.ebay.com/GERMAN-MAPLE-EBONY-6-STRING-BANJO-BRIDGE-BANJITAR-NEW_W0QQitemZ360192980824QQcmdZViewItemQQptZLH_Def aultDomain_0?hash=item53dd2cb758

RonS
10-18-2009, 01:43 PM
Having tried an ebony saddle (and a few other very dense hardwoods) I can say that bone still sounds the best.

koalohapaul
10-18-2009, 03:44 PM
I've notched out a few saddles when I absolutely couldn't solve a handful of balance problems with the pickup. I can barely hear the acoustic difference, but there is a noticeable increase in the individual string articulation., when amplified. Not night and day, but noticeable enough to be note worthy, in my opinion.

Keep in mind that tweaks such as those won't make or break a good ukulele. In a recent thread in the general discussion area, there was a question about why customs take so long and if they're worth the wait. For those of us that do both production and custom work, those little tweaks are what make the difference. However, they're a whole lot of little tweaks that add up to something that you can hear and feel.

cornfedgroove
10-18-2009, 04:38 PM
I agree

The thing about my cbu's is that I make my own thru-neck. I dont angle it off the body so I mount the neck to make sure the fretboard is pretty high above the top of the soundboard (1/2 inch - 5/16s maybe) to keep the action low. I had bought a few bridges from LMI, but the plastic saddles suck, so I cut, shave and swap em out with corian (much better). sometimes I jack up the math on the neck placement and have to make the saddle taller than normal LOL (sssh)...so I thought maybe I could pretty it up and help the sound by putting some holes in it.

Kekani
10-18-2009, 07:35 PM
Moveable bridges and fixed bridges activate the soundboard in different ways.

It seems to me that you're thinking the lighter saddle will improve vibration transfer. On the simple side, vibration transfer, as Paul alluded to, directly relates to UST's in particular.

In this case, really take a look at a moveable bridge (with a tailpiece) and a fixed bridge. Once you figure out how each works, or, what happens when you pluck the string, you may change your question to refer to the bridge (or bridge plate) rather than the saddle.

Hint: there's a reason the body is sometimes metaphored as an air pump (particularly guitars).

-Aaron

koalohapaul
10-18-2009, 08:42 PM
Now I feel dumb. After reading the abbreviation about a hundred times, I finally realized that "cbu" stands for Cigar Box Uke. The whole time, I kept thinking about some kind of composite material.

cornfedgroove
10-19-2009, 03:13 AM
you feel dumb? Kekani just went all technical on me...I didnt realize the a single piece bridge/tailpiece was a different dynamic than one with a separate tailpiece...nor did I realize that floating bridge was any different than a fixed one. I dont understand the airpump thing although I do believe I remember reading about a soundboard thicker in the middle and thinner around the edges somehow produces some air pump affect?? something like that. I suppose I need to read a book or two...although I hate that idea.

Kekani
10-19-2009, 10:51 PM
you feel dumb? Kekani just went all technical on me...I didnt realize the a single piece bridge/tailpiece was a different dynamic than one with a separate tailpiece...nor did I realize that floating bridge was any different than a fixed one. I dont understand the airpump thing although I do believe I remember reading about a soundboard thicker in the middle and thinner around the edges somehow produces some air pump affect?? something like that. I suppose I need to read a book or two...although I hate that idea.

I didn't mean to sound condescending, but its threads like these that all of the theorists come out, which usually supports fruitful, albeit sometimes outlandish, discussion. If you had the answer already, you wouldn't have to think about it. What good is that?

A while back, I presented a "question" so to speak to a mechanical engineer friend, it basically had to do with rotational forces and pivot points of a stressed member, pulled in one direction, with torque forces and resultant action. I didn't tell him what it was, but to make a long story short, it was the action at the bridge, and where the pivot point was. Once I told him what I was looking for, he responded, "I always wondered why guitars are larger at the bottom. Now it makes sense, or not, where the bridge is placed."

CFG - you're headed in the right direction, although, since you got it that an archtop generates sound differently from a flattop. . . what was the original question again?

-Aaron

cornfedgroove
10-20-2009, 05:58 AM
First off, you were not seen as condescending in any way...so its all good. There's nothing wrong with getting technical, its supposed to be that way. Some of us though are a little behind on the learning curve, so naturally there are discussions that involve specifics on point "D", and I'm only up to speed on A and B, and so its over my head. That is to be expected, and doesnt bother me at all. It is, after all, the luthier forum, and I...am not a luthier:D I will glean what I am able.

I believe Paul effectively answered my question...my question was not about the dynamics of floating vs fixed or even the air pump theory, but rather regarding notched saddles. I have had to improvise a larger saddle as you can see in the 2nd picture on this last post.

http://www.ukuleleunderground.com/forum/showthread.php?t=20509

I thought since I have such a comparatively large saddle, that there was more surface area to absorb and diminish the sound through the transfer process. Soooo if I notched or drilled some holes in the saddle, decreasing surface area, it would increase the amount of transfer to the soundboard. My question was effectively if that was theoretically correct, and then wondering if anyone had tried it to see if it worked out in reality.

Cigar Boxes are not "ideal" as you can imagine, so the little things do make a difference. I have a question about these strings that I'm going to post on Uke Talk forum, so I can kind of get a feel for how they effect the sound.

luckyd
10-20-2009, 06:33 AM
If you put your hand over the soundhole on a guitar, and tap the guitar on the lower bout, you will feel the air pump out of the sound hole, quite signifigantly. It's the fine line between stiffness, and too much flex that really make a guitar sing. I haven't experimented with ukes, YET, but that's right around the corner. And this discussion about bridges is enlightening.

Bradford
10-20-2009, 05:59 PM
A number of years ago, I was fortunate enough to have a customer pay me to experiment with bridge design on his mandolin. I made a number of bridges and saddles out of different materials, drilled holes in them, altered the feet and tried a number of things. In the end, the only conclusions reached were that bridges and saddles are often overlooked components that can make a huge difference in how a given instrument sounds. I now advise anyone making an instrument with a floating bridge, to make and try at least 2 or 3 bridges. The difference between bridges of the same design and materials is often amazing.

Brad

Matt Clara
10-21-2009, 03:27 AM
Why not make a bridge out of two parts, effectively extending the groove in the bridge where the saddle rests right through the bottom, so the saddle actually rests on the soundboard? Then it would be strings, saddle, soundboard instead of strings, saddle, bridge, soundboard...?

thistle3585
10-21-2009, 04:11 AM
Here is an interesting page on floating bridges and how modifications affect the tone. http://www.murphymethod.com/redbridge.html

cornfedgroove
10-21-2009, 05:06 AM
Why not make a bridge out of two parts, effectively extending the groove in the bridge where the saddle rests right through the bottom, so the saddle actually rests on the soundboard? Then it would be strings, saddle, soundboard instead of strings, saddle, bridge, soundboard...?

I made a mandolin one time with only floating saddle...no bridge. I didnt even have sound holes in it, and it was bought up right away by a true-blue player. He played it ten minutes and was like shaazaaam! "I want it". We both agreed soundholes would be interesting, but every instrument sounds different and when you find one you love, dont screw with it. I wonder if that saddle had anything to do with it. It was a cigar box mandolin, shallow body, thin wood and really sounded good for what it was. It sounded good enough where he said he'd play out with it and leave his 1918 at home...maybe I just got lucky.

cornfedgroove
10-21-2009, 05:17 AM
Here is an interesting page on floating bridges and how modifications affect the tone. http://www.murphymethod.com/redbridge.html

awesome information here...I am not a huge reader so this link is as far as I can make it in one sitting, but is really at the heart of the issue for this post

http://www.murphymethod.com/ebonybridge.html

like I said...I havent read any of the rest. Perhaps it gets even better, but such is my life. My reading level is great, but my attn span along with my ability and desire to sit for long times is lacking.

Matt Clara
10-21-2009, 05:59 AM
awesome information here...I am not a huge reader so this link is as far as I can make it in one sitting, but is really at the heart of the issue for this post

http://www.murphymethod.com/ebonybridge.html

like I said...I havent read any of the rest. Perhaps it gets even better, but such is my life. My reading level is great, but my attn span along with my ability and desire to sit for long times is lacking.

Well, let me sum it up for you. A hard maple bridge with a split foot, wings*, and a couple holes drilled in the middle make the best mandolin bridges.

*The wings were just a couple of slots cut in the side of the bridge, going in about a quarter inch or so, effectively separating the outer quarter inch of the top from the bottom.

DaveVisi
10-21-2009, 06:03 AM
Why not make a bridge out of two parts, effectively extending the groove in the bridge where the saddle rests right through the bottom, so the saddle actually rests on the soundboard? Then it would be strings, saddle, soundboard instead of strings, saddle, bridge, soundboard...?

I'm not sure how sturdy it would be compared to a single bridge piece, but I have seen this on guitars (usually steel string)where the saddle slot is routed all the way through the bridge. I have a guitar with a screw adjustable saddle that is built that way. The only thing that contacts the soundboard is the base that the screws are threaded into. Essentially the saddle assembly is in four parts, the soundboard contact (metal) the saddle (plastic, glued to metal ears that straddle the screw shaft) and two screws. This whole assembly sits into a rather wide captive slot routed into the bridge.

cornfedgroove
10-21-2009, 06:45 AM
Well, let me sum it up for you. A hard maple bridge with a split foot, wings*, and a couple holes drilled in the middle make the best mandolin bridges.

*The wings were just a couple of slots cut in the side of the bridge, going in about a quarter inch or so, effectively separating the outer quarter inch of the top from the bottom.

haha, I kinda figured it went something like that...I suppose you just have to remember that some elements of sound are subjective. I would say that it sounds like the wings and holes could aid in maximizing transfer, increasing volume and somehow keeping it balanced. i think there may be a certain range of wood types that would all be good choices...not just maple.

Kekani
10-21-2009, 06:48 AM
Why not make a bridge out of two parts, effectively extending the groove in the bridge where the saddle rests right through the bottom, so the saddle actually rests on the soundboard? Then it would be strings, saddle, soundboard instead of strings, saddle, bridge, soundboard...?

First, we are still talking about `ukulele, and not floating bridge instruments, right?

If the objective is to have vibration transfer from the saddle to the soundboard, then I suppose that would make sense.

Personally, the bridge is a brace and has its own function. The only vibration transfer I'm concerned about is from saddle to UST. For me, slotting to the board wouldn't make sense because:
1) I don't have a hardwood base for the UST.
2) I would have to route the slot with the bridge attached to make sure the angle of the saddle going into the bridge would all match up (this is something I do, along with a few others.
3) This would weaken the structure of the bridge, and the function I intend to get out of it. This alone would justify why not.

Just my $.02 - Aaron

Matt Clara
10-21-2009, 07:46 AM
First, we are still talking about `ukulele, and not floating bridge instruments, right?

If the objective is to have vibration transfer from the saddle to the soundboard, then I suppose that would make sense.

Personally, the bridge is a brace and has its own function. The only vibration transfer I'm concerned about is from saddle to UST. For me, slotting to the board wouldn't make sense because:
1) I don't have a hardwood base for the UST.
2) I would have to route the slot with the bridge attached to make sure the angle of the saddle going into the bridge would all match up (this is something I do, along with a few others.
3) This would weaken the structure of the bridge, and the function I intend to get out of it. This alone would justify why not.

Just my $.02 - Aaron

Seems like there are ways to deal with all of your perfectly legitimate points, except I'm not sure what you mean by UST, unless it's just the soundboard.

luvzmocha
10-21-2009, 10:30 AM
Seems like there are ways to deal with all of your perfectly legitimate points, except I'm not sure what you mean by UST, unless it's just the soundboard.

UST=Under Saddle Transducer

cornfedgroove
10-21-2009, 10:48 AM
First, we are still talking about `ukulele, and not floating bridge instruments, right?

If the objective is to have vibration transfer from the saddle to the soundboard, then I suppose that would make sense.

Personally, the bridge is a brace and has its own function. The only vibration transfer I'm concerned about is from saddle to UST. For me, slotting to the board wouldn't make sense because:
1) I don't have a hardwood base for the UST.
2) I would have to route the slot with the bridge attached to make sure the angle of the saddle going into the bridge would all match up (this is something I do, along with a few others.
3) This would weaken the structure of the bridge, and the function I intend to get out of it. This alone would justify why not.

Just my $.02 - Aaron

The idea of a 2 piece bridge doesnt do anything for me, but...

why are you just interested in the transfer to the UST...what about acoustic value?

and also...just for my own learning. that first comment about floating bridge instrument vs ukulele. Take a quickie and explain for me the different dynamic between bridges. Feel free to oversimplify if its involved

Matt Clara
10-21-2009, 11:08 AM
haha, I kinda figured it went something like that...I suppose you just have to remember that some elements of sound are subjective. I would say that it sounds like the wings and holes could aid in maximizing transfer, increasing volume and somehow keeping it balanced. i think there may be a certain range of wood types that would all be good choices...not just maple.

That site had links where he tested upwards of 30 types of wood. While he liked a lot of them, he liked hard maple the best.

Bradford
10-21-2009, 11:19 AM
Hey CFG, let me take a stab at it for you. In a carved top instrument with a floating bridge and tailpiece, the primary motion of the top when you pluck the string is up and down. That is why the center section of the top is carved relatively thick and the edges are thin. You want the top and back to act like a diaphram of an air pump. With flat top instruments, where the bridge is glued to the top the primary motion when the string is plucked, is for the bridge and saddle and top to rock back and forth, creating waves in the top. Understand that this is a simplified explanation.

Brad

luckyd
10-21-2009, 12:25 PM
And to add to Brads simple version, the saddle "vibrates" in three directions: Up and down, front to back, and side to side. And by side to side, I mean as if pivoting on an axis. The greatest movement is front to back, if I remember correctly. Then up and down, and then on the axis. And this all comes from the vibrations of the guitar top.The bridge is just that, a bridge from the vibrations of the strings to the top of the guitar, causing that air pump, thereby "pumping" the sound out of the sound hole. And I'm going home to check my notes on this tonight. And hopefully find the link to the article that theory came from. Paul

cornfedgroove
10-21-2009, 05:53 PM
sweet, thanks brad...thanks lucky

regardless of how simplified, that makes alot of sense and is a great start for my book smarts.

Kekani
10-21-2009, 10:10 PM
why are you just interested in the transfer to the UST...what about acoustic value?

and also...just for my own learning. that first comment about floating bridge instrument vs ukulele. Take a quickie and explain for me the different dynamic between bridges. Feel free to oversimplify if its involved

You've already gotten good responses, not only overly simplified, but pretty much exactly in the ballpark. Taking it to the place where I consulted with my engineer friend, pivot point was my concern, thus, the torquing action at the bridge, and the resultant movement in the soundboard "sweet spot". Although, some would argue that a 12-fret Martin Tenor sounds more like a Martin than a 14-fret does - the bridge placement is different on both. On the 12-fret, the bridge is right in the middle of the sweet spot, whereas the 14-fret is further up.

So, getting back to acoustic value. . .of course I'm concerned about that, but, from a torquing standpoint, more than a vibrational standpoint. I know, semantics . . .but, most of my instruments have a UST in it, and that's how they're played.

Funny, my friend, just today, is looking for a guitar (for another friend), but doesn't know what to look for. He found one with a pickup, and he understands that when plugged in, there's a certain amount of modeling that can be done. His theory also being, "When does he ever play unplugged? Never." My caution to him was that while modeling can take place, all a pickup is going to do is make a crappy instrument sound crappy louder.

So, that said, I think an `ukulele with a UST installed, needs to sound better acoustically than one without. And right now, I can't see the soundboard being a good surface for a UST (by the way, most of my soundboards are softwoods, not hardwoods), and I can see a two piece bridge being pulled apart by tension alone, but less overtension when a string is plucked or strummed. Longevity is the concern, and Derek Shimizu once told me in conversation, "Never sacrifice structure for sound." For me, if it sounds that bad, I'll just start all over.

-Aaron

cornfedgroove
10-22-2009, 03:43 AM
that makes sense...

I understand the UST thing, I have a way to amplify all my instruments (minus the banjo) for the versatility. I do lead worship at church and do various specials and whatnot, so its nice to have a variety of instruments and the ability to play plugged in with them. Although I do play plugged in on a regular basis, I play alot more at home unplugged...just relaxing or noodlin or whatever...but not everyone is that way.

I laughed a bit about a crappy acoustic being amplified, lol...its true. You also can take a quality acoustic instrument and ruin it with bad UST (tragedy) ...glad you cleared that up for me. I know where you're coming from now, makes alot of sense.

peace

Matt Clara
10-22-2009, 03:49 AM
You've already gotten good responses, not only overly simplified, but pretty much exactly in the ballpark. Taking it to the place where I consulted with my engineer friend, pivot point was my concern, thus, the torquing action at the bridge, and the resultant movement in the soundboard "sweet spot". Although, some would argue that a 12-fret Martin Tenor sounds more like a Martin than a 14-fret does - the bridge placement is different on both. On the 12-fret, the bridge is right in the middle of the sweet spot, whereas the 14-fret is further up.

So, getting back to acoustic value. . .of course I'm concerned about that, but, from a torquing standpoint, more than a vibrational standpoint. I know, semantics . . .but, most of my instruments have a UST in it, and that's how they're played.

Funny, my friend, just today, is looking for a guitar (for another friend), but doesn't know what to look for. He found one with a pickup, and he understands that when plugged in, there's a certain amount of modeling that can be done. His theory also being, "When does he ever play unplugged? Never." My caution to him was that while modeling can take place, all a pickup is going to do is make a crappy instrument sound crappy louder.

So, that said, I think an `ukulele with a UST installed, needs to sound better acoustically than one without. And right now, I can't see the soundboard being a good surface for a UST (by the way, most of my soundboards are softwoods, not hardwoods), and I can see a two piece bridge being pulled apart by tension alone, but less overtension when a string is plucked or strummed. Longevity is the concern, and Derek Shimizu once told me in conversation, "Never sacrifice structure for sound." For me, if it sounds that bad, I'll just start all over.

-Aaron

To begin with, I have no idea why I'm defending my crazy idea, but here goes. My suggestion that a saddle might rest on the soundboard, skipping the bridge, in no way necessitates a two part bridge, nor a structurally unsound one. There, said it. Anyone ever try one? No? Then it's a little early to be shooting the idea down, isn't it?

RonS
10-22-2009, 04:42 AM
To begin with, I have no idea why I'm defending my crazy idea, but here goes. My suggestion that a saddle might rest on the soundboard, skipping the bridge, in no way necessitates a two part bridge, nor a structurally unsound one. There, said it. Anyone ever try one? No? Then it's a little early to be shooting the idea down, isn't it?

Consider that some steel string guitars use pegs to hold* in the strings. The stings go through the bridge, the top and bridge plate. In other words the strings directly touch the top. There is very little, if any sound difference compared to a bridge that doesn't use pegs. **

*The pegs only hold the string in while turning and can be popped out after full tension is applied without the stings flying off. ;)

** I know some are going to argue this point.

luckyd
10-22-2009, 04:56 AM
Here's the article I referred to. It's pretty in depth, and has great illustrations. And I want to thatnk all of you, because I went back and reread the whole thing, and probably will again this weekend. It's very scientific to apoint, but very enlightening. Enjoy. Great thread. And I am intrigues about the saddle minus bridge idea. Just don't know about the whole concept. http://www.esomogyi.com/principles.html

Kekani
10-22-2009, 07:00 AM
To begin with, I have no idea why I'm defending my crazy idea, but here goes. My suggestion that a saddle might rest on the soundboard, skipping the bridge, in no way necessitates a two part bridge, nor a structurally unsound one. There, said it. Anyone ever try one? No? Then it's a little early to be shooting the idea down, isn't it?

Matt, no need to be defensive. The idea wouldn't work for me, and basically for one reason - Spruce soundboards and UST's will not match. There are more reasons such as where the leading edge of the bridge patch is placed, and other variables I didn't mention.

I do think this is a good conversation about bridge design, somewhat.

-Aaron

cornfedgroove
10-22-2009, 09:17 AM
disclaimer...certainly this is a hack idea, and I dont know how it would sound but...

if you lost the bridge and saddle was directly against the soundboard, you gotta find a new way to anchor them. what if you just fed the strings over into a pinless soundboard sort of thing. Make a series of holes on the back end of the saddle large enough to accommodate a knot or ball end...but give each hole a narrow tail that extends toward the saddle that will hold the string ends.

I dont know if you'd have to brace the soundboard or something, but its just a a thought I've had for a while, but never did anything about. My fear is that the pull on the soundboard from the strings may deaden the vibrations alone, or maybe have a tendency to rip through and damage the soundboard thus requiring bracing which may also dampen the soundboard.

WhenDogsSing
10-22-2009, 01:23 PM
disclaimer...certainly this is a hack idea, and I dont know how it would sound but...

if you lost the bridge and saddle was directly against the soundboard, you gotta find a new way to anchor them. what if you just fed the strings over into a pinless soundboard sort of thing. Make a series of holes on the back end of the saddle large enough to accommodate a knot or ball end...but give each hole a narrow tail that extends toward the saddle that will hold the string ends.

I dont know if you'd have to brace the soundboard or something, but its just a a thought I've had for a while, but never did anything about. My fear is that the pull on the soundboard from the strings may deaden the vibrations alone, or maybe have a tendency to rip through and damage the soundboard thus requiring bracing which may also dampen the soundboard.

Sort of like this...???...Please no comments on the excess glue...:D

cornfedgroove
10-22-2009, 04:27 PM
Sort of like this...???...Please no comments on the excess glue...:D

pretty much like that, but with only a saddle and no bridge

koalohapaul
10-22-2009, 08:27 PM
I think of the bridge as part of the instrument, rather than an extra part that doesn't need to be there. I understand where you're coming from, but to me it's kind of like reinventing the wheel.

A fixed bridge creates a point of torque, which is a good thing. The more torque on the bridge, the better stored energy in the strings can be delivered to the sound board. It's like having a loaded spring.

The second thing that the bridge does is distribute the stress from the pull of the strings across a wider surface area. Again, a good thing. Keep in mind that the whole sound board will vibrate with any string being struck, but vibration will travel most easily in the direction of the grain (longitudinal with the strings). Having a cross grained bridge helps distribute the energy across the latitude of the top. This is the same function that the bridge patch or sound bar serves. It distributes stress, as well as vibration across a larger foot print of the top, effectively allowing more of the sound board to resonate. Any kind of energy always finds the path of least resistance.

I've done bracing experiments in the past with no bridge patch, to see just how lightly something could be braced. Basically no bracing at all. Those instruments came out tinny, with sub par resonance.

Having only a saddle would force all the energy from the strings through a somewhat narrow choke point. Kind of like lightning going through a speaker wire. You would also eliminate most of the rocking motion that occurs with an anchored bridge/saddle combination, which means the top would be effectively moving only up and down.

As long as there's good balance between the string tension and stiffness of the top, a well designed bridge should help improve the sound, rather than detract from it.

Matt Clara
10-23-2009, 05:53 AM
Consider that some steel string guitars use pegs to hold* in the strings. The stings go through the bridge, the top and bridge plate. In other words the strings directly touch the top. There is very little, if any sound difference compared to a bridge that doesn't use pegs. **

*The pegs only hold the string in while turning and can be popped out after full tension is applied without the stings flying off. ;)

** I know some are going to argue this point.

Actually, I'd argue that once the strings have gone over the saddle, they aren't vibrating any more, so it stands to reason that affixing them to the sound board wouldn't make much difference.

cornfedgroove
10-23-2009, 06:55 AM
I think hes saying that the bridge acts as a channel...accepting the sound from the saddle and efficiently and evenly 'channeling' it out through the whole soundboard rather than just the saddle alone shooting all its energy into one small point that cannot disperse it throughout the soundboard effectively.

its about even dispersion throughout the entirety of the body allowing for even sound. I imagine in my head like a cone effect...yell into a orange cone and you get good amplification an dispersion along with more efficient use of energy and sound.

hence the bridge is an asset rather than hindrance

luckyd
10-23-2009, 06:58 AM
Sorry Matt, I'm with koalohapaul on this one. The bridge distributes the vibrations across the top. And as the Symogi article illustrates, a bridge needs to flex to distribute the vibrations. The bridge is just that: a bridge. Wood moves. Bone does not. So really, a saddle is a bridge to the bridge. Again, love this discussion. Are Uke people smarter than your average bear?

cornfedgroove
10-23-2009, 07:21 AM
so how much bridge is too much?

RonS
10-23-2009, 08:08 AM
so how much bridge is too much?

That is the real question.

I know in the guitar world luthiers like to keep ebony bridges between 22-26 grams in weight.

I'm going to guess... for a uke around 6-8 grams in weight should be good.