Saddle channel depth in bridge

McQ7 · #1 01-08-2012, 07:09 PM

I was wondering if anyone knew if there was a recommended saddle channel depth for acoustic flat-top bridges? How deep can or should the channel go? I realize that too shallow of a channel could cause forward string pressure and risk cracking the bridge, just as a saddle too tall would also do. But is there a similar danger with regard to leverage if the saddle channel is too deep? It would seem that a saddle going all the way through to rest on the top of the guitar would provide the greatest transmission of energy, right?

stanron · #2 01-08-2012, 07:39 PM

Interesting point. Would the saddle bearing directly on the front cause damage to the softer wood?

McQ7 · #3 01-08-2012, 07:50 PM

Maybe so, with a typically narrow width of a flat-top saddle. Gypsy jazz guitars have rosewood saddles with two points each of about a half inch square resting directly on the guitar top (kind of like a violin bridge).

I am trying to figure out if it is necessary to place a rosewood plug into the bridge of my Alvarez 5052. It has a Gibson-like adjustable saddle, and when I removed the screws and metal saddle housing, I was left with a saddle channel going all the way through the bridge material. If I placed a saddle in that channel and rested it directly on the guitar top, the base that touches would be 4 inches long by 1/4 inch wide.

I'm prepared to just get a small piece of rosewood and insert it between the guitar top and the saddle, but wondered if it were necessary.

Tom West · #4 01-08-2012, 08:01 PM

McQ7: Have never seen that done and would recommend that you not do it that way. A deeper saddle is said to be better for sound transmition as well as being less likely to be pulled forward from string pressure.For a saddle that is .375 thick I would put in a slot at least .250 deep or a bit deeper.That leaves .125 to .100 between the saddle and the top.
Tom

McQ7 · #5 01-08-2012, 08:07 PM

Quote:

Originally Posted by Tom West

McQ7: Have never seen that done and would recommend that you not do it that way. A deeper saddle is said to be better for sound transmition as well as being less likely to be pulled forward from string pressure.For a saddle that is .375 thick I would put in a slot at least .250 deep or a bit deeper.That leaves .125 to .100 between the saddle and the top.
Tom

You are talking about recommended depth, but from the bottom of the saddle channel to the top of the bridge, correct? I am saying: what if the saddle is even deeper--as deep as the entire height of the bridge?

Tom West · #6 01-08-2012, 08:24 PM

McQ7: Missed your post about Gibson type saddle. Never use them and would replace with a regular belly bridge if you want the best out of the guitar.
Tom

stanron · #7 01-08-2012, 08:25 PM

OK, the Gibson adjustable saddle. That is a wider opening than the normal saddle. I can't see much difference between a saddle on a rosewood base and a saddle directly on the front at this width. Somewhere I have read about a rosewood filler glued into the gap and a normal saddle width routed out in this. It seems like a lot of work. If you can get a piece of bone that will fill the space you could make a saddle from that, low cost and no irreversible damage. Is there some metal hardware still in the bridge and can this be removed?

McQ7 · #8 01-08-2012, 08:26 PM

Quote:

Originally Posted by Tom West

McQ7: Read the first sentence of my last post.
Tom

Yeah, I am just trying to figure out which way you don't recommend. I am asking which method is the preferred one. Sorry for the confusion!

McQ7 · #9 01-08-2012, 08:30 PM

Quote:

Originally Posted by stanron

OK, the Gibson adjustable saddle. That is a wider opening than the normal saddle. I can't see much difference between a saddle on a rosewood base and a saddle directly on the front at this width. Somewhere I have read about a rosewood filler glued into the gap and a normal saddle width routed out in this. It seems like a lot of work. If you can get a piece of bone that will fill the space you could make a saddle from that, low cost and no irreversible damage. Is there some metal hardware still in the bridge and can this be removed?

My long term goal is to get the filler and then create a standard sized channel for a standard saddle, as you mention. However, I figured I would try this first as a cost-savings measure, and because it would be a fun project.

The Tusq oversized blank saddle will fit perfectly in my bridge, and there is no metal hardware remaining. Unlike the actual Gibsons, this design simply had two height screws connected to the saddle--and the screws rested on the top of the bridge. So nothing was actually screwed into any material. It was a relief to discover, I can tell you!

stanron · #10 01-08-2012, 08:37 PM

You might like to check this link.

http://frets.com/FRETSPages/Luthier/.../hbirdbr1.html

If you can get away with just changing the saddle you will be doing well.

McQ7 · #11 01-08-2012, 08:41 PM

Quote:

Originally Posted by stanron

You might like to check this link.

http://frets.com/FRETSPages/Luthier/.../hbirdbr1.html

If you can get away with just changing the saddle you will be doing well.

Oh, yeah, I've seen that one--what a nightmare! Yes, fortunately, my bridge looks completely normal, the top has no screw holes. I just have this huge saddle channel going all the way to the guitar top.

I actually just checked the height of the Tusq oversized saddle blank, and I might have to get a shim anyway. It is 1/2 inch tall, so that doesn't leave a lot for me to work with.

stanron · #12 01-08-2012, 08:46 PM

Good luck. Let us know when you get done.

McQ7 · #13 01-08-2012, 09:09 PM

Will do. May be at least a week, but I'll add some before and after pictures once the job is done.

Ned Milburn · #14 01-09-2012, 10:54 PM

Hey MQ7, the reason for not setting the saddle directly on the top wood (ie: cutting the saddle slot fully through the bridge) is for these reasons.

The bridge/saddle combination are the transmission unit of the vibrating string energy into the guitar top. If the saddle is sitting directly on the guitar top, well, the top is softwood and so some of the vibrating energy will be lost through friction and heat. With the saddle encompassed in the hardwood bridge, ALL the vibrating energy goes into the bridge (with less energy loss). The vibrating bridge, attached to the top with a LOT greater surface area than the saddle bottom, in turn vibrates the top of the guitar. So, the point is, you want to get all the vibrating energy into the bridge via the saddle, then into the top via the bridge.

Next, with a cut through saddle slot, the part of the bridge in front of the slot would be more prone to bending/warping forward due to the pressure of the saddle pushing on the slot. So, structurally, it seems to be important to keep some wood at the bottom of the slot.

If cut-through saddle slots were actually good, you'd likely see it as the present standard for steel string instruments, since it is pretty easy to slot through the full thickness.

McQ7 · #15 01-09-2012, 11:06 PM

Quote:

Originally Posted by HCG Canada

Hey MQ7, the reason for not setting the saddle directly on the top wood (ie: cutting the saddle slot fully through the bridge) is for these reasons.

The bridge/saddle combination are the transmission unit of the vibrating string energy into the guitar top. If the saddle is sitting directly on the guitar top, well, the top is softwood and so some of the vibrating energy will be lost through friction and heat. With the saddle encompassed in the hardwood bridge, ALL the vibrating energy goes into the bridge (with less energy loss). The vibrating bridge, attached to the top with a LOT greater surface area than the saddle bottom, in turn vibrates the top of the guitar. So, the point is, you want to get all the vibrating energy into the bridge via the saddle, then into the top via the bridge.

Next, with a cut through saddle slot, the part of the bridge in front of the slot would be more prone to bending/warping forward due to the pressure of the saddle pushing on the slot. So, structurally, it seems to be important to keep some wood at the bottom of the slot.

If cut-through saddle slots were actually good, you'd likely see it as the present standard for steel string instruments, since it is pretty easy to slot through the full thickness.

This all makes perfect sense--thank you for explaining all of this!
Do you have a standard saddle slot depth? Is it 1/2 bridge height? 3/4? My saddle won't be very tall above the bridge, but I do want to make sure my ebony shims/inserts are thick enough. My bridge height is .3125" and I have 2 shims coming from Bob Colosi that are .08" thick each. I was thinking I would use both of them to get about 1/2 bridge height. Any thoughts?