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Just finishing my 4th dreadnought. Used Cumpiano book for 1st three. Use ROB DVD this time. Some procedures are quite different. eg. ROB DVD uses a slightly thicker bridge.
I'm concerned about there being very little exposed saddle this time and wondered if this means the reduced string break angle could affect volume/tone. See pics below.


I found an earlier post in which some of you said you go for an exposed saddle height of 1/8" to 3/16".

Here are some measurements...
1.) Bridge height " 13/32" - this is a smidgeon over 10mm indicated on DVD
2.) Saddle exposed at bridge centre : approx 1/16", dropping away to approx 1/32" on sides ...and I still need to take a bit of the saddle on the high E.
3.) Height from soundboard to bottom of low E : 15/32" - so I don't think the neck angle is too low. Tell me if you think otherwise.

Should I sand 1/8" off the top off the bridge?
I have read that string break angle is really important on archtops but haven't seen the same comments on steel string acoustic type bridges.
As always, I appreciate very much the experts out there helping mugs like me get better at this.....
Frank

I'd reset the neck. It's probably underset. You could shave the bridge but down the line when you need to adjust it again you'll be double screwed.

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John Mayes
http://www.mayesluthier.com

If you set the neck according to the Cumpiano book that may be your problem. I found his measurements to low for my guitars. I think his book says with a straight, fretted neck, you need 7/16" clearance for a 3/8" bridge. I find 1/2" clearance to be much better. I guess a lot depends of how stout/flexible the finished guitar is.
I would certainly say though that you need more exposed saddle. I think you need a better break angle. At least it would be best. You could shave your bridge to 11/32". That would be a good thickness. Then if you still needed abetter break angle reset the neck.

Who or what is ROB?

If the action is good now (except for going a bit lower on the high E), your neck is not underset. You have a tall bridge at 13/32". Take it down by 1/16."

The crown of the saddle looks a little excessive. What is the fretboard radius? The saddle radius?

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

I'm guessing ROB is Robbie O'Brien DVD.

Darrin

Howard
As Darrin has already pointed out, ROB is Robbie O'Brien. DVD has been a great resource for me, and I much prefer using a radius dish and mould to Cumpiano method where you don't use either.
At this stage in my development, I would prefer to not remove the neck to do a reset.

I removed 1/16" off the bridge and that made a big difference. It sounded pretty good before, but there is noticeably more volume now. Very happy. Can't include a pic as I masked it up to do some touch up spraying.

Both Cumpiano and ROB start out with a 3/8" high bridge. But in setting the neck angle, Cumpiano says to get an airspace of 1/64"-1/16" above the bridge when running straight edge over fretted f'board, whereas ROB DVD says to get 1/32" below top of bridge. So there's a reduction in exposed saddle of around 1/16".

I was also curious to find differences in suggested slot depth. Cumpiano says no less than 3/16". ROB goes for 5/32". Kinkead goes for 3mm from the bottom. I forgot to mention in the original question that I had installed a piezzo undersaddle pickup. Being mindful of the pickup, I went for a slot depth which was 4mm from the bottom - thank goodness for that. So after taking 1/16th" of the top of the bridge, I was only left with about 3/32" to the top of the pickup. I was a bit worried about that, but it sounds great acoustic and amplified.

You were right about saddle curvature not being right. It was incomplete when pic was taken and I have fixed that now. (16" fretboard radius) This raises another puzzling difference re saddle curvature. Cumpiano says to get a curve similar to fretboard radius between high & low E, whereas ROB DVD uses a straight line.

Thanks again for your suggestions and questions.
Frank

One of the ways that you can further improve the break angle, which is very important on an acoustic, is to slot the bridge and not rely on slots in the pins. The pins, if already slotted, can be turned around if you slot the bridge.

The real benefit of slotting the bridge and using unslotted pins besides greater break angle is that the string ball will rest more completely on the bridge plate reducing wear, extending life, lowering taxes, regrowing hair....... Well 2 out of 4 isn't bad.....

As far as the saddle slot my rule of thumb is that 2/3 of the tree is under ground.

Here is a picture of a slotted bridge:

If you have the neck fretted, and with a straight edge your hitting the bridge not clearing it then you're underset. The way I do it is with an unfretted neck you put your straight edge on your leveled fingerboard and it should just barely touch the top of the bridge. So that once fretted it clears the top edge of the bridge by the height of the crown of your frets(minus the neck deflection from string tension of course). This will give you a sufficiently high saddle with room to take it down in the future if needed.

Now if you've got a overly tall bridge (which looking at your measurements closer this seems to be the case) then everything above goes out the window. You have to either reset the neck to match the tall bridge, and therefore creating some wicked fallaway or you have to make the bridge smaller. Sounds like you've already taken care of the issue.

Just for reference here are my bridge dimensions (forgive the cruddy CAD drawing on my part)

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John Mayes
http://www.mayesluthier.com

Another thing is to radius the top of your bridge. Yours looks flat which will leave considerably less exposed saddle at the high and low E and make the break angle shallower. I usually radius the top of my bridges the same as the fretboard radius with a little drop off towards the high E so the same amount of saddle is exposed across the whole length.
When doing the neck set I support the headstock and put 5 or 6 lbs of weight on the shoulders of the body to get a ballpark idea how much the neck will deflect under string tension. I like to see the straight edge just clear the bridge under tension unfretted. This usually gives around 1/32 clearance under tension fretted.
You have to get an idea how much your guitars will move after string up. That will probably differ a lot with personal design. They will normally settle in a little after a few weeks so starting out with around 5/32 of exposed saddle has been OK for me. Usually winds up around the sought after 1/8" as the guitar finds it's comfort zone.
Good Luck
Terry

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Just curious as to what the clearance underneath the G and D immediately in front of the bridge are. Sounds like you're around 15/32". That should be fine. I like mine to be no less than that but that should give you enough to take the bridge down to even 5/16" if you want. I typically make bridges 5/16" or 11/32" tall in the middle with a slightly shorter treble side than bass and try to match it pretty close to my fingerboard radius. You definitely need to consider slotting the bridge. Check out Bryan Kimsey's site for a good idea if necessary.

Good luck.

SR

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"We might not be big but we sure are slow"

John Mayes can you PM me or email me at sthomison@centurytel.net. I tried other things before post here. Thanks bro

I have yet to figure out why a break angle of more than 12-15 degrees would make any difference in the sound. Not saying it can't, I just can't understand the physics, and have seen no good experiments on it. I do know that altering the height of the strings off the top has an effect, but that's something else.

I'd be willing to bet that the improvement you got in the sound was due to the lower mass of the bridge. Try sticking on some weight and see if it reverses the effect.

The only reason I can think of that you need to have any saddle sticking up is to allow for later adjustment when the neck pulls up. That's an important consideration, of course.

Alan - this is probably a dumb question, but in suggesting I stick on some weight to the bridge, do you mean taking something like a bit of bridge plate (1/16") and taping it to the top of the bridge?