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top slope/bridge position
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Author:  Andy Zimmerman [ Sun Aug 21, 2005 6:32 am ]
Post subject: 
Hi
Newbie again
I am working on my second guitar and I have noticed the same issue on 2
straight. I am using a 25 radius for the top and when I place a straight edge
on the top as if it was the fretboard, it clearly shows that the fretboard will
be too high with regard to the bridge. (It looks like I will need a tall saddle)
This is WITHOUT look at neck angle. If the neck angle matches this top
slope angle, It looks like it will have too much of a back angle and therefore
the fretboard line will be too high over the bridge.   Any suggestions. I dont
want to sand the top
Author:  tippie53 [ Sun Aug 21, 2005 8:13 am ]
Post subject: 
     If you put a radius on the top , you need to do the same to the sides so you match the top and controll the positioning of the top.
     On way to see is what your neck angle is doing. Also are you using a building mold? If you aren't you will have little chance to control symetry and square.
     what the neck angle is , is irrelavant as long as you make the neck fit the top. Most guitars are set to a 1 to 1 1 /2 degree. I have seen them as high as 3 degrees.
      What kind of guitar is this , a nylon or steel?, we need that info to get you into the ball park
john hall
Author:  Andy Zimmerman [ Sun Aug 21, 2005 10:49 am ]
Post subject: 
This is a steel string and I did build it in a mold. The angle of the top
with respect to the side (heelblock) is about 3.5 degrees. This seem too
steep and the reason why I would end up with too high of a slope to the
bridge.
I guess I could make a taller saddle, but that would not be ideal.

Can I change the slope of the bottom of the fingerboard that overhangs
the soundboard to decrease the angle???? (Keeping the fretboard level on
top)
It seems that the 25' radius top is creating this 3.5 degree angle.

Suggestions.....HELP

How do I decrease the angle???

Thanks
Author:  Alan Carruth [ Sun Aug 21, 2005 11:53 am ]
Post subject: 
One thing that helps (and it may be too late on this one) is to remove some material from the top edge of the sides at the tailblock. Jose Romanillos talked about this at a GAL convention once.

I start out with the top edge of the sides straight before they are bent. There is a bit of taper in the bottom edge (done as per Cumpiano and Natelson), but the sides are taller than I will want them. When tey are bent I put them in the outside mold and trim off the ends.

At this point I plane about 4-5mm off the _top_ edge at the tailblock location (there's no block there, yet), tapering them back up to the wide point of the lower bout. Then I put the mold&sides in the top dish, top side down, and shim up the neck end until the gap at either end is the same. A white pencil can be run around the inside to mark off the rough shape to trim the top edge so that it fits the dish at that slope. Once the top edge is fitted pretty closely I work out the shape to trim the back edge so that the taper comes out right.

This does two things: it moves the 'top of the hill' up a bit toward the neck end, putting the bridge further back on the dome, and it also reduces the amount of fitting I have to do on the fingerboard extension.

It does not eliminate that fitting, though. I fit the joint so that the projection of the top surface of the neck comes out at the right height at the bridge location to establish the action and bridge height that I want, trying to take into account things like the amount the neck will pull up when the thing is strung. I end up with the end of the neck about 3-4mm above the top most of the time, and glue a shim onto the underside of the fingerboard to fit to the top.

The neck angle is most certainly relevant.
Author:  Andy Zimmerman [ Sun Aug 21, 2005 12:08 pm ]
Post subject: 
Part of my problem may be because I sand down the top edges sides to
match my 25' radius dome. My sides are taller then the final size to plan
for the taller section needed at the waist. I sand down until I have the
perfect radius AND the height of the sides are to my final dimensions.

Do any of you fit the fingerboard extension by sanding the gluing surface
of the fingerboard. If I do this I can have less of an angle on the neck as
compared to the soundboard. Granted the neck and soundboard won't
be dead level with eachother.

Mike above you mention tapering the sides. How do you do that??

thanks

Andy
Author:  RussellR [ Sun Aug 21, 2005 12:14 pm ]
Post subject: 
Andy

In this senario I would normally sand the soundboard, with the dome leveling jig as is shown in the jigs section. I have on one occasion tapered the fingerboard, but my execution was not as good as I would have liked and I wound up with a small lean on the neck, it has to be said this was my poor execution of the sanding that caused this.

Russell
Author:  Andy Zimmerman [ Sun Aug 21, 2005 12:31 pm ]
Post subject: 
Russell
The dome leveling jig just seems to level that part of the soundboard, but
can it actually decrease the angle???? You would have to put more pressure
near the soundhole vs. near the neck block
Author:  RussellR [ Sun Aug 21, 2005 12:40 pm ]
Post subject: 
Andy

You can adjust the position of the guitar in the jig so that you are only sandind the part nearer to the soundhole, if you take it easy and test fit the neck as you go, you should get a good fit and reduce the angle.

Russell
Author:  Michael Dale Payne [ Mon Aug 22, 2005 12:58 am ]
Post subject: 
For furture refferance If end the radius just pass the sound hole you will have a flatter FB mounting surface. I do this by not putting any radius in my upper transverse brace or upper transvers graft, and by gradualy flatting the sanding of the linings starting just past the the intersection of the x-braces at the waist.
Author:  Andy Zimmerman [ Mon Aug 22, 2005 3:41 am ]
Post subject: 
Thanks for all your help.
I sanded the soundboard by the fretboard extension, and have decreased
the angle a bit. It is still a bit large, but OK. My saddle might have to be a
bit tall, but not exessive.
If it is still too high, I will sand the gluing surface of the fretboard over the
soundboard to allow the neck to be set with less back set.

Thanks again
I cannot do it without all of your help
Author:  Michael Dale Payne [ Mon Aug 22, 2005 4:24 am ]
Post subject: 
I believe you said that you have fretted already.

If you have, you might try my method next time.

Set the neck angle with out frets in the fretboard shooting for the Fretboard plane to be .06 proud of the bridge. Level the bare fretboard to .04 proud of the bridge. Fret the fret board and level the frets to with in .08-.10 proud if the bridge. I find this method to be quicker and more goof proof than trying to set the neck angle with the frets installed, plus you dont have the missing last frets to deal with while mearsuing the neck angle. (you know the forward rock of the straight edge just as you are about to zero in on that cirtical mearsurement)
Author:  Kevin Gallagher [ Mon Aug 22, 2005 5:17 am ]
Post subject: 
   If you were to take more off of the tail end of your rim when your putting the radius on the rim set in preparation for the top installation, you will find that you'll eliminate this problem on your next guitar. I have a powered radius dish machine that spins my dish at relatively low RPM while I can adjust the four support points on the mold in order to allow any quadrant of the rim to be favored during the sanding process and adjust the tilt of the final location of the peak of the parabola that results from the bracing radius and side radius coming together to form the arch.

   Favor the tail block a little more next time and check the approach often as you sand the radius. I would recommend making a guage that has the same radius as your top bracing in the bridge area to lay across the rim in the lower bout at the point where the bridge will be to indicate the final top surface height and then lay a straight edge on that area of the neck block where the fingerboard tongue will be glued to check for proper clearance and approach there. I always end up with about 1/8" of clearance under a straight edge at the saddle location with no fingerboard or bridge in place. That provides a good dimension for me to have the proper bridge thickness and a good amount of saddle height to alow for future adjustment by the player. It also gives good height for the strings off of the guitar body and a sharp break angle over the saddle to the pin holes for tonal benefits.

    I slao have one of those sanding fixtures that I saw at charles Fox's shop and use it more to true up and flatten the area where the fingerboard tongue will be glued down. I use a flat bracing system under the fingerboard while using a 25 foot radius throughout the rest of the top.

    I've built nearly 500 guitars and have used this method for the last 350 or so and it has worked well for me.

Regards,
Kevin Gallagher/Omega Guitars
Author:  tippie53 [ Mon Aug 22, 2005 6:57 am ]
Post subject: 
    If you do the math the 28 foot radius will drop you a 1 1/2 degree neck angle ( aproximatly ) and the 25 foot will indeed give you a high location at the saddle.
      When I set the sides with the radius dish I check my location before I glue the top. I can adjust the heigth before the top is applied. I use a .100 thick top so I set the flat on the sides before the top is glued on. this helps to give me the straight fingerboard without the 14th fret drop or hump. You can sand the flat in like was previously shown but you need to be careful not to overthin the top.
    Also check to be sure the neck block area is square and the block is postioned well.
   You can make adjustment to the bridge and thin that a little to help. Remember you will learn more from a msitake than a success
john
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