Official Luthiers Forum!

Hi All.
I am just starting to build my first guitar from a LMI serviced kit based on the plans for a 1937 Hermann Hauser. On inspection of the parts I noticed that the pre-made bridge that comes with the kit has some differences to the Hauser design.
1) The pre-made bridge has a concave face on the rear of the tie block which has me somewhat puzzled. What is the purpose of this?
2) How do I install the bone tie-block reinforcement strips, in particular the aft strip? It seems that even a shallow rabbet may compromise the thin lip of the rosewood top edge too much.
3) The tie-block and saddle slot width on the pre-made bridge is 80mm, whereas the Hauser plan shows closer to 86mm. Does this matter?
4) There are some other slight differences from the Hauser plan such as the location of the saddle slot relative to the front of the bridge: 6mm vs. 3mm for the Hauser.
5) Also, the saddle slot (2.3mm wide x 3.6mm deep) is not cut square but at 95 degrees from horizontal. What is the purpose of this?







More details which may or may not be pertinent: The thickness of the bridge at both the tie-block and saddle slot is 9.9mm. The thickness of the wings: 4.0mm treble side, 4.7mm bass side. The bottom is essentially flat a couple of very shallow depressions that should disappear when surfacing to match the domed soundboard.

Thanks for any insight and suggestions. Joe

Joe-
Welcome to the OLF!

If you are making a 'replica' of the 37 Hauser, you'll want every detail the same, but if you are building a guitar based on the Hauser (Brune) plan, I wouldn't worry too much about the bridge differences between the LMI bridge and the Hauser.

IMO, You should think of the LMI bridge as a 'roughed out' bridge- there's plenty of finish work and shaping left to do. As you mention, shaping the bridge to the dome of the top will 'use up' a bit of the depth of the bridge.
On a first guitar, I wouldn't worry too much about small details like the difference in tie block length. Just make sure that the string separation at the bridge 'works' with the fingerboard width and taper in the plans. A quick diagram (full-scale) is a good idea for checking that, if you have any doubts.
BTW, it's the saddle location that's important (for intonation)- a mm or two difference in bridge location is not a big deal- so I wouldn't worry about the different amounts of wood 'in front of' the saddle.

The 'tilted back' saddle is considered by some makers to be 'better'- there's a tendency for the saddle to be pulled/tilted forward by the strings, and there are also ideas about having the string angles closer (in size) to each other on the two sides of the saddle.
Some possibilities:
Bridge blanks are quite cheap; you could buy a couple and make a bridge or two, if you want to take the time.
You could add a tie block overlay to the LMI bridge- keep it fairly thin, and you could take a bit off the top of the tieblock to make some room for an overlay. Solid bone (or ivory), or a bone 'frame' with a mosaic or other decorative inlay are both quite traditional looks.

Keep posting details/questions/pictures as you go- there are quite a few keen classical builders around the OLF and it's nice to see another build in progress.

Cheers
John

Thanks John for the welcome and feedback. Now that you mention it, the slightly tilted saddle makes sense in that the central axis of the saddle is more in alignment with the string forces; it seems having the foot of the bridge slightly forward relative to the saddle slot may help distribute the twisting force that the bridge imparts to the soundboard.



I’ll have to give the tieblock overly some thought. The concave face on the rear of the tie block still has me puzzled. I’m sure I’ll have plenty more questions once I get underway. Thanks again for your help.

Joe

Joe-
I've seen quite a few classical bridges with a 'lip' at the back edge i.e. the tie block not extending right to the back edge of the bridge. Your bridge may be a variant on that idea. You could always re-shape it to the 'lip' style if you wanted- it would take some of the width away from the tie block, which could be better-looking (?).

Thanks John. The lip at the bottom of the tieblock looks like a nice touch and actually mimics the Hauser plan somewhat if I’m interpreting it correctly. Could the lip at the top provide a better grab on the strings?


I think I might first try to inlay a piece of bone strip along the top edge while maintaining a bit of lip but with a shallower, more rounded profile. If that doesn’t seem to work I’ll trim the edge square to accept a rabbet or trim the top of the tieblock to make room for an overlay as you've shown.

Joe

Frankly, I'd ditch the bridge and make one from scratch. If you are building the whole guitar, you can make a bridge. It's one of the easier parts of a guitar to make.
I don't think there is even one of the "pre-made" bridges out there that is a decent design and without several of the rather wonky features you've shown us. Besides, they are all far too large, stiff and heavy.
Get the Sloane book as it has a very simple and effective process for making your own bridge, use the Hauser plan for specs........you'll be ahead of the curve when it comes time for the next one.

David-

Thanks for your input. Sloane’s book is accessible through our local library system so I’ll be sure to take a look at his bridge making method.

Joe