Official Luthiers Forum!

This morning I put strings on a '37 Hauser inspired guitar, and much to my dismay, I realized that i located the bridge ~20 mm short!! Unfortunately, I used some locating dowels in the saddle slot that will now be outside the bridge foot print. (there are no words for how I feel right now!)

Anyway, i think i am looking at a top replacement. I've done this a few times with mixed results, i.e. it's been hard to keep the fit so tight that i have a good look around the perflings.

My questions:

1. Do i need to remove the FB, or can I cut through at the 12th fret and work around it?
2. Should i just plan on new binding/perfling? I could keep the side perflings...
3. Any other advice?

thanks in advance!

If this was a guitar I just built which sounds like it's the case then personally I'd just do a total do over binding and all. There are elegant ways to save the binding but since it's a new guitar anyway then I'd probably just do it over.

I would definitely remove the fretboaard as well.


That sucks man, one of those live and learn mistakes. Try not to be too hard on yourself

Been there almost. Yes remove the fretboard. Rout the old top off or use a Gramil or something similar to cut around the top at the binding, and chisel it off. You may or may not be able to save the transverse braces. Make your new top and put it in the hole. Cut a purfling channel and insert purfling to cover any gaps. I did as above, and replaced binding and purfling. Made it a little easier as the top didn't have to be a perfect fit. If you are careful, you can save your rosette. Cut around it carefully, and sand the wood from the back until you have maybe a couple of tenths of a mm left on there to hold things together. Re-set it in the new top. I cut around the peremeter, leaving about a half mm or so and sanded to the outer ring of purfling.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Pretty much what Waddy said

It won't make you feel any better but I did that exact same thing on a commission, but mine was worst 1" off location since my habit was/is to measure from the 1" mark and not use the ruler end --- matter of fact that incident led to the invention of our (KMG) bridge setting tool.

_________________
Ken Cierp

http://www.kennethmichaelguitars.com/

Option 2... replace the fingerboard with one cut for a 20mm shorter scale length

Thanks! I can't figure out how i made such a goof..Live and hopefully learn. Great advice on saving the rosette, i will definetly try that.

I should post a picture or two, it looks awesome, before surgery starts. First time use of Royal Lac and i think i like it.

Brilliant, Dennis!

....and buy a Saddle-Matic.

I briefly considered a "custom" scale length of 630 mm, and if this was my guitar, I would try it....

I'd really get more input from the classic builders regarding a "short scale" conversion. High tension and high tension strings in general tend to make these nylon string instruments respond well and I believe as expected. I am just guessing but its seems likely that a reduced scale length could end up sounding pretty flabby on a sound board braced for the higher tension. Not to mention that the bridge has been placed off the sweet spot likely in a more restrictive position.

_________________
Ken Cierp

http://www.kennethmichaelguitars.com/

Here's another choice, maybe even easier and with no side-effects to play. Pull the bridge with care - get it pretty warm. Dowels are likely very small - carefully flatten with razor blade so they are flush with the top. If not, you'll have to make small spruce plugs to replace them. Sand back the finish on the top. If you've done a good job with bridge removal, it should not be evident. This is a fresh glue-up so it should come off pretty easily. With the top clean, go about locating the new bridge location. Tape the bridge patch off, just shy of the bridge size by maybe a 1/16". Measure twice, cut once - make sure the bridge is in the right place. Refinish the top. Pull the bridge tape and let finish cure. Once cure, install the bridge. Use tape to build up an edge that locates the bridge exactly where you want. Prior to installing bridge, chamfer the bottom of the bridge edge all around so it "hops" over the finish (remember the finish is 1/16" inset). Glue the bridge and you should be all set.

You are probably wondering about the bridge patch inside. Don't worry about it. Many classical builders build without the patch - you either got that in the right place, or it is inset toward the sound hole and, either way, irrelevant.

As for the two plugs .. as long as you flush them, it will be ok. If you are super concerned about looks, consider refinishing with an amber toner ... but honestly I would not re-top that guitar - it's far more complicated. I don't know that I'd change the scale either (though it is a brilliant idea) - first of all you'll have to get the scale perfect to the bridge offset (it's probably not 20mm exactly), and a short scale will play differently. You may not care, but ... I'd rather have two small wood circles in the top in front of the bridge than change how the guitar is suppose to play.

Keep asking questions!

Andy

Have a look here............!!
http://www.grevenguitars.com/retopping-demo.html
Tom

_________________
A person who has never made a mistake has never made anything!!!

Thanks - I've seem the Greven demo and actually have used it on a couple of experimental instruments. I've got it to come out pretty clean, but not perfect.

As to pulling the bridge and relocating it with plugged holes - I just don't know if i can get it to look acceptable. I suppose there is no harm in trying since I can always re-top. (The bridge patch is in the correct position, I just goofed measuring when I located the bridge.)

I'll pull the bridge today and see how it comes off and what the dowel holes look like....

Rather than leaving dowel plugs showing, you could carefully rout 1/2 way through the soundboard between the rosette and the new bridge location, and in line with the plugs. Then insert offcuts of the soundboard (following grain lines if possible). By ending the splints at the rosette and slightly under the bridge, the splints if well done will be inconspicuous and undetectable to most people. Use high clarity hot hide glue if possible.
If it's a fail, you can always drop back to the retop option.

Clay makes a good point.

Post some photos. There are a few solutions to minimizing the plugs. How big are they? You could also drill them out and replug with spruce plugs (just use a plug cutter ... and maybe scrap top material if you kept it). To your point, you can play with fixing it. I suspect you could do so satisfactorily. Remember that when you take on a far more complex solution, you also introduce more opportunity for things to go wrong.

Best of luck and post pictures!

Andy

I haven't done this, but read of others. If you are not happy with the hole plug result, the next step before a more extensive repair would be to carve out a slight depression, such as with one stroke about an inch or less long with a narrow chisel just a bit wider than the plugs. Then cut a sliver of some matching wood and glue it in proud. After drying, sand down. If you are not adept at the chisel, I think just sand in a little dimple and press the patch in and glue it. I don't know all the glues, but you need one that won't show. If I were doing it, I would use Elmer's school glue, because it seem to me to be the most invisible after drying, If this doesn't work, just move on to the next more extensive try.

Other threads periodically offer that such errors are opportunities for novel decorations. Usually, you do not see that on classical tops, but what the heck. Maybe some little flower inlays.

A bit of an update on this adventure: I tried "scooping" in a spruce plug and inlaying a matching strip from tail to rosette. Both were good learning experiences but neither looked good enough. I followed the Greven method and routed off the top and was able to save the rosette. The new top is in place, but i decided to redo the top perfling and part of the binding. All of this looks good! (I will try to post pictures!). The big problem now is that the box is pitched too high, at ~ 113 hz. (no bridge) I am not quite sure how i got here since i tried to match stiffness of the plate to previous results...

I haven't done any perimeter thinning or general plate thinning, but i am interested in feedback on how to lower this resonance. It seems like a long way to go and to avoid 110 hz (A string).

As an interesting note, this guitar has sound ports, and when closed, they move this resonance down to 107 hz.

Thanks in advance!

A bit more of an update: I have managed, with some fairly aggressive wood removal on the top in the lower bout, and around the edges in particular, to get the resonances down to more comfortable numbers. I also fitted the bridge more accurately. (Did not follow the practice of arching the bridge more than the top as Hauser seems to have.) This top is constucted with a 1.5 mm dome in the solera. With everything glued up, the first resonances come in at 105/100 for ports open and closed. (Not my practice to glue the bridge first and then finish, but... I wanted to be sure I was done thining the top)

My initial thoughts on the sound is that it is and will be a success ! The resonance sits pretty comfortably beneath A and not on G#. This is a bit high for the Hauser design, but i don't think i can get this any lower.

If I wanted to adjust a bit more my choice seems to be to work on the back bars, removing wood from the center to get better coupling.

Any thoughts on this?

Thanks!

A bit more of an update: I have managed, with some fairly aggressive wood removal on the top in the lower bout, and around the edges in particular, to get the resonances down to more comfortable numbers. I also fitted the bridge more accurately. (Did not follow the practice of arching the bridge more than the top as Hauser seems to have.) This top is constucted with a 1.5 mm dome in the solera. With everything glued up, the first resonances come in at 105/100 for ports open and closed. (Not my practice to glue the bridge first and then finish, but... I wanted to be sure I was done thining the top)

My initial thoughts on the sound is that it is and will be a success ! The resonance sits pretty comfortably beneath A and not on G#. This is a bit high for the Hauser design, but i don't think i can get this any lower.

If I wanted to adjust a bit more my choice seems to be to work on the back bars, removing wood from the center to get better coupling.

Any thoughts on this?

Thanks!