How to replace bridge plate with falcate bracing

[anthip]

Hi there
I'm new to this forum and building my first guitar. I was just seeking advice on a problem I've encountered. Long story short my scale length was miscalculated in initial stage of the build which means my bridge has had to be moved to the correct position on the soundboard. This in turn means my bridge plate is now in the wrong position on the enclosed box arghh! I have falcate bracing for a start and I've had to move the bridge back about an inch. Any suggestions welcome?

[Trevor Gore]

If the bridge plate is in the wrong place, so is the bracing. Moving the bridge plate (if it could be done) is unlikely to help, as your new bridge pin holes will probably want to penetrate a brace. Best thing to do is re-top. If you don't want to do that and fancy your luck, you could extend the bridge plate backwards (three separate pieces) and use a pinless bridge. If you've only just put the top on (no bindings, finish etc.) just bite the bullet and re-top.

[anthip]

Hi Trevor
Thanks for the advice (your guitars are brilliant by the way). Unfortunately the error was discovered whilst i was setting the bridge as a last step before my final sand so redoing my top may be a little difficult (and heartbreaking). I think i will go with the pinless bridge idea and hope for the best on the final tone of the guitar when extending the bridge plate inside the box.

[Mark McLean]

If the box is already bound and looking great, and you don't want to pull it apart again, another option is making a different neck/fingerboard with the appropriate scale length for the box that you have made.

Let's think through what that might mean...... When you say the bridge needs to move "back", do you mean towards the tail block? That would mean that you have made a box that has the scale length too short by an inch? What scale were you planning? Is it a 14th fret join? You can get away with a shorter scale than standard 25.4 inch Martin scale length, and it is not too hard to make a shorter scale fingerboard. You can even place it on the same neck and use up the extra inch of neck length by adding a zero fret and placing the nut above the break of the headstock angle. Or make a whole new neck to fit.

On the other hand if what you mean is your bridge is currently placed with a scale length that is too long, and your move would be towards the neck block - you could leave it where it is and redesign the neck and fingerboard for a 13th fret join.

Don't worry about wasting a neck if you have already made it. Nobody ever makes one guitar. You can just keep it for the next one.
Don't panic. This is what first guitars are for - it is a learning process. You are among friends here. We will get you over the trauma!

Mark

[kiwigeo]

Mark's suggestions are worth taking on. My nearly completed parlour guitar started life as a neck that was cut too short. The shorter scale (620mm) length parlour was a perfect use for the neck.

[kiwigeo]

Nobody ever makes one guitar.
Mark

Yeah but sometimes I wonder if I should have stopped after the first one..

[Nick]

Yeah but sometimes I wonder if I should have stopped after the first one..

Amen to that!

[anthip]

Hi guys thanks for all the advice and support. It looks like the bridge pins may just penetrate the bridge plate when moving back the inch towards the tail block and miss any bracing. (After the initial shock I have had a closer look ha). This was a sigh of relief, however do you think I would need to place extra support behind the existing bridge plate, towards the tail block, to prevent the bridge from excessive pull due to not sitting over the centre of the bridge plate? If so, how will this affect tonal quality? If not, another sigh of relief.

[Trevor Gore]

I don't know how closely you followed the brace/bridge plate layout in the book plan, but if you're moving things back ~ 1", your bridge pin holes are going to hit a brace or the bridge plate edge or both, whether you make the hole line straight or curved, according to my measurements off the plan. You want the bridge pin holes to be either well on the original bridge plate or well off and on a secondary bridge plate (and missing the braces). I don't see how you can do that if the layout is as per the plan, but shifted forward an inch.

The most prevalent failure mode of bridge glue lines is the top peeling off the bottom of the bridge. One of the major reasons for this is not having a progressive change in top stiffness as you move from the bridge footprint to off the bridge footprint. One of the main purposes for the bridge plate is to manage this stiffness transition. What you don't want is the top "folding" behind the bridge, making it ripe for a peel failure. That is what you have to design around. Given where it looks like your bridge pins are going to end up, I'd suggest giving a lot of thought to a pinless bridge and a supplementary bridge plate if you aren't going to re-top.

[anthip]

Thanks trevor your exactly right, il have to try and get a secondary bridge plate in...wish me luck haha...thanks for taking the time to offer your advice its greatly appreciated and well respected.