Weissenborn Top Bracing

[ozziebluesman]

G'day everyone,

Two years back I built two weissenborn guitars from the MIMF (musical instrument makers forum) weiss plan. At that time it was my first go at guitar building so I followed the plan. After building the guitars there is one issue that I would like to resolve before I embark on making another.

The issue is the bridge rolls forward under string tension and distorts the top. Below is the plan. The bridge size is 150mm x 30mm. Located according to the plan the wings do not pass over the X-Brace. When I built mine this issue was made aware to me so I made the bridges longer at 170mm but that did not fix the problem. For the bridge wings to pass over the X-Brace with the X-Brace positioned where it is the bridge would need to be over 200mm long and would not look so good on the guitar plus it may impare the tone. There is a triangle piece set in the X-Brace extending toward the bridge patch. which is 4mm thick and the bridge plate is recommened 2.5 mm thick. The problem as I see it is the area between the bridge patch and the triangle piece.

Below is a picture of an early teardrop Herman Weissenborn teardrop guitar. It has what is now been called a X-mas bridge patch. I reckon this design change may fix the bridge rolling problem and give the top much more structional integrity.


Any thoughts, recomendations greatly received.

Thanks in advance for your interest and advice.

Cheers

Alan

[Kim]

Alan,

A bridge can only roll if that area of the top directly behind the bridge is allowed to belly up and that area can only belly up if the area in front of the bridge is allowed to sink into the sound hole which is a notorious weak point of any "X" braced instrument.

I would look at closing the "X" brace a little so that it crosses the tips of the bridge. You could also lengthen the bridge a 'little' more then the plan indicates so that you do not need to reduce the free area behind the bridge too much when you close up the legs of the "X". I would also look at enlarging the bridge plate a bit, but not so much as in your example because I think it's over kill and will reduce the instruments potential to amplify.

I would also consider realigning the finger braces to be more perpendicular to the "X" so they come into play to resist the rotational force of the bridge plate and also glue in a cross grain soundhole patch to sure up the entire area between the front of the upper "X" legs and the UTB.


This is pretty rough and exaggerated, but sort of like this.



Cheers

Kim

[jeffhigh]

Hi Allan,
Both mine were built to the plan and are fortunately standing up well.
The original bracing around the bridge is a crazy mishmash IMHO and If I recall Tony Francis's comments correctly, he considers the later "Chrismas tree" bridge plate versions to be the best sounding of the original Weissenborns.
In addition to Kims comments,
It is also worth looking at your saddle height, How high above the soundboard are your strings?
AIR you went with a bone saddle whilst I used wire.

I am using 16-56 strings in open D and open C on my long scale 27"

[Richard]

My finger braces are two braces parallel to the x-brace.

My bridge plate is something akin to the teardrop photo; I don't go all the way with the christmas tree shape but it does extend up to the x-intersection.

I also use tonebars like on a Martin guitar (angled from the bottom of the bridge plate towards the end of the x's) rather than the horizontal braces which on their own do little to counter bellying or bridge rolling.

This is all my personal preference, but as soon as I stopped using the original odd assortment of plates and braces seen on the original Weissenborns and simplified it to a larger bridge plate and finger/tone braces that better stiffen the top I noticed a vast improvement in the top's stability.

[Dave White]

Alan,

As you know I did my own thing on the bracing on mine and three years down the track it's a solid as a rock in terms of the top geometry. My X brace angle is the usual 78 degrees. I spent most attention on the soundhole up to start of the hollow neck area using my usual soundhole patch and A frame braces but modified as there is no neck block:

[Rick Turner]

The thing to remember about original Weissenborns is that they're practically all falling apart and while they are a bit more consistent than Knutsen's guitars (absolutely no two alike), they're still all over the map as far as specs and design.

[Ron M.]

Hello to all.

Thanks Alan for starting this thread and everyone who has contributed. If you don't mind, I have a couple of questions:

1. Should the bat wing bridge points (or what ever kind of bridge wing points), sit within the confinement of the bridge plate, or is It ok for the wing points to overlap the bridge plate (sit outside)?

As you can see from the plans I ruffed out, I could certainly use a longer bridge, because the front of the bridge will not sit on top of the X brace as much as I would like it to. I lowered and closed the X brace as much as I could, and could still use a little more length on the bridge. The front of the bridge is 156 mm, but I need It to be 173 mm for It to sit comfortably on the X brace.

2. Is 173 mm too long for the Bridge length, and will It impede the soundboard?

Thanks

Ron M.

[ozziebluesman]

Kim: I thought of moving the X-brace toward the tail by about 15mm and then move the scale forward toward the soundhole by 15mm then use a little larger bridge footprint and that would place the wings of the bridge over the X-brace. My thoughs with the X-mas bridge patch was to make it 2.5 mm all the way. Just an extension of the bridge patch. The triangle piece in the plan is 4mm thick so by making that area 2.5mm it should not change the stiffness of the top much? I did use only two finger braces each side on my guitar but aligning them by your suggestion makes good sense. Thanks mate for your input.

Jeff: I like your point regard the wire saddle. I will try a wire saddle and see if there is as much rotation on the top. I found my blackwood weissenborn has not produced a problem anywhere near as bad as the sassafrass. Sassafrass is very light in weight and is almost a sortwood so it maybe that fact that is making the top distort. The sassafrass was not spot on quarter sawn like the blackwood was. Thanks Jeff.

Richard: May I say your guitars a first class. I had a friend Cuff (his nickname) call and see me Sunday. We have had many conservations on the email but never meet. He owns one of your weissenborns and it is spectacular and sounds great. What thickness do you make your oversized bridge plate? Your idea to use of martin style tonebars and two parrallel to the X'brace finger braces is worth thinking about. Do you dome your tops? Thank you to you for your thoughts.

Dave: Hello mate! I have studied your brace pattern and see your design works. My problem is lack of building experience and if I don't follow a plan I am in trouble. In saying that my 0-18 martin style guitar on the bench is my brace design so we will see if I have learnt anything over the past two years reading all the great guitar building info on this forum. Thank you for your input.

Rick: Yes most of the old knutsen and weissenborns are falling apart but you must remember these builders where innovators of their time so it is up to us now to build lap slide guitars that will stand the test of time.

Ron: G'day mate. Good questions there and someone with more experience than us will be along and answer your questions for sure. Thanks for becoming involved here.

Thanks agin everyone and I hop to see some more discussion on this issue.

Cheers

Alan

[jeffhigh]

Or even a low bone saddle Allan if you have much sitting above the bridge

[Allen]

Mine was built following the plan pretty muck, but with a 25' dome built into the top. I had used a 12 mm tall bridge, and then a tall saddle, as was recommended by several people on the OLF. This was way too much for the top, and I started cutting back the saddle until it's pretty much the hight that you'd get from some fret wire. The tone is much improved as well.

The top still had unacceptable distortions though, and I ended up gluing in another brace in front of the bridge patch, that fits snug between the legs of the X-brace. Also added a 2 mm thick spruce patch behind the the bridge patch all the way to the lower transverse brace (or ladder brace). Thinking that it would do something similar to the teardrop bridge patch. Seems to have helped a lot, and not impaired the tone.

The next time around the bracing is going to be much different to the plans. I look forward to everyones input.