Bridge Design

I’ve been making the bridge for Geoff’s guitar so I thought that take this opportunity to mention an often overlooked element; bridge design. Now you may ask, if I’m so interested in bridge design, why mine looks fairly “traditional” and not shaped like an asymmetrical dog bone with a spilt saddle?

Firstly, the function of bridge is to transfer as much of strings’ kinetic energy into driving the soundboard as possible. Therefore you want to have a light bridge so that the strings’ energy isn’t taken up overcoming the inertia of the bridge (remember Alan’s mandolin bridge). That said, any design solution is always the best compromise; the solution that best fits all the conflicting specification points. Read on......

So, although I want a light bridge there are other considerations. You’ll notice, like some other luthiers, that I’m using a fairly wide saddle. The reason for this is to have more room for the adjustment of the strings’ intonation (there’s a good article on intonation on the Luthiers Mercantile International website). Some luthiers go for a split saddle but this just seems wrong to me; I feel that all the strings should be on the same saddle so that their vibrations can interact with each other, giving rich overtones. Also if the player ever wants to retro fit a transducer under the saddle, their options for a pick-up aren’t limited. The saddle slot is also cut deep for number of reasons; mainly so that the saddle is held firmly and doesn’t tend to lean forward (this would sharpen all the notes). Again, thinking of the future it’s deep enough to fit a transducer without having to route the slot any more, also if the action needs to be raised there is plenty of depth to fit shims under the saddle. With all the forces acting on the strings, there has to be a fair amount of wood in front of the saddle to support it.

Unlike many guitars, my bridge pin holes are parallel to the saddle; this gives a similar break-angle to each string- this break angle does affect the “feel” of the guitar and therefore should be close to equal on all strings. Also the pins are not evenly spaced. I use proportional spacing- the distance, centre to centre, between the 6^th and 5^th strings is slightly greater compared to 5^th and 4^th and so on. With evenly spaced pins, the gap between the 6^th and 5^th string is less than the gap between the 1^st and 2^nd, due to their comparative diameters. The use of pins to hold the strings makes a hardwearing wood such as ebony a suitable material- you could use lighter woods but I would be concerned that after a number of string changes the pin holes would wear.

I also like to cut 45 degree ramps for the strings so that they can break cleanly at a good angle over the saddle which helps to eliminate the risk of any odd buzzes.

The wings of the bridge are thinned to reduce some mass and all edges are rounded off so that there are no sharp edges for those players who like to rest the hands on the bridge. The curved belly at the rear of the bridge increase the surface area for gluing in a place where bridge can eventually pull up.

Quite a lot there eh? So that’s why you buy a hand made guitar!

Phil Hare update

Phil has been out and about with the new guitar, and there is a very nice comment on the Acoustic forum by Fliss, who saw him at the Raven Folk Club, “Oh, and yes he had the Gary Nava guitar - it looks and sounds stunning! I love the shape of it, the newness of the top which is still creamy white, and the aesthetic details such as the shape of the headstock (echoed in the fretboard end) and although I'm not a fan of bling, that rosette is very pretty!” Thanks Fliss!!

If you’re interested, here are a couple more videos that Phil made.......

Mandolins, Mandolins, Mandolins!

I’ve been getting on with French polishing Geoff’s OO- this is the first time that I’ve used Honduras rosewood and it’s really starting to look spectacular under a layer of polish.

Paul’s mandolin

Mandolins seem to be temporarily taking over! I got Paul’s mandolin playing last week; one thing that I enjoy about mandolin building is that, due to the floating bridge and tailpiece, you can set the instrument up prior to applying any finish.

Once it’s playing perfectly, it can then be stripped back down and the finish applied- Tru-oil in this case. The mandolin has a K&K pick-up installed. The K&K is fixed directly to the underside of the soundboard with an adhesive film and as the soundhole is far too small to allow me in insert my hand into the finished mandolin, I decided to fix it in place during the construction stage. This way, it can be fixed exactly where I want it and the soundboard’s surface can be prepared so that the film adheres correctly.

If I know that some accessory has to be stuck to the inside of an instrument, I will coat the surface with several layers of CA to seal the surface so that any adhesive film sticks really well.

“Red Mandolin”

You may remember the “Red Mandolin” from a couple of years ago.

Its owner, Alan, wanted me to make a new bridge for it with a removable bone saddle. He also wanted to me to make it as light a possible. Alan is a retired professor of engineering and has also made a few violins, so I respect his views and was happy to oblige. You can see the old and new bridges below.

Alan was delighted with the outcome and reports a noticeable increase in the instrument’s volume.

Richard’s Mandolin

You may also remember Richard’s English walnut mandolin, unfortunately he allowed a friend to play it and it picked up a few finger nail marks on the soundboard.

Richard can’t live with the marks, so I’m re-polishing the soundboard for him. Fortunately, the nail marks haven’t torn the grain, so they sanded out quite easily. I was surprised, however, at how resilient the polish was to sanding.

The case against using French polish is it perceived fragility. However, the polish is applied thinly and what ever medium you use, it is sitting on a very soft surface. With fingernail marks, it isn’t the finish that is scratched as such, but the wood that is underneath the finish is dented.

The “Standard”

I’m also designing a new mandolin that I’m going to call the “Standard”. In these times of austerity, not every musician can afford to own a bespoke, hand-made instrument. So in bid to build a mandolin that is more affordable, and that competes with the like of Moon and Fylde on price, I’m designing a no-frills instrument. Time is the most expensive component of any hand made instrument and building one-off instruments to a clients specific needs is extremely time consuming. With the Standard, I shall concentrate on the features that influence the sound and playability and strip back any unnecessary adornments. This will be a real exercise in "form following function." The result will be a beautifully sounding, playable hand-made mandolin at a reasonable cost to the player.

Watch this space for more information.........