top of page
Search
  • Pete

Uke design considerations

So having made good progress over the past month I've got a few design points to still square away.

One of my current sticking points is, what shape and style of bridge do I want?


Bridging the gap

The bridge is the component towards the bottom of the ukulele or guitar that holds the saddle (the point at which the string bends over setting the length of the string) and usually anchors the ends of the strings. In acoustic instruments, this is usually made from wood and acts to transfer the energy from the strings into the soundboard of the instrument which causes vibration and sound. In solid-bodied, nylon-stringed ukes the bridge also usually houses a piezo pickup strip (essentially a contact microphone). This sits underneath the saddle and converts the vibration of the strings into electrical signals.


The options are pretty endless in terms of shape, especially on a solid body uke. Style is a bit easier with 4 main options. String through, slotted, tie or pin. All have their pros and cons.


String-through

The picture above is stolen from the web from iriguchiukuleles.com and is an example of a string through bridge, where the strings pass through the bridge to the underside or inside of the uke and are prevented from pulling through with a bead pulling against the underside. A string through bridge isn't really an option with these solid-bodied ukes since I don't want holes and covers on the back.


Tie Bridge

This picture is stolen from the web from gotaukulele.com a great resource for uke reviews. This is a Shima JS ukulele with a tie bridge, the strings pass over the saddle, through the bridge and are tied around the bar at the back of the bridge. I'm not a fan of tie bridges, I find them a bit fiddly to tie neatly, and if you do it properly with each string end being tucked into the next one, changing out one string means fiddling with all of them. They are traditional on Spanish and classical guitars but probably not fitting with a quirky electric uke.


Slotted bridge

Image again stolen from gotaukulele.com, this is a slotted bridge on a Kamaka ukulele. Slotted bridges are very traditional, commonly seen on vintage Martin ukuleles for instance. The string is knotted at the end and pulled into a hollow in the bridge passing through the slot and over the saddle. They are simple to make and are nice neat options on smaller sized acoustic ukes where size and weight matter. Getting the string to seat neatly in the hollow and the slots neat can also be tricky.


Pin Bridge

This image is again from gotaukulele.com and shows a VTAB tenor uke with a pin bridge. Here, like on a string-through bridge, the string passes through the bridge inside the uke and is held with the help of a bead or knot against the inside of the uke. The pin helps to wedge and block the bead from passing back through the bridge. Pin bridges are becoming more common on modern ukes and are standard on acoustic guitars. They are a bit more fiddly to make, requiring tapered holes and matching tapered pins.


There are arguments that tie and slotted bridges are more prone to pulling away from the ukulele top due to the angle of pull in comparison to a string-through and pin style where the force is on the inside of the uke top.


Alongside headstock design (more on that later), bridge style, tends to be a recognisable feature of a particular luthier. I'd like to keep design continuity between this and other builds in an attempt to develop a signature style, but I'd also like to keep it simple.


The design I have come up with combines elements of string-through and slotted. On these solid-bodied ukes, it is essentially slotted without the slots, but on an acoustic instrument (or one with access panels) the same design could be used without the hollows and used as a string through bridge. On the solid-bodied ukes, I have used locating pins which help with positioning but will also help improve torsional strength and hopefully reduce the likelihood of the bridge being pulled away.



These bridges were made on the CNC from some ebony offcuts I got from Pete Howlett a while back.


First, the blank was thicknessed down to 8mm. Then, two mounting holes and the hole for the piezo pickup cable were milled along with the slot for the saddle. The outline was then cut.


The outer edges were rounded over using a round-over bit.


The outer wings were scalloped using a ball nose cove bit.


Next, the string holes were drilled


and the edges countersunk using a 60 degree bit.


Finally, the bridges were flipped over and the string hollows were carved. So whilst the CNC makes it straight forward to make reproducible parts, it is far from straight forward, with this single component requiring 7 machining steps.



So that's the prototype bridges done, next up headstock design and fretboard...


Stayed tuned for more updates. The ukes may have to take a back seat for a couple of weeks now as I have an influx of other projects that need some time.



10 views0 comments

Recent Posts

See All

Bình luận


Post: Blog2_Post
bottom of page