Soundports

I've posted Matt Mustapick's observations on soundports before, but it seems an opportune time to do so again:

"This concept came originally from the great classical maker Robert Ruck, who puts two small holes on each side of the guitar, very close to where the neck joins the body, rather than one larger hole. The main advantage of the soundport is that it gives the player a "front row seat" to enjoy a strong direct signal from the soundbox. This feature takes nothing away from the forward projection of the instrument. From 20 feet away the guitar is just as loud. For anyone closer to the guitar, it adds a great deal of richness to the sound, owing to the dual sound source which creates a stereo field."

Prior to marking and cutting the side soundports, I took the precaution of gluing two thin layers of veneer to the inner surface of the sides as reinforcement.

Cross-grain veneers provide a measure of protection against cracks

In recognition of the veneers' primary purpose which is to strengthen the area around the ports, their grain runs perpendicular to that of the sides. Some builders argue that cross-grain veneers actually promote cracking by restricting the expansion and contraction of the sides that would otherwise occur. While I accept that such veneers do indeed limit the capacity of the sides to move with fluctuations in humidity, the distance between the linings in this area of the upper bout is small and any potential dimensional change is minimal. If it was a credible risk, we'd surely see cracks developing where the headblock and tailblock similarly restrict the sides' movement across the grain.

In addition to their practical role of protecting against cracks, the veneers also provide me with an opportunity to introduce a contrasting maple line around the walnut guitar's port and extend the rosewood guitar's black and red theme.

Dremel extension handpiece with mini circular saw blade fitted - before and after

A mini sanding drum in the Dremel handpiece takes me to the line

Final sanding required, but essentially, they're done

Very soon, I'll prepare myself mentally for the onerous job of installing purflings and bindings - a task that never seems to get any easier or less stressful!

A recent guitar, with soundport

Useful links:
The Shrinkulator is an online tool that calculates dimensional change in wood with variations in moisture content or relative humidity.



Cheers
Pete

Notable Firsts

This is a guitar project I've had very little time to work on lately, but with the Australian blackwood/Sitka spruce triple-O featured in my last post about to head off to its new home, I delude myself with the notion that with one less guitar to complete, this East Indian rosewood/Engelmann spruce effort is somehow closer to completion too.

With a side soundport and a Florentine cutaway, there are some personal firsts for me with this instrument. This has also been my first experience using Grafted Coatings' "other" water-based finish, KTM-SV, which I've written enthusiastically about in earlier posts. KTM9, Grafted Coatings' previous foray into water-based finishes, was successful up to a point and still has its advocates, but there have been enough negative reports over the years that I eventually discounted it as I considered a switch to sprayed finishes. I think it's fair to say that in many people's experience it hasn't stood up well to normal wear and tear or, most alarmingly, to the corrosive effects of some people's perspiration. To date, I've read no reports of a similar nature regarding KTM-SV - fingers firmly crossed!

The soundport is an increasingly popular feature and proved a simple addition, which perhaps accounts for the fact that some professional builders offer it as an option at no additional cost. Adding the port is a relatively easy task which I completed once kerfed linings had been glued around the rim and the back had been attached to the sides. The guitar sides diminish gradually in depth as they approach the neck area, and it was easy to glue in a similarly tapered veneer laminate to wedge snugly between the linings as cross-grain support in the area of the port. I chose a simple oval soundport which was marked on the outer face of the side with the aid of a flexible plastic template and a white ball-point pen. I used my Dremel and a tiny circular saw blade to roughly cut through the side and the backing laminate well inside the line, then sanded to the line with the Dremel and a mini sanding drum.

The cutaway presented a more formidable challenge, with much head-scratching and several sleepless nights required before a plan of attack was formulated. Bending the cutaway section of the side on an electric bending iron was easy enough, but binding the point of the cutaway proved a little trickier; I chose the ambitious approach which was to mitre the joints in three dimensions. The outcome wasn't perfect, but having now negotiated the process more or less successfully, I can see ways to improve the end result next time around. Generally, it's only after I've addressed a problem and found myself unable to identify a potential solution that I become temporarily dejected and briefly contemplate other less taxing hobbies!

Cheers

Pete