Guitar Making Tip number 126 is about thinning the rim of the top where it meets the sides in order to make more sound. The rim of the guitar flexes to allow the top to move up and down as the strings vibrate. More vibration means more sound. Here is how you do it.
Thinning the Rim for More Flexibility
There are a lot of little tricks that you pick up over time in guitar making. This is one that I learned a long time ago, and I don’t even remember where I saw it otherwise I would give credit. I imagine it came from my woodworking library, but I don’t know for sure.
It makes complete sense that since the top moves up and down as the strings move back and forth, that the flexibility of the rim will influence how well that happens.
If the rim were rock solid, the top would struggle to move up and down to produce good sound.
By the same token, if the top were paper thin in those areas it would allow the most movement but may get muddy as there is very little control. This is one of those areas where a small change makes a big difference. Here is how you can add some more flexibility to your guitar top…
How to Thin the Guitar Rim and Where
The rim of the guitar is where the top meets the sides. This area covers over half an inch or so of kerfing and side thickness. It’s in this area, and the area immediately before the top meets the inside edge of the kerfing that needs thinning.
If you reduce the thickness of your top to about half or two thirds of the normal thickness, you will effectively thin the area enough to make a difference. You do this on the outside, and carefully blend it into the top so that the edge does not look beveled.
You are going to end up thinning about an inch or so of the outside border of the top, from the sides, and then you smooth it and blend it into the top. This can be done with a cabinet scraper or sander. In the end, sand by hand to even up the sanding scratches and blend everything.
Thinning the Rim and Binding Thickness
If you are super intense on your binding strips, or you are the type that really notices things, you may see the 1/16th inch difference in the top binding and the back binding. If this is going to bother you, then plan it into your design.
You can accomplish this one of two ways. Either set the a taller strip a little lower, and carve it down, or set the same height strip 1/16″ lower than the top, and you can use that as a guide for thinning the rim.
Essentially, in the second method, you can thin the rim area until you meet the top of the binding strip. At that point, you know you are done. You also know that the job is fairly even looking all the way around.
Guitar Making Tip No. 126 – Wrap Up
Guitar Making Tip Number 126 is about thinning the rim area of the guitar so that the top can flex more. When the top flexes more and has more freedom to vibrate, you get more sound. More sound is better, and it’s easy to design into your guitar.
You need to thin the soundboard by taking off one third to one half of the thickness for the last inch all the way around the rim. This allows the outside edges to flex more. The added flex allows the top more freedom, making more sound.
As you thin that area, make sure to blend it into the rest of the guitar. You are going to lose about 1/16th inch all the way around. Thankfully, that small of a difference is fairly easy to blend into the rest of the instrument.
1,001 Acoustic Guitar Making Tips for Beginners
Tip No. 126 is from my book, 1,001 Acoustic Guitar Making Tips for Beginners, which has a thousand more great tips to get your first few builds on the right track. There is no secret to guitar making, just a lot of small things that you need to get right. These tips will help you.
If you have any questions about Guitar Making Tip No. 126, please leave a comment and I will be glad to answer them. Also, please Subscribe so that you don’t miss out on anything new. Happy building.