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I am building a 15" archtop inspired by the one Martin Taylor plays. I've only built 17" ones to date. How much would you scale down the F hole size going from 17 to 15"?
Thanks
Terry

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Hi Terry,

I use the same size f holes for all three of my sizes-16",17" and 18", so if I built a 15" model I don't think I wood scale it down. I guess it probably would depend on how big they are in the first place. I think mine are on the small side - I pretty much the D'Agelico style.

Thanks Brad,
Mine look a lot like the ones in your picture. I just used the ones on the LMI Benedetto template when I built my first and made a pin router jig with that size. They get smaller with binding which I usually use.

From looking at pictures of 15" models it does not look like they are scaled down a lot.

_________________
It's not what you don't know that hurts you, it's what you do know that's wrong.

Hi, Terence.
I only have a hunch about this, and everyone knows what my hunches are worth. But, that said, I think you could probably follow your instincts and come out just fine. Brad has reported good results with the same size sound holes in all three of the sizes he has built to date. I'm not at all surprised to read his feedback. Furthermore, when you look at some of D'Aquisto's designs from the mid 1990's, you will see some really huge sound holes. Those guitars seem to be highly prized by the people who own them. I think there's room for latitude and one's own design intuition.

All that said, I am currently building a 16" archtop and I took the trouble of scaling a photo of a Gibson ES-175 to get the overall length and the general width of an f-hole that I thought I might like. Then I drew an "s-hole" design of the same length, but a curving width that gracefully went as wide as the points on that Gibson f-hole. It's not as long as the s-hole on my 17" instrument, but it looks right to me. It suits my visual tastes. I am confident it will work out okay. I think if you stay somewhere within the norms for these sound holes (and the norms are all over the map) you will be okay. If you are unsure, just draw your top out on a piece of craft paper or whatever and see if your sound hole design looks pleasing to you in full scale. If so, and if it isn't radically outside of something you would expect to see on a 16" guitar, then I'll bet you'll be just fine with your 15" guitar.

Best of luck!

Patrick

If the unamplified sound of the guitar is your main consideration the theory is to combine the tuning of the wood resonance with the tuning of the air resonance so that the instrument has a nice even strong tone on all the notes in the bottom octave and a half. Making the hole(s) bigger raises the pitch of the air resonance and vice-versa. Small adjustments make a big difference in the balance and gutsiness of the low end of the guitar. Guitars with holes too big can be very pleasant and relaxed in the mid and upper ranges, and less likely to feedback on the lowest notes.
Since most arch-tops are played through an amplifier, I doubt if folks pay much attention to getting the holes just right anymore on guitars with a pickup.