Flat top with f-holes

[Magnus Geijer]

I'm building a little single cutaway guitar shaped flat top here, and I was planning to use f-holes. Well, f-holes of a sort, but anyway. I was going to use a bracing pattern from a flat top guitar, but realized that everything I've seen has been round/oval holes.

Any ideas on how to brace this thing to make it structurally valid, or is it just a bad idea to begin with? I'm building a guitar from the same design alongside it, and I would assume that a bracing pattern could be transferred from one to the other, just at a different scale?

Thanks,

Magnus

[Paul Hostetter]

If you could post an image of the top with the "sort-of f-holes" you had in mind, it would be easier for a few of us to visualize the possibilities. Something's going to have to change, but it depends on what you have in mind for the soundholes.

[Magnus Geijer]

Here's the concept. Never claimed I could draw.

The shape is really a straight rip-off of the plans in the Benedetto book, scaled down to mandolin size, obviously.

I was thinking about something beginning with an X and adding crossbraces from there.

Thanks,

Magnus

[billhay4]

Why not go whole hog and make it an archtop? Then you'd imitate Benedeto's braces, too.
Bill

[Paul Hostetter]

Like this?

http://www.lutherie.net/benedetto.top.web.jpg

I have no idea how he braces this thing. It looks flat in this photo, but with a $21K MAP I hope it's carved.

In either case, a couple x-bracing ideas might be:

http://www.lutherie.net/benedetto1.jpg

http://www.lutherie.net/benedetto3.jpg

The f-holes preclude effective ladder bracing, but some sort of lattice might be worth exploring. I'm thinking mandolin bracing here, not guitar.

[Paul Hostetter]

Other ideas:

http://www.lutherie.net/benedetto2.jpg

http://www.lutherie.net/benedetto4.jpg

[billhay4]

Benedetto's book will have the bracing pattern. I forget what it is and don't have the book before me right now.
Bill

[Bill Snyder]

Wouldn't Benidito's bracing plan be for an arched top instrument? Magnus wants to build a flat top.

[Paul Hostetter]

Right, but X-bracing in archtop instruments merely mimics and redeploys X-bracing as used much earlier in flattop instruments. The principle serves each style of top in a similar way. X-bracing a flat top makes sense, even if it's not really copying the engineering of a Benedetto archtop. The typical way of bracing an earlier archtop was longitudinal tone bars, as seen in early Gibsons.

http://www.lutherie.net/benedetto5.jpg

My only suggestion to Magnus, if he's certain about doing a flattop mandolin based on this aesthetic idea, is to radius and dome the top well. A simple flat top isn't going to be very strong.

[Magnus Geijer]

That's odd, I could have sworn I replied to this.

Anyway, thank you so much Paul, that's exactly the sort of thing I was looking for. I particularly like the second to last, double x design.

Thanks,

Magnus

[Magnus Geijer]

I found this thread and thought I'd post the result. The mandolin still isn't finished, but it's sibling, which I built for my sibling, as it were, is complete and now confusing the snot out of my sister's local guitar shop.

Again, thank you kindly for the suggestions.

/Magnus

[Paul Hostetter]

Bravo! Be sure and post some images of the mandolin when you get it finished.