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When I’m doing a cutaway I understand there must be extra length to accommodate it on that side. My question is:

How does this affect the geometry of the 2 sides? The curve from the back will still break at the same point, so I suppose it is basically flat through these areas...yes?

I think using my dishes will also even things out.

My second question is, is it viable to cut the soundport prebend, or will this weaken the side and encourage a break when bending?

Please correct me if I’m wrong



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If I'm not mistaken, it's actually the non cut side that is longer, as it needs to cross the centreline at the block to meet the FB edge, or longer, depending on how you're approaching it...

There is usually a distinct swell in depth at the cutaway. As the cut bends in, it needs to get deeper, as it's coming in towards the center of the dish, then less deep as it goes back out towards the edge. If you're using the method where you add a block to your mold matching the cutaway, I'd suggest using your dish to make a proper profile, otherwise you may be in for more dish sanding than you think...

But once you've done that, just line up the waist right and you're gold...

Here’s how it measured out for me.
On the cutaway side it was 28 5/8” from the bottom.
On the non cut away it was 27.5”



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27.5 from where to where?

I think what might be twigging my brain, is not that it's actually longer, but not to cut the non cut side at the centreline, it needs to extend across to meet the cutaway corner, however you choose to do it...

I'm confused about what you are asking. Are you asking about the the lengths of the sides from the centerline at the tail to the centerline at the neck, or are you asking about adding a bulge to the bottom of the side profile through the cutaway section of the treble side?

The only soundport I've done was on the guitar I built in a course and it was cut into the side after the body was a closed up box. If I was going to do another one, that's how I would do it again. I would have your same concern about pre-cutting it creating risks for bending.

That's nice looking wood. What is it?

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The wood is sapele

I think as I’ve read a few posts and straitened it out on my mind I have less of a concern... I was concerned that the back, or top really, had a pre radius, however because the cutaway needed extra length to make it around the shape and to the center I was afraid the slope(s) would start in non parallel places.
The remedy, I think, is to just keep the extra length the same width as the “flat” area of the side through the cutaway.
I realize this is probably clear as mud.


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Really suggest making a template from the mold with a washer and tape/cardboard as outlined in other threads.

If you don't thicken the sides in the area the cutaway goes towards center of dish, you end up having to sand the rest of the rims down to meet the low point, which can be a real chore. Look at the spot where I put the sanding block, how there's a bulge there...

I’ll search for that thread.
What is a washer for? Guess the thread would explain it.


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It was mentioned in this recent thread: https://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=51545

_________________
Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter