Archtop arching

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Dominic
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Archtop arching

Post by Dominic » Thu Jan 20, 2011 11:13 pm

Hey carved top makers, I have been thinking about the arching on archtops and wonder what people are using. My first archtop I just followed Benedetto's arching templates as close as I could and used parallel bracing and loved the sound of the finished guitar. A nice fat sound on the bass strings, almost like it had been amplified (not like that plonky jazz sound which does not appeal to me at all) and nice trebles. A mate has borrowed it to do some recording but he wants me to make him one when I get back which led me to ponder my options. I was wondering what others do with their arching and how it impacts on the sound.
Do you guys follow Benedetto’s templates (assuming you are using his plans) and what might be the result if you made the arch a little higher or a little lower or a little rounder or a little more peaked? In flat tops a flatter radius would give more bass but an archtop is a different thing altogether and I would imagine a flatter arch would hold up less well to the downward force of the strings and so would perhaps need to be bit thicker.
Anyone mucked around with these parameters yet and what are your thoughts on it?
Cheers
Dom
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but you can't bomb the world to peace!

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matthew
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Re: Archtop arching

Post by matthew » Fri Jan 21, 2011 12:06 am

i think the curtate cycloid arching principle has merit. Even rate of change of curve right across the arch.

Image

my goodness that looks like someone i know.

Image

you can get programs that will draw them for you for given width and arch height and so on.

Mistake I made on my first bass top was to bring the arch up from the edge too soon. makes the whole center much too stiff and affects the bass response/darkness. Second one I used cycloids and it was much better.

Still wondering about the shape of the long arch ...

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sebastiaan56
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Re: Archtop arching

Post by sebastiaan56 » Fri Jan 21, 2011 5:52 am

Have you read the research papers here Matthew? http://www.violin.uk.com/ (see the research tab). Im still digesting and dont pretend to understand it all but the science looks very solid.
make mine fifths........

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Re: Archtop arching

Post by matthew » Fri Jan 21, 2011 6:53 am

I've not seen those yet but I did follow a HUGE thread on Maestronet and it seemed to make sense. I like it because it is a mathematical way of describing a curve, and a good point to start.

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Dominic
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Re: Archtop arching

Post by Dominic » Fri Jan 21, 2011 11:51 am

Thanks Matthew, do you mean you made the top curve too steep out near the edge on your first one? So the centre section ended up flatter?
I found an interesting post from Graham McDonald on a different forum where he mentioned that the mando guys seem far more interested in plate thickness while the violin guys are interested of curvature. The archtop guitar is quite a new invention relative to these so perhaps we have a lot more to explore and learn before we find its true potential. Like arch height and how an oval hole works which Bob B discusses in his book.
I just read that a flatter curve on the long axis with a steeper transition near the neck and tail blocks gives a warmer darker sound which sounds like something to muck around with also.
I really like thinking about all these curves and how they join up, similar things to when I was making surfboards although they have far more complex interactions still. They are all curve and everyone one is important to how well the boards goes.
Cheers
Dom
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matthew
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Re: Archtop arching

Post by matthew » Fri Jan 21, 2011 12:23 pm

yeah the flat long arch does result in a warm sound because i suppose its less stiff in one direction, but it is also less strong, so you have to make the top thicker to compensate or it will sink over time under string pressure, but a thicker top is more stiff, which results in a brighter sound, cancelling out the intent in the first place. So maybe If we make the long arch taller and slightly convex, we can make the belly thinner because that will result in a darker sound, but then a convex long arch is stiffer, resulting in a brighter sound, cancelling out the intent in the first place!

Humbling, really, if you get it right.

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Re: Archtop arching

Post by Puff » Fri Jan 21, 2011 5:25 pm

Just my opinionated self here.
An archtop without recurve is a radiused flat top.
The longitudinal crown is under the bridge.
From memory the people at Seagull did quite a bit of study into increased guitar top curvature and concluded that any arching north of what ended the effective resonating surface - be it sound hole or full width brace, was of no consequence.
The argument for continuing the lateral crown northwards in instruments with FF holes or offset or side sound ports is a structural one as it dissuades the area between bridge and neck block from caving in. Effectively a free longitudinal brace.

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Re: Archtop arching

Post by matthew » Fri Jan 21, 2011 11:05 pm

absolutely right. An archtop without recurve cannot really resonate, like an eggshell cannot resonate.

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duh Padma
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Re: Archtop arching

Post by duh Padma » Sun Jan 23, 2011 4:41 pm

Yo, Dom

Un like flat toppers, there ain't all that much out there about arch top variations.

You might find logging on to http://www.luthierforum.comand following the "All Cedar Arch Top Build Along" threads. Yes me said threads cuz there are about a half dozen or so builders all building concurrently the same (Benedetto) design and posting independently from one another. The build is being facilitated by Steve Stevens. Now here would be and interesting series of builds to keep an eye on if your into arch tops. Although they are using Benedettos plans and are all using cedar from the same tree, I would think, as variations from builder to builder slip in and are documented, some interesting resulting data might be comeing forth soon.

As for me, well me don't really pay much attention to this that or the other in building, being more of a scribe, cut and fit guy, In fact me calipers fell behind the bench so far way back long ago me don 't think I would be able to recognize them unless me blasted back there with a hundred lbs of air.

Other than a given 1/4 or there abouts under the bridge and about 1/8 in the recurve, me don't pay much attention at all to the shaping of the plates which vary from a 1/2 to 1 inch. and much prefer to just carve the sucker by instinct. Ya some sound better than others. But thats they way it is. Always some better n others.

blessings
duh
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Dominic
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Re: Archtop arching

Post by Dominic » Sun Jan 23, 2011 8:33 pm

Thanks Padma, I like the cut of your jib. I must admit with the flat top brace carving I have done I usually start with good intentions of keeping to measurements and knowing where I end up but I usually just go at it and trust my intinct in the end. With the first archtop I made recently I planned it out using the curves from Benedettos book but then just carved away to get the curves that i thought felt right and to get them to blend into each other in a pleasing way. In surfboard making some curves are sexy and some are not and I always found the sexy curves work best and were more fun to make. I applied the same principle to the archtop and I liked the result but not having even played one before have no base for judging.
Anyway, thanks for the link, I'll check it out and see what the various builders get up to.
Cheers
Dom
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ozziebluesman
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Re: Archtop arching

Post by ozziebluesman » Sun Jan 23, 2011 8:39 pm

I'm about to venture into my first archtop.
Thanks for the link Padma.
There sure is some good info there!
Cheers
Alan
"Play to express, not to impress"

Alan Hamley

http://www.hamleyfineguitars.com/

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