Newbie luthier questions - flat vs domed tops

Construction and repair of Classical Guitar and related instruments
mChavez
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Newbie luthier questions - flat vs domed tops

Post by mChavez » Tue Jul 04, 2017 7:14 pm

Hello all,

I am an absolute beginner luthier looking for some advice about building guitars and this seems to be just the right forum for it.

I have recently completed my first guitar build (a wee steel string parlour) and I am looking to attempt a couple more guitars next year while I am learning the craft. After reviewing my first build, I have noted that almost all of the problems that I have encountered were caused by doming the soundboard and the back, and I am tempted to build perfectly flat tops & backs for the next few guitars, at least until my skills get a bit better (before the first guitar I never even held a chisel in my hands) and until I build up more tools, jigs and equipment.

Does anybody on this forum build their tops flat, and if so, what is your experience with them? How do they stand up to humidity changes? Did you ever have soundboards cracking?

From what I have read online, the flat top's only potential issue might be cracking in extreme humidity changes. Sound wise, domed tops should have more highs (as they are more rigid), but I guess that the extra bass of a flat top will not do the parlours any damage.
While the humidity at home stays around 40-45% in winter and 55-60% in summer, a couple of my future builds are likely to end up with friends in continental European climate where humidity changes are more dramatic.

Another question that I would like to hear some opinions on is how much tension can be loaded onto a classical bridge, as opposed to the through-the-soundboard construction. I like the idea of fan bracing, but I think it will clash with a pin bridge as the bracing will have to be based round the string holes.

Thank you for your help.

Bruno Piancatelli
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Re: Newbie luthier questions - flat vs domed tops

Post by Bruno Piancatelli » Tue Jul 04, 2017 11:06 pm

I think the question is, why would you want the top to be flat in the first place? there shouldn´t be much trouble with doming if you have the right jigs, like solera or radius dish.

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Michael.N.
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Re: Newbie luthier questions - flat vs domed tops

Post by Michael.N. » Wed Jul 05, 2017 6:53 am

True flat tops tend to go a little concave over time, due to humidity swings. Not that it matters. I've seen countless romantic guitars and all of them were built with a flat soundboard, even some of the larger models. To be honest I'm not sure they are any more susceptible to cracking than modern domed guitars. Of course they tend to be much older and have often been abused, you would expect them to have more issues.
Not sure I agree on the tone and better 'highs' but we'll leave that one.
You can do a pin bridge with fan bracing (Panormo did). You do need to be very accurate if you don't want a pin going through a fan brace though. Plug in neck will help with this.
Historicalguitars.

mChavez
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Re: Newbie luthier questions - flat vs domed tops

Post by mChavez » Wed Jul 05, 2017 7:11 pm

Thanks.

Bruno, I found that doming was very easy even just by pre-shaping braces. The difficulties I faced were in matching of the bridge to the domed top and cutting the binding channels, plus I have some concerns about the quality of the joint between domed soundboard and the ribs.

As I have mentioned, I have next to zero woodworking experience, so I am considering the flat top for the next couple of builds just to keep things simple.

printer2
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Re: Newbie luthier questions - flat vs domed tops

Post by printer2 » Wed Jul 05, 2017 8:41 pm

You could build it flat but dry out your wood before hand and it will dome with the added humidity. Hey, there is an experiment begging me to build another guitar.
Fred

Pat Foster
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Re: Newbie luthier questions - flat vs domed tops

Post by Pat Foster » Wed Jul 05, 2017 10:18 pm

Hi, Fred!
printer2 wrote:
Wed Jul 05, 2017 8:41 pm
You could build it flat but dry out your wood before hand and it will dome with the added humidity. Hey, there is an experiment begging me to build another guitar.
There's a top-drawer builder in our area who does something like that, bringing his tops down to something like 4 or 5% EMC, braces them, then brings them back up to 8% EMC before gluing them to the ribs. He's been building for 40 years and has a long waiting list, so I believe in his methods.

Pat

bftobin
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Re: Newbie luthier questions - flat vs domed tops

Post by bftobin » Thu Jul 06, 2017 2:13 am

I've seen some cases of a flat top but an arch on the bottom of the bridge to raise the top height in that area

vesa
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Re: Newbie luthier questions - flat vs domed tops

Post by vesa » Thu Jul 06, 2017 6:13 pm

Hi mChavez!
I can´t quite understand the reason why you want to build flat, I think the problems you mention are quite easy to solve,
there is a lot of good advice available in these sites, in other forums, Courtnall book etc.
I´m starting my fourth now, so also a newbe. To begin with I used quite long time to build a proper solera,
which really was a good investment and makes my life easier when joining neck, top, sides and back.
I have followed Courtnall´s advice and left ca. 2 cm flat between the edge (sides) and where the dish begins,
it makes joining sides to the top easier because you have 90° angle all the way round.
And I followed advice from these sites about the neck angle, it has been spot on in all my builds.
Marshall Dixon wrote:
you can tape a piece of sandpaper to the top
I do it that way and tape a A4 paper between the sandpaper and the top to protect the top and vacuum the after every 30 - 40 strokes.
Works for me.
I don´t understand the problem with the bindings?
Vesa Kuokkanen

Antonio Marin nr. 813 1995 (Bouchet)
Vesa Kuokkanen 2016

RedCliff
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Re: Newbie luthier questions - flat vs domed tops

Post by RedCliff » Thu Jul 06, 2017 8:00 pm

I have and do build both flat and domed. Both work. Haven't yet noticed any difference in the likelihood to crack or deform. Yes, a dome is inherently stronger, so it can be built lighter. Lighter doesn't always sound better, although it may sound louder. Lots of people have built flat and made pretty good guitars.

Problem you face in asking this question on a forum is that the majority of people build with a dome of some kind. They aren't likely to a) know how to build flat or to compensate for building flat unless they have invested serious time in doing so, and b) they have considerable investment in terms of time, money, prestige, reputation in saying that dome is better - otherwise why would you buy their domed guitars?

I'm not knocking domed guitars, I also build them, they are great, but so can flat tops be. There are advantages to both. You are right, cutting binding channels is much easier with flat tops if you want perfectly vertical ledges. Perfectly fine way to go to build up your skills. If you are worried about rapid moisture changes put a couple of coats of shellac wash on the inside of the top before you close the lid. Doesn't stop the moisture loss but it might slow it down. I challenge anyone to be able to hear the difference. If you can still find one Jim Williams Guitar Making Manual gives a good plan for a flat top.
Giles Ratcliffe
Sheffield
England

printer2
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Re: Newbie luthier questions - flat vs domed tops

Post by printer2 » Fri Jul 07, 2017 12:56 pm

Pat Foster wrote:
Wed Jul 05, 2017 10:18 pm
Hi, Fred!
printer2 wrote:
Wed Jul 05, 2017 8:41 pm
You could build it flat but dry out your wood before hand and it will dome with the added humidity. Hey, there is an experiment begging me to build another guitar.
There's a top-drawer builder in our area who does something like that, bringing his tops down to something like 4 or 5% EMC, braces them, then brings them back up to 8% EMC before gluing them to the ribs. He's been building for 40 years and has a long waiting list, so I believe in his methods.

Pat
You mean there are two top drawer builders in your town?
Fred

mChavez
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Re: Newbie luthier questions - flat vs domed tops

Post by mChavez » Fri Jul 07, 2017 5:41 pm

Apologies All - I did not realise that flat vs dome was such a heated topic and I never intended to cause any arguments here.

I would be very grateful for any tips on building flat and compensating for it. My line of thought was more along the lines of steel-strung romantic guitars. Any help with plans would also be greatly appreciated.
In terms of raising the bridge height - what are the drawbacks of angling the neck slightly towards the soundboard (i.e. reducing the 180* angle)?
I understand that bridge height affects the sound, but would neck angle affect it too? All this assuming that the scale length is kept true after the angle reduction.

Marshall, Redcliff, all posts are very helpful for me in terms of gathering the information and I am sure that no offence was intended by anyone.

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GeoffB
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Re: Newbie luthier questions - flat vs domed tops

Post by GeoffB » Sat Jul 08, 2017 11:37 am

Note: Some posts have been removed from this thread at the poster's own request, so as not to distract from the original question.
Classical Guitar Forum.

"Experience is something you don't get until just after you need it." - Steven Wright

ddray
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Re: Newbie luthier questions - flat vs domed tops

Post by ddray » Sat Jul 08, 2017 12:37 pm

Yeah I'm finding that just about any topic can become heated on these Internet forums. Er fora.

John higgon
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Re: Newbie luthier questions - flat vs domed tops

Post by John higgon » Thu Jul 13, 2017 5:04 pm

I don't see a problem with building flat tops whilst you are developing your woodworking skills. There are allegedly a couple of advantages to domed tops (more resistant to humidity changes, and the additional tension introduced by the dome helps with aspects of the sound, as I understand it). Whether it makes a great deal of difference, especially on your early guitars, is debatable. Domed tops aren't that difficult, though. You just need to carve a suitable recess into the lower bout of the solera, but not right up to the edge od the plantilla. Cutting the binding recess is therefore not affected by any curve at the edge of the top. The underside of the bridge is a bit of a pain, but you can use sandpaper and the dip in your solera to make a complementary curve on a piece of wood, then glue some sandpaper on that to give you a sanding jig that will approximate the curve you are looking for on the underside of the bridge. I've never tried putting sandpaper on the top and doing it that way. Some people on this forum use this method and it seems to work for them. The risk, as I see it, is that any pressure on the domed soundboard will result in a temporary deflection, so the resulting curve may not be as pronounced as you are aiming for. Anyway, just have fun and try various methods until you find one that works well for you!

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