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top plate joining and wood grain question
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=43821		 Page 1 of 1
Author:  patch [ Thu Jul 17, 2014 1:49 am ]
Post subject:  top plate joining and wood grain question
hi, i tried the search but with no luck.

my question is this. when joining top plates and the grain is tighter on one side of the book match than the other, which side would you join? is it better to join the tighter grain together or the wider? does it matter?

thanks!
Author:  Colin North [ Thu Jul 17, 2014 2:19 am ]
Post subject:  Re: top plate joining and wood grain question
Usually the tighter grain is jointed together in the middle of the top.
The wider grain spacing tends to be less stiff/more flexible so is left at the outside of the top.
Author:  DennisK [ Thu Jul 17, 2014 3:08 am ]
Post subject:  Re: top plate joining and wood grain question
Colin North wrote:
The wider grain spacing tends to be less stiff/more flexible so is left at the outside of the top.

Says who? Or have you done any tests yourself, and verified that the results weren't skewed by runout variation across the board? I've always heard that grain spacing has no consistent effect on stiffness.

I usually join with the tight grain in the center just because I think it looks better, but I'd have no fear doing it the other way. And if there's more runout on one side than the other, then put it toward the outside.
Author:  Michael.N. [ Thu Jul 17, 2014 5:02 am ]
Post subject:  Re: top plate joining and wood grain question
Not sure it looks any better, just that our eyes are more accustomed to seeing the tight grain in the centre. If I get a better reflection by placing the wide grain in the centre, then I'll do that. I haven't done it many times, perhaps on 4 or 5 occasions.
Author:  Colin North [ Thu Jul 17, 2014 5:04 am ]
Post subject:  Re: top plate joining and wood grain question
Hi Dennis, sorry I was not more specific in my reply.
I have also heard that grain spacing has not necessarily any correlation with stiffness, especially longitudinal stiffness.
Here we are talking about "a" top varying in grain width across the two halves.
In most of the small sample of 40 or so tops I own or have used, the ones where the grain spacing varies from one side to the other do so because the wood goes off quarter at the wider grained side.
I have also seen pictures of many tops advertised where the grain width varies across the boards for the same reason, so this seems to be fairly common.
The same wood, cut perfectly on the quarter, unless I am severely mistaken, tends to be stiffer across the grain than if it is cut off quarter.
As an extreme, I bought some (now replaced) "AAA" cedar tops that arrived with the grain around 40/45 degrees off quarter that that are so flexible cross grain that they can be rolled virtually into a tube cross grain without breaking, totally unlike their very well quartered replacements, all from the same tree (yes, I know you can get widely varying wood properties from the same tree)
So with my tops, I joint my tighter grained edges in the middle as I look for more flexibility at the edges, especially of the lower bout, but my apologies for not explaining my reasoning for suggesting this in my original post.
I admit it is also cosmetic.
I must admit, I have not seen many, if any, pictures of guitars with tops jointed with wide grain in the middle and tight grain at the edges. (here we go, flood of post of pics with the wider grain in the middle laughing6-hehe )
But hey, if that floats your boat, why not.
Author:  DennisK [ Thu Jul 17, 2014 5:29 am ]
Post subject:  Re: top plate joining and wood grain question
Ah, so you were speaking of cross grain stiffness :) True indeed that grain angle has a huge effect on that in softwoods. But then there is the question... does cross grain stiffness of the plate have more tonal impact at the perimeter or in the center? And is maximum cross grain stiffness even a desirable property? I haven't come to any conclusions on that yet.
Author:  Colin North [ Thu Jul 17, 2014 5:47 am ]
Post subject:  Re: top plate joining and wood grain question
Yes, but the string pull forces are at the center and would require a thicker and hence heavier top to resist that?
Author:  Michael.N. [ Thu Jul 17, 2014 6:06 am ]
Post subject:  Re: top plate joining and wood grain question
Here's one Colin (although you'll struggle to see it).

https://www.youtube.com/watch?v=dAhCi0XaQD0


Not only that but NO bracing:

Image


I broke all the rules, or rather Torres did.
Author:  Nick Royle [ Thu Jul 17, 2014 6:46 am ]
Post subject:  Re: top plate joining and wood grain question
Michael.N. wrote:
Not only that but NO bracing:


Did you just leave the lower bout of the top thicker than you usually would, Michael?
Author:  Michael.N. [ Thu Jul 17, 2014 6:55 am ]
Post subject:  Re: top plate joining and wood grain question
Well it is a small instrument but yes, about 0.5 mm thicker than my average.
Author:  DennisK [ Thu Jul 17, 2014 6:58 am ]
Post subject:  Re: top plate joining and wood grain question
Colin North wrote:
Yes, but the string pull forces are at the center and would require a thicker and hence heavier top to resist that?

But the bridge would "bridge" the floppy area, forcing it to bend all together anyway, and then the higher cross grain stiffness toward the outside would help continue to spread the stress outward without the aid of major bracing stiffness like you have in the center. At least in theory. I need to go dig it up, but I remember a post by Alan Carruth that cross grain stiffness doesn't seem to resist cold creep very well, so in terms of structural strength, you need to focus on long grain stiffness anyway.

And aside from effect on total mass by being able to take it thinner, there's the question of vibrational effect of different stiffness distribution. And that's what I was mainly talking about in my previous post. The guitar Michael posted is a great example of taking it to the extreme. The long grain to cross grain stiffness ratio should have a major effect on the relationship of the long dipole and cross dipole mode frequencies there. And the part of the plate outside the wings of the bridge will have the most impact, because the bridge stiffness is so much higher than the plate's cross grain stiffness in the middle either way.

I built one of those fanless Torres guitars as well, and used perfectly quartered redwood, and it sounds great. I have plans to build another with a 45 degree super-flop top, so that will make a good comparison of extremes.
Author:  Colin North [ Thu Jul 17, 2014 7:39 am ]
Post subject:  Re: top plate joining and wood grain question
Thanks for posting that Michael, absolutely beautiful sounding guitar and very well played.
I watched it just the other day, probably from a Delcamp link.
If I'm not mistaken, that is a small Torres style classical, short scale length, lower tuning than A=440?
I see you built thicker than your "normal", it would be interesting to know if the top is an even thickness, or thins towards the edges as seems to be not unusual in classicals (and not uncommon in SS's either)?
Actually, it's not the first guitar I have seen without any lower bout bracing, classical and SS.

"They" say that "rules" "are made to be broken.
OK, I can see the 'wisdom' in that, and I am not really one to "follow the crowd" unquestioningly.
But I would hesitate to recommend going against what seems to be "conventional" build techniques to someone who has to ask which way round to joint a plate.
None of the guitar making books I own, or have read, recommend putting the tighter grain to the outside.
Those that do mention it, suggest putting it to the middle.
Or is that the final secret that the Master, as he fades away, whispers in the apprentice's ear?

Sorry if I'm talking out of turn here, but this forum tends to lean towards helping guys out if they have questions, that's all I'm trying to do here. Why do I feel kind of harangued for that?

Dennis. I also look forward to seeing your report back on building guitars cross grain floppy in the middle and stiff at the sides now.
Author:  Colin North [ Thu Jul 17, 2014 7:40 am ]
Post subject:  Re: top plate joining and wood grain question
Double post.
Author:  Colin North [ Thu Jul 17, 2014 7:56 am ]
Post subject:  Re: top plate joining and wood grain question
DennisK wrote:
...................... I have plans to build another with a 45 degree super-flop top, so that will make a good comparison of extremes.

I can definitely help you out there if cedar's OK?
Author:  Nick Royle [ Thu Jul 17, 2014 8:31 am ]
Post subject:  Re: top plate joining and wood grain question
Colin North wrote:
None of the guitar making books I own, or have read, recommend putting the tighter grain to the outside.
Those that do mention it, suggest putting it to the middle.
Or is that the final secret that the Master, as he fades away, whispers in the apprentice's ear?


A very experienced guitarist and guitar-maker I've spoken to said something to the effect of, "hmm, I've heard some lovely guitars that had the wide grain in the middle. That can be very nice".

My second hand 2 pence! :)
Author:  DennisK [ Thu Jul 17, 2014 8:38 am ]
Post subject:  Re: top plate joining and wood grain question
Sorry Colin. I do tend to get carried away pondering every little detail of guitar design...

And I'll get back to you on the cedar whenever I make up my mind whether I prefer high or low cross grain stiffness. I have plenty of 45 degree redwood for experimenting, but if the conclusion is that I prefer low cross grain stiffness, then I'll start collecting more 45 degree wood :)
Author:  mqbernardo [ Thu Jul 17, 2014 9:45 am ]
Post subject:  Re: top plate joining and wood grain question
DennisK wrote:
Colin North wrote:
The wider grain spacing tends to be less stiff/more flexible so is left at the outside of the top.

Says who? Or have you done any tests yourself, and verified that the results weren't skewed by runout variation across the board? I've always heard that grain spacing has no consistent effect on stiffness.

I usually join with the tight grain in the center just because I think it looks better, but I'd have no fear doing it the other way. And if there's more runout on one side than the other, then put it toward the outside.


Hi Dennis and Collin, nice thread! Please hear me thinking out loud here for a while.
Latewood (in conifers) has the cross section of tracheids much smaller than in earlywood, and late wood tracheids have a much thicker walls than earlywood and are all neatly packed together, right? Latewood tracheids also have an higher percentage of lignin on the walls than earlywood. After all, growth conditions tend to be optimum in spring and by late summer trees are mostly busy gaining back some "muscle" after inducing on all that spring sap making frenzy.
Regarding the few articles i´ve read on the subject, this translates in latewood being denser than earlywood. To which extent, it depends on species, conditions of growth, position of the tracheids on the tree and so on, but the trend is always present.
As the tighter grain has a significantly higher percentage of latewood tracheids than wider grain, it should also have a significantly higher density than wider grain, which should correlate with higher stiffness. So, even if tighter grain is by no means a guarantee of stiffer wood per se (if we´re comparing wood from different sources), tighter grain = higher long grain stiffness if we´re talking about a particular piece of wood, provided there´s the same amount of runout on both parts. At least that´s he sense i make of it.
Author:  Clay S. [ Thu Jul 17, 2014 9:49 am ]
Post subject:  Re: top plate joining and wood grain question
I use a fair amount of Engelmann, some of which has a spiral twist, where the runout will vary greatly from edge to edge. I like to join the edges with the least runout. Sometimes it is the wider grain and sometimes it is the tighter. I do this for cosmetic considerations. For steel strings I think the top wood properties are less critical than for classicals.
As Colin said, generally the tighter grain is joined in the center of the top.
Author:  Colin North [ Thu Jul 17, 2014 10:16 am ]
Post subject:  Re: top plate joining and wood grain question
Don't want to derail the topic, but just out of interest to those who may not have seen it, some of my early pre-guitar making reading and influences was from Frank Ford's frets.com.
http://www.frets.com/FretsPages/Musician/Guitar/ToneWoods/tonewoods1.html
Have a look especially at the soundboard on the
Quote:
exceptionally good sounding
mandolin at the bottom.
Author:  JasonM [ Thu Jul 17, 2014 11:01 am ]
Post subject:  Re: top plate joining and wood grain question
Put the stronger silking to the center, as it will have the least runout. May or may not be the narrow grain. Try to get silking under the bridge, to minimize the chance of a bridge pulling up due to being attached to run-out fibres. Also should be stiffer, as silking shows it's perfectly quareted there.
Author:  Tom West [ Thu Jul 17, 2014 3:27 pm ]
Post subject:  Re: top plate joining and wood grain question
Clay S. wrote:
I use a fair amount of Engelmann, some of which has a spiral twist, where the runout will vary greatly from edge to edge. I like to join the edges with the least runout. Sometimes it is the wider grain and sometimes it is the tighter. I do this for cosmetic considerations. For steel strings I think the top wood properties are less critical than for classicals.
As Colin said, generally the tighter grain is joined in the center of the top.


This is also my approach, I detest the runout look at the center joint.
Tom
Author:  patch [ Fri Jul 18, 2014 7:26 pm ]
Post subject:  Re: top plate joining and wood grain question
thanks for all the replies! lots to digest here.
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