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  #16  
Old 12-06-2015, 06:43 PM
dekutree64 dekutree64 is offline
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Originally Posted by rogthefrog View Post
RC tonewoods indicated this student-grade top isn't as stiff as they would like, and it does feel very floppy (though I've only ever handled one other top, the Italian spruce top for my harp guitar, which may have been chosen for extra stiffness to handle all those strings).
Harp guitar? I love harp guitars! I shall be your friend throughout your quest

By floppy, do you mean across the grain? Usually that comes from being off quarter (look at the endgrain and see if the lines are angled, rather than perfectly vertical). Being cut at 45 degrees will make softwoods ridiculously flexible across the grain. Then as you get toward perfectly flatsawn, it stiffens back up again. Happens because the cells are square. Orienting them as diamonds lets them deform easily. Hardwoods have round cells, so their cross grain stiffness doesn't really change with how they're sawn.

My present belief is that the plate's cross grain stiffness doesn't really matter that much. Long grain stiffness is what's important for survival. Cedar is a lot less stiff than spruce, but a lot lower density too, so you just leave it thicker and everything works out. If the top has a lot of runout, that could be why it was graded low. It is possible for a tree to grow with inherently bad stiffness to weight ratio along the grain, but it's hard to judge that on rough sawn tops without actually measuring the density and doing deflection testing.

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Next up: same thing, with the back. If the back works out well, I'm feeling bold and will attempt to put in a strip of contrasting wood across the joint to pretty it up. The back and sides are very white birch and I will almost certainly stain them darker.
A solid wood backstrip inlaid at half the thickness of the back is actually a good reinforcement for the center seam. I use them as a chicken exit when I have back woods that just refuse to joint perfectly nomatter what I do

My guess on the mystery block is ipe.
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  #17  
Old 12-06-2015, 06:54 PM
rogthefrog rogthefrog is offline
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Ipe makes sense. According to

http://www.wood-database.com/lumber-...hardwoods/ipe/ its density is 1,100 kg / m^3, and I calculated my block's density is 1,030 kg / m^3 (see previous post for Excel). It also looks just like the picture on Wood Database.

Good eye!

That kinda answers my next question. Wood Database says it's hard to work and hard to glue, so it may not be ideal for making laminated end/neck blocks (I was thinking mahogany/mystery laminations). It may also be too heavy. Any thoughts?
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  #18  
Old 12-06-2015, 07:53 PM
rogthefrog rogthefrog is offline
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Originally Posted by dekutree64 View Post
Harp guitar? I love harp guitars! I shall be your friend throughout your quest
Here's the thread from when I received it.

http://www.acousticguitarforum.com/f...rt+harp+guitar
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  #19  
Old 12-06-2015, 10:32 PM
dekutree64 dekutree64 is offline
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Here's the thread from when I received it.

http://www.acousticguitarforum.com/f...rt+harp+guitar
Oh! I thought you meant you had a harp guitar soundboard stashed with plans to build one after doing this first guitar as a training mission. But I guess there's not much incentive to build one when you've got that beauty! Funny, I commented on that thread, but had forgotten about it.

As for ipe as head/tail blocks... I'd say no, just because it's so hard to work. If you're doing a butt joint bolt-on, that might not be a problem. Then it just depends on whether you care about the total weight of the guitar.
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  #20  
Old 12-07-2015, 12:24 AM
rogthefrog rogthefrog is offline
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Oh! I thought you meant you had a harp guitar soundboard stashed with plans to build one after doing this first guitar as a training mission.
Ha. Given how painful HG builds appear to be, even to a seasoned builder, I doubt I'll ever make one. But who knows, right?
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  #21  
Old 12-07-2015, 03:01 PM
difalkner difalkner is offline
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Come on, pix or it didn't happen!
LOL! Then we'll have to go with 'it didn't happen' until I string it up.
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  #22  
Old 12-08-2015, 05:05 PM
rogthefrog rogthefrog is offline
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The birch back warped a fair bit so it spent some quality time in shackles to think about its behavior.



After 48 hours indoors in its corset, it was flat again, so I jointed it and joined it on the joining board:



Tomorrow or Thursday I'll thickness it, cut the top and back shapes, and inlay a center strip on the back.
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Last edited by rogthefrog; 12-08-2015 at 05:13 PM. Reason: GIANT IMAGES OMG
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  #23  
Old 12-08-2015, 07:38 PM
Ned Milburn Ned Milburn is offline
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Originally Posted by rogthefrog View Post
Ipe makes sense. According to

http://www.wood-database.com/lumber-...hardwoods/ipe/ its density is 1,100 kg / m^3, and I calculated my block's density is 1,030 kg / m^3 (see previous post for Excel). It also looks just like the picture on Wood Database.

Good eye!

That kinda answers my next question. Wood Database says it's hard to work and hard to glue, so it may not be ideal for making laminated end/neck blocks (I was thinking mahogany/mystery laminations). It may also be too heavy. Any thoughts?
Mahogany: Shrinkage: Radial: 2.9%, Tangential: 4.3%, Volumetric: 7.5%, T/R Ratio: 1.5

Ipe: Shrinkage: Radial: 5.9%, Tangential: 7.2%, Volumetric: 12.4%, T/R Ratio: 1.2

There are reasons certain woods have been chosen as standard woods for guitar building. When people refer to "stability" of mahogany, part of the meaning is its low expansion/contraction rate.
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  #24  
Old 12-08-2015, 10:28 PM
maxtheaxe maxtheaxe is offline
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That really looks like walnut to me...one of the darker ones like Circassian, et al... hard to say from pics.

The only other wood that reminds me of is a type of African mahogany that has that chocolate color, tends to be more 'wild-grained' and is denser and heavier than S. American hog. I used to see it sometimes on vintage boats, as various kinds of trim and I had a transom rub-rail on my old power boat that was made from it.
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  #25  
Old 12-09-2015, 12:30 AM
rogthefrog rogthefrog is offline
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Originally Posted by maxtheaxe View Post
That really looks like walnut to me...one of the darker ones like Circassian, et al... hard to say from pics.

The only other wood that reminds me of is a type of African mahogany that has that chocolate color, tends to be more 'wild-grained' and is denser and heavier than S. American hog. I used to see it sometimes on vintage boats, as various kinds of trim and I had a transom rub-rail on my old power boat that was made from it.
Thanks. I'm pretty sure it's ipe. Definitely not walnut--it's about twice as heavy. Pretty crazy how heavy it is!
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  #26  
Old 12-09-2015, 12:31 AM
rogthefrog rogthefrog is offline
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Originally Posted by Ned Milburn View Post
Mahogany: Shrinkage: Radial: 2.9%, Tangential: 4.3%, Volumetric: 7.5%, T/R Ratio: 1.5

Ipe: Shrinkage: Radial: 5.9%, Tangential: 7.2%, Volumetric: 12.4%, T/R Ratio: 1.2

There are reasons certain woods have been chosen as standard woods for guitar building. When people refer to "stability" of mahogany, part of the meaning is its low expansion/contraction rate.
Interesting! I thought ipe was used extensively for outdoor decking. With that kind of expansion and shrinkage, one would have to leave a fair bit of room around each board during installation.
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  #27  
Old 12-30-2015, 07:22 PM
rogthefrog rogthefrog is offline
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I picked up the build today after a short break, during which I learned about plate thicknessing.

This afternoon I thicknessed the top to my satisfaction, though it feels a little floppy. I knew that going in, as it's a bargain-basement / "student grade" top that was graded that way because it's not very stiff. I've been considering making this a nylon string, and the floppiness may make that necessary.

Once that was done, I thicknessed the back, and ran into some trouble there. One of the halves had terrible tearout, even though my planes are very sharp; but that was taken care of with aggressive sanding. Thankfully the plate was thick enough for that and it looks fine.

Then I routed a channel for the back strip, and screwed up a few times. The way I held the router moved the micro adjustment wheel and I routed too deep, going all the way through in a couple places. Then my straightedge slipped and the channel edges are suboptimal. I wasn't sure whether to use purfling around the strip, and now I have to. But it looks better with purfling, so it's all good. And the one spot where the channel is visibly too wide is a good excuse to inlay something pretty and pretend it was on purpose.

Next up: even out the edges and bottom of the back strip channel and glue in the back strip.
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  #28  
Old 12-30-2015, 08:20 PM
charles Tauber charles Tauber is offline
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I was taught to use the method you describe to inlay a back strip into an already-joined back. I have long since abandoned that method in favour of simply sandwiching sufficiently thick center strip (and purling) between the joint of the two halves. I always use a reinforcement on the inside of the joint of cross-grain wood and have yet to find any advantage - long or short term - to inlaying, rather than sandwiching, the center strips. It is much easier to sandwich them than inlay them.

As previously discussed, if top, back or sides have appreciable runout, each half must be worked from the opposite direction. That is, after book matching, if one half has the runout going from guitar butt to heal, the other half will have the runout going from heal to butt. Tear-out can also be minimized by using a "zero-clearance" throat on the plane and an appropriate angle, often a bevel up plane.
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  #29  
Old 12-30-2015, 08:50 PM
rogthefrog rogthefrog is offline
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Originally Posted by charles Tauber View Post
I was taught to use the method you describe to inlay a back strip into an already-joined back. I have long since abandoned that method in favour of simply sandwiching sufficiently thick center strip (and purling) between the joint of the two halves. I always use a reinforcement on the inside of the joint of cross-grain wood and have yet to find any advantage - long or short term - to inlaying, rather than sandwiching, the center strips. It is much easier to sandwich them than inlay them.

As previously discussed, if top, back or sides have appreciable runout, each half must be worked from the opposite direction. That is, after book matching, if one half has the runout going from guitar butt to heal, the other half will have the runout going from heal to butt. Tear-out can also be minimized by using a "zero-clearance" throat on the plane and an appropriate angle, often a bevel up plane.
Thanks, Charles!

As it turns out, this back simply refuses to be flat. I had it sit clamped down and flat for 2 weeks, and it's warped back to its original shape. The problem is the shape is the reverse of what I was planning on doing, i.e. with the inside and outside faces as I intended, it is concave rather than convex.

So instead of fighting it, I think it may be better to just go with it and put the back radius along the wood's natural direction.

What this means, though, is that my crappy route is now on the inside.

My thinking was to cut the reinforcement marriage strip with a slight mortise at the bottom (the cross section would be like the cross section of a mushroom--narrower base and wider top), so its base sits in the route and the top of the strip covers the route plus a little extra width on both sides.

But what you're saying, Charles, is making me think that maybe I should just cut the joined back in half, excise my flawed route, replace the 1/8 inch or so with a new strip of wood (and purfling), and rejoin the whole thing.

Edit: I dry-fit a candidate strip with purfling and I like the look. So I'll cut out the route and re-join the back the way you suggested. Thanks again!
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Last edited by rogthefrog; 12-30-2015 at 09:00 PM.
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  #30  
Old 12-31-2015, 06:39 AM
charles Tauber charles Tauber is offline
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Originally Posted by rogthefrog View Post
Thanks, Charles!

As it turns out, this back simply refuses to be flat. I had it sit clamped down and flat for 2 weeks, and it's warped back to its original shape. The problem is the shape is the reverse of what I was planning on doing, i.e. with the inside and outside faces as I intended, it is concave rather than convex.
So, there are two things that you've learned from this exercise.

The first is that this is what generally happens to non-quartersawn wood, that it does not stay flat.

The second is that this is what happens when wood changes humidity: it changes size and/or shape. This is why stable humidity is required during the building process. Stable humidity can be achieved relatively easily without having expensive or complex equipment.

I once braced a quarter sawn back by gluing the back to quarter sawn braces planed to a convex arch. A few days later, when the humidity level changed, the back, braces and all, was concave - arched the wrong way. Very difficult to accurately fit parts that continually change size and shape while you are trying to fit them.
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