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Kerfing species Top and Back
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Author:  Anthony Armijo [ Thu Jun 28, 2012 5:50 pm ]
Post subject:  Kerfing species Top and Back
Can some of you guys with dozens of builds under your belts give me your opinion. I was thinking of stocking up on kerfing wont get into reverse or standard but it is all made from Sapele. Is there an advantage to using Kerfing made of same species as the top and using the Sapele kerfing just for the back?
Author:  Chris Ensor [ Thu Jun 28, 2012 6:14 pm ]
Post subject:  Re: Kerfing species Top and Back
I don't see any advantage in using a wood that matches top. The point of kerfing is to add gluing surface area. I guess if you were to use spruce, it would reduce the weight of the guitar, but that is the only advantage I see in it.

I have been using spanish cedar lately with the idea of helping regulate internal humidity (think cigar box).
Author:  bluescreek [ Thu Jun 28, 2012 8:16 pm ]
Post subject:  Re: Kerfing species Top and Back
sapele is a heavy wood . I think I would go with mahogany or spanish cedar. You don't want to add more weight that you have to.
Author:  Markus Schmid [ Fri Jun 29, 2012 6:40 am ]
Post subject:  Re: Kerfing species Top and Back
bluescreek wrote:
You don't want to add more weight that you have to.

Why?

I personally think that it is not a bad thing at all having more mass in the sides and/or linings as long as one is concious of what the (acoustical) effects of mass at the rim of the top are. One can build with heavy sides or with lightweight sides, nothing wrong with either method. As i see it, the linings are (in a mechanical/acoustical sense) part of the sides not of the top.
Author:  bluescreek [ Fri Jun 29, 2012 10:16 am ]
Post subject:  Re: Kerfing species Top and Back
I respectfully disagree . All the really great guitars I played were light . There are few exceptions to this rule . You of course are free to build as you wish . The kerfing is a gluing surface and that is all it is . Will Sapele work , Sure but the added density of it may effect the sound. I am a traditionalist and use Cedar or Mahogany.
Early in my career I used what was available and soon found out there is a reason that most guitars use these 2 woods for kerfing. If I had to pick a third I may use spruce. Just my 2 cents .
Author:  alan stassforth [ Fri Jun 29, 2012 10:32 am ]
Post subject:  Re: Kerfing species Top and Back
I like basswood,
because it's easy to bend.
Plus, I bought a bunch years ago,
and have enough for the rest of my life!
Author:  Markus Schmid [ Fri Jun 29, 2012 11:15 am ]
Post subject:  Re: Kerfing species Top and Back
bluescreek wrote:
All the really great guitars I played were light . There are few exceptions to this rule .

Well, I don't want to count all these "exceptions" which could take up quite a bit of time. I would agree though that alone making a guitar heavy (or light! beehive ) is not the receipt for making a good guitar.

Edit:
Even if there was only one exception this would be enough to accept that "building heavy" can be used to to make a great guitar. Oh... and great guitars are exceptions anyway, but we won't stop building because of that, will we? ;)
BTW, I prefer to play light guitars - because they weigh less on my leg or my neck...

Getting back to the "kerflings"... if made of a wood species that doesn't get split as easily as some conifers and a few lightweight hardwoods one could make them narrower, freeing up some (although not really much) soundboard area to vibrate. In any case I think that choosing the wood species for linings is worth a thought or two, and its material properties should be taken in account in the construction process, e.g. dimensioning of the linings.

Sorry for the lengthy edit, could have been a new post. But well, here it is.
Author:  John Coloccia [ Fri Jun 29, 2012 11:28 am ]
Post subject:  Re: Kerfing species Top and Back
Spanish cedar smells nice and sands easily, so I make them out of Spanish cedar now.
Author:  CharlieT [ Fri Jun 29, 2012 11:54 am ]
Post subject:  Re: Kerfing species Top and Back
Sapele isn't THAT heavy, is it? Although sapele is typically marginally denser than today's average mahogany, it's used almost interchangeably with mahogany for back and side material by some guitar makers. As tiny as the linings are in the scheme of things, I can't imagine that any added weight from using sapele in place of mahogany would even be measurable.
Author:  flounder [ Fri Jun 29, 2012 1:07 pm ]
Post subject:  Re: Kerfing species Top and Back
Is Western Red Cedar a suitable material for kerfing?
Author:  StevenWheeler [ Fri Jun 29, 2012 1:55 pm ]
Post subject:  Re: Kerfing species Top and Back
How many times do we have to go through this?

Linings hold guitars together.

Kerfing is the act of cutting all those slots in the lining to make it bend!!!
Author:  John Arnold [ Fri Jun 29, 2012 1:55 pm ]
Post subject:  Re: Kerfing species Top and Back
Quote:
As tiny as the linings are in the scheme of things, I can't imagine that any added weight from using sapele in place of mahogany would even be measurable.

I would be more concerned with the hardness and stiffness of the kerfing wood, rather than the density.
I used to use willow and basswood, but those two woods are pretty dead, acoustically speaking. When I finally switched to Spanish cedar, I felt that my guitars sounded a bit more like vintage Martins.
Quote:
Is Western Red Cedar a suitable material for kerfing?

IMHO, spruce or WRC should make good kerfing, but I still prefer Spanish cedar. For my all-domestic models, I used butternut or sassafras.

Quote:
Linings hold guitars together.
Kerfing is the act of cutting all those slots in the lining to make it bend!!!

Both words are verbs that have been transformed into nouns, so IMHO it is a distinction without a difference.
Author:  CharlieT [ Fri Jun 29, 2012 1:58 pm ]
Post subject:  Re: Kerfing species Top and Back
StevenWheeler wrote:
How many times do we have to go through this?

Linings hold guitars together.

Kerfing is the act of cutting all those slots in the lining to make it bend!!!


Technically, you are correct, but 'kerfing' has become an accepted term for kerfed lining, and one that all the major luthier suppliers use. It's not that big of a deal. How about we move on to something that matters.
Author:  fric [ Fri Jun 29, 2012 4:36 pm ]
Post subject:  Re: Kerfing species Top and Back
well I escape from traditionalist zone and for back my lining is kerfed mahogany and for top laminated 2-3 layer of maple now ,or some other hardwood

regards
Author:  wbergman [ Fri Jun 29, 2012 6:46 pm ]
Post subject:  Re: Kerfing species Top and Back
Years ago I read that part of the sytem that made Hauser guitars good was the large amount of purlings that supposedly stiffened the edges.
Author:  Anthony Armijo [ Fri Jun 29, 2012 10:34 pm ]
Post subject:  Re: Kerfing species Top and Back
Thanks for clarifying Steven that was a great addition to the thread.
Author:  Nils [ Fri Jun 29, 2012 11:48 pm ]
Post subject:  Re: Kerfing species Top and Back
Black Walnut has become my lining of choice. I have an affinity for woods that grow where I live - thats the only real reason I do it.
Author:  Trevor Gore [ Sat Jun 30, 2012 3:22 am ]
Post subject:  Re: Kerfing species Top and Back
bluescreek wrote:
You don't want to add more weight that you have to.

That depends where you're adding it. Greg Smallman has been making really heavy classical guitars for years (3-3.5kg) but his soundboards are amongst the lightest, <1.5mm of WRC with balsa/CF lattice bracing. You'd be a brave man to say he's doing it all wrong, given what his guitars sell for.

Lining stiffness and mass and side stiffness and mass are variables in the mix that can be adjusted to taste. Heavy sided guitars can be outstanding, whether they're classical or steel string.
Author:  Don Williams [ Sat Jun 30, 2012 4:38 am ]
Post subject:  Re: Kerfing species Top and Back
Where's Howard Klepper when you need him?
Author:  Andy Birko [ Sat Jun 30, 2012 7:53 am ]
Post subject:  Re: Kerfing species Top and Back
Don Williams wrote:
Where's Howard Klepper when you need him?


I think he's out making kerfing. laughing6-hehe
Author:  bluescreek [ Sat Jun 30, 2012 10:03 am ]
Post subject:  Re: Kerfing species Top and Back
The kerfed linings main job is to create a glue surface area . John Arnold's also points out a secondary effect , that is dampening . When you look at physics , an object that is in motion tends to stay in motion and an object at rest wants to stay at rest. I agree that there are areas that are more prone to this than others , but the realities are that the physical properties of the woods used and construction methods do interact. This means the heavier , the more energy it will take to get the guitar working. There is a balance that you need to find , it isn't just about light , heavy or stiff or floppy.
I used many different woods in my early days and there are some very good local woods out there . Not all woods work well in instruments. Not all woods used in Violins translate well to guitars . You have to find what works well for your abilities and techniques. Pre War Martins are pretty much are the standard for many steel string builders . That doesn't mean it is the only standard . After all Dreds are great guitars but there isn't anything wrong with a good 000.
There are some very good contemporary builders out there . Find what works best for you , after all the end results are mostly subjective and hard to quantify but the more you build and the more you look at the engineering and physics in the box , the more you can learn. If you are doing this as a commercial enterprise you will soon find out if you will be successful or not . It will be a very educational journey .
Learn from others mistakes, you can't make them all yourself. Learn your sources , not all information sources are good sources. Many more opinions are printed than facts . and that is the hardest part in learning .
Author:  Anthony Armijo [ Sat Jun 30, 2012 11:32 am ]
Post subject:  Re: Kerfing species Top and Back
I appreciate all the information. It appears the jury might be out on this. What brought this topic up was that I had been buying Kerfing/Lining for each build, bass for top and spanish cedar for back. I found a source that is pretty inexpensive if I buy the strips by the gross but it is all sapele and with that much stock I would just use it for both the top and back. I have both spanish cedar, Bass wood and Mahogany lumber. Maybe I will cut my own and do some experimenting. I just hate spending the time cutting when I can get it so cheaply and spend my time building instead, but it might answer some questions so I'm off to do some kerfing. Thanks Guys.
Author:  Dave Stewart [ Sat Jun 30, 2012 11:34 am ]
Post subject:  Re: Kerfing species Top and Back
+1 for Spanish Cedar..... it's light, tough, aromatic, pretty...and I have lots of it from my "humidor" days. laughing6-hehe Lots of others though (eg willow)
FWIW, in this case they're both nouns: kerfing (actually kerf) is the slot ("a slit or notch made by a saw or cutting torch") and lining is the whole ("material that lines or that is used to line especially the inner surface of something " )
Author:  Andy Birko [ Sat Jun 30, 2012 11:45 am ]
Post subject:  Re: Kerfing species Top and Back
bluescreek wrote:
When you look at physics , an object that is in motion tends to stay in motion and an object at rest wants to stay at rest. I agree that there are areas that are more prone to this than others , but the realities are that the physical properties of the woods used and construction methods do interact. This means the heavier , the more energy it will take to get the guitar working. There is a balance that you need to find , it isn't just about light , heavy or stiff or floppy.


I don't know if there's a lot to this story but I think there are more variables at play here. The first thing that comes to mind is impedance.

There are sort of two extremes to building philosophies - on the one end we have the extreme that the top alone should produce all the sound. Smallman championed this philosophy by using a very thin and active top and massive sides and back. The impedance mismatch between the top and sides reflects most of the top's vibrational energy back into the top, similar to the way a solid body's impedance mismatch reflects most of the string's energy back resulting in a long sustain.

The other extreme is the "active back & sides" camp where the vibrating back gets into play to create the guitar's voice.

Increasing the mass of the linings could indeed change the impedance between the top and the sides and change the voice of a guitar and not necessarily in a negative way. I think it would just be different.
Author:  David Malicky [ Sat Jun 30, 2012 2:19 pm ]
Post subject:  Re: Kerfing species Top and Back
Great post, Andy, on the impedance issue. There is also a 3rd camp, which has active top and back, and inactive sides -- that one seems to have the greatest potential from a physics perspective.

Trevor's book has a very thorough analysis of the top, back, side, and air interactions. Simplified greatly... In the 'main top' mode (the largest sound producer), most of the top and back move in the same direction, while the sides move in the opposite direction (conservation of momentum). For example, Fig 9.14 (193 Hz):
http://books.google.com/books?id=9CRSRY ... &q&f=false
For this to happen, the outer part of the top and back have to move in the opposite direction (negative phase) as the center, which cancels some sound production. Conservation of momentum also tells us that if you want more of the top and back to move faster (make more sound), increase the mass of the sides. In other words, heavy sides and linings give the top an 'earth' to push against, which lets more of the top (and back) make more sound. The 2 I've done with heavy sides & linings are easily the loudest.

In addition to the mass of sides/linings, there's also the issue of stiffness. Often mass and stiffness go together (thicker wood), but not necessarily -- kerfed vs. laminated linings. I've not seen any physics on lining stiffness, but it stands to reason that stiff linings help the top 'see' the full mass of the sides.

Whether the heavy sides/linings approach sounds better is a different question. In the Martin tradition, heavy sides or linings may indeed sound worse -- the Martin designs are already highly optimized, so even small deviations are inherently more likely to sound worse than better. If building outside an tightly optimized tradition, louder is often a good place to start.
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