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Spanish heel
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estebanana
Posts: 9351
Joined: Oct. 16 2009
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 RE: Spanish heel (in reply to yourwhathurts69)
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To elborate on what Aaron said about how the Spanish heel is used in construction:
It is a very ancient system and it can be used to make a guitar without a mold. The reason it works is because the top of the instrument under construction is connected to the neck early on in the assembly of the main constituent parts of the guitar. Assembly goes: Top to neck block, then ribs to that sub assembly and finally the back goes on. When the top is connected to the neck / Spanish heel several structural, measurement and alignment problems are solved in one gluing operation.
The center seam of the top is lined up with center line of the neck. This ensures a straight plumb line from tip of headstock to the termination of the center seam of the top at the bottom block. The intersection of the top and the ribs at the 12th fret is established when the top is let into a shallow mortise cut into the Spanish heel where the ribs enter the slots. This also sets the top in plane with the neck ( so to speak ) so the fingerboard can have a plane to rest on. Once the top is trued and connected the heel by glue this assembly can be turned face down on the solera and the work can continue because the crucial neck and top alignments have been made.
Back in the old days it was not uncommon for the builder to use a couple of nails to set the top true in the mortise on the heel. They would put glue on the two parts, join them together, lay a straight edge on the center seam of the top to line up with the center of the neck. When that was true they would put a tiny nail through the top into the block and then recheck the straight edge. If it was still true they would put in another nail on the other side of the block and then one more on the seam to form a triangle and viola! The top is locked to the neck and all the nails are under the fingerboard. Some builders pulled the nails after the glue was dry and some left them in. Some did not even use the nails to secure the top and probably just used clamps. However if nailed the top was instantly secured and there was no need to worry about the top slipping under clamp pressure.
The Spanish heel was probably invented a long, long time ago. There are guitars from the late 16th century which have this construction and it was probably in use much before then, but due to the fragile nature of guitars we just don't have many, if any instruments from before that time. The extant vihuela called the Paris or Andre Jacquemart vihuela has Spanish heel construction. it is reasonable to think it was used commonly on early vihuelas which are mentioned in literature and court life accounts in the mid 15th century.
So as Aaron said all you need is a work board and a few clamps to ultilize this wonderful construction style. Imagine being an instrument maker in the 15th century and having to make many of your own tools. You might go to the black smith for your heavy tools or have him temper your knives or plane irons. You probably made your clamps and some mallets out of wood. You had a straight edges, marking tools, the black smith may have helped you with those too. So you get the picture, the instrument maker was dealing with basic tools. This meant they had to be clever and think of methods which allowed them to be accurate and decisive. The Spanish heel style embodies that spirit. There may have been shops which carried out more complicated tooling operations, but the small guy needed expedient ways of working and this face down, neck to top connection was both artful and useful.
As for the way the slipper extends into the back area. I've always thought that was to give more gluing surface to securely connect the back the neck and prevent the neck from slipping forward. It just looks like a common sense way for a carpenter to gain some mechanical leverage, it's just engineering made attractive. Whether or not that has bearing on how the back responds and sounds is up for debate. Nobody ever seems to want to debate it however because I don't think anyone really knows for sure. And there are better things to do with one's time anyway.
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https://www.stephenfaulkguitars.com
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Date Jul. 1 2010 9:07:47
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aarongreen
Posts: 367
Joined: Jan. 16 2004
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RE: Spanish heel (in reply to Ramon Amira)
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quote:
Aaron –
I have often wondered about the Spanish foot versus a mortised connection. Maybe you could elaborate a bit. It is my understanding that the purpose of the Spanish foot is to provide more integrity to the connection by making the neck an integral part of the body. With a mortise, even though they're joined, they are still two separate parts. Would that dissipate the vibrations to some degree? Also, you mentioned that you now use a smaller interior block, but I think that most luthiers using mortise still have a large block. Does a large interior block inhibit vibration of the back more than the foot? Thanks for your input.
Ramon
Hi Ramon,
One could argue that no joint is better than any joint (dovetail, mortice etc..) but I think it is well beyond the point of diminished returns as it were. I believe the spanish slipper foot construction came about as a way to avoid the need for molds and other fixtures. As such it had to be a continuous neck/heelblock with slots for the sides. However there is one downfall to this construction, at least in how it is commonly practiced in that the sides are often not glued into the slots. I always glued them myself but it is tricky and can be a real bitch if the glue swells up the slots to where you can't get the side in completely. An absolute nightmare actually so traditionally the sides just were left unglued at that point.
The problem comes about if the top cracks on both sides of the fingerboard. Now all the load from the strings is focused on the shoulder brace(s). If that brace lets go or creeps as it often does if it was glued with white glue.....there is nothing stopping the fingerboard from caving into the guitar. If the sides are glued to the block, there is much more structural integrity there. A few years ago I restored a David Rubio classical guitar with this exact problem. It required a new fingerboard and removing the top wood under it. Then the neck was pushed back into place, the cracks were in effect removed from the equation when new wood was fitted into place (using the old wood on the edges to mate up with the rest of the top to keep it looking like nothing happened.... A big job to say the least
In terms of the size of my interior block, it is big enough to do the job with a little extra there for stability. It's a rounded block, slightly wider than the neck at the top and around 50 to 55 mm wide at the back. However it extends into the body 35 mm, unlike the 70 to 80 mm you find with the slipper foot. It certainly is enough to resist the pull of the neck, steelstring guitars don't have blocks that are that massive and they take a lot more string tension.
In terms of the joint inhibiting the vibrations of the neck I would say I don't believe there are any losses there at all....if you do a good job fitting the neck. Mine is glued on with hide glue and it's basically a hidden biscuit joint. I size the end grain of the neck twice to fill it up and then glue on the neck. The only way to get it off is to saw it off and I can tell you that even after a minute of clamping, that neck isn't going anywhere. Amazingly strong joint esp. if you use hide glue and size the end grain.
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Date Jul. 1 2010 12:22:58
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Ramon Amira
Posts: 1025
Joined: Oct. 14 2009
From: New York City
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RE: Spanish heel (in reply to yourwhathurts69)
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Thanks Aaron, and thanks also to Estebanana for that comprehensive explanation of the Spanish foot. All of this just got me thinking about another aspect of construction. Do you – and do most luthiers today - use a template for the top? I know it would seem obvious to use one, but the great guitarreros of the past actually free-handed the outline of the top. I have read interviews where they talked about that, and how of course it naturally contributed to considerable variation from instrument to instrument. Logically, in the spirit of experimentation, it would make sense to free-hand, and study the results. I believe that Santos, Barbero, and Manuel Reyes free-handed the top. I have a photograph in one of my books of a Torres that is very noticeably asymmetrical, clearly not made from a template. Any thoughts on this?
Incidentally, if you want to read a most extraordinary interview with a guitarrero, if you don't already have it get a copy of "The Flamenco Guitar," by David George. There is an interview from the sixties with Manuel Reyes, in which Reyes proves to be incredibly articulate, and discusses construction in both a lucid and poetic manner.
Ramon
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Classical and flamenco guitars from Spain Ramon Amira Guitars
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Date Jul. 1 2010 14:26:34
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estebanana
Posts: 9351
Joined: Oct. 16 2009
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RE: Spanish heel (in reply to yourwhathurts69)
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I think dovetails are fine, a half a million Martin and Gibson guitars have them. (which keeps me and lots of other people in business) Plus all the other American steel string models that use them. Fleta used a dovetail, plus a few others who built non Spanish heel classical guitars.
There was one company the US that became almost notorious for using a Spanish heel on steel string guitars. That is B.C. Rich. A small operation from the late 1960's through 80's (IIRC the history). They were a small shop that did great work and made very good sounding guitars with high quality woods, often very desirable Brazilian rosewood. Their D-45 models have always been a point of interest to those who do net resets in steel strings because the Spanish heel style construction does not stand up as well to the high tension of steel strings and often they need neck resets sooner than a dovetail neck.
Since BC Rich made a fine guitar, most repair persons and guitar owners don't want to dispose of a nice instrument because of one shop made design characteristic which causes neck angle failure. The common consensus to restore neck angle of a BC Spanish heel is to cut the neck clean off at the body and refit it to be a bolt on neck with a joint simply butted to the guitar body. You can also go the route of making a dovetail joint, but you then have to disassemble the neck from the ribs whole and create a new interior block for the guitar and use the meat on the Spanish heel to create the dovetail. This requires pulling the back off the instrument to extract the Spanish heel and change the neck block.
Other solutions include cutting the neck off at the body and creating a spline joint, a sort of modified bisquit joint where the body and neck are both slotted to receive a spline of wood to join them.
So if you can imagine you've got to invent a neck reset/attachment method on the fly which converts a Spanish heel steel string to some other type of joint which is designed to be taken apart and reset. The dovetail was traditionally the joint of choice by Martin and most other shops followed suit. Several problems arise when you have to cut the neck off of a Spanish heel steel string, one of them being intonation. If you remove too much material at the point where the body and neck touch at the fingerboard you are effectively shortening the neck enough to change the intonation and the guitar will play sharp.
It's tricky stuff. When the guitar has a dovetail to do a neck reset, you remove a fret at the body join, drill a hole into the dovetail cavity and remove the neck by inserting a hollow needle connected via tube to a pressure cooker. This Gilligan's Island contraption will steam the joint until it is soft enough to prise apart. ( Never attempt this unless you are a guitar maker and repairer with a lot of experience. Not for beginners to try their hand at alone.) When the dovetail joint has been separated and the neck and body are extricated from one another they are clamped up with cauls to keep the residual effects of the steam from further disassembling the neck block from the ribs and then set aside to 'condition' for a day or two. Once the wood has settled down from the steaming operation the dovetail can be reset by removing wood in a long thin wedge shape from the back side of the heel to the top side of the heel. The process sounds easier than it is because there are myriads of details to watch along the way. If done well the reset operation is virtually invisible.
I learned something from doing a BC Rich neck joint re make / reset where I choose in that case to remove the neck and create a bolt on neck joint: There was no perceptible difference in sound or volume that either I or the customer could hear between the Spanish heel intact or after I removed the neck and bolted it back on. The sound remains the same to almost quote a song. Once the joint was clean and securely bolted with the contact between guitar body and root of the neck, it was a rock solid conductor of vibration. The bolts may have even helped with that, but I have no conclusive evidence other than my own anecdotal observation. Prior to this personal revelation I was one of the naysayers who would would only grudgingly think about a bolt on neck of any kind. But when faced with making the repair I had to amend my ways.
For flamenco guitars I still think the Spanish heel is a fine way to construct, but for other types of guitars including some classicals there are other methods to choose. The note on Gene Clark: It's curious he would have said that vis a vis steel string makers and the Spanish heel. Gene is the Dean, ( at least in my part of the woods) but even the Dean of the class gets it wrong once in a while. A Spanish heel on steel string is not the best solution for long term neck reset capability even though it does make a fine guitar. It's not as suited as a dovetail or some of the more neo-modern neck joint styles.
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https://www.stephenfaulkguitars.com
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Date Jul. 3 2010 18:55:02
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yourwhathurts69
Posts: 117
Joined: Sep. 16 2009
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RE: Spanish heel (in reply to yourwhathurts69)
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Thanks for the responses, everyone.
just to clarify, my original question was just in regard to the actual heel, not the entire "spanish foot" method of construction. in other words, the exposed, pointy part of the spanish foot.
however, after reading some of the responses, it has made me wonder about the spanish foot method versus the dovetail method. I've read and have been told that glued joints can be just as strong or stronger than the actual wood. if this is true, why not just do a dovetail joint? it would be easier (if done properly). and, if it's stronger, wouldn't it be better? I know it might not be the traditional way of construction, but as technology changes, so do methods of construction. in many cases, technology leads to better methods.
also, from the responses, i started to think about the foot inside of the body. some builders use a round foot, others a square foot. the shape and size inside seems to vary among builders. does it really matter, especial if most (or all) of the vibration and sound production happen before the sound hole? (ie by the bridge and lower bout, but before the upper bout and spanish foot). i could see the shape/size/mass of the foot having minute and insignificant effects on the sound (especially when compared to the guitar as a whole), but is there any reason (in regard to sound and durabilty) to chose a certain shape or joint over another?
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Date Jul. 3 2010 23:39:09
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Tom Blackshear
Posts: 2304
Joined: Apr. 15 2008
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RE: Spanish heel (in reply to aarongreen)
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quote:
ORIGINAL: aarongreen
I just finished a restoration of a very fine Fleta and had a lot of time to look at it. To me that plantilla looks like one of Gary Larson's drawings of fat kids in the Far Side. Big puffy cheeked butterballs. Pretty those guitars are not, unless you like them like Rubens, which I don't.:)
Still and all it was pretty much the best Fleta I've encountered and a stellar world class guitar, really inspiring. So you know, you take the bad with the good.
aaron
Hi Aaron, I had a chance to look at a Fleta top, some years ago, inside and found that there was a hollow place thinned out about the size of a quarter, half way between the sound hole and bridge on the outside bass edge.
Have you had any similar experience in finding these top graduation techniques. My theory is that the guitar's top is so stiff that Fleta relieved a small area on the top to bring out more bass sound.
The reason I mention this is that Miguel Rodriguez has thinned His bass side in a similar fashion, in some small areas on occasion, almost as thin as a business card
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Tom Blackshear Guitar maker
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Date Jul. 9 2010 18:11:16
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