View Full Version : Loar Specs
I am starting a Stewmac kit. I would like to know how close Don's thickness specs are to the Loars'? How can I get the specs for the Loars?
What are Don's specs? #The best bet for getting Loar specs are to either measure a Loar or possibly even better measure a new Gibson master model. #I think if anyone knows Loar specs it's Derrington and the master models are probably more consistent than the Loars were. #I've heard a wide range of numbers when it comes to loars. #Your best bet it to get an exact copy of the arching and the thicknesses for that arch. #Different arches will have different grads. #Siminoff is suppossed to have a "definitive" set of plans out but they are way off from what I've got. #I haven't seen his archings though so maybe his loar measurements are for a different arch than the ones I've seen. #Any experts care to talk about differences in Loars and their published specs?
If your building your first mandolin ,I suggest using the numbers on the Stew- Mac print as a guide and don't expect to duplicate a Loar the first go round. It's a real challenge just to get it put together ,maybe you can build a perfect Loar copy on the second attempt. The recurve thicknesses are actually quite thin on that print ,and you may want to stay at around 3mm unless you have a very stiff piece of spruce.
inner recurve 3.5-3.7 mm
try and make a nice flowing dish shape for your first one use stew macs tone bars and you should have a nice sounding mando.
Good advice from Mr. Hilburn. You definitely do not want to go any thinner on the recurve than what is stated on the Stew-Mac/Macrostie plan, and the thickest centre graduation thickness can stand to go a very small amount thinner. Don't worry about Loar's; Don's plan will make a great mandolin, and as Jim has stated in previous posts, if you were to go any thinner than the graduations stated on Don's plans (or even if you don't), you will start to get the tone bars "witnessing" or showing through the top after stringing, which means you are approaching the outer limits of what you can expect #a poor (or good!) piece of spruce to withstand. A mandolin built to those specs will still require a substantial "break-in" period, so be patient, before and after building.
If you get Siminoffs "New" book it has the Loar specs. I have done 2 Stewmacs and I am doing a Siminoff right now.
The main difference I see in the two plans are.
1 The neck angle (which you can't change now)
2. The Location of the tone bars. (which are way different) Siminoffs look to be in the same location as Dudenbostels, McRostie has them inward a bit more and a lot more on the treble side.
As far a graduations, I did not check, because Siminoff graduated the top and back for me. Thats the part I screwed up on my Stewmacs, I got them too thick (my fault, not the plans) http://www.mandolincafe.net/iB_html/non-cgi/emoticons/smile.gif
From the original specification sheet for F5s (GAL Journal):
Backs: The carving graduations at center 3/16". Fin. 5/32"
at 7/8" from sides and tail end 1/8" Fin. 1/10"
Tops: The carving graduations at center 7/32". Fin. 11/64"
at 7/8" from sides and tail end 5/32" Fin. 1/8"
So converting this to decimals and metric, backs are 0.156" (4.0 mm) at the center and 0.1" (2.5 mm) at the recurve. Tops are 0.17" (4.4 mm) at the center and 0.125" (3.2 mm) at the recurve.
This only provides a very rough measure of the graduations, but it is a good starting point.
Mr Stahl's interpretation of the original spec sheet is very good, and Loars were done very closely to it. The problem is that they need a couple more statements to clarify that the recurve specs do not apply everywhere.
One must know that the top has some elliptical symmetry to the carving in that it gets thinner again under the fingerboard extention similar to the tailpiece end...but the back does not. It essentially gets thicker and thicker as you go north along the center line. The thinnest part of the back is an elliptical "U" shape. Most builders apply some symmetry to the back by taking way too much meat out of the inside in the upper bout area.
Hey Darryl.. On my Paganonni I used to have I noticed what was kinda unusual that the back of the mandolin near the button had more meat than any other mandolin I have ever seen on the outside of it. What I mean is at the back button the thinkness was raised Were all the Pags like that and were they any loars like that?
Hey thanks. This gives me some things to consider and some thoughts on variation of the kit. Just looking for a great sounding instrument when it's done. Not too worried about the assembly or finish out, but the graduations are a new adventure. I'll let you know how it goes.
After reading Steve Stahl's post and reading F5journl's reply I have revised a comment/question and deleted it from another post and here we are now. I see that the center and the recurve are the recorded measurments. I was wondering if the Loars used a common rate of graduation from center to recurve? A problem with this train of thought is if the center and recurve are fairly consistent to the center and recurve thickness's than a common rate of graduation must be out of the question because the tops had to be tuned. With a set center and recurve thickness you would have to play with the rate of graduation to get the proper sound from your top. I may be right or wrong or possibly stating the obvious but please let me know if I'm on the right train of thought. It wouldn't be the first time I hopped the wrong train. Thanks all John http://www.mandolincafe.net/iB_html/non-cgi/emoticons/rock.gif
According to Charlie Derrington Loars were not tap tuned as free plates but were just carved to spec.
Chris, I agree that the Siminoff plans are off or at least suspicious. I do not have the plans but from what can be seen here (http://siminoff.net/Media/roger_dwg_collage.JPG) (bottom left). There are three lines in the graduation map (of back), representing three different thicknesses, that meet the outer edge! That's most certainly not kosher. No one will argue that the edge is 3/16" thick all around the plate except the part of the scroll. I assume that the outermost line that connects smoothly on the edge is the 3/16" line. That suggests that the back is quite a bit thicker in the center (bridge center) than the thicknesses stated by Mr. Stahl.
I used to own the Stew-Mac plan and I am sure those archings and graduations were not taken from a Loar. The single evidence of this is the ridge on the back. This is certainly not a feature of a Loar mandolin. Howewer, there is a Loar with a ridge, but with a very subtle one. The ridge on the plans is maybe more pronounced than the ridge of most old mandolins with a "ridged" back.
It'd kiinda tough to explain but most all Loars have a flat button 3/16' high. The binding on the adjacent sides is also 3/16" high...all the way into the scroll area and the point area on the other side. But the profile starts rising almost immediately fron the binding. Along the centerline headed to the flat button..the back smoothly adjusts profile to return to 3/16" high at the button
Here's a jpg of the grads that I was sent last year. I don't recall if these were from one of the books or someones personal copy.
I've never seen a copy of Ted's prints before, but assuming it is correct ,I would conclude that Loar's were inconsistent at best, and that they may not have been all that carefully graduated. How else would you explain a 4.2 reading at the bridge while it was 4.5 a couple of inches out toward the rim. Also, 4.5 seems very thin to me. While 6.35 on McRosties may be a little stout ,I personally have scrapped tops that I got below 5.5, worrying about the structural integrity. 4.5 is what I'm looking for around the inside f-hole point. And I've made some pretty thin-topped mandolins in the past. They will start to distort.
Those graduations were taken from a refinished Loar..use your own judgement on how it got that way
Darryl, Please elaborate on your comment that those numbers were from a refinished loar. I'd like to hear more detailed information about that mandolin, its history and what became of it.
That could certainly explain what looks like rather less than uniform instrument.
I was told by Tom Ellis, who Davis acknowledges on the print, that those numbers came from a mandolin that was brought in to him for repair. The story went that someone had to prove his love for his wife over the love for his Loar by smashing it onto the driveway. It was the wife who contacted Tom and remorsefully inquired of him to do the repair. Tom took it in and said that it was way beyond repair, but that he was able to take measurements off of it. It must have been refinished prior to that. If any of you are not aware of who Tom is, he has built a few great sounding mandolins in his day and I trust that he took the most accurate of measuremnts off of that one example. Who knows, maybe it wasn't the first time that Loar had been sacrificed to prove true love.
What do you think Daryl??
I don't know much about it other than it had been refinned. I only heard that Ellis took the measurements. The best way to arrive at loar specs its to do a composite of all available info on graduations..from there you can see the consistency of measurement. There are about 5 or 6 "maps" that people have done
There seems to be quite a bit of information about Loar plate thicknesses and graduations available, but I've not seen anything on tone bar size for Loars. Darryl, do you have any information on this?
My feeling is that the tone bars on the MacRostie plan are taller than on a Loar, and they stop at the recurve rather than continuing out to the lining, also the placement is slightly different than on a Loar.
The Loars go to the lining. #I dont have my tone bar info handy..but memory says they are 1/4" wide with one being 5/16 high and the other 1/4 high. #They are rounded slightly triangular. #The bass tone bar parallels the f-hole about 1/2" in from the edge of the f-hole "holes" while the treble one is in about an inch from the upper end of the f-hole and about 1-1/2-1-3/4 at the lower end. #Essentially the treble bar runs straighter up and down and is further in. #I can just barely touch the treble tone bar with my little finger..whereas you can see the bass one
One of the best pictures ever on the subject is one from the Bluegrass Unlimited article on the C. Derrington fix of Monroes Loar.....showing the inside of the top with the back off. Monroes mando seem to have a peculiar placement of the tone bars..possibly contributing some to the sound. I'll try to scan and post it
I have seen that pic of Monroe's mando I actually made a templete from that pic by blowing it up to the exact size of a mando top and taking the tone bar placement from it.
That's very intersting that the mando in question was refinished.
Today I had a go at Gary Vessel's one year old F5 with a Hacklinger gauge. #It came out almost identical to the print I posted earlier! #Probably a couple of tenths thicker, particularly as you moved toward the neck in the center of the top. #Gary said that he made that one from a particularly hard piece of red spuce. #
I think it is one of the best sounding mandolins I've ever heard. #It's definitely loud http://www.mandolincafe.net/iB_html/non-cgi/emoticons/smile.gif
Number 2 is comeing together as we speak and it's top is significantly thicker than #1. #Some where in the low 5mm range in the center of the top as opposed to 4.4mm or so. #The recurve area is about 3.3mm as opposed to 2.7mm on his #1.
Maybe the type of spruce has a lot more to do with it than I would have guessed.
Regarding the tone bars, you will find variations in how tall , how long, and placement. But in general I have found in the 5 Loars I have measured that the treble bar runs just inside the treble adjuster of the bridge almost paralell to the edge of the fingerboard, and the bass bar splays out much wider. They have been in the same places on the ones I saw, but the lengths varied. Some stopped at the recurve area and some went all the way to the lining, often one bar is long and the other is shorter in the same instrument. John Reischman's '24 and David Grisman's '23 are like this. So far I haven't measured a top that was thicker than 4.4mm in the bridge area, they are usually a bit less, around 4.0mm - 4.2mm.