Official Luthiers Forum!

Hi, I am starting my 6th OM size guitar, and first off would like to thank you all for the wealth of knowledge that you share in this forum.
I have had very good results and would love to post some pictures, but I am not able to get them down to an acceptable size for the forum, I am still not up to speed with reducing file sizes. Anyway I am wondering if my guitars are "average weight" or too heavy. My heaviest is a walnut B&S, walnut neck, neck block, and heel block. It weighs in at 4lbs. 15 oz. which I know is heavy due to using walnut for neck and neck & heel block.
The other 4 weigh in at 4lbs 8oz each +or- an oz. They all have mahogany necks, and neck and heel blocks, except one that has an oak neck(which suprizingly added only 1 oz). The B&S are 2 with EIR, flamed myrtle, and oak. They were weighed at 44% RH and 70 degrees temp. All of these guitars have a dovetail neck joint.
So the question is, what kind of weights are you all averaging on an OM size guitar (fully completed for playing, ie. with strings, tuning machines, etc. installed)?

Thanks, Chuck

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Hi Chuck. It's great to see someone else interested in the weight of their guitars too.

Here are a couple of OMs that I built in the last year. The Koa one weighs 3 pounds 6 ounces and the BRW one weighs 3 pounds 11 ounces. Interestingly they both lost an ounce or two months after they were completed. And since you mentioned it they were weighed in 42 - 48% RH at around 72F.

The only difference besides the tuners is the wood choices.

I would say that is a VERY hard question to answer.... I have built several guitars that were heavy because I used African Blackwood or Ebonies and others out of Black Limba, Tasmanian Blackwood, etc.... that were extremely light. Truss Rods, Neck woods, Bracing Patterns and the tonewoods will dictate most of the weight outcome.

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Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

Thanks Hesh and Peter.

Hesh, those are fantastic looking guitars, I really like the koa, I'll have to put that high on the list for future guitars. You do a great job at keeping the weight down too. Like anything else, it's the last few ounces that are hard to shave off. I assume that you are using a truss rod. I use the LMI double acting truss rod. I use mahogany for the neck and heal blocks, what are you using? I know some of the folks here are using baltic birch plywood which I suppose could shave off those last few ounces.

Type of wood and thickness can effect weight also as Peter said. My thicknesses are sitka top (which I have used on all 5 guitars) .105 to .110, backs @ .100, and sides @ .085 to .90.

Thanks again for replying
Chuck

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The key question is, do you like the sound? If you do then your guitars are the right weight, don't always assume that ligher is better, it may be for one design, but not for another. A heavy stiff neck may give you incredible sustain not available to the featherweight.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

I don't build OM's so I can't help you there, but if you want to shrink pictures for the forum you can do it for free at http://www.shrinkpictures.com/.

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Ken Franklin
clumsy yet persistent
https://www.kenfranklinukulele.com

Right - lighter is not necessarily better it is just lighter.

My goal in guitar building besides tone, playability is light and stiff guitars though. It's the kind of guitars that I prefer to play where I can feel the thing vibrating against my body when I play it. So I weigh everything and have given thought to using woods and products that are light weight comparatively speaking.

Tuners are interesting because a pair of Waverlys or Grover open backs can be around 140 grams where Gotoh 510s can be 265 grams. I use the same truss rod that you do only I like the Allied one designed by Mark Blanchard better. Both the LMI and Allied rods are 119 grams.

I prefer mahogany for my blocks and linings and necks for that matter. It's light weight and a superb and very under rated tonewood.

Bracing is not going to be a place where you can save a lot of weight IMHO because you need what ever bracing you end up needing for your specific top to keep the thing from folding like a cheap suitcase.... Typically bracing only weighs around 40 grams anyway ( Adi - OM style guitar) so you can see that even a 25% reduction is only less than 1/3 or an ounce in weight savings and again in a place where you need some beef. Apologies to the vegans for the beef term.

Finishes add weight! And finishes can add more weight than I imagined until I started weighing my guitars in the white and then after finishing.

To me a light weight guitar is secondary to the sound that I hope to achieve but it is related to the sound I am after too. This gets into the area of backs and how there are a couple of schools of thought in guitar building as to how a back should/could work - reflective or slightly flexible.

I built a L-OO where I pulled out all the stops to see how light I could build a guitar. It came out at 2 pounds 9 ounces AND this guitar lost another ounce or two a year later which I also can't understand why. It is lightly french polished and sounds very different from my guitars with nitro, poly, and urethane finishes. I didn't expect that this light weight L-OO would hold up well building it as a learning experience but it is my favorite shop guitar to play. It is like holding air and very responsive since there is not much mass to accelerate.

Anyway I agree with Colin that light weight guitars are not the end all to be all - they are simply light weight. It's all good.

Also there is a free program called The Gimp that does professional level photo editing:

http://www.gimp.org/downloads/

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I have never weighed my guitars but I tend to build very light.

Thanks Colin, how it sounds is at the top of the list, along with a few others, in importance. I have been happy with the sound of my guitars, so I guess I am honing in on how much the final weight will be.

Thanks Todd, tuners can add or subtract 6oz., this was something that I had originally overlooked.

I like the feel of a lightweight guitar when playing, like Hesh said, but at the same time do not want to give up sustain.

Thanks Ken for the picture shrinking site, Im am going to try to post a picture later.

Chuck

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The McPherson guitars are easily twice as heavy as any acoustic I've ever built. I think it's more owing to the super thick top, and backs, laminated bracing, almost solid carbon fiber neck, and big brass rod through heel. Matt McPherson told me that he tried to build the guitars light but he thought they sounded cheap.

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John Mayes
http://www.mayesluthier.com

Well I am more than happy to concede that lightness is not the end-all-to-be-all but......... I am not willing to concede that heavier guitars will always sustain better/longer. My experience with my own guitars has been different and sustain is something that is often noted and brought up by many of the OLFers who have played my light weights.

Admittedly I don't understand the physics anywhere close to the point of say Al Carruth or Colin but I do know what I hear, feel, and see (most of the time........) . Sustain is IMHO not exclusive to heavier guitars.

All things being equal, which is not really possible in guitar building because we are dealing with wood, more mass requires more to drive it - right? Likewise more mass requires more to keep driving it - right?

Oh Al?

I like to have the right mass in the right places and know what kind of music I'm building for. I usually have the most top strength and mass near the x brace where it will do the most to keep the guitar from emploding.

I build a little heavier for bluegrass players who use a flatpick and medium strings. They want projection and they don't want the guitar to lose focus when they drive it hard. For them a little heavier back aids projection too. I build lighter for fingerstyle players and singer/songwriters who are looking to be enveloped by the sound. They want to hear all the subtleties the guitar has to offer and I find that a lighter guitar is better for them.

In my building, a top that is too light can produce uneven note volume when fretted in different places on the fingerboard. I like a more balanced sound but it can tend to be sterile if the top is too thick. You might want to vary the thickness of your tops if you are looking to save some weight and improve sustain.

The bridge material and design can affect the weight of a guitar also.

If you like closed back tuning machines with a little less weight the Gotoh minis with plastic buttons come in at 170 grams.

Ultimately, you have to find the right balance between structural necessity and the music you are going for.

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Ken Franklin
clumsy yet persistent
https://www.kenfranklinukulele.com

Interesting topic. I am just starting another OM so think I'll put it on a bit of a diet to see how it turns out. I am going to use a set of black acacia and a really nice stiff sitka top that I got from someone that has had it sitting around since 1962.
Any general guidelines on how thin I might be able to go on the back, sides, and top? I had been using the Martin style truss rod made by Gotoh, but will try the Allied truss rod with this one, as well as a set of open back tuners instead of the Gotoh 510s that I have been using.

Hesh....those two OM are beauties!

Alan

I don't know how much or if at all this makes any weight difference as I have never weigh anything on the guitar. I for most part now use spruce for the neck block and tailblocks. I go a litte thinner when I can for tops, backs and sides. I do know one thing, I find different woods are heavier than others, so just make the parts and thin andcut out as much as I can and move on.

Ken that was a great post - very informative and thanks for bringing the playing style and intended music into the discussion - very important.

I had the sincere privilege of playing one of Mario's guitars last month in Ann Arbor. Mario is also building, or at least this one was built for bluegrass, mediums, great projection and if these were Mario's design goals he nailed it. The guitar was one of the finest sounding guitars that I have ever played.

Interestingly - it was also very light weight.

Alan my friend it sounds like you have a great wood combo planned. Aussie Blackwood (our Aussie friends prefer to call Black Acacia Aussie Blackwood and I am not going to argue with them....... ) and sitka should make a great OM and a light weight guitar is very possible with this combo too.

Every top is different so the suggestions that I am going to throw out here are what I believe to be a safe bet for you regardless of how stiff your top is and for an OM sized guitar.

top: .110 and you can thin it around the perimeter of the lower bout during final sanding. Thinning to .100 should be safe and help the top pump/move.

sides: .080 - .085 bend at .085

back: .085 - .090

Make your braces and X brace 1/4" wide and I like to see about 1/2" of height at the X intersection pre-cap.

I hope this helps.

This is a very good discussion indeed!

Ken's description of differing ways of building fits my thoughts very well also. I actually prefer figured maple necks, but the weight difference between one of those necks and an identical neck made from Spanish cedar is a large difference. A couple of ounces here and another there makes for a heavier guitar. I am also guilty of leaving the back and side wood a little thicker on woods that I have not built with before and I guess my mentality on doing this is just to be cautious about cracking or other problems later on?? My fears are probably unfounded but this has been one of my hangups when dealing with unfamiliar woods.

It is always interesting to see how others are able to achieve lighter weights in their builds.

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Reguards,

Ken H

I just unpacked a guitar kit from LMI and the heaviest bit of wood by far was the ebony fret board.

Interesting. I have been keeping track of the weight of the top and back plates, but not the whole guitar. I do try to build light, within reason, but also try to maintain proper strength. Anyway, this thread prompted me to haul the old kitchen scale out the shop and check up on the three guitars I have handy.

Englemann/Locust classical - 3#-4oz.
Redwood/ Cherry 00 (same size as classical) - 3#- 12 oz.
Eu/Mahogany Small Jumbo - 4#- 4 oz.

The cherry neck on the 00 doesn't seem to be adding al that much weight, considering that it has a heavy Martin style rod. The slot head and Waverly machines help.

The SJ has an Allied/Blanchard rod, but also Schaller M-6 minis with ebony buttons ( the buttons save the weight of two machines). It's a bigger guitar, of course.

It looks as though I'm not the weight saving champ! I think that some of the extra is probably in the neck block, where I use a fairly large 'chin' to support the fretboard end.

Sustain is an interesting thing. There are actually two ways to get more sustain; a heavier/stiffer top in the bridge area, to get a higher mismatch of impedance between the strings and the top, or a more efficient, and usually _lighter_ top overall.

When you pluck the string the sound output rises fast, and then falls off at some more or less steady rate. As long as that output curve is above a certain level you can hear the guitar. A large impedance mismatch decreases the output and the slope of the fall, so the level can stay above the threshold longer so long as the initial level is not too low. A more efficient top that is lighter will have a steeper falloff, but it can also get to a higher level, and it may, thus, stay above the threshold of perception longer. Jansson talks about this in his book "Acoustics for Violin and Guitar Makers" which you can download free.

There sure is a lot to think abut with these things!

Another datapoint:

OM, mahogany neck, body and blocks, cedar top, sitka bracing, 58% RH, 22˚C, 4 lb 0.9 oz (1840 gm). Finished in shellac and with 'mini' tuners which together probably shave off a ounce or two. However, it's got the chunky Cumpiano pattern top block which probably adds it back, and some.

Ian