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So I’m going to start on a small body ladder braced guitar and for the top I’m using mahogany. I’m relatively new to acoustic building so I’m not sure if I should treat the hardwood top differently or not when it comes to target thickness vs spruce. With my spruce tops I shoot for just a hair shy of 1/8” with my plane and do some cleanup sanding and scraping.

Should I go thinner with a hardwood? What is your target thickness when dealing with hardwood tops? I know all about tap tone and each case is different and I go through the process of tapping as I build, but honestly I’m not experienced enough to be comfortable going off of tap tone. Basically my process is bring the tops down to a target # and if it sounds dead or dull I massage a bit more off. That’s the extent of my tap tuning. I go through the process anyways for the experience. Pretty much the same with tuning after bracing.

First off, I've never built with a hardwood top. I should just stop here I suppose, but, mahogany isn't any stiffer than spruce (similar), but it is denser. I might consider going a little thinner to keep the weight down and making the braces a little taller to compensate. Just a thought experiment on my part. I'll be interested to see what those who build with hardwood tops have say.
Like I said, no experience with hardwood tops.

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Jim Watts
http://jameswattsguitars.com

Well Jim I appreciate your honesty by being upfront in your lack of experience with hardwood tops and presenting your thoughts as thoughts not experience. The worldwide web could use more like you. I agree with you slightly thinner top with taller bracing makes sense in my minds eye.

I've built one guitar with a hardwood top--an all mahogany L-00 style. I started out taking the top to the same thickness off the sander as I would with a spruce top. As I worked it, it did end up a little thinner, but not by a whole lot. I was using taller braces than I would with a Martin style guitar just because it was more in the Gibson style with narrower taller unscalloped braces, so I can't really say what role these played in the whole thing. The guitar came out sounding really nice--it's my main player these days.

Dave

As Jim says, mahogany, like most hardwoods, is not much stiffer along the grin at a given thickness than spruce, but the hardwood is denser. If you work the top to a similar stiffness hardwood will be heavier. Since there's only a limited amount of horsepower in a plucked string you tend to end up with less treble in the sound and less power with a hardwood top. I'm not a big fan of making a thin top with heavy braces to cut down on the weight; IMO a lot of the 'clarity' of the high end comes from achieving the proper balance between the stiffness of the top and bracing. I don't like the sound as much with the thin top.

This will be a small body instrument modeled after the LMI plans as they call it a 20’s l-0 with a sort of H or A ladder bracing. No doubt spruce for the bracing still kicking around which ones will get a radius it’s been a bit since I looked the drawings over but I do not recall them indicating a radius for anything but no doubt from looking at existing examples online they came with a radius. The top as I said will be mahogany, back and sides walnut, most likely a hog neck but haven’t decided. I’ve not seen that combination before so not sure what exactly to expect but looking forward to it.

This will be an experience / experiment for me I’m not a luthier just a tinkering fool with much curiosity. Many of you do this for a living I do this for therapy I think! It keeps the mind busy and distracts the mind from unpleasant things I guess. I do most all the work by hand it adds to the intensity and struggle which in turn produces small victories and defeats in each step that somehow make me happy. It also adds much appreciation for the beauty of string instruments and appreciation for the skill of all those who do this work / art well.

I only built a few mahogany topped guitars and that was before I knew what I was doing, well I still don't know what I am doing but I have gotten better... I built them the same as a spruce top guitar.

I also started building thin topped guitars and I have been getting thicker ever since. I think I am starting to agree with Alan that the thin topped guitars are not as good. Having said that if you do manage to get the bracing right on a thin top guitar then it seems to work exceptionally well it's just really hard to get it right and perhaps just a lot of luck.

Having said that 1/8in is pretty thick for a small body guitar. On LG type guitars I have gone down as low as .09 on a stiff top.

Today I use deflection. I do have plans to build some very small all mahogany guitars in the future and I will build those tops to teh same deflection as spruce with the theory that they should at least share some similar structural qualities.

My mahogany topped L-00 measures out at .093" for what it's worth.

Dave

I'd make it about the same thickness as spruce. Whatever stiffness feels right. Ladder bracing relies more on the soundboard itself for stiffness compared to X bracing, and small guitars have a lot of leeway before mass becomes a problem.

It's an old thread, but you might find it useful reading...

http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=43138#p569628

The guitar is built on a classical body shape, which is similar in size to a Martin 00.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

I have a 1927 Martin Model 2-17 mahogany guitar on my bench right now. The Model 2 is a fairly small Martin X-braced all mahogany guitar. This guitars mahogany top is 0.1125 “ thick at the soundhole. The guitar is not bound and the top thickness at the outside edges is very close to 0.125”. Bracing is scalloped.

For your interest.

Cal

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Remember, there are no stupid questions, only stupid answers!

There was a brief discussion of mahogany tops at MIMF a while back

https://www.mimf.com/phpbb/viewtopic.php?f=3&t=6640

As I stated there I have built one all mahogany guitar, 00 sized with fairly deeply scalloped X bracing. My top ended up at 0.120 and the guitar is plenty loud and punchy. From the thread is sounds like others have gone a bit thinner.

I have also built and worked on ladder braced guitars, but not mahogany. You need to think about bracing and top thickness with respect to the kind of bridge you will be using - you'll have more rotational component with a pinned bridge, more down force with a tailpiece.

I have not considered using a tailpiece my original intent was to go with a pinned bridge. I do not see many flat tops with a tailpiece. What do you recommend on top thickness & bracing for pinned vs tailpiece? Is taller bracing better for downward force?

Slim, remember that a pinned bridge puts a torque around the cross axis of the bridge, pulling the lower bout up and pushing the area between the bridge and sound hole down. I've always thought that the Martin style X brace was a stroke of genius (or darn good engineering) - it puts the strongest part of the bracing in the weakest part of the top and still supports the lower bout. Ladder bracing is great for across the grain strength but very little to counter that rotational force. Ladder bracing does work very well for guitars with tail pieces since the bridge only has a perpendicular component. Lots of great ladder braced guitars (Stellas, SelMac's) have tailpieces and work very well. Archtops and bowed instruments also have tailpieces and floating bridges, but usually not ladder bracing.

When I see ladder bracing used on flat tops with pinned bridges it is frequently some of the lower line instruments - old Harmonys, student model Gibsons, other budget guitars. They have a characteristic sound and are frequently very good for roots music. There are a few modern builders making ladder braced guitars with both pinned and tailpiece bridges. You probably should look at some of them.

I have built exactly one ladder braced guitar, it is a long scale 12 string patterned after the 1930's Stellas. It has a tailpiece and a fair amount of vertical pressure on the top, but has held up and plays well. I have also built exactly one mahogany topped guitar (which was your original question), as I said before a 00 sized X braced instrument patterned after the great little Depression era Martin 17 series. I have also worked on several inexpensive ladder braced guitars (Harmonys, Gibson LG-1) which have needed neck resets and bridge repairs.

If you have plans or a particular model in mind by all means build it. My experience is limited but I am happy with both the 00 and the 12 string. Good luck

Yeah the plans I have do not have what I consider typical ladder style bracing but more of an H or A type pattern opposed to bracing running from rim to rim parallel or crossing over over the bridge like typical x bracing. Actually the pattern seem pretty unique or at least to me when compared to the modern string patterns. I would post a pic of the plans but don’t know if LMI would like me doing that.