Official Luthiers Forum!

Hi, I'm a new member and new guitar builder. I know that every answer will get 50 openions or answers but I would still appreciate some help.
My first guitar is, " OM-000 kit from LMI is Indian Rosewood back and sides, Red Spruct top.
Spruce bracing and end block. Tipical binding and trim"
Problem: Ordered kit with top glued up and supposedly thickness sanded. The top is currently 124 thousandths thick. Being new at tap tuning I am afraid its to thick and all I have read indicates it should probaby be about 80-85 thousandths thick for starters. I am very concerned as to the sound when finished sounding like MUD. Have emailed several knowledgable people in the business with no response back (of course). Have not gotten to the point of purchasing a finish sander for accuracy. Feel lost. Want to be somewhere in the decent sounding department with hopes of rich base and mellow sounding guitar. Could ruin an very expensive kit being a green horn. Could use your thoughts and help as I am dead in the water so to speak. Hope to leave this guitar for 5yr old grandson some day.
Thanks
W Brothers Guitars.

Howdy there Wendell! Nice to see another builder in the KC area.

.124" is indeed on the thick side, especially for an OM, and even more being red spruce. But .080-.085" is on the extreme thin side, and not advisable for a first build since it requires a good feel for stiffness, and different bracing than the standard X with diagonal tone bars... probably somewhere in the .100-.110" vicinity would be good, maybe a bit thinner around the perimeter.

For me, fingers are more useful than ears when it comes to thicknessing the top. Bracing stiffens it up so much, the free plate tap tone doesn't seem to mean much, although I do still tap on it because why not? Flex it with one hand at the tail and one through the soundhole, thumbs reached in as far as possible. Not hard enough to break it of course, but enough to feel how bendy it is. Just go by numbers and guessing at "good" tap tone and flex at first... after a few, you'll start to develop a feel for the range of stiffness we work in.

You don't need a thickness sander for spruce. Hand planes can make quick work of it, followed by a cabinet scraper to smooth out the plane marks. Although depending on whether the wood has much runout, it can be a little tricky to plane without tearing. I've had bad luck with LMI's top wood in that regard. Have to go up on one side of the plate, and down on the other, and it's tricky to get the center level without going across the line and tearing out in the other half. But it helps if you can get your blade really sharp, and take fine shavings with a very small mouth opening on the plane.
Always thickness from the back side. Small tears are much less noticeable inside the box

Good luck, enjoy the journey, and then build another one

Wendell,
I agree that .124 is on the thick side.
But not TOO thick. It's a good starting point and I'm sure there are lots of guitars out there that started at that thickness.
But if you want to bring it down a little bit and don't have access to the tools to do so, find someone who does. Like a local cabinet shop, wood shop, guitar builder, etc... Someone has a drum sander near you who could deal with your top in a couple minutes, especially for a small donation to their operation.

If you decide to do it yourself with a plane, make sure you get someone to show you how to sharpen it and set it up (if you aren't already familiar with the tool.) The potential of that tool is awesome, but few people ever use one that is ACTUALLY sharp. They take two or three swipes with one out of the box and get tired and disheartened by the results. The real deal (even a Stanley from Menards will do the trick) when properly working will do everything you want it to... just with a little more elbow grease than the power version.

Good luck on your first build.

Dave

thanks for the suggestions DennisK and Dave. I have been trying to find someone with a
drum thickness sander and no one will talk to me. Will keep looking. Oh DennisK, I was told no one else in the KC area was a guitar builder so glad to know that. I am in O.P, ks and would like to stay in touch.
Thanks both
w bros guitars.

Hey Dennis,

I would like to know what you mean by "different bracing" for the thinner top. For my first two, they are small parlors, and by this I do mean small, the lower bout is only 12-1/4". The plans I have call for a top thickness of .09", and I went a tad too far; both ended up around .083. Now assuming a tolerance on thickness of +/-.005", I'm only .002" out on the low side, which should be OK, or at least it seems to me.

I'm also a first time guitar builder here, so always open to the voice of experience! Both tops are stika sprice and have a decent feel, far as I can tell (neither feels flimsy, or like it will break if I breathe on it wrong.) So I was thinking i can either take a chance with the bracing as per the drawing, or perhaps make the braces a bit taller and/or thicker to increase the stiffness.

Any suggestions? I Have so much tied up in these already I would hate to start over.

Phil

_________________
Phil

http://www.oleninstruments.com

"Those who tilt at windmills are only considered insane by those who can't see the dragon."

What I meant by "different bracing", is something to support immediately behind the bridge. The diagonal tone bars can support one side of it, but not both, which results in a funky lop sided bellying close behind the bridge.

Symmetrical patterns like Somogyi's 4 part lattice in the lower bout, Edwinson's 3 fan braces, and Trevor Gore's falcate bracing work better to distribute the twisting force of the bridge over a larger area of the top. Even just using a larger bridge plate like Somogyi's might be enough to get away with diagonal tone bars, or using a large spruce bridge plate with a small hardwood plate just around the pins.

That said, you'll probably be ok with it as-is. Smaller spans require less stiffness, so especially if those are 12 fret necks, that reduces the bridge to tail span by quite a lot compared to an OM. There's still a chance you could get the localized deformation right behind the bridge, but I haven't built a steel string parlor yet so I can only make educated guesses. The only time I got the thin top bubble was with a 16" lower bout. That guitar still sounds great though. It just looks funky and the action is a bit high. I need to adjust the neck angle on it.

My most recent one is OM-ish size with a sitka top in the .080-.085" range, and large bridge plate with lower bout lattice. No structural issues, and excellent bass, but the trebles sound like crap