Official Luthiers Forum!

A thick back would influence just on weight or the sound would be dull also?

Sent from my GT-I9505 using Tapatalk

What Ed said. 0.2" is much thicker than you want. Like more than twice as thick depending on the wood and size of the guitar. yes I made my own thickness sander and made it big enough that I could run jointed backs through. As the plate gets thinner, its stiffness decreases faster than the thickness. As you approach the thickness we want, the wood is flexible enough to be held flat with little effort so you can get it down to your desired thickness while it is pressed flat, it will rise up again when you relive the pressure but the braces and back geometry should be more than up to the task of holding it in shape. You should be able to do that with a plane also but you may have to use wedges or supports to get it closer to flat while it is thick. Essentially the drum sander did this for me by taking LIGHT passes, the high spots were knocked down while the wood was still fairly stiff. Flipping it over then took off the opposite high spots on the other side. As I continued, the high spots became flats that helped register in the table for the next pass averaging out the cup a bit and slowly the stiffness decreased allowing the drum to press the plate more and more into a flattened state each time.

Ideally, you would only remove the high areas from both sides leaving the middle 0.1ish" perfectly flat on both sides but if the cup isn't too bad, that is not strictly necessary and you can rescue a board that is too thin for its cup. . .

oops, I see you were responding as I was typing. Good to see you aren't going to leave it that thick.

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

I don't see much here that bothers me. Join it while thick. Then lay it under something heavy in a humidity controlled environment (your house). Go find something else to work on for a while. Thin it down to 0.10-0.12 and brace immediately. Keep braced wood pressed in a radius dish (inside house) till you are ready to join to sides. None of this is ideal, but none is critical either. Your first guitar will be a burner.

Thanks! There is a guy who irons the wood with a moist cloth, i wonder if that would help as well

Sent from my GT-I9505 using Tapatalk

Probably not the best practice but i used the wifes steam cleaner(she doesn't know) on a thinned back that was bowing after i took it out in the sun.. (doh)..braced it up and it worked a treat ..all will be fine

If...your wood is totally acclimated moisture wise (otherwise you are chasing your tail), I have used my thickness sander to square cupped wood.
1) carefully measure the cupping. Assuming .4 inches, make a .4 inch thick shim the length of the board and double side tape it to the cupped side. Then with light passes keep running it through the sander shim side down till you are sanding across the full width of the board. No you can flip the board, remove the shim and sand that side down till it is sanding across the full width of the board. You will now have two pretty flat sides parallel to each other.

The problem is, this will take the thickess of the cupping off of each side reducing the board thickness by .8 inches! It's really only practical for lesser cupping unless you start with a really thick board.
Mike

Keep in mind that a thickness sander will not remove the warp the same way as a planer. the piece will be held flat by the guide rollers and sanded equally across its width, so when it comes out, it will still be warped, just thinner. (but easier to conform onto the braces/sides) A planer will selectively remove the high points, either in the middle or edges depending on the pass.

Actually, David, Mike Imbler's method works just fine. I'm pretty sure there are no guide rollers on thickness sanders, but the shim will support the cupped wood, and keep it from flattening under pressure from the sanding drum. Flattening with a thickness planer will work, but only if the wood is thick enough to resist the presssure from the guide rollers, or if you attach it to a carrier board with a shim under the cup. If you try to run a board under 1/4" on a thickness planer, wear a face shield and a jock cup, or risk being a one eyed soprano.

Alex

_________________
"Indecision is the key to flexibility" .... Bumper sticker

Hi Alex, My Jet 10/20 has guide rollers that will flatten thin wood before it goes under the sanding drum. Don't know about others.

_________________
Steve Smith
"Music is what feelings sound like"

He built his sander. So I suppose he made it not to flatten the wood before sanding.

Sent from my GT-I9505 using Tapatalk

My thickness sander (Jet 22/44) has guide rollers. So did my 10/20. Lay a lightly damp cloth on both sides, heavy board on top plus more weight, and forget about it for a month. If that does not work, make barrel staves out of it.

.... Or a Lute

I have two Performax sanders while, the in and out rollers keep the work compressed againt the conveyor there is not enough pressure to flatten a cup in all but the thinness board --- its the drum that does the flattening. So in that regard a simple shop built will be just as effective.

_________________
Ken Cierp

http://www.kennethmichaelguitars.com/

If it works, great! If not, you have gained experience. Don't let it discourage your first build.
Good luck!
Dan

_________________
wah
Wah-wah-wah-wah
Wah

As Alex points out, that is why my method uses the shim. It works.
Mike

Ronaldo, I don't see where you are from and what your climate conditions are, but that wood is problematic. As it is your first guitar, use it if you want, be aware that as someone else said, it will probably be a "burner", if you will even finish it. You will learn a lot of things trying, one is about flatsawn wood. It is not a good wood for guitars. Those that use it correctly will put the flatsawn part out at the edges of the instrument with the quartered part in the center. Doesn't look like you have much of any of the wood that is close to quartered. They will also use well seasoned wood. Depending where you live, I would consider looking for some quartered wood. Many local woods will work nicely if they are quartered and seasoned.
Another is about keeping your shop humidity controlled. It is essential. You can't build a stable guitar without it.
Two tenths of an inch is roughly twice as thick as it should be...

Thanks,

I am from Brazil, the place where I live is very dry (capital) , 20% r.h. right now.

I cannot find any local wood sellers that sell quartered sawn wood around, the only guy I know who sells lives about 900 miles away, and the shipping would be very expensive. That's why I bought those wood. I do not expect the very first to be a good instrument, as you all have said, it is more to gain experience. In my view, it is better practicing in a not so good wood than destroying a piece of spruce/maple/jacaranda wood/mahogany.

All the best!

Sent from my GT-I9505 using Tapatalk

Brazilia must be pretty humid at times too, yes? Or is that desert?
If you are serious about building, it would be good to try to find some stability in the place you are building. Humidifiers and maybe also dehumidifiers are required.
Using the wood and learning your skills is a good idea, but expect problems without humidity controls.
Good luck!

Okay, I see what you're talking about with the shim. I was under the impression you were talking final thicknessing, at which point my sander's guide rollers will easily flatted a warped piece of wood near final thickness. After that, I would depend on bracing to hold position, and its not under high tension. Interesting discussion in any case, on different ways to handle warp. Good luck, and definitely don't get discouraged. There's plenty of other stuff to pull hair over!

Most of the times it is dry. But from January to April it is moist.



Sent from my GT-I9505 using Tapatalk

If I wanted to use that board I would be inclined to rip it down the middle, wet one side to take the residual cup out of it (as Ken mentioned) and then resaw both pieces to get twice as much usable wood from it. You could make a four piece back, which if carefully done would look like a two piece back.

Thanks. I would need a band saw to saw the parts in the half with a usable thickness, wouldn't I?

Sent from my GT-I9505 using Tapatalk

Resaw a cupped board that is .35" thick? To make 4 useable pieces? Yes, you'd need a bandsaw and a whole lot more. To be remotely successful, assuming u had a bandsaw with a resaw blade (thin kerf), and appropriate drift adjusted fencing, you'd need to glue the board to a true and flat backer board. And that would sacrifice some of the wood. I don't remotely believe u are going to end up with a book matched set. If the goal was book matched set from that board, maybe time to reassess. Otherwise, solid back. What am I missing here?

Ps: not solid back, two piece back, just not book matched.

That's what I thought. Sisyphus work.

Sent from my GT-I9505 using Tapatalk

What your missing is ripping it in half first(which will reduce the cupping in half), then wetting to remove that remaining cup. Then you are resawing an essentially flat piece, and two usable pieces from a 0.35" thick piece is possible. I think I could do it successfully, and have no doubt that Clay could do it, but it would not be easy!

_________________
A man hears what he wants to hear, and disreguards the rest. Paul Simon

Cutting a 0.35" piece in half is reasonable. Should not be too hard to get two 1/8" slices assuming your resaw setup is reasonably good.

_________________
Steve Smith
"Music is what feelings sound like"