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Bowed Lutz Spruce Top - Do I need it flatten it before use?
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Author:  longdrive55 [ Tue Feb 08, 2011 3:36 pm ]
Post subject:  Bowed Lutz Spruce Top - Do I need it flatten it before use?
Hi All,

I just got a Lutz spruce top and one of the boards has a bow across the grain (across the short length of the wood). It's bowed about 1/8" or so.......maybe a little less.

Do I need to try and flatten this before I can join it/sand it? If so, what's the best process?

Thanks,

Erik
Author:  Jim Watts [ Tue Feb 08, 2011 3:48 pm ]
Post subject:  Re: Bowed Lutz Spruce Top - Do I need it flatten it before use?
Just sticker with a little weight on it and let it acclimate for a while and you should be fine.
Author:  Shane Neifer [ Tue Feb 08, 2011 4:00 pm ]
Post subject:  Re: Bowed Lutz Spruce Top - Do I need it flatten it before use?
Yup, what Jim said!

Shane
Author:  longdrive55 [ Tue Feb 08, 2011 5:08 pm ]
Post subject:  Re: Bowed Lutz Spruce Top - Do I need it flatten it before use?
Thanks guys.

I have another question regarding prepping the top to be joined.

If I look at the individual pieces of wood, the thickness of the two boards varies quite a bit:

Board #1
.198 (at the joining edge) .278 (at the outside edge)

.158 (at the joining edge) .238 (at the outside edge)

Should I thickness sand the boards individually to try and get them to a consistent thickness of around the .150 before joining the 2 halves or should I just joint the edge and join them with their current measurments........then thickness sand them together as a unit?

Thanks again,

Erik
Author:  Mark Groza [ Tue Feb 08, 2011 5:14 pm ]
Post subject:  Re: Bowed Lutz Spruce Top - Do I need it flatten it before use?
longdrive55 wrote:
Thanks guys.

I have another question regarding prepping the top to be joined.

If I look at the individual pieces of wood, the thickness of the two boards varies quite a bit:

Board #1
.198 (at the joining edge) .278 (at the outside edge)

.158 (at the joining edge) .238 (at the outside edge)

Should I thickness sand the boards individually to try and get them to a consistent thickness of around the .150 before joining the 2 halves or should I just joint the edge and join them with their current measurments........then thickness sand them together as a unit?

Thanks again,

Erik

You could start them both out at .150 or glue and thicknes just once. It's up to you as both ways work.
Author:  longdrive55 [ Tue Feb 08, 2011 5:21 pm ]
Post subject:  Re: Bowed Lutz Spruce Top - Do I need it flatten it before use?
Thanks again. You guys are great.

This will be my first time using a thickness sander, so I want to make sure I'm sequencing correctly.

Couple more questions:

1) Is it safe to inlay my rosette and cut my soundhole then thickness sand to final dimensions?
2) Can I run the thickness sander over the rosette to get it level with the board or should this still be shaved level with the top before I go to final thickness sanding in the drum sander?
3) Should I sand to final thickness on one side only or take a little off on both sides to get down to final thickness?

Thanks again,

Erik
Author:  Mark Groza [ Tue Feb 08, 2011 5:58 pm ]
Post subject:  Re: Bowed Lutz Spruce Top - Do I need it flatten it before use?
longdrive55 wrote:
Thanks again. You guys are great.

This will be my first time using a thickness sander, so I want to make sure I'm sequencing correctly.

Couple more questions:

1) Is it safe to inlay my rosette and cut my soundhole then thickness sand to final dimensions?
2) Can I run the thickness sander over the rosette to get it level with the board or should this still be shaved level with the top before I go to final thickness sanding in the drum sander?
3) Should I sand to final thickness on one side only or take a little off on both sides to get down to final thickness?

Thanks again,

Erik

I do the rosette after i thickness sand to lessen the chance of sanding it to far. When you thichness sand swap sides as you go to get the same amount off both sides. ;)
Author:  Dave Fifield [ Tue Feb 08, 2011 6:00 pm ]
Post subject:  Re: Bowed Lutz Spruce Top - Do I need it flatten it before use?
1) Yes, if you only thickness the soundboard by taking material off the back of it!
2) No. Under no circumstances should you use the thickness sander on a rosette IMO. Level the rosette using a scraper, not sandpaper, since the sandpaper will tend to remove more of the softer soundboard material than harder rosette material. Once level with the soundboard, you should finish sand the front by hand (with the sandpaper wrapped around a wood block), then only thickness it by removing material from the back of the soundboard.
3) Off the back of the soundboard only IMO. Obviously, once the braces are on and the soundboard is glued to the sides/kerfed linings, then if you need to remove more material you will have to take if from the top, but try to avoid this.

HTH,
Dave F.
Author:  Ken Franklin [ Tue Feb 08, 2011 8:08 pm ]
Post subject:  Re: Bowed Lutz Spruce Top - Do I need it flatten it before use?
I think that how you thickness the top depends on how thick the rosette material is. Ideally you want the rosette to be about half the thickness of the finished top thickness. That may mean that you need to take some off of the rosette side and some off of the back side of the top. The problem with just taking it off the back side is that thick rosette material might leave too little spruce behind it. I don't have any problem leveling my rosette with my Jet thickness sander down to 120 grit. Then I sand by hand with a wood block. Make sure you leave a little extra thickness for the finish sanding. It's not a bad idea to practice on some pine before you do your first top.
Author:  Shane Neifer [ Tue Feb 08, 2011 8:42 pm ]
Post subject:  Re: Bowed Lutz Spruce Top - Do I need it flatten it before use?
Erik,

I would first thickness sand the backs of both pieces until you have them both the same thickness. You can leave a few small saw marks but have them substantially clean. Then take a light pass off the face of the boards. Then joint the edges and glue them up. I then sand the face so it is clean and level and then thickness to .140 - .150 and then install the rosette. Once the rosette is installed I remove most of the excess rosette material with a cabinet scraper and then I do a very light pass of the face through the thickness sander. Once I am happy with that I sand the top to my final "rough" thickness (still need to finish sand and/or cabinet scrap so leave a few thou for that) by removing material only from the back of the top plate. I hope that helps!

I need to say this though, I suspect that this wood did not come from me (it's OK....REALLY!) as my sets are not that uneven in dimension as I resaw from a fence.

Good luck and keep us posted on your progress.

Thanks

Shane
Author:  longdrive55 [ Tue Feb 08, 2011 11:00 pm ]
Post subject:  Re: Bowed Lutz Spruce Top - Do I need it flatten it before use?
Thanks for all the responses guys. You've helped this newb a lot.

Shane the top was not from you. It really isn't that bad, I just didn't know how to deal with it cuz it's the first top I've got that's bowed. I've got a couple of other tops (Carpathian) that were pretty uneven dimensions too. Everything should clean up well. I really can't complain, cuz I didn't pay much for any of these and the general quality of the wood is pretty nice.

Thanks again all.

Erik
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