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I am going to buy a serviced classical guitar kit from lmii. I would like to have the sides already bent. Whats a good way to cut the taper for the back on allready bent sides?

When I worked with pre-bent sides I got them close with a small block plane with the sides clamped in a mold.

(I have also cut them close on my bandsaw)

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I glue the neck and tailblock down, then kerf and glue the sides down onto the top and blocks (no mold). Then I work them down with a block plane and finish with a sanding board.

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Old growth, shmold growth!

Bandsaw close to your line, then a very sharp plane. Fun stuff.

easy to do:
Mount the sides in the mold.
Cut blocks to desired height
glue in the blocks
mark profile with masking tape (some day I am going to figure out how to include the desired radius)
rough cut with a fine blade in a frame saw (safer than using a band saw or table saw)
bring to the line with a block plane

-jd

You can do it any of these ways. However, I think the safest way is to do the entire process with your block plane. It's fun and easy. With a sharp plane, it probably won't take fifteen minutes to get the sides planed down to your line. One other proviso: You need to read the grain of your sides and plane with it, not against it. In most cases, you'll probably be planing from the waist area towards the neck block. With some wild sets of wood, you might need to plane in the other direction. You'll know immediately. I bet you'll enjoy the process.
Patrick

in simple term - just start building the guitar - top side down - glue your sides to the top and the tail block - with the neck attached - then use the plane to bring your sides down to size. I would not try trimming them unmounted.

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It's this new idea from recent decades that everyone gets a participation award. - MUX

Doing that at this very moment I like my sides at constant width when bending, so I always have to taper after gluing to the top (I do Spanish style with individual lining blocks, aka dentellones). I do saw the sides to about 1/8" wider than the tail block height before bending, so there's not too much to remove.

So, after I get the sides glued to the top, mark approximate heights at various points along the sides (just calculating averages between the height of the head block and height of the tail block). Plane to about 1/8" above those marks, laying it on a flat surface as it gets close, taking down the high spots until it lays gapless on the table at about 1/8" above the headblock and tail block. I use my Stephen Boone finger plane, but block plane works too.

Then mark all the way around about 1/8" below the edge, so I have a clear reference. Plane some more, taking it down flush with the blocks, and leaving it higher at the waist for the dome of the back (1/16"-1/8" depending on how tight of a radius I'm going for on the back). Glue kerfed linings slightly proud of the edge, and plane them flush with a slight angle to support the dome, and you're good to go.

As mentioned: a bandsaw works nicely to taper already bent sides if a lot of material needs to come off. Leave a couple mm or so, then use a small hand plane to bring to design profile.



Joe

I read an interview with Eugene Clark in which he describes a simple jig that really helps this process. As mentioned above, a sharp block plane takes the sides down close to the final depth once they are glued to the top in the mold. Then a simple guitar-shaped board is placed like a lid on the box allowing you to see high spots. The board need only be slightly larger than the outline of your plantilla with notches allowing it to fit around the heel and end block. Once the board sits flat you're pretty much done.

After trying this technique to put the taper in, I glued my lining a smidge proud of the edge. I then used a radiused sanding paddle to shape the linings/blocks to accept the dome of the back. I'm still finishing off guitar #1, but this approach made fitting the back and sides a cinch.

Jake.

I always cut the taper after bending. I just glue in the blocks and use a chisel and block plane to cut the taper. Use a level to make sure both sides are the same height. Its really much easier than it sounds