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I bought a japanese style plane cheap (that is all they got here in Taiwan anyways... I wish I could get a metal soled Western style plane) and the oak plane body appears to have a slight curve to it when I placed it on a thick sheet of glass. Is there a right way to true the sole to insure that its dead flat? I don't have a jointer (that would solve the problem) so I plan on placing a piece of coarse sandpaper on the glass and attempt to lap the plane body...

any thoughts?

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Tai: Assume these are the pull type planes. Don't have any experience with these but have made wooden push planes and will give some suggestions. The blades should be left in the planes with the same tension as if being used normally but with the blade raised to ensure no contact between blade and abrasive. This makes sure you have a flat sole under tension compared to a flat sole without tension that distorts when you do put tension on the blade. Suggest that you use abrasive with adhesive on the back to stick to the glass plate. Think this will be easier to use then loose paper on the plate. Good luck and let us know how you make out.
Tom

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A person who has never made a mistake has never made anything!!!

When you say the body has a curve, do you mean a hollow?
I don't know what size plane this is, but on a common Japanese plane
(hira-kanna) there are two touch-points: at the end closest to you,
and just before the mouth. the area between is hollowed slightly, as is the
the area after the blade; this is normally done with a scraper plane going
across the grain. You *can* flatten a sole with sandpaper and glass, though
it's not as easy as it might seem. And a flat sole is ok, though not ideal.
Do you have a straightedge that's as long as the body on the diagonal?
The leading edge should be flat (crossgrain), as should the area just in
front of the mouth (this is critical), and they should be coplanar. Aft
of the blade be sure there is no 'bump'- normally this area is hollowed
by the maker. There's more but this will get you started, assuming I've
been clear enough.

It looks like the entire plane body without the blade installed is convex in the bottom, not hollowed.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Has the blade been fitted to the body (dai) already, will it move into cutting
position with light to moderate hammer taps? How much convexity are you
seeing? It's quite unusual for even an old or cheap dai to go convex in length-
this is more common looking across the dai's width. Either way, it needs to
be flat at the least. Your sandpaper- flattening idea will work, assuming the glass is flat (and the substrate too)- go slowly, mark the high spots with pencil,
take a couple of light passes, check with straightedge. You might consider
using a sharp card scraper and straightedges rather than sandpaper-
also, *avoid removing wood from the mouth area* as much as possible.