: . .Is there
: a grading system for other plywoods with hardwood exteriors that implies
: minimal voids and scraps?

I think you already know the answer to that: YES.

The rating system that we commonly see is the one which specifies wood "suitable" for marine use, and are sold with a number (eg. BS 1088) showing their conformance to certain specifications. You know about THIS rating because you are shopping for wood which is less expensive, but which can serve as an alternative.

Manufacturers, who have tight control over the construction process for plywood, can make the product without voids. These are sometimes stronger panels and these are sold at a premium. There are also lumbercore and MDF core plywoods. The cores are graded from J to M with grades K and L being in the middle. J grade core is probably as void-free as you'll find, while M grade will probably have some pretty big voids -- but if you can cut around them, or live with them . . .

By looking for panels which are rated for their strength you increase you chances of finding panels with excellent cores. Aircraft grade plywood would fall into this category.

If you can think of a special purpose plywood, you'll probably find that it was made with a very good core! The inexpensive construction grades we see at home centers, which may not be load rated, are not going to be the best that is available -- but you may find some pieces that are excellent, and many more that are well suited to your use, and at an excellent price, if you don't mind discarding a bit of waste.

Some sites for information on plywood grading:

http://www.forestplywood.com/grading.htm ( that site also has a nice glossary of terms at http://www.forestplywood.com/glossary.htm )

http://www.woodmagazine.com/woodbasics/vendors/mcfeely/pages/aboutplywood2.htm

http://www.iwpawood.org/woodref.html Through this site you can get books of grading rules for international hardwood plywood products. Of particullar interest is their book on lauan doorskins -- a well mentioned resource in our field. The free, downloadable, version must be for members only, though.

http://www.sloanswoodshop.com/grading_wood.htm This guy has a good slant on the whole grading process. He points out that grading is done by human eyes, and there will be some variability. Unfortunately, the plywoods he stocks are in small pieces, probably for use by the scrollsawers he markets to.

http://www.mainecoastlumber.com/plwoodgrades.html This site has 4 pages that appear to be scanned images of the grading rules of the American national standard for hardwood and decorative plywood (from the Hardwood Plywood and Veneer Association) They also ahve a tollfree 800 number to call for information on their grading. (This appears to be a Maine lumberyard, not a plywood information site, so I wouldn't suggest calling about grading standards in general. They are in businees to sell the stuff, not to judge it.) They have 10-foot panels (120 inches) and thin ones (1/8th inch), and marie grade panels in several species, so they might be a good supplier of speciality plywoods for someone. And it says they deliver over a 5 state area.

http://www.phillipsplywood.com/plywood_cores.htm On the other side of the country, they offer a service of making you the plywood you want to whatever specs you supply.

Here is a group that you might calland chat with:

Hardwood Plywood & Veneer Association (HPVA)
Includes former Fine Hardwood Veneer Association
1825 Michael Faraday Drive
P.O. Box 2789
Reston, VA 22090
Telephone: 703-435-2900
FAX: 703-435-2537
e-mail address: hpva@hpva.org
Web Address: http://www.hpva.org
Contact: E.T "Bill" Altman

Their web site lists books on gradign standards, for $25 to $20 as well as a hardwood plywood self-study course for $30. This may be a bit more than I want to get into, but someone might be interested.

http://www.mcvicker.com/twd/gwdi97/page003.htm This has a lsit of other websites that may give you some information on the grading process.

Hope this helps.

PGJ