Plywood Plates

bigolbassguy · #1 09-01-2010, 08:48 PM

Any thoughts on DIY plywood basses? I've been thinking about it lately, mainly because of the prohibitive cost of bass tonewood. How are the forms for the plates constructed? How, exactly, are the plates molded? As always, pictures - educational resources would both be much appreciated.

powerbass · #2 09-02-2010, 07:07 AM

There are some threads about this. One way to do this is to have a male/female mold or form. Thin plywood is heated probably w/some steam added then it is pressed in the mold which is probably also heated. Veneer doesn't like to bend in 2 diretions but it maybe done if it is softened first

bigolbassguy · #3 09-04-2010, 11:53 AM

I've been searching old threads, but haven't been able to find what I'm looking for. No luck on Google, either. As a side-note, I really like the way Upton's ply basses look. Really crisp. I'd like to achieve a comparable result.

Bill Bentgen · #4 09-04-2010, 06:12 PM

I remember seeing some old pictures of the Kay factory somewhere where the construction process was described. There was a giant press with the two halves of the mold. The individual layers were placed in the press with glue between each layer. I think there was heat involved. Didn't look like something I could duplicate in my basement.

bigolbassguy · #5 09-05-2010, 12:11 AM

I'm getting that impression. Not a lot of room for a giant hydraulic press/steam iron in my shop. I'd still like to have a detailed understanding of the process, though. Is anyone else interested should I be fortunate enough to find the info?

George700DL · #6 09-05-2010, 08:47 AM

Quote:

Originally Posted by bigolbassguy

I'm getting that impression. Not a lot of room for a giant hydraulic press/steam iron in my shop. I'd still like to have a detailed understanding of the process, though. Is anyone else interested should I be fortunate enough to find the info?

I'm interested. I enjoyed carving my top, but the idea of making a plywood bass is attractive to me as well.

George

vejesse · #7 09-05-2010, 10:54 AM

Engelhardt sells individual plywood tops and backs. Or how about a carved top with a flat plywood back?

xwtb · #8 09-05-2010, 01:44 PM

If zeytoun can induce a compound curve in a sheet of .25 plywood, (Acoustic/Hybrid Upright Bass Project ) with wet towels and clamps, surely it would be possible to do the same to a sandwich of veneer. Applying tons of pressure to a mold shouldn't be all that tough, given two planes to work between that are reasonably unmovable and more or less parallel. Floor and ceiling of an apartment parking garage, for example. Then house jacks or joist levelers, with a grid of beams to distribute their pressure.

Please keep us posted on what you discover.

L.F.Miller

Big B. · #9 09-05-2010, 03:22 PM

How about a vacuum press and a male shaped mold? You can fit the bag to the size of your project. I guess it would depend on the thickness of your plies.

bigolbassguy · #10 09-05-2010, 07:05 PM

Quote:

Originally Posted by Big B.

How about a vacuum press and a male shaped mold? You can fit the bag to the size of your project. I guess it would depend on the thickness of your plies.

I'd probably be using 6mm aircraft grade laminates. Not sure they will bend easily.

Quote:

Originally Posted by vejesse

Engelhardt sells individual plywood tops and backs. Or how about a carved top with a flat plywood back?

I've considered going the hybrid route + joining a 3-piece top to save money, but my graduating caliper is only large enough for a cello. :\ Every time I buy a new tool, I suspect my wife secretly packs a few more of her belongings.

bigolbassguy · #11 09-05-2010, 08:00 PM

Quote:

Originally Posted by Big B.

How about a vacuum press and a male shaped mold? You can fit the bag to the size of your project. I guess it would depend on the thickness of your plies.

The more I think about it, the more this looks like the way to go. I have most of the things I need to build an AVS system.

What about a vacuum bag made from .60 mil epdm roofing rubber? It would be strong enough to handle just about anything without rupturing + it could be shaped neatly to the project + used again and again...

Big B. · #12 09-05-2010, 08:41 PM

The good thing about a round top plate is that there are no corners for anything to catch on. A bass top is the perfect shape for using a vacuum bag,just a large flat surface with gradual relief. I think it would take a tremendous amount of pressure to rupture the bag. Maybe if you pulled the air out of the bag slowly and give the plies time to bend it would go more smoothly. Just cranking down all at once may not be good idea.

George700DL · #13 09-05-2010, 10:52 PM

Quote:

Originally Posted by bigolbassguy

I'd probably be using 6mm aircraft grade laminates. Not sure they will bend easily.

I've considered going the hybrid route + joining a 3-piece top to save money, but my graduating caliper is only large enough for a cello. :\ Every time I buy a new tool, I suspect my wife secretly packs a few more of her belongings.

I made mine exactly that - plywood back and ribs, carved top. Made my own calipers.

bigolbassguy · #14 09-05-2010, 11:20 PM

Quote:

Originally Posted by Big B.

Just cranking down all at once may not be good idea.

If I go forward with this idea, I plan to leave excess material on the plates and trim them to shape, so corners might actually be an issue. You think that the standard vacuum bags would be strong enough the handle the work?

Big B. · #15 09-06-2010, 03:19 AM

I would either round off the edges or use some packing material to pad the corners. I would think a regular bag would work. (famous last words!) Keep in mind that I have not done this before but this seems to be the best way to replicate a factory press. I would do some serious research on my glue.

powerbass · #16 09-06-2010, 04:53 AM

I have used vacuum presses quite extensively for veneering and creating bent laminations for custom furniture. Vacuum pressing a top/back plate would be a relatively inexpensive way to try out making your own. First of all a bass plate is a compound curved object so you would need to carve a male form. The easiest way to do this is to use rigid foam insulation the kind used in house construction. This can be carved to your bass top shape and would be strong enough to handle the pressure. To my knowledge vacuum pressing creates 30lbs PSI. The commercial bags are quite strong. I have mostly used this company, (they sell Unibond Glue which is great for veneering) their systems are quite good, though you could make your own pump cheaply, buy a bag.
https://www.vacupress.com/vacuumveneering.htm. Veneer is cheap, if you soften the veneer first then place in the press and if your plate shapes are not too extreme this SHOULD work. I have yet to try this so I am assuming it would work. My experience has been with single plane curves, not compound. As for sharp edges the rubber roofing material mentioned would work well
http://www.woodcraft.com/search/sear...FdJL5Qod6DmA2Q

bigolbassguy · #17 09-06-2010, 08:47 AM

Quote:

Originally Posted by powerbass

I have used vacuum presses quite extensively for veneering and creating bent laminations for custom furniture. Vacuum pressing a top/back plate would be a relatively inexpensive way to try out making your own. First of all a bass plate is a compound curved object so you would need to carve a male form. The easiest way to do this is to use rigid foam insulation the kind used in house construction. This can be carved to your bass top shape and would be strong enough to handle the pressure. To my knowledge vacuum pressing creates 30lbs PSI. The commercial bags are quite strong. I have mostly used this company, (they sell Unibond Glue which is great for veneering) their systems are quite good, though you could make your own pump cheaply, buy a bag.
https://www.vacupress.com/vacuumveneering.htm. Veneer is cheap, if you soften the veneer first then place in the press and if your plate shapes are not too extreme this SHOULD work. I have yet to try this so I am assuming it would work. My experience has been with single plane curves, not compound. As for sharp edges the rubber roofing material mentioned would work well
http://www.woodcraft.com/search/sear...FdJL5Qod6DmA2Q

Using the frame technique, It looks like the ribs could easily be done this way as well. I can see how trying to create a compound curve in a piece of 6mm AG ply would be a problem. This brings up another possibility - hide glue laminations. I hadn't considered doing my own laminating before, but actually think it might be the easiest way to go, bending one layer of laminate at a time, producing instrument-grade plywood in the process... hmm.

Thank you for the links and very useful tips.

powerbass · #18 09-06-2010, 02:05 PM

I wouldn't recommend trying to bend 6mm ply. Make your own with veneer which is 1/27" -1/16" thick. I haven't found a source for wide spruce or red cedar veneer yet

bigolbassguy · #19 09-18-2010, 05:48 PM

I have a little 2 gal. compressor that I'm going to try converting for an AVS system. I really liked this design and think it would suit the purpose well. Also, I think I've found a couple of sources for spruce veneers, available as large as 4X8.

http://www.joewoodworker.com/veneeri.../thompson1.jpg

powerbass · #20 09-18-2010, 06:16 PM

I know a woodworker that converted a compressor similar to the one in the link. Can you send me the link for the spruce veneer? I have access to a band saw and thickness sander but buying the veneer would be easier for me at this point