Recommended thickness for ply back

[xwtb]

Is there any consensus regarding the best thickness for a laminated back? I've seen flatback plans specifying .20 in. (5.2mm) But suppose you happen to have a nice sheet of .25 hardwood veneered plywood-- should you use it as is, or plane it? Or ditch it? Alternatively, say you have a 1/8" sheet-- use it as is, ditch it, or add a veneer to thicken it up?

Observations much appreciated.

L.F.Miller

[Matthew Tucker]

If you use a thicker ply your bass will be heavier. But it will probably be OK.

if you use 1/8" ply your bass won't be very robust. The edges will chip easily and the thing will have to be braced strongly especially to support the soundpost.

Ideally, you need to make it as light as you can without it falling apart or collapsing under string pressure. (Arnold said that a way back, and its a good mantra)

[xwtb]

Thanks, Matthew. I've learned since first posting that while what's actually double-veneered mdf is a full .25" thick, nominal 1/4" plywood with a single cross-grain veneer center is likely to be closer to .1875". Since most hardwood veneer plywoods seem to be available in 1/4", but not in in anything thinner, this opens up a good range of possibilities beyond the standard 5.2mm stuff, which comes only in the drabbest lauan or birch. I couldn't get excited about building a bass that looks like a bathroom door.

LFM

[Matthew Tucker]

Originally Posted by xwtb

I couldn't get excited about building a bass that looks like a bathroom door.

That statement indicates to me that you may need to brush up on your antiquing and finishing skills

Some great basses are made from very plain looking wood. But if you're really after a stunning looking back, then you may need to look further than plywood!

curious - are you building a whole bass, or just replacing the back on an existing one?

(edit: Oh hang on, you're a washtub guy So are you asking about a washtub bass or a double bass? if the former, forget everything I said, as I could never get excited about a bass that looks like a washtub!!)

[xwtb]

If there's anything that antiquing and finishing can do to make a slice of lauan visually interesting, I'd like to know about it! Seriously.

I wouldn't say they're stunning, exactly, but you certainly see multitudes of grain patterns in plywood that are unheard of in solid wood.

It's a complete upright that's in the works. The x in xwtb refers to the fact that my washtub bass days are now behind me. If I ever build another tub bass, it'll at least have a carved spruce top.

Picture of target piece attached. Joining my basses LeRoy and Igor, this one will surely have to be called Madonna (Our Lady of the Plies?).

BTW is your bass-building site back up and running?