Hardwood faced plywood for a campervan worktop? Warping?

[mlawranceowen]

Hi,

I am in the process of converting a Campervan and am about to sort my worktops out. I have built some units using lightweight plywood and I managed to get a couple of nice planks of Beech wood. I have cut this down to 6mm pieces which I was going to glue to the plywood top to give the effect of a solid worktop (lightweight, with more durability that a thin veneer ply). However, I have started to become paranoid about the expansion of the Beech and how much warping it may lead to...Does anyone have any thoughts on the best way to achieve the effect I am looking for while minimising the possibility of warping? I was thinking about using a similar method to glue down for solid wood flooring? I understand flooring glue allows for expansion and if I leave a 5/10mm gap around the back edges for expansion then maybe this could work? Any help would be greatly appreciated as I really don't want to waste all the bits of Beech I have cut (but equally don't want to ruin my plywood units...) .

Cheers, Mike

 

[profchris]

My experience is guitar and ukulele making, to put this in perspective....

I'd say the most important thing is to glue the beech on in comparatively low humidity (around 50%). You don't want the veneer to shrink and crack.

A guitar top or back using a vertical grain cut (viewing the board end on) might move around 1mm in the vertical direction. That's probably manageable, assuming the cross grain dimension of your worktops is around 18 inches, maybe 50% wider than a guitar. Your plywood will reduce this movement to near zero, unless it's really thin.

Horizontal grain moves more, maybe producing a 2mm rise in 12 inches across the grain.

If you're concerned, measure the board width on a dry day and on a humid day. I'd guess you'll be fine, but each board acts differently. But I stress again, glue up when humidity is low. A little distortion might not be noticed, but cracks will be.

 

[Inspector]

Balance the forces by gluing more Beech on the bottom of the plywood. Same thickness but it doesn't have to be the nicest. Same as you would do if you were going to veneer furniture.

Pete

 

[mlawranceowen]

Cheers for the replies. Unfortunately I don't have any more Beech that I can glue to the underside (not much anyway)...Also, what glue would you recommend? Originally I was going to use a PVA wood glue (Titebond/Gorrilla) but have seen some people suggest the water in it will be absorbed by the ply and cause problems...Would it be better to use a more flexible glue to allow the Beech to expand a bit?

 

[custard]

I have cut this down to 6mm pieces which I was going to glue to the plywood top to give the effect of a solid worktop (lightweight, with more durability that a thin veneer ply).

This is a really bad idea. You're basically using 6mm thick veneer without a balancing veneer. That's bad practice in two ways. Firstly 6mm is way, way too thick for any veneer laid onto a sheet goods ground, and secondly you always need a balancing veneer.

Don't invest any more resource into this plan and start again as its virtually certain to end badly.

 

[mlawranceowen]

I'm slowly starting to realise this may have been a bad plan....As the Beech is fairly thick still I am thinking that I can edge glue up all the pieces to make a 6mm thick panel and then fix this to the plywood with standard solid worktop methods. I.e. leaving expansion gaps, low modulus silicone and possibly some slotted brackets....I know this isn't ideal but as it's a campervan I'm not overly precious about it being perfect...just dont want to cause damage to my units...

 

[Simon_M]

Adding plywood (that's stable) to wood (that's liable to shrink/expand) = total disaster. Not unlike a bimetallic strip?

Not to mention that a camper van can be left in the sun so internal temperatures can escalate.

Some cars used very thin "matched" veneer e.g. left/right and front/back matched and everything glued to an aluminium substrate. The strength is from the substrate - not easy to replicate.

If there was a simple way that works in a vehicle, they would have cottoned on and switched to it too.

 

[Simon89]

What would the weight difference be between your proposed solution and a solid hardwood worktop? Often when you cutout for your sink and stove there isn’t a huge amount of worktop left.

 

[colinc]

Mike,

I don't think I can add anything to what has been said about the use of the beech as a veneer.

I think that I would be looking at using a laminate (Formica) both sides of the ply myself for durability.

Personally, I am quite interested to know more about you Campervan build in general as it is something I have been pondering for years. How about some photos in the Projects section? I think it will have enough woodwork in it to be relevant.

regards

Colin