Butt joining 9 mm plywood

[chippy1970]

Just got myself a ply lining kit for my T5 van but the floor is in two sections split down the centre. Its 9mm WBP pretty good quality but I want to make the join a proper joint. I was thinking of running a 4mm groove with my biscuit cutter and use a long 4mm strip of ply as a loose tongue. Only trouble I see with this is there will only be 2.5mm of ply left either side of the tongue this may be weak I dont know.

When its dry out there I will take a proper look I may have room to just put a ply strap screwed to the under side of the joint.

Any other ideas ????

Cheers

 

[Mr Ed]

Yes, but if you glue the ply tongue into the groove, its effectively back to being 9mm ply again. I'd have thought it would be OK

Ed

 

[chippy1970]

Yes, but if you glue the ply tongue into the groove, its effectively back to being 9mm ply again. I'd have thought it would be OK

Ed

Exactly what I was thinking cheers.

 

[MikeG.]

One thing to watch out for, ChippyJoe, is that two sheets of 9mm ply may be different thicknesses.

I have just had this problem making a mold that had to be terribly accurate. The two sheets of 15mm ply (picked from the same pile at the same time!) were almost 1mm different in thickness, which was a real nuisance. You have to work from the reference face, in normal woodworking manner, but then it will mean that there could be a hump on the underside.

You'd obviously have to set you biscuit cutter to a very shallow depth, and would be relying on keeping it very steady as you moved it over the work. I would use a PU glue, so that any minor gaps were filled.

Mike

 

[Chris Knight]

As Mike suggests, I would use PU glue, principally for its slippery qualities not its gap filling qualities (and which are only cosmetic in any case). Glueing in a very long strip of ply into a groove could prove difficult with normal PVA glue which has a tendency to "grab" quickly.

 

[chippy1970]

One thing to watch out for, ChippyJoe, is that two sheets of 9mm ply may be different thicknesses.

Mike

Yeah I thought PU glue would be a good idea, just been up the workshop and had a look and they are exactly 9mm both sides of the joint so no problems but I know what you mean I had that problem with some MDF awhile back it was about 1.5 mm thicker.

PS Mike who's Chippy Joe ? :lol: :lol: I'm Chippy Chris :wink:

 

[Chippyjoe]

Me :lol: :lol: :lol:

Mark

 

[shipbadger]

Just an idle question, but why are you bothering to joint it. Most coachbuilders etc would use one of the adhesive/sealers from Sikaflex. I would use FC40 from O'Learys. This would allow for any differences in thickness and a slight degree of movement if the floor became damp/dry. I tried PU adhesive and biscuit joints on two 12mm sheets for a van bulkhead and found it very difficult to clamp and keep flat with the kit I had available.

Tony Comber

 

[MikeG.]

PS Mike who's Chippy Joe ? :lol: :lol: I'm Chippy Chris :wink:

Oooops, sorry!!

I posted a reply without using the quote button, so I didn't have your name in front of me when I was typing. I obviously have the memory of a goldfish.....

Mike

 

[chippy1970]

Just an idle question, but why are you bothering to joint it. Most coachbuilders etc would use one of the adhesive/sealers from Sikaflex. I would use FC40 from O'Learys. This would allow for any differences in thickness and a slight degree of movement if the floor became damp/dry. I tried PU adhesive and biscuit joints on two 12mm sheets for a van bulkhead and found it very difficult to clamp and keep flat with the kit I had available.

Tony Comber

Yeah its only a thought at this time I wont fit it until the weekend. I have used Sikaflex before for laying a solid oak floor great stuff. I was just going to fix the ply down with the six lashing points. I can swap the lashing points for 40mm m10 countersunk socket screws and screw down into the existing threaded holes. I suppose the odd dab of Sikaflex would help.

Heres a video of something similar http://www.youtube.com/watch?v=vp7X5tmxkSU