3.5 mm plywood

[sanctuary79]

so i have just ordered some 8 by 4 sheets of 3.5 ply

ext, not birch

 

plans to just vanish them

 

however is this too thin?

im using them for the roof and sides

with battens 2ft apart

 

thoughts?

[twbm]

Yes. Much too thin. You'll go through that if you walk on it and any contact with tree branches risks damage to the cabin sides. Wouldn't use anything less than 15mm myself.

[sanctuary79]

Yes. Much too thin. You'll go through that if you walk on it and any contact with tree branches risks damage to the cabin sides. Wouldn't use anything less than 15mm myself.

 

thanks for the relpy

however, im a little confused

 

the floor is 22mm - done

the ply (3.5) has been brought for the side (under and above gun)

and the inside of the roof

 

covering 50mm and 25mm celeotex boards in steel structure

[pete23]

i used to fit boats out, most cabbin sides and roofs were done in 9mm faced ply, although i reffited my own boat and i done the cabbin sides in 16mm t+g.

 

3.5 is far to thin.

[twbm]

thanks for the relpy

however, im a little confused

 

the floor is 22mm - done

the ply (3.5) has been brought for the side (under and above gun)

and the inside of the roof

 

covering 50mm and 25mm celeotex boards in steel structure

 

If you'd said 'for lining the inside' I'd have replied 'Probably OK'. But you said you were using them for the roof and sides.

[Higgs]

It is thin, to be honest. It doesn't give you alot to screw fitments into. Unless it is really well battened, will probably warp. Probably 6mm for the ceiling, 9mm for cabin sides, and 12mm below the gunnels.

[sanctuary79]

@twbm

hands up...my bad

 

@higgs thanks

very helpful...will try and cancel the order and get some thicker sheets

 

Ta

[alan_fincher]

I'd say 6mm absolute minimum if not backed by something else.

 

Chalice uses 9mm throughout, which I consider is rather better.

 

3.5 mm is little more than stout cardboard!

 

I'd say 6mm absolute minimum if not backed by something else.

 

Chalice uses 9mm throughout, which I consider is rather better.

 

3.5 mm is little more than stout cardboard!

[Titan]

I feel its often difficult to make what u want out of what u have, my guess you like the finish/appearance of what you have bought, as others will say a tad thin, builders express are very inexspensive for faceless ply which you could use as a sub base ??? or if your sticking to your choice ,perhaps exspanding foam could be applied just prior to the last few fixings to bulk out and indeed support your ply ????? the reason i say this im using 6mm oak ply above gunnels which could flex but a quick squirt of foam makes them solid. regards Martin

[BEngo]

thanks for the relpy

however, im a little confused

 

the floor is 22mm - done

the ply (3.5) has been brought for the side (under and above gun)

and the inside of the roof

 

covering 50mm and 25mm celeotex boards in steel structure

 

 

3.5 mm will be OK for the ceiling, provided there are plenty of battens and they are nicely lined up to avoid waves and ripples. You won't be able to fix anything much to it, except at the battens though. My ceiling is OK after 23 years in 4mm ash faced ply. Keeps the high-level weight down nicely.

 

3.5 alone is far too thin for the sides. 12mm at least so you can fix other things to it. If though you find that your merchant won't or can't substitute thicker ply then you can simply put somme 9mm ply behind it and glue the thinner stuff on top. There are advantages to this in that you can make your cock-ups with the cheaper ply and then cover it up with the fancy faced stuff. DAMHIKT.

 

N

[churchward]

so i have just ordered some 8 by 4 sheets of 3.5 ply

ext, not birch

 

plans to just vanish them

 

however is this too thin?

im using them for the roof and sides

with battens 2ft apart

 

thoughts?

I would say 3.5mm is OK for ceiling lining particularly if it has to form a curve. 6mm min on the sides would be better.

 

It would be interesting to see someone form a curve with 12mm ply on the ceiling!

[bowten]

9mm for sides,6mm for roof sections.You will be able to flex 6mm if your roof section is curved.

[nb Innisfree]

thanks for the relpy

however, im a little confused

 

the floor is 22mm - done

the ply (3.5) has been brought for the side (under and above gun)

and the inside of the roof

 

covering 50mm and 25mm celeotex boards in steel structure

 

If you was sticking 3.5 straight onto celotex which in turn is stuck to steel sides then yes it would make a solid job provided it was completely backed up by celotex with no hollows behind.

[designerstuart]

i found 6mm ply for a curved ceiling a bit thin with battens at 600mm centres - it bent nicely but bowed out between the battens. i ended up trying to stiffen it along the edges and fitted some wedges to avoid the ripple effect which worked okay in the end.

 

if i did it again i'd provide more support for the edges (i had my lengths going longways, so 150mm gap either side) rather than bulk up the thickness.

[blackrose]

I've got 9mm at the sides and 6mm on the ceiling. I was told 6mm was a bit thin, so 3.5mm sheets sound like wafers.

[bowten]

i found 6mm ply for a curved ceiling a bit thin with battens at 600mm centres - it bent nicely but bowed out between the battens. i ended up trying to stiffen it along the edges and fitted some wedges to avoid the ripple effect which worked okay in the end.

 

if i did it again i'd provide more support for the edges (i had my lengths going longways, so 150mm gap either side) rather than bulk up the thickness.

This is what you must do on the edges.

 

I've got 9mm at the sides and 6mm on the ceiling. I was told 6mm was a bit thin, so 3.5mm sheets sound like wafers.

6mm is absolutely fine on ceilings.

[sanctuary79]

i found 6mm ply for a curved ceiling a bit thin with battens at 600mm centres - it bent nicely but bowed out between the battens. i ended up trying to stiffen it along the edges and fitted some wedges to avoid the ripple effect which worked okay in the end.

 

if i did it again i'd provide more support for the edges (i had my lengths going longways, so 150mm gap either side) rather than bulk up the thickness.

 

Thats right the idea was to follow the curve from the fluch celeotex boards and fix onto 1" battens that run along the sides...ie most of the sheet would be stuck (marine flex) to the roof - id say 70% would be in contact with boards and angles.

the air gap debate is now in the bin for me.

a trim would hide the sheets meeting (5ft by 4ft)

with no lighting from the roof

and 4/5" holes for vents

 

 

thanks for all the replies

GGRRRR need my camera back form the missus - would be easier to show you all ....right?

Edited August 15, 2012 by sanctuary79

[bowten]

Thats right the idea was to follow the curve from the fluch celeotex boards and fix onto 1" battens that run along the sides...ie most of the sheet would be stuck (marine flex) to the roof - id say 70% would be in contact with boards and angles.

the air gap debate is now in the bin for me.

a trim would hide the sheets meeting (5ft by 4ft)

with no lighting from the roof

and 4/5" holes for vents

 

 

thanks for all the replies

GGRRRR need my camera back form the missus - would be easier to show you all ....right?

Yep.