Is all BS 1088 Plywood perfectly square?

John Robinson

John Robinson

Well-known member
I finally got all of my materials, supplies and boat cradle in order and organized in my workshop. I learned my lesson from our earlier duck boat build and ordered all high quality wood, epoxy and glass cloth. I ordered the BS1088 Okume from Edenwood supply, one of Devlin's recommended suppliers. I am very happy with the quality of product and service, they were very easy to deal with over the phone.

One problem though, this weekend I started the project by staggering the plywood on my work table and started to power plane the scarf "stair step" method. I noticed two things about my plywood. One of the 3/8" sheets was slightly warped, the others were all perfectly flat. By chance this was the sheet I stacked on top, and anchoring it with screws didn't flatten it perfectly against the rest of the stack, so I set it aside and picked one of the other 3/8 sheets. This one laid flat but seemed to be 1/4" out of square on the end I was scarfing. As I write this I can see that I should have turned it around and checked the other end.

Am I being too anal? It seems to me that if I ignore it and plane the scarf on and angle even this slight, the glue joint with either not be tight, holding the panels inline, or the panels will cant with a tight joint. I did measure the panel for a right angle using the old 3-4-5 method and it looked square by my tape measure, but 1/4" in eight feet might not show up that way. I'm nervous about cutting another end with my skill saw, factory edges always seem straight and square. I'm probably missing something as I got tired and frustrated. Maybe it will all be perfectly clear when I get home tonight, but if you notice something I'm missing please shout out.

thanks,

John
 
John

You want at least one edge on each of the 16' panels to be straight as a taught string. All your lofting is done with this as a reference point(I'm assuming your offsets index off the same edge of the plywood but do remember the scaup used both sides) so it's important. Using a straight edge and a large T-square you should be able to cut off the end of the plywood to make it square. Shouldn't be more than the 1/4" you stated. I wouldn't worry about the warped panel. Just use it to your advantage, either in the hull or on the decks. Okoume is cooperates quite well so you should be able to move it into position without too much difficulty.
 
John,

Eric alluded to it and I'll second it. If you are working with plywood you really need a 4 foot T square. I think they are called drywall T squares in the store. It is one of my most used tools when I am lofting or any other measuring on plywood. In my mind one of the 'must haves'. I may not be able to find a builders square sometimes but I always have my T square handy.

Pete
 
Another way to check your squareness on any square or rectangle is to measure corner to kitty corner and then do the same for the other two corners. If the measurement is the same, the sheet is square.

square.jpg
 
Like Steve said, corner to corner is the most accurate way to see if something is square....but....if both ends are cut the same out of square with the sides you will have a sort of trapezoid. Always square off the long side and cut it square yourself. It's easy to be off a little when stacking to gain a bit on the ends...a 1/16" off in 8' due to a screw kicking a panel can throw it off. When gluing up your scarf, snap a chalk line to lay your long edges to.
 
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