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Stretching your plywood...just 1 technique

PostPosted: Thu Dec 31, 2009 11:54 pm
by doug hodder
Recently there have been a number of people asking where to get larger sheets of ply. They can be difficult and almost always are very expensive to get. I know that the experienced woodworkers here know this technique, but I thought it would be a handy thing for some of the newer builders to see. If someone would like to document scarfing ply, that would be great. There are several ways to stretch your plywood, here's one method.

This technique uses a router and if you don't have a router....well, you're going to need one anyway as it's a real versatile tool. Pick up a 3 wing cutter. Shown is an 1/8" one but they are also available in 1/4". It will cut a 1/2" slot into the edge of the ply. The 1/4" one will cut a 9/16 wide slot.

Adjust the cutter so that it is approximately cutting in the middle of the ply. I mark the side that I rout from so if it's not dead on, the sides will mate up fine anyway. Rout all the slots for the matching pieces.

I cut splines out of baltic birch ply. It's a true 1/8" ply so it's a dead on match to fit the slots. I rip them just a hair under 1", if there is any crud in the slot or they are too wide, the ply will want to sort of kink at the joint. A little narrower takes care of any of that. Baltic birch is also stronger than a lot of the cheap plys available when using small pieces.

Glue it all up, make sure to butter the sides of the spline really well and the edges on the ply sides. Weight and clamp, watch too much end pressure with a clamp however. I use epoxy as it gives me more working time, however Titebond works well also.

It's a real easy/quick way to make up whatever size sheets you want. For a woodie...I use a lesser substrate, then laminate up the nice thin veneer ply over it, making sure that the joints don't fall on top of each other. I've done this on 5 trailers so far and it works great for me. I made some 6'4" x 11' ply this evening. Doug


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PostPosted: Fri Jan 01, 2010 12:01 am
by Juneaudave
:thumbsup: Thanks for the tip Doug!!! So...how big is that sheet you glued up for the Nomad side? I couldn't find that much floor space!!

PostPosted: Fri Jan 01, 2010 12:21 am
by len19070
This really is a great technique.

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You can make some BIG sheets of plywood this way.

Happy Trails

Len

PostPosted: Fri Jan 01, 2010 12:29 am
by High Desert
question guys- what's the minimum thickness ply you can do this technique on?

Great idea, thanks for sharing it! :thumbsup:

PostPosted: Fri Jan 01, 2010 12:36 am
by doug hodder
It kinda depends on how comfortable/precise you are with your routing. I'd bet that with good quality ply, a steady hand and patience, you could spline full 1/4". That would allow 1/16 on each side of the spline. 3/8" is no problem. Doug

PostPosted: Fri Jan 01, 2010 12:41 am
by len19070
High Desert wrote:question guys- what's the minimum thickness ply you can do this technique on? :thumbsup:


The thinnest I've ever done it with is 1/2".

I made some shelving out of 3/4" plywood scraps once using 2 splines in it...it worked, but it was overkill.

Happy Trails

Len

PostPosted: Fri Jan 01, 2010 12:42 am
by High Desert
Thanks Doug and Len. I was thinking about the 3/8 to 1/2 range. This really changes the way a person looks at materials when deciding on build size.

PostPosted: Fri Jan 01, 2010 12:47 am
by doug hodder
Another advantage is that if you have a load of smaller pieces the same thickness, you don't need to go buy a new sheet of material. If it's going to be skinned in aluminum it's all hidden anyway. Doug

PostPosted: Fri Jan 01, 2010 7:55 am
by prohandyman
Great thread. This should help alot of builders. :thumbsup:

PostPosted: Fri Jan 01, 2010 10:56 am
by madjack
I use the same technique as Doug...sure beats paying 100+bux for a single sheet of ply...I have also used a biscuit joiner, which worked just fine but prefer the continuous run a spline gives you.........
madjack 8)

p.s. I have used a Titebond type glue for this BUT MUCH PREFER EPOXY for this...especially somewhat thickened epoxy...........mj

PostPosted: Fri Jan 01, 2010 11:03 am
by rwelp
For a quick and simple method to make scarf joints, try this link: http://www.oneoceankayaks.com/stitchglue/plyshophtm/scarfjig2.htm You can also use a half lap joint. :thumbsup:
Rob Welp

PostPosted: Sat Jan 02, 2010 12:07 am
by artwebb
rwelp wrote:For a quick and simple method to make scarf joints, try this link: http://www.oneoceankayaks.com/stitchglue/plyshophtm/scarfjig2.htm. You can also use a half lap joint. :thumbsup:
Rob Welp

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PostPosted: Sat Jan 02, 2010 8:07 am
by rwelp
artwebb wrote:

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Sorry abouy that, when I copied the url I accidently put an extra period in there. Try this one:http://www.oneoceankayaks.com/stitchglue/plyshophtm/scarfjig2.htm

Rob Welp :oops: ;)

PostPosted: Sat Jan 02, 2010 11:20 am
by KDOG
EXCELLENT. I don't know how I didn't think of this! I've been trying to desperately think of where to get "oversized" ply, but with this technique I don't need to! I can get started sooner. You, sir, deserve a big :thumbsup:

PostPosted: Tue Jan 05, 2010 6:59 am
by CaliforniaKid
wow another great thread...this was something i was wondering about to :thumbsup: