Scarfing plywood

[Mick C]

HI all. Can anyone recommend a good tool for scarfing (scarphing) plywood sheets.
Thanks
Mick

[Wand]

Originally Posted by Mick C

HI all. Can anyone recommend a good tool for scarfing (scarphing) plywood sheets.
Thanks
Mick

A plane? That's all I've known so I'm all ears if there are better tools...

[holmek]

If you mean forming the edges, a plane and belt sander. Use sheets of office carbon paper to check for high spots.
To clamp and glue if screwing is not acceptable, then make up a box-clamp using a two by four above and below along the length of the join with a spacer at each end to hold them apart a little more than the thickness of the plywood. Then drive a series of wedges between the two by four and the plywood to create pressure on the join.

[keepondancin]

West System (Epoxy) makes a scarfing jig for circular saws. You can also make a tapered jig and use a router, google search should turn up an example. Belt sander would work, and a plane is the old standby. The West web site give some good info, and there is a pdf download of their boat building and maintainence book that has a chapter on scarfing wood.

[capngeo]

I use a shaper, but I’m a tool snob and have one of everything. The same tool makes nice panels for cabinet doors too!

[bobofthenorth]

I built my own jig so I could use my router. I seem to recall an article in Woodenboat that was the inspiration for that project.

[HopCar]

I've built a couple of small stitch & glue boats from 1/4" plywood. I used an 8 to 1 ratio and it worked fine. I drew a line 2" from the edges of the plywood that I wanted to join. (1/4 X 8 = 2) I stacked the plywood with the edge of the top sheet on the line of the bottom sheet and tacked the two sheets together. I then used a belt sander to grind the taper on both pieces at the same time. You just keep sanding until the taper touches both the bottom edge of the lower sheet and the line on the top sheet. It was actually easier than I thought it would be. No special tools required. I practiced on a scrap the first time to get the hang of it.

[minaret]

Originally Posted by keepondancin

West System (Epoxy) makes a scarfing jig for circular saws. You can also make a tapered jig and use a router, google search should turn up an example. Belt sander would work, and a plane is the old standby. The West web site give some good info, and there is a pdf download of their boat building and maintainence book that has a chapter on scarfing wood.

I can testify that the scarfing jig for circ saws is a great tool for scarfing ply. With a quality saw and blade it will crank out nice scarfs faster than any other method, with a small tool you can take anywhere and minimal setup.

[clockwork orange]

I mostly use a power planer and stagger the sheets by the scarf ratio so its like a lot of steps that get planed off,then finish up with a belt sander.The glue lines give a great visual guide.
Steve.

[HopCar]

Clockwork, steps is a good description of how you place the sheets. If I had a power planer I would have used it as you did. It took me longer with just the sander. You're right about the glue lines being good guides.

[Adelie]

Scarfing plywood sheets - scarfing jig

Here's a technique that uses a circular saw.

[minaret]

Originally Posted by Adelie

Scarfing plywood sheets - scarfing jig

Here's a technique that uses a circular saw.

I like the WEST System 875 Scarffer better. It's a great piece of gear. It's limitation is that it's designed for a max 8" circ saw blade and so can only do an 8:1 scarf on up to 3/8" ply and no more. If you do a home made jig you can use a 10" circ saw and scarf 1/2" ply if you need to. I like a simpler jig that doesn't require so much setup like this.Thats the WEST scarffer on the bottom.

West System 875 Scarffer

[Mick C]

Thanks all.
Yes I did the google search and came up with the same ones.
My problem is that some of the bulkheads are over 25mm thick so trying to get a scarf on these are a challenge. I don't think the circular saw will be feasible at 12:1.
I found a scarf rail system for a router that looked like it had potential but only goes to 1.6 m wide. I will need to join 2.4m sheets.
So currently I am developing a stiffer more robust version of the rail system with a router. A friend is a s/s welder (VG too and works for beer and a BBQ ) so we are designing up something with some scrap s/s he has.

Finally the designer has also indicated that a butt joint with doublers will be ok so I am checking the furniture positions to see if I can hide the doublers which would be MUCH easier.

Thanks for the input.

Mick

[Wand]

Originally Posted by Mick C

Finally the designer has also indicated that a butt joint with doublers will be ok so I am checking the furniture positions to see if I can hide the doublers which would be MUCH easier

Yes, much easier I've found, especially for a hack like me. But as a matter of interest, can you say what you're building?

[clockwork orange]

How many sheets do you have to do? You are going to spend more time dicking around trying to solve a problem that dosnt exist,better to just get on with the job.Thicker ply like that is the easiest to scarf because,assuming you are using good quality plywood of course,it is nice and flat,so just mark a line 9" in from the edge of each sheet(for 12:1) and stack them all on top of each other with each sheet staggered by the 9",clamp the stack together and plane it all off with the electric planer, i start off with a thick sheet that is not going to be scarfed on the sawhorses and line up the edge of the bottom sheet with the edge of this to support it as it becomes a feather edge. You will be done with a whole boats worth of scarfs before your done picking your ass trying to figure out your routing jig. Its a quick process,really.
Steve.