Scarf Joint

Mesh drywall tape has a glue on it, that I'm not sure about, in regard to adhesion or comparability with epoxy. There are a lot of techniques you can use to insure no joint starvation. One of my favorites is back cutting the joint. You leave the perimeter of the joint alone, but hollow out inside the joint a bit. This way the edges of the joint look perfect, once the ooze out is removed, but inside the joint, a mass of goo is holding things nicely. You can also use string, placed into the joint, which even after crushing with a clamp, will offer some room for the goo, but you'll also have a fat glue line, which my back cutting technique doesn't.

 

A bonded joint should have .005 to .010 gap for max strength. Fishing line would work well if it is not too heavy.

 

Now you tell me - when I think of the trouble I used to go to in order to get perfectly flat surfaces for a scarf joint . . .

 

hi.have anybody NES 02-140 or nes 08-100 standard?
if any body have it,please send to my mail. it is very vital for me to have it.
my mail: apachi.89@gmail.com
thanks allot.

 

West system has a scarffer that you bolt on a skill saw, should save lots of labor, 875 Scarffer.

 

Or you can shape a couple of 2x4's, fasten them together, and attach them to your Skilsaw....





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The pictures are from my build thread for the canoe I built with my son, before he went into the Army:

http://www.boatdesign.net/forums/wo...ation/building-flat-bottomed-canoe-33266.html

 

Fiberglass window screen sounds like a possibility.

 

There are millions of scarfs that haven't failed glued the standard way. I think it is an unnecessary complication with no real advantages. Joints get starved because the wood absorbs the resin. If you put something that keeps the wood surfaces apart and the wood absorbs resin, there should be a gap left.

 

Prep is always the key and precoating raw wood is just a standard requirement, for any epoxy work.

When I have stock I can lay on a bench, this is the setup I can use. I can cut a 9' scarf with this, easily.

 

Par,

Looks like a good set up. Solid so you get a consistent cut.
I just have to question the 9' scarf. Did you mean 9/1 ratio?
How thick of a piece of ply can you cut with the circular saw blade?

 

No, I meant a 108" long scarf. I made it on the edge of a work bench, so I could scarf the long edge of plywood, for a large planking project I was working on.

A typical 7 1/4" circular saw can cut a 2.5" deep cut, so this means a 10:1 on 1/4" stock, a 6.6:1 on 3/8" stock and a 5:1 on 1/2" stock. If you remove the guard, you can swing an 8" blade and get more slope on the scarf for thicker stock. My jig was set at a common angle to maximize the blade depth. 5:1 with an epoxy joint is suitable for plywood that's not heavily radiused, such as planking. A quickly curved combing for example, might get pissy with a 5:1 scarf slope.

By changing the blade angle you can get a better slope too, but you have to have the blade diameter to pull it off. I have an off brand 9", that now swings s a 10" blade. It can cut a 8:1 scarf in 1/2" stock, but watch your fingers. This saw scares the hell out of me when I use it. Maybe one day I'll make a guard for it. I know Makita sells a 16" circular saw, which probably costs a fortune, but damn what a machine.

 

I used to work for a contractor who owned one of those 16" Makitas; it was his pride and joy. He only brought it out to cut beam ends, and wouldn't let anyone else touch it -- partly because he he was afraid they'd break his toy, and partly because he was afraid they'd cut their leg off.

 

hi.i am sorry, my English is not good.
I use epoxy resin to build laminate joint(not adhesive bond joint), such as tee joint. i have one question.
what time(day) after curing laminate pieces is better to assembly them with epoxy? and what time after assembly i should cure theme(assembly piece)?
I use epoxy 5052 resin,there is no information in manual.
thanks

 

Cure time ?

I Dont know how long for your climate, shop temp. and epoxy.

Why not make up a few Tee joints then break them a 12, 24, 36 hours.

With the West System Epoxy and standard hardner .... 24 hours at shop temperature is required before the joint is stressed...manhandled.

With West system epoxy , a plywood scarf joint at standard shop temp ..needs 36 hours before handling

 

Michael, it's likely he's attempting to get information about Araldite 5052 epoxy. A quick trip over to their web site will yield the appropriate gel, pot and cure rate/times he's looking for. This would be the logical place to start, in any case. Of course, as you and I know, these are subject to considerable "flexibility", depending on shop conditions.

Troy, I knew a timber framer that had one and he prized his as well. I used it a few times and it's a beast, but cutting a 7" deep tenon shoulder in one pass, on a 12"x16" log is a lot of fun.