Primitive Archer
Main Discussion Area => Bows => Topic started by: Prarie Bowyer on March 11, 2012, 11:20:35 am
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Hey guys.
I need to make some scarf joints. What is the best way to do that? Router Jig? Drum sanding sled? Shooting Board?
If it's not Drum Sanding jig then anyone have the tools for precision jig making and want to trade for a scraping shave?
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I've done a few scarf joints and always did it by hand on a belt sander.
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I would clamp both pieces together and use the belt sander (stationary). We use planes in boat building to do this, but we are also scarfing plywood sheets together. Easy process as long as the ends match perfectly for gluing.
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Dont have stationary belt sander.
Target wood is carbonized bamboo flooring.
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Belt sander, disc sander, miter saw ,ect.
What tools do you have !
What are you calling a drum sander (sand paper on a drum in the drill press)
done with patience and a sled maybe ,but not the best option
guy
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I just use a miter saw...
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I just use a miter saw...
me too, Bub
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Here is a very simple way to make a solid splice.
Take both limbs, and set them end to end laid out as if they were one bow already.
Overlap them 6 inches. ( 6 is the minimum, 8 is best )
Have the upper limb to the left of the lower with that 6 inch overlap.
Using a straight edge and a sharpie, draw a straight line from the upper corner of one limb to the lower opposite corner of the other.
That is the line that will define your splice. Its just a line that resembles a not equal to symbol. Where the equal symbol are you limbs, the slash is your splice.
If you are good with your basic handsaw, clamp both limbs side by side and cut them both on the line at once. You may want to fashion a miter box of sorts to keep you straight.
After the cut is made, test fit the limbs togeather. Any inconsistancies in the cut can be fixed with a 2x4 clamped to a table with 8 grit on top. Pretend this sanding block is a belt sander, and rub the cut limb over it to fix any uneveness ( that word looks strange ) in your joint. Some gap is ok, but anything over 1/8 inch I would for sure fix. Use a good gap filling glue or epoxy. I use tighbond 3. It has worked for me on bows up to 55 lbs no worries.
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Belt sander, disc sander, miter saw ,ect.
What tools do you have !
What are you calling a drum sander (sand paper on a drum in the drill press)
done with patience and a sled maybe ,but not the best option
guy
I made a drum sander around solid maple slug that I tured up in my lathe. Mounted it on a 5/16 stainless rod. Made an adjustable floor under it that bolts to the lathe table
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Here is a very simple way to make a solid splice.
Take both limbs, and set them end to end laid out as if they were one bow already.
Overlap them 6 inches. ( 6 is the minimum, 8 is best )
Have the upper limb to the left of the lower with that 6 inch overlap.
Using a straight edge and a sharpie, draw a straight line from the upper corner of one limb to the lower opposite corner of the other.
That is the line that will define your splice. Its just a line that resembles a not equal to symbol. Where the equal symbol are you limbs, the slash is your splice.
If you are good with your basic handsaw, clamp both limbs side by side and cut them both on the line at once. You may want to fashion a miter box of sorts to keep you straight.
After the cut is made, test fit the limbs togeather. Any inconsistancies in the cut can be fixed with a 2x4 clamped to a table with 8 grit on top. Pretend this sanding block is a belt sander, and rub the cut limb over it to fix any uneveness ( that word looks strange ) in your joint. Some gap is ok, but anything over 1/8 inch I would for sure fix. Use a good gap filling glue or epoxy. I use tighbond 3. It has worked for me on bows up to 55 lbs no worries.
These will be for bamboo core laminations Say 1/4" thick? That kind of overlap still necessary? I'm trying to pieces long enough to stick into an ELB design.
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The goal in a scarf splice is to have a 6 inch long to 1 inch thick ( 6:1 ) ratio splice. This is optimal.
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For a core lam you only need them 1/2 inch long, 1/4 is enough.
I make reflex/deflex flatbows with tapered cores that are made with a drum sander so they have to be spliced somehow. The simplest core splice is a scarf joint. If however you intend to make the elb's bend in the handle it is safer to use a fishtail splice.
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I have never made a core lam, so I would go with mike on this one. However, if it were just a self bow, I stay with what I said.
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If the splice is in the handle area I totally disagree, a 45 degree cut is plenty. If you are making a lam bow, it would have to shear from the back, or the handle would have to pop off for there to be any danger. If that happened you have bigger problems.....
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If that happened you have bigger problems.....
I bet.
So I'll plan on 1/4" lam for the first one and 1 1/4" overlap. The elb design I'm considering won't bend in the handle or not right at the handle. I may pin them with 1/8" dowels to assure alignment during glue up. Oh wait. I'll need to grind the lam any way... So I'll just clamp them to a straight form with news paper under them and use a bit of tight bond. Then when the 3 lams come togeather I'll use the almighty URAC (heavenly light and music).
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Titebond or urac will work for the main glue up there is no real difference when the lams are well prepared. A 45 degree cut is what you want. It's pointless making them longer for core lams with no bending. Superglue is the best for scarf joints - quick and easy. Use sellotape instead of newpaper.
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Sorry I was away for a bit !
Mike has ya all lined up it looks !!
Guy
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Yep super glue, Mike has it down. ;)
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There was this one time my friend Jimmy was about to light one up when this cop walked around the corner. Man, you never saw someone scarf down a j....oh, THAT kind. Uh, never mind. :-[
Post pics of your laid up joint when you are done, even if it ain't bow porn, good woodworking pics are nice to see.
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GUYS !
Scarf joints are EASY!. I read on other sites that 8:1 or even 12:1 were optimal. Lemme tell ya. 6:1 is just dandy. I need to reorder my order of operations. I split the plank into thirds on my bandsaw. THEN sanded the finish off the biggest thirds and split it down. I was trying to get three pieces out of each plank but it's not practical unless verging on paper thin is ok.
Still two planks ber board is great with a skinny left over for accents and stuff.
I used scrap to make a scarf jig for the router. it works great but I wish my router plate was clear plexiglass. I can't see what I'm doing. :-[
After making the scarfing jig I realized I need to make a gluing jig. So off to that I went. Kinda like a bench hook. Glued it up with TB3 and let it sit overnight. I then ran the whole thing through my lam sander affectionately named "knuckle rubber". TO think I almost made it by sandwiching a bunch of those mini skill saw blades. Fortunately i played that out in my head and saw the possibilities.
With all that sanding to clean up saw marks and glue joint and flipping it and basically holding it by one end out flat.. the joints held and are invisible. If I bought this lam I'd think... "some lucky guy has a source for 74 3/4" bamboo planks. Bastard. But wait! It's meeeeeee!.
New process: Clean finish off with router set to 1/16" depth. Saw out planks. Sand on lam grinder. Scarf. Glue up. Clean up joint on lam grinder. DUN! move on to building bow. Lam grinding time minimized.