Scarph idea

[Paulyboy]

One of the newer router bits on the market makes a multifingered "glue joint" on edge. Depending on the wood thickness, there are anywhere from 2 to 5 fingers on the finished edges. Wouild this be an alternative for a scarphed joint?

[Ken Hutchins]

Looks down a few threads to WOOD MAST AND BOOM for your answer. ;)

[Bruce Hooke]

The follow discussion about finger joints came up on another recent thread (http://www.woodenboat-ubb.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=011102):

StevenBauer
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Member # 1053

posted 03-03-2005 07:24 PM Profile for StevenBauer Email StevenBauer Send New Private Message Edit/Delete Post Reply With Quote I still like Ken's method:

http://www.imagestation.com/picture/sraid81/p0a86206838a1833cc24385a518ebe544/fafd4aba.jpg

fingerjointed at a 2 to 1 scarf

Steven Posts: 231 | From: Portland, Maine | IP: Logged
Tom Lathrop
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Member # 942

posted 03-03-2005 07:46 PM Profile for Tom Lathrop Email Tom Lathrop Send New Private Message Edit/Delete Post Reply With Quote The finger joint appears to be kin to a scarf that takes up much less length from the board. That it can be cut by machine in a production line makes it very popular with molding and trim manufacturers.

However the finger joint still has a significant amount of butt in it and can not be as strong as a full scarf.

I will be happy to put this one to rest

Now, in big timber construction, such notched joinery is more common since it handles wood movement better and glued joints are rare. Posts: 1312 | From: Oriental, NC USA | IP: Logged
ssor
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Member # 9610

posted 03-03-2005 08:28 PM Profile for ssor Email ssor Send New Private Message Edit/Delete Post Reply With Quote Finger joints in moulding are no more prone to failure than any other part of the stick. I am always impressed with just how well they do. The long scarfed fj combination looks to me to be the best of both worlds. A standard scarf is it, seems to me to be very demanding of accuracy and clamping, while the fj can be glued and driven together with alot less concern for the varibles of clamping. Posts: 163 | From: Bel Air, Md | IP: Logged
Harry Miller
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Member # 6588

posted 03-03-2005 08:59 PM Profile for Harry Miller Email Harry Miller Send New Private Message Edit/Delete Post Reply With Quote I think Norm's lying about his last name. [Big Grin] Posts: 793 | From: Toronto Canada | IP: Logged
Bruce Hooke
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Member # 1507

posted 03-03-2005 09:15 PM Profile for Bruce Hooke Author's Homepage Email Bruce Hooke Send New Private Message Edit/Delete Post Reply With Quote I am somewhat concerned about finger joints in boatbuilding because, as Tom noted, there is some end grain left in the joint so in high load situations I am not convinced that it would be as strong as a proper scarf. There is a big difference between the loads placed on the lumber used in your average house (which is where I have usually seen finger joints) and the load placed on many parts of a boat. This is why we are a LOT more picky about the wood going into a boat than we are about the wood going into a house.

That said, it does seem like a finger joint might be a reasonably solution to joining pieces of wood that will go into a birdsmouth spar. Without some solid data to rely on, however, I probably would not use it in a spar that would be big enough to really hurt someone or create a dangerous situation if it broke in use. Posts: 4664 | From: Rhode Island, USA | IP: Logged

[JimConlin]

The literature (See other thread) says that the tensile strength of such a joint is maybe 75% of that of the solid stock. I would be inclined not to use the method in a spar, but would strongly consider it in other applications. Of course, I'd be influenced by tensile test results.

[Ian McColgin]

It maybe that I'm just too simple, but it seems to me quite a bit easier to make a nice flat 12:1 bevel match another flat 12:1 bevel - all by hand with pleasantly quiet tools - than to screw around with noisy machines that must be carefully alligned to produce something that's not as strong anyway.

Just as the needs of housebuilders are profoundly different from boatbuilders, so too the needs of mechanized mass production for stuff that will go into a house are different from the practicality of a little hand work in a one-off boat where the building is part of the pleasure in the first place.

You all just wait till Seth's book comes out and then you'll see . . .

[Tom Lathrop]

Well said Ian.

[Paulyboy]

Thanx, guys. Although this was aimed more at scarphing strakes, I get the jist of your replies. Overall strength is diminished and the noise is not the same as the good, zen like quality of the swishing of a well tuned hand plane.

[Tom M.]

Seth's book? Anyone care to explain? Thanks.

[Ian McColgin]

HehHehHeh.

I was one of the folk reading and helping Seth Wood edit his book, which I hope makes it to publication. Grandpa would always find the right old fashioned not over-mechanized way.

http://www.woodenboat-ubb.com/cgi-bin/UBB/ultimatebb.cgi?ubb=get_topic&f=6&t=003665&p=