Scarfed in plank ends?

[bhaskell]

Looks like a few of the plank ends on my 28 ft, 66 year old cutter, have gone bad. If I cut back and replace the planks I may end up replace about half the planks. Could I scarf and glue in new plank ends for the bad ends by using a 1 to 12 scarf? After all many long planks are "make up" in this way now days.

[Thad]

I say "Yes".

[Rich VanValkenburg]

I've replaced a few using butt blocks and they turned out fine. It might be tough cutting a perfect scarf unless you remove the whole plank and work it on the bench. Gotta watch where the butt block are positioned.

Rich

[Gordon Bartlett]

I'm with Rich on this one. Sure, I suppose you could use a scarf but it would be a whole lot more difficult to do than a butt joint. By the way most of the "authorities" recommend staggering the joints at least 2 frame bays on adjacent planks.

[Chipito]

I helped restore an old pilot boat and we replaced a lot of butt joints with scarfs. The coast guard would not let us scarf the hood ends though. Dumb but what can you do.
Jeff

[Thad]

Generally with hood end repairs it is not reasonable or possible to space the butts enough, weakening the hull. Replacing whole planks when 90% of the planks are solid does not always seem reasonable (eg, the work to pull fastenings, and finding stock at least as good as that to be replaced), so I think scarfing ends on the old planks the next best thing. I have seen some fine hogging in hulls with short butts in the ends.

[Concordia..41]

Nevins and Herreshoff's rules for wooden yachts address the size, material and spacing of butt blocks. Butt blocks were perferred as they overlap the upper and lower planks which helps hold the splice in shape.

Other designers preferred the scarf as long as each end was fastened to a frame.

Dave

Sun over the foreyard>

[Allen Foote]

When I repair plank ends, its due to the end of the plank ONLY, that is/has rot/damage. First, remove the whole plank from the boat. Then you can assess the actual degree of rot, look for the signs of rot migrating through the middle of the plank (mahogany will do this when slab cut, it follows through the plank, the whole width so both top seam and bottom seam will have soft areas behind the caulking bevel). If it is determined that in fact, only the end has damage then cut the end off 12 inches behind the first sign of damage (decay is the final stages of rot, rot exists where there are no signs of decay) Then, router out the back 1/3rd of the thicness. for a length of 10-12 inches and the whole width of the plank. Epoxy on a slab of wood of the same species, the thickness of the routered depth.(care must be taken when the plank end has a twist, to replicate that twist, it may mean using a piece that is 2 times the thickness and carving the twist into it.) When this cures, flip the board over and glue in a piece 1/3rd the thickness on the front. When that cures, router the end 1/3rd depth of the thickness for 5-6 past the glue joint and epoxy in the last piece. In essence you are creating a "plywood end" by 3 "veneers" and epoxy. You can see that it is alot more time & material consuming to do a proper repair...it is alot easier and quicker to replace the plank....but that means getting over the mental hurdle of "wasting" a good 90% of a fitted plank.

[ 05-26-2002, 10:09 AM: Message edited by: Allen Foote ]

[paladin]

Allen's way is pretty much the way I have done it to it...and was instructed so at the Choey Lee yard many moons ago....seemed to work well....

[Ian McColgin]

At butts and hoodends I've not had problems with in situ fixes by scarfing with epoxy. I don't do complex hook scarffs - just a nice 8:1 or 12:1 bevel. If the length to be replaced is under a couple three feet running length, you can just make it a little thick, maybe backing out where it goes over an interveening frame, and stick it in without any bendind. When you finish shaping from the outside, some grain will stand up a little so seal with CPES. If you need extra support in drawing it in, glue a bit of extra wood on the inside just a bit back from the sharp bevel edge of the planking that's in place. You can get the piece in with screws or even bolts and replace with trennels once the epoxy is dr y.

Easiest way I've found to make the bevel in the plank that's on the boat - Once you have the basic hole defined so you have a rot free inner edge, use your Japanese pull saw to slot the plank back to your mark for the bevel. I put that back about 18" on my 1-1/2" planking but I move back or forth a little depending on what else is going on in the area. Any bevel over 8:1 seems to work fine. The pull saw kerfs give a guide for what you'll whack off with your slick and mallet. Actually goes pretty easy by hand, once you're used to it, though some planks are just plain hard to get at and learning to be ambidexterous helps.

G'luck.

[Nicholas Carey]

Sometime in the last year or so, WB ran a piece on a guy in England who is scarfing planks together for restorations, but he does it a little differently. He cuts the scarf at something like 12:1 but does it at 90 degrees to the usual way -- that is to say that the taper runs from one edge of the plank to the other, rather than from one [b]side] of the plank to the other. And he cuts the scarf with a finger joint bit on the router.

This accomplishes a couple of things

</font> you get a lot of lot of glue area in the scarf.</font> The repair is essentially invisible.</font> The scarf is stronger -- the glue line is in shear rather than in tension.</font> Unlike the more conventional scarf, Lloyds evidently excuses this type of scarf from the usual rules regarding the staggering of butt blocks.
</font>Just a thought.