Nibbed scarf

[m2c1Iw]

I'm in the process of making side decks for my Coquina and using shortish stuff so two scarf joints are required each side in planks around six inches wide.

As there is no room for error (I'm using Huon pine very expensive and very scarce) I'm looking for tips on laying out and cutting a nibbed scarf. I've already decided a practice run is a must.

Thanks
Mike

[Mrleft8]

Look at "The Art of Japanese Joinery".
Lots of good (Mind boggling in some cases) ideas on scarf joints.

[Draketail]

Mike,

I'm just getting to the same point on my draketail. Sometime Wednesday night I should be able to post pictures.

In the meantime, my thoughts are to make a pattern for the scarf out of 1/4" plywood, making sure to get the lines good, straight, and square. Then put the first piece of pine side deck in place to make best use of the material. Align the jig on top of the side deck piece till it suits you and tack it in place. Then trace and cut the first half of the scarf. Clamp the board with the cut scarf back in place. Then turn the jig over and butt it against the cut scarf. Now lay the next piece of side deck in place. Align the new side deck piece to suit. Now snug the jig up against the scarf, raise it up to the underside of the new piece and clamp the jig to the new piece. Remove the new piece and cut the other half of the scarf. A practice run with cheap shelving boards wouldn't be a bad idea...

At least that's the theory as best I can figure it out. I'll let you know how it works in practice later in the week......

Grigg

[rob]

It is a bit easier to get a really good tight fit along the nib if you only place the nib on one side, top in this case. That way if there is any slight misalignment it wont hold your joint open on the visible face, and small fitting adjustments can usualy be limited to a single mating surface...with 2 nibs you almost always have to tweak the slope as well as the nibs if you start fussing with it. the board is also a bit stronger this way, as the nibs are definite weak points.

It's easy to jig this (or any) scarf joint up with a sloped sled jig and a plunge router, but for just a few it would be just as quick to cut them by hand. Some folks would rough them out on a band saw then tune them in with chisel/slick and rabbit plane, but I wouldn't think your deck is thick enough to bother with all that.

Layout and cutting are pretty much what you would think. end cuts parallel and as close to equally dividing the angle at which the boards meet as possible. sloped section from 8:1-12:1 depending on your requirements.
nib is pretty slight usually maybe 1/16"-1/8" on a 3/4" board...again depends on application. Mark out both sides, nibbed end, and face cuts.

It can be a little tricky to keep a nice flat plane on the slope as it meet up to the drop cut for the nib. you will have to work from the side with a wide chisel or rabbit plane and check your work in both directions(cross and long grain) with a good straight edge.
Cut one board at a time, tack in place to get the location and angle of the end cut for the next board, then just repeat you layout. This is again easier if you only have a nib on one side (the top and first cut), as the mate can be cut as a quick normal scarf of the correct slope ending at the nib thickness rather than a feather edge.

[m2c1Iw]

Mike,

I'm just getting to the same point on my draketail. Sometime Wednesday night I should be able to post pictures.

In the meantime, my thoughts are to make a pattern for the scarf out of 1/4" plywood, making sure to get the lines good, straight, and square. Then put the first piece of pine side deck in place to make best use of the material. Align the jig on top of the side deck piece till it suits you and tack it in place. Then trace and cut the first half of the scarf. Clamp the board with the cut scarf back in place. Then turn the jig over and butt it against the cut scarf. Now lay the next piece of side deck in place. Align the new side deck piece to suit. Now snug the jig up against the scarf, raise it up to the underside of the new piece and clamp the jig to the new piece. Remove the new piece and cut the other half of the scarf. A practice run with cheap shelving boards wouldn't be a bad idea...

At least that's the theory as best I can figure it out. I'll let you know how it works in practice later in the week......

For sure I'll wait for your pics thanks, been following your build very impressive and putting a lot of skills to work.

It is a bit easier to get a really good tight fit along the nib if you only place the nib on one side, top in this case. That way if there is any slight misalignment it wont hold your joint open on the visible face, and small fitting adjustments can usualy be limited to a single mating surface...with 2 nibs you almost always have to tweak the slope as well as the nibs if you start fussing with it. the board is also a bit stronger this way, as the nibs are definite weak points.

It's easy to jig this (or any) scarf joint up with a sloped sled jig and a plunge router, but for just a few it would be just as quick to cut them by hand. Some folks would rough them out on a band saw then tune them in with chisel/slick and rabbit plane, but I wouldn't think your deck is thick enough to bother with all that.

Layout and cutting are pretty much what you would think. end cuts parallel and as close to equally dividing the angle at which the boards meet as possible. sloped section from 8:1-12:1 depending on your requirements.
nib is pretty slight usually maybe 1/16"-1/8" on a 3/4" board...again depends on application. Mark out both sides, nibbed end, and face cuts.

It can be a little tricky to keep a nice flat plane on the slope as it meet up to the drop cut for the nib. you will have to work from the side with a wide chisel or rabbit plane and check your work in both directions(cross and long grain) with a good straight edge.
Cut one board at a time, tack in place to get the location and angle of the end cut for the next board, then just repeat you layout. This is again easier if you only have a nib on one side (the top and first cut), as the mate can be cut as a quick normal scarf of the correct slope ending at the nib thickness rather than a feather edge.

A great description and leaving the underside feathered well worth a thought.

Thanks for the responses.

[Draketail]

I think rob and I are describing scarfs that are at 90 degrees to each other...

[rob]

after rereading your post draketail I think you are right. Scarfing the sidedeck/subdeck in the way you describe (over the width as opposed to thickness) often gets done when the side deck is a substantial structural member as in the harpin on a friendship sloop or other workboat types with large open cockpits. usually this is done with thick stock and then through bolted at each joint. And most often I have seen canvas or a laid deck over this strucutre...
It also gets used a lot on covering boards in combo with a laid deck.

On a boat like the cociquina, the side deck is not structural in the same sense. I assumed the OP's scarfs are running the thickness of the board. And nibs were being used to give a clean joint line when left bright, one that can be sanded down with time/use...that's why it is only needed on top.

I made several assumptions....always a dangerous thing!

[m2c1Iw]

Picture is worth a thousand words, here is the pattern on the stock. Yes the joint is running the thickness to give a clean line for a bright finish and Grigg read your post a couple of times and the penny dropped eventually your joint is across the width.

[Draketail]

Yep, my instructions were for across the thickness. And rob is right, I'm trying to make the side decks along the open cockpit of the draketail out of a single piece for structural reasons. The scarf is needed fore and aft to finish out the side decks....

I expect a tapered jig and a router are your best bet for repeatability.

[chuckt]

I'd love to see pics of some jigs if anyone has them. I know I've seen one for a router on the forum but a google search of the forum failed to turn it back up for me.

[Gerarddm]

Naval architect Charles Davis, in one of his classic books on how to make wooden model ships ( I think it was the one about building the Revolutionary War brig Lexington ), talks about " our Chinese brethren" and their wave scarfs as seen on junks. The lack of corners made them strong, he noted, and the adjoined plank halves could not ride up over each other due to the two humps in the wave pattern. Ingenious.

[Draketail]

As promised, here are pictures of making a scarf across the width of the covering boards on my draketail build. In the picture below the 16 ft covering board running the full length of the open cockpit has been put in place and indexed for location with three screws. Now I need to scarf on a shorter piece of plank (3'6") for the stern. The scarf pattern is located tengent to the curve of the stern and screwed to the cockpit side plank with a couple of drywall screws.



Then the plank is trimmed to the scarf pattern using a bottom bearing flush trim router bit. The one inside corner needs to be cleaned up with a sharp chisel to remove the radius left by the router bit.



The cockpit side board is then reinstalled in the same place using the three index screws. The scarf pattern is then flipped over and snugged up to the plank.



Now the short plank for the stern is positioned as required and screwed to the scarf pattern underneath.



The plank with the pattern attached is then removed and trimmed with the router.



And finally the two plank halves of the scarf are fit together and screwed in place. There is still some trimming to be done on the edges of the covering boards.



This is the first time I have tried this method. Six covering boards including eight scarf havles were fit in about 3 hours. None of the scarfs needed any additional tune up. The stern and bow planks fitted to the initial cockpit side plank and returned exactly to their reference marks after the scarfs were cut. Seems like a success to me...

[Gib Etheridge]

An alternative would be to rip your stock into strips, join the strips to full length with simple sliding compound miter saw scarfs across the width, plane the strips to a uniform width in the thickness planer, edge glue them together to match the pattern then run them through the thickness planer.

I'll look for the nibbed scarf jig for you.

[Gib Etheridge]

Here it is.

http://forum.woodenboat.com/showthre...-Scarfe-joints

You can use this jig to join your strips to full length to obtain a less visible scarf joint.

[m2c1Iw]

Thanks for posting that link of the jig Gib and your suggestion re stripping the deck. To be frank I don't think the Herreshoff Manufacturing Co would have stripped the deck though. I'm not trying to achieve an ultra accurate replica after all it is glued lap and while the laid deck look would be nice I've decided to practice the joinery and hopefully using a layout pattern I'll acheive a reasonable result. Failing that I think I can produce a nib on the top surface and feather on the underside. The thing is the curve of the deck produces an added level of difficulty for this joint as the alignment of the nib cuts becomes an issue. I think by roughing out the stock first, marking out while the stock is pinned in place using a pattern of the joint cuts and cutting one side of the joint at a time it should be possible, we'll see. I'll report back later but it may be a couple of weeks away we are flat out at the moment.

BTW I'm heartened by Mr. Ledger's comment "A stepped scarf, on the other hand, is a little more complicated to make, and requires a different approch. Any suggestions would be appreciated." I don't feel quite so inadequate now.

Thanks for the pics Grigg, nice idea and great result.

Mike

[davebrown]

I think this was a good way to do it. By the time I got to my decks, I was somewhat burned out from making lots of drilled hanging knees, which took four times as long as it should hvae and saved me a half pound of weight. So I stripped mine.

[m2c1Iw]

Scarf cutting day today first job was to layout the joints using a full length pattern of the deck.



Then mark the joint location and cut the boards to length. Anyone see a problem with this clamping fortunately I noticed as I started the cut.



Next find a piece of scrap and plane sides exactly paralel at 65mm the length of the scarf then mark out both the width and the ramp with a knife.



Using the marking scrap as a fence set just a smidgen over the marked line then cut a trench for the nib.



With the depth of the nib cut select a weapon of choice in this case a #78 rebate plane and remove the waste I could have rough cut on the bandsaw but I'm chicken.

cont.....

[m2c1Iw]

With the scarf cut all that's left is a trim and a few test fits and a bit of tweaking.



Actually after much tweaking finally a completed nibbed scarf joint.



Repeat above three times and you get a couple of decks ready for final trimming and fastening.



Mike

[Draketail]

Well done!