Scarfe Joints

[Chris Pink]

Whereas it seems fairly easy to set up a jig for various tools to make a feather edged scarfe, I can't find any reference to the 'proper' way to make a nibbed scarfe such as is in gunwhale sections.

 

 

It is straightforward to make one in a plank so the scarfe is on the longer edge but in the gunwhale sections the scarfe is on the shorter edge.

 

If there was an intelligent way to use a router and a jig this would seem favourite.

 

2 x 5" Oak onto steel gunwhale backing, no pinning in the scarfe section - although it could be square-nailed carefully.

 

All suggestions gratefully received.

Edited April 12, 2010 by Chris Pink

[Timleech]

Whereas it seems fairly easy to set up a jig for various tools to make a feather edged scarfe, I can't find any reference to the 'proper' way to make a nibbed scarfe such as is in gunwhale sections.

 

 

It is straightforward to make one in a plank so the scarfe is on the longer edge but in the gunwhale sections the scarfe is on the shorter edge.

 

If there was an intelligent way to use a router would seem favourite.

 

2 x 5" Oak onto steel gunwhale backing, no pinning in the scarfe section - although it could be square-nailed carefully.

 

All suggestions gratefully received.

 

Probably not 'proper but how I would do it:-

 

With a number to be done, it would be worth devising a router jig which shouldn't be too hard but would require a router with a fairly wide or extended base.

For just a few, mark out carefully both sides and make a whole series of saw cross cuts at appropriate depths, a small portable power saw would be good for this. Chisel off the dross, and finish with a very sharp wide paring chisel.

 

Otherwise, router out to the shallowest depth and finish with mallet & chisel (tedious).

 

Yes you could saw the cut directly by hand, but it's almost bound to need finishing because controlling the saw at that depth of cut ripping diagonally across the grain won't be easy.

 

Tim

[carlt]

My method was almost certainly not the "traditional" method but I used a biscuit jointer to make the cross cuts, Tim describes, then a 2.5" chisel to chop out the rough shape, made pretty with a belt sander.

 

The biscuit jointer is great for cutting slots at controlled depths and is a very useful tool indeed.

 

Useless for making chocolate chip cookies, though.

[capnthommo]

hi chris

i think it's a matter of using a scarfe jig and router and stopping a little short to allow space for finishing the nib with a careful saw and paring chisel. i never have to do enough to make it worthwhile setting up a jig so end up doing it the wrong way but i feel there should be some way to set up stops on a scarfe jig so it didn't end up tailing off into a feather edge. maybe some sort of router carriage and stop bar?

cheers

nigel

[Dovetail]

It is possible to make a router jig to cut the joint but depends on how many joints you have to cut as the jig will take time but once made will cut both sides of the joint.

 

If you imagine a flat board sitting on the plank to be machined and that flat board had a large square hole in it as big if not slightly bigger than the joint to be cut.

 

You then fix a thin piece of ply to the bottom of the router with a hole in it for the cutter this piece of ply is to stop the router falling through the first piece of ply with the big hole in it.

 

So if you are still with me the first piece of ply is tilted to the correct angle required and fixed in place folding wedges are good for this once the correct angle is achieved the wedges and ply can be screwed together.

 

So as the router moves down the ply it gets deeper into the wood and routers the joint I hope this makes sense

[RLWP]

<snip>

Useless for making chocolate chip cookies, though.

 

Of course it is, silly. It's a biscuit joiner for repairing biscuits

 

Richard

[Chris Pink]

My method was almost certainly not the "traditional" method but I used a biscuit jointer to make the cross cuts, Tim describes, then a 2.5" chisel to chop out the rough shape, made pretty with a belt sander.

 

The biscuit jointer is great for cutting slots at controlled depths and is a very useful tool indeed.

 

Useless for making chocolate chip cookies, though.

 

hmm, not got (or thought of) biscuit jointer. I guess I could use a router with a thin straight bit to cut controlled transverse cuts (or steps) then chisel. Especially if I make them all at the same time.

 

If I remember rightly I've got 8 pairs to make so on the cusp of a jig.

 

Mr Dovetail's method could be a goer too if I can get the angle wedges accurate enough and clamp it to the workpiece securely.

 

thanks all.

[starman]

Having lived in a couple of old timber framed houses I've always marvelled at the skills of the 17th century carpenters. And to think they managed all those scarfes, mortises and lap dovetails without biscuit jointers or routers.

(Me, I can barely cut straight and I need every powered aid possible.)

[WotEver]

Mr Dovetail's method could be a goer too if I can get the angle wedges accurate enough and clamp it to the workpiece securely.

Chris - note that the sliding wedges in that description were only temporary to get the correct angle. Once you're there you glue-screw it all together.

 

It read as a good plan to me, but I probably wouldn't bother with wedges, I'd draw out a full size rod on a piece of board and take measurements from that. One thing to note however is that by using an angled jig, the little steps at the end of the scarf joint will also be angled. This won't actually matter, just as long as the same angle is used to cut the boards to length, say with a mitre saw.

 

Tony

 

Edit to say that to make the plywood sub-base for the router, unscrew the plastic face from the router base, and use that as a template for the hole positions. I apologise in advance if this is teaching you egg-sucking.

Edited April 13, 2010 by WotEver

[Chris Pink]

Egg sucking not quite mastered - I didn't quite get this bit;

 

One thing to note however is that by using an angled jig, the little steps at the end of the scarf joint will also be angled. This won't actually matter, just as long as the same angle is used to cut the boards to length, say with a mitre saw.

[WotEver]

Egg sucking not quite mastered - I didn't quite get this bit;

I've never been the clearest describer-of-stuff.

 

To cut the scarf joint with a jig basically means that your router will be sitting at some angle away from the vertical - say 7 degrees. At the top of the jig will be a batten to act as a top fence for the router; this will give the 'step' at the top of the scarf joint as per your original drawing. However, because the router is angled away from the vertical, so your 'step' will be undercut by the same angle.

 

So, if your slope is at 7 degrees, then when you cut the next board, you cut the end at the same 7 degrees with a tilting mitre saw so that it will match your step neatly.

 

I'll do a quick sketch and put it up to show what I mean.

 

Tony

[RLWP]

You could just square the seven degree undercut off with a chisel of course

 

Richard

[WotEver]

You could just square the seven degree undercut off with a chisel of course

 

Richard

Yes, but that's difficult to get neat.

 

Edit to add picture

Edited April 13, 2010 by WotEver

[RLWP]

This is boat building, not cabinet making

 

Richard

 

[WotEver]

This is boat building, not cabinet making

Okay then - hew your timber and buy a box of marineflex tubes

 

That better?

[Dovetail]

I've never been the clearest describer-of-stuff.

 

To cut the scarf joint with a jig basically means that your router will be sitting at some angle away from the vertical - say 7 degrees. At the top of the jig will be a batten to act as a top fence for the router; this will give the 'step' at the top of the scarf joint as per your original drawing. However, because the router is angled away from the vertical, so your 'step' will be undercut by the same angle.

 

So, if your slope is at 7 degrees, then when you cut the next board, you cut the end at the same 7 degrees with a tilting mitre saw so that it will match your step neatly.

 

I'll do a quick sketch and put it up to show what I mean.

 

Tony

 

Well spotted Tony keeping the slight angle if we are saying say 7 degrees will actually gives a slightly stronger joint as they would sort of lock together.

 

To get the jig to work you have to want to cut the joint that way because although a reasonable description of the jig and the points Tony spotted you will have to tweak the jig to get it just right and adjust it to a system that is good for you.

[RLWP]

You've got me onto one of my soapboxes now, about using powertools where the job was always done quickly and easily using hand tools in the past. I'm going to get off it before I get carried away...

 

Richard

[Dovetail]

You are right Richard and I have played with wood since leaving school only 29 years ago and still playing and there is nothing better to hand cut timber with hand tools but in the past its not the case that they decided not to use the power tools its the case that they had no power tools and if they had them ?

[RLWP]

Yes, of course. And if I were turning out wooden boats for a living, then I'd have a shop full of power tools too.

 

Richard

[WotEver]

Yes, of course. And if I were turning out wooden boats for a living, then I'd have a shop full of power tools too.

 

Richard

Well get off yer box then

 

Is it a wooden box?

[carlt]

I have to say that all this building jigs and faffing about would probably take longer than just cutting the joint by hand.

 

I'm assuming it is a scarf for the gunwales of a metal working boat so the tolerances are pretty huge.

 

Some builders didn't even bother with a scarf at all, on the gunwales, preferring a butt joint filled with Charlie, to allow for expansion.

[Paul H]

I've been told that gunnels were not originally scarfed at all.

 

The proper way is butt joints with a couple of diagonal wooden pegs/dowels from the side to hold it line but allow for some expansion - and of course plenty of charlie, pitch or similar.

 

With the scarfe joints illustrated earlier in the thread you'd get a very vulnerable "thin end of the wedge" which if it moved in contraction/expansion could catch ropes etc. or splinter off.

 

Also gunnels were to some extent sacrificial and when damaged it had to be easy to let another length in.

 

Paul

Edited April 13, 2010 by Paul H

[Osprey Sprinkler]

I know sweet Felicity Arkwright about traditional boat construction but I've cut plenty of scarf joints in my time. Routing using a jig is entirely possible but a bit OTT unless it is cabinet work you are after.

 

I would cut a simple plywood template to mark an identical Z shaped profile on the 2" side of each plank, then cut the entire joint on a band saw. You will need a roller stand to support the other end of long timbers (fifteen squid from Axminster Power Tools). The plank will be a bit wobbly because it is standing on its narrow edge while you saw - holding it against a square offcut cures this.

 

Use the widest blade the saw will take, with fewest possible teeth per inch - 4 TPI skip tooth is good. If you don't have a band saw that will take 5" depth, ask around in the pub. Every secondary school has one, as do local sawmills and amateur enthusiasts, and all are open to bribery with beer. Once, in desperation, I even enrolled on a woodwork evening class just to get access to their machinery. If you do borrow a machine, buy a new blade for the job (only £10 to £15); you get the benefit of a fresh, clean cut and you've done the owner a favour.

 

Failing that, as Carl points out, cutting the joints by hand really isn't a big job and it's good for the soul. Use a decent rip saw for the long, shallow cut (some dodgy general purpouse saw from Homebase really will be hard work) and make sure it is sharp. Scribble candle wax on the blade if it binds in the cut, and use plenty of lubrication for the operator.

 

The angled undercut mentioned by others is generally a good thing, discouraging edges from popping up as the wood moves over time.

 

I seem to recall that Alan Herd was shown using scarf joints on Dover - if he can do it, you will find it a doddle.

 

Ash

[WotEver]

I seem to recall that Alan Herd was shown using scarf joints on Dover

As I recall the episode, he was showing someone else doing it

 

edit for tryping

Edited April 13, 2010 by WotEver

[Natalie Graham]

Once, in desperation, I even enrolled on a woodwork evening class just to get access to their machinery.

 

I'm picturing the reactions of the other students as they work on their bookshelves and bedside tables while a wooden narrowboat takes shape in the school workshop. Not to mention when you start boiling up pitch and cow dung in the corner.