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Scarfe Joints


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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. :lol:

 

What a lovely image! It's a long time ago now but I did bring in the best part of a tree, one or two slices each week, tied to the car roof. The other students thought it was great - they would give me a hand lugging it in before it was sawn up and machined to size. A few of them also got the bug when they realised they could find lovely wood dirt cheap in the rough at sawmills. But I did draw the line at pitch and cow dung.

 

Chris - of course you're welcome to come and use my bandsaw as well. But I'm based near Gatwick Airport so, unless your boat is on the Wey and Arun :lol: , I doubt if this is much use to you.

 

Ash

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Not being a wood butcher, If you can't weld,braze,solder,rivet, I am not interested and leave all the woodwork to those that can. However I do understand joints can someone explain why it has to be a stepped scarfe joint and not a half lap joint? the latter being able to be done with a router.

Edited by Big COL
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....made pretty with a belt sander.

Im going to buy a belt sander on friday to do a job on the wheelhouse roof, im hoping for many hours and hour of enjoyment turning things into dust between then and packing up. So much im actually look forward to it right now.

- Its going be like the first time i was allowed to use the chain saw, aged 12 i think, all over again. (well ok, maybe not that good, but you can dream!)

 

 

 

Daniel

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Why a router? You can cut either of those joints with a saw!

 

Richard

 

I was only following on from the o/p suggesting the use of a router. I still cannot see a difference in strength between a scarfe and a half lap joint. I thought a scarfe joint was like an interlocking half w so the joint can't be pulled apart.

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I was only following on from the o/p suggesting the use of a router. I still cannot see a difference in strength between a scarfe and a half lap joint. I thought a scarfe joint was like an interlocking half w so the joint can't be pulled apart.

 

Ah, but a scarf is a boatbuilding joint, a half-lap is carpentry :lol:

Scarfs (scarves?) come in a vairety of styles, you're probably thinking of a 'hooked scarf'.

The scarf is easier to make watertight, and less likely (I think) to split along the joint line. If I were doing one for a gunwale joint I would include a layer of boilermaker's felt, or chalico as a minimum, in the join.

Despite what someone (Paul H?) said earlier in the thread, I have commonly seen 'old' gunwale joints of this type, maybe they weren't original on GU metal hulls though.

 

Tim

Edited by Timleech
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Despite what someone (Paul H?) said earlier in the thread, I have commonly seen 'old' gunwale joints of this type, maybe they weren't original on GU metal hulls though.

I think it varied from builder to builder.

 

I know of one fairly well known wooden boat "restorer" who insisted vertical scarfs were the correct way and no original gunwales existed, to prove his point, despite him having owned two wooden boats that were known to be completely unrestored.

 

To be honest I can't see what scarf joints would add, structurally, when bolted down to a metal sided boat.

 

They may serve a purpose when spiked to planks, though, but I think their main role was cosmetic.

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A (non-stepped) scarf joint has two advantages over a half-lap.

 

1. It's easier to cut (and therefore invaiably neater)

2. More importantly, it's stronger.

 

A half-lap has the entire thickness of the board as an end-grain to end-grain glue line, plus a large area of face-to-face glue line. End grain never glues strongly. A (non-stepped) scarf joint has a more or less 100% face-to face glue area with no end-grain glue line to fail.

 

The stepped scarf joint as per the OP's question is a half-way house between the two.

 

Both half-lap and scarf joints need to be cut with a jig if you want to make a good, fast and accurate job of it. Otherwise it's a case of cutting oversize and cleaning back to the scribed line with a block plane.

 

I have absolutely no idea whether it's right or proper to use either for gunwales, I'm just addressing the 'woodwork' side of the question.

 

Tony

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Many thanks for the bandsaw offers, unfortunately neither are near to my wood, though I have been looking for an excuse for one of those cheap but good Axminster bandsaws. Maybe it comes a step nearer.

 

The only reason for scarfe is that my 'pattern' is a wooden motor that has them done like that. I guess the half-lap is a much quicker option. It's all bolted rather than glued. The scarfe looks a bit prettier too.

 

I think an overlapping joint is likely to degrade more gracefully than a butt joint, which won't take very long to become a void in the gunwhale. I know this from experience.

 

...so given all the replies (thank you) I think feather edged scarfe using a simple jig on a bandsaw, whether bought of borrowed with the nib cut after.

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Both half-lap and scarf joints need to be cut with a jig if you want to make a good, fast and accurate job of it. Otherwise it's a case of cutting oversize and cleaning back to the scribed line with a block plane.

 

I have absolutely no idea whether it's right or proper to use either for gunwales, I'm just addressing the 'woodwork' side of the question.

Wooden narrow boat building to wooden yacht building is like what pub garden furniture is to Chippendale, though.

 

Tolerances are purposefully coarse to provide rom for caulking gunk and to take the stresses of being manhandled round the canal system.

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Wooden narrow boat building to wooden yacht building is like what pub garden furniture is to Chippendale, though.

 

Tolerances are purposefully coarse to provide rom for caulking gunk and to take the stresses of being manhandled round the canal system.

A fair point, well made :lol:

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Many thanks for the bandsaw offers, unfortunately neither are near to my wood, though I have been looking for an excuse for one of those cheap but good Axminster bandsaws. Maybe it comes a step nearer.

Don't get the three wheel one. They're just not tough enough for the sort of lumps of wood you'll be using.

 

The 2 wheel ones are far stronger, though you do lose some throat depth.

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I did not want to complicate this thread so I have staryted a new one - please see 'What wood', I look forward to all your comments.

Hmmm... where?

 

Edit to say - oh, there! Both of them :lol:

Edited by WotEver
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