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Chris Pink
04-13-2010, 05:46 AM
Hi All.

I did try search but fund nothing specific to my need.

I need to make around 8 (so jig if simple, individually if not) nibbed scarfe joints in 5 x 2" oak with the scarfe on the short edge like so for the gunwhales on a working narrow boat replica;
http://www.tigerboats.co.uk/images/forum/nibbed-scarfe.jpg
I can find jigs and methods for feather edged scarfes but nothing on nibbed edges.

All hints and tips gratefully received.

Jim Ledger
04-13-2010, 06:33 AM
Make a jig for a feather scarf using a router on a wide plexiglass base. You let the thin end run out to a feather. The step is formed by screwing a stop across the jig, limiting the travel of the router. The feather ends get sawn off to form the blunt end. The slight cant in the step can be chiseled by hand into a vertical plane. Some hand fitting is required, but the basic planes of the joint are machined in.

I've never had occasion to make a series of stepped scarfs like you describe, but if were I to try, this would be my starting point. Others may have some more concrete suggestions (maybe even pictures;)).

SMARTINSEN
04-13-2010, 07:09 AM
There are a couple of ways to spell it, scarph or scarf, but not scarfe. That may influence your search results.

Or you could just listen to our very own tiechlemiester.:) (sp?)

Mrleft8
04-13-2010, 08:55 AM
I'd try looking for Ye Olde Scarfe jig...;)

gert
04-13-2010, 08:59 AM
Do you have a router table?

http://farm4.static.flickr.com/3558/3322951109_dfe34a88d3.jpghttp://farm4.static.flickr.com/3539/3323789808_6dcba03410.jpg
http://farm4.static.flickr.com/3561/3323792210_d3b5747805_o.jpg
the soup cans are lead filled; they'r just there to hold the rig down.
There is a length/weight limit on this rig.

But it works well, especialy if there are lots to do.
http://farm4.static.flickr.com/3574/3323794436_dcd838f877.jpg

5.5 Meter
04-13-2010, 10:15 AM
Gert, great jig but he is looking at 8/4 oak not 1/2 ply. I would also think that there will be some length to these boards (used for bulwarks) so try to imagine holding an 8/4 piece up.

Chris,

8/4 Oak X 5” you are going to have fun.

1) What type of fit are you looking for? At 8/4 that is going to be a long splice and the slightest variance in the wood (8/4 dimension), from one piece to the other, is going to throw off the scarf…even with jigs, when you try to mate up the pieces.
2) You may be tempted to use one jig to use on both halves of the scarf. However if the jig is not Perfect the scarphs will never match. And Oak will make the process of final hand fitting very time consuming.
3) Then, seeing that the application is for bulwarks, one would assume that there is some share to the deck line. If so, are you scarphing then cutting the share or fitting the bulwark and then cutting the scarph? The latter adds complexity because you then limit your ability to play with the fit of the scarph (retries to fit) because every retry will shorten the board and thus its for and aft location which would then change the fit to the deck/covering board that was already made…there is going to be the for and aft share as well as a bevel on the bottom to account for the angle of the deck.
4) Are you using the scarphs to account for some of the share? What you have drawn is assuming that the pieces will be glued in a straight line. Will the pieces actually be glued so that there is some curve to the bulwarks (up and down going for and aft) once all the pieces are glued together? If so you have now added some complexity to the scarph in that the scarph notch is not 90-degess to the edge but will be an angle of which has to be matched four times for each scarph (notch and feather times 2).
5) What type of appearance are you looking for? And what is the final application? Finished bright both sides? Finished bright one side? Painted both sides?
6) If it is finished bright one side and painted the other, you could then focus on the appearance of the scarph on the bright side, kind of like having an A/A or A/B side grading in plywood.
7) Will there be a cap rail?
8) And finally how long are the pieces and how long is the final bulwark and how much does it have to curve? 8/4 is going to be a lot of fun to bend and fit to the hull….

Finally, you say replica. 100% historic replica or just replica in appearance. The reason I ask is that the way I would tackle your bulwarks would be to laminate up to the 8/4 thickness, perhaps out of 5-laments (1/4, ½, ½, ½, ¼). This would allow you to glue in the curve to match the hull. Fit the inner and otter pieces separately to match the share and deck angle (while the inner pieces could receive less of an effort in fitting to the deck because they will not be seen). Stager the pieces (butts) and then use the butts of the ¼ pieces to provide the appearance of the notched scraph.

5.5 Meter
04-13-2010, 10:45 AM
Also Chris, I think you have the scarph going the wrong way. The slant part of the scarph should be on the 5” side not the 2” side.

gert
04-13-2010, 01:33 PM
only trying to show a "principal" ; stock thickness is irrelevant.

Ian McColgin
04-13-2010, 02:23 PM
Wrong scarf for a gunnel.

Remember that at least the upper corners and maybe under corners will be rounded. This scarf will put a feather edge exposed on the corner which in a well epoxied joint is not so bad for strength or avoiding splinters but will expose the visually broader glue line on a bevel, thus defeating the whole purpose of making a nibbed joint at all.

So, make a simple step scarf.

5x2 is pretty hefty. I take it this boat is something more that 20'. Is the gunnel member alligned with the planks or normal to them making a horizontal shelf? This will make a difference in issues of bending the wood. If alligned long face verticle you might get away with cold fitting and screw& glue the scarf in as you go but it were better to steam and put some bend in the stock (actually overbend a tad) first and then cut the step scarf. If the gunnel is long side horizontal, steam and bend is absolutely essential.

G'luck

Jim Ledger
04-13-2010, 02:37 PM
If it's a narrowboat, there probably won't be any bend at all. We're talking canal boats here. A full length boat is seventy feet, by about six feet of beam. However, a lot have been cut in half to make two boats of thirty-five feet, suitable for excursions.

A picture would be helpful, or just interesting.:)

lagspiller
04-13-2010, 02:56 PM
Um....
We always and as a rule whale out our scarfs by first cutting the end to measure, then marking the beginning of the scarf and finally planing the sucker down with first an electric plane, and then a belt sander. It never fails. No jigs.

If you are working with ply, then you also can use the glue lines as an indicator. A straight glue line is indicates a straight joint.

What was the problem again?

Jim Ledger
04-13-2010, 03:38 PM
Um....

What was the problem again?

A feathered scarf is a reasonably straightforward piece of work, either by hand or machine, freehand, or with a simple jig.

A stepped scarf, on the other hand, is a little more complicated to make, and requires a different approch.

Any suggestions would be appreciated.

lagspiller
04-13-2010, 05:22 PM
Aaahhhh.... sorry. I see the problem now.

I suppose you might just set a depth to your saw for the upper line and use a pencil line on the outboard end for the lower edge. Or use a bit of stock the correct height butted against the end of your scarf. Then plane in the same way I mentioned until the saw 'cut' disappeared and the outboard edge is at the line - or level with the stock.

kc8pql
04-13-2010, 06:40 PM
Make a jig for a feather scarf using a router on a wide plexiglass base. You let the thin end run out to a feather. The step is formed by screwing a stop across the jig, limiting the travel of the router. The feather ends get sawn off to form the blunt end. The slight cant in the step can be chiseled by hand into a vertical plane. Some hand fitting is required, but the basic planes of the joint are machined in.

I've never had occasion to make a series of stepped scarfs like you describe, but if were I to try, this would be my starting point. Others may have some more concrete suggestions (maybe even pictures;)).
I cut these basically the way Jim suggests, except rather than cut a feather edge off after routing, I adjusted the depth of cut to leave the flat on the end. There's not much to it really.

http://i43.tinypic.com/1z68tg4.jpg

These show the simple jig and router setup. I posted these in a thread not long ago, but I can't find it at the moment so I'll repost them here.

http://i42.tinypic.com/dwdi0g.jpg (http://i42.tinypic.com/dwdi0g.jpg)

http://i40.tinypic.com/2gsidy0.jpg

http://i44.tinypic.com/24ax35j.jpg

Gerarddm
04-13-2010, 06:58 PM
You could do a wavy Chinese scarf and not have any corners at all.

Trying to recall where I saw that- Charles Davis? Chappelle?