yikes, the scarf joints

So I received my passagemaker plans in the mail yesterday, and I'm scared.  I guess I didn't realize that there's be, you know, JOINERY involved.  I really don't have any skill with planes to speak of.

Any pointers?


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RE: yikes, the scarf joints

Ha!  Welcome to the club!

Just a few minutes ago I ordered a 1/2 inch dovetail template (less than $20 shipped) to try out the puzzle joint method on this page:

http://www.duckworksmagazine.com/06/howto/puzzle/index.htm 

I'm a few weeks into a Wood Duck 12, and so far I have one ugly but strong scarf joint made with a hand plane, and several pieces of various circular saw jigs that didn't work as well as I had hoped.  The last jig created a scarf slightly better than a wood chipper would do.

All kidding aside, I would try some practice scarfs on scrap wood (preferably the same as you're using for your kayak) with a plane, and see how you do.  I've determined that I can do a satisfactory job strength-wise, but for an unpainted finish I've quite a ways to go.  I'm going to try the puzzle joints because I think I can do a much more precise job with my tools and skill level.

That's the input from a no-talent hack...hopefully you'll hear more from those who can do a perfect scarf in a matter of minutes with "a few strokes with a sharp plane."

 

 

 

 

RE: yikes, the scarf joints

As mentioned in the post above, the key element is having a sharp plane. If you have a plane already, you need to make a small investment in sharpening materials ranging from cheap (Scary Sharp sandpaper method) to appalling (Japanese natural water stones, Tormek sharpening system) When using stones and such you also need an angle guide, again ranging from cheap (a small block of maple cut to the right angle) to fancy honing guides.

The plane also needs to be "fettled". This is the process of making sure the sole is flat, bed is square to the sole, etc. High quality expensive planes such LieNeilsen and Lee Valley already have this done but even the cheapest old plane can be made servicable with a file, emery cloth on a flat surface and elbow grease. 

Once you have it fettled, the real critical skill in using planes is knowing how to adjust it. You learn this by trying out different settings on the plane and observing the results. Adjustments are always very small and subtle. You "sneak up" on the desired cut.

Once sharpened and adjusted, making whispy shavings is a snap. For plywood you don't even need to read the grain. Planes cut best when they are on a surface that supports their soles for the full length. The best way to accomplish this when cutting scarfs is to cut all similiar scarfs at once. Put all the blanks in a pile and then stagger back the edges by the distance dictated by the ratio of the scarf. For instance if if the ply is 1/8th and the ratio is 1:8 then the stagger is 1".  Draw a line on the top blank 1" back from the edge. If you have  four blanks in the pile you now have a "surface" formed by the top part of the edges. If you have less than four use scrap on the top and bottom. Start planing away the edges with uniform strokes. Observe the lines of the plies as they emerge. Straight lines indicate even strokes, wavy means uneven. You want straight. Keep planing until you reach the line you drew on the top blank. At this point you should have nicely formed scarfs. Don't worry about perfection because the cut surface is inside and epoxy will close gaps. If the scarfs have wavy edges that look bad when put together cut 'em off and try again.

 That's what great about plan building, there are no ruinous mistakes.

-Dusty

RE: yikes, the scarf joints

I agree with Dusty - perserve keep trying don't give up on the Scarf - should be a CLC shop tip showing how its done & in 3 or 4 mm ply its a fairly quick process trust me I've just cut & glued my scarfs for a WD12  - got it right after 3 attempts & i'm reasonably satisfied - as a chippie i should have got it right 1st time but over confidence...

The puzzle joint looks good & a desirable feature -I did consider buying a dovetailing unit & even thought of creating the joints with a home-built template but it seemed like a bit of ginning about & just easier to scarf

RE: yikes, the scarf joints

So Dusty, you recommend cutting lengthwise down the board(s), rather than across?

RE: yikes, the scarf joints

If you have any woodworking friends or a woodworking shop nearby, you could have them make you want amounts to a "shooting board" whereby you would just clamp your plywood into the board and use it's sides for a guide to accurately scarf your plywood. It would be easy to make as long as you settled on what angle you wanted the scarfs to be.

RE: yikes, the scarf joints

I was also a scarfing newbie on my Pocketship build. Pocketship has some large scarfs (24") and my hand planing attempts were dismal. This link to my blog

http://pocketshipadventure.blogspot.com/2009/04/zen-of-scarfing.html

outlines the 2 scarfing jigs I found online that worked very well for me. There are pictures of the very easy to construct jigs and links at the bottom of the post to the original web sites with instructions how to build and use the scarfing jigs.

 

RE: yikes, the scarf joints

So Dusty, you recommend cutting lengthwise down the board(s), rather than across?

Sort of depends on the size of your plane and the distance of the stagger. (almost any bench plane will work along with most block planes) If you have a #4 bench plane or larger and the stagger is small you can start from the sides, which will remove material faster. If you have a small plane and large stagger definitely start  cutting from top to bottom. Regardless of plane or stagger size, as you get close to the finished scarf, your cuts should be from top to bottom.

I forgot to mention that the bottom blank should be supported by a piece of 1x softwood scrap that's large enough to support the area being cut. The edge of the scrap should line up exactly with the edge of the bottom blank and the whole pile should hang a little of the edge of your bench. This will allow clearance for the plane.

Also, as decurtis mentions, if you're going to cut a lot of scarfs, making a jig makes a lot of sense. I don't bother with a jig for a small amount of scarfing because precise set up can be rather fussy but when I'm ramping up for a big project I definitely reach for it.

RE: yikes, the scarf joints

I may try the jig from above.  I see it cuts the bottom surface, which I had considered but didn't try.  Two out of three of the contraptions I did try (each of which I built) relied on the saw's built-in blade tilt to get the angle.  And one problem was that I was using 7.2 degrees instead of the less-shallow (and more forgiving) 6 degrees mentioned at the link above (which I don't believe yields an 1:8 scarf, but if it has worked for someone else...)

I'll also be trying some more planing to see if I can hone my skills a bit. 

The way things are heading I'm going to end up with a scarf-butted puzzle joint, rough-cut with a circular saw, finished with a plane, and reinforced with fiberglass.

 

 

RE: yikes, the scarf joints

I wonder if an 8:1 scarf joint isn't overkill for our needs. The joint only needs to be as strong as the wood it connects. I've used taped butt joints on two boats, including a 12-foot sailing skiff, and never had a joint failure. A simple 45-degree bevel might be all we need, and would certainly be a lot easier for an amateur to make. Has anybody tried this, or tried test panels of various joint types? -Wes

RE: yikes, the scarf joints

Just from the advice offered thus far, you can see that successful manual cutting of scarf joints has many factors.  Type of block plane, angle of blade, sharpness of blade, position of cut, skill of user, phase of the moon and above all, lots of practice and wasted wood.  It's unfortuate that this intimidating step comes so early in most plan built S&G kayak projects(yikes indeed!).  A less that perfect result will leave the first time builder feeling like they bit of more than they could chew when.  I decided right away to go with a jig. 

http://www.flickr.com/photos/algonquinpaddler/278624487/sizes/l/

It took me an afternoon to plan out and a couple of hours to build.  I figure I would have spent more time practicing with the plane.  I have since used the jig on 3 kayaks, MDF trim for the house and few smaller projects.  It is easily adapted to cut the narrow panels of a CH16 or the very wide bottom panel of a MC16.5.  The edges feather out to nothing which is great when gluing the panels - nice flat, clean, straight joints. 

I know I've posted this before, but it seems like this step in the project is the greatest hurdle for the beginner and it need not be.  You are not lacking in kayak building skills if don't have a knack for using a block lane.

If you are intested in building a jig and want more detail than shown in the picture, email me at sjacobson2@cogeco.ca

RE: yikes, the scarf joints

The last post was made by me....don't know who Owen is?

Chris J.

RE: yikes, the scarf joints

Sorry Owen, I see now you initiated this thread.  I'm using two computers here and when I post from one it fails to populate the "submitted by' field.  Not sure what's going on.  Maybe a Mac thing.

RE: yikes, the scarf joints

Sorry if I'm cluttering the thread needlessly, but please ignore everything I said about 6 degrees vs. 7.2 degrees above.  Turns out my geometry is as weak as my woodworking.

RE: yikes, the scarf joints

"A simple 45-degree bevel might be all we need, and would certainly be a lot easier for an amateur to make. Has anybody tried this, or tried test panels of various joint types? -Wes"

Yes!  My side joints were all cut on a 12" compound mitre saw at 45 degrees; my bottom joints (two) are butt joints only.  All joints got two layers of glass (1st one on the bias, second parallel) and I was very happy with the results.  The joints aren't clean enough to clear coat (my opinion) but I've got a paint scheme that will eliminate them from the otherwise all-wood finish.  I wobbled those 17 ft long strips all over my garage and they never popped, and once wired together they attain the strength of the overall shape.

Larry

RE: yikes, the scarf joints

"A simple 45-degree bevel might be all we need, and would certainly be a lot easier for an amateur to make. Has anybody tried this, or tried test panels of various joint types? -Wes"

Yes!  My side joints were all cut on a 12" compound mitre saw at 45 degrees; my bottom joints (two) are butt joints only.  All joints got two layers of glass (1st one on the bias, second parallel) and I was very happy with the results.  The joints aren't clean enough to clear coat (my opinion) but I've got a paint scheme that will eliminate them from the otherwise all-wood finish.  I wobbled those 17 ft long strips all over my garage and they never popped, and once wired together they attain the strength of the overall shape.

Larry

RE: yikes, the scarf joints

i think I could swing the 8:1 bevel on a 24" panel, but the Passagemaker instructions call for scarfing a 4'x8' panel to a 4'x4' panel.

 I''d build a  jig to use a router, but at 4' wide that's a project in and of itself.  Maybe I should just aim for a sailing kayak?

 I could def manage a 45degree bevel:  I have a friend with a panel saw that he build out of a skilsaw...  What does CCL have to say about that?

 

RE: yikes, the scarf joints

Owen,

I mis-read your original post (was focused on Wes' question).  I didn't realize you were scarfing that large a sheet for the Pocket sailship.  I'm not sure I'd recommend a 45 degree "scarf" on that large a surface spanning that size of a boat.  My 45's spanned 7 inches at most, for a kayak (4mm Okoume ply).

Sorry for my confusion,

Larry

RE: yikes, the scarf joints

The circular saw jig I used produced exactly a 8:1 scarf on 1/4 inch plywood but would do less than that on 3/8". Again , I found the jig very useful on Pocketship's scarfs which I think are larger than the Passagemaker or any kayak.

Dave C 

RE: yikes, the scarf joints

So, i messed witha jig for a while, and just never really got it to the point where I liked the results.  I broke down, sharpened up the plane and gave it a go.

The intructions were right, it really isn't that hard.  The only evidence of the joint is going to be the glue line...

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