Scarf joints

I am new to boat building but since deciding to build a drift boat it is about all I can think about. I have good basic wood working skills but have never had to deal with a scarf joint. This is the most intimidating part of the build for me. The only method I have read about involves a 12:1 taper of the mating edges and is done with a hand planer or sander. Neither seems like an accurate way to provide a perfect mating of the surfaces with a less than obvious joint. Is there a way to do this with a router and a jig to guide it. I have seen some pictures that appear to show a scalloped edged joint. Is this a method of stepping the laminated layers rather than a long taper. Any advise or direction to existing forums would be very helpful.
thanks,
GS ZOLL

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Permalink Reply by Mike Baker on January 18, 2010 at 6:22pm
Welcome,
It is true that the scarf joint is intimidating at first. I think you would be surprised at how accurate the joint is when cut with a sharp hand plane. I use a 22" jack plane. If you don't have Roger Fletchers book yet I would highly recomend it. He describes how to cut the joint far better than I ever could. As far as clamping it do an intenet search for Brian Dixons scarfing jig he has a great way to clamp it. I also like to use System three T-88 for glueing.
Hope this helps
Mike
http://www.bakerwooddriftboats.com
Permalink Reply by Randy Dersham on January 18, 2010 at 9:13pm
Yes, we run the wavy scarf at the shop; however, it is cut with a CNC router and run a series of wavy steps about .062 or 1/16 of an inch deep each step and each step has a 3/4 in face giving us a 12:1 scarf.

The wave would be very difficult without the CNC. It is much easier to plane or sand a hand scarf. It sounds intimidating but the feathered edge glues easily and once you do one you will get the hang of it. Practice on a couple of scraps and you will be good to go in no time.
Permalink Reply by Josh on January 19, 2010 at 7:18am
I too was worried about cutting the scaft joints when I first started my build a few years back. I ended up purchasing the west systems scarfing jig the mounts to the bottom of a circular saw. It took a bit to make sure the measurements were correct when mounting it but the scafts turned out perfect and only some very minor sanding was required. I used it on plywood up to 1/2" thick. It'll will leave a little ridge on 1/2" plywood but doesn't take long to knock it down with a sander.





Josh
Permalink Reply by Dave Z on January 19, 2010 at 8:11am
I've done all mine by hand. You can clamp the two pieces and use a belt sander or a very sharp plane. Spend alot of time sharpening your plane, stropping it on leather and adjusting the blade untill it is perfect. This can be an art in itself. However, when doen porperly you can cut beautiful scarfs in no time. I prefer to do it by hand, as I do not have a CNC nor a scarfing jig. I believe that doing it by hand gives you way more control than using a belt sander too.

If you are intimidated by it, Take Mikes' advice and practice. What you can do is make your rock guards first- scarf them up, it will be easier to handle than a full sheet of plywood. check my blog for pics in the archives.. www.thtchronicles.blogspot.com


Clamping- I used a method which involves some hardware- I glue my scarfs inside the house (in the basement) under the main beam of my first floor. I got a piece of I-beam that is 50" long, lay it on the joint, then put a bottle jack on top of it. I stand a 4x4 on top of the jack to the main beam. I'll slowly jack this up and move the house. hahaha. This applies a nice amount of even pressure on the joint.
Permalink Reply by lhedrick on January 19, 2010 at 3:36pm
Everyone is giving you good advice. I for one tried a few jigs for a circular saw. In my option I don't like making cuts like this with a circular saw. A little to dangerous in my view. As for the belt sander method it works but, what a mess. Since I have built a few boats and keep doing this next time I may build a router jig. For one boat I think your best bet is a hand plane as already suggested with a little practice on some scrap. As you cut it down you can use the exposed lines of the plywood core to tell you how you are doing.

As recommended don't start until you have sharpened the blade. Clamp securely to the work surface take your time and it will turn out fine. Epoxy bonds like crazy so if it's a little off it's not a problem. Epoxy up your practice piece then, brake it. You'll see.
Permalink Reply by Mike Baker on January 19, 2010 at 3:39pm
I forgot, there is always this method.http://www.youtube.com/watch?v=IcauPaEDlIw
And no that is not me.
Mike
http://www.bakerwooddriftboats.com
Permalink Reply by gs zoll on January 20, 2010 at 12:31pm
Thanks everyone for the great info, Dave I checked out your build on your blog and you built the same boat I have plans for. My materials list is about the same and I plan to have the same clear finish. Beautiful boat, I hope mine looks as good. I purchased Roger's book and plans already and his web sight lead me to Randy's sight and then to this one. Great network of people, valuable information and it's comforting to know that you can all say, been there done that. Randy I figured that the wavy joint was probably from a pro like you. I have a few ideas for a jig that I haven't seen anywhere yet and if it works I will let you all know. The method with a hand planer is a little less intimidating now and I am confident that I can manage it if I can't come up with something more precise (something that I can't screw up), it's that sharp thin edge that I worry about.
thanks again
GS Zoll
Permalink Reply by Dave Z on January 21, 2010 at 8:09am
Enjoy your project. You will find good advice here, so please stick around and post often, pictures always a plus!

good luck!
Permalink Reply by Terry Jones on January 24, 2010 at 7:03pm
Try this site I have used this jig and it worked well with a fine bladed skill saw. Works great on plywood up to 3/8", also worked well on 1/2" with a little ridge to clean up for a perfect fit.

http://www.oneoceankayaks.com/stitchglue/plyshophtm/scarfjig2.htm
Permalink Reply by Brad Dimock on February 13, 2010 at 7:10pm
Here's a set of six scarfs done all at once with a belt sander:
Attachments:
Permalink Reply by Brad Dimock on February 13, 2010 at 7:13pm
P.S. I mounted my shop-vac in the blast zone which kept the dust down. The more you do all at once with this system, the better they all come out.

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