Scarfing wood

D

Drew Arnold

New member
I'm was not able to find the lengths of wood to use as the gunnels and keel on my Kara build. So instead I purchased 1x6x8's and used a homemade scarfing jig I found on the gatorboats forum website. I have everything cut and ready to glue. My question is what would work best to attach these pieces of wood together. I've read that on plywood scarfing it's better to use epoxy or a fillet mixture to connect the wood but I've also read where folks have used just glue such as 5200 or plain wateroproof wood glue to attach lengths of boards. What would work best for this application?
 
Drew...that's my scarfing photo tutorial on the gator boats site. Just use epoxy thickened with fumed silica (cabosil). Don't overclamp them.

Brad
 
I built my kara this past summer. I had been reading how many folks were having problems with the gunnels cracking when bent. I tried something different. I used 1/4 plywood, three layers, glued them together and formed them in place. It was very simple to do, and with so many layers, was plenty strong. Just my .02 for a different approach!
 
Drew,
5200 will seal the joint if the Scarf is supported and not in a lot of tension when the boat is built. A backing block used on a plank scarf comes to mind. The screws hold the plank ends to the block and the 5200 keeps the water out.

For a chine or strake like you are building a more Glue like product is likely better ie. the epoxy. The thickener will help to take up any space that is left when the scarf joint is made. Most long scarf's (10 to 1) have a huge glue area so the glue itself is under very low loading per square inch. Outdoor yellow glue would work in a good joint, and the old builders used resorcinol.

But epoxy works well and most guys have it for the build anyway.

Did you look at the lumber yard for spruce or fir "Strapping"

They sell it for hanging drywall in new homes and it comes in 16' bundles, cheap.(3\4" x 1 1\2") There is us. also "Ledger board" in the same species. These are rough sawn and 6 to 8 inches wide. You pick the good ones and saw out what you need with a skill saw.
 
Ed, Great idea, I have done that many times and it turns out scary strong. One wrinkle I learned is to use a heat gun and heat the plywood as you bend it to shape and it turns to rubber. Clamp it down and laminate another layer on!!
 
Thanks for the heat gun suggestion Tom. I just met a guy while hunting using a scull boat. Now that I have the boat building bug, I think I'm just gonna hafta build me one of those too, and I'll implement your suggestion!
 
Tom
Did you have to wet the wood first before you put the heat gun on it like steaming or did you heat the wood from being dry.
Take care and God Bless
Eddie and Amber
Its all about Building that Bond.
 
Eddie,
Just dry. Now I am only talking about 3 or 4" strips for the coaming but it just softens the glue I think and lets the plies slip. Just a guess but it sure works!! You can see some pics on the spec page here of my Armstrong Broadbill build. If there is more interest I can probably dig out some old pics and try to get some posted here. Picture resizing is still a problem for me. I will have a few weeeks to play with that over Christmas, this is my last wek of class this semester.
Oh yeah, you will break some strips learning to do this!!!
 
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Drew the 5200 would work, but I think it would take forever to cure. I'd use West thickened with cabosil. Make it itno a nice paste and your good to go
 
Tom
I have done a search and tried to get a link on your thread but I did,nt have any luck, could you post a link for me mate. Thanks.
Take care and God Bless
Eddie and Amber
Its all about Building that Bond.
 
Re: the Epoxy. Cabosil is a thixotropic. It adds no strength to the equation. The biggest worry doing the scarf is that the joint will become resin starved from wicking into the wood fibers. I'd recommend that you also throw in some West system microfibers. Those will help to keep the joint moist during cure out and it will add a little strength. Also prewetting the joint with unthickened resin is a good idea.
 
Eddie, Just go to the main index here then "duck boat specs", "sneak boats", "Arthur Armstrong Broadbill" and you will see a few pictures of my build. Good Luck
 
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