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Re: Weak Scarf Joints
By:Jack Martin
Date: 3/24/1999, 9:24 am
In Response To: Weak Scarf Joints (Dan Gunn)

> Not minutes after someone posted a question about my using 3M bubbles as a
> thickener in my scarf joints, and the possible ramifacations to strength,
> did one break.

This might read across into the "CLC instructions" thread, Dan, but I'll put my "newbie" observation here.

My CLC North Bay manual and the basic CLC manual included in the kit --- along with CLC's "The Kayak Shop" book, tells the builder to bond scarf joints with "thickened epoxy" --- thickened to the consistency of "jam". In another section of the basic manual, CLC tells the builder to use silica powder (Cab-o-Sil) as the thickening agent for bonding, and to use microbaloons and wood flour for fairing and other filling applications. I really thought that one of the other reference works recommended first coating the joints to be scarfed with unthickened epoxy to fill the end grain and to ensure that the thickened epoxy to be used for joining was not drawn into the ends, making a weakened joint, but I can't find that information in any CLC material after taking more than a few minutes to look through the instructional material provided with the kit, in the book, or on the web site in the "Shop Notes". That's a technique my (adult) son, a builder with some experience in using epoxy, and I used when we joined the scarf joints on the North Bay --- with apparent success so far, by the way.

Could the more accomplished builders among us comment on this point, please? The idea of first working unthickened epoxy into the scarf joints to fill the end grain, and then immediately coating the joint with silica-thickened epoxy to provide the bonding joint? It might help a lot of folks further back in the assembly chain.

Sidebar: a brother of a friend, in the process of building a CLC boat, asked me for advice --- the blind leading the deaf? --- when his scarf joints failed; but, in his case, he had used unthickened epoxy only in joining his scarfs. Chris helped him with the solution, and suggested he re-read the manual. My point is that I agree with you, Dan, that there are some occasional apparent inconsistencies occasionally in the CLC literature --- speedbumps on your "journey" in the other thread --- but that, overall, at least in the case of the North Bay literature, there is a pattern of using the NB manual for specifics and the general manual for general issues which I find adequate so far. The departure to that acceptance may be in this very important issue of properly joining scarf joints, and, maybe soon, Chris will weigh in with some thoughts and observations. [Nod, nod, wink, wink.]

Jack Martin

Messages In This Thread

Weak Scarf Joints
Dan Gunn -- 3/23/1999, 3:33 pm
Re: Weak Scarf Joints
Stan Heeres -- 3/24/1999, 9:01 pm
Re: Weak Scarf Joints
Shawn Baker -- 3/24/1999, 12:12 pm
Re: Weak Scarf Joints
Brian Barnett -- 3/24/1999, 10:40 am
Sounds like a new take on a "folding" ka
Pete Rudie -- 3/24/1999, 12:26 pm
Re: Weak Scarf Joints
Shawn Baker -- 3/24/1999, 12:13 pm
Re: Weak Scarf Joints
Byron Lawrence -- 3/24/1999, 10:38 am
Re: Weak Scarf Joints
Jack Martin -- 3/24/1999, 9:24 am
Re: Weak Scarf Joints
Shawn Baker -- 3/24/1999, 12:03 pm
Re: Weak Scarf Joints
Don Herring -- 3/23/1999, 8:49 pm
Re: Instructions & Weak Scarf Joints
Dan V -- 3/23/1999, 5:30 pm
Re: Instructions & Weak Scarf Joints
Larry C. -- 3/23/1999, 6:50 pm
Re: Instructions & Weak Scarf Joints
Pete Rudie -- 3/24/1999, 12:35 am
Re: Weak Scarf Joints
Kenneth Paul -- 3/23/1999, 5:08 pm
Re: Weak Scarf Joints
Mark Roberts -- 3/23/1999, 4:40 pm
Re: Weak Scarf Joints
Pete Rudie -- 3/24/1999, 12:42 am
Re: Weak Scarf Joints
Dan Gunn -- 3/23/1999, 4:50 pm