Boat Building Forum

Find advice on all aspects of building your own kayak, canoe or any lightweight boats

Re: Weak Scarf Joints
By:Shawn Baker
Date: 3/24/1999, 12:03 pm
In Response To: Re: Weak Scarf Joints (Jack Martin)

> 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.

You're right, Jack. This is the method recommended by Raka in their epoxy manual. I can't remember what type of epoxy CLC sends with their kits, but I'm sure you'll find the information in the epoxy manual.

> 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.

I let my joints sit 5-10 minutes so that the end-grain can really soak up the epoxy. If you slap it right on and then put on the thickened stuff, not much will have soaked into the joints and when you clamp it, most everything will squeeze out. If you let it soak a bit first and then put on the thickened goop, only the excess thickened epoxy will squeeze out.

> 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