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Re: Strip: Butt joint issues?
By:Bill Hamm
Date: 12/29/2010, 8:07 am
In Response To: Strip: Butt joint issues? (Darel)

: Hi all,

: After 3 months of work I'm finally laying my first strips on a Fire
: Star.

: I quite literally found it impossible to find full-length lumber.
: Local, internet, you name it. There was one possibility that
: would have doubled the cost of the project.

: So, I decided to scarf boards together as suggested in Rob's plans.
: Built the jig, and also built a clamp jig to hold them square
: and tight while drying. Did a couple boards at an 8:1 scarf.
: Glued them up with TB III and let them dry for a week.

: As soon as I picked them up they broke at the joints. All of them.
: The one that didn't break, when I ran it through the table sw
: each individual strip broke as it came off.

: After much searching, I figured butt joints would have to do. To my
: (admittedly faulted) logic, the end result is the same product.

: Sidebar: when I design and build things there are always
: compromises. As a matter of habit I generally try to turn my
: compromises into "design elements".

: One idea I had for a design element would involve lining up all of
: my butt joints in a line from shear down about 4". My
: (admittedly faulted) logic tells me this is not a good idea for
: structural reasons. A little voice also tells me that most of my
: strength comes from glass.

: Question #1: Will lining up these butt joints create a weak
: "seam" in the finished kayak? Like, will it break in
: half when I pick it up? Strap it to a car?

: I laid my sheer line to see what it looked like. I like it. What I
: did was cut several 2" pieces of strip and (permanently)
: glued them to the back of the butt joint. I can either sand
: these off or leave them in place and glass over them. Question
: #2: Thoughts? Leave in place? Sand off? Will they actually do
: anything to reinforce the joint? I rounded off the corners so
: they look like little pills and I think I could live with them
: in the finished boat if they do actually do anything.

: Like I said the line of butt joints will be from the sheer line
: about 4" down. There will be hardwood pinstripes running
: between the butt-jointed strips. No more than 3 butt joints will
: be lined up without a hardwood pinstripe between them. Does this
: help any?

: Anyone have any thoughts? Bill, I know you have no issues with butt
: joints. Rob, it's your kayak and I know you DO have a problem
: with butt joints. Anyone feel like chiming in? I don't want to
: do anything that will compromise the integirty of my kayak.

: Thank you,
: Darel

Hi Darel,

Staggered butt joints are one thing, lining them all up is something else entirely. Much like building a brick wall, if the joints are all lined up the wall is very weak, tends to crack at the lined up joints, if there is an overlap from one brick to the next the bricks share their strength, and the joints don't matter. Same thing with wood, if the butt joints are staggered, they have no effect on the overall strength of the boat. Lining them all up will create stress points that will eventually cause failure.

Bill H.

Messages In This Thread

Strip: Butt joint issues?
Darel -- 12/28/2010, 10:03 pm
joints of many kinds *PIC*
Paul G. Jacobson -- 1/2/2011, 12:02 pm
Re: Strip: Butt joint issues?
Fred Gasper -- 12/30/2010, 7:57 am
Re: Strip: Butt joint issues?
Paul G. Jacobson -- 12/30/2010, 11:54 am
Re: Strip: Butt joint issues?
G New -- 12/29/2010, 8:07 pm
Re: Strip: Butt joint issues?
Eric -- 12/29/2010, 7:14 pm
Re: Strip: Butt joint issues?
Rob Macks / Laughing Loon CC&K -- 12/29/2010, 2:16 pm
Re: Strip: Butt joint issues?
Dean -- 12/29/2010, 12:40 pm
Re: Strip: Butt joint issues?
Joy -- 12/29/2010, 9:43 am
Butt joints NOT over forms are bad
Paul G. Jacobson -- 12/29/2010, 1:43 pm
Re: Butt joints NOT over forms are bad
Al Edie -- 12/30/2010, 12:06 pm
Re: Butt joints NOT over forms are bad
Bill Hamm -- 12/30/2010, 1:48 pm
Re: Butt joints NOT over forms are bad
Bill Hamm -- 12/29/2010, 3:02 pm
Re: Strip: Butt joint issues?
Randy Echtinaw -- 12/29/2010, 10:56 am
Re: Strip: Butt joint issues? *PIC*
Joy -- 12/29/2010, 10:09 am
Re: Strip: Butt joint issues?
Bill Hamm -- 12/29/2010, 8:28 am
Butt joint boards or strips? *PIC*
Jay Babina -- 12/29/2010, 8:19 am
Re: Butt joint boards or strips?
Bill Hamm -- 12/29/2010, 8:30 am
Re: Strip: Butt joint issues?
Bill Hamm -- 12/29/2010, 8:07 am
Re: Strip: Butt joint issues?
Les Cheeseman -- 12/29/2010, 5:03 am
Re: Strip: Butt joint issues?
Randy Echtinaw -- 12/29/2010, 7:00 am
Re: Strip: Butt joint issues?
Darel -- 12/29/2010, 5:36 am
Still got that bottle of glue?
Paul G. Jacobson -- 12/31/2010, 7:22 am
Re: Still got that bottle of glue?
Darel -- 12/31/2010, 11:31 am
buy new glue
Paul G. Jacobson -- 12/29/2010, 4:27 am
Re: Strip: Butt joint issues?
Dave Houser -- 12/29/2010, 12:46 am
Re: Strip: Butt joint issues?
JohnK -- 12/29/2010, 2:23 am
Re: Strip: Butt joint issues?
Charlie -- 12/28/2010, 11:20 pm
Re: Strip: Butt joint issues?
Bill Hamm -- 12/29/2010, 8:16 am
Re: Strip: Butt joint issues?
Allan -- 12/28/2010, 10:36 pm
Re: Strip: Butt joint issues?
Stephen Troy -- 12/28/2010, 10:13 pm
Re: Strip: Butt joint issues? *NM* *PIC*
Darel -- 12/29/2010, 12:43 am
Re: Strip: Butt joint issues?
Bill Hamm -- 12/29/2010, 8:33 am
Re: Strip: Butt joint issues?
mark j -- 12/28/2010, 11:19 pm
Re: Strip: Butt joint issues?
Darel -- 12/28/2010, 10:22 pm