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Wendy Reymond
05-07-2003, 10:19 PM
What is a shiplap, as in the instruction, "shiplap and glue"? What sort of a join is it?
Wendy

Shalfleet
05-07-2003, 11:19 PM
I remember my Dad using the term refering to a type of fence with lapping planks. I found a couple of references but it still does seem at all clear to me!
1) Floor, Shiplap A floor consisting of shiplap boards, the term "shiplap" referring to the practice of alternately offsetting or rabbeting opposing edges of a board so that, when joined to others of its kind, adjacent boards "lap" one another.
2) SHIPLAP: wooden sheathing in which the boards are rabbeted so that the edge of each board laps over the edges of adjacent boards to make a flush joint (a rabbet is a channel, groove, or recess cut out of the edge or face of a surface, usually to enable one edge to receive another, as in paneling). On a Taylor Acoustic Bass or a Baby Taylor, the fingerboard brace interlocks and shiplaps onto the block.

Ken Liden
05-07-2003, 11:23 PM
WOW! Thats a term I have not heard for a very long time. If I recall correctly a piece of commercial shiplap was typically 1" x 6". The face at one edge was rabbeted to half thickness and about 1/2" wide. The mating piece was rabbeted on the opposite side. When joined the rabbets formed a simple overlap joint. I can't confirm its use in boats however.

Looks like Shalfleet and I remember the same product. I had forgotten that both edges are rabbeted.

[ 05-07-2003, 11:27 PM: Message edited by: Ken Liden ]

Wiley Baggins
05-08-2003, 12:13 AM
As described above and illustrated below.

_____
I..........I
I..........I
I.....__I
I.....I
I.....I
I__I

.......___
.......I......I
.......I......I
___I......I
I.............I
I.............I
I______I

Thad
05-08-2003, 06:55 AM
Everyonce in a while someone asks about "shiplap" and I generally say the funny thing is it isn't used on ships. Now that isn't quite true, but it is true in structural hull construction as far as I know. Is there any particular boat/ship use of shiplap lumber? or is it a flatland variation on a lap joint?

Bruce Taylor
05-08-2003, 07:41 AM
Thad, on lapstrake boats the gains are sometimes shiplapped.

TomRobb
05-08-2003, 11:02 AM
It's just opposing lengthwise rabbits. I've never heard it used anywhere but in reference to a style of house siding - like rabbited clapboard.

Geoffrey Harris
05-08-2003, 12:21 PM
It seems to me I have seen shiplap used in laid decks before

Thad
05-08-2003, 05:48 PM
Bruce, I know gain well but don't recommend a full square rabbet (shiplap) and in any case it would only appear to be shiplap looking at the hood end. That could have been the source of the name but I wonder.

Bruce Taylor
05-08-2003, 08:15 PM
I know gain well but don't recommend a full square rabbetThad, Walt Simmons doesn't like them either. From _Lapstrake Boatbuilding_ :

"As time goes on, I am less and less in favor of using ship laps. They make for good joints, but they have some weakness due to the right-angle rabbet that must be cut. They are also particularly nasty to fit in a tuck. If a ship lap could be made so that there was a rounded corner to the inside, it swould be considerably stronger..."

I wonder if the term "shiplap" might have entered the house carpenter's vocabulary by way of the analogy between lapstrake planking and clapboard siding. Early clapboard houses are sometimes referred to as "clinker-built" or "lapstreak" homes (esp. in older sources). The first ones would have used "plain bevel" planks, but these evolved into the familiar rabbeted "shiplap" board:

http://www.homestore.ca/tabs/homeimprovement/how_to/images/hsrep227fig3.gif

Just a thought.

[ 05-08-2003, 08:20 PM: Message edited by: Bruce Taylor ]

Thad
05-09-2003, 06:42 AM
Bruce, That's kind of what I think, BUT: I have been working on a Coast Guard Motor Surf Boat, 25' 10", lapstrake cypress; the garboard/broad and the lower topside planks are actually done 1" shiplap so they look like 1/2 inch laps on the outside but they lie flush on the inside, where the watertight deck was run, the bottom made heavy for strength.

Paul Scheuer
05-10-2003, 10:52 PM
It seems like the seams would be guaranteed to hold water. Maybe the skiff/planters' fate was sealed by the design. Makes more sense for house siding where the water only comes from above and the walls are vertical.

J Sanford
05-11-2003, 12:04 AM
I have a 1958 Lightning that was built using shiplap method. The seams were sealed with a rubber like compound. I plan to remove and replace with BoatLIFE Life-Caulk.