1/8" thick strips too thin for strip-built boat?

Hi all,

Geting back into building kayaks after quite a break.  Kicking off with a CLC double, but then keen to do my first strip one.

WRC is expensive here in Australia, but I managed to pick up a whole lot from another buider who ripped strips from cedar blind offcuts.  He built a rowing shell from them.

I was hoping to use them for a kayak, but they're 1/8" thick vs the more common 1/4" strips I see Nick and others use.

Would this be too thin for a kayak, assuming it was for light bay/lake use and well glassed?  I'd need ot be careful with sanding, but would there be any other issues using thin strips?


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RE: 1/8" thick strips too thin for strip-built boat?

From a purely strength perspective, additional layers of glass and possibly carbon fiber will fix any deficiency caused by thinner wood. With the correct lamination schedule that boat could easily be stronger than the standard 1/4" boats.

What I see as issues are handling during construction, construction itself (like the sanding that you mention) and defining the lamination schedule so that it stays light and affordable. None of these are show-stoppers, just something to pay attention to that may not be called out in the instructions for the standard boats.



RE: 1/8" thick strips too thin for strip-built boat?

Hi  DJR1971,

i have a lot of strip build experience and i agree with lazlo's comments. i thought i could add some more color that might be useful.

one of the key things you are looking for in a strip build is the 'stiffness' of the laminate.    that is, its resistence to bending.  its important becuase this is the type of strength that holds the hull in its shape. 

the easiest way to make a light and stiff laminate is a wide core with thin fibre (fibreglass, carbon, kevlar, etc) layer bonded to each side with a little epoxy.   now most of the weight of this composite is in the epoxy and glass....so when you analyze the physic of this, you have to add a lot more epoxy/glass sheathing to to get a 1/8 strip as stiff as a 1/4 strip with a given epoxy/glass sheath.   As Lazlo pointed out,  the 1/8 strip construction can add a lot of weight if you need the same stiffness as anticipated  in the 1/4 inch build.

the other point i would make is that you can acheive stiffness through other means than the layup....rounded hulls that don't have flats sections can be very stiff as result of their shape and can be built with thinner strips than a design that has a lot of flats.   just think of a paper tube and how it is stiff vs the unrolled piece of paper.

anyway, to make a long story short, i have had good success building light stiff kayaks with thin strips as little as 1/8.....but i have been most successful with this when the hulls had curves and very few flat sections (e.g., tube shaped).  i did once build a boat with thin stips that had some big flats and had to add a lot of glass/epoxy to stiffen up the hull.  the other thing i would say is strip built boats, if they are kept light, can certainly be strong and reliable but i would not typically describe them as 'strong' in terms of being able to take big impact or poiint load (e.g., bashing into rocks or certain kinds of kayak rescues) without a lot of glass and weight needing to be added.

so as pointed out by you, crew boats are strong enough to do what they do....but if you drop them, you tend to break them pretty easily.



RE: 1/8" thick strips too thin for strip-built boat?

I'll jump into this thread with the suggestion that you look into what's called 'cold-molding' technique if you have enough of the 1/8" WRC strippage on hand to contemplate fabricating a double-thickness of 1/8" strips to yield a cross-planked 1/4" thick hull wall that then get's 'glassed on both sides.

Cold-molding basically is making your hull out of strips/veneers glued together that then form custom 'plywood' shaped over the hull form.

WRC is fragile enough at 1/4" thickness... how wide are your strips?

Wider generally means less able to conform to contours so narrower – in this case maybe 3/4" or 5/8" for a kayak would be appropriate – but with 1/8" thick strips you can get away with a bit more bending because the strips aren't nearly as stiff as their thicker bretheren.

For a kayak the results may be worth the extra effort involved for the thickness that then provides stiffness once the hull's 'glass & epoxy skins have been added. You may find that a bare, cold-molded hull shell can get along with less 'glass & epoxy than a single layer of 1/4" strips would have required, potentially saving some weight!

Some links for study:




RE: 1/8" thick strips too thin for strip-built boat?

A kayak is the wrong shape for cross-plank cold molding with 1/8" WRC strips.

RE: 1/8" thick strips too thin for strip-built boat?

ALL kayaks?   

Or just some of a more radical style where compound curves change fast?

Doesn't have to be acute angle either between the two layers. I was thinking maybe 30 degrees max. but it was just a suggestion if the OP had enough strips to double-wall a hull.

RE: 1/8" thick strips too thin for strip-built boat?

DJR1971, Laszlo knows what he's about, rest assured.

Still I'm intrigued by the possibilities those 1/8" thick strips might hold for a project.

Do you have a kayak design in mind for this endeavor?

(I've been out in a SOF kayak exactly once in my lifetime. That afternoon's adventure convinced me that SOF had limitations when the return lake crossing had me checking the duck-taped errant branch puncture repair frequently as we got closer to shore.... That afternoon was my only kayak experience... at least in this lifetime, so far.)


RE: 1/8" thick strips too thin for strip-built boat?

Asked some other experienced folks about this, got back some interesting comments.

Obviously cold-molding would be a tedious endeavor if it's even possible for the design you've chosen DJR. Requires a mold or form over which the laminating process takes place so there's time & money spent in building that, to be used just one time.

3/16" is a generally accepted minimum strip thickness for strip building but as h has related it can be done with a suitable design and you're willing to undertake the challenge.

One suggested approach for using 1/8" strips already on hand would have you gluing two strips together face to face so that the net effect would have you building your hull out of 1/4" thick strips. There's some fussiness in this approach in that the strips, if not already uniformly wide, would need some additional trimming to get to a consistent width. This could be done if you'd plan on adding a cove and bead detail to their edges, something virtually impossible to effect on 1/8" strips. Great care would have to be taken during the gluing operations to ensure the strips are as straight along an edge and that they'd be held in close contact during the glue cure time. Gluing two strips together face to face would make the thicker strips somewhat more uniform than strips cut to 1/4" from stock and may also be less resistant to splitting while assembly is being done.

RE: 1/8" thick strips too thin for strip-built boat?

   I used 1/8" strips accidently on my first Petrel. I had gotten strips from someone who had milled them poorly and by the time I got the boat sanded fair it was 1/8" thick. Can you say Frah Gee Lay? I ended up using 6oz glass on the hull the strengthen it. The boat end up being 33lbs and really fun. Not fragile at all.

Nick Schade frequently uses 1/8" strips. He cuts extra forms and uses 10" spacing to minimize the flex while sanding.


RE: 1/8" thick strips too thin for strip-built boat?

Thanks all for the replies and inputs.  It occured to me after I posted that i could just glue two strips together to get a 1/4" thick strip!  So that may be an option, I have quite a few strips.

I'll have another look at Nick's build video's on using thin strips too.  And I might go something hybrid, one of the designs with a strip deck where I could get away with the thinner strips and add some cross-bracing or hollow frames to reduce flex.

Lots to think about, I'll crack on with my CLC double for now and look further into what I could make with the strips I have, working with doubling, better bracing, or thicker glass.

Thanks again!  Great to see this forum still active and experst like Laszlo still around.


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