View Full Version : sof kayak project

09-06-2008, 11:49 AM
Well, the frame is wood. But it has plywood in it. I don't know if the purists will approve, but I promised the fine fellow who supplied the plans...


The plywood is the cutout from a sink installation in a new counter. It's thicker than it absolutely has to be, but this boat will be in the freight hauling category and percentage-wise it isn't too heavy. It's what I had.


Here are Frame A and Frame B. The boat is absolutely symetrical, something I will be altering a little in the setup. The plywood is two thicknesses screwed together, so I have four frames started:


The circular saw is handy for getting fairly straight cuts where they're wanted. I'll separate the panels after I cut the frames for the sheer stringer and finish the cutouts after the the rest of the setup is built.

I got some fairly clear western red cedar that I'll rip to the the two sheer stringers. Their twelve foot length bent around the frames to the stems will determine the overall length of k1.

Oh, the square bilge? That will get modified after the keel stringer, which I will get out of VG Douglas Fir, and the rest of the parts are temporarily lashed together. I will still have a hard turn of bilge around the center of buoyancy, with fine ends. The bilge stringers will be the fiddley part, trying to get the volumes distributed where I want them. Very empirical. And a lot of fun. Before I get that far I will make templates of the frames as you see them, and templates of the frames after fairing and fitting. k2 will get all the empirical benefits of k1. k0 is the original kayak I built a Long Time Ago and am replacing now:


More to follow...,


Pernicious Atavist
09-06-2008, 11:55 AM
The 'purists' live way up north and use driftwood, ivory, bone and walrus hide to build their kayaks, so, no, they wouldn't approve, if they even cared....

For the rest of us...time will tell.....

09-06-2008, 12:05 PM
The 'purists' live way up north and use driftwood, ivory, bone and walrus hide to build their kayaks, so, no, they wouldn't approve, if they even cared....

For the rest of us...time will tell.....

Yup, those purists who use 4-wheelers to haul the catch, and rifles to kill it, and heat their homes with stove oil and light them with electricity and fly their fish out to market on airplanes, which they catch in aluminum boats powered by outboard engines, and for all I know buy their kayaks from Gander Mountain.

Methinks it's been a while since you've been "way up north". ;)


Paul Scheuer
09-06-2008, 02:18 PM
What's your plan for the skin ?

Also, what's the "freight" agenda ?

I picked up a "free" rigid 15 ft. Folbot Sporty kit a few years ago that had two layers of "leatherette" on the bottom, with carpet glue between, and one layer of lighter material on the deck. It turned out a little on the heavy side, but bullet proof.

Keep us informed.

Pernicious Atavist
09-06-2008, 02:29 PM
I think that's my point, most of the purists have long since left us....

09-06-2008, 03:59 PM
Paul, I'm planning to get some light dacron like Dyson sells, and use 2-part polyurethane to dope it.

Freight was a little tongue-in-cheek, but I think I saw such a category on the CLC site referring to some of their designs. This means it'll be more like a duck than a baidarka, more of a weight carrier than a sprinter. Here's their 12 footer with the freight rating :


or the similar Pungo:


There's a good video showing the clc duck's speed and tracking agility.

09-06-2008, 05:28 PM
Here's another source for heat shrink dacron.
Order Form & Price List - Geodesic AiroLITE Boats (http://www.gaboats.com/order/)
Use epoxy glue and double sided tape along gunnels and stems then shrink with household clothes iron. Finish with varnish or paint to seal the fabric.

Cuyahoga Chuck
09-06-2008, 05:43 PM
There were a lot of kayak designs for plywood and lumber SOF construction at one time .
A Brit, Percy Blandford, developed a style of kayak construction featuring 3/8" plywood bulkheads for the British Sea Scouts. He used this in designing about a dozen different versions that covered every possible combination of long, short, narrow,wide, one hole, two hole, open cockpit. You can still get his plans from Clark Craft in Buffalo.
Blandford's designs aren't very popular any more but they are well thought out, lightweight and fairly cheap to build.
There are also plans for some old SOF designs on this web site.

I hope you aren't going very far. A kayak with a waterline less than 12 feet isn't going to be a treat to paddle. Short boats like that are all the rage but all their benefits are on land. An the water an old lady in a 15 footer will keep up with you using half as many strokes.

09-06-2008, 06:09 PM
Hi Chuck,

Thanks for the links. I actually used k0 in the Alaska bush for a number of years. I hauled water 15 gallons at a time when the wind prevented the bank dory from proceeding. I shot and hauled deer with it. I traveled around the Inian Islands in the mouth of Cross Sound three days in succession with no problem, scouting and looking for deer. That includes passages thru The Laundry, North Inian Pass, and South Inian Pass.

I also hunted from it while anchored in a hidey hole near White Sulpher Hot Springs on the outside coast of Chichagof Island, waiting for weather so I could get back in the ocean again.

It was stable enough that I never got a rail under, and burdensome enough that I could carry an adult passenger from the boat to the beach with no worries.

I never raced another kayak, but back in the day the ONLY OTHER kayak I saw in Southeast was Dyson's, who was paddling between a cove and Grave's Harbor, going through the rock piles and past the light house at Cape Spencer. The lighthouse was manned by Coasties at the time.

I'm pretty sure that anyone racing past me won't have ninety pounds of water on board or a hundred twenty five pound deer.

If I didn't have actual prior experience I wouldn't be so stinking enthusiastic about building some more of them, but I'm loving it Chuck.



09-06-2008, 06:11 PM

Thank you for the source link. Duly noted and bookmarked.


09-07-2008, 06:41 PM

Initial mockup.
I ripped the sheer stringer from red cedar with a japanese style pull saw. It can follow the grain even though you keep the kerf running exactly on the line. Not a problem tho.

I added two inches to the height of the sheer in the drawings. I like volume. Still less heighth to the deck stringer than the Hooper Bay boats.

Next I will cut the stem and stern posts, if they can be called that, and make a keel strinjger to tie the bits together. Then I can start getting serious about the frame placement, getting the center of buoyance where I want it.

I think the frame shown in the drawing closest to the ends is not necessary, unless I can't get the volume disposed the way I want it in that area.

Hope all the projects are progressing,


09-15-2008, 08:27 PM
Here's an update on the skin on frame frame:


I altered the cockpit length from the plans by making another frame and bringing the deck stringer aft. It will still be a big cockpit, but not as big as last time.

I'm thinking of putting a lightening hole in the stem and sternposts. Whatd'ya think?

I have a surplus center frame now and next I'll start chipping away at the bilge corners to get the spot for the chine stringer worked out. After that I'll remove frames and make templates for the chine stringer fore and aft. I'm moving the center of buoyancy aft some, sort of swedeform, and keeping the bottom wide where I sit. When I do the final assembly I'll peg the joints with dowels and be more careful with the lashings.

I talked to George Dyson today and he's sending me some cloth for the skin. The old way of covering this frame with canvas was to cover the hull first, and cover the deck afterwards, overlapping the seams on the sheer stringer. Nowadays I mostly see one single seam on the deck centerline. Any opinions about this item?

Thanks for looking,


Mike Field
09-16-2008, 02:06 AM
The Percy Blandford kayak I built nearly fifty years ago looked quite like your K0, but with a raised and flared cockpit coaming. It had a somewhat similar structure to your K1, and, of course, a canvas skin. And as you've said, the canvas was in two full-length pieces, overlapped at the gunwales.

The obvious reason for this method was that as the deck canvas was lighter than the hull canvas (12 oz vs 15 oz from memory, but memory's not completely reliable after all this time,) that was really the only place to make the join. If the vessel were to be covered with the same material throughout, as it sounds yours is to be, that would not provide any particular benefit of itself.

But the second reason in my case might still be appropriate in yours. This was that, once the skin was all on (and in my case painted,) the gunwale join between the hull and deck pieces was completely covered with a " half-round timber rubbing-strake, and the rubbing-strake both protects the join and also makes it invisible.

I think it was a good design feature, and I'd use it again for that reason if for no other.


09-16-2008, 08:05 AM
Nice kayak Mike. My building plans are very similar. I didn't install the coaming, needed the boat for transportation, and I never missed it. I think there must have been thousands of kayaks built just like ours. They are incredibly good boats.

I think those old designs had lots of stringers because cotton sail canvas wasn't nearly as strong as the aircraft fabric we have available now. I'm leaving most of the stringers out and using heavier ones where they're necessary. Seems to work on the modern boats like the Cape Falcon Kayaks F1.


I haven't decided on the cockpit. Either an enlarged version of the F1, or a similar one to yours.

Are you motivated to build your kayak again? I hope you do, it's still just as rewarding as ever.


Mike Field
09-16-2008, 08:14 PM
I suppose I added the coaming mainly because it was part of the design, and to omit it was to not finish the boat. But I do think it looks better for it, and I found it had good practical value too -- firstly it kept a lot of water out of the boat when there was any slop over the deck, and second it provided a sound footing for a spray-cover when I used one (which was usually when getting out through the surf zone into the ocean.)


Kareela was built as a fun vessel, not a working vessel like K0, of course.

This is design PBK27, 13' overall, and I have the sister-plans for PBK18, a 17' double-cockpit to the same design-philosophy -- a stable, burdensome, cruising vessel. But I doubt I'll ever build that one now. Kareela still takes me where I want her.

There are some good photos and a narrative about a PBK27 under construction here (http://people.brunel.ac.uk/~acsrrrm/kayak/pbk/pbk27/pbk_27.html), the builder using Ceconite 101 as the skin material. He's kept the same framing as the original design though, which uses three intermediate stringers between gunwale and hog. The frames are cut so there's a concave curve between each stringer, meaning the skin doesn't bear against the frames anywhere, allowing the stringers to keep it fair,as shown here --


The end-posts and all frames are cut from 3/8" marine ply, the gunwales and hog are 1" x ", and the stringers and cockpit framing are " x " (all the non-ply being straight-grained softwood, in my case parana pine. If I could find the photos I took of Kareela under construction with my trusty old Brownie Box, they'd look pretty-well identical to the ones on this site.

Plans for at least some Percy Blandford designs are still available through Clark Craft (http://www.clarkcraft.com/cgi-local/shop.pl?cart_id=e3f55a3731d1428355641a9db6f22026&type=categ&categ=014) in New York. Look for the ones whose catalogue numbers start with "BK" as they seem to be the Blandford designs.

Good boats.


09-28-2008, 11:38 PM
Mike, thanks for the details. Your craftsmanship is way better than mine. An inspiration. Here's some process photos with some details. I am basically using the midsection of the plans I started with to build upon, a little like the norse setup, and finding the other frame spaces by eye, using the stringers to get fair curves.


Here's the 'jig' to get the stern post plumb.


The dowels are glued to the outer piece only
so they won't back out into the skin. The two
pieces are free to disassemble. Same with all
these joints.


Here's the setup to introduce sheer into the
sheer stringer by ripping and laminating the
cedar. The effect when the connection
is made is to put tension on the post
and induce rocker into the keel stringer.


This shows the bow detail pegged and lashed.
The glue line is visible. It extends to within six
inches of the plywood frame.


Detail of the stringer to frame lashing.


Lashed up and waiting for the chine stringers
to be scarfed. They will be in two pieces, and
the ends of those pieces may want to be split
as well. A four-way lamination. Unless I decide
to truck over to the lumber yard to see if they have
long enough material to save the scarfing time.

After the chine stringers are lashed in I can derive
the two remaining frame shapes. Just got a planer
which makes getting out bits and pieces
ridiculously easy.

Three Cedars
09-29-2008, 12:53 AM
Griz - Good project, that is an honest working man's kayak made to work .

My experience is building several of the lighter weight kayaks using steam bent ribs with a single piece of fabric sewn up the center of the deck. SOF kayak construction doesn't have hard and fast rules , pretty adaptable .

You can use one piece of fabric but it will have to be pretty wide which I think Dyson can supply. Two pieces is probably easier to get smooth the first time around and little to no sewing needed.

Mike Field's info is solid , Percy Blandford designs are good safe boats . Tom Yost has an incredible website that includes plywood form construction
www.yostwerks.com His Sea Tour double is sweet http://yostwerks.com/SeaTourEXPDouble_2.html

The ultra-light aircraft 3-4 oz dacron is too light for all but dainty use. Go with 10 - 16 oz nylon or polyester fabric , in a heavy boat like yours you want a tough skin for beaching . Put in a floor of thin plywood or stringers and tarp to keep the grit out. If at all possible don't drag the boat , carry it or use pool noodles to protect the bottom. Water in jugs for ballast if needed, buck deer on the trip home.

09-30-2008, 06:27 AM
Looking good Grizz.

10-01-2008, 08:54 AM
Thanks Guys

Next update:


I chose the get clear cedar route. It's buttery soft. I made a fence
from a piece of oak trim that I thinned to a quarter inch. This gave
me good fits on the stringers with barely any adjustment needed.
The oak guides the saw and the blade takes the softer wood. Nice.


Here's the beginning of fitting the frame. You can see that the
chine stringer canted in the center frames so I went with the
wisdom of the wood. Not something I've seen done, but it's
done now.


Here's the frame joggled into position. I beveled the cut to get
better frame support at this station. The dowel is installed but
the frame tie holes and lashings are on the list. Next is the matching
frame at the other extreme, getting the 'deck' supports attached
and then lots of fiddly work getting all the bearing surfaces smooth
and round. Then disassemble, finish the wood with sealer,
reassemble, and put her skirt on.


Here's the original mockup lashup. She's phat in the center and
fine on the ends. A little resemblence to the CLC 12 footer. It's
an open question if she can carve turns, but she has rocker and
may agree to it. The original was dead straight along the keel
and perfectly symetrical, and didn't carve so well, she paddled
more like a canoe. It's going to be fun finding out, and she'll be
wet just in time to work on the salmon run that's about to pass
by the house.



12-18-2008, 12:12 AM
Here's the current state of the frame:


There are only a couple of pieces of wood in this frame that were in the previous early pictures.


This is a complete redesign from the prototype, including relocating the cockpit area and building it differently, replacing the keelson and end posts, making this frame a foot shorter, and making new frames to fit. So far I'm pleased with how it's looking and don't plan any big changes to this one.

Still have to do the floorboards, then install the deck ridges, then install the cockpit coaming which I decided to do the lamination style, so I'll rip a thin piece of cedar and wind it around a form and glue the layers to make a type of I-beam. After that the cloth, the finish, and the splash-in. Getting excited. Might be done by break-up if I keep at it. Heh.

Hope everyone who wants one has a Merry Christmas.

12-18-2008, 07:18 AM
Good thread thanks.