Building the Sawfish 12 – Part Two

by Jim Brown - Sweetwater, Tennessee - USA

A Foam Kayak Designed by Rowerwet (Josh Withe)

Builder: Jim Brown – Sweetwater, TN

Part OnePart Two

Part Two – Covering and Finishing

There is nearly a month gap since Part 1 was written. Even though I have been working steadily almost every available day since then, the canvas covering and resulting needful fairing of overlaps with the DAP lightweight spackle, plus myriad other details such as making a mount for the seat, has been very much more time-consuming than I expected.

I had selected a heavier covering fabric than Rowerwet usually recommends, using a cotton duck canvas from Jo-Ann’s Fabric ($9.90/yard 61″ wide, but because my wife had a 50%-off coupon, $4.95/yard). I bought two 4-1/2 yard pieces, which weighed in at 9 pounds for 9 yards, or 16 oz/yard, as compared to the 10 oz/yard polyester fabric used on the Chuckanut 12. Total cost was about $45.

Fitting non-flexible canvas over so many compound curves has required doing the boat in many pieces, with many slits in the fabric to accommodate the curves. I found that using Carole’s pinking shears greatly reduced the number of extraneous strings coming off the fabric edges. However, the pinking shears introduced a new problem: when the pinked edges were saturated with glue and dried, the edges raised up, creating sawtooth like edges which had to be sanded off and the edge seams filled with spackling compound, then resanded to produce a smooth paintable edge.

In the course of this work, I read Rowerwet’s reference to The Battleyak, a heavily modified fishing version of the Sawfish (with electric motor, battery, lights, bait well, rod holders etc.), and looked up the building video on Facebook, which showed the builder covering some odd-shaped large bottom strakes with some denim cloth from an old pair of jeans. Eureka! A revelation! If there is a next Sawfish, it will be covered with Stretch Denim, which will conform much more easily to the compound curves which have consumed so much of my time for the past month. That fabric is also available at Jo-Ann Fabric for $12.99/yard, but with Carole’s 50%-off coupons that would be little more expensive than the cotton duck I am now using.

Since I am installing a GCI SitBacker seat similar to that I used in the Chuckanut 12, I needed a means to mount that seat in a foam floorboard. This required building a seat bracket that will accommodate the under-seat straps of that stadium seat, and a means of screwing that assembly to the foam, so I drilled 1/2″ holes in the foam bottom, filled the holes partly with PL Premium, and inserted 1-1/2″ lengths of 1/2″ dowel I had on hand. After the excess PL was trimmed off, the dowels were drilled to line up with the previously drilled holes in the seat mount. This installation is strong enough that the entire boat can be lifted up by the seat mount!

Rowerwet, after testing the original Sawfish, suggested that all such boats be fitted with a keel strake to prevent the boat from being blown sideways in a stiff breeze, and to aid tracking while paddling. I had enough foam scraps left to piece together a 3″ high by 2″ wide keel, which was glued in place with PL Premium. The top edges were rounded off with the 60 grit sander, and the keel covered with the cotton duck canvas.

Even before covering the keel with the cotton duck, the entire boat could be lifted by the foam keel with no problem. Of course all that Titebond II wood glue will require more sanding, filling and sanding. Actually, it is not the work of doing these things which consumes so much time, but it is the waiting for the glue and spackling to set up sufficiently to be sanded. I must confess that most of this work is of my own making. I am not a perfectionist, but I don’t want my boats to look “too homemade”.

In the process of all this, I got so carried away with the prospect of a denim-covered kayak, that I decided to change the planned color of the kayak from Rustoleum Safety Yellow gloss enamel, to a grayed-blue latex satin house paint (HGTV-Sherwin Williams Sea Creature HGSW3342, in Assure Satin Base, $22.98/gallon at Lowes). I had to try it out in a small spot on the hull. Perfect! Looks just like denim on this canvas.

After some more filling and sanding of canvas joints and overlaps, painting was started, using a 4″ roller, and a foam brush for the corners. For the first coat I used a fuzzy roller intended for rough surfaces, but it left too many little fuzzies in the paint, so I switched to a foam roller intended for smooth surfaces. Three coats used 3/4 of the gallon of exterior house paint. Each coat looked better, and a fourth coat might have improved it still more, but I decided to save one quart in a jar for future touchups or modifications, and to minimize weight.

At this point a weigh-in was appropriate:

Bare foam boat shaped, but no additions……………………..17 #

With canvas, glue, spackle and 3 coats latex paint………..27 #

With seats, seat mount, hatch and straps (no cooler)……..33 #

So the boat ended up 10# lighter than my wife’s previous Wilderness Systems Pungo 120 (43# manufacturer claimed weight), and 6# lighter than my previously built Chuckanut 12. All three boats were nominally the same length and width (12′ x 28″). I could undoubtedly have saved some weight by using a lighter covering fabric, and a lighter seat/mount assembly, and being less persnickety with the filling, sanding and painting. My modifications to the as-designed boat by adding a fourth layer of 2″ foam added weight as well. I would guess it could be 27#-28# easily.

Cost of the boat, including 9% TN sales tax ended up being about half of what the aforementioned Chuckanut 12 cost to build:

Two 4×8 Sheets of 2″ Formular Pink Foam:…………………$63.22

One Gallon Titebond II Wood Glue…………………………….$19.59

18 OZ Gorilla Glue……………………………………………………$20.23

9 Yards Cotton Duck Canvas………………………………………$49.23

1 GCI Sitbacker Stadium Seat…………………………………….$27.00

1 Quart DAP Patch & Spackle…………………………………….$7.06

1 Gallon Blue Satin Latex House Paint……………………….. $25.05

1 Tube PL Premium 3x Adhesive…………………………………$5.09

1 Gamma 2 Paint Pail Lid……………………………………………$7.94

10 Blue Nitrile Gloves………………………………………………..$2.81

Bamboo Skewers/ PVC pipe/ Misc Screws…………………...$3.00

Total $230.22

Obviously, the cost could have been reduced by using a less expensive seat, fabric covering, and paint. Also, I used some scrap wood from my wood pile. Mostly it was 1/4″ exterior plywood left over from previous projects, so a prospective builder might need to add $15 or so to the total. So here she is ready to splash:

All the various straps were attached to the foam hull by either drilling holes through the fabric and filling with PL Premium and inserting folded straps (carry handles), or by drilling holes and inserting PL Premium and wooden dowels, which were drilled and straps screwed in place (cooler straps and lifting straps for the garage ceiling hoist). The blue straps were cut from some Chinese imitation Thule straps which came with some roof-top kayak J-carriers I bought recently.

All that remains now is to hang the boat on the garage hoist next to the Chuckanut 12, and then get them both out for a sea trial, probably on nearby Tellico Lake, launching at the Notchy Creek Wildlife Ramp.

Well, I have just fulfilled half of the tasks mentioned in the previous paragraph. The other half may take a little longer.

It’s pouring rain right now, with a lot of rain forecast this week. But I promise a water test report soon, and a “comparo” (as Motor Trend would put it) on the pros and cons of our now sold Wilderness Systems Pungo 120, the Dave Gentry Chuckanut 12 completed in early December 2016, and the modified Sawfish 12 just finished. This will not be a “which is best” report, but just the pros and cons of each as I see them, so every reader can judge for themselves which kayak best meets his (or her) needs. Fair Winds!


  1. Wow! Very impressive. Do you have any additional photos or description regarding the seat mount you devised?

    If I understood your description, you drilled four holes into the foam, filled them each with the PL-III and half inch dowel. When solid, you drilled each of the dowels to accept the screws coming down from the seat. Is that right? Thanks for the articles. Jim

    • The picture of the seat mount in the article is the best one I have. The trick is aligning the holes in the seat mount with the holes in the dowels. The process was: 1-drill the holes in the seat mount: 2-put the seat mount in place: 3- drill small holes through the holes in the seat mount into the foam: 4- remove seat mount and drill 9/16″ holes in the foam: 5- fill holes half way with PL Premium: 6-insert the pre-drilled dowels in the holes: 7- All the holes should the line up: 8- if not enlarge the holes in the seat mount and use larger washers under the screws. Guess how I know that?

  2. Thanks for a great story. Very well written and informative. The whole world is on the edge of it’s seat waiting for sea trials!

  3. Thanks. That article has been written and submitted. It is a “comparo” between our previous WS Pungo 120, my Chuckanut 12 SOF, and the Sawfish 12, telling the pros & cons of each as seen by an 83-year-old guy. Opinions may differ according to the reader’s situation. Sitting on the edge of your chair too long can make your butt numb!

  4. Thanks for a well written description. I live in Knoxville and sail out of the Concord Yacht Club. I too, have a Trimaran project in my future.

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