SOF completion

Here are some pictures of a geodesic SOF 14' canoe build. Stringers, thwarts, breasthook, inwhales, outwhales, stem, keelson are Douglas Fir. Ribs, cutwater and keel strip are oak. Canvas is 3.7oz dacron. Diagonals are kevlar roving. Wood members are bonded and encapsulated with epoxy then varnished for UV protection. Covering outside is coated with plastidip to retain weave flexibility then varnish. Inside is varnish. Weight 28lbs. Design capacity 2 px

Dino

First pictures need no explanation. Last picture of previous post is pre-bending in and outwhales


referance line on strongback and mold frames

steambox assembly waiting for oak ribs shown installed

Frame released from mold

inwhales installed

thwarts, breasthook and floorboards added

covering after attaching diagonal rovings then retensioning rovings after heatshrinking dacron

highly diluted plastidip elastomer brushed into weave so covering remains flexible and tough after varnish topcoat has dried

Keel, cutwater and rub rails followed by varnish and it's done

Thanks for posting. Excellent sequence. Great boat.

I second Dave's comments.

I wonder if you might expand a bit on "highly diluted plastidip elastomer brushed into weave so covering remains flexible and tough after varnish topcoat has dried."

What did you use to dilute, and in what ratio? Is there a particular brand you used? Is this your own idea, or did you learn of this elsewhere?

I presume that this coating is intended to overcome, at least a bit, dacron's trait of tearing more easily than canvas?

Plastidip coating is an idea tried by one builder as a waterproofing method. It is mentioned in the build manual as a possible inexpensive substitute to coatings made for Hypalon inflatables. I bought some clear coat product and was advised by the tech assistants of the manufacturer that the unpigmented variety had UV stabilizers in the formulation. My idea was to encapsulate the polyester (Dacron) in a permanently flexible matrix that would block subsequent varnish coats from locking the fibers as the varnish aged and hardened. Coating schedule is as follows:

Outboard. 2 coats Plastidip diluted 50% in naptha to dry film thickness about 5mils, Epifanes clear spar varnish 2 coats at 20% diluted in white spirit, 3 coats 20% diluted Helmsman urethane spar varnish satin with stain additive to mask plastidip blotchiness and add sepia satin hue.

Inboard. After confirming that plastidip had wet through the dacron, 3 coats Epifanes spar varnish followed by 1 spray coat Helmsman urethane satin varnish to dull high gloss of previous varnish coats.

Reasoning is that Dacron polyester has superior mechanical characteristics compared to cotton. It is also heat shrinkable. Both fibers lose some resistance to tear and puncture resistance when set in a hard matrix like epoxy or aged varnish. Body armor is made of Spectra or Kevlar fabric sheets that are compressed together and not laminated with resin to help stop bullets. Also it is a common observation that fabric boat coatings lose a degree of puncture resistance as the coatings age harden over time. My reckoning is that since Plastidip remains permanently flexible it will mechanically isolate the fabric fibers from other coatings that harden. If the blotchy finish with minimal UV resistance is acceptable you're done. I added considerable weight by epoxy encapsulating the wood frame and subsequent fabric coats for appearance/UV protection.

Glad you enjoyed the build. I was apprehensive that the purists would take me to task.

Dino

Picture is after after plastidip coatings. Notice blotches on dacron from different degress of coating penetration that is difficult to control. If an opaque finish is acceptable the Plastidip comes in color spray cans. One or two light coats and you're done.

Thanks. Food for thought. And I'm not sure what a SOF purist might be -- I don't think anyone expects seal skins stretched over a drift wood frame.

Greg

Very pretty. I have been saving thick cardboard for the formers on my 12. I'm kinda inspired!

On the Water

Dino

It looks beautiful! Thanks for sharing. Paddling-pictures are welcome too!

Beautiful boat, outstanding build, and a darling paddler, I'm considering a SOF for my 9 and 11 year old girls. That looks manageable for a dainty girl. I think you kindly responded on another thread to my questions.

Its real early but is there anything you would have done different?

Yes. I would have been more meticulous in steam bending the oak ribs so they more closely followed the curve of the stringers. This must be done without leaving any pretension that would disturb the hull form after it is released from the mold frames. Some have a gap of several mm that I bridged with epoxy-cotton flox bog which while structurally sound adds weight and is unsightly.

Dino