The Acre kayak was my first try at making a skin on frame kayak! I wanted a light weight design that could hold enough for an overnight camping trip.

The Acre is a heavily modified version of a design found in "Fuselage Frame Boats - A Guide to Building Skin Kayaks and Canoes" by Jeff Horton. pretty non-conventional with an overlapping skin design for a cleaner look. The build was pretty painless although the frame was hand cut then cleaned up with a hand router which was pretty rough. Think I will go CNC next time for sure!

Original design was done in CAD. Each of the frame elements was pulled out and put in a drawing package so I could print cutting templates out 1:1. Fortunately most of the parts fit on my 17" x 11" printer pretty well.
All the ribs are cut out of marine grade plywood and the stringers are fir.

Fast forward a through a bunch of hand work cutting out the ribs...
I built the strong-back that the lower stringer would slot into and hold the ribs in place during the build.

Gunwale and stringers are bungied in place.

The upper stringers were steamed and bent around the cockpit for a more rigid hull. Also looks nice.

Stringers are all lashed in place on the top so the frame is flipped on the strong-back and the bottom gets worked on.

There is no glue or standard hardware fixtures used on connecting the ribs to the stringers. The contacting surface area is so small that any connection like that would just snap when the hull flexed.
Instead everything is tied together using synthetic sinew. The amount of tension you can get on the lines is pretty crazy and you can see it biting into the birch and plywood.

The frame is completed and the adjustable footrests are in place.

More complex lashing passes near the bow.

Lot going on with everything coming together at the stern. You can also see that the frame has been covered in tongue oil at this point.

The combing was split down the center to better follow the contour of the deck. You can see the all the through holes running along it for the fabric to be tied through later.

8oz polyester is draped over the top of the frame for the top deck.

End result of the top deck. The polyester has been stapled down to the underside of the gunwale and lashed around the lower combing.

The polyester top deck has been heat shrunk with a heat gun at this point. The fabric is super forgiving and takes up a lot of slack once you get some heat on it.

The polyester takes oil based paint great! I 1:1 turpentine mixed in with it to get watercolor like saturation on the top.

Polyurethane sealant (usually used for concrete floors) has been applied to the deck fabric to get it water tight.
Fiberglass rods and heat bent ABS plastic rod front/rears are connected with stainless steal tube to create a top hoop. This will be the attachment point for the deck webbing and shock cord.

The lower hull is draped and sewn around the top fiberglass hoop. This will all come under tension when it is heat shrunk.

Continuing working down the rails and sewing the stern.

Multiple running stitches are done to clean up the hull fabric and secure the webbing around the frame.

Final running stitch going down the starboard side. This one pierces through the top deck fabric to the interior to lock down the hull fabric through the deck.
It was so painful getting the upholstery needle around through the sealed top. Had to use a mixing stick to force the needle though the deck instead of my thumb!

Sewing in the bow.

All the sewing is finally done with the excess in the bow and stern lashed down.

Finally screwed down the upper combing to the lower combing.

You can see how much slack is taken up in the heating of the polyester. The left side is how it naturally sat and the right is after it was hit with the heat gun.

Interior looks good too!

Combing attached, only thing left to do is seal the bottom!

Combing attached, only thing left to do is seal the bottom!

Bottom has been sealed. I taped off the sides and added the painting detail along the rails to clean everything up.

View from the completed interior.

Bow side bungie and webbing detail.