is now about building a new Sonnet inflatable / folder, I've decided to start a new thread.
viewtopic.php?f=27&t=2946 - "Homebuilt kayak durabilty and seaworthiness". Scroll down at the link to find the Sonnet skinning frame pics / text.
The Sonnet 16 in the "Inflatable Kayak Builders Manual" differs in a number of ways from the new Sonnet Combi. Most notable is the use of 3
sponsons per side vs 2 sponsons per side on the Sonnet 16, and nylon sponson sleeves vs glued PVC sleeves, This change necessitates
the use of 2 stringers per side on the Sonnet Combi vs 1 stringer per side on the Sonnet 16. The stringers are inserted lengthwise between
the sponsons and work in conjunction with the sponsons to provide shape and rigidity to the structure. Like the Sonnet 16, the side
stringers are free standing with no connection points to the stems for ease of assembly. I hesitate to call them chines as the sponsons are
the chines, as well as the gunwales.
..... The following is a description of making nylon sponson sleeves for the Sonnet Combi.
The sleeves are lightweight rip-stop nylon with a top and bottom section sewn together to create a D-shape for each 15' Folbot sponson.
The bottom section contains 3ea X 3.5" sections that are sewn to a top that has 3ea X 8" sections for a total individual sleeve circumference
of 11.5" to accommodate the 11" circumference sponsons. Between each individual sleeve are 3/4" wide flat sections that isolate the 3/4"
aluminum tubes. I made 4 ea X 93" sleeve sections for ease of sewing. 2 sections per side will hold the 15ft sponsons.
Sewn to the bottom sections are full length 6" wide 10oz PVC strips for glueing the sleeve to the inside of the hull .
Sonnet Combi "Sponson Sleeve" Pics ......
The yellow nylon bottom and red nylon top are sewn together along the lines draw on each section. This forms a "D" shape and allows the
bottom to lay flat against the inside of the hull. Before starting, I immersed sample 12" nylon squares repeatedly in water and measured
them again after drying each time. The coated yellow nylon ( Seattle Fabrics) showed no shrinkage, and the red ripstop nylon ( JoAnn Fabrics)
showed just a very slight amount. I oversized the sleeves slightly ( 1/2") to compensate for any shrinkage while in use.

Rita sews the sponson sleeves on her Pfaff. It took her about 12 hours to sew the sleeves, Some of that spent finding the right dimensions via sample sleeves.

The top of the 93" sleeve . A second sleeve (folded) is on the next table.

The bottom of the sleeve showing the 6" wide PVC glue strip (10oz). If not glued to the inside of the hull, it would be very difficult to position
the sponsons and aluminum tubes during assembly.

Sponsons inflated with 2ea X 93" sections butted together to form one full length sleeve.

Inflated full length sponson and sleeve. 186" sleeve and 180" sponson. The sleeves may be shortened if needed when attaching to the skin.
I haven't decided yet whether or not to sew the sleeve ends shut.

Inflated sponson showing bottom of sleeve / PVC glue strip.

2ea... 3/4" 6063-T832 aluminum stringers inserted between the sponsons. These, the 1" keel , and 3 cross brace tubes are the only hard
structure in the frame. There are no cross sections like those found in most folding kayak frames. During assembly, the inflated sponsons will
trap the side tubes (stringers) and they will not be visible.

This is a prototype , so there likely will be changes to the above as construction progresses. Building a prototype is very different than
following plans for a boat already developed from tried and tested materials and processes. The sponson sleeves are the sticking point for
this type construction. From here on in, it's all down hill

The aluminum Sonnet frame is much easier to build than the standard "Feathercraft style" frame on my other folders.
Next Time... Gluing in the sponsons and skinning the hull and stems.
Regards, Tom