PDA

View Full Version : SOF canoe - station design



mdmiller1
08-06-2015, 12:54 PM
I have a friend with a northstar 12' solo that I want to clone as an SOF canoe. Planning on using a flexible 36" french curve and transferring the shape at selected canoe cross-section points onto paper to create a template for the stations. My question is on rib spring, should a certain amount of spring be designed into the stations (really not sure what to expect though), or should the stations be cut to exact profile shape?
Appreciate any advice, many thanks - Duane

SNAPMAN
08-06-2015, 01:47 PM
Duane,

Are you using laminated or simply steamed ribs? How many permanent spreaders/seats are there in the boat?

If it is the same as the Northstar (4 spreaders and a seat) you should be fine once it is assembled, as they will keep the hull in the original shape.

When I built Helium, the stringers pulled the ribs in more than the ribs pushed the stringers out. If you look at the pictures in the Helium website, you will note that there were always spreaders in the boat once the temporary frames were removed. With the 3 cross-spreaders, it has held it's shape perfectly.

Alan
https://sites.google.com/site/helium12sofsailboat/home?pli=1

DGentry
08-06-2015, 01:53 PM
I have a friend with a northstar 12' solo that I want to clone as an SOF canoe. Planning on using a flexible 36" french curve and transferring the shape at selected canoe cross-section points onto paper to create a template for the stations. My question is on rib spring, should a certain amount of spring be designed into the stations (really not sure what to expect though), or should the stations be cut to exact profile shape?
Appreciate any advice, many thanks - Duane

Cut your stations to the exact shape. If you have a substantial gunwale/inwale system, and/or at least one thwart (the backrest, for instance) bracing the gunwales, your hull should hold it's shape.

Good luck, and feel free to ask questions if you get stuck.

Dave Gentry

mdmiller1
08-06-2015, 03:15 PM
Thanks for the replies.
I'll be steam bending the ribs and matching the spreader/thwart length and connection points, as in the ADK solo.
It uses a pad for a bottom seat, kayak-style. I need something very light for the wife who prefers a kayak paddle, this design looks about right.

Todd Bradshaw
08-06-2015, 06:30 PM
Depending on how it goes, you may find that you need a bit more stability than a French curve provides. We used to take the lines off of canoes by setting them on a strongback beam with U-shaped cross members, braced and hot-glued to the beam every couple of feet, and also a couple L-shaped ones, positioned lengthwise off of both ends. Then we cut a bunch of pointers from scrap wood and stapled them to the cross beams where they just touched the hull. We would carefully remove the boat, remove the cross beams and mark the pointer ends on a sheet of paper with base and center lines. It proved to be pretty accurate with proper centerline markings and leveling. Plus, it was quick and cheap to do.

The finished crossbeams looked like this:

http://i1303.photobucket.com/albums/ag153/ToddBradshaw/assorted/fbf052bf_zpskej0q32r.jpg

And a stack of them with the points all faired in looked like this. This is a B.N. Morris canoe from about 1900.

http://i1303.photobucket.com/albums/ag153/ToddBradshaw/assorted/morris-001a_zpsf9drqcl0.jpg

nedL
08-06-2015, 06:54 PM
I was thinking along the same lines as Todd. You could alternatively cut large "horseshoe" shaped sheets (as Todd shows) and then use a joggle stick to duplicate the shape at each station.

Gib Etheridge
08-06-2015, 07:29 PM
Do you know anyone with a laser scanner? They're often used to take lines these days.

mdmiller1
08-07-2015, 10:03 AM
Stability of the flexible curve is a concern and could be an issue. Your template method reminds me of the template a fellow created last month to template our countertops for replacement, and it was very accurate -- he put some complex shapes together in a few minutes using strips cut from mahogany door skin material and a hot glue gun. I considered finding a 3D scanner but I'm thinking a manual duplication method will better fit my skillset. I should get the french curve delivered by next week and will determine if it can be used; I'm hopeful that it will hold it's shape for transfer.

mdmiller1
08-10-2015, 12:05 PM
I received the flexible curve for creating templates for stations; so far I'm very impressed with it. I shaped it into a curve then drew a line with it, carried the flexible curve around the house with one hand, laid back down and it fit perfectly. From amazon, there were a number of brands but this particular one was repeatedly described as very stiff and I would concur. $9.85.

http://forum.woodenboat.com/attachment.php?attachmentid=2752&stc=1