Keyhole Cockpit for Outer Islander?

I didn't put a keyhole cockpit in my Outer Islander build - I wasn't a very experienced or capable paddler then, so hadn't yet 'seen the light' on cockpit shapes and sizes! :)

Since then I've used a keyhole (Romany copy) cockpit on all my boats. I wouldn't build or use any boat except for a dedicated rolling boat without a keyhole cockpit. It's safer (quick exits and entries/re-entries) and much more efficient since it allows my knees to be  'up' at the midline for much paddling.

The seat position should be where the designer has specified as this affects the fore-and-aft balance of the unloaded boat. Make sure that the cockpit shape will put the thigh pads on the paddler's thighs, not kneecaps - this is a big problem in fitting commercial boats to shorter paddlers.

It would be worthwhile to take a couple of days to make a rough mockup section of the kayak to make sure you have the position of the cockpit correct in relation to the seat. Here's a pic of the cockpit area of my recent Thomasson Njord build. You can see :

-the cockpit rim profile is flat

-I've changed the shape of the forms to conform to the cockpit plane

It helps a lot if the deck can 'roll over'  in the thigh area if the design allows for that. If you have a chance to sit in a Mariner or a NDK Romany/Pilgrim/Explorer you will see what I mean. If the deck 'rolls down' you won't need a lot of foam to make secure thigh pads for rolling and bracing.

About the flat plane of the cockpit:

Read https://www.thomassondesign.com/en/news/cockpit-rims

BTW, the Outer Islander is the most straight-tracking kayak I've paddled.

I couldn't find the thread where I posted details on the cockpit rim fabrication, but you might find some ideas on the posts from my Frej 16' build:

http://www.kayakforum.com/cgi-bin/Building/index.cgi/md/read/id/222790/sbj/strip-building-bjorn-thomasson-s-frej/

 

Here's a pic of the cockpit on my Panthera.  The cockpit rim is recessed into the deck, which requires quite a bit of extra work - especially if you are finishing the boat clear. I paint my boats so I can mix glass and wood where convenient.

You can also see the temporary 'teeth' I used to help align the hull and deck.

The basic idea of the cockpit rim fabrication is simple. Make an over-width sacrificial form using rigid insulation board. Glue that form to the deck - I use epoxy with lots of Microlight or balloons to make sanding easier, later. Use spring clamps to hold the form to the deck till the glue cures. Sand the under-deck to meet the form in a smooth transition. Hand laminate pre-wetted stips of glass over the form, wrapping the glass under the deck. You can add black SystemThree pigment to the epoxy if using all glass. If using carbon use a non-amber epoxy (S3 Silvertip or similar). Add at least one layer of glass over the carbon to protect it when sanding. You'll need quite a few fill coats of straight clear colourless epoxy over the rim so that you can sand it smooth. I find that I usually need the equivalent of '40 oz' of material to give enough stiffness and thickness to the rim - so several layers of 6 oz glass and one or two layers of carbon. The carbon tends to open it's weave unless you are extremely careful in handling it, so a double layer helps prevent 'see-through' spots. Remove most of the foam with a wire brush and get the remainder with acetone and a scotchbrite pad.

Carbon is expensive but it does impress folks and looks good!  :)

Hope this helps!

Ken-

I'm glad to help!

When I built my Njord last fall I was concerned about the room for my feet - I like to be able to move my feet a bit when paddling (bulkhead as footrest) and I knew from experience that Bjorn's boats are tight, even for my Sz10 shoes. My Frej doesn't let me wear anything except very minimal whitewater style 'creek boots', even with my feet jammed in, heels touching. So I made a mockup of the foot area and decided how much to raise the deck (more than the 'High deck' option on the plans. I raised the deck at the sheer, not in the middle, BTW.

If you can get 'up close and personal' with a good commercial kayak (like the NDK/SKUK boats) with a cockpit that fits you, take a tracing of the inner and outer cockpit rim shapes, using posterboard.

I use the same (Romany) shape on all my builds - it's easier to have the same sprayskirts fitting all the boats.

 

FYI:

If you need to buy carbon cloth, CST (Composite Store) has up to $40 off (19%) using the discount code CV19.

 

Just had an email from them.

The NDK boats have what I would call a 'true keyhole' cockpit - the inner edge of the opening is like an old-fashioned keyhole escutcheon.

A lot of manufacturers just add some protruding 'fins' or wings (aka 'thigh hooks) to an oval cockpit rim. The advantage of that style is that the fins/wings can be movable (in a good design), so they can be moved fore/aft and closer and farther from the midline by using different bolt holes.

The 'thigh hooks' can also be made in a curved shape to cradle the paddler's leg. 

I think the Pygmy kits use plywood thigh hooks.

If you paddle with your knees in the middle very much, it's nice to have the edge of the 'thigh hook' area as smooth as possible. That's one of the things I like about the NDK style keyhole.

Romany:

WS Tempest Pro

Depending on the paddling style, boat, and paddler (!) thigh hooks may not be necessary. Here's Freya Hoffmeister's 'Freya' cockpit.

She paddles with her knees at the midline most of the time, and is also an excellent roller (competed in Greenland rolling in the past).

 

John,

I am going to try your approach on my next project (just finished a CNC Vember build for my wife).  In your post you indicate that 40 oz of fabric is about right.  I assume that means say 8 layers of 5 oz fiberglass.   If one uses say 2 layers of 5 oz carbon,  how many additional layers of 5 oz fiberglass would you recommend.

Thanks

David

p.s. I am not sure of the rules of this forum.  Is posting pictures of finished builds encouraged?

David-

My recommendation would be to do an experiment - lay up layers on a flat surface (a piece of plywood a piece of scrap melamine shelving, covered with plastic or wax paper) and see how stiff/flexible the result is. You won't need a very big test piece.

I use bias-cut strips for rim lamination, so you will have some triangular scraps for experiments if you do that.

I'd probably think of 5oz as '6 ounce glass' . Also, carbon is light but thick and soaks up quite a bit of resin.  I'd probably start with 2 or 3 layers of 6 oz glass and then a couple of layers of carbon twill, then a top layer of glass. The carbon is mostly for cosmetic effect used this way - for strength the carbon should be the outer layers with the glass in the middle. The only reason I use 2 layers of carbon is that there will be clear spots where the weave opens, with one carbon layer. That could be avoided by using black pigment (SystemThree) in the first glass layers, but I recall that the black epoxy tended to migrate into the carbon and obscure the carbon 'look'.

Probably thinner would work just as well, but I really would be embarrassed if the coaming broke during a rescue practice.

BTW, for me, this is an extremely 'messy' layup with hand massaging to wrap the glass under the deck. You should protect the inside of the boat with plastic or brown paper taped into the cockpit.

Using carbon this way is really mostly just for vanity and to attract praise- I admit it! :)  It does work! :)

It's nice (with a painted boat) to see the surprise on people's faces when I pop open the hatch and prove that it's a 'wood boat'.....

I do much prefer the thinner glass coaming rims like the commercial glass boats have. Thicker rims, like plastic boats have, don't seem to grip the sprayskirt as well.

Pics are more than welcome here, I think.

I try to keep the file size (and dimensions) down, but some forums automatically re-size images to accomplish this. Not sure if that's the case here,  so probably best to check the file size before posting. Some users are still on slow connections or may have  data charges which are costly.

I said: 

 Here's a pic of the sacrificial foam mold for the coaming on my current build, a Bjorn Thomasson Panthera.

Unfortunately the site is indicating errors with my images - not sure of the reason for that.

anyway....

I use pink 'Formular' insulation board 1" thick and use a roundover bit in the router table to shape the inner edge.

I sand the deck edge to make the transition on to the mold.

I glue the mold to the deck with epoxy and 410 Microlight so it is easy to sand the deck smooth later, after the foam is removed.

For this layup, the first layer was a coat of thickened black-tinted epoxy, then 3 layers of 6 oz twill, then carbon, then a twill layer. Later I'll sand carefully and add epoxy so that I can end up with a smooth surface. I usually clearcoat the coaming and seat.