Cockpit and spray skirt sizing

[SZihn]

Hello to all you good folks out there. I have a question maybe someone can answer for me:

I would like to know the circumference of the outside of the combing on kayaks that takes a Seals 1.2 and 1.4 size skirt.
My idea is that if I know the circumference and I make a string loop of that size, and the combing of future kayaks can be made to size using the loop to make the forms. When done those cockpits would fit the sizes perfectly.

Is my logic sound?

 

[JohnAbercrombie]

I think it would be better to get tracings of cockpit coamings that fit your skirts.
A long skinny coaming vs a shorter, wider one - same circumference but one skirt wouldn't fit both.
Some coamings are more 'oval' - broader at the front - than other more 'pointey' shapes.

I've had skirts that seemed to fit the coaming, but pulled away from the rim at the side when I leaned 'too far'.

But your idea of 'standardizing' on a cockpit shape for builds is one I share. In my case, I picked a very popular (and common) boat - the NDK Romany - and copied that shape.

I think the Seals 1.4 fits most Mariner (Seattle) cockpits, BTW.

 

[SZihn]

That's probably very good advice John.
So far I have only one for a Chatham 17 which takes a 1.7 and a Wilderness Systems Piccolo which takes a 1.4. I have not seen anything yet that takes a 1.2 But if I standardize on the 3 sizes, a 1.2, 1.4 and 1.7 I doubt I'd ever have a reason to make a cockpit that was not one of those 3. I bet those 3 would cover all builds from a kids play boat to a full size sea kayak for a large man.

Can you thing of anything I am missing?

If anyone out there has a kayak that takes a 1.2 and would be willing to send me a tracing, I'd truly be thankful.

 

[CPS]

Many/most commercial kayaks these days seem to be those sizes. Usually 1.4 or 1.7, in my experience.

Often one can swap between a 1.7 and a 1.4, depending on paddler's preference. For example, a 1.4 fits on my Necky, and is apparently correct according to Seals' sizing charts, but I find a 1.7 a much better fit. The 1.4 is so tight that it's at risk of popping off.
Another example would be a Stellar kayak that calls for a 1.7. A colleague used a 1.4 with no issue, though she likely prefers a tight fit, coming from a very high level whitewater background.

I think the general trend is for larger cockpit rims, they fit more people more easily.

 

[JohnAbercrombie]

What @CPS said ^^^^^

 

[sofstu]

I agree with everything said.

Before I made my first coaming I had 1 rule.
I must use a common shape and size, so I can head over to any water sports store and buy one off the shelf if required.

I am grateful that you are doing the same thing.

 

[BigandSmall]

Along with circumference, paddler position and width at the various areas make a huge difference as John mentioned. I look for boats that take a 1.7 with the paddler at the rear of the coaming. Unfortunately Seals puts the paddler position a little forward of that as if to fit a WS Tempest perfectly. That style of cockpit/seat position makes heel hook re-entry's easier IMO for holding the paddle. Likely helps with rolling too. Since I paddle a Scorpio HV it's wrinkled behind me and tight in front. My wifes uses a Seals 1.2 on her Avocet RM and her Tahe Reval mini before that. It wasn't a good fit on either. Even though the rand is tight the fabric is sagged in areas that allow water to pool and drip. I don't mean to be speaking ill of Seals. Every boat should have one of their cockpit covers and I love their Seasprite model skirt. Brooks used to offer a service that you could send a template of your cockpit in as well as choose paddler position and tube size. Not sue if that's still the case. In any case I'd suggest keep renting boats until find that one with the perfect cockpit to copy the dimensions from. My three favourite cockpits have been my Scorpio HV, the Baffin C3 and the Delta 18.5E. Easy butt first entry and great contact in all for me. I'll be using the Scorpio cockpit dimensions in a build down the road with a Redfish seat and a IR Lounge band if can ever find one in Canada.

 

[SZihn]

This is all useful information for me.

I hope to find a program on-line that can give me the center of buoyancy location for any design I come up with. If I can get that, I can position a cockpit over the position where a Seals spray skirt will fit perfectly, and position the seat precisely to allow for it, so the back and butt of the owner are against the back of the seat and back-band when the skirt is centered on their torso with no pull or wrinkling at all.

I could make a balance board so any given paddler could sit on it and I could locate their individual center of gravity so the paddlers center of gravity could be directly over the center of buoyancy. It would be a seat on a board with a roller under it. I'll have them roll back and forth until they are balanced and see where that point is on their body. Most will be a few inches in front of their crotch, but a big man with a bit of a gut will shift that location farther forward then a small slender woman. I can set the kayak seat to place that measured location directly over the center of buoyancy of that particular kayak.

Of coerce loading the kayak with gear will off-set things, but at least I could get it perfect for them before they load any gear.

There so many cool little modification that can be made if you have the ability to make the decks, hulls and cockpits. In any hull, I probably have 6-8 inches of room to adjust back and forth for seat position. If I can establish that, I can make the cockpit exactly where it needs to be to have the skirt fit in a relaxed way.

I am very thankful to you all for the input.

I am making notes.

 

[JohnAbercrombie]

I hope to find a program on-line that can give me the center of buoyancy location for any design I come up with.

I think Kayak Foundry will do this? Probably others as well. @mick_allen and other designers here will have that info, I bet.

BTW, when thinking about seat placement in the cockpit, my top priorities include providing enough leg room to allow the paddler to do a 'butt first' entry (and the usually more difficult, 'feet and legs first' exit). The other thing that often causes problems is getting the paddler's thighs (not kneecaps) under the thigh padding. The former is more of an issue for the long-legged, the latter for shorter-legged paddlers, in my limited experience.

Having at least a couple of inches behind the seat allows stowing a sponge and inflatable paddle float; more space there can accommodate water bags etc.. It also allows easier 'back clearance' when trying to do layback rolls, if the seat is farther from the coaming.

 

[mick_allen]

a program on-line that can give me the center of buoyancy location for any design I come up with

solidworks [which you have I think] will be able to do that along with any other [Kayakfoundry as John says] 3d marine programs that you choose like the delftships, freeships, solidworks, 3d autocads, rhinos, blender [almost certain], catia, etc etc etc. There are/were even dedicated [to buoyancy calculations] programs for this.

 

[SZihn]

I am trying to understand the solid works tutorials now. Even they are well above my head, but I am learning. (very slowly) I don't know ANYTHING about computer design ,and I do mean nothing at all, so I am starting at "pre-school level"
All the other things you named are a foreign language to me as of now. But I have to start somewhere.
Mick, is there one that you'd recommend above the others for a new guy to learn?

 

[mick_allen]

With any of them you have to humble yourself and put in the time. And you, me, and others have and can achieve results with any of them.

You in particular, are in the envious position of having one of the programs plus an instructor available at your fingertips: you are golden.