Positioning of cockpit on a C16

I am about to start decking my C16, which has been built from plans. Interestingly, nowhere on the plans, nor in the Assembly Manual, does it specify exactly where the fore/aft position of the cockpit should be.

The plans indicate that the leading edge of the coaming should be in line with the front edge of main deck-beam. However, since deck-beams may vary in width, mine is 20mm (a tad over three-quarters of an inch), there appears to be no precise guideline. 

Any C16 plans builders out there ?

Dave


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RE: Positioning of cockpit on a C16

I recently completed a CH17LT from plans and had the same dilema.  On the CH17LT plans, it appears that the inside rear edge of the coaming is flush with the forward edge of the aft bulkhead.  It also appears that the outside forward edge of the coaming spacer is flush with the aft edge of the deckbeam.  The overall outside dimension of the full size coaming spacer on my plans was close to 32 1/4.  The distance between the aft edge of the deck beam and the forward edge of the aft bulkhead on the plans is close to 32 1/2 (considering the 6mm thickness of the aft bulkhead).  With these measurements, it would be impossible to have the coaming spacer sit on the deckbeam and be flush with the aft bulkhead.  This is also magnified by the fact that the CH17LT's low aftdeck introduces quite a bend into the coaming which makes it's linear length even shorter.  In the video (which is a CH16) and manual, the coaming spacers are temporarily nailed into deckbeam during assembly.  My nails (I didn't actually use them) would have missed the deck beam had I positioned the coaming flush with the aft bulkhead as the plans showed. 

This all gave me a slight headache so as silly as it sounds, what I did was look at many, many pictures of other builders kayak's (CH16's,  CH17's, LT's and not) focusing on the coaming.  I also read many other forum posts to determine where I should put it.  What seemed fairly consistent was that: A) the inside rear edge of the coaming should be slightly forward of the forward edge of the aft bulkhead; this allows some space for you to install the backband clips and B) the outside forward edge of the coaming spacer should be supported at least a little by the deckbeam...say a minimum of 1/4 inch.

I ended up having the forward edge of the coaming spacer overlap onto the deckbeam by 1/4 inch or so which left the inside aft edge of the coaming spacer forward of the aft bulkhead by roughly 1 inch. Now if you altered the position of the deckbeam or aft bulkhead, all of this goes out the window.

I don't know if this helps you but that was my experience on the CH17LT.  In a twisted sort of way, that's the beauty of building from the plans.   How you interpret the plans and how you cut your materials makes it quite interesting.

Cheers. 

 

 

 

 

 

 

RE: Positioning of cockpit on a C16

Thankyou for your very detailed description.  This will certainly help. 

As you point out, the position of the aft bulkhead can vary from boat to boat so the best guide is to, as you put it, use the aft bulkhead as a datum point and position the inside rear edge slightly forward of the forward edge of the aft bulkhead.

No one could say boat-building is dull !

Dave

RE: Positioning of cockpit on a C16

I just finished my CH 17. On my plans it calls for the Aft Bulkhead 124"  and the Forward Bulkhead to be at 64". The critical measurement to me is the location of the AFT Bulkhead. Once in place you can change the location of the Forward Bulkhead somewhat. The Forward Deckbeam is located at 93" however, many people move the Froward Deckbean so as not to be hitting you knees when exiting you boat. Some people have completed removed this Foreward Deckbean with good results. I moved the Forward deckbeam 10" from the front of the Coaming with good results.

 Don't get to mixed up with all the exact measures. Boat building is fun and allows for several different ideas with the design. Have fun and be happy.

RE: Positioning of cockpit on a C16

"Some people have completed removed this Foreward Deckbean with good results. I moved the Forward deckbeam 10" from the front of the Coaming with good results."

Seriously?  The deck seems pretty darn thin, and I like the idea of the cockpit coaming having solid support at the fore and aft ends.  In any case, I would definitely check with CLC first before drastically altering structural components.

Grant

RE: Positioning of cockpit on a C16

Hmmm...my above post regrarding my CH17LT looks to be anonymous.  Anyway, I had one more thought on all of this cockpit placement discussion which to me might be the most important.

While I have only built 1 kayak and am not a boat designer, I would think the most important factor in cockpit placement is the center of gravity of the boat.  Wouldn't it make sense that the placement of the seat (fore vs. aft) is the primary concern so as to impart the correct fore/aft balance?  Your cockpit would then be placed accordingly around the seat location.  I have built a few R/C airplanes and the center of gravity is critical to making a good flying airplane.  As such the COG is always descibed in the plans and instructions but I never hear of that in this particular hobby.

Dogan. 

 

RE: Positioning of cockpit on a C16

Hi Dogan,

My experience suggests that fore and aft trim is vital in determining how a kayak handles in various conditions.  But before conducting "sea trials" it's not easy to determine what adjustments in COG will be needed.  The position of the actual seat can sometimes be shifted a couple inches.  But since we should always be carrying at least a minimum of basic gear, trim can be adjusted (often according to conditions) by where we choose to stow things.

By the way, Quickstart, I think you definitely voided your warranty!  LOL!!

Grant

RE: Positioning of cockpit on a C16

To Grant/Old Yeller,

I moved my Forward deckbeam 1-2" foreward of the Coaming not 10". However, there is a  posting about someone removing their Deckbeam.however, that is not what I did. Sorry to cause any confussion. I agree with the center of gravity comments.

RE: Positioning of cockpit on a C16

I just finished a Ch16 and installing the coaming was interesting, I had a bad scarf joint on the bow and re-spliced the joint, this in turn meant that my joint between the fore and aft deck pieces was shifted forward and I had to be careful I had enough material to make the length of the yak. It worked out OK and the forward edge of the coaming ended up over the deck beam and tacked down into the beam.

Just a small warning          BY SHIFTING the coaming forward and smoothing the inside surface of the coaming around the back of the seat I ended up with a thin rim below the top coaming ring.

Then , when I screwed the backband up into the rings

I missed the rings, and came up through the deck, #@%$^&*

fill, sand and reposition the screws, and if I don't point it out, you would never know.

As people say, yak building is fun, challenging, and interesting, you spend as much time thinking about how you are going to do it as actually doing it!

Just enjoy the build.

Ted B

 

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