GEAR: sea kayak sail_update

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Several years of using sails on my sea kayaks has lead to refining my initial set up.
I no longer sew my sails but I still create my rigging, using custom made carbon masts.
On some narrower kayaks my sail set up was not as bombproof as I would like it to be where in a strong breeze (above 20 knots) the mast would not keep vertical and the little polymer base would deform under the lateral pressure of the wind. In a beam wind I would like to have my mast in a vertical position, making the sail more efficient and increase a bit of speed.
Mick at Flat Earth Kayak Sails has developed a brilliant way to reduce the down pressure on the flexible joint and is now shipping his sail with a new system where the mast contacts directly the removable fitting.
I want to use carbon fibre masts but I have been unable to find an off-the-shelf mast that would replicate Mick's system.
Not wanting to bond aluminum to carbon to create the oversize sleeve for the mast, the only way I could achieve what I wanted was to modify my existing masts to create the sliding foot sleeve.

mast uphauled
Instead of having a larger diameter mast running the whole length, I just made a short sleeve out of glass fibre tape wound around a tube of slightly larger diameter than my carbon mast. Once cured I bonded a the sleeve section to the base of the existing mast and covered it with carbon cloth for strength, and looks :-)
The sleeve section slides over a stubby base with the flexible polymer allowing the mast touch the actual hard surface of the red plastic base.
No load is now exerted on the polymer so it will no longer deform when the mast is uphauled and cinched down hard.

mast lifted for demo purposes
Of course the mast can still be lowered as before and when the sail is folded onto the deck the mast slides back up just enough to allow the flexible polymer do its job.



To prevent the sliding mast and the stubby base come apart I have used a short piece of shock cord threaded internally holding the two together.



I have also improved my anchor point for the stays on the mast.
I no longer use a stainless steel ring riveted with a saddle to the carbon tube but I prefer the use of soft Dyneema core line bonded directly to the mast with a section of carbon fibre cloth.
The load is distributed better and there is no risk of cracking the thin carbon tube with the pressure of installing (pulling) a stainless steel rivet.

mast rotated to show the carbon cloth anchor for the Dyneema cord
I have been using the new recessed anchors with great success, locating them right on the seam of the hull/deck to achieve a wider stance and a better load angle.
The stainless steel shackles are now heat shrunk (see warning below) to the Dyneema stays so they don't rotate when the sail is lowered on deck.



The whole assembly, viewed from the bow.


WARNING:
update 04JAN13
Richard Sharp from SEQSK has this to say:
"I had the sail up in 20knots and got hit by a gust which tipped me in. It
was at that point that I noticed the sidestay had snapped. Finding it hard
to believe that this was possible given the breaking point of spectra, I
examined the break closely. It was then that I discovered that where it had
snapped the internal spectra cord was melted together. See the enclosed
photos."





It appears that the core has melted while the outer sheet remained OK.
Using a heat gun at close quarters causes the Dyneema/Spectra fibres to fuse and become very weak.
The melting point of Dyneema is much lower than the outer polyester (pictured here black) and no noticeable damage was visible from the outside.
He now prefers to use the heat shrink only over the loose end of the rope, not over the entire knot and apply very gentle heat for longer to allow the tube to shrink.