Andrew

It all depends on which Sailrig you're adding to your kayak.  The Mk III, with its 70 sq ft sail, requires the most work.  According to the SailRig manual, CLC recommends 3 layers of 6 oz fiberglass in a 10 inch band running from rail to rail on the underside of the deck at the mast opening, and several layers of 6 or 4 oz glass to reinforce the mast step on the floor of the kayak.  This can all be done after the kayak is completed.  At the stern, you would want to be sure that either your epoxy end pour is thick enough to absorb the full length of the eye bolts/rudder attachment, which are embedded in fresh epoxy after drilling through the stern, or use a wooden stern block instead and through-bolt the rudder bolts, which is the way I chose to go, using Laszlo's example in his Wood Duck 12 construction series.

 If you look for posts added by "What could go wrong", you will find his info on strengthening his kayak for the CLC Mk III sail rig, especially in his post "Finished the Mk III conversion and sailed to Catalina".  He did a lot.  Whether all of it was necessary will no doubt be argued by others.  His remarks concerning beefing up the leeboard are useful, as well as his finding that his commercial rudder wasn't large enough to handle the loads of sailing, which leads to useful information about making a balanced rudder which works much better.

I'm working on my SailRig Mk III conversion now, to add to my WD 12.  The only other change I made was to glass the inside of the hull to add stiffness.  I'll do all the extra deck and cockpit floor strengthening once I have located the exact placement of the mast.

Enjoy your build.  And get that manual again.  You'll need it.

Peter 

Hi,

I've got a Sport Tandem with the sailrig MK3 set up and I use stays as the mast is extremely bendy in reasonable winds - first video below.

Have a few videos of various setups on youtube if interested:

https://www.youtube.com/watch?v=mZTb-kBewE4

https://www.youtube.com/watch?v=4E8jH7c1F1A

The first video had 20mph+ winds and the mas t looked like it would snap - hence the stays.

Will be testing more of my larger old windsurf sails shortly as they seem to perform very well and put no stress on the hull.

No problems on the hull so far - strengthening around the mast step and under the hull seems to have worked quite well.