When I round over the edges on my akas (soon), I'll start with a 1/4" radius and see how that looks.  I can always go to a larger radius after that, like a 3/8", if I think it needs a little more.  I probably won't go to a 1/2" or larger, as that will start removing a lot of wood, and I want to leave the akas as stiff as possible.  

  Good plan. Thanks!

Hi,

I've built the Sailrig conversion onto my Sport Tandem and I used a 1/4 inch radius. Works well with the lashings and looks fine.

I wouldn't bother wrapping them with glass for any strength - my standard aka's work fantastically well and my boat is very heavily modified with an RS200 jib, stays and trampolines on the aka's.

No sign of any problems at all and minimal flex is probably useful in dmaping the ride slightly.

If using the sailrig Mk3 from my experience some light stays and putting more attachment points on the sail to slide into the track improves the sail shape markedly.

I've put some clips on youtube - search "kay maran" and I've posted various things here and on smalltrimarans.com as well. The mast flexes crazily in decent wind - see the video called T1mmy - the boat has had some serious loads on in some heavy conditions when everyone else has gone in and no glass needed on the aka's.

I also have some thick adhesive neoprene under the akas where they sit on the deck which seems to help again with the aka's having some slight flex and ensures a really good load spread across the deck.

Good luck with it - they are fantastic fun and surpisingly quick.

   Hi Algieb,

Thanks for the comments. I've seen your videos. You've done some very nice work. I'm building a Chessie Double, which is a little fatter than the Sport Tandem. 

I've been in contact with John Harris, who had some suggestions for me. He's the one who suggested sheathing the akas. We may be going into some 6-foot seas with it, and the extra strenght will give us some confidence.

Another of John's suggestions was mounting the leeboard inboard (in a case in the hull) to strengthen it, and to make room for paddling. I thought that was a great idea. He had it in the center of the forward cockpit, with the forward edge of the case attached to the laminated deckbeam. I'm taking advantage of the generous beam on that boat and shifting it to the right, still bonded to the forward deckbeam, but under the deck. That will seal it completely off from the cockpit, and probably make it structurally more sound by attaching it to the starboard sheer clamp and to the deck itself. The board will go through a slot in the deck. I did a test fit and found there's lots of room.

I went with the big sail primarily because it can be reefed (the sleeve-luffed smaller sails can't be), with is important in open water; and to catch the light breezes better. We'll probably be on the first reef much of the time, especially when the wind is up.

I should have said actually that I think the biggest issue is the leeboard, the little brackets suggested are notsatisfactory at all with the power the sail generates.

Now that I have my fore/aft position pretty well resolved I am going to review the leeboard set up.

We don't think we have room to put the board inside but that would be ideal. I am going to consider further though looking at how it might fit through the hull to see if that is possible in anyway. I would be really interested to see any pics/vids you might have of your set up. I don't think the leeboard needs to be particularly big on the Sport Tandem so possibly a smaler one through the hull could be possible.

The flex in the leeboard is extensive currently (although it hasn't had any problems as I double layer sheathed it) and next time I will not have the "handle" cut out of the board but will add a handle extension to give more leverage and increase the surface area of the bracket hugely to spread the load as it can be tedious gettting it up and down.

The sail performs well when reefed but I would strongly suggest you try the stays and think about a small jib as the increase in performance is incredible - the mast flex which is seriously mad in higher winds is controlleld and the sail shape is much better. The exta attachment points to the mast track also fundamentally helps a lot.

Finally the mast position fore/aft for balance is crucial - the inability to tack with the suggested set up was hopeless for us, now we can tack with no problem and steering is much more responsive. What is the loction on your Double?

I am actually going to try the mast further back again behind the front cockpit which I think will be too far but might then try a larger jib to balance it up. If that works then there is psace for an inboard leeboard. I am going to add an extra bulkhead behind the front cockpit and it could be easily integrated into that potentially.

We have various points in the deck available for various masts as at different points we have had 2 masts using various cut down/modifued windsurfer sails which again have performed really well.

Finally I am just about to pick up an old spare RS200 spinnaker to whack on it and see what happens... Hopefully will have that at the end of this month and will post the results when I can.

Always lots of things to experiment with!

   Yeah, the Sport Tandem is much narrower that the Double, which has a 30" beam. 

I noticed you ran a couple of stays from near the mast head to bridles attached to the akas. Did you need the forestay to balance those, or is that just there for the jib? How did you attach the stays to the mast?

I'm trying to keep this as simple as possible. I'm willing to give up some performance for simplicity. If the stays will make it more rugged and less likely to break, I'll give it a try. But I remember my experience sailing Lidos many years ago. The stays were attached to the deck, rather to chainplates on the hull, and over time, the decks on every one of our boats either delaminated at the stay attach points or separated from the hull. We seemed to be constantly repairing them. Those compression forces may not break things right away, but could show up later, potentially at a disastrous moment.

I do think there's likely a tension or a mounting point on the mast that will allow some give when things are about to break. I'll give it a try.