Sport Tandem with Mk 3 Sailrig update and query ref. skegs on outriggers?

Builder's Forum
1

Hi All,

We have completed the first part of moving the mast back to get better balance with the boat.

Here is a short walk around before we took it out for testing on Saturday:
https://youtu.be/_YTy4RlQBg8

Huge weather helm obviously as it is set up now, but the power is better balanced longitudinally, not driving the bow down so much which is what I was after.

I am now going to put on a temporary spar between the trampoline decks so we can find the perfect position for the leeboard.

One other issue with the leeboard is the added complexity of it - the putting on and taking off and the pressure on the brackets and the board itself.

If keeping it I will need to beef up the brackets and board considerably as they bend a lot and I think will fail sooner rather than later as we have quite a lot of power with the RS200 jib as well.

As an alternative I might investigate putting long, shallow skegs on the bottom of the ama's - I will try and rig up some test skegs and if it works go that route.

Any thoughts on issues of using skegs as per the Warren Light Craft approach:

http://www.warrenlightcraft.com/kayaksailboats.html

Where we sail has loads of shallows and the leeboard and rudder are both on bungees to flip up out of the way - shallow skegs I think will be less efficent but essentially a lot simpler.

If I can work out the right position I could then cut through the bottom of the outrigger to insert the skegs and bond them into the decks to make them nice and strong.

Any thoughts or experience from anyone here on this?

Hopefully get some good sailing/paddling video soon if the weather improves.

2

  Neat project. It's fun to see these projects that go beyond the safe parameters of the catalogue. I haven't put a sail on a kayak (yet), but some general sailing observations are:

-the forward, side stays are redundant and only increase mast compression and decrease forestay tension

-the clc leeboard is a head scratcher. I love the idea of skegs or even pivoting centerboards in each float. Toe them in ~2 degrees and give them a slightly asymmetric profile, even. Don't go too crazy and make them too deep- I doubt the float/beam connection really wants a lot of torque from a deep foil.

-with all the strings, wouldn't a foot controlled rudder make sense? -You're not sitting on those tarp tramps are you? That would be a lot of RM and could increase rig loads way beyond what a kayak backbone can endure. And the style police in me has to mention that the 2x4's clash with your nicely built kayak!

-you mention the bow going under. After doing what you can to move weight aft, I wonder what effect adding some lifting strakes to the bow would have?

3

   Hi,

Thanks for the comments.

The stays are not under any tension initially they are there to prevent excessive bend in the mast. It is as specified but bends like crazy in anything other than light winds and loses shape horrifically.

I added more attachemnt points to the mast to help the shape but the mast bend was still maddening.

The boat flies - there is a video here of the very first test sail we did:

test sail

which shows some useful bits and pieces. Around 50 seconds we pass a moored boat and it gives an indication of the speed but prior to that you can see how the floats are submerging completely and the water is hitting the vertical brackets giving a lot of drag. I am planning to fair these in to reduce this as much as possible. Now with more righting moment the boat is way faster.

This also then shows how close the aka's are to the water as it heels over. The idea for the tramps then is that we can shift weight around easily so my wife now sits out and we really move along. Another plan is to redo the cross beams into a single flare up and out so they are higher above the water - but leave the floats at the same height they are now.

Once that is done i will make the attachments points for the tramps - the crappy frames are just the test bed while we see exactly what works - and they will be discarded and join the burn pile....

In the video we were testing various differnt cut down windsurfer and sails and positions - we have run it with twin masts but if you look around 7:52 in the video you can see an indication of the mast bend - close up my friend up front was crapping himself.

At that point we couldn't tack it easily either and had to paddle through turns, but the jib makes a huge difference and getting the balance better will improve it further and make life easy.

There is another video here when we couldn't get the jib up it was so windy

no jib

and a very low wind potter here

low wind potter

which show ballast hopping about for balance but also shows when the mast was further forward and the stays were connected by a linking line to both cross beams to spread the load.

With moving the mast backwards the stays can only really spread the load across the rear stays hece adding the foestays to spread the lateral load of the mast between both crossbeams.

It is great trying different things, i will be making a tiller extension so i can sail it single handed from the tramps.

I do have a foot operated rudder for use when we are paddling - but I swap it out for a much shorter and small chord rudder as the stock rudder is way overpowered and gives too much drag.

When sailing the standard rudder is in fact a bit underpowered so I am looking to probably upgrade that slightly, just making it a bit deeper to give us more turning power - at nearly 22 ft long and some pretty significant power with the jib - we need a bit of oomph for turning.

The foot pedals simply can't generate the power for use with the sailing rudder so the tiller is quite good as it is attached with a tight bungee so I "lock" it in position. I also use it paddling sometimes as you can point it, lock it and just get on with the paddling. That  is great as you can concentrate on jsut generating power and really thrash it. With the two of us paddling we can go through most sailboats and a lot of boats under power as well which people are amazed at.

I have reinforced a lot of it for the extreme loads we put on it and it is also really quick under sail - we go past most small boats and are often out in conditions when everyone else has gone in or not even gone out.....

It is really great fun and all the changes have sparked my interest hugely.

So now I am currently starting to build my own design of sailing trimaran (while still modding this) which has a central skiff huff and large outriggers using an ISO dinghy rig which will be seriously mad. I will be grafting on home made surface piercing hydrofoils once completed for extra life threatening insanity....

4

I've moved the mast and leeboard back 18 inches now and given it a test in light winds with some video here:

Light wind testing

The imporvement is massive: turning quicker and lighter and tacking is nice and predictable.

It is now situated jsut in front of the front cockpit giving more bow volume up front and feels great.

Going away for a while but when back will hopefully get it out and ride over to the Isle of Wight to give it a proper test.

I'll remake the crossbeams making them flare up much more from the centre then  drop down just at the outer ends to give more clearance to the water and also integrate the trampolines directly into them - removing the quality 2 x 4 used for testing.

I will also smooth in the upright brackets on the ama's as well so when they submerge / hit a wave the water can flow around and not scrub off so much speed.

5

Have you done anything to prevent water from entering the hull around the mast?

6

Hi,

This was something I was concerned about but actually no. Out for a couple of hours at a tme in some chellengng conditions sometimes I might get half a cup of water get in.

I do things a bit different;y - I have a separate sturdy aluminium tube that passes through the deck into the mast footer (remains there permanently) and the mast drops into this. The reasoning was the diameter of the short fixed pipe is significantly more spreading the load against the thin deck (reinforced of course but still thin) and it is an almost perfect fit in the deck and footer. It hasn't been glassed in place yet as I have been trying differrent positions. Any movement of the mast is them ally on ally not ally against the wooden deck.

Now we are happy with the position I will fix the short piece with some epoxy and fg tape and also make a small boot to fit around that short piece and the mast itself. It will be sealed and fixed at the top and held permanently on the mast and so will just drop over to keep any water off the small open space between the ally and can rotate with the mast.

My biggest concern now is closing the front cockpit with some support so the ballast can scamper about and put weight on it as they transfer from side to side. Currently water can pour in there when it splashes up. I have a cover but need to make some frame to sit on the hull up to cockpit height that can be easily dropped in and out and hopefully collapsible to not take up lots of space when moving things.

Plan is to make it slot togther system - a simply flat top to fit inside the top of the cockpit and 4 vertical crossed panels that slot together and into the top from underneath and then the neoprene blanking cover simply goes around the cockpit as normal.

Once I get time I will sort and post some pics.