Friday, May 1, 2009

Karma, Whats working and whats not.

Karma has been sailed a few times and is now staying in one piece so I have had time to reflect on what has worked and what maybe needs some redesign or reconsideration. There are so many things on this boat which are diferent to most modern moths its worth considering some components separately, even if many are intendended to function as a complete package. I am not a follower in design terms and the freedom to experiment a bit off to left field is one of the reasons I am interested in this class.
So the list:
Hull: The freeboard is lower than any other modern skiff. The bow height is a little less than Bladerider and the stern is a lot less. But it works. There is enough volume to float everything, and because the aft wing has been brought forward, there is still heaps of volune aft. No Hobiecat like stern overs likely. The Hungry Tiger shape proved one of the best in the light over Easter, so performance when the hul is in the water should be up to standerd. Its light too.Tick.
Elevated wings and tramp. Not new, seen on Greg K's boat at 2000 WC, plus Sideshow Bob, Fuzzy Logic, Chainsaw and of course all the 14ft qnd 16ft Hobiecats. Its very comfortable in the light, but needs some foot holds which I have done with half pool noodles in pockets. I have not felt discouraged even when a lot of other things were not going well. The wing spacing is only 1.65m so its reduced the windage of the wings, tramp and the hull/tramp interface is not even there. I broke the first set of elevating struts, and build a better set, adding only a little weight. The boat is remarkable smooth and quiet when flying, which must in part be due to the windage reduction. Tick
Tapered foil tops. Also on B2 but I did not copy, see photos here late last year. This is a great idea, BR owners would miss their rubber mallet, the foils go in so simply, lock in place and need only a small pin to prevent them falling out. The fin and rudder box are smaller and lighter and the verticals will be too when I make some better ones. Tick.
Reversed Bellcrank and tesnion wand linkage. Marty Johnston had this first, but I have simplified it as best I can. The bellcrank is on the hull aft of the fin. So tesion in the wand linkage pushes the flap down. The bungee pulls the bellcrank back directly which also pulls the flap up and the wand down. The linkage between wand and bellcrank is a 1mm spectra kite string. Light, simple, flexible. It has taken me a lot of trimming to work out settings and where the adjustment needed to be. It now has a model yacht rigging screw in the linkage for fine trim. Bungee tension is adjustable via a contol line and needed to be increased as trimming processed. Happy so far. I have to get it right as the top of the fin and case is too small to insert a regular bellcrank anyway. Maybe a smaller tick for this one.
Removable Tees. I have had the rudder foil removable since last year, sailed the nationals with one and seem to have got it sorted. But the main foil Tee is another matter. I have rebuilt it a few times but for now I have given up and glued it together with a much more substantial molded Tee. Its seems very hard to get a decenet size T section and a strong enough receiveing case inside the small vertical section. I will have another go later after I sort out a few more issues and get the boat completing races on pace. Cross.
Aft mainsheet. Becaue there is no deck to mount a central sheeting system and the front wing is too close to the mast, the aft wing is the only place left. Not new, Lea Sitja, Charlie Mckee, and Martin Cross all use it. I just took a while to sort it out. Purchase, ratchet block location, sheet length all played with, but coming good. I do know that when its wrong its aweful. I have to get it sorted, no tick just yet.
Tiny Gantry. The pundits all said it was flimsey. Its a little shorter than the max 500mm at 350mm because the transom is so small I could not get decent angles at full length. Its made from 10mm tube pultrusions and weighs 260g. I have had some big crashes in the first few weeks and no signs of cracks or groans so far. Still a tentative tick.
Layout. Compared to Hungry Tiger the mast is forward 100mm at 900, and the fincase is forward 200mm which is also why I could shorten the gantry and maintain appropriate foil spacing. Although I have yet to be happy with the rig/sail combo, I think the helm is right. Neutral when healed to windward but still not excessive weather helm when low riding. All good, Tick.
Now the really big one: Unstayed rig. The mast is max length and made from a CST M354 40mm spar with some 50 and 55mm sleaves from the base almost up to the spreaders. It is strong enough to stay up without any rigging, but is too soft. I have also sailed it with either: 3 stays with spreaders, forward raked diamonds, and with the diamonds plus a forestay. In none of these configurations can I get the mast to match the luff curve of the KA MSL13 which I bought for the boat and to use on the old boat at the Nationals. Also because the mast is stepped quite upright with little rake, plus max length, the sail is set very high.
So I need either a new sail made for the present mast in one of the three configurations listed, or I need a new mast to rig more conventionally to match the KA sail. Since I just sold a boat I might splash out and do both. The stayed KA rig would allow me to sort out what esle works well and what does not, and also be the right stuff when there is good winds. The unstayed mast with a new sail could be much higher aspect ratio as the leach could easilly be a half metre longer, and that combined with the ability to square the rig would be a big advantage in light winds, especially for a heavyweight skipper.
So another tentative Tick with a lot more development to come.

Overall I am happy with progress so far. More ticks than crosses! The boat is very light, maybe close to a M2 or VRX but at only 1/4 the cost so far. Its noticable most when carrying it out on its side to deep water. Balance point is the (high) boom, rather than the toestraps as on the old boat.

Working on two rigs will delay my other plans which was to be a full solid wing rig. This was one incentive for the unstayed configuration of the whole boat. We will see what time is left this year.

The fact the boat is far from fully developped and reliable means that I will not be going to the Gorge as I had once planned. But Perth in January seems a good alternative and I hope to have it racing well by then.

On the list of new stuff are new foils, new tampoline to replace my amateur sewing, plus sail and mast. I have a new main foil under way, and will make a new small aft foil based on Andrew's new one. A new mold for the vericals is needed, slight reduction in width like the M2 plus a better section. Plug carving first. Soon.

And of course I need to learn to sail it fast, practice? Not over winter, I feel the cold too much at my age.