MartinRF

Using open source programs you mean? I think that could be done using Freecad and maybe Z88 Aurora or Elmer or the tools collected in CEALinux. I will try that some day but for now I am lazy and use tools I am used to from work. /Martin

So I couldn't help myself and started modelling the board-hull interaction: Very much work in progress and I can't guarantee the usefullness of the results but the idea is to load it up with some of those finite elephants and hopefully understand better where stresses go. /Martin

No sole in my boat. None specified and my boat is small with some 1.3 m head room so adding a sole would not really add to comfort. I see Tennant stuck to the same design we rejected back in 1985. There were a number of things we change in the structural engineering. The only things that have broken are things we did not change such as the cross beams. Yes, the sole helps distribute the load but only from one side unless you wrap fibres around the dagger board case and spread them onto the sole. Are you in a hurry? If not, why not spend some time on a bit of proper engineering befo

Four layers of glass? What kind of glass and why? Here is what we did 30 years ago instead of following Tennant's instructions. This has worked but I (now) understand there are even better ways of reinforcing this area of the hulls. Some years ago there was a very long thread on the renovation of a tri called Timberwolf. Unfortunately all photos are missing now. Having longer boards with the upper support further up in the dagger board case also helps -- less crow-bar like. My dagger boards reach deck even when fully down. /Martin

Underengineered and underbuilt foils are far too common. There is some information on this here. I have enclosed a section that works real well. You can scale thickness a bit to fit your dagger board case. The first coordinate is cord and starts at the trailing edge (1) with zero at the leading edge. Recommended for rudders too. /Martin prulsY.txt

I am envious, I want to emigrate. /Martin

This four year old video demonstrates what impact on sail shape down-haul-induced mast bend can have. /Martin (envious, I don't have this level of shape control)

Both boards are fully down throughout this video. That was not perceived as a problem by the helm. When the biggest gusts hit he was not totally happy with rudder response (he is a former Swedish A-cat champion sailing Marström boats -- very skilled but a bit spoilt when it comes to build quality). Afterwards I calculated bow-down and forward tilt and figured that during maximum acceleration even the lee rudder operated almost totally in the wake of the hull: the lowest point of the hull being almost as deep as the tip of the rudder. Hence the plans for new rudder blades. Note that

Yes, bending and tosional stiffness are important, especially if the blades are raked forward: Bending will induce angle-of-attack increasing twist... /Martin

OK, here is what I think may be going on after having looked at the video above. I see you use the same 'geometry trick' I do for balancing transom hung dagger-board rudders. There is really only one mostly aestetic difference: In my case the rudder blade is vertical and the rudder axle is raked. Watch the attached drawing: The left part shows the original design from Tennant. The right-hand side shows what I have had since 25 years or so. I have reduced the distance between the centre of effort and the rudder axle. Your geometry does the exact same thing. The right-hand side also sho

I was spending time at the other end of the speed spectrum today -- had problems reaching five knots. This was possibly the last sail of this season. The temperature had dropped to 3 C when I got back to my apartment. Very nice, calm and quiet as I was all but alone on the water. Tiller gets very light above 18 knots? That's odd I think. Do you know what wing section is used for the rudders? Are they balanced in any way? /Martin

> The failure mode seems to be in the details, such as around reef patches. > This is where the original sail maker shows his worth, as the sail nears the > end of its life. Which is why I mourn the fact that the sailmaker of my last two main sails has closed shop. I had hoped to place an order with him for a new jib... > Sure on dacron Tornado and PT mainsails we used lots and lots of luff tension > to bend the mast, open the leach and move the draft forward. But I'm not > convinced it it effective on bigger boats with radial sails. It is an important tool i

When Kevlar sails were a new thing back in the 1980s I was told they held their shape until they disintegrated. I was not in the echonomical position to test this. Now I have an almost ten year old jib built from a carbon/Kevlar laminate from Contender called Maxx. The material still looks very solid apart from the window which isn't very transparent. Still, ogling the shape in lighter wind I see the draft is not as far forward as it used to be and the leech is hooking. If the wind is up and its sheeted and tuned flat it looks fairly good. (Disclaimer, when the wind is up I don't have

My jib sheet is routed 'on top' from cockpit to cockpit via the jib clew: Forward from the winch to a cheek block on the main beam, then along the top of the beam to a block on the traveler, through a block attached to the clew and down to another block on the traveler etc. The line I am giving a tug in that video is the barberhauler. That one is routed under the trampolines. I need to give it a tug as the traveler track of the jib is straight and the jib is only semi-self-tacking. Simplisticy over function? /Martin PS Nice photo paxfish.

See, Paxfish, I am not the only one doing my own hardware. /Martin (Looks like sail I could have a lot of fun with on my boat.)

I think length = size is a mistake. Sundreamer was, if memroy serves, designed as a very long fortyfooter: Width and sailplan as if she was 12 m long but with 18 m long hulls. ORMA 60s were designed to a rule which limited length, width and rig height but not much else. They were designed for pro sailors and money was not an issue until it became such a big issue it killed the class. Designing them became a desperate pursuit of longitudinal stability, according to Nigel Irens. All information I have indicate the MOD 70 trimarans are much better boats and in most cases actually fast

No. /Martin

Me on Ackermann: http://hem.bredband.net/b262106/Boat/acker.html /Martin

Been there done that twice. Once because of stupid underbuild and second time because I hit a rock. That time I missed a race but the boat was back in working order within a week. By the looks of it I don't think you hit something. I think this is a case of too weak. Remove damaged laminate (angle grinder and 40 grit 'paper' comes to mind). Rebuild and make it strong enough. You need a 'bandage' of fibres holding it together between the pin and the sleeve. Idealy you should have fibres forming a figure '8' with the rudder sleeve in one loop and the bolt (pin) in the other loop + fi

Their store locator does not feature Scandinavia or even Europe. I have been told covered lorries are painted using 2-pot polyurethanes like the ones we are used to and you can get any colour you fancy. I will investigate this. /Martin

Easier said than done since that yellow colour is not part of either International's or Hempel's offering any longer. I have some ideas on where and how to get it but some investigation effort is needed. /Martin

Lessons learned: Longboarding isn't quite as intimidating as I thought, but it is a good thing to be patient and not try to do it all in one go. From an Altex video I learned about applying tracer paint onto the undercoat before sanding. This really helped. Keeping the mixed and thinned (20--25% thinner) paint in a bottle and squirting paint into the roller tray as needed to wet the roller ensured consistent viscosity throughout the application. Don't count on weather being cooperative /Martin

Final result photo from about a boat length away. /Martin

I have had really good battens from day one but the first set of sails were undebuilt dacron sails (1986, remember?) and good battens can not save bad sails We found another sailmaker, one who knew what he was doing, who re-cut the main and reinforced its leach and we ended up with a useful if not good sail. /Martin

Perfection was not the goal and I don't like adding weight to my boat so I added almost no filler -- less than 100 g for sure. I sanded until reaching high spots of the laminate and did not fill in lows. I then undid some of the longboarding as I removed the 60 grit paper scratches by machine sanding with finer paper: exposed filler sanded quicker than old paint. Still fairer than before. /Martin