Nemesis

Seems you wait years for an Unarigged singlehander, then 3 come along at once!

Hi Toby ...

Not sure if I sent you this one in the Summer...  Can you guess what it might become yet ?  (I think you can)   Don't get too excited  - It is just a bit of a diversion for me through the winter to try a few new ideas but you are welcome to have a look... its very very light though ... (the one in the foreground that is !)

 Mike L




Edited by blaze720 - 31 Oct 13 at 4:06pm

As I recall when they were developing the Hurricane Catamaran they wanted to minimise the nose diving tendency of its cousin the Tornado. They looked at big fat ugly bows like they had on the C class Ocelot but settled on making the back end narrower. Evidently there was too much lift from the more buoyant stern of the Tornado which pushed the bow down at high speed. Reducing the buoyancy and consequently the lift generated in the Hurricane made for a boat less prone to diving. Apparently.   

The whole essence of why that V twin was the shape it was (a bit ugly some would say) was to prevent nose dives, which conventional Cat lee hulls are prone to. I spent ages considering the issue, how far forward should the mast be, how long should the boat be to counter the levering effect of the rig forward.

Going down the mine is the product not just of the rig forces, it's the rocker of the boat, the wave length in relation to the boat length (and that rocker), the resistance of the nose volume and the shape of the nose and of course wether or not you're designing a planing encounter or a displacement entry into the back of the wave.

Wave speed and length also effects it, slow short waves imv are more of a problem than fast long waves and since for the most part the sequence is, nose buries craft slows, next wave lifts stern further. If the wave speed is fast you have more chance of popping back up than if it's slow and short frequency.

Our water is probably worse than most as the waves generally are slower than the craft riding them when conditions are such that nasty mining is likely to occur, so boats under 14 ft in length have more of a problem than 15 and over, it's just the way of it, hence Contenders doing OK. But, it's not just the length, the rocker plays a part, there's something about the Blaze rocker for instance that brings more nose related issues than say the Contender.

The next incarnation of my beast which should the Gods ever put me in a position to foist upon the world, is due to approach the problem in a similar but slightly different way that I went about it before, with the plan of introducing more area only when the wave is encountered or excess heel in up wind work, difficult to describe it, wish I had Peaky and Dans computer rendering skills (or a programme that works on a mac).

I find these threads fascinating and really informative and really hope the Nemesis sees the light of day, it's great to see British inventiveness is still alive and well.

Back in the early 90's we usd to see the technical presentations on the Twintex and it all looked terriffic. We were in marine composites using conventional thermosets and it really got us quite worried. We would hear about customer X trialling it for a project and then it would go all quiet and no one ever got it into full scale production of marine mouldings. The technical gossip around at the time was that getting the stability into the tooling was difficult ( I am sure that things have moved a bit on this since then but it still is not simple). Also there was horriffic " print" and sink marks on the laminate. Oh and you couldnt paint it to sort it outcosmetically. So all in all the mouldings probably looked pretty grim. Not the sort of thing that we expect for the hull of our racing dinghy