Matt, am I reading that right? 75mm for the cord on a rudder?
2 15/16"? With your example of 10% that would make the rudder 5/16" at its thickest point...That seems insane...how do you make anything with those dimensions stiff/strong enough to function at all irregardless of keeping laminar flow?

what, you mean these things aren't just thrown together from parts that are sitting around?

Pete same problem. The f18 Shockwave uses extended pintles maybe cheaper than new rudders, you would only need the arms to be lengthened then

Looks like one way to solve a little of the "over steer" problem....especially on an existing boat...but how does that sit with the rules? And if what you have pictured is class legal...how much farther can you carry the pintles aft before the rules have been broken?

Curious to how much smoother the steering can be enhanced before it is considered an extension of the hull, and is included in the overall length.

My PERSONAL understanding of the rules is that rudder gantries are legal provided that they do not add bouyancy or waterline length. Therefore they must be solid, heavier than water or open vented tubing that cannot float.
The overall length of an F16 hull excludes rudder fittings.

Wayne, couple of questions...
1) Did you ever sail that boat with the rudder attached directly to the transom without the stand off pintels? If so what percentage improvement did you feel it achieved by moving the rudders back?

2) What's the motivation for mounting the rear beam so close to the transom?

Thanks for sharing your insight...

Regards,
Bob

It was to overcome a problem the F16's had started to get into design wise. We all have started moving the front beam back further in the boat like the A's basically to get the upwind Uni sail working better ( the uni sailor is not allowed to have a jib ) and bringing the Spinnaker COE back further into the boat to prevent pitch poling ( it does seem to do that ). Bitsa has got to the point in that despite quite fine bows, it will side slip rather than dig the nose in even when provoced to try and make it so. A part of that also is my belief that as an Uni sailor we are over square at 2.5m beam so reduced it to more the A's of 2.3m

The problem lies with the box rules in that we have only a 8.5 m mast height allowed which then makes the sail much lower aspect than the A's and creates a much longer foot. That means then that the rear travellor has to be much further back than an A, so the beam has to go back further in the boat which then immediately flags up the short fulcrum arms. The 150mm gantry is a waste of time as far as leverage goes, it was just a method of getting the arms longer.

There is an alternative to the arms we use and I wish I had used that method, Have a look at the C class boats, they use a much better, far less vulnerable to accident damage ( crew falling into the cross arm )and probably a lot lighter system. Knowing now the problems caused by the extra leverage of the gantry, I wouldn't do the same again particularly as we cannot fair the lower gantry in to make it more streamlined as per the box rules.

Bitsa as we speak is in the workshop getting this mod done ready for next season, it has a load of benefits, moving the tiller mount point 400mm inside the rear beam and giving central sheeting. The downside is I will have two short tiller sticks rather than the more traditional long stick.

I know I will regret asking this, but here goes anyhow: Why did you reduce the beam by 20cm?

The hull bouyancy is marginal for the 15m main, yes I can get my lardy 95 kilos out on the wire to compensate but all that will do is sink the hull further creating wetted area and drag which means slow. So much better to reduce sail area and let the hull ride in its optimum level.

Certainly proven with my current boat, having gone from 13.5m sail to 15m sail and then from 2.3m wide to 2.5m wide, I think the smaller sailed narrower boat was faster other than in light conditions.

But Mecca I'm sure you will tell me that I am so wrong

I won't tell you that you are wrong, but I'm sure plenty of people who design multihulls for a living will...

But hey, if it's working for you... Keep on trucking!

Corrr that has to be a first

Slightly narrower beam seems to work for A cats.

And do you think the A cat would be faster or slower if it was wider??

I think it depends on the wind. We all want to sail on one hull as much as possible, for reduced drag. A narrower boat will fly a hull sooner, with less righting moment, so in light air, that's what you want. But when the wind comes up, now you need more righting moment, so the same hulls, crew, etc. should go faster with a wider platform (more righting moment), right?

I don't know. Why don't you ask Pete Melvin?

I'm guessing you'd have to beef up the beams to make it wider. The wider platform would be less stiff and I've no idea how to correct that. The narrower beam would be easier to sail, "things" would be an inch or two closer and easier to reach.

So, I'd conclude the narrower beam would be one of many compromises.

If you can get Melvin to address the issue, I'd be greatful.

Pete and Gino have a bit on at the moment, and to ask them that question would be like asking Enzo Ferrari if he thinks more horsepower is a good thing...

I'll leave you guys to this little discussion, you seem to have entered the 4th dimension...

Macca,you make no sense. The analogy between horsepower and beam is dubious at best. In cars the problem has always been getting power to the road. That requires matching engine and chassis. As power increases, chassis are redesigned to accommodate the increase.

The assumption here is that Pete Melvin is at the top of his field and his designs are among the best.

IF: wider beam are always better

Then: Pete Melvin desgins should always have wide beams.

Since the conclusion is demonstrably false, so is the premise.

FWIW, Ferrari doesn't know everything. Their cars don't win all races or sell to all upscale buyers. Iirc, Ferrari was one of the last builders to switch from drum to disc brakes.

OK then, which is fastest upwind a DNA A class or the latest all singing and dancing 10ft wide Melvin designed F20C. My money would have to say more times than not the A class.

Ah now I quote from the DNA's own website "This weekend PJ sailed in Hellevoetsluis in force 5-6 in such a set-up (increased mastrake, striff battens) and he could easily beat a Nacra 20 carbon and the F18's upwind by saling both higher and faster (downwind the Nacra was a rocket).

Now if everything can be believed from the internet

Ok, how about we do a lineup? You guys bring an A class and I bring the F20.....

You shouldn't believe everything you read on the web...

You think Ashby would show?