Why I'm Following Sven Yrvind

History has also proven that learning and improvement come from understanding and respecting existing designs and learning from them and what the way they work teaches us about the forced involved. I've been lucky enough to talk to many great designers and perhaps the biggest characteristic they share is their deep understanding and respect of earlier designs, and (in some types of craft) their own ability to sail fast. What none of the top designers ever do is assume that the best current designs are terribly wrong, because that's rarely, if ever, true. They are like Einstein, Newton and the Wright Brothers - they deeply respect earlier experts and learn from their knowledge rather than assuming that they were dorks. Top designers don't think that earlier craft are perfect, but they do respect them and learn from them. They study other craft and the thinking behind them in great detail and with general respect, just as Einstein, Newton and the Wrights did.

As AII says, tumblehome is the hull sloping inwards. It increases the angle of the chine in your design. Highly abrupt and angled chines in a bow section tend to lead to major control issues at higher speed, and major turbulence/drag issues at lower speeds. That's why windsurfer shapers, for example, spend so much time on rail (chine) tuck and apex.

An immersed stern is extremely draggy at low to medium speeds. Given that a heavy boat around 10ft long is inherently slow, reducing low speed drag is important.

Sailrocket remains pretty much the only successful inclined-rig craft, and that is arguably largely because it sails in extremely strong winds down a straight line in one direction. Windsurfers don't really try to incline their rig for speed - it's just that leaning their body, and therefore the rig, to windward is the way they develop stability. Look at this pic of Matteo Camboni, one of the world's best Olympic windsurfers - he's hanging onto the uphaul rope rather than the boom with his front hand so that the rig is as upright as possible, rather than leaned to windward.

https://media.gettyimages.com/photo...class-on-marina-picture-id587767114?s=612x612

The whole issue of windward rake in board rigs is complex and interesting, and there's certainly little if any evidence that windward rake normally helps overall. Also note how Matteo is tilting the board, which is contrary to simple planing theory. The fact that he has both board and rig at different angles to that which some theories suggest show how much we can learn from looking at what experts do, rather than assuming the tens of thousands of hours they have spent developing their craft are wrong and that we can sit back and do better.

 

Here's the last bit (?s=612x612) of the Mattia Camboni windsurfing picture URL cut off for a bigger version, he's holding the uphaul rope with his front hand while hanging onto the trapeze while holding the rig is as upright as possible, here's some more Mattia Camboni pics at the same source.
— P.S. —
Here's a picture of Giorgia Speciale holding the uphaul rope similar with her front hand while hanging onto the trapeze while holding the rig is as upright as possible.

 

I feel the same way. Not being a naval architect, I haven't studied and become knowledgeable of many designs. I am only familiar with the ones I've sailed and read about, and only to the extent of a very casual layman. I have a great deal of respect for the work and thinking that designers have put into their boats. The one I knew the best was indeed an impressive man whom I respected tremendously. I can confidently say his influence has helped shape who I am. That is not to say I learned anything about boat design from him. I just knew him as a family friend.

My ideas, if they are non-traditional, are mostly out of ignorance and a sense of personal aesthetics blended with a logic that has no meaningful premise upon which to base it. It is, however what I have, no more, no less. If they work, cool, if not, that is too be expected. I am unlikely to actually build a tiny boat with which to cross an ocean in. I am an artist, a cabinetmaker and a small homestead farmer.

While I don't take your critiques too closely to heart, I can't help but read a chastisement in your words. I have not meant to suggest that past designers are dorks. I certainly don't think Sven is a dork, nor is he wrong in his approach to his designs. His boats are not how I would do it, that is all. As I have said before, he is out there upon the sea while I am not. Bravo for him. I am following Sven because he has something to say that I have ears to listen for.

I hope I can also listen to what you have to say. I'm sure your points about my design failures will lead me to a better understanding. I am listening. Thank you.

-Will (Dragonfly)

 

Regarding rolling the boat: I guess there is a statistic on this somewhere, but I was unable to find one. The thing is, I believe that Sven is tackling a rather non-existent problem when he so adamantly is pursuing super high stability. The form and CG of his boat are such, that they cannot remain inverted, and even getting there is rather difficult. The initial stability is not that good with a narrow boat, but in the scenario of getting rolled they are safe, I'll give him that.

But: considering cruising, leisure and even hard core travelling (I would put Sven's boats in the latter category, as sailing in them would hardly be considered a pleasure by most ) capsizing and remaining inverted is very very rare. I do not think we should look at racing yachts (or boats) in this context as they are completely different animals. For Sven to refer to them in his manifesto is a fallacy at best. I do not recall who it was, but one of the great racing yact designers once said that if something never breaks on a [racing] boat, it is too heavy. Obviously this extends to keels also.

So, I think Sven has a point in his pursue for stability, or roll safety, rather. I also think he overdid it, and definitely hope he ditches the idea of an articulating keel he posted here: PREPARATIONS AND PLANS https://www.yrvind.com/preparations-and-plans/ unnecessary complexity with little gains. Instead I wish he would take a step back and continue with the chinerunner idea from Matt Layden: MATT LAYDENS CHINERUNNERS BASED ON SWAMP THING, PARADOX & ENIGMA, ETC. https://www.yrvind.com/matt-laydens-chinerunners-based-on-swamp-thing-paradox-enigma-etc/. He could use the brass keel plate idea he has on Exlex Minor, but extend the plate over the bottom sides of the boat and bend the overhangs downwards maybe 30 degrees.

 

Not a "boat design" topic perhaps, but now Sven is approaching the Azores for real, and it looks like he'll have fairly favourable wind directions for the next 4-5 days.. I hope he makes it. If not, it could be a long loop to get back . (And perhaps he doesn't mind doing that either for a few more weeks.. ).

 

At the current winds he might as well sail to the Caribbean.

 

Oh I bet he's itching badly to start the building of the next Exlex, so Azores will be the end of the line for Exlex Minor.

 

And he would be very foolish if he decided to cross the Atlantic now, in the middle of the hurricane season.

 

I doubt there's statistics about it, just like about how many cars actually roll over, nevertheless the moose test made the 1997 Mercedes A-Class adding electronic stability control, and modifying the suspension, which now has become common on most cars.

 

Looking at the current winds I was thinking in post #201 he might miss the Azores, as he has to sail upwind for that now.

 

Depends highly on how many sailors have insurance. Insurancing is a business run purely on statistics.

And: there surely is a statistic of boat capsizings leading to deaths / serious injuries, as these would involve use of public services.

 

Styrbord Sven, styrbord!

Oh blimey, he's gonna overshoot Horta...

 

He's definitely trying . . .

Sven Yrvind ExLex II tracker screenshot on Sept. 4, 2020, at the posting time of this message, at 68 days + 19 hours in the trip from Ålesund, Norway.

 

At 2020-09-04T21:30:42Z (ISO8601):



Certainly not looking good. He's got food though, so no problem I guess...

 

He may make New Zealand whether he wants to or not.

I'm rooting for you Sven .

-Will (Dragonfly)