Yrvind

Hi Manie,

It's the same flat bottom advantage as I tried to tell in post #612 on your build thread.

‘‘ .... one of the advantages of a centerboard is you can pull it up in a gale to be able to be pushed aside by the seas rather than trip over the board/keel which causes the knock downs when the sails are down .... ’’

Maurice Griffiths explained it much better than me in his book Swatchways and Little Ships.



If someone has the English version of the book please post a scan of Chapter 16, Bilge keels and centreboards, centerboard advantages, point 7 and 8, advantages of the centerboard up in a storm.

I only have the Dutch version of the book, so I only can post a scan for the Dutch and Afrikaans readers here ...

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Same thing goes for Sven's flat bottomed boat.

Sven is doing well , I like the balance lug yawl rig of the model

Cheers,
Angel

 

Hi Sven,

Maybe you can save some on the 100 kg of books if there are books of your liking available as E-books, the E-reader, which can hold enough books for a year reading I guess, could be charged with your hand and foot powered alternator I think.

Paper books are less sensitive to malfunction, though.

Just some thoughts in case you read here or someone will pass this on

Good luck !
Angel

 

Great Video of Sven in his shop with the boat and the little model...thanks for posting...I love rowing my little 7-foot dinghy and nestling between waves...riding up and over them...rollers it get alot harder to do this...hence the reason he will have alot of weight I presume...to hold position...and I can see how that bow-shape will help diffuse wave energy from steady short-period rollers and help him ride up and over them instead of through 'em...but those are found mostly nearshore....offshore he can slide over and between the steep short-period rollers but it's of course gonna be long,grueling and slow in areas....but I think he makes it..I wouldn't ever bet against this guy...he's still in good health it appears..and the mind is sharp! Probably not 5 people on the planet who know the pelagic AND coastal scene for the small boat the way he does...

 

New post on his blog May1st, about shaping the hull and testing the scale model: http://www.yrvind.com/present_project/

He wrote something I liked; "We human beings are the only animals being bored except wild animals in captivity."

Thing is, if I take a spin on that.. -Most of us human beings are in fact wild animals in captivity.. And all this.. building boats, sailing, kayaking, etc.. It's about breaking free..

 

I like it all so far except the twin rudders system without a centreboard or lee board.
The twin rudders on a small boat will have liitle effect on yawing and leeway.
Good down wind steering but little lateral resistance.
I would suggest a sliding daggerboard off the bow - a system that he has used many times before that has a proven record of success.

Anyway GO SVEN GO
looking better every day
bon voyage

 

Bow dagger ?

This will be a boat for the roaring forties and furious fifties to do a lot of down wind sailing there, hence the extra side by side mast steps forward of the hatch, I'll guess that will be on each side of the cabin top. Changing of the masts positons and re-stepping them will need nice weather but the sea will never be flat, so I'm wondering about that . . ? ?


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The long twin rudders in / \ position will dampen the rolling of that small boat, but like Manie I think lateral resistance from the rudders will be low as their suface is all behind the boat and they only will provide lee helm if going anything else than down wind.

On Sven's course winds and storms will be down wind to the east, so his only lee shore will be Chili's west coast when he approaches Cape Horn. But to not end up on land there and be master of his course he'll need some more lateral resistance than provided by the rounded multi chine bilges and flat bottom. So a bowboard might be a good idea.

Yrvind Ten hull + waterline.
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Below pics of the skipped bowdagger of Yrvind.com and a bowdagger haul sketch for Yrvind Ten...


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Maybe Sven can use the skipped bowboard from Yrvind.com. I've made a sketch to overcome the sliding problems which caused the skipping of the bowboard on Yrvind.com. In the sketch the bowboard's up and down hauling and locking is operated from the hatch with haul lines to which some blocks can be added.

Info about the planned, made and skipped bowboard of Yrvind.com can be found at . . . . .

- October 7, 2008 - (bottom post of the link) - RUDDER & BOWBOARD

- December 20, 2008 - GOOSENECKS & OTHER FITTINGS

- June 14, 2009 - ON THE IMPORTANCE OF BOWBOARDS

- December 1, 2009 - (bottom post of the link) - THREE STEPS BACK AND A NEW THEORY FORWARD


Btw, any of our Swedish friends going to Sven's laminating party . . ? ?

Good luck to Sven

Cheers,
Angel

 

A pic shows the only lee shore and down wind situation best, blue is 60°S, next one drawn north is 30°S, winds and storms are most westerly blowing Sven east, Sven will be north of Antarctica and south of all land exept Chili, must be no problem to miss the few islands by far.


click pic for source

Cheers,
Angel

 

I envisioned a daggerboard on the bow that swings up and down. No need for the extra work of a daggerboard casing that takes up space and adds weight. One rudder at the back and one daggerboard up front - easy and less weight.

I question the usefullness of having masts side by side on this small boat

Not a good idea at all.

 

If we assume that he should round Cape Horn in January at approx 60 deg W and we assume that he does the trip in 12 months that means he should cover around 30 deg per month. 12x30=360
Jan = 60 W
Feb = 30 W
Mar = 0 W
Apr = 30 E
May = 60 E

That means that he should be around the Kerguelen Islands at this time of year. The southern hemisphere is already in the grips of winter so I am assuming a course steered at 45 deg "should" be not too cold.

Now when I look at todays Ugrib weather report for that area the boat MUST have good lateral resistance because you will be on a beam reach in 40knots of wind OR ELSE YOU WILL BE BLOWN MILES OFF COURSE.

Ugrib = 45s - 60e = 35.8 knots @ 340 true @ 1017 mb

This is not "downwind sailing" trade wind style.

South Africans represent less than 1% of the worlds sailing community but each and every one will give you a stern warning of the southern ocean. The boat MUST tack well to steer off the lee-shore or else face a journey that will take twice as long in the freezing conditions off the Antartica.

 

Sven: (quote)

"I believe a deep fin keel with a heavy bulb is going to create bad movements...."

When re-reading this again made me suddenly realize boat design in a new way to a degree...the word aeronautical (aero) and (nautical)...It made me think of a vessel more as a vessel of the water...AND the air...in a way I hadn't before...
Aircraft Pilots only encounter strong wind (currents) in venturi-like areas like canyons.etc....or at high cruise altitudes....or in pressure gradients like cold front and storms...There is not a single set of weather elements (air currents) that an entire boat is exposed to...like an airplane has.....except in a seaplane landing or taking off...then it is a boat with..."weather set" above the waterline.... and a different (but related) "weather set" below.....Now in the case of a deep fin keel...the nautical aspect of the vessel cannot be controlled as much really since a deep fin is permanent and stationary and un-movable....unless a canting keel....Anyway...was more to it but it ended up being incoherent and ramblin.... but I do feel better about my heavily ballasted shoal-draft centerboard boat...and glad to have more overall versatility due to a c/b... I am just postulating..but maybe Sven seems more willing to be subject to air currents which may be fierce but controllable to a degree due to low-profile and daggerboards...than water currents (a deeper keel puts currents in play more)...while a daggerboard flat-hulled boat area wont catch the currents as much...He's going to have sled-rides...it's just how much sledriding vs. how much gaining ground...divided by your energy/stamina/food supplies.etc...His theory might be correct and he can bob around alot and eventually get upwind but it's going to take awhile...

 

Sven took the trouble to respond to some of the above posts.

He gave an explanation about the planned forward lateral area, probably a pivoting centerboard, and the weather patterns at his speed.

Much appreciated Sven, thanks for your time

Happy building and thanks for sharing the build and your adventures and thoughts

Good luck !
Angel

 

It could be something like this mock-up on Yrvind.com. - December 1, 2009 (bottom post of the link)


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I'm sure we will learn more about what it's gonna be on Sven's website as the build continues.

Cheers,
Angel

 

Hey Angel well spotted
we always wondered if Sven actually reads our little conversations
now we have positive proof

Thanks Sven we love you

 

this says it all

good one

 

Departure tentatively scheduled from Tasmania . . . . . . Sorry Manie . .

Guess that would be arround August, maybe 2013 . . . . . ? ? ?

Rough sailing timetable guess...

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Probably the starting point will be adjusted to the time Yrvind Ten is ready . . :idea:

Good luck Sven !

Cheers,
Angel