Swain BS_36 Stability curve

[Jack Hickson]

Originally Posted by welder/fitter

Well, it has been a long time but as I recall Dove III had transverse framing, a centreboard, & I still believe that the skin was thicker, but could be wrong, it's been a long time.

As for the "16 days in large surf..." I've never claimed anything, although I have been told that the mantra is much exaggerated. As I consider "he said/she said" to be anecdotal, at best, I've never felt it of value to state that (Name) told me...

Dove had zero transverse framing and 1/8th plate. If she had transverse framing, she would have been badly dented between the frames. She has no dents whatever.
I don't have a 36 ,and most people I know with them are heading north this time of year.

BC fast ferries are an excellent example of the top number crunchers available being hired to calculate everything. They were abysmal failures , and were sold for below scrap prices. Welder fitter was paid for that project.
What do you call someone who can cross and ocean and not learn anything? A slow learner.
Douglas fir has a tensile strength of 1500 PSI , steel 60,000 PSI . Someone who would rather be in a plywood boat in rough conditions has a judgement problem. Compared to steel , plywood is flimsy, by any comparison, or calculation. The sea doesn't show favoritism for wooden boats over steel ,on a lee shore.
Ability to survive screw ups is an important factor in any offshore cruising boat. Believing you will never screwup is self delusional, and just plain bad seamanship .

[MikeJohns]

Originally Posted by Jack Hickson

............
Douglas fir has a tensile strength of 1500 PSI , steel 60,000 PSI . Someone who would rather be in a plywood boat in rough conditions has a judgement problem. ............

Maybe they know their material properties ? The steel you are building with yields at 36000 psi, Anyway you design to the fatigue limit, that's where the sea more commonly eventually breaks your boat. It's a lot lower than 36kpsi.

Steel has the best abrasion resistance but at sea you can make a boat safely out of any reasonable material to a strength that the sea can't break it. That's what class scantling rules are about.

As for stability and safety in the extreme event, intuition is a very poor teacher. Intuition tells you that a comfortable ride in a severe storm is safe. That unfortunately is an observation that lead to the deaths of many seamen. It's also why stability is so closely regulated in commercial vessels and part of that is that the CoG is accurately deduced from inclining experiments. Displacement is also obtained quite accurately from a simple freeboard measurement. ( providing accurate lines).

Very experienced seamen will be very antagonistic when you tell them their boat is dangerously unstable, they mutter about boffins with no sea time.

[Dean Smith]

Quote MJ

Very experienced seamen will be very antagonistic when you tell them their boat is dangerously unstable, they mutter about boffins with no sea time.

So if one is a very exp. sailor and very experienced builder and one says um, I will draw and build myself a 34 yacht
She will have transverse on 400, she will have nice deep floors, she will be at departure 8000 kg she will have 3800kg of lead in a scheel keel 1700 deep. She will be tight , tight in the hatches tight in every egress. She will be weatherly, she will have 4 hd, sls ready to go so that she will power on the wind when the wind gets UP there.
Does one need a NA, the answer is no After a life time one can look at a boat and say Ah she is sea kindly
mind you so far I just read total gobbledegook from ole BS

[Dean Smith]

and does he need) i took this 4 years back in Tr

[rwatson]

Yeah - anyone can brag about their 'experience' and 'instinct' and whatever else they think gives them their superior status.

But unless there is some serious impediment to getting qualified calculations done, failure to do so is just sheer pig-headedness and egomania.

Self - praise is no recommendation .

[Dean Smith]

Originally Posted by rwatson

Yeah - anyone can brag about their 'experience' and 'instinct' and whatever else they think gives them their superior status.

But unless there is some serious impediment to getting qualified calculations done, failure to do so is just sheer pig-headedness and egomania.

Self - praise is no recommendation .

so when YOU apply for a position, you say nothing abt yourself? how very odd, good day to you
And OH please tell this to countless generations of artisans
And who said anything abt superiority? or bragging,? by your post you are on my iggy list, please feel free do same

[rwatson]

So you didnt get your designs checked by an NA either I take it ?

[MikeJohns]

Originally Posted by Dean Smith

..............
Does one need a NA, the answer is no After a life time one can look at a boat and say Ah she is sea kindly..............

You might want to step aboard for a start and stand with a few friends on the gunnel midships. Some very seakindly salty looking boats lie on their ear when the wind gets to 20 knots. The Dellenbaugh angle is a very good piece of information for the monohull sailor, a full GZ curve at half stores and with all equipment aboard is the best indicator of safety against being rolled that you can ever hope to get.

Very few of the cruisers have anything like the stability they think they have. I just tested a traditional full deep keeled yacht and the CoG was significantly higher than the designers published estimate and the AVS was under 110 degrees, not the 147 they expected and that was even without raising the sails.

You don't need a NA/ME but you can follow the same procedures we use to ascertain stability. It's not hard and it's an accurate assessment.

[Dean Smith]

oh I am quite sure there will be exceptions, same as there will be exceptions with so called qualifieds? see those sinking launches
But by and large we, us , boatbuilders usually can get it right, same as you can
But how can you deny as Watson has that for eons we simply did not need Boffins? please enlighten.
How did the Greeks, Nordics, Romans , Polynesians, get around without the the schule of Tasmania? Come on!!!

[Wynand N]

Originally Posted by Jack Hickson

Someone who would rather be in a plywood boat in rough conditions has a judgement problem. Compared to steel , plywood is flimsy, by any comparison, or calculation. The sea doesn't show favoritism for wooden boats over steel ,on a lee shore.

Brent, Apparently you did not read my previous post...do not use my personal preference to make you look like the king of the **** pile.

Have you ever heard about the "Voortrekker"
This is a cold molded ply wood RACER (before the event of epoxies) This boat, designed by the Dutchman, Ricus Van De Stadt and built in 1968, competed very successfully for more than 20 years with Bertie Reed at the helm, often beating modern, state of the art boats at their own game.
Built from cold molded ply, 50ft LOA, weighing only 6.5 tons.

Voortrekker raced the Cape to Rio's, Cape to Uraguay's, Ostar, BOC Challange, Globe Challenge, etc etc , many of them a few times always with her master , Bertie Reed at the helm.
For 20 plus years she took every and anything the seven seas - and Cape Horns a few times - could throw at her, despite her light weight, remained sound. She was a master piece of engineering and a testament to v/d Stadt's design ability This highlighted words you would not understand....

"Voortrekker" continued to sail to this very day and is used for the navy for training sailors and used in all local racing events.
On 10 January "Voortrekker" again competed in the 2009 Heineken Cape to Bahia yacht race in the South Atlantic.
http://www.supersport.com/xtra/artic...seas&id=284471

Now what more can I say Brent Jack Swain Hickson? This cold molded ply wood boat RACED for 40 years, mostly in the lower southern latitudes by world class racing skippers - read, not fair weather cruising and sitting at anchor/mooring - and is still in racing condition. And it does not even have one rust stain after 40 plus years on the big blue.....
This boat rounded Cape Horn a few times on bad days, completed racing circumnavigations etc etc long before any of your tin can creations saw the light of day and is still going strong.

If you can make similar claims or better with your BS boats, perhaps them (maybe) you can sway me to believe in steel as the ultimate building material. Until then, Im sticking to plywood.

As for strength, MikeJohns summed it up nicely and I quote;

"Steel has the best abrasion resistance but at sea you can make a boat safely out of any reasonable material to a strength that the sea can't break it. That's what class scantling rules are about."


But then again, scantling is something you would not understand from past discussions.

[Dean Smith]

Wyn, what is diif Voor and boer? please. If I had one wish, it would be to be fluent in many languages

[bntii]

Mike- perhaps fodder for another thread, but I read with interest the following:

Originally Posted by MikeJohns

intuition is a very poor teacher. Intuition tells you that a comfortable ride in a severe storm is safe.

Originally Posted by MikeJohns

Very few of the cruisers have anything like the stability they think they have. I just tested a traditional full deep keeled yacht and the CoG was significantly higher than the designers published estimate and the AVS was under 110 degrees, not the 147 they expected and that was even without raising the sails.

I had always taken the deep and narrow form of my CCA rule Rhodes to give both comfort and safety.
Not necessarily so?:



I mean- narrow bows so she might pitchpoll, and attached rudder so she might slew around and broach, narrow so she might be rolled... but safe other than that eh?

[MikeJohns]

Originally Posted by Dean Smith

..........
How did the Greeks, Nordics, Romans , Polynesians, get around without the the schule of Tasmania? Come on!!!

Ha !!!

They accepted their losses and often enough they didn't get around very well at all. They survived if the gods were merciful and willing. Decimated fleets from bad weather were the norm. Missing vessels and drowned crew were just par for the course and an accepted fact.
Faith in providence rather than trust in the vessel. Like Odysseus and his crew you survived or died depending on the whim of the gods, that was an accepted fact. The seaworthiness of many of those old vessels was abysmal.

[MikeJohns]

Originally Posted by bntii

..............I had always taken the deep and narrow form of my CCA rule Rhodes to give both comfort and safety.
Not necessarily so?:.......................

I mean- narrow bows so she might pitchpoll, and attached rudder so she might slew around and broach, narrow so she might be rolled... but safe other than that eh?

From a robust designer you will get a good boat, I think you'll be fine. No small sailboat is really comfortable in heavy weather, just less miserable perhaps might be a better term. Your narrow heavy boat is more seakindly becasue it reduces vertical acceleration but there is another comfort factor, and that's in the jerkiness of the roll.
If you reduced your metacentric height GM (and reduced your stabilty) you would also find it more comfortable, less jerky. More seakindly but less seaworthy by means of a reduction in GM. That's the one people intuitively confuse.

[Wynand N]

Originally Posted by Dean Smith

Wyn, what is diif Voor and boer? please. If I had one wish, it would be to be fluent in many languages

Stu, "Voor" means front or in front, but also before, depending on how it is used. "Trekker" means puller or tractor. However, "Voortrekker" does not means front puller but in fact pioneer/settler.

"Boer" on the other hand means farmer and the word is color blind. But is is also a slang word for the police or amongst the blacks a slang word for a white man.

Hope this help.