Adventures with Stability.

capnsensible

capnsensible

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The transatlantic season is now building again to start of the fantastic voyage for many people.

It's also the time that some of the more eccentric approaches to yacht stability also appear....

Outside of the ARC there will be very few, if any, commercial yachts involved in this. It's nigh on impossible for a commercial vessel to get a stabilitary category at an economically viable cost to take paying people on this trip of a lifetime.

So, with the freedoms we have, once again I watch with interest the customisation of yachts (various) and wonder how small craft designers, past and present, feel about the 'enhancements' to their carefully crafted calculations??

There are always interesting threads here about the suitability of various design times for blue water, but mebbe a look around the traditional departure havens can be an eye opener.

So, add large quantities of food, water, spares. Diesel cans lashed around the deck. Radar reflectors and radar transmitters up the mast, and a foghorn, think leverage. Plus of course, the rib on Davits, a gantry with solar panels, wind generator, bicycles and a mass of other gear and what do you get? A self contained world of cruising comfort, or an accident waiting to happen at the first serious goffer (wave)?

Does the keel design make a difference when these overloaded vessels put to sea? Should seamanship ensure that the vessel floats to its design marks? What are you happy to push the limits to?

Personally, I've always made the most of going simple on my own boat, stowing things as low down inside as possible. But deck tankage is inevitable, I think. It's always a compromise but this thread has been prompted by some of the head scratchy things I've seen in the past month or two. Bless em.
 
Your descriptions put the pointless arguments about the affect on stability of a furled in mast mainsail into perspective!
 
Tranona said:
Your descriptions put the pointless arguments about the affect on stability of a furled in mast mainsail into perspective!
Click to expand...

:)

Just around me now I've got three older yachts, well lived on and, well, enhanced above the waterline!

I'm writing this on an iPad, have taken pictures of them with it but unfortunately can't get to post them on here.

I'm sure they will make it across, nearly everyone does, but I'm sure some people would be surprised at how some boats are prepared!
 
An interesting idea for a thread - we are planning to get down to the Canaries around September next year to either stay for a season or cross - mostly depending on financing the time away from work.

But we are already very loaded with 8 years of Med ownership and on deck have a rib on the foredeck, two outboards on the pushpit and a Bimini which will have flexible panels so can't be folded away so easily in a blow. Then of course we will be adding a lot more diesel on deck and probably displacing cockpit locker contents to the forecabin. Plus a lot of bottled water and food.

I'm hoping the extra windage will be small but the extra weight won't be but I'd have no idea how to tell whether the extra weight in the cabins is helping the boats stability or hindering it. It will certainly slow down the boat.
 
I reckon that the Canaries are ideally placed for peeps to have that 4 to 6 day proper offshore go at it in order to make some final (not literally!) decisions about how to best manage the yacht. Its all a bit of a risk, but how far to go?

Ive always used just a general seamanship eye when preparing boats for the blue bits rather than a 'designer calculation' and gone with what 'looks right'.

However, there are more than a few around that certainly dont look like that happily bobbin around all through the Windies and beyond and I do sometimes wonder how close some were to the edge.

Forgot to add windvane steering, outboards, kayaks, paddleboards and on a new neighbour, an anchor and a dog complete with cushions and a shade. ;)
 
I can't understand why you would want to carry extra diesel on deck on a tradewind passage.
Maybe it's cheaper on this side?
 
Alan S said:
I can't understand why you would want to carry extra diesel on deck on a tradewind passage.
Maybe it's cheaper on this side?
Click to expand...

Friend of mine with a reluctance to use a bit of engine assist took 43 days, Canaries to St Lucia. Most people dont have the luxury of that time and can do a bit of windseeking.

The winds can be a lot less reliable than is generally imagined. Also, not everyone has an alternative to battery charging than the alternator.
 
capnsensible said:
Friend of mine with a reluctance to use a bit of engine assist took 43 days, Canaries to St Lucia. Most people dont have the luxury of that time and can do a bit of windseeking.

The winds can be a lot less reliable than is generally imagined. Also, not everyone has an alternative to battery charging than the alternator.
Click to expand...

On my one Atlantic crossing we took 10 25l cans from a nearby chemical works tip and had used half of them by the time we reached St Maarten - and used all but one by two thirds of the windless trip up to Florida.
 
I've always thought it reasonable to use the engine when appropriate to keep the momentum of the passage going.

Juggling the consumption figures and days to go gives a bit of a mental work out to.......:)
 
Of particular concern are amateur builders of small steel yachts who adapt the designs to give them better headroom. At one time this was all too common. I remember once getting onto a yacht supposedly of the same design as mine, which tipped almost like a dinghy when one stood on the side. The owner quickly gave up on plans of ocean sailing.

My own yacht had exceptionally deep bilges and it was actually an asset to stability to have them completely filled with supplies for long passages.
 
Interesting. I wonder where this is going to go.

Idle curiosity prompted me to look for a commercial ARC on a cat 0. I found a few at rates not much different from the others.

The economics of which I couldn't speculate, truthfully I find it hard to believe any boat can be economically operated in the sailing business. Yet clearly some do.
Some years ago, I considered buying a boat and taking off by myself. I met a girl and changed my plans.

I looked at a Sadler. I liked the reserve buoyancy concept. I had a chat with Sadler. I think it was the guy himself. He was quite willing to give me the stability data for the boat if I ordered one. He also advised me where to stow gear provisions water. I cant remember the numbers but we got as far as discussing how much weight of gear was reasonable before adversely affecting performance and the reserve buoyancy concept. It was his opinion I didn't need the stability data. The Vast majority of people wouldn't understand it. Or be able to use it. including me. Bottom line my understanding and intended use of the data. Was not what the data was about.

TPI not realistic, TCP even less realistic. KG per CM or just don't submerge the strip at the top of the anti fouling if it looks ok reasonably even keel for and aft and no list. Should be fine 3 or 4 people with a couple of bags of gear and a months worth of water and provisions. were within designer parameters.
My memory may be faulty, Most of the weight of the boat is in the Keel. CG bellow the hull. CG loaded for a voyage would have been about bottom of the hull. Hull fills out a lot from keel up. TPC or KgPC increases a lot with increase in draft.

He was nice enough to humor me. Stupid questions from a dreamer. He took the time to talk to me others didn't.

Bottom line compromising the stability of a fin keel sailing vessel requires some effort. I am sure if try hard enough it can be done.
Converting a fishing boat into a nice motor yacht. Compromising the stability. I've seen that done.

Once upon a time I thought a Sadler was a reasonable choice of boat to head off into the sunset on. Why? reserve buoyancy.
Today I would wonder if a Sadler or Starlight could qualify for Cat 0 based on alternate provision for reserve buoyancy. I have never actually looked at the requirements for Cat 0 so I have no clue if they could or not.

I do own a boat about the same era, about the same sise, sail boat fin keel, much lighter, bigger rig, and no way in hell would I venture out of sight of land. I just don't want to. I like sailing from Pub to Pub.

Its pretty stable probably even more stable than a Sadler. 10000 Lbs of lead dangling under a lightweight balsa cored 35ft IOR hull.
Reserve Buoyancy? Intact lots Damaged reserve buoyancy? None. Damaged Stability? irrelevant Its going to sink. At least until completely swamped.

Weather tight? Nope. Mostly showerproof.

Water in cockpit, If it reaches the locker It will down flood.
Is my hatch weathertight? Nope.
Fore deck hatch weathertight? Welll not really Splash proof. Windows? Splash proof.

Suitable for ARC? Lots of similar boats have and vast majority made it. Which doesn't necessarily mean it was a good idea.

My Conclusion.
My mid 80s old 35ft cruiser racer. Is a 0 compartment. probably splash proof old tub. A heavy rainstorm might sink it:)

Stability? good enough for me.

My slight recollection for Cat 0 single compartment is required or alternate equivalent.
Which means able to flood any 1 single compartment and still have positive stability and positive freeboard with the deck not submerged.

A few other bits and pieces are include like a minimum angle of down flooding. area under the curve, righting leavers ect.

But if it wont stay afloat who cares:)

Cross an ocean? Hell I shouldn't even take across the straight. :)
 
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