RCD Category 'A' Ocean

[aod]

Re: RCD Category \'A\' Ocean

I don't take issue with that but for certain they have worse weather in Falmouth than they do in the Solent and if you are off to sunny places you usualy have to go that way.
I did the AZAB in 95 and then tried to single hand it in an SJ35 called Act of Defiance but when the control unit burnt out I had no means of steering so I retired 60 miles W of Ushant. I wouldn't mind but I had the bastard thoroughly checked two weeks before the race and although I had two drive arms I only had one control unit.
If I ever did a race like that again I would take a leaf out of Mary Falks book and take three completely independent means of steering.

The boats used to offshore racing and I raced her in the non stop around Britain and Ireland race in 2000 and the 2 handed RWYC Iceland race in 97. Surfs nicely off the wind but upwind in a strong blow you have to really work the tiller to stop her crashing about all over the place. I think the thing that struck me the most in the AZAB was that left to her own devices she took a terrible pounding and banged and shuddered indeed the whole boat shook when waves broke on the transom.

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[NigeCh]

I sail 2 odd boats both RCD Cat \'C\'

One is a Wayfarer (Round Ireland) and the other is a Contessa 26 (Biscay survivor)

The RCD ratings (and STIX numbers) are part of the so-called 'anti-risk political let's-pretend-to-get-it-right anti-being-sued-for-getting-it-wrong nambie-pambie scenario'

A Contessa 26 will take me wherever I want to go to ... Birgitta has been to La Coruna and Horta: We've been knocked down but never quite rolled. I've never been unable to bail the Wayfarer .... but I've been sunk twice on RCD Cat 'A' boats in coastal waters.

IMO, what the RCD hasn't got right yet is a) AVS and more particularly b) down flooding caused by inappropriate locker/hatch/washboard design.



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[Chris_Robb]

Re: RCD Category \'A\' Ocean

Richard - as you say - you need three back up systems! Interested that you had such slaming problems down wind. I have always been concerned with my Victory 40 with its large poopdeck and flat transom with windows, that this could be a danger. Although the windows are extremely strong - they once withstood the impact of the bowsprit from a Falmouth Oyster boat - before breaking with his second attempt! - that this flat area could be a problem. Not much danger in pooping though as the centre cockpit is totally enclosed.





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[AndrewB]

Sueing the Builder

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<font size=1>It will be interesting when someone sues a builder having survived structural failure in a CatA AWB - surely it's only a matter of time. Maybe once this happens manufacturers won't be quite as keen to stick this tag on their boats.</font size=1>

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My memory is a bit distant on this now, but relates to the case of a new Moody that was lost in the Thames Estuary about 10 years ago owing to rudder failure. As I recall, the defence that Moody's put up, was that the yacht and in particular the rudder had been built to certified Lloyds A1 standard and so the fault was in the standard, not their responsibility.

The consequence was a nightmare for the owner. His insurers refused to pay up on the grounds that the loss was due to a structural defect, and Moody's equally refused to accept the rap. Until, that is, the owner turned up evidence that a number of other yachts of the same design had also suffered rudder damage. Settlement was out of court and barely mentioned in the UK mags - I read this in Cruising World.

 

[dulcibella]

Truth vs Vested Interests

Sad but true that manufacturers of boats from about 10 metres upward have a vested interest in getting a class A rating and have been able to exercise effective pressure for criteria that include almost everything of that length. Unfortunately the reviews in the mags don't help inexperienced buyers. I'd love to see the reviewer of a new 11 metre flat-bottom point out that the only way to get the brute to stop screwing to windward in a F7 aft of the beam is to dump the mainsail, but this is another area where vested interests - advertising pressure - operates.

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[qsiv]

Re: RCD Category \'A\' Ocean

To be pedantic, the ability to self right after 180 inversion doesnt have anything directly to do with the AVS. It has everything to do with the layout of the deck, the ballast ratio, and perhaps most importantly the volume of the deck structures (many of the open 60's could only pass their self righting test by altering the shape and volume of the doghouse - one even needed an airbag!).

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[qsiv]

Re: Mutually exclusive

Love the comfort rule - but you will need to discard for my 'sail around the bay trip'. I believe we will be talking more of ankles as the relevant joint!

As Flanders & Swann put it decades ago, it will be '.. short but none the less nauseating!'.


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[charles_reed]

Re: RCD Categories

Unfortunately they have little to do with a boat's seaworthiness and more to do with size and levels of safety equipment.

I certainly wouldn't like to be caught out in an Atlantic F10 in any modern production boats, they work badly enough going to windward in a mediterranean F6.

Again the RCD is a bureaucrat's attempt at "organising" something he doesn't understand and which has so many variables that any two experts will produce at least 3 opinions as to what is a seaworthy boat. The truth is that it is impossible to produce a simplistic "rule" for the protection of the flock of EC citizens.
The RCD has merely served to give people a false sense of security.

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[ponapay]

Re: RCD Category \'A\' Ocean and Gales at Sea

I agree, the only time in my Nich 38 that we have slammed was when well pressed in a north sea gale, and it was the bow that slammed not the bottom of the hull. A reduction in sail, an alteration of 20 degrees and more careful helming stopped all the slamming.

On another occasion heading under power straight into force 10 in short seas with little fetch (6 miles) we did not slam at all, but the speed was down to 1.6 knots most of the time and occasionally down to less than half a knot. The ride was very uncomfortable but neither me nor my (aged) crew members were ever doubtful that the boat would see us through.

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[Chris_Stannard]

Re: RCD Category \'A\' Ocean

I brought a Najad 460 from Sweden via the Kiel Canal in May this year. On passage from Ijmuden to Dover we caught a North Sea gale (not forecast). Because of the shipping lanes and shoals limiting our sea room I decided to motor sail using about half of the main. My opposite number relied on the autopilot and found that the cest course he could steer was about 60 degrees wind apparent, it the boat was not to slam. this was caused by the short steep seas you get in shallow water. We did not make much progress.
I chose to hand steer and could make a course with about 20 degrees apparent wind, but sliding off when I could see a steep wave coming.
Incidentally from my time in the Navy I have a cine film of a destroyer with about 25-30% of her keel out of the water and she certainly slammed.
I do not believe that you can make a boat that will not slam if you hit a wave the wrong way, but if you read Adelard Coles "heavy weather sailing" you will find advice on how to steer in bad conditions and this works. the problem is that there is no known autopilot that can do it since you have to bear away at the crest of the wave.
Even so I have met the wave, off the coast of Brittany, which had no back. We dropped off it about 8 to 10 feet, though it felt like a lot more. This is produced by a combination of waves which add up to a square waveform, and if you do not believe this is possible go and ask an electronics guy to show you how it is done on an oscilloscope. If we can do it in the lab sure as hell Mother Nature can do it for real. If you meet a wave like that your boat will take a hell of a pounding and I doubt the ability of many lightweight modern designs to do that without some damage.

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[MainlySteam]

Re: RCD Category \'A\' Ocean

I think one of the contributing factors to modern small yachts slamming, apart from their hull lines, is their low weight and comparitively small mass moment of inertia (light ends, light rig and keel of low mass and draft) so that they are easy to rotate longitudinally in relatively small seas (low energy input from waves needed to pitch them). Similar and explaining example is a heavy rimmed wheel is harder to rotate than a light rimmed one. That maybe also explains why they do not motor well onto seas (so I am told) as when the boat pitches the drive provides part of the energy wasted in rotating the boat - leading, ultimately, to bogging down the engine if very heavy pitching (which I have certainly experienced in a heavy displacement small vessel in very steep short seas).

There is a speed penalty for having a higher moment of inertia, but from a cruising vessels standpoint it is of trivial magnitude.

Coming out of a steep backed wave, as you describe, is another thing as the closer to free fall the boat is without any pitching rotation I would expect a light and heavy boat to tend towards falling with the same acceleration (gravity) and hence same terminal velocity when hitting the bottom with the big bang.

I wonder what other views there are on this?

John

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[Robin]

Re: RCD Category \'A\' Ocean

One difference over the years maybe forgotten in the debate over traditional versus modern designs is the size and reliability of the engines fitted and the expectation that you can still carry on pounding to windward in gale force conditions. With average motor power of just one hp/ton (that was a quoted figure) you sure as hell HAD to sail if you wanted to go upwind in any wind or sea. Under sail you would be taking the seas at an angle, there were no autopilots either so there was someone to steer around the worst seas, indeed it was in their interest or they got even wetter, they couldn't hide under the sprayhood.
Nowadays boats are fitted with reliable diesels and considerably more HP, people are used to sailing to timetables and therefore passage speeds must be kept up, on goes the engine it's time to bash & crash.

Don't let's kid ourselves, all boats slam given the right set of conditions, but I firmly believe that a sailboat will be more comfortable and slam much less if under sail. This pre-supposes that the design is one which will still sail and make ground to windward in gales, mine certainly will but there are a great many out there both ancient and modern that will not. There are probably a similar number of owners who if faced with such weather would turn to the engine before the storm jib.




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[Chris_Robb]

Re: RCD Category \'A\' Ocean

Robin - I do take issue with you about all boats slamming. I have had Corsair - who can steam into a full gale quite happily - into some very difficult seas. With excessive heel - ie I should have reduced sail - she will slam on the side of the bows sections. However once sail is reduced to bring heel down under 20 degrees - I have NEVER had her slam. She hardly ever takes it green over the foredeck either. In bad weather I have huge respect for the boat - no tendancy to broach - no directional problems if rolling - NO SLAMMING. I cannot say the same for lighter varieties that I have been out in in lesser conditions.

AND - i haven't worn Oillies this year either!! -

Chris

PS - do you know if any swing moooring are available in Poole for next year????

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[Robin]

Re: RCD Category \'A\' Ocean

OK Chris I give in!

She must get 'stopped' though by the odd wave, presumably doesn't bang when she does. As a matter of interest how many HP are needed to keep Corsair driving into a gale with sea to match?

We haven't worn oilies either this year, not even once in just on 2,000 mls.

Poole Its A Beautiful Place! I will send you a PM with phone numbers for moorings so others don't get a head start.....

Robin


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[snooks]

Re: RCD Category \'A\' Ocean

I agree that it's not just the hull lines, but their low weight, that can lead to slamming

There's a way of reduce the slamming effect on AWB's, and that's to increase the ballast low down...one way, and probably the easiest, to do this is to take bags of sand onboard keep them in the bilge and reduce the weight (pour the sand over the side) so you reach a compromise between stability and performance....once finished get the weight of sand made into lead blocks and glass them into the bottom of the bilge, make sure the weight isn't just in one point, but spread along the backbone of the boat. This will dampen down the movement so she doesn't pivot sharply.

You should find she'll carry her way through the water rather than bobbling over the top of waves.

One of our yachts had better stability and less of a tendecy to slam after the hull was strengthend round the aft end of the keel, with SS and a lot of CSM, sails like a dream all the weight is in the right place. And the perfomance and stability of a wing keel 28fter was improved using the sand/lead method above.







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[MainlySteam]

Re: RCD Category \'A\' Ocean

I agree with you. While most yachts are only sailed in smooth waters so slamming (using the term in the noisy banging sense) is not really an issue, a good sea boat, putting aside events such as falling off steep waves, etc, will not slam even when driven into steep seas.

John

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