RCD Category 'A' Ocean

[nicho]

RCD Category \'A\' Ocean

Those who have read my recent "Atlantic adventure" post will be aware I recently suffered at the hands of an Atlantic storm in an AWB. In the middle of the pounding, I got to thinking about the RCD Categories and what they actually mean in such circumstances.

As I understand it, any boat awarded Cat 'A' is considered safe for ocean use, and that seems to be applied to just about every modern production boat, above about 32 feet, including my Bavaria 36, and of course the Jeanneau 452 I was on during this Atlantic "hooley". However, whilst I have never had the good fortune (?) to witness such awful conditions in any of the the more fancied blue water yachts, (Rasseys/Najads/Swans/Contests/Farrs etc), I cannot help but think they do not suffer from the constant slamming that our Jeanneaus hull had to endure.

I wonder therefore, if the RCD categories should be rethought, to perhaps sub divide Category A in to two parts:

Category 'A' 1 - for boats with hulls that are heavily laid up, and of such a design that they will not suffer from constant slamming - presumably this would apply to the aforementioned blue water boats, and suitable for prolonged ocean use.

Category 'A' 2 - for the modern AWB, that will indeed SURVIVE such conditions, but at the expense of major discomfort of the crew, and the risk of minor structural damage.

The Jeanneau 452 I was crewing, shook and shuddered violently in the big seas we were pounding into, the relatively flat bottom seemingly unable to cushion the hammer blows, to the extent that hull flexing eventually broke the foreward cabin bed joinery. The hammering noise and jolting in such conditions, when witnessed from down below, had to be seen, felt and heard to be believed!! It led us to wonder whether such treatment could be maintained for prolonged periods without more serious structural damage.

There was a story doing the rounds at our Gibraltar starting point, that a largish Beneteau on it's way to the Gran Canaria start of the ARC encountered a major storm in the Bay of Biscay, and suffered serious structural hull damage, to the extent that it would need some serious rebuilding.

Our modern, AWB did indeed survive such conditions, and in that respect, it did perhaps live up it's category 'A' status...but is it really suitable for prolonged Ocean use? Along with my Bavaria, and many other lighter displacement modern boats, I don't think so, hence my question about a broadly applied RCD 'A' category.

What do you more experienced guys feel?

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[tcm]

Re: RCD Category \'A\' Ocean

I don't think any boat can be designed for "constant" slamming, and i would do something else (go slower, faster, or in a different direction) to stop slamming after the first slam. Not a great skipper if he carries on "constantly" slamming imho. I think you did very well to get through what you did and I wouldn't be surprised if you were a major factoer in keeping spirits up (if only by being one of the few not feeling queasy) - but I don't think I applaude the circumstances by which you were put there - and then continued.

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[Twister_Ken]

Mutually exclusive

Many modern hull shapes are derived from racing boats. The essential requirement of a racing boat is to go faster. An enemy of speed is immersed volume underwater (= more underwater surface = more drag). Combined with a desire to plane when the wind is free which requires relatively flat underwater surfaces.

Hence:
With less underwater volume, more boat comes out of the water when going through waves, so it has to go back in when coming off a wave = crash, and
With underwater shapes being flat = smack.

Result, spectacular but uncomfortable.

Twister Ken's Comfort Rule
When in a boat, work out where the water level is, relative to your body when standing on the saloon floor.

Below knees = uncomfortable.
Above hips = comfortable.

I don't believe this is covered by the RCD


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[webcraft]

Re: RCD Category \'A\' Ocean

I'm not sure anyone has much faith in RCD classifications any more.

For one thing, Cat A boats can have an AVS as low as 100deg so long as they are big enough . . . which means they may well stay inverted after a rollover.

By contrast, stable, proven heavily ballasted designs under 30ft can never attain Cat A because of the way it is calculated.

Secondly, as nicho experienced, prolonged slamming can cause structural damage. It's all very well to say don't go to windward in these conditions, but if the alternative is being wrecked on a lee shore than you need to know the boat can take it for as long as it takes.

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.

Given freedom to choose a heading I am sure that most AWBs can be kept afloat in most conditions provided the skipper has sufficient skill and experience. Older more traditional designs, however, are more likely to look after their crew even when not sailed with pinpoint accuracy and anticipation.

All IMHO of course.

- Nick

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[rhinorhino]

Re: RCD Category \'A\' Ocean

It seems to me the major flaw it this line of reasoning is that the worst sea conditions occur in "Oceans". Coastal regions where the sea shallows often have the worst conditions. The only real rational seems to be that on the Ocean you can't get to shelter.
I suspect that anyone who thinks that "Cat A" means "will happly go through the Southern Ocean the wrong way without damage" may be in for a suprise.

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[Robin]

Re: RCD Category \'A\' Ocean

Nicho

Slamming has more to do with hull design and how the boat is handled than displacement (ie weight of layup) and there is a misconception I suspect that modern designs from the likes of Swan, HR, Najad, Contest are just like their older and slower models used to be with long keels, deep forefoots and so on. I would guess that performance design has crept in with these makes too over the years as a look at the designers used will show.

I believe from a reply to one of the posts that during the storm the Jeanneau 452 was under engine alone, no sail up, and was bashing upwind straight into the seas. I have to say that in my very humble opinion and from the comfort of my armchair that ANY boat would have slammed very badly if treated thus.

My previous boat was a very heavily built Westerly 33 Ketch (deep forefoot) with a 50hp 4 cylinder engine and 3 bladed prop, quite capable of bashing upwind in very heavy wind/seas but not if you wanted an intact set of teeth after the trip. W33s have done many transatlantic crossings and RTW trips and one is recorded as having survived a F11 storm. However we once went up through Alderney Race in ours with big spring tides and against a NE6-7 headwind, motorsailing with main alone and it was horrendous, in one big slamming crash the spinnaker pole flew overboard from it’s deck mounts and cleared the rails untouched. Speed slowed to 3kts at revs for 6kts plus, we tried more revs but the slamming then was unbelievable and we backed off , We should have been under sail but reefing the main to do so was not an attractive option in the seas.

In our current Jeanneau Sun Legende 41 this summer we were beating upwind against NE5-6 along the N Britanny coast from L’Aberwrac’h to Trebeurden , beautiful sailing on a sunny day and dry enough to leave the hood down. Just before Isle De Batz (where there are very strong tides/overfalls) we passed a heavy wooden ketch who was hobby horsing horribly, motoring into the wind and sea, and I thought how much better he would have done under sail. A mile or two later and I realised we would not clear Isle De Batz without tacking out to sea again and very stupidly turned on the engine ‘just to get round the corner’. What an idiot! Now we too got very wet, hood went up, speed plummeted and blood pressure rose, the slamming was horrible but our hull is laid up with Kevlar for strength, unlike my teeth which by then were firmly clenched shut. 10 minutes of this crap was quite enough and we reverted to sail, what bliss by comparison and no slamming, yet the wind and sea was just the same.

In your other post, you mentioned that many others turned back, some with damage and this must have included some of the ‘heavyweight’ designs. I cannot but think that without the pressure of a delivery schedule there would have been a better option than motoring into such seas.

As I said, all IMHO from an armchair viewpoint.


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[aod]

Re: RCD Category \'A\' Ocean

I think the question is very interesting. When I got back to Falmouth after this years AZAB I did some thinking myself. I have an IOR race boat with a flat section foreward and in order not to slam you have to screw over the waves coming down the wave face at an angle. Because I was beating into 35 knots apparent in the Western Approaches the seas were short and steep which made this practice quite difficult and very uncomfortable espec when under auto steering. I was on my own on the foredeck ( well, on the boat actualy) changing from a three to the four when the autopilot burnt out and the yacht broached. A crash gybe followed and the main ended up pinned against the runner blowing the lazyjacks on the process.

Anyhow the end reult was that for a time I ended up bare poled sailing down wind and the seas took the yacht from the stern. Every time a wave crashed against the transom the whole boat shook violently and I really did believe that it was only a matter of time before it broke up.

Anyhow the gyst of all this was that after I had got back to Falmouth and had some time to wander around and look at other yachts I noticed how the majority of West Country yachts were traditionaly deep vee'd hulls that were substantialy built. I couldn't help but wonder if this was because of the weather systems down there and yachts had to be stronger to take the hammering.

Anyhow the whole experience peruaded me that if I ever bought a yacht for Ocean/World cruising I would definately opt for the more traditional long keel (and yes, slower) heavily laid up design, maybe be even a double ender (Victoria ish).

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[nicho]

Re: RCD Category \'A\' Ocean

Robin,

I was certainly under the impression that the Rasseys/Najads/Sweden Yachts etc had a hull design that prevents slamming. Perhaps I am wrong in that assumption?

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[AndrewB]

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

I've ocean cruised, and experienced gales, in both types of yacht. And bad conditions are always uncomfortable, no matter what you are in! Slamming is a consequence of sea state and how hard the boat is being pushed specially by motor-sailing, as well as of design. Generally in open ocean the longer waves and weak currents make it much less of a problem than somewhere like the North Sea.

But a purpose designed ocean cruiser with a longish keel, heavy build and high AVS has a lot of advantages. I would not have wanted to be aboard your Jeanneau with a crew of less than 6 because such yachts need to be 'worked' through bad conditions, and damned hard work it can be. By contrast the purpose built yacht will heave to very easily, handle well under self-steering even in a gale, and should even be capable of maintaining its own course on certain points. This way it can be managed by a crew of 2 or 3, not just for active sailing, but also making emergency repairs in bad conditions.

Being in a gale always creates anxieties about one's safety, even though statistically the real risk is not that great. To feel the jarring of slamming, or of a breaking wave smashing into the side, and to see a thin GRP hull visibly flexing, does nothing for one's peace of mind. However, the greatest risks, from a survey I did of a number of ocean cruisers some years back, seem to be associated with (a) capsize (beyond 90 but rarely 360)and (b) damage to the rudder. I for one would always check out an ocean yacht for what is likely to happen in a capsize. If the AVS is low, then it might remain over for a minute or more - what will happen inside the cabin? If the yacht has been made secure for this eventuality then at least the cabin provides a cocoon to which the crew can retreat if a combination of seasickness, inexperience and bad conditions makes it impossible for them to take active measures.

Second, any yacht that has an unsupported rudder is very questionable for ocean cruising, as there have been so many failures in this area. I would always expect such a yacht to have made (and practiced) provision for rigging an emergency rudder that will work in big seas. Having these two matters sorted is for me a great reassurance.

Posters often say on this board that an ocean cruiser spends far more time in port than it does at sea; and this justifies cruising in yachts that are long on accomodation at the expense of being 'seakindly'. I can't disagree with the first statement, but I do know that it generally only takes one experience of the type you have had, to persuade most people to trade a lot of home comforts in port for a small amount of seaworthiness at sea.

Whether one can do much with the RCD is doubtful. Anything like this must be a blunt instrument at best. Its principle failing is that the category descriptions mislead the inexperienced - specially as they are presented by salesmen. In the right hands, all Cat A yachts may be 'suitable' for ocean use, but in the final analysis though it is the crew rather than the yacht that determines capability at sea.

 

[nicho]

Re: RCD Category \'A\' Ocean

Andrew,

Interesting comments about having sail up. We did not, I guess due to the wave and wind direction? The skipper has made regular Atlantic crossings, a couple of times encountering survival conditions, and the 1st mate was an experienced Commercial Yachtmaster, and as a humble, inexperienced day skipper (as were the rest of the crew), I felt no desire (or indeed had the knowledge) to question their practices. Certainly after the really bad wave encounter, the skipper instructed the boat to be slowed right down, which did improve matters.

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[Twister_Ken]

Dutch bridges

Apropos sail vs motor, I was once helping a friend move a Carter 30 from Holland to the UK. 1st part of the trip was on inland waters. The sea area forecast was gales, but we were probabaly experiencing a F6 inland, which was Ok for sailing, and although the waves were no more than a meter or so high they were very short and square.

At one point we had to drop the genny and let the main flog while we motored dead to windward through an opening bridge. Progress was terribly slow and uncomfortable - seemed to take for ever. Probably did for the motorists who were queuing either side of the bridge as well!, As a soon as were through and could bear away to fill the main, everything quietened down (relatively) and we resumed normal progress.

That experience stuck with me as an illustration of the fact that yachts are designed to sail, not motor.

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[bedouin]

Re: Dutch bridges

I agree entirely - on my boat progress is almost always faster and more comfortable under sail than engine. In particular motoring into a heavy sea is very comfortable.

In the conditions nicho described I cannot imagine that I would adopt the motoring straight into wind approach unless I felt it very important to make ground to windward to avoid a lee shore. However all boats are different and I can't really comment on how the boat in question handles.

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[ParaHandy]

Re: Mutually exclusive

RCD short-form floating category: below knees = floating: above hips = sinking

i've always assumed that the whole point of an awb is that you have available to you good and accurate weather forecasts from which you can match the boat's limitations. that seems to me quite reasonable in that the awb is a trade-off of price etc and consequently is not built to withstand such heavy conditions and that should be accepted by the owner .. a sort of gov warning on the packet?



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[pandroid]

Re: RCD Category \'A\' Ocean

Probably in order to sell more boats, even these companies have been going towards the 'flat bottom' shape. The new HR40 is faster, but unlikely to be as stable as the HR39 it replaced. Similarly, my HR36, whilst still being a good sea boat, is not as stable as the HR352 it replaced.

I had a previous IOR yacht that slammed, and I'm a damn sight more comfortable in a blow with the HR, but this is as much a factor of shape as weight. In fact it was the slamming tendency (among other things) that persuaded me to change.



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[Chris_Robb]

Re: Mutually exclusive

<Result, spectacular but uncomfortable>
please add - will lead ultimately to destruction.

Don't know what slamming feels like anymore! - hips below waterline.

It was a truly frightening description by Nicho, and I would not like to think about the consequences of them having to ride out the storm at sea.

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[Robin]

Re: RCD Category \'A\' Ocean

Designs evolve over the years and the influence of racing and cruiser racing designs would have been felt by most builders I think if they wanted to keep the orders coming in. I'm sure there are others more qualified to comment but I do believe the likes of Ron Holland and German Frers were called in to provide a bit more oomph to the range of HRs and others, their designs I would guess would incorporate features from their race boats. Even HRs, Najads and contests have the obligatory waterline length extending scoop sterns these days. Look too at the old offshore racers, they all once had long keels and very heavy construction - and hove-to or took shelter in gales (gales not storms). Along came cutaway forefoots, shorter keels and separate rudders, even unsupported spade rudders. But guess what? NOW they could keep racing upwind in gales!





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[Guest]

Post deleted by danfoley

 

[Chris_Robb]

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

Andrew - you imply in your first paragraph that all boats slam especially when motor sailing. by slamming I am referring to the bone shaking shivvers that one can get. - On my Victory 40 the only time it slams is when its chucked off a wave and meets the wave with the side of the bow section. Otherwise if upright, I have never felt a slam - OK it can be pretty unconfortable - but at least you know nothing is having an undue stress placed upon it.

I assume that if a boat slams then that initial shock will be transmitted to the rig as a V sudden deaccelaration, so imposing far more strain on the rig as well?

Its unfortunate that the RCD misleads the inexperienced - the very people who need the help.

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[Chris_Robb]

Re: RCD Category \'A\' Ocean

Richard
I think the reason for there being many more deeper V'd boats in Cornwall is that they tend to have an older population of boats which were of course built like brick shit houses.

I suspect many of those will still be there when the newer AWB has passed into oblivion.

Which boat did you do the Azores race in?

Chris

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[milltech]

Re: RCD Category \'A\' Ocean

"I cannot but think that without the pressure of a delivery schedule there would have been a better option than motoring into such seas."

Timetables have a lot to answer for. Although I'm in my 60th year I've not yet had time to go cruising proper, maybe I never will, but so long as I have to be places at fixed times it will be on my own boat so I can say, "lets take EasyJet home". Loaded with a full crew, provisions and a schedule to keep there will always be pressures to push on and go, under these pressures I'd rather not be aboard.




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