AVS explained

[Happy1]

I am trying to work out the AVS for my vessel, that is the 'Angle of Vanishing Stability', if my research is right then this would be the angle of the heel at which a boat will invert rather than right. A conventional 15m motor cruiser has is around 80 degrees, which compares to yacht of 115 degrees. How would I work out my AVS? Part 1 of the stability standard ISO 12217 covers 'the stability and buoyancy on non-sailing boats of a hull length greater than 6mtrs' mine falls into this category, just. These figures are used in the assessment of the design category A (Ocean) category B(offshore) and category C(Inshore) . I am category C but wander if I can ever become a category B. I know that it addresses the risk of downflooding (water entering non-draining parts of the boat), The size and position of openings in the hull and their height, the gunwale height, and when heeled to an operation angle are given limits. Can anyone help ?

<hr width=100% size=1><font color=purple> "You only see what you recognise, and you only recognise what you know" <font color=purple>

 

[BarryH]

Don't really think you need to worry about that too much. You've got a wide beam yank boat for wide beam yanks. If you get it over that far the your anal nerve will let go before the boat does!

Just for a comparisson, a certain member on this board had mu boat running on its gunnel at around 20 knots. My beamxlength ratio is a lot smaller than yours ie, mines slightly longer than yours and a bit narrower in the beam. Also, you have a hard chined boat. So it will not go much passed the angle of the deadrise. You'll get the feel of the thing once you start using it.

Hull design is a science in itself, so don't go into it too deeply as you'll just get lost in all the maths, hydrodynamics and put yourself to sleep......yawn, thats me done.

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[longjohnsilver]

So who's been reading their RYA mag then? I got about 3 paras into the article and got totally bored.

And that was the only thing in the whole mag about motor cruisers. Boring, boring, boring......................................

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[tr7v8]

Ummmm, someones been reading the RYA mag haven't we!
The AVS for your cuddy cabin should be greater that a 15M cruiser for the simple reason that it has very little cabin area. It' the flybridge that makes it 80deg.
The other issue will be things like engine ventilation which will flood quite early on.

Jim
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[tr7v8]

Yes that article and a few piccies!
Makes me wonder if some of the flack they took around Xmas got through,
still won't be renewing my membership anyway.


Jim
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[hlb]

Happy 1 You have bought a play about boat. It is not intended for serious or even half serious sea conditions. You will have inumerable other problems before you get even near to turning the boat over. Swamping is a much bigger issue. Have you thought of that!!

<hr width=100% size=1> <font color=blue> Haydn

 

[Happy1]

I am reading it at the moment but I CAN'T understand it. I know I am Cat C and I am classed as Inshore, my insurance company gives me 25 miles coverage, is that inshore? We have discussed the Cat codings in a previous thread, but this article seems to try and explain it. I wanted to know if mine can be upgraded to a Cat B, or is there nothing you can do. If you understood it or anyone else, I would appreciate some help, which is what I was after /forums/images/icons/wink.gif

<hr width=100% size=1><font color=purple> "You only see what you recognise, and you only recognise what you know" <font color=purple>

 

[Happy1]

Yes I have thought of swamping, the RYA article on the AVS covers this but I am confused, to get a Cat B code you should ahve a quick draining cockpit, I am Cat C so does that mean I DO NOT have a quick draining cockpit and could drown? Can I make it a quick draining cockpit, that is the question.

<hr width=100% size=1><font color=purple> "You only see what you recognise, and you only recognise what you know" <font color=purple>

 

[Happy1]

SO WHY do they send out stuff frightening the life out of you because you are the lowest Cat C, meaning you have crap drainage and could flip over? I wish I had not subscribed now, I won't sleep tonight now!! I will have to get it made a Cat B at least don't you think. Funny thing is I asked the RYA about these Cat codings last week, but never got a technical answer, all I have is the RYA mgazine I just opened.

<hr width=100% size=1><font color=purple> "You only see what you recognise, and you only recognise what you know" <font color=purple>

 

[Happy1]

I think you are right John, I have just finished it, even most of the adverts are raggies orientated. Why did you tell me to join? /forums/images/icons/laugh.gif

<hr width=100% size=1><font color=purple> "You only see what you recognise, and you only recognise what you know" <font color=purple>

 

[tr7v8]

You need to understand one thing, as explained in the article (not very well) the RCD rules are really written for Raggies not power boats of any sort. Hence the fairly wooly bits that the RCD refers to, like cockpit drainage. Your more likely to find rocking horse droppings than capsized power boats. The reason being is simple that the vast majority wouldn't get caught n weather that bad, they'll either out run it or have not gone out. The only ones that do go out re the Nelsons, Lifeboat type designs which are not hard chine sports boats. Watch the RNLI Videos of them testing the big Lfeboats and you'll see the AVS point seems to be in excess of 100 Deg. The cabin etc gives the bouyancy for them to roll upright again. BUT and it's a big but they have sealing air vents and a shed load of other things that ensure that A. water doesn't go in and B. the engines can be restarted.

Jim
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[Happy1]

Thanks for the explanation. SO WILL I BE SAFE in the river Medway, that's all I need to know. Perhaps I should have bought a second hand lifeboat /forums/images/icons/laugh.gif

<hr width=100% size=1><font color=purple> "You only see what you recognise, and you only recognise what you know" <font color=purple>

 

[tr7v8]

Have a look at
<A target="_blank" HREF=http://195.224.113.154/disposals2/ItemSpec.asp?ItemID=18898>http://195.224.113.154/disposals2/ItemSpec.asp?ItemID=18898</A>
ARUN CLASS EX LIFEBOAT RNLI - HYMAN WINSTONE NO.1067
Yours for £ 130K plus VAT ONO.......

Jim
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[BarryH]

So basically your going to take on the powers in Brussels and argue the toss over the category that has been given to a boat that was never really designed for the waters of northern europe! Right yeah OK.

The thing that your not using here is your discression. If it looks like a mailstrom out side the marina with whitehorses foam streaked water everywhere are you going to go out because the category given to your boat says you can!

Grumps, learn to walk first, you can run a 3 minute mile next year when you have a few miles under your belt. Sorry if the replies are getting a bit flippant, but erm....

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[Happy1]

EXCUSE ME BARRY !!! I am only doing this research so I can follow you to the bloody IOW trip, I am planning for that trip now. I would never go so far in such a small Cat C boat, if I am going on this dangerous trip I want to ensure my vessel is capable. Mine will be the smallest one to make this treacherous trip. OK you may be holding my hand going over, but IS my boat capable of going MORE than the 3 miles out that I should?

<hr width=100% size=1><font color=purple> "You only see what you recognise, and you only recognise what you know" <font color=purple>

 

[hlb]

Of course if you do get a wave over the top. All your safety gear will be as much use as a chocolate fire guard. I on the other hand have had many waves over the top and have at one time cruised comfortably with three foot of green water over the deck.It was quite interesting watching the window wipers!!! But can you go into submarine mode. and just plod along. With water all around and above. Only the radar scanner and GPS airial above water. Ten feet up! This was only on a supposed leasurely cruise of 17 miles Salcolmbe to Plymouth. Will the window screen hold with 10-20-30 Tons of water hitting it!! Mine has. We have discussed the fact, that once your in the sea. There is not much going for you. life rafts are no where near as good as a well found boat. Is it self draining?? Or does it fill up like a bucket?? We need to get down to the nitty gritty of safety. Arials, GPS Arials, Radar.. Ten- Fifteen foot up from sea level. Or how you going to see where your going in this sea thats going to turn you over? How you going to comunicate with others. The waves are higher than you!! So all equipment is useless. You would not buy a Relient robin and try to turn it into F1. It wont do it.
Dont know if your serious. or trying to wind us up. So have refrained from pointing out the obvious till this point. If you want to go to sea. Trade it in and get a propper boat. IMHO.
Don tin hat and await the flack............./forums/images/icons/laugh.gif

<hr width=100% size=1> <font color=blue> Haydn

 

[Happy1]

Haydn. I don't know sometimes if you deliberatly try to wind me up. All I want to know is will it float. I don't have wipers but have considered getting them, but the screen is curved so I might as well have chocoltae ones, as you would say!! Is ther anything I can do to my boat (forget the safety gear) structurely to make it more seaworthy. I can assure you if it rains I will be going in, I have bought rainex for my windscreen though. I will contact Glastron to get the breaking stress limits of the screen, I did not research that, but I only have a camper canvas on top so that will be like a chocolate cover, I may as well had a bloody chocolate boat!!! So have a I bought a load of sh.t. No decent drainage, I was suspicous why mine had nice carpet in the cockpit when you would think it would be plastic to let it drain out, I may have to install some better bilge pumps, I also want to test the seals on the cockpit door. apparently the Cat C is OK for F6 and <2mtr waves, anything over that and I am dead meat. Why oH Why did I not stick to something simple like caravaning? Anyway I am doing a risk assessment for the IOW trip, and just at the right moment this RYA mag popped through the door, just made things more complicated.

<hr width=100% size=1><font color=purple> "You only see what you recognise, and you only recognise what you know" <font color=purple>

 

[BarryH]

Ok, so my boat was built before all this RCD gumph was brought into play. So my boat has no RCD rating. Thats NONE, ZILCH, NICH rating. Its 21 feet long 7 feet wide. Its got a 15 year old wheezzing Volvo lump. Its been to france its travelled the length of the south coast, its been up the west coast, its been round the east coast. Through the dover staright more times than I care to remember. It came back from france in a force 5. I was crapping myself. Its been to Italy. Its been to Ireland. Its run along the south coast of ireland. Its been to the scilly Isles. Its brought me through weather that all the whistle and bells yank boats would have shaken themselves to bits in. BUT IT HAS NO RCD RATING, does it make it no good for the conditions!

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[BrendanS]

Yes, your boat can go more than 3 miles out and many smaller than yours do so everyday. They only do it (if they have any sense) with experience of their boat at sea. Then you know what conditions it will tolerate, and what is safe. First time you go out in what seem to you at the time as rough seas, you'll be praying to get home, next time you'll know the boat can take it, and be able to take rougher water with more confidence. After a year, you'll wonder what all the fuss of the first voyages are about, and start thinking about what sort of boating you want to do.

AVS is a waste of time for motorboats, as already explained, a motorboat doesn't really fit this raggie measurement. Raggies have big sticks above, with sails on and big keels below ,and are designed to heel, often with a large section of the side completely underwater. Many are designed to be able to completely invert, and still come up again. Motorboats don't heel (much) and those that get that much water onboard typically sink.

Trail the boat to the Solent and launch there, that will be more than enough thrill for you in your early months of taking your boat to sea

While on CE, total waste of time, they mean nothing in real terms, and most manufacturers self certify

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[hlb]

No. Dont think at is wrong for conditions. It's just that you know what your doing!!

<hr width=100% size=1> <font color=blue> Haydn