the thought of huge waves tipping the boat just scares the **** outta me|||A combination of shape, strength and careful positioning of the draft and centre of gravity is what stops a boat from becoming bowled over by the waves - and if done really well, even getting it back upright again if it does become overwhelmed. (See film).
Boat shape certainly compliments this combination and different shapes have different characteristics.
Probably the most seaworthy designs in the world are the cutters of the US Coastguard.
At the mouth of the Columbia River on the US West Coast, nature has contrived to produce one of the roughest bodies of water in the world.
The Coast Guard has found over many years of experience and design that the best type of boat shape for use in these waters is the double-ended V-bottom type, with deep forefoot and high, flared bow, which has subsequently evolved there.
It is a combination, from bow to stern, of all the types of hull-shape, with a great deal of fine tuning, to produce a type of vessel that puts extreme seaworthiness at somewhere near a pinnacle.
The advantage of the pointed (also rounded) stern is to reduce the tendency of broaching in a quartering sea. This means to be swung around and out of control by the force of the following wave:-
"If the forefoot is too deep and there is no skeg, it may be impossible to steer such a boat. When a boat of that profile runs down a wave, she buries her nose in water and her stern lifts high and clear 鈥?[lifting the rudders and propellers clear, and thus making them useless] 鈥?Around she goes, pivoting on her deepest point, the bow. Next step in this tragedy is violent rolling in the trough of the seas. Capsizing or swamping is the last act.
If a deep forefoot is desired, then the profile must be balanced at the stern with a deep skeg and rudder. 鈥?Every line must be a compromise" 鹿
[Typed in from the book, below. Not copied and pasted.]
So good was this design that the resulting vessel was also used by the RNLI (Royal National Lifeboat Institution - the UK national coastal rescue service) with a number of boats being purchased from the US Coastguard.
The boats were signified as the 'Waveney' Class of lifeboats here in the UK, with the numbers beginning: 44 001 / 2 / 3 etc.
Here is some super film, and pics, of some of these vessels (together with their earlier and later incarnations) on station, possibly at Morro Bay, or the aforementioned mouth of the Columbia river, USA:
Lifeboat Cutters:
http://www.youtube.com/watch?v=vesgFkgP0鈥?/a>
Is this good enough performance to set your mind (and your bowels!) at rest? ;-))
The 'Waveney' features quite a bit here, (spot the 44 on the bow) but the best view is at 2. 05 minutes into the video (towards the end) cruising along in flat calm water with shore in the background). Also in calm, 17 seconds in, on the right.
In really rough conditions, seaworthiness is very much a function of the person at the helm, ultimately.
____________________
鹿 Skene's Elements Of Yacht Design. Revised by Francis S. Kinney. Adam %26amp; Charles Black. London. 漏 1927, 1935, 1938, 1962 By Dodd, Mead and Company, Inc.
-|--)|||Double-ended V-bottom type, with deep forefoot and high, flared bow. Shape was the question, that is the answer. (Unless you are getting into survival torpedoes and submarines etc. Which you weren't.)
Many thanks for the valuable vote, kind voter.
Much appreciated.
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|||To keep the waves from tipping your boat you only have to keep the boat pointed into the waves. That is the first rule of seamanship. A boat that is taking the waves on it's beam will be capsized if the waves get big enough.
You need to take a boating course if you are this unsure, or you are going to find yourself in trouble.|||keeping the weight below the water line as much as possible works better than the shape, ship owners often times take a boat that is built for a specific task, and usually add tanks or winches or things that were not part of the engineers plans when the boat was built, IN almost all cases of a ship capsizing its usually when it has a full load of crap pots ABOVE DECK IN A HIGH WIND, LIKE THOSE BOATS ON THE SHOW in alaska, If you build your boat right, and keep the weight low and dont have a high profile above deck it will be tough and durable and steady in high waves and a big wind.|||Fact is (and you can ask any Marine Insurance Company to verify this) 7 out of 10 boats sink at the dock, 3 out of ten are involved with alcohol related accidents, and only 1 out a 100 ever sink while underway - and 9 of 10 of those that do could have been avoided with preventive maintenance, and the other .01% are disputed to have been avoided (or not) by the skipper paying more attention to navigation and or weather.
Truth is, if you plan it right, you can sail (or power) boat around the world in 95% perfect or near perfect weather. It is like everything else, what you hear on the news is always the bad news.
While your dream is great one... You need however, to rethink your vessel, and the reason for your boat requirements. 20 to 80 mph on the open sea is simply not realistic. It is not even attainable with any production offshore vessel.
For example: You may have seen the news on "Earthrace" - the "Earthrace" was an amazing powerboat that currently holds the record for a powerboat to circumnavigate the globe. It recently set the world record for powerboats around the world at 60 days, 23 hours, 49 minutes.
This vessel cost 3 million (us dollars) to build and it cost $368,000 (us dollars) in fuel to circumnavigate the globe. It in fact was designed and built for a top speed of 40 knots (that's only 46 mph) and it was going for a world speed record. (See why your 80 mph is unrealistic?)
What did they prove after spending all that money on the boat's design, construction, and fuel cost?
Only how ridiculous %26amp; foolish it really was... As the world's very fastest circumnavigation is 57 days, 13 hours, 34 minutes - (almost 4 days faster then Earthrace) and is held by a sailboat averaging only 15 mph. (Kind of like the tortoise and the hare story here, huh)
So... What I am saying is the dream is a good one... I encourage it. The vessel however needs serious rethinking.
On the open sea, when it comes to crossing the ocean... the right vessel will get you there comfortably %26amp; safely... you don't have to worry about tipping over - least not in a true offshore vessel and good common sense. But the ocean herself will determine your speed much more so then you or your boat or your boat's engines.
My son and I have been around the world once together... we spent an additional 5 years sailing around "in" the world together... and we both have an accumulated total of more then 60 years of boating. We still laugh at ourselves and others when we hear talk of boaters wanting to cross oceans with vessels having the best speed - because (sail or power) when it come to the open sea the "right kind" of $20,000 sailboat can get you there and back just almost as fast and just as safe as any $2,000,000 boat with high-tech sails or super-charged engines.
Now you didn't mention the "purpose" of your boat... But if it is for crossing oceans and sailing off to Paradise or on around the world... I would much rather have all that money in my cruising %26amp; voyaging bank account so I can stay out longer... then have a big shinny boat with big shinny boat payments and gargantuan fuel cost, and no money left over to take time off to go anywhere.
John
My Dad always told me that God gave us dreams with the wish for us to live them. And while we can't control life's changing winds... we always have the ability to adjust our sails.
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