Power boats in rough weather

[rogerroger]

Can you guys please enlighten me...

I've often wondered how power boats - say a 36-40 foot, twin engined planing fly bridge cruiser for example - cope in rough weather, largish waves etc. I'm not talking storms - but the sort of weather us raggies wouldn't put out in intentionally.

Some of the large sex-machines look like they've got very little below the water line and plently above it. How stable is this ? If one ever capsized is it game over?

... or (as I suspect) - does the speed of such beasts mean you can just get to the nearest port ahead of any weather while us raggies check our life insurance and wills?

I'm sure some of you have had to come back across the Channel for example in some weather when there's been little choice?

Tar.


Roger Holden
www.first-magnitude.co.uk

 

[BarryH]

Couple of schools of thought on this one. You can tack into the head sea, lessen the force of the waves. Play with the throttles to keep the nose up to meet on coming wave or sit on the back of a wave. Or as you say, beat the weather back to port.

Thats what the "books" say anyway. but I'm sure someone else will have their own ways of dealing with it

Wha'dya mean "I'm always playing with this engine" its the only way to get it to run!

 

[stewart]

As far as I can see the problem comes down to this - planing boats need some speed to handle properly and get on the plane, typically 15 knts plus and at speed in rough weather it can get very unpleasnt with slamming etc, but the other alternative of not being on the plane in rough weather is far worse, boat just gets thrown all over the place. Best solution seems to be check the weather forecast first and stay home if it's not good.......

 

[Medskipper]

Of course the best plan of action if very heavy weather is forecast is to stay in port, or make for your second choice port of call, just like any yachtman really!

There are of course the fully planning hulls and the semi displacement hull, I have had both and I have to say around our coast lines the latter is better in heavy weather as it give a far more comfortable ride in bad conditions, having said that its unlikely to be as fast a boat as a fully planning hull but most semi displacements will do 18-22knots which I feel is quick enough for a serious cruising motor boat man!

Barry


I just want to retire with my boat to the Med!

 

[Deleted User YDKXO]

Although I think I'd rather be in a sailing boat in a real blow, dont assume that planing power boats are dangerous in rough weather. Firstly, consider that many new boats are delivered to their owners by sea and delivery skippers run tight schedules so not going because its blowing a bit is not an option. Secondly, whilst power boats have a lot up top they have one or two large lumps of engine below plus a load of other machinery and, of course, a hull with a much heavier lay-up than your average yacht - so there's a lot of weight low down. Thirdly, even at relatively slow speeds, planing hulls exhibit hydrodynamic lift which also assists with stability. Fourthly, having good speed allows the helmsman to steer/throttle around larger waves and to run with a following sea - in fact running at speed in a following sea is an exhilarating experience in a well found planing boat. In a head sea, the hull will slam at speed but slowing down to displacement speed is often quite comfortable because most planing boats have very fine sections forward. Not only does having speed allow you to avoid weather but it also allows you to be at sea in the most favourable conditions, for example timing your arrival in overfall areas for slack water.
Obviously, the big difference is in a capsize situation where a yacht will self right and a motor boat will not but, having said that, you dont ever hear of motor boats being lost at sea except for very small ones
I guess most of the motor boat owners on this forum have been caught out in rough weather and we've all lived to tell the tale

 

[rogerroger]

Thanks Mike

That all makes sense, being a raggie I'd not really thought of engine contributing to stability.

I certainly wasn't assuming planing hulls were dangerous in rough weather - just genuinely intrigued by how the boat / skipper deals with it.

My other half would love it if I got a stinkie - being able to do 20 - 30 knots to the nearest port when things kick up instead of the usual "well we're making 4 knots dear, which isn't bad to windward - you'll only have to put up with this for another 8 or 10 hours"!

So fair to say maybe - you wouldn't want to be caught with a heavy beam sea (true in a sail boat of course) - and if you had to bash into the waves and wind it wouldn't be a lot of fun? but you'd be OK?

Roger Holden
www.first-magnitude.co.uk

 

[tcm]

beam sea isn't too bad, and actually needs confident handling to get the boat on the plane and bomb al;ong - otherwise the boat rocks badly over each wave. Following sea is indeed exhiarating, and needs careful matching of speed to wave "speed", to avoid too much sitting on the back of the wave (where the boat is attempting to go uphill and can't plane) and perhaps (if clear sea) surfing the front of the wave with admittedlt not a lot of steerage. On the nose is worst, f6-7 or more means roomfuls of water over the bow, and 5knots before it starts slamming. Not much fun, but even in large seas that the boat I've never had a time at which I thought we'd sink or capsize.

 

[Deleted User YDKXO]

Personally, my biggest concern would be losing all power and the boat would then sit beam on to the waves which would be very uncomfortable indeed in a big sea and a potential capsize situation. Actually driving in a big beam sea is not too much of a problem as, depending on the boat, you can steer around the higher crests.
Bashing into the waves is no fun in any boat but, in actual fact, it's probably the safest condition
I would have thought that changing from a 4 knot yacht to a 30 knot stinkie would be too much of a transition and you'd definitely lose all your sailing friends. Why not consider a semi displacement boat which will still give you a 15-20knot speed capability which is plenty. If you want something traditional and you've got loadsamoney, something from the Nelson range is often the route ex sailors go. Otherwise, the Scandinavian builders such as Nimbus, Saga, Marex are worth a look. In fact, I understand Nimbus get lots of sailors making the change and even take yachts in p/x

 

[Bergman]

I may be talking rot (again) cos I've no experience of power boats, but I don't think I'd fancy having a big sea up the blunt end of some of the modern looking ones.

Big cockpit, patio doors all look very vulnerable, especially with engines and electrickery underneath.

Take the point about stability, certainly true of lifeboats which self-right despite (or more correctly because of) lots of boat above water, but they have watertight hatches and sealed internal compartments.

The local fishermen all try to head into a big sea, keeping speed down to just enough to steer round worst bits - or so they tell me.

The motor boats locally rarely seem to go out even in good weather so never had chance to see them perform in iffy stuff.

 

[MapisM]

It depends: how rough is \"rough\"?

I mean, there is a limit for any planing boat, above which planing is just not feasible.
And if you reach that limit, life aboard a planing boat gets quickly unconfortable, to say the least.
Of course, this limit depends on the size mainly, and to some extent on the hull.
But in my experience, a displacement boat forced by the rough sea to cruise at 7/8 kts instead of 10/11 can still provide reasonably good confort and safety, whilst a planing boat of similar size cruising at the same 7/8 kts instead of 25 or 30 is much more shaky and unsecure (or at least, it gives that feeling).

 

[rogerroger]

Thanks for the tips - but I'll not be hanging up the rags for many years yet!

Roger Holden
www.first-magnitude.co.uk

 

[Deleted User YDKXO]

Actually, planing boats have a lot of buoyancy aft and, with no keel, they're not as likely to broach as a yacht but I suppose it depends on how you define a big sea. Certainly, if you had waves breaking into the cockpit, I guess the patio doors would'nt last long but the cockpit would be self draining and, on a shaft drive boat, there's usually a bulkhead between the cockpit bilge and the engine space
I can only speak from personal experience. I was once caught out in a following sea in a Fairline Turbo 36 off Brittany in a Westerly Force 8 (thank you, SWMBO) which had been blowing for a couple of days. Once I got over the terror of looking behind and seeing waves considerably higher than the flybridge on which I was sitting, I soon found that the boat handled fine at its normal cruising revs although the speed varied between 10 and 30knots depending on whether the boat was sitting on the back of the wave or the front. We actually became so confident that we pushed on beyond our original destination and did about 50miles altogether. Not a F10 in the Southern Ocean, I admit but I met a yottie the next day who was out in the same conditions and he could'nt believe that we were out also

 

[Deleted User YDKXO]

Sounds like 'er indoors has got the right idea, though

 

[adarcy]

Dag Pike did an excellent book titled
Fast boats & Rough Seas or Fast Boats & Bad Weather
or something like that.
Excellent book detailing how to drive in big bad seas. More applicable to lighter
planig boats - our 14 ton P45 doesn't snap its bow up or down quickly with the throttle like our 29 ft boat did. In fact, it just seems to mash through anything.

I also rekon the boss has the right idea.

Anthony

 

[Guest]

Whilst in a secondhand bookshop in Brighton, a few years ago, I came across a fascinating book written by the very well respected journalist, navigator and recordbreaker Dag Pike entitled (almost coincidently) 'Power Boats in Rough Seas'.
It may no longer be in print as my copy (now) was published and printed back in 1974.
It is well worth a serious read, and as you would expect of Dag Pike, contains an incredible amount of in depth research and detail. ISBN 0 229 11523 3. For anyone interested in acquiring a copy, or maybe borrowing one from the local library.

A very interesting debate!

Peter.

 

[milltech]

"in fact running at speed in a following sea is an exhilarating experience in a well found planing boat."

I wouldn't recomend it in a Moonraker. She was my first boat big enough to sleep on and a sensible first boat since so many were made. But with a following sea she was constantly try to broach, it was not a pleasent experience.

John

 

[Deleted User YDKXO]

Then try it in any Olesinski designed Fairline or Princess, Turbo 36, P45 or any of his modern hulls. Correct me if I'm wrong but does'nt the Moonraker have quite a substantial keel? If so, that certainly would'nt help as the keel gets pushed sideways by any wave that is'nt dead astern

 

[milltech]

I don't think so but I sold her about 1984 and can't remember. She lives at Haslar these days, "Yellow Moon". She had an "interesting" time in St. Vaast during the 92? hurricane.

I continued crewing her sometimes with the man who bought her from me because his wife would meet him off a ferry but would cross. We had a wonderful thrash back from St. V in a 5/6, spray with rainbows, sunny day, leaping from crest to crest, just enough weather not to have to ease up. Trifik

John

 

[Guest]

Hmmm....just returned from Plymouth trailing a Cruisers Int 224 Holiday. Deep vee planing hull, V8210hp engine, nearly sh*t ourselves in Plymouth Sound going across a very slight beam sea....planing at approx 25knots, suddenly lurched as if going to tip over....couldn't right it immediately....no time to adjust trim. Cured by slowing down to displacement speed...help!!!

 

[hlb]

Very true. Once did 90 miles up the Bristol Chanel with a f7 chasing me. Boat loved it. Just keep the power on. Came back to Plymouth last week with a F?? on the nose. Had to slow down to 9 knots at times, but still going twice as fast as the yachties. Had to get out the captain Tullys when I got back though. Broke every blummin window seal in the screen.

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Haydn