Seaworthy or not Seaworthy

[Sandyshore]

A vessel is seaworthy when it is fit for purpose including crew.
A speedboat going down Southampton water at 50 knots may be designed and capable add 4 people pissed as farts in charge of then its not seaworthy as crew not fit for purpose.
Boat ashore having had skin fitting removed is fit for purpose in that it is ashore. launch it with knowledge skin fitting not replace with a hole in its side its not seaworthy.
Marine law is complex if in doubt suggest contact RYA legal which was the advise given to me .

 

[PowerYachtBlog]

More or less all boats are seaworthy. The important thing is to know your boat and what it can do and how it can do it, and most important the limits they have.

Lets talk planning boats.
A deep Vee hull (20 deg deadrise aft or more) loves following seas, and will basically eat it, head seas in a deep Vee depends very much in weight distribution and how the hull characteristics are forward.
A medium Vee hull (10-19 deg deadrise aft) is prone to have less direction stability in following seas but has the advantage to plane easier in head seas. This last also depending in weight distribution.

For example an Olesinski hull has a deeper fore hull say to a Don Shead Sunseeker, and in most cases an Olesinski Fairline handle head seas better to most Sunseeker's.

Obviously when I am speaking seaworthy I am speaking at seas in 1 to 2 meters waves. (2 to 6/7 ft).
In the end these are pleasure boats when it is rough or very rough it is not a pleasure to be outside, although most boats can take these kind of seas with caution of speed.

Re aft cabin boats they tend to be the most seaworthy of the lot because of the very good balance most of them have.
Both Fairline 36 Turbo, or old Princess 435 are both considered among the most seaworthy boats ever made by the two British boat builders.

The aft cabin note that they told you they are not sea worthy, might come for those who have river designed hull.

 

[jointventureII]

I got absolutely hammered on this in the MCA oral. "Please describe what you understand by the term seaworthy"...

I'd revised the 5 C's of Seaworthy (credit Barry Sadler)
Crew, certification, compliance, construction, contractual (think that's what they were!).

However this wasn't enough for the examiner who wanted to hear "watertight integrity" - which I'd thought was covered within construction.

 

[Bouba]

What about turning off the engine for angling?

Once you turn the key off then all boats rock. Merry Fishers are designed to be stable when stopped but you know how that feels?
But of course there is a solution. Stabilization. It’s expensive, maybe $30,000 to $50,000 (plus of course a generator) but when you consider the cost of a forty foot boat it becomes small change? and your daughter will thank you ??

 

[Portofino]

Top heavy boats rock more , you see some shockers at anchor .The more weight relative up top the more they rock about .
You don’t see many paddle boards rocking .

 

[peterjaw]

Once you turn the key off then all boats rock. Merry Fishers are designed to be stable when stopped but you know how that feels?
But of course there is a solution. Stabilization. It’s expensive, maybe $30,000 to $50,000 (plus of course a generator) but when you consider the cost of a forty foot boat it becomes small change? and your daughter will thank you ??

You are right, all boats rock when stopped , but there are still differences from a boat to another.

I always hear a sentence, "all boats compromise". I would like to know if I can put an
equation between a running boat and a stopped boat.


Stabilizer is an expensive option, and you know what? everything coming to Taiwan will
double or triple the costs when they are in consumers' hands.

 

[peterjaw]

Top heavy boats rock more , you see some shockers at anchor .The more weight relative up top the more they rock about .
You don’t see many paddle boards rocking .

So, again, this is another advantage of shaft drive boats, because they have
engine arranged low and close to the GC.

 

[Portofino]

So, again, this is another advantage of shaft drive boats, because they have
engine arranged low and close to the GC.

Yes the nearer the centre of gravity to the meta centric centre , the centre of lift the more stable it is at rest in roll and pitch . Static stability.
Helps when moving too when dynamic stability comes into play .
Too much weight aft and they can end up porpoising and require a lot of trim adjustments.
Triple sterndrive Superhawks I have seen end up slowing right down in a big head seas to D speed because of this .

What a lot of sterndrive boats do is have short waterline lengths ( or pointy bows ) to move the centre of lift aft nearer the fixed mass of the machinery .
They then pivot behind the helm position and the shorter WL L means a good 1/3 rd of the forward sections the deeper dead rise is redundant when planning so a tendency to slam on the rearwards shallower sections comes into play .
Obviously if like a Donzi or Magnum the transom dead rise over 20 degrees actually 24 , then they ride better .

With a central machinery mounted set up like those I mentioned early the helm and sitting passengers are right over the pivot point so you get a more comfy ride in a given sea state than the rear weighted biased boats .
Additionally designers do not need to decrease or reduce the water line length so they have a longer fwd wetter area , run flatter and the sharper more Fwds sections are available to cut through more .The bow 1/3 rd if you like cuts through.
Of course all boats can be trimmed when running , but not all actually need a lot of trim .
Indeed it’s arguably true that boats which require bags of trim when running ( in all sea states ) are in fact out of balance hulls
You see a lot in yards with huge fixed trim appendages hanging off the transom, between the rudders as well as the lateral movable tabs .The fixed one looks like an afterthought.

So a low it’s said under 4 degree running angle is better for ride as the Fwds sharper bow sections are indeed actually useful .

 

[JB]

Top heavy boats rock more , you see some shockers at anchor .The more weight relative up top the more they rock about .
You don’t see many paddle boards rocking .

The Nordhavn's flopper stopper is the best thing they ever did to counterract the roll ! It virtually eliminates the rolling motion

 

[Deleted User YDKXO]

Funny how almost every thread has to turn into why my Itama is best.

As predicted here Seaworthy or not Seaworthy


Maybe we should all just agree that Itamas are the best boats in the world and acknowledge that all other boats are not worthy to lick the boots of an Itama?

 

[BruceK]

Hell no, he scored an own goal. From now on medium V aft rocks. I shall dine out on it for a long time to come.

 

[Bouba]

From now on medium V aft rocks.

I thought they don’t rock?‍??‍???

 

[Portofino]

Hell no, he scored an own goal. From now on medium V aft rocks. I shall dine out on it for a long time to come.

What own goal ?
The list of great hull designers ( race winners offshore) were wrong about deadrise ?
For the benefit of doubt heres another reputable 23 degree boat btw for your perusal. .
Why did they do it Bruce ? What are trying to achieve with the deep V ?

Boston Whaler 380 Outrage (2020-) | BoatTEST

This would be a great choice for the Ops needs or a bigger one , based on engine serviceable and legendary “ sea kindness “ and seaworthiness and the hobby fishing side .

 

[BruceK]

Maybe they found religion? Hell I dont know. Surely you cant be claiming all the hull designers of the remaining 95% plus boats were complete charlatans? Or maybe they were sucking on the exhaust gasses?

 

[Portofino]

Maybe they found religion? Hell I dont know. Surely you cant be claiming all the hull designers of the remaining 95% plus boats were complete charlatans? Or maybe they were sucking on the exhaust gasses?

No of course not .Show me where ^^^ ?

Feels like it you making a fuss ?
It is what it is , read the book .Less dead rise means as already said less horse power less weight because of the increased lift without as much drag so more speed for a given lower and cheaper engine set up .
All well and good for the “95 % “ until the sea state starts getting up .They end up throttling back dropping off the plane loosing dynamic stability .They have to because they slam .

If you see the BW blurb ^^ it’s can keep its speed so much in a chop that if I was to get big air it has a soft landing .
So in normal or your 95 % ( not the airborne seas ) it’s just a better more comfortable ride .
Seeing as this is one of the OP s prescriptions ( the daughter’s “sea kindness “request ) it would be silly not to intro dead rise et al into the equation.
Seeing as many boats theses days are sold as floating camper holiday homes , you know mid cabin s fuller bows , blown up hulls mid section for interior vol , price sensitive competition wise etc .Often if you kill the dead rise flatten it off at the stern you get get away with smaller cheaper lighter engines and keep the project on budget to sell it .
The FL 62 GTO springs to mind . Weedy engines and slams easily in boat tests .Nice to look at and sit on at the dock .
Trip to Corsica from Cannes , no Thx .But if it sells fine .Just recognise it for what it is .

That builder in the vid has unusually resisted the floating holiday home temptation and stayed focused on the hull form to a point .It’s an IPS rear weight thing on D6 370 s Thats his compromise, which restricted him to 18.5 degrees at the transom .
But a quick boat and fuel efficient it’s claimed ?

Windy s are the best sterndrive sports boats in terms of hull shape , dead rise , ability to run in waves .

Thing is you can get caught out in unplanned seas even with the best met .
Suspect Taiwan is like that so tea tray flat stern boats are probably not a wise buy ?

We never HAVE to go at D speed , sure slow down upwind in a chop to 22/24 but never have to drop off and end up bobbing about .That’s what a deep V does it takes the slamming out of the job .

 

[Portofino]

I got absolutely hammered on this in the MCA oral. "Please describe what you understand by the term seaworthy"...

I'd revised the 5 C's of Seaworthy (credit Barry Sadler)
Crew, certification, compliance, construction, contractual (think that's what they were!).

However this wasn't enough for the examiner who wanted to hear "watertight integrity" - which I'd thought was covered within construction.

Wasn't gonna mention “ watertight integrity “ for fear of being accused of “ Itama best boats “ but seeing as you have raised it , in for a penny in for a £ etc and folks are already accusing me anyhow .For sake of completeness.
Amarti made them to order a few where for commercial guest transfer Naples / Capri like mine and have water tight bulkheads either side of the ER ,So three sections as the ER is the middle .

So if you were to clip an underwater object and rip off the p bracket or what ever they still float .



The bilges on the Sunseeker were all interconnected and services just run through holes or under the floors .
So a hole or bust seacock anywhere ( depleted batts ) would have sunk it .Well built but no water tight compartments.

 

[BruceK]

Feels like it you making a fuss ?

Moi? Naww. Just giving you the opportunity to bash the Lindsay Lord bible to these heathens. Think of me as the studio heckler.

 

[Whippersnapper]

And what did he all have to say detracting a steep V aft? He banged on about it for nearly a minute

I know. I found a 30 minute video with the designer talking ab

You are right, all boats rock when stopped , but there are still differences from a boat to another.

I always hear a sentence, "all boats compromise". I would like to know if I can put an
equation between a running boat and a stopped boat.


Stabilizer is an expensive option, and you know what? everything coming to Taiwan will
double or triple the costs when they are in consumers' hands.

in general boats with the best sea keeping and dynamic stability will rock more at anchor (form stability). That is to say that relativelymnarrow deeper Vee boats will rock more easily than a wide shallow Vee vessel.

 

[Mr Googler]

Centre Console you say! Outboards are better than naff old shafts.....but only when you have 6

 

[BruceK]

Centre Console you say! Outboards are better than naff old shafts.....but only when you have 6

Do keep up. Itama is out, Formula is in. The Man said so

Look what the did to the PC ?