scottie
Well-Known Member
perhaps we would agree that AC boats are not seaworthy?
Seaworthy or not Seaworthy
- Thread starter peterjaw
- Start date
peterjaw
Well-Known Member
Bouba
Well-Known Member
Do you mean America’s Cup?
peterjaw
Well-Known Member
OK, here are what I get from you.
1. Compare the dead rise if everything other is equal, the more dead rise the more sea kindness.
2. More weight in/close to the gravity center is better, so shaft drive is better than stern drive, stern drive is better than outboard, if all else equal.
3. If possible, dead rise over 20 degree is preferable.
Do I get your points?
By the way, stern drive is not an option for me due to terrible local after service. (All bradns the same.)
peterjaw
Well-Known Member
[2068]
...
I was thinking "Aft Cabin" ... I was wondering if this was about leaving portholes open in a following sea?
Portofino
Well-Known Member
Yes you got them .
I opted out of sterndrive too despite an abundance of service facilities on the CdA , wanted turn key and no known unknown s or is it un known knowns ? Talking bills and down time .
Last edited:
Portofino
Well-Known Member
BruceK
Well-Known Member
Porto? That video just poo-pooed your entire mantra. It does in fact conform to the Formula PC. Please send me your address so I can send you my hat to eat.
Portofino
Well-Known Member
In what way ?Porto? That video just poo-pooed your entire mantra. It does in fact conform to the Formula PC. Please send me your address so I can send you my hat to eat.
To overcome a deeper V drag you need more Hp ( bigger engines ) and to add lift and stability you go with slightly wider chine flats and bigger lifting strip / spray rail width .Adds drag thus more power .Net result is the same as above a few knots quicker burning more fuel in even steeper seas due to the greater dead rise for a given length .
He is right about the steering once mine @ 23 degrees gets going and lifts up it’s arrow straight and often I have to throttle back down to 25 knots to turn tightly .That might be partially to do with the tiny less drag rudders which hang off the stern ( not under ) and theses lift up reducing drag and steerage .
Apart from that as I said its not luck , coincidence , or “ my dad did it this way “ it’s all totally calculated and predictable.
So you either do not understand it all or think Filippo Theodoli Mario Amarti, Ray Hunt Soni Levi , Jim Wayne ( magnum fame ) , Don Aronow , Lindsay Lord had no idea how to make power boats run fast and comfortable in rough weather ?
Which is it Bruce ?
Lindsay Lord being the farther of fast powerboat designs , quantifying the maths and from designing Mafia funded “Rum runners “ in pre war prohibition that beat the officials, to WW2 US Motor torpedo boats used successfully in the Pacific to post war winding up a chair in marine architecture ( the worlds first ) at MIT .
The book s a good read .
.The book is called ” The navel architecture of planing boats “ by Lindsay Lord .........put it on your lockdown reading list.
Magnum Marine - Wikipedia
Last edited:
BruceK
Well-Known Member
Not me, your vid, your narrator. ... And proving his point.... in his boat. I'm not rigid. I'm not so narrow as to believe one size fits all and that there can be many equally effective combinations.
But I will confess the way he shot you down gave me a chuckle. Own goal springs to mind.
Portofino
Well-Known Member
You have lost me Bruce , What are you on about ?
Op s enquiring about ‘ sea kindness “ @ 40 ft ish .
What have I said that , or the guy in the vid that conflicts ?
The maths and physics are constants , alter one thing its has a knock on effect on another .
Amarti also a Roman is said to have copied his mate Theodoli in 1979 with his 38 and the rest as say is history . Why s that shooting my self in the foot .Amarti made them in Rome for Italians .
As I said who cares who’s name is on the boat take your pick ( Anronow , Magnum , Hunt , Itama et al ) the sea kinder ones all follow the same basic mould ( scuse the pun ) and design principles. Dead rise is just one but instantly easy to recognise.
The boat in the vid with its “ near 20 degree dead-rise “ did ok I thought in explaining it all ?
Bit slow up wind but the point was made I thought for cruising which is what the Ops enquiring about .
The deeper you go you end up having to re add stability by widening and enlarging the spray rails , in-fact they morph into lifting strips and you run them to the stern + widen the chine flats .All this add drag so needs more power with oversized engines which adds weight , but means you can carry your speed longer in bigger waves .Obviously burning more fuel , while opposition backs off due to slamming .
Last edited:
BruceK
Well-Known Member
Did you listen to the narrator? His comments about deep V aft and what this boat has. No, I am not about to transcribe his narration. It's your video listen to it.
Whippersnapper
Well-Known Member
Funny how almost every thread has to turn into why my Itama is best.
I think Randall out it best. Modern designs have optimised to what gin palace owners want. More space which means engines at the back, lots of beam with that beam carried well forward. This allows for a full beam mid master but that also means the superstructure is higher to allow for the headroom.
a more ideal design would be a relatively narrow beam to length ratio, engines in the middle etc..., no fly bridge and on and on.
the reality is that for most people and their use of boats it doesn’t matter that much. Few of us are crossing oceans and pick and choose our days. We can all be caught out but the video that was shared has the narrator saying it was a few times over decades of boating.
grumpy old David Pascoe would extol the virtues of the sport fisher and convertibles like the Vikings but they aren't for everyone.
I personally tend to reject options that are too obviously orientated towards low consideration of sea keeping abilities but that’s me. For coastal cruising unless you want to maintain a high speed into a head sea it’s mostly of little consequence As long as you use your head, watch the forecasts etc.. The nature of boating for most people has led to the current market conditions.
there are a very few people who want to put up with the compromises of a very deep v hull pleasure boat when they see the alternatives larger interior space and lower cost (primarily due to smaller engines)
further evidence for the adage all boats are compromises
I think Randall out it best. Modern designs have optimised to what gin palace owners want. More space which means engines at the back, lots of beam with that beam carried well forward. This allows for a full beam mid master but that also means the superstructure is higher to allow for the headroom.
a more ideal design would be a relatively narrow beam to length ratio, engines in the middle etc..., no fly bridge and on and on.
the reality is that for most people and their use of boats it doesn’t matter that much. Few of us are crossing oceans and pick and choose our days. We can all be caught out but the video that was shared has the narrator saying it was a few times over decades of boating.
grumpy old David Pascoe would extol the virtues of the sport fisher and convertibles like the Vikings but they aren't for everyone.
I personally tend to reject options that are too obviously orientated towards low consideration of sea keeping abilities but that’s me. For coastal cruising unless you want to maintain a high speed into a head sea it’s mostly of little consequence As long as you use your head, watch the forecasts etc.. The nature of boating for most people has led to the current market conditions.
there are a very few people who want to put up with the compromises of a very deep v hull pleasure boat when they see the alternatives larger interior space and lower cost (primarily due to smaller engines)
further evidence for the adage all boats are compromises
Last edited:
Portofino
Well-Known Member
I refute your inference.
I have listed a range of boats and a range of designers who designed them .Even gone back to the “Charles Darwin “of the fast planning boat world .
Even alluded to Amarti copied Theodoli .
A vid of the basics I thought well described .
The op like me seem to be living a parallel boating experience.
My first was a S/ Sker portofino 35 , new nothing .Noticed differences in the chop with a delicate wife @ sea ( the Ops daughter ) .
The boat handling or lack of it which impacted on its usability.
I sought professional help and advise and followed it , trusted the brokers .
Then worked back by reading around the subject in amazement of the new ride or “sea kindness “
As I said I have given a huge list above of the boats based on those designers .
Plenty out there @ 40 ft .
Over many more over 40 ft eg .Pershing , Otam , Baia , Sarnico , Nortech , plus many others they have a common denominators in hull design . Op s asking what to look for . Apologies if my enthusiasm to answer the Ops questions seems like something else to you .
Any how constructively what would you suggest and why to the OP ?
Whippersnapper
Well-Known Member
MJM 40z that porto posted up has a deadrise of 18.5º
BruceK
Well-Known Member
And what did he all have to say detracting a steep V aft? He banged on about it for nearly a minute
scottie
Well-Known Member
Exactly but I do realise that I have wandered into the dark realm
peterjaw
Well-Known Member
May I ask a (stupid) question?
If a boat runs stable (relatively) in rough sea, does that mean it is also stable in moderate condition?
What about turning off the engine for angling?
Bowlerhat
Well-Known Member
In the merchant sector Seaworthy is a handy term for insurers to challenge claims. As such, much like the IRPCS, it is deliberately open to interpretation. However, the principle of seaworthiness is one of the vessel being “reasonably fit” for the “adventure insured” (marine insurance act). It is therefore contextual to what you’re doing. The RCD achieves part of this, but is primarily designed to ensure that a reserve of buoyancy is preserved (although manufacturers are responsible for necessary structural integrity during manufacture). On top of this, I would suggest considerations like the condition of the machinery, the number of engines, carriage of life jackets, rafts and flares etc all add up to the overall seaworthiness of the vessel. Crossing rhe channel with a perfectly serviceable engine, flares and life jackets wouldn‘t mean your vessel is seaworthy, necessarily, if the flares were inshore and the engine was 5HP. The qualifications of Masters/skippers is typically considered separately to the seaworthiness of the vessel, although undermanning is considered relevant. There is a responsibility on us as owners/skippers to apply common sense to what we’re doing and add all the factors together to judge whether our vessel is seaworthy. In motoring terms (in the UK) I think of it as MOT + service + ‘the adventure’ = seaworthiness. Then I question my own competence to undertake the adventure! Good thread and an important topic.
