Is Semi-Displacement Hull better than Deep V Hull ?

[ShaneAtSea]

Er Nope no deep V ^^^^ .
More like low V not even medium.
Theres no info i could find in the two trials of the 58 .Every other number except dead rise .
But the big marketing BS alarm is the IPS ….it’s gotta be flat at the back , the mounting pads for the pods .
Otherwise if you were to rip out my motors in my 23 degree deadrise and install VP IPS on that degree of V the thrust vectors when turning would roll the boat ….badly .Marina manoeuvres , parking it would tip everything off a table and open lockers etc .
You know the ECU / joystick decides just to swing one pod and give it revs , say the wind blows etc .

Sticking pods on deep V or more accurately a medium v ( below 20*degrees ) facing straight Fwds works .
But once you start the fancy parking malarky the steep inclined plane of un toward thrust vectors takes over .

Aside the gear boxes would lean inwards and nut each other in the ER in any other than a pretty shallow dead rise.Low V .

Floating apartments is a more accurate term .NOT deep V that’s a hilariously term .

Deep V, Medium V, Low V, No V

I was just talking about style of boats in my own layman terms

Im sorry if i wasn't using the correct technical jargon but i was trying to just give a jist of what i meant

But i keep learning and this forum definitely keeps me on my toes

 

[petem]

Deep V, Medium V, Low V, No V

I was just talking about style of boats in my own layman terms

Im sorry if i wasn't using the correct technical jargon but i was trying to just give a jist of what i meant

But i keep learning and this forum definitely keeps me on my toes

Conflating hull form and boat style is a very bad idea.

There are many planing boats that are very comfortable for extended cruising. Conversely, there are may displacement boats that you wouldn't want to spend more than a night on.

"Expedition" or "Trawler" style are more descriptive of styling.

 

[petem]

Also, for what its worth, some people regard Semi-D as the worst of both worlds, neither good for planing nor good for displacement speed cruising.

As Scottie said, "You can't change the laws of physics".

 

[Portofino]

^^^ You really have to test drive them in the conditions you are gonna. / plan mostly using .
Just like a car really .
Try a Lamborghini , Park it in London do a supermarket shop .
Well according to the glossy brochure it’s this that and the other and costs x more than the competition so it’s gotta be better ?
The Lambo sales man will never put you off as would any boat show smiley person .

 

[ShaneAtSea]

Conflating hull form and boat style is a very bad idea.

There are many planing boats that are very comfortable for extended cruising. Conversely, there are may displacement boats that you wouldn't want to spend more than a night on.

"Expedition" or "Trawler" style are more descriptive of styling.

I try not to get too technical because it can take the fun out of it

A bit like being a Gynaecologist

 

[prinex]

Nice dsy etc but mistral started to blow up from the W .No issues as we were under a lee cliff .

Which give the location (Porequrolles) is either stay until the next morning or leave quickly. Old trawler ? Anchor down and get the bottle of wine. Quick 25+ knots boats ? Relax as you need 20 mins to safety.

What I'm saying is depending on the boat you have there are almost always safe options. Problem is situation evaluation and if you make a mistake you end up with a boat shaking his crew around and possibly scared passengers. Did my share of wrong calls, they are getting less with the years - or maybe with the experience I just pull the trigger much earlier and make a dash for the next safe spot instead of debating is it going to blow harder yes/no.

Semi-disp I always have seen like an attempt of having trawler space but with still some speed if you really needs to get out of the weather, not even sure if the Swift Trawlers etc are semi-disp.

The thing with the weather turning wild quickly is usually (in the Med) a summer problem, very hot days etc - in the shoulder seasons is much more reliable so the risk of getting rattled around are much less (translation you dont really need to make passages at 30+ kn). Of course August is where everyone is boating hence a quick hull is almost a must.

 

[petem]

I try not to get too technical because it can take the fun out of it

A bit like being a Gynaecologist

It's not technical, it's elementary ?.

Saying that, I wouldn't worry too much about angles of deadrise. Only Porto worries about that in his one man willy waving contest! The planing hulls from the big manufacturers will be perfectly adequate for normal use. If you do get caught out in heavy seas (pretty unlikely these days) you might have to slow down. The boat won't sink.

 

[Bouba]

I try not to get too technical because it can take the fun out of it

A bit like being a Gynaecologist

Deep Vs, gynaecologists…..it’s all getting confusing…..??‍

 

[Portofino]

It's not technical, it's elementary ?.

Saying that, I wouldn't worry too much about angles of deadrise. Only Porto worries about that in his one man willy waving contest! The planing hulls from the big manufacturers will be perfectly adequate for normal use. If you do get caught out in heavy seas (pretty unlikely these days) you might have to slow down. The boat won't sink.

Alimentary canal is the other one . Who have you been dating?

 

[ari]

Absolute yachts are probably the only company that does a Deep-V & Semi-D version of all their boats

I don't think they do!

They offer a Navetta range of trawler yacht style boats, but those are different models, not the flybridge models with different hulls. And I'm pretty sure Navettas have planing hulls too! You won't get almost 30 knots out of a 64ft 50 tonne semi displacement boat with a pair of 1,000hp engines (Navetta 64), you need a planing hull to do that.

 

[Portofino]

Shane , take a look at this Riva Rivale 52 open .A pa

I don't think they do!

They offer a Navetta range of trawler yacht style boats, but those are different models, not the flybridge models with different hulls. And I'm pretty sure Navettas have planing hulls too! You won't get almost 30 knots out of a 64ft 50 tonne semi displacement boat with a pair of 1,000hp engines (Navetta 64), you need a planing hull to do that.

see my post #20 , I put him right as well .

 

[Portofino]

Shane picture this boat .
Monaco resident bachelor needs a day commuter to St Trop / Cannes perhaps the odd romantic overnighter to show a bird a good time .
Riva Rivale 52 .Why not ?

Expensive , exclusive, well made Infact arguably the best fit n finish money can buy .From leather handles hand stitched solid chrome rails , even a champagne cooler under the bed + crystal flute only Riva could build in a std .
The “ if you have ask the price you can’t afford it sir “ - attitude of the sales team at the Monaco yacht show .

What could possibly go wrong ?

Well it rides like a tea tray slams like hell in the tiniest waves .All thoses glasses clattering away below .
Talking from experience.Sure the creamy V8 MAN 900 accelerate it up impressively but you have to back down the rpms very quickly.

What s up , why and how come I hear eve one shriek .
Sorry to prick a few bubbles but take a close look .

First the old chestnut of mid section vol .Guest + crew cabin .Engines on V s big engines yummy 900 s but heavy 900 s as well .
So to work all this in you need to beam out the mid sections .


Not a bad deadrise a medium V , semi tunnels well 1/2 tunnels to lower the shaft angle .So they need to add back lift by compromising the deadrise lower .
But crucially dead rise is only one figure the industry bench mark because it easy to measure .More important is the rest of the flare / V ness as you go Fwds .Infact the mid section V where the strike pount of the water is most where the majority of lift the CoL will be .^^^^ between the red arrows .As the previous layout pic this space is ballooned up inflated to accommodate all the boaty bits associated with the interior lay out .= flat too flat = it a slammer a real slammer .

The 1/2 - 1 hr “ test drive “ was all over in 10 mins the look on Mrs Portos face .Thankfully the sales guy read the mood and said nothing as I turned I around and headed back He knew we were coming from an Itama .

But from the armchair or static boat show you would never know .

Basically they took the Rivarama 44 ( single open plan cabin interior ) with a deep V mid mounted 700 Hp , no semi tunnels , rolla props in a 4.3 M beam and attempted to fit what everyone missed .
So a tender garage 3 cabins inc crew , huge galley and for Henry an American fridge floor to ceiling twin door thing .
Blew up the hull vol shoved as much mech stuff aft tarted it all up in the exquisite Riva garb etc etc .
What a load of crap seakeeping wise .

Its not even got underwater exhaust s as the ER is so far back the exits would comprise the lift from the stern which they could not do without .Hence the big stern 1/4 pipes .Sure look nice but they conceal a flaw .Never mind the noise this is on top of the noise .

Sold over a hundred units though .

 

[Portofino]

Theses are an interesting breed .American sport fishers .

No pressure on the lower interior layout volume as the galley etc are actually on the deck level .
Below is just rudimentary sleeping .

So low to medium deadrise .The V at the very stern .
But and it’s a big but unlike the Riva Rivale and others these sport fishers go very V , fine in the mid sections and bow very quickly.
Plus mega Hp bigger motors than eq EU flybridge - Ari s point re the Navetta “ floating IPS “apartments “

Its in Face book .Sorry cant find a untube version .
198 boats shot gun start to get to the fishing grounds $9.8 Million prize money pot .

No Semi D here guys .

For FB users click on the “ watch on Facebook “

https://www.facebook.com/video.php?v=1011807242974955

Edit not the same tournament but planing every time .The more horses the better if you can
Note the sea state .

 

[ShaneAtSea]

Shane picture this boat .
Monaco resident bachelor needs a day commuter to St Trop / Cannes perhaps the odd romantic overnighter to show a bird a good time .
Riva Rivale 52 .Why not ?
View attachment 125539
Expensive , exclusive, well made Infact arguably the best fit n finish money can buy .From leather handles hand stitched solid chrome rails , even a champagne cooler under the bed + crystal flute only Riva could build in a std .
The “ if you have ask the price you can’t afford it sir “ - attitude of the sales team at the Monaco yacht show .

What could possibly go wrong ?

Well it rides like a tea tray slams like hell in the tiniest waves .All thoses glasses clattering away below .
Talking from experience.Sure the creamy V8 MAN 900 accelerate it up impressively but you have to back down the rpms very quickly.

What s up , why and how come I hear eve one shriek .
Sorry to prick a few bubbles but take a close look .
View attachment 125540
First the old chestnut of mid section vol .Guest + crew cabin .Engines on V s big engines yummy 900 s but heavy 900 s as well .
So to work all this in you need to beam out the mid sections .

View attachment 125541
Not a bad deadrise a medium V , semi tunnels well 1/2 tunnels to lower the shaft angle .So they need to add back lift by compromising the deadrise lower .
But crucially dead rise is only one figure the industry bench mark because it easy to measure .More important is the rest of the flare / V ness as you go Fwds .Infact the mid section V where the strike pount of the water is most where the majority of lift the CoL will be .^^^^ between the red arrows .As the previous layout pic this space is ballooned up inflated to accommodate all the boaty bits associated with the interior lay out .= flat too flat = it a slammer a real slammer .

The 1/2 - 1 hr “ test drive “ was all over in 10 mins the look on Mrs Portos face .Thankfully the sales guy read the mood and said nothing as I turned I around and headed back He knew we were coming from an Itama .

But from the armchair or static boat show you would never know .

Basically they took the Rivarama 44 ( single open plan cabin interior ) with a deep V mid mounted 700 Hp , no semi tunnels , rolla props in a 4.3 M beam and attempted to fit what everyone missed .
So a tender garage 3 cabins inc crew , huge galley and for Henry an American fridge floor to ceiling twin door thing .
Blew up the hull vol shoved as much mech stuff aft tarted it all up in the exquisite Riva garb etc etc .
What a load of crap seakeeping wise .

Its not even got underwater exhaust s as the ER is so far back the exits would comprise the lift from the stern which they could not do without .Hence the big stern 1/4 pipes .Sure look nice but they conceal a flaw .Never mind the noise this is on top of the noise .

Sold over a hundred units though .

Its a beautiful boat but i think my Miami Vice days are behind me

 

[Portofino]

Its a beautiful boat but i think my Miami Vice days are behind me

See what I mean you have to test drive them more so nowadays .
PeteM s post #27 statement is wrong “ The planing hulls from the big manufacturers will be perfectly adequate for normal use.”

That’s a cop out for poor design.
I have explained and detailed how something crap sea keeping wise gets through to production and boat shows and woos punters cheque books open .

Take another one the FL 62 GTO , it new barely made over 30 knots and reading between the review lines , the journo test the ride at speed , well it’s mid 20 knots speed was “ a little lumpy “
Exactly the same reasons as the Rivale 52 they ballooned up the mid sections to stuff in what they thought punters want .
Plus for cost reasins weedy motors .
Those big sport fishers in my post #33 sit between 30-40 knots all day a few nearer 40 .
Power / Hp and the finer entry and mid section s , the opposite of the GTO 63 which has weedy power and flatter mid sections = slower and a tendency to get bumpy .

They ( builders ) are all at it btw it’s like a arms race for accommodation/ floating apartment and Absolute are in the thick of that trend .Low deadrise for IPS + flatter mid section for accommodation and low Hp to be price competitive.

Interestingly and quite telling is Genoa .That show recently there has been some windy days say 3 out of the 6 .
Note the builders that refuse to go out / take punters above F4/5 , to play in the white horses .

Equally note those that demo on every day irrespective of the conditions and it’s not just ribs .


Very interested in your feed back after demo / test drives Shane , I do hope you actually test the short list before committing?
In other than mill pond calm .

 

[petem]

See what I mean you have to test drive them more so nowadays .
PeteM s post #27 statement is wrong “ The planing hulls from the big manufacturers will be perfectly adequate for normal use.”

That’s a cop out for poor design.
I have explained and detailed how something crap sea keeping wise gets through to production and boat shows and woos punters cheque books open .

Take another one the FL 62 GTO , it new barely made over 30 knots and reading between the review lines , the journo test the ride at speed , well it’s mid 20 knots speed was “ a little lumpy “
Exactly the same reasons as the Rivale 52 they ballooned up the mid sections to stuff in what they thought punters want .
Plus for cost reasins weedy motors .
Those big sport fishers in my post #33 sit between 30-40 knots all day a few nearer 40 .
Power / Hp and the finer entry and mid section s , the opposite of the GTO 63 which has weedy power and flatter mid sections = slower and a tendency to get bumpy .

They ( builders ) are all at it btw it’s like a arms race for accommodation/ floating apartment and Absolute are in the thick of that trend .Low deadrise for IPS + flatter mid section for accommodation and low Hp to be price competitive.

Interestingly and quite telling is Genoa .That show recently there has been some windy days say 3 out of the 6 .
Note the builders that refuse to go out / take punters above F4/5 , to play in the white horses .

Equally note those that demo on every day irrespective of the conditions and it’s not just ribs .


Very interested in your feed back after demo / test drives Shane , I do hope you actually test the short list before committing?
In other than mill pond calm .

Porto, above is further evidence that you don't understand most people's priorities for choosing a particular boat.

 

[marcochi76]

Shane picture this boat .
Monaco resident bachelor needs a day commuter to St Trop / Cannes perhaps the odd romantic overnighter to show a bird a good time .
Riva Rivale 52 .Why not ?

Wonderful analysis Porto! I have an excuse now to strop dreaming of the Rivale (that I will never be able to afford!!!) ?

Sorry to go off-topic...
How would you consider the hull of a Princess V39? Deep V, medium V, slam lover?
It looks deep V at entry point, then 21degree at midpoint and 15degree (very flat) at aft.
That is very visible in the attached photos.

 

[Portofino]

Porto, above is further evidence that you don't understand most people's priorities for choosing a particular boat.

No you are wrong Pete .
See my post #32 …….the last line “Sold over a hundred units though .”
And the recent Genoa trend for the floating apartment ( with robotised parking gadgets) guys to cock off demos with the first sight of a white horse in the bay .
They want that ink to dry first . .

Not being judgmental Pete , just saying it as it is .

 

[ShaneAtSea]

See what I mean you have to test drive them more so nowadays .
PeteM s post #27 statement is wrong “ The planing hulls from the big manufacturers will be perfectly adequate for normal use.”

That’s a cop out for poor design.
I have explained and detailed how something crap sea keeping wise gets through to production and boat shows and woos punters cheque books open .

Take another one the FL 62 GTO , it new barely made over 30 knots and reading between the review lines , the journo test the ride at speed , well it’s mid 20 knots speed was “ a little lumpy “
Exactly the same reasons as the Rivale 52 they ballooned up the mid sections to stuff in what they thought punters want .
Plus for cost reasins weedy motors .
Those big sport fishers in my post #33 sit between 30-40 knots all day a few nearer 40 .
Power / Hp and the finer entry and mid section s , the opposite of the GTO 63 which has weedy power and flatter mid sections = slower and a tendency to get bumpy .

They ( builders ) are all at it btw it’s like a arms race for accommodation/ floating apartment and Absolute are in the thick of that trend .Low deadrise for IPS + flatter mid section for accommodation and low Hp to be price competitive.

Interestingly and quite telling is Genoa .That show recently there has been some windy days say 3 out of the 6 .
Note the builders that refuse to go out / take punters above F4/5 , to play in the white horses .

Equally note those that demo on every day irrespective of the conditions and it’s not just ribs .


Very interested in your feed back after demo / test drives Shane , I do hope you actually test the short list before committing?
In other than mill pond calm .

I'll be using the boat mainly on the Intracoastal Waterway in Florida which is littered with 'No Wake Zones' that have a 5 knot speed limit so im not in any rush to go anywhere

Comfort and liveable space is whats important so i guess i do want a floating apartment with flybridge with the range to take me up the East Coast if i fancy an adventure

id be happy just doing the Florida loop..... looks very leisurely ❤

 

[Portofino]

Wonderful analysis Porto! I have an excuse now to strop dreaming of the Rivale (that I will never be able to afford!!!) ?

Sorry to go off-topic...
How would you consider the hull of a Princess V39? Deep V, medium V, slam lover?
It looks deep V at entry point, then 21degree at midpoint and 15degree (very flat) at aft.
That is very visible in the attached photos.

Medium V as convention calls it at the deadrise , the 15 which is the transom only .

How ever I have explained using the American fished that’s it the mid sections that really count .As for lift at the stern they are very low deadrise wise , but catch up mid sections as per vids illustrate. No accommodation/ apparent issues to spoil the hull .

You would have to slow down a bit as the waves increase from 30 + knots to nearer low twenties .
Very similar to my Porto 35 .If you inadvertently flew off the top of a sharp steep one and landed on the rear sections would slam .
It will keep you on your toes trying to go fast in waves , waves / sea state .proportional to its 12 m L

Sometimes I used to get bogged down in big seas 17/18;knots being knocked off the plane in my stern drive boat .
Got by but not a great days out as the wind would spray into the cockpit because the hull couldn’t out run it below 25 knots .