Nauti Fox
Well-Known Member
Some people tell me this is a planing hull, others semi displacement...or is it all the same?
Taken at 19 knots.
Am I planing...or semi displacementing?
- Thread starter Nauti Fox
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Some people tell me this is a planing hull, others semi displacement...or is it all the same?
Taken at 19 knots.
blueglass
Well-Known Member
looking aft I would say she looks S/D - certain amount of lift but back end digging in a little and not quite fully on the plane.
omega2
Well-Known Member
How much power has she got and were you using all of it to produce 19 knots, if your power is about 75hp per ton I would say you are semi dispacement
DAKA
Well-Known Member
with out getting too technical it looks SD to me.
Wake not fully caught bow wave and not sharp enough for planning.
Laguna not designed to plane.
bow parts the water instead of using it to lift up.
19 gps or log ???
Wake not fully caught bow wave and not sharp enough for planning.
Laguna not designed to plane.
bow parts the water instead of using it to lift up.
19 gps or log ???
ccscott49
Well-Known Member
Planing, for that waterline length and speed, you must be planing.
That is a planing hull, it doesn't matter how big your engines are, if you dont have enough power to make your hull plane, that's a different matter, planing hulls will travel at displacement speeds, often very uncomfortably and often not very directionally stable.
That is a planing hull, it doesn't matter how big your engines are, if you dont have enough power to make your hull plane, that's a different matter, planing hulls will travel at displacement speeds, often very uncomfortably and often not very directionally stable.
Nauti Fox
Well-Known Member
The design speed when new was 23 knots.
Max power is 540hp at 2700rpm. At this speed it uses 2300rpm.
Speed was GPS but with no tide running.
Here's another shot from the side.
Max power is 540hp at 2700rpm. At this speed it uses 2300rpm.
Speed was GPS but with no tide running.
Here's another shot from the side.
ccscott49
Well-Known Member
Maybe trim tabs would improve her stance?? If she's on shafts!
Nauti Fox
Well-Known Member
That is with the tabs half down!
I'm more than happy with the way she goes through the water, its just that talking to various people they have different views on it and the manual doesnt really say. Its a very deep vee at the bow and also deep vee at the stern with a piece that protrudes from the stern by about a foot down both sides of the hull (that the tabs are attached to) but with a gap of about a foot across the bottom.
I'm more than happy with the way she goes through the water, its just that talking to various people they have different views on it and the manual doesnt really say. Its a very deep vee at the bow and also deep vee at the stern with a piece that protrudes from the stern by about a foot down both sides of the hull (that the tabs are attached to) but with a gap of about a foot across the bottom.
DAKA
Well-Known Member
The stance looks perfect to me, as do the photos, great shots. /forums/images/graemlins/smile.gif
There is a laguna similar to this in our club, just re engined with 300's
it is fast but still doesnt plan.
There are some who would say a sunseeker doesnt really plane so I dont expect it matters as long as you enjoy it ! /forums/images/graemlins/cool.gif
There is a laguna similar to this in our club, just re engined with 300's
it is fast but still doesnt plan.
There are some who would say a sunseeker doesnt really plane so I dont expect it matters as long as you enjoy it ! /forums/images/graemlins/cool.gif
Nauti Fox
Well-Known Member
Thanks, to be honest we toddle around mostly at about ten knots but speed up when we need to.
It just intrigued me as to what it is.
It just intrigued me as to what it is.
mainshiptom
Well-Known Member
Alec
great pictures, she is looking good !
Tom
great pictures, she is looking good !
Tom
Nauti Fox
Well-Known Member
Cheers Tom, what happened to the mystery boat you were buying?
Alan's now getting a bigger tug if you fancy it!
Alan's now getting a bigger tug if you fancy it!
duncan
Well-Known Member
planning - she's up and ahead of the stern wave in the 2nd picture
D
Deleted User YDKXO
Guest
Agree with you ccscott49. IMHO there's no such thing as semi displacement although I use the term myself. If a hull is going faster than it's max hull speed, then ergo it must be planing. Really what semi displacement means is a hull that does'nt lift out of the water as much as a full planing hull but they both plane
Medskipper
Well-Known Member
I am pretty sure you have a semi displacement hull. I have always understood that to be a planing hull it has to have chines the full length of the hull or at least 2 thirds of the hull. No one here has mentioned "Chines" they are the ribs that run the length of the hull and help force the water away from the hull thus creating the lift that a boat needs to plane properly. S.D and Displacemnt hull are usually smooth and often have a small keel as well, often a S.D. hulls can perform with speeds around 20 knots but don't normally really get up and out of the water so don't usually exceed 20 odd knots.
Nauti Fox
Well-Known Member
It has no full length chines and a stub keel that runs about 2/3rds the length of the boat.
mainshiptom
Well-Known Member
what sort of tug?
Dave_Snelson
Well-Known Member
No such thing as semi-D
Technically, there is no such thing as semi-D. All hulls have the capability of becoming planing. Its just that some hulls become downright dangerous when you plane them - ask any yachtsman who has surfed down a large wave in a storm.
A boat makes two wakes - one off the bow and another off the stern. When you cause your hull to overtake the bow wave, you are planing. So when you see your bow wave disappear off and you get only one wave out from the stern, you have your answer /forums/images/graemlins/smile.gif Your lower picture would indicate to me that you are planing even though there is some splash off the bow which is quite normal.
Technically, there is no such thing as semi-D. All hulls have the capability of becoming planing. Its just that some hulls become downright dangerous when you plane them - ask any yachtsman who has surfed down a large wave in a storm.
A boat makes two wakes - one off the bow and another off the stern. When you cause your hull to overtake the bow wave, you are planing. So when you see your bow wave disappear off and you get only one wave out from the stern, you have your answer /forums/images/graemlins/smile.gif Your lower picture would indicate to me that you are planing even though there is some splash off the bow which is quite normal.
Nauti Fox
Well-Known Member
Re Planing semi D
From the Nordhavn site
.A.E., however, recognizes that not all owners or prospective buyers need the incredible range of these passagemakers and instead would prefer to go a bit faster during their coastal cruising. A sensible, pragmatic approach to providing faster speeds without sacrificing seaworthiness is to design a boat with semi-displacement characteristics. This design allows the hull to get partly out of the water when sufficient horsepower is applied and to get out from the grip and limitations of its own bow wave. The boat essentially begins to "plane."
So it seems its probably both....err...maybe.
Rest of the article here
From the Nordhavn site
.A.E., however, recognizes that not all owners or prospective buyers need the incredible range of these passagemakers and instead would prefer to go a bit faster during their coastal cruising. A sensible, pragmatic approach to providing faster speeds without sacrificing seaworthiness is to design a boat with semi-displacement characteristics. This design allows the hull to get partly out of the water when sufficient horsepower is applied and to get out from the grip and limitations of its own bow wave. The boat essentially begins to "plane."
So it seems its probably both....err...maybe.
Rest of the article here
whisper
Well-Known Member
Spot on, in my very humble opinion.