Semi Displacement advice

[BruceK]

By and large, I agree. Truth is, nobody really "need" SD boats (let alone full D) for pleasure boating, if by that we mean in conditions which, albeit uncomfortable as they can be in the video which you posted, are still cruise-able at P speed.
It's when you cruise at D speed, not because you choose to do so but because the sea conditions don't allow you to go faster, that I don't agree anymore.....

For me that cut off in my locale is F8 and following sea. Simply because the boat does not have the power to climb the back of the wave. I then am reduced to about 11knts and sucking diesel like there is no tomorrow. I have had to do that several times in the last couple of years usually because I am cruising somewhere else that is better. It's conditions like this that I approach my cut off line

 

[kashurst]

Have a look at the bigger Rodman fisher boats on shaft drive, I'm biased I have a softy flybridge cruiser, however very very deep v hull and small keel goes very easy in the rough stuff. Built in Spain on the Atlantic coast for the Atlantic so not fast med cruisers at all.

 

[NBs]

Hi,

I think about SD or Planing Hull is what kind of trips you do and sea areas and typical wave. My previous boat was of a similar size planing fly and it was nice smooth waters all about 1.5 m breaking breaking wave 22-29kn, the higher the breakthrough wave it did not offer a pleasant ride even if the bow trimmed down and lowered the speed it was to hit the hard bottom, jump up the wave as well as wet riding. For me, the current SD gives a better chance of moving in a big waves comfortably at all speeds, riding is wet driven by a wave, but it's soft and pleasant, folowing sea is much better because long keel and big rudder give direction stability, side wave is deplorable but increase speed Over Hull speed dynamic stability is greatly enhanced and movement is calm.

Video NT42 soft, wet riding difficult to estimate wave height?

https://youtu.be/9tX-GdwUGP4

and NT34' about 5 feet sea

https://youtu.be/qcT85CSZGCY

NBs

 

[Davy_S]

These guys are out for a bit of Mackerel bashing in an SD.

 

[BruceK]

ya no, I agree with Vas, fair play to them but that is beyond simple pleasure boating

 

[Bouba]

I also agree with Vas. I don’t even drive my car in a force 6

 

[omega2]

Kettle's on, bacon frying, no worries!!

https://youtu.be/KqfZ6ZXl5pc

 

[BruceK]

I also agree with Vas. I don’t even drive my car in a force 6

A F6 in open water I believe is very different to coastal water. Here the wave periods just get closer. If you look at Penmaenbach which sits in the middle of Conwy Bay today the waves seldom got to 6 foot but the periods closed in. It was predominantly F6 gusting and is typical of the area

https://www.windfinder.com/forecast/penmaenbach

 

[Bouba]

A F6 in open water I believe is very different to coastal water. Here the wave periods just get closer. If you look at Penmaenbach which sits in the middle of Conwy Bay today the waves seldom got to 6 foot but the periods closed in. It was predominantly F6 gusting and is typical of the area

https://www.windfinder.com/forecast/penmaenbach

You are right, but when I leave port I only have one thing on my mind, how am I going to park. Strong wind and waves at sea are uncomfortable but Med parking in a strong cross wind will ruin your day

 

[Firefly625]

I often am out in my Mitchell when the only boats out are sailing boats, no sports cruisers in sight. I would only buy a SD hull due to how I wish to use my boat and I am not dictated by weather.

 

[benjenbav]

What was max speed? and how heavy was she?

Can't remember max speed. Think I might have once seen 20 knots on the GPS ... downhill! About 8 tons.

 

[Keith-i]

happy to return with a following sea pushing F8 which will produce a 2m rounded swell with a 8 second period provided the waves are not breaking.

Round these parts the waves starting breaking at F4 and dependent upon which direction the tide is running can be very short and uncomfortable. I’ve never seen waves at F8 that weren’t breaking. Add some swell to the mix at F8 and even our 4,000 ton 129m freight boats stop.

For other’s interest, we have a single 265 in our Channel Island 32 and burn about 3.5l per mile at full speed which gets you to just under 20kts. A sensible cruising speed for economy is around 14 kts at just over 2l per mile.

 

[dpb]

Round these parts the waves starting breaking at F4 and dependent upon which direction the tide is running can be very short and uncomfortable. I’ve never seen waves at F8 that weren’t breaking. Add some swell to the mix at F8 and even our 4,000 ton 129m freight boats stop.
.

Point very nicely made!!!!

 

[BruceK]

is running can be very short and uncomfortable. I’ve never seen waves at F8 that weren’t breaking.

Now you have. Doing ~20 knts and the bow pennant still at right angles.

Like I said previously we have Anglesey and the LLyn. If the land is windward it can be quite calm relatively and here you can always have the land windward. This following vid was taken during a weekend where the winds were gusting to F8. As you can see, apart from slaloming around the anchor chain the water is calm

and again in this video. Gusting to F8 we tucked in at Moelfre for the night. Coincidently it was the evening of the Moelfre life boat day I showed in an earlier vid

 

[MapisM]

I’ve never seen waves at F8 that weren’t breaking.

Now you have.

I don't think so.
Whenever sea state is referred to Beaufort scale (Douglas being more appropriate in theory, but less popular), it's common practice to consider non just the wind strength, but also the corresponding wave height.
Which in a Beaufort F8 is 40kts and 6 to 7m respectively, IIRC.
A sea state where the waves are breaking by definition, so to speak.

You might well be cruising in an area where due to local geography (coast sheltered, limited depth, or whatever) a 40kts wind does NOT produce 6 to 7m waves.
That's understandable of course - taking that to the extreme, I've been at anchor in F8+ winds, but very close to the coast in the direction the wind was blowing from, hence with no fetch and practically no waves.
That's far from representing what is commonly referred to as an F8 condition in open sea, though - which I guess is what Keith had in mind.

 

[NBs]

Hi,

link to diagrams with wind speed below m / s, left significant wave height meters, right wind free trip at sea.

Example wind speed 10 m / s, wave height about 2 meters, and wind blows 20 kilometers trip in sea.

http://blogi.foreca.fi/wp-content/uploads/2015/01/Aallonkorkeus.jpg

NBs

 

[Bandit]

There are many, many factors governing the seastate: wind, tide, directions of the wind and tide depth of water, fetch and how long it has been blowing for.

In a boat many factors affect seakeeping hull shape, depth of vee forward, Longitudinal Centre of Gravity LCG, type of drive, keels and bilge keels, length and weight as well as how stiff or tender a boat is from a roll point of view etc etc.

Having had to make decisions about fast ferries, hydrofoils, catamarans an wave piercers it is very difficult to actually compare seakeeping objectively without measuring equipment and a computer.

Also bear in mind all boats are a compromise.

I have had a Sunseeker 31, Mitchel 31 mk 1, Mitchel 31 mk 2, a Halmatic 34, Fairline 36 Sedan and now an old Aquastar 48 no stabilisers cruise 19 knots.

I obviously prefer semi displacements. I don’t choose to go out in rough weather, unless we have to get home. I will take a reasonable level of pasting in heavy weather but the boat will take far more than I ever want to.

My Aquastar rolls with a beam sea below 10 knots, but about 12 knots the ride stiffens considerably dampening the roll considerably so depending on the direction of the waves I adjust my speed in bad weather. In the Halmatic 34 and the Aquastar 48 I have been out in some vile conditions and even in a big following sea I have never felt I have been approaching a broach.

I will stick with semi displacement boats, but every boat is a compromise.

 

[BruceK]

I don't think so.
Whenever sea state is referred to Beaufort scale (Douglas being more appropriate in theory, but less popular), it's common practice to consider non just the wind strength, but also the corresponding wave height.
Which in a Beaufort F8 is 40kts and 6 to 7m respectively, IIRC.
A sea state where the waves are breaking by definition, so to speak.

You might well be cruising in an area where due to local geography (coast sheltered, limited depth, or whatever) a 40kts wind does NOT produce 6 to 7m waves.
That's understandable of course - taking that to the extreme, I've been at anchor in F8+ winds, but very close to the coast in the direction the wind was blowing from, hence with no fetch and practically no waves.
That's far from representing what is commonly referred to as an F8 condition in open sea, though - which I guess is what Keith had in mind.

Fair enough but when I embarked on this I was at pains to point out exactly what I was experiencing and that it was conditions peculiar to my locale and coastal and then repeated this in later posts. The fact that people then chose to half read and latch on to just one aspect of the explanation shows not an attempt to deceive on my part but a lack of comprehension or reading skills on theirs. Not being contentious btw. I kind of figured this would be the response hence why I was at pains to describe the conditions from the very beginning and repeated and put in not only videos but a localised wind sea state prediction for my area. If I had said gusting F8 or gusting 40mph would make not a jot. People would have latched on to that figure anyway and still poo-poo'ed. At the end of the day the OP wanted advice as to whether he should go SD. My comments should be taken exactly in answer to that. A planing hull in the kind of conditions he is likely to go out in is as good and sometimes better than a SD hull. That is my honest belief and everything else was given to support this belief. I'm not seeking approbation by the board, it's fun, it's informative but I am no acolyte.

 

[Blue Sunray]

I don't think so.
Whenever sea state is referred to Beaufort scale (Douglas being more appropriate in theory, but less popular), it's common practice to consider non just the wind strength, but also the corresponding wave height.
Which in a Beaufort F8 is 40kts and 6 to 7m respectively, IIRC.
A sea state where the waves are breaking by definition, so to speak.

You might well be cruising in an area where due to local geography (coast sheltered, limited depth, or whatever) a 40kts wind does NOT produce 6 to 7m waves.
That's understandable of course - taking that to the extreme, I've been at anchor in F8+ winds, but very close to the coast in the direction the wind was blowing from, hence with no fetch and practically no waves.
That's far from representing what is commonly referred to as an F8 condition in open sea, though - which I guess is what Keith had in mind.

:encouragement:

 

[BruceK]

Oh. Just for Elecglitch if you look at the Navionics screen you will see I am in Conwy Bay and can determine my direction to from the compass. Im travelling Eastwards. Have a look at the pennant and you can see the wind is from the North. North of Conwy Bay is the whole of the Irish Sea. I.e there was no landmass sheltering. You explain it then.