Interesting hull form

[Woodsong]

From the sales description of the particular boat in question:
The Poseidon Class 53' Motor Yacht is built on solid fiberglass hull 4" thick. The semi displacement hull is designed and utilized for the Royal National Life Saving Service, UK. The hull design is a semi-custom yacht and one of eight that were finished out as private yachts instead of government service. Repowered in Nov 2004 with Volvo TAMD63P-A[FONT=Verdana, Helvetica, sans-serif]

[/FONT]

 

[expat]

It may not know what it wants to be ie planning, semi displacement or fulldisplacement but I love the looks of the entire craft, if it is a variation of a RNLI design its probably a very capabill and safe boat.

 

[Nomad Willy]

expat,
"capabill and safe" ???
Who cares ... look at it.
Just fun'in ya expat.
With 19hp per ton it's either a semi-disp or a very overpowered displacement boat.


Woody/Tony,
You're not making yourself clear ... are you talking about Woodpecker? 4" thick hull? Sounds heavy but I'm not usually in the company of 70 footers. But it says she's got Sabre's. What's this about Volvo's.

You must be talk'in about a different boat.???

 

[Northern Spy]

From the sales description of the particular boat in question:
The Poseidon Class 53' Motor Yacht is built on solid fiberglass hull 4" thick. The semi displacement hull is designed and utilized for the Royal National Life Saving Service, UK. The hull design is a semi-custom yacht and one of eight that were finished out as private yachts instead of government service. Repowered in Nov 2004 with Volvo TAMD63P-A[FONT=Verdana, Helvetica, sans-serif]

[/FONT]

expat,

You must be talk'in about a different boat.???

He's talking about the boat. You know. The one that this thread is about.



Hint: It is not Woodpecker of Poole.

 

[FF]

The Poseidon Class 53' Motor Yacht is built on solid fiberglass hull 4" thick.

I'm not sure a solid GRP that was 4 inches thick could be given enough power to get that weight up on the plane.

 

[Woodsong]

I could get into this Poseidon boat except for the weird hull design. Exterior lines (from waterline up) look nice to me and interior looks nice as well and price is good for this size boat. Except for the fact I also am not a volvo fan, this hull would be too problematic I think to really want to own. I can't imagine difficulty in bottom paint or haven forbid blister repair. It would be interesting to see how the hull rides but since I cruise at trawler speed regardless of hp, I think it would be a mute point.

 

[Nomad Willy]

I think the Poseidon would cruise at hull speed also as she lacks the power to do anything else judging from her small propellers. I suppose though the apparent size of the props may be misleading. The much increased wetted surface of the "ragged" hull may not have that much effect at trawler speeds and unless I'm wrong about the props hull speed it will be. It's probably sellable though as lots of people have enough money that the fuel burn and the Volvo parts cost would be fly stuff.

Most people don't like odd things so if she was for sale the price would probably be right.

 

[Tad Roberts]

Well she has a good name, "Big Trouble"......

Re-powered 9 years ago and 150 engine hours since, 16.5 cruising hours per year? Asking $163k......Big, heavy, short boat with over 700HP installed, not a happy cruiser IMM........

 

[thurman]

Ahhh ... Thank you much TAD and Scott. Indeed there was something to my foggy recollections. I think I had a book at one time that covered all that racing stuff at Cowes in England.

The Watson hull dosn't look warped to me but interestingly it has the same QBB as the boat in the beginning of this thread. With both the transom is smaller than the midships section .... but w the same deadrise. Perhaps I don't have a propper understanding of "warped". I thought it was decreasing deadrise in the aft sections.

This type of hull (Watson and the OP hull) is kind of magical in that at displacement speeds it's semi-disp and w enough fwd motion the QBBL would become horizontal and then achieve a positive angle w more speed and actually become a planing hull. The QBBL would need to be straight though and that may require some angle of attack. By the way TAD a great many here do know what the QBBL is.
The "ragged chine" should be effective at reducing spray but I think the Watson hull actually would be more efficient due to her lesser deadrise. I was in college then and fascinated by all these boats and especially the Moppie in Miami. Soon after I found out how much power these deep deadrise hulls required I was inspired to design my own boat that addressed that shortcoming but w it's own more significant shortcoming. It needed to be of very light disp to perform well and suffered from excessive wetted surface area.

There was a boat that I practically worshiped and I can remember her form quite accurately even now. She was the Woodpecker of Poole. May have been in that same book in another chapter. Woodpecker was about 65' long and fairly narrow. She was more like a stretched out Krogen than anything else contemporary that I can think of but had less freeboard and much less house and top hamper. What I remember most about her was her extremely beautiful form. I'll never forget the Woodpecker of Poole.

Go to yachtworld.com and enter "woodpecker" as the keyword, and you'll find her. A Laurent Giles design, and she's beautiful. Got 600k?

Ouch, I just noticed that Mike beat me to it. Oh well, it was worth repeating... love that master stateroom!

I do think that the hull in this thread is an attempt to duplicate the lapstrake hull. My 38' 1968 Chris Craft Sea Skiff Corinthian was the best boat in a Chesapeake chop that I ever saw, very soft on entry, and just wouldn't pound at 12 kts, her sweet spot. I got about 1 mpg with her on plane at that speed. If most of the hull is riding out of the water, why the worry about the strakes making more wetted surface?

 

[Nomad Willy]

thurman,

Because the Poseidon hasn't got the thrust to plane. But that's just my opinion. If she does your'e right.

See the link in post #27.

 

[thurman]

My boat had 700 hp, but didn't need all of it to reach plane. On plane, her attitude was just a few degrees above horizontal, and her forefoot hovered just over the water. The design actually came from Lyman, CC inherited it when they bought the company. She used a lot less than 700 to stay on plane. Minimum planing speed was around 10.7 kts. I can't really judge if Posiden has enough thrust or not. They both look to my eye like classic semi D hulls, happiest at S/L 2.0. Great in a chop, but very, very, wet.

Posiden's props do seem small. Maybe optimized for higher turning gas engines? What's her length?

Never mind, just went through the thread again. 53' and Heavy.

 

[Nomad Willy]

What does the size of propellers have to do w the kind of fuel being used to turn them?

Posiden is a SD hull but much closer to a planing hull than a FD. So I would think she should have enough power to go well over disp speeds. But it dosn't look like it. I looked at her listing and there is no mention of speeds at all. Dosen't make sense unless someone is trying to cover up the fact that she can't get out of her own way.

 

[thurman]

Diesels are usually low rpm low hp, hi torque, and gas engines are high rpm, hi hp, low torque. High revving engines require less gearing if the props are small and high turning too...

What does the size of propellers have to do w the kind of fuel being used to turn them?

Posiden is a SD hull but much closer to a planing hull than a FD. So I would think she should have enough power to go well over disp speeds. But it dosn't look like it. I looked at her listing and there is no mention of speeds at all. Dosen't make sense unless someone is trying to cover up the fact that she can't get out of her own way.

 

[Nomad Willy]

Thurman,
No need to be. Just choose. The appropriate gear ratio to turn the prop you want. You could turn a 30" prop w a Briggs&Stratton if you wanted. Might take a 50-1 ratio though.

Most boats had direct drive when boats mostly had small props like old Chris Craft's and engines that ran at 1400 to 2000 rpm.

 

[thurman]

Thurman,
No need to be. Just choose. The appropriate gear ratio to turn the prop you want. You could turn a 30" prop w a Briggs&Stratton if you wanted. Might take a 50-1 ratio though.

Most boats had direct drive when boats mostly had small props like old Chris Craft's and engines that ran at 1400 to 2000 rpm.

I noticed that the broker is claiming this boat has direct drive as well. I think the Volvos listed are 2800 at max rpm.

I'm aware that the proper gear selection can accomodate variations in props, but I wonder if your 50-1 ratio might have unacceptable gear train losses. In any case, the boat was reengined, and I too have the feeling that an expert was not consulted in the powertrain choices...

 

[Agaman]

interesting hull

Hi All.

i saw this artical about this hull.
Thought I,d show you my boat, Shes a 1982 All weather Shipmaster, 8.50 metre, built by G.LWatson & Co of Glasgow, they built the Arun class lifeboat, pilot boats, and boats for the UK MOD, the hull is a Ragged Chine design, bit like a spray rail, keeps her very stable in rough weather, twin 120hp fords, will do 19 knots, no slaming, smooth ride.

 

[Nomad Willy]

That is a boat I could REALLY REALLY like.

A lot of wetted surface though but well worth the dry and smooth ride.

Is it thought the "ragged chine" helps create the smooth ride? I doubt that it does. I'd suspect that the smooth ride has all to do w the deadrise. But the pic dosn't show a lot of deadrise ??????

 

[psneeld]

Hi All.

i saw this artical about this hull.
Thought I,d show you my boat, Shes a 1982 All weather Shipmaster, 8.50 metre, built by G.LWatson & Co of Glasgow, they built the Arun class lifeboat, pilot boats, and boats for the UK MOD, the hull is a Ragged Chine design, bit like a spray rail, keeps her very stable in rough weather, twin 120hp fords, will do 19 knots, no slaming, smooth ride.

Someone posted a pic of a similar bottom on a 40 something motor yacht not too long ago...had more than a few heads scratching to the design and it origin.

 

[Gnorts]

Hi All.

i saw this artical about this hull.
Thought I,d show you my boat, Shes a 1982 All weather Shipmaster, 8.50 metre, built by G.LWatson & Co of Glasgow, they built the Arun class lifeboat, pilot boats, and boats for the UK MOD, the hull is a Ragged Chine design, bit like a spray rail, keeps her very stable in rough weather, twin 120hp fords, will do 19 knots, no slaming, smooth ride.

That looks like a very capable boat, with sweet lines, and she looks well kept. It would be a shame to see her damaged when she falls off that awful blocking of oil barrels and cinder blocks. That hull would be expensive to repair!

Just sayin'-if the boatyard won't provide proper jackstands and safety chains, find another place to haul her out!

(sorry, I'm a retired insurance surveyor who's seen the damage done by yards who operate on the cheap - I just can't help myself when I see such carelessness.)

 

[Nomad Willy]

Gnorts,
The drums are three to each side and I've been blocked that way many times. I'd feel very secure w the blocking shown. There is a better way of setting up the drums and blocks of wood. It allows the drums to be vertical and the bottom to be flat on the ground resulting in support probably superior to "proper" jack stands. A bigger footprint for one. Difficult to attach a chain under the keel but creative blocking can over come most of that issue up to a point. These drum stands may be marginal for extreme deadrise hulls.

Also the blocking shown is used extensively in small private marinas.

 

[FlyWright]

Don't know about the ride, but if you like the sound of the waves lapping against the hull at night, this is the boat for you!

 

[Agaman]

Interesting Hull form

Hi All.

I was told they only built five of this model, I know of one in Scotland, and one in France, Engines were fitted with V drive gear boxes, so no engine hatches, walk straight through to cabin.
Just to say the boat is not kept in that yard any more, and is secured with blocks and steel beaching legs,
we do a lot of boating around the french coast, Channel Islands, were there is a full and rise of tide up to 10 metres, tides run through islands around 3 to 7 knots, wind against tide can be quite bad, but in this boat no problems.

 

[brian eiland]

Bertram 31

Didn't the Bertram 31 have a hull somewhat similar? ...the strakes just didn't start as far forward up above the waterline?...and there weren't quite as many

 

[brian eiland]

The 'Bladerunner' also used these
YachtForums.Com - View Single Post - Trimarans and the BladeRunner...


...and Ocke Mannerfelt's Bat Boats


...a few more 'Bats'




Breakthru Hull Design... - Page 3 - YachtForums.Com

 

[Nomad Willy]

Oh the B-31 ... so beautiful.

The Shipmaster's "ragged chine" is more to control spray and the chines may provide a bit of lift keeping the water (to some extent) under the hull but the cost in wetted surface must be rather large. Perhaps too large as we don't see many like this.

The B-31s "lifting strakes" are shaped to produce lift and reduce wetted surface. The Bertram's strakes probably actually increase efficiency.

 

[brian eiland]

Peter Paynes Sea Knife Designs

Have you ever seen these?
Trimarans and the BladeRunner... - Page 4 - YachtForums.Com

...not really a 'trawler subject', but a lot of interesting discussion and photos of unusual hull designs.

 

[Agaman]

interesting hull form

Hi All.

I know my boat is not a trawler type, just thought the hull was interesting to some, has soon has I saw my boat for sale I had to have it. where ever I go, I get a lot of people asking where it came from, i found this picture of a round Britain power boat race, 1969, a boat called foamflyer 26 foot. designed by G.L.Watson.

 

[markpierce]

Those chines don't appear to be of any benefit if one keeps to "hull-speed," as all "good" recreational "trawlers" do.