'Unusual' Brand New Shannon Class lifeboat design. .

[rustybarge]

####Home build ? Seems very ambitious ! Perhaps a little downsizing to meet your finances ? I would imagine the fuel bill is daunting, the boat is likely built like a brick outhouse, and with jets probably not the most economical alternative. I think the people inside are supposed to break before the boat does.######


The original twin engine design has 2'6" draught.
I was thinking that a weight saving with just one engine would save 1 ton.
Hamilton jet drives are horrendously expensive, so i was thinking of shaft drive in a propeller tunnel, so should be able to get in at about the same draught or slightly more, and this would mean a more efficient drive at displ. speeds where jets don't operate very well.

Obviously the propeller will hang down below the tunnel, but the weight saving will probably compensate for this.

Dutch sailing barges use steel 'planks' to create compound curves; maybe this would be possible in the bow section?

 

[rustybarge]

Other recent RNLI boats have them including the Mersey class which the Shannon class will replace. Photo of Mersey class stern

My guess is the bilge keels serve several purposes including directional stability but the primary function is support so the boat stays upright when it is grounded or on a slipway. The Shannon class was designed for beach launching and recovery (return) which can include running the boat onto the beach.

Now that's what I call prop tunnels!!!
On the east coast of England nearly all the boats have bilge keels for that very reason, when the tide goes out they stay upright on the drying ground.

 

[Mr Efficiency]

No bilge keels here:

https://www.youtube.com/watch?v=eCoYeAgui6E

Presumably a vessel of the same genre, but much broader in the shoulders. Maybe the self-righting would be less likely to be needed, than the other boat.

 

[rustybarge]

No bilge keels here:

https://www.youtube.com/watch?v=eCoYeAgui6E

Presumably a vessel of the same genre, but much broader in the shoulders. Maybe the self-righting would be less likely to be needed, than the other boat.

Nearly identical hull form, without the keels.....I'm getting a bit confused.

 

[Mr Efficiency]

Nearly identical hull form, without the keels.....I'm getting a bit confused.

Not really that similar, the 'watercat' is much fuller in the bows, would probably give the crew a bit of a hiding in the rough, though.

 

[Mr Efficiency]

These are pretty beamy boats, and probably not that suitable for running at "transition" speeds, economy-wise.

 

[rustybarge]

These are pretty beamy boats, and probably not that suitable for running at "transition" speeds, economy-wise.

Just as an example of a steel boat, very obviously not a similar design,this design is being built on the MBM forum, stretched to 50' with twin 600hp cummins at less than 20 tons. http://www.ybw.com/forums/showthread.php?374141-Fifty-Feet-of-Grey-(steel)

The 46 foot version you see above, is a semi displacement, single engine version for the dutch river network and coastal work.
we have attained a full rcd A rating, with Lloyds approval, for the design, and weld schedule.
The CAD drawings below show the new bang up to date window system we are going for which hopefully will give a modern twist to classic shape.
Also showing the new planing hull, with inset tunnels. 20knots cruise was my goal, with a max 26 knots.
bare hull weight at 14,000 kg.

The 45' version with single engine should come in at about 17 tons.[guess]

57,000 euro's for complete hull and superstructure....http://www.bonitoboats.eu/en/product/Bonito-46-FO-2.html

So steel might just get in at the correct displ.
Fantastic value.

 

[rustybarge]

Here's drawings for the Safehaven design that was rejected. http://www.safehavenmarine.com/2011 PILOT 42 design page.htm

Very obvious severe 'side to side' cork screw action in a following sea, the vessel nearly broached at 15 secs into the video, they had to edit the action. Again at 3.00 minutes another edit... https://www.youtube.com/watch?v=KRjMKExBgdg

Conventional deep keel as you would expect.......

...the plot thickens!

 

[AdvEndureDesign]

My guess is the bilge keels serve several purposes including directional stability but the primary function is support so the boat stays upright when it is grounded or on a slipway. The Shannon class was designed for beach launching and recovery (return) which can include running the boat onto the beach.

This exactly. Not an afterthought, I'm sure.

Again, easy to see why the Safehaven design was rejected.

The Watercat 1500 Patrol III was designed as a new boat for the Finnish Lifeboat Institution. Different conditions call for a different boat. Base design was the Watercat 1500 Patrol shown in the video.

 

[rustybarge]

This exactly. Not an afterthought, I'm sure.

Again, easy to see why the Safehaven design was rejected.

The Watercat 1500 Patrol III was designed as a new boat for the Finnish Lifeboat Institution. Different conditions call for a different boat. Base design was the Watercat 1500 Patrol shown in the video.

I'm sure your'e right, the Baltic is a much more protected sea but can get pretty rough too.

I think the Shannon should be called a semi~planing hull, half semi~displ at the bow and with the bilge keels, and half classic planing vee at the aft and mid sections.

It will revolutionise hull design.

Re the cost of the RNLI build:.
Jet space
£206,000
Engine room
£389,000
Tank space
£118,000
Survivors space
£263,000
Fore store
£100,000
Forepeak
£74,000

Page 26: http://www.berthon.co.uk/publications/BerthonVII_LifestyleMagazine.pdf

Told you those Hamilton jets were expensive.....where did I leave my lottery ticket?

 

[jonr]

The Shannon looks great. The catamaran in the first video looks scary when it sticks the bow into a wave.

 

[The Loftsman]

Another good reason why everyone with the least bit of interest in ships, boats or the sea should contribute what they can to an organisation which has been saving lives at sea for many, many years and all voluntary as well when that flare goes up the guys drop whatever they are doing and head for the boat no matter what the weather or the time of day or night.
Big thank you to the R.N.L.I.

Cheers

 

[rustybarge]

The Shannon looks great. The catamaran in the first video looks scary when it sticks the bow into a wave.

...but they are the vessel of choice for commercial operators on offshore wind farms, summer and winter 365 days a year; and actual practical experience on the sea must be worth something in the end rather than a concept on a NA's drafting board.

 

[rustybarge]

Another good reason why everyone with the least bit of interest in ships, boats or the sea should contribute what they can to an organisation which has been saving lives at sea for many, many years and all voluntary as well when that flare goes up the guys drop whatever they are doing and head for the boat no matter what the weather or the time of day or night.
Big thank you to the R.N.L.I.

Cheers

...and they don't even get paid for it.

 

[Mr Efficiency]

These rescue boats don't seem to me to be a good template for a pleasure craft, especially if you intend to potter around at 8 knots most of the time. At that speed they are much less efficient than a boat purpose-designed to run at that speed. You will pay through the nose for the ability to 'dash' home at 17 or 18 knots when the weather turns. The aim of these boats is extra speed to get to the trouble more quickly than the traditional lifeboats, and to do so without bashing the occupants senseless. They are designed for conditions where prudent pleasure boaters are not on the water. I'd be looking elsewhere for inspiration, possibly at small pilot boat designs, where a turn of pace and good sea keeping are both required.