Lifeboat Hulls

Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

If I can add my threepennies worth?

I think you have to be very careful indeed with many generalisations that are being made here.

Ribs are not only used as inshore rescue boats - check out what a lot of N Sea oil production units have......Big Ribs for Huge seas.

Lots of skill & big balls
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

I wish everyone could at least state what they believe to be the case as regards the sea worthiness of the three different hull types.

If you think that the modern planing hull is as seaworthy as the displacment or SD hulls then you are simply living in denial.

There is nothing, whatseover wrong in choosing a planing hull boat and if I was in the med and going there for weekends I would stick to my squaddie. However I would not fool myself that in using as planing hull I have the best sea keeping hull shape because I would know that a planing hull relies on its stability on its forward speed and the lift it gets from the interaction with the water. Lose that speed and you lose the stability. A displacment hull relies on its stability on the water it displaces - it sits in the water. The SD is in between.

I have now experienced first hand the behaviour of the SD hull at sea and have chosen to go for that. That is neither a right or a wrong decision - its a decision that is right for me. However, I know that I am losing on some things and gaining on others. Its a compromise. I do know that the ride in the water is magnitudes better than the planing hull alternative - I do know that its is a better sea boat - I do nkow that I will not be able to get there as fast in calm conditions but may well get there faster in rougher conditions. I do nkow that it does not have the same wow factor as my squaddie etc ... in fact many aspects that I have balanced up.

What I do not do is pretend this or pretend that..... I beleive some folks around here are living in denial..... :-)
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

I have just thought - there is a classification of hulls based on their sea worthiness the Trader is a Class A boat - what is a Squadron?

So we already have a system that classified boats according to their ability at sea - therefore I am hardly alone in generalising ... am I?
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

Doh!! Debs has a displacement boat. Cat D, whilst I have an off shore planing boat (Not sure what cat, maybe B??

AAaaRRGggg, will this never end!! /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/crazy.gif /forums/images/graemlins/tongue.gif
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

Paul,

Yes, it's a compromise. Everyone agrees it's a compromise. Please let us get on with our inferior, planing-boat lives. You're absolutely right, the Trader is the right boat for you. It isn't for me, so please don't keep trying to get me to agree that you've made the right choice and you have a superior hull shape.

You have the right hull shape for Gludy-type boating, I have the right hull shape for Wiggo-type boating, and no-one knows what EyeNo has, cos he won't let on...
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

Wiggo at no time have I said that anyone else has the wrong hullshape for them. In fact I have tied to have a rational discussion which is almsot impossible on this forum but here are some facts about what the classes of boats are.

The class rating is a measure of seaworthiness:-
“A” (Unlimited Ocean) STIX Value >32 - adequate to withstand up to a force 10 gale, with average waves of 7 m height and eventual wave heights of 14 m.

“B” (Offshore) STIX Value >23 - adequate to withstand up to force 8 winds, with average waves of 4 m.

“C” (Coastal) STIX Value >14 - adequate to withstand up to force 6 winds , with average waves of 2 m.

“D” (Local) STIX Value >5 - adequate to withstand up to force 4 winds, with waves of 0.5 m maximum.

Now if you take any given length of boat, such as say 60 foot, I do not think you will find any class A planing boat they will all be displament or Semi-displacment.
yes you can find even class d displacment boat - I have a 12 foot dinghy that is that and many river boats are a lower class so that proves nothing.

I can now rest my case ... if you want to dispute what i have eben saying just come up with a class A planing boat of about 60 foot length.
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

[ QUOTE ]
I am hardly alone in generalising ... am I?

[/ QUOTE ]
No - but that doesn't make it any more valid. If anything some of the classifications would seem to conflict with the arguments you are already putting forward - my 25ft planning hulled craft is Cat B for example.

I regret that this thread, and the others, is taking on the same traits as most anchoring ones ie. it's jumping from absolutes to compromises at will. One minute we are talking about comfort, the next survivability and even operational abilty has appeared with reference to lifeboats.
The stability of a planning hulled boat (or any other) operating at displacement speed has little to do with it's sitting on the water rather than in it and everything to do with the shape of the hull and it's various centre's of mass as clearly set out in Dag's books.
I can very easily agree that travelling in SD mode delivers a good balance of control and comfort - Planty's observations above would be an example of exactly that and, in my case, I trim in and hold at around 10/11 knots untill the conditions are too bad for even that, at which point I drop to 6 knots and pretty much go with the flow; the last step before treating each and every wave as an individual challenge. As BrendanS highlights that (treating each wave as a challenge in itself) can be done as well by a planning hulled craft as an SD or D with individual craft characteristics all contributing - RIBs being particularily well suited with (generally) excellent PTW ratio's and stability in all axis. They are not (generally) good for making tea or passenger comfort in extreme conditions however.
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

I think.
1.Displacement hull, good for economy and range but can be uncomfortable in a beam sea and cannot really run for shelter.
2.Semi displacement,good for low and medium speeds and can bash through heavy weather,and has enough speed to run for shelter.The bad points are that they tend to be wet boats and when used towards the upper ends of their speed range use bucket loads of fuel,not a problem if you either have lots of money or dont pay the fuel bills (pilot boats etc).
3. Planing,excellent for getting places with pretty good economy when at the right speed,good for running for shelter,but perhaps can't maintain the pace of a semi when the going gets really rough, if you want to be out there.
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

Yes it does make it valid - the only point that the whole thing took off an was when I suggested that the SD boats were more seaworthy and tehy are.

Does that mean they are suitable for all purposes? NO.

Does that mean that in some specialist conditions they are the best rescue boat? NO

Does it mean they are a better Boat? NO

It just means nothing more that in general they are a better sea going hull from one persepctive - seaworthiness.
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

It seems that summary is not a bad one .. very balanced.

I would add range to it - if you want seriuos cruising its nice to be able to go over 1000 miles between fill ups.

I would also add comfort of ride but would qaulify that with stablisers. Some folks are sicker on a rolling d hull tan a banging planing hull. I really think the stablisers have changed the balance.
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

I've wondered about the seasickness and think that not only is it the motion that does it but also on the semi's and displacement boats people tend to spend more time inside,so losing sight of the horizon and getting that good old sensory conflict where the ears tell you that your moving and the eyes are saying no I'm not.
Not been on a leisure boat with stabs so can't really comment on that one!
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

All I set out doing was a balanced list like yours but when i do it issue is tek nwith the most basic things that you include in your list and then hundreds of posts later the original simplicity of it all is lost!

You are probably right about more time inside and no view of horizon.
The stablisers are like switching off the sea ... that can even lure you into a flase sense of security.
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

Must be a nice piece of kit to react in the sort of time frame needed.
Good luck with the boat.
Al.
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

But your evading your own question. We are not talking about traders. We are talking about D SD and P.

We have a Displacement boat Cat D a 2.3m dinghy Cat C and a princess 35 Cat B?

Cat D is not fit for the sea at all at all. So by the rules you have set, Displacement boats are not fit for the seaand my dinghy is. End of leason.
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

That is absurd - you can have a displacment boat only fit for a canal - ie a 8 ft dinghy.
What we are talking about is equivalant boat a 50 foot D, SD or planing.

So I ask you again ... name a class A planing boat ... you cannot and so are putting up a smoke screen.
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

Cat D, displacement boat is 50 ft well no, it's 49ft and weighs 18 tons, where as Ellen went round the world in her planing boat, not sure what cat. But it got there anyway!!
 
Re: Lifeboat Hulls, Prop Tunnels, The Bristol Channel and Tea

1. I think hlb is talking about a 50ft displacement boat, and there are many that couldn't be taken out in more than a small chop
2. Wallypower is Cat A

Back to your previous response to my post; no - by whatever definition you ultimately wish to ascribe to 'sea worthiness' displacement wins hands down, preferably with a canoe stern and a full length deep keel.
 
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