displacement and stability?

[kfz]

How does displacement effect stability.

I'm not talking about distribution of weight. COG or anything but just plain old weight of boat.

The reason I ask is that modern designs are hugely lighter than traditional or classic designs does this make the boats inherently more stable and seaworthy?

Im sure modern hull/sail designs come into it but is there anyway og getting round the problem that 'There aint no replacement for displacement' as they say?

regrds
Kev

[JimC]

The reason I ask is that modern designs are hugely lighter than traditional or classic designs does this make the boats inherently more stable and seaworthy?

So many other factors that I think its the least of your worries... Of course in any case larger boats in thermoplastics tend to be barking heavy... As a material it doesn't seem to scale up as well as plywood. The modern high performance boats give a whole lot of new problems just because they are so much faster... I think its fair to say that few traditional style boats regularly suffer from all the handling problems that come from taking off as you overtake waves downwind and then stuffing the bow in the back of the wave you've jus caught up...

[Graham T]

Think there must be a lot more too it than weight - one of the tippiest boats I have sailed (I have always been too large for a Moth....) is an RS Vision - this lump of thermomoulded soapdish weighs a fair old bit and is quite beamy and slow. Why it is so tippy I don't know. My Miracle which weighs next to nothing has only been over twice in the past ten years despite being sailed mainly when it is too windy for me to dare taking the Osprey out.

[kfz]

I agree with you guys but are we saying displacement/weight isnt a factor at all?

Kev

[davidh]

I would not go so far as to say that it is NOT a factor - but I would strongly say that it is ONLY a factor - there are far more important considerations.

If you look at the Merlin Rocket Book, published in 1985, it takes a quick look towards the future and talks about boats getting flatter and wider. Yep - spot on... but waterlines are skinnier than ever. If we take as our example the Rs300 (it is an extreme boat but equally makes the case very well) here you have a boat that is modern, fast - and difficult to sail. This is not to take anything away from the boat -it is good (though not the 'best' of the RS single handers which I would still say is the 600) but is very evidently not a boat for the casual every now and then sailor.

I mentioned earlier in another string that I'd recently been the after dinner speaker at Hayling, when my topic was pretty much the question you're asking. I demonstrated through a number of progressions that as you add sail/or sails to a boat you reduce the pool of people who can fully enjoy the sailing experience.

Move up the PY numbers and the same applies - the faster the boat, the fewer the people who can sail the boat through the whole range of wind conditions. Another good example here is the Int14 - which since it went low displacement and super high tech is a wonderful bit of kit - but is hardly the boat for the irregular club sailor. This last season they held the Prince of Wales Trophy Race at Hayling and it was nasty and windy. Out of a small fleet I think they had something like 16 finishers - just half the fleet. Yet when their held a 505 Worlds Qualifier at the same club, same water, similar conditions, pretty much the whole fleet got round and most thought it the 'best dfy of the year'. As far as I an concerned, the case can rest there. Int Canoes with kites, the Devoti D-One, Musto Skiff.... all these boats are becoming the specialised domain of the committed sailor.

Yet the crazy part of all this is to look where the best competition is: It's in slower boats, fleets like the Solo and GP14.

What this says to be is that the marketing led commercialisation of the sport is skewed to developing boats that people think they want to sail, rather than boats that they can actually manage. This is one of the great ills that is becoming apparent in the sport - my worry is that by the time the people who really can do something about it wake up to the fact - it will be too late!

D

[kfz]

Yet the crazy part of all this is to look where the best competition is: It's in slower boats, fleets like the Solo and GP14.

What this says to be is that the marketing led commercialisation of the sport is skewed to developing boats that people think they want to sail, rather than boats that they can actually manage. This is one of the great ills that is becoming apparent in the sport - my worry is that by the time the people who really can do something about it wake up to the fact - it will be too late!

D

David,
Completely agree with you, actual boat speed is pretty much irrelevant (he says with a 6 kt springs at his local club), lets face it sail boats are slow, if you want speed spend 3 grand on a second hand powerboat, beat any sailboat hands down, like two flees arguing who owns the dog.

Where I'm coming from is that how do modern designs (ie lightweight) get sway with not having much boat in the water. This is a law of physics and No computer is going to get round it.

I guess its all relative, I guess when the plywood boats of the 40 and 50's came out all the old salts used to sailing there big clinker timber boats thought, 'Modern lightweight stuff, bloody useless in a blow!' And I guess their right. Lust like in a another 40 years the old salt rinky dink asymetric skiff owner will be saying bloody modern carbon fibre boats too unstable.

Can modern designs make up for the low(er) weight/displacement in thre stability stakes to what we now call a classic or cruising dinghy.

Kev

[jpa_wfsc]

Yet the crazy part of all this is to look where the best competition is: It's in slower boats, fleets like the Solo and GP14.



D

... and the Finn

[Rupert]

What we are maybe looking at here is not the skiff end of the spectrum - they are light and tippy, and more weight would just make them heavy and tippy.

But the Heron end of the market? It is possible to build boats like this far, far lighter, but I think that it would make them more skittish, harder to handle, and would put off cruising sailors, right up to the point they have to pull it out of the water...

[Nigel]

My gut feel would be that hull shape is a far bigger factor than weight.

he says with a 6 kt springs at his local club

Is that all ? Where do you sail?

[kfz]

My gut feel would be that hull shape is a far bigger factor than weight.

he says with a 6 kt springs at his local club

Is that all ? Where do you sail?

liverpool SC

[Rupert]

My gut feel would be that hull shape is a far bigger factor than weight.

he says with a 6 kt springs at his local club

Is that all ? Where do you sail?

Just because you sail somewhere where it is like the plug has been pulled out!

[kfz]

My gut feel would be that hull shape is a far bigger factor than weight.

he says with a 6 kt springs at his local club

Is that all ? Where do you sail?

Just because you sail somewhere where it is like the plug has been pulled out!

Rupert, Where does he sail?

Kev

[Rupert]

At Shirehampton, just up from where the Bristol Avon meets the Bristol Channel. A mad place to sail!

[Ed]

Where does Nigel sail?

Might be wrong, but think he sails at Shirehampton on the mouth of the Avon.

I seem to remember that Springs there are a little on the fast side

eib

[kfz]

Where does Nigel sail?

Might be wrong, but think he sails at Shirehampton on the mouth of the Avon.

I seem to remember that Springs there are a little on the fast side

eib

Yep, makes the Mersey look like Sefton Park Lake......

Its good fun but you need to be aware not to caught downtide of the slip, on the ebb once you have cleared the beach, about 1/4 mile, then the next landing is 9 miles downstream.

Kev