IoR hulls versus modern IRC derived hulls

[Judders]

Looks like an IOR hull - there should be a health warning with these hull shapes for anything approaching downwind sailing

That was not my point but in answer to your point ......

Yep - used to race Beneteaus (very hard) and in early 1990's raced a 45 footer which would be equal upwind with a stipped out two tonner (ex Admirals Cup) and waved bye bye to it downwind as they struggled with broaching whilst we powered away under full control!

Bit of thread drift - apologies to the OP!

You're right, we're in danger of a thread hijack, hence a new one...

Notwithstanding that the early nineties probably don’t count as modern in yacht design terms, it's a very subjective anecdotal point. I can equally point to the way in which modern Bendytoy 40.7s and First 40s are murdered upwind by late IOR designs.

Certainly in the latter case, I am satisfied in my own mind that it's because the lead boat is being sailed better, or at least that is part of it and perhaps that was also true of the reverse twenty years ago?

Also, the nature of the IOR was of course that there were an awful lot of one offs and some were better than others. I would guess that those which are still raced today are the good ones, but it’s before my time and I'd be willing to stand corrected.

But why the health warning on going upwind in an IOR hull? The good ones don't slam or round up or fall away anything like as frequently as the modern Bendytoy, and I don’t just want to pick on them either as I am sure the same is true of many modern production Cruiser/Racers.

 

[dt4134]

There were good IOR boats and bad IOR boats, there were conservative IOR boats and extreme IOR boats.

Remember, the Contessa 32s & Sigma 33s are IOR boats.

I raced on a late and very competitive IOR half-tonner and we were perfectly capable of carrying a spinnaker in a F8, the main risk being submarining. In fact she went quite well on a dead run in light to medium winds, which is something I wouldn't even think of attempting in an IRC boat (because it is slow).

IRC did encourage more ballast, but some modern designs have particularly unbalanced hulls with wide sterns. I've not raced a 40.7, but having raced several other x.7 designs, both bigger & smaller, I'd say they are quite amenable to broaching. In extreme cases you can have the main fully dumped and still broach to windward under headsail if it is not eased too.

 

[sailorman]

But why the health warning on going upwind in an IOR hull? The good ones don't slam or round up or fall away anything like as frequently as the modern Bendytoy, and I don’t just want to pick on them either as I am sure the same is true of many modern production Cruiser/Racers.
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i have owned an IOR One Tonner this passed 14 yrs.
we dont race but we have ( Me n Swmbo) carried the Spi in 15 kts apparent, it was then taken down whilst we were still in control .
she has yet to slam, is a very stable platform & great to sail.
we dont do rounding-up, she goes to windward like a Witch with 52% ballast ratio

 

[Stork_III]

The health warning, in E39mad quote, was for going downhill.

 

[E39mad]

The health warning, in E39mad quote, was for going downhill.

Indeed - most sail up wind superbly well! Tis when you put the coloured sail up in medium to strong winds that the problems with their design show themselves.

 

[Judders]

The health warning, in E39mad quote, was for going downhill.

oh yeah! I've managed to misread that half a dozen times.

That said, I'd refer to the Liqud Vortex thread for the downwind qualities of the 40.7 versus a a good IOR equivalent.

 

[doris]

oh yeah! I've managed to misread that half a dozen times.

That said, I'd refer to the Liqud Vortex thread for the downwind qualities of the 40.7 versus a a good IOR equivalent.

Liquid Vortex's problems were a crew of novices in frisky conditions. The crash gybe was caused by the boat answering the helm as it should. A 40.7 is terrific downhill, powerful but excellent.

 

[Judders]

Well old boy, I was in that race and the other 40.7s were all over the place, including the ones with proven crews. The successful boats were the Asymmetric ones who didn't even attempt to go properly down wind.

To be balanced however, the Barclays 36.7 had a good run that morning.
It goes back to my point that crews play a huge part in this.

 

[monkfish24]

From experience, in a 26ft, cold moulded ply IOR quarter tonner called bullit, It was the prototype to the Glass version designed by Jacques Fauroux.

I digress.

35 gusting 40kts, downhill, spinnaker up, completely surfing into falmouth harbour, never once felt out fo control!

What's more there were benetau first class 8s racing with us where two had lost their rig. I know which boat I was putting my chances on holding together.

Quarter Tonners look light but by god this one is like a tank. It is still winning in the Solent with the QTC

 

[fishermantwo]

The yacht in my avatar is a halftonner thats done 5 Sydney Hobart's with the previous owners. Has 5 spinnakers. The heavy air spinnaker is made out of heavy dacron cloth, looks like about 6 ounce and the tack rings are SS rings about 2 inches across made from 3/8 rod. The previous owner reckons they used it in 30 knots down wind no sweat.

 

[flaming]

I can equally point to the way in which modern Bendytoy 40.7s and First 40s are murdered upwind by late IOR designs.

Don't really recognise that scenario.

I don't often race on 40.7s, but I have. The Elan I race on is however pretty similar in many ways.

I have never, ever, been beaten to the windward mark by an IOR boat. That includes a swan that is 4 foot longer, every sigma 38 in the Solent and others. Simply put the harder it blows the further in front we are. To win under IRC you have to be fast upwind, not downwind. Hence the trend to T keels.

 

[savageseadog]

Don't really recognise that scenario.

I don't often race on 40.7s, but I have. The Elan I race on is however pretty similar in many ways.

I have never, ever, been beaten to the windward mark by an IOR boat. That includes a swan that is 4 foot longer, every sigma 38 in the Solent and others. Simply put the harder it blows the further in front we are. To win under IRC you have to be fast upwind, not downwind. Hence the trend to T keels.

What's the theory behind T keels?

 

[E39mad]

Quarter tonners are light enough to plane whereas larger IOR hulls may not. The IOR hull shape esp towards the stern in particular slowed the boats down wind - a modern hull does not have these distortions and is freer to plane. You used to see lots of rooster tails from IOR sterns whereas modern hulls leave a much cleaner wake in the same conditions.

Because of the hull distortions the boats would become overpowered off the wind making them difficult to handle as they try to trip over themselves. Thus they are more likely to broach or chinese jibe. Same race as the two tonner mentioned previously in the Bene 45 we saw a Swan 51 (Holland design) chinese gybe spectacularly a little distance behind us.

 

[Crabman]

The early IOR boats were designed for going upwind 1/2 ton shamrock etc . Then the French brought in wider stern boats for downwind , Elf Equitaine. The skill was down to the helm and crew as with all boats .Simply having a fast boat does not cut the mustard, that is only one part of the jigsaw. With all the lumps and bumps would you be able to get the hull out of a one piece mould?Would a split hull mould be more exspensive to produce? Good memories racing the ton class boats in the 70's and 80's.

 

[flaming]

What's the theory behind T keels?

High aspect ratio fin, with all the weight at the bottom. Hence lower centre of gravity, less wetted surface area and more efficient fin - so more lift.

 

[chewi]

rooster tails from IOR sterns

what's a "rooster tail"?
Not heard of that.

 

[Crabman]

What's the theory behind T keels?

When the boat heels, the keel gets longer, thats the theory, then you have the collins slotted keel , sailed years ago a boat called Rulor with this keel very quick.

 

[flaming]

When the boat heels, the keel gets longer, thats the theory,

Run that past me again...?

 

[chewi]

When the boat heels, the keel gets longer, thats the theory, then you have the collins slotted keel , sailed years ago a boat called Rulor with this keel very quick.

thats a theory!
How does the keel get longer?
The keel is not the waterline!

 

[Crabman]

Would I like to sail IOR now, no, there are some really fast good boats with less hastle.