IOR Ton Rule

[Paul B]

Originally Posted by Charly Setter

No, not at all:

I made a interesting comparison of my (build date 1982) old 1/2-tonner with the modern GP33-class:

Boat / 1/2-ton / GP33
Length / 9,30m / 9,99m
max. Beam / 3,35m / 3,00m
max. Draft / 1,78m / 2,20m
Displacement / 1800kg / 2150kg
Keel weight / 1000kg / 950kg
Crew weight 600kg 560kg

If you look at these parameters the differences are not that large. But if You look at Sail area....

Main / 27m² (21 @ IOR-rating) / 40m²
Jib / 18m² / 26m²
Spinnaker / 46m² / 136 m²

there is a huge difference.

I´m wondering how these modern designs handle this huge sailloads at conditions above 4Bft. The Leadbulb and the higher Draft will help, but I doubt that these designs will be save at stronger conditions (6-9 Bft, even in the Baltic Sea). Conditions we had to withstand several times in races but also shorthanded (2 People) on longer trips.

I´m really thinking about modifying my boat. Just to see what happens if it gets a bulb and more stability.

Many of the resurrected IOR 1/4 and 1/2 Tonners have been re-ballasted with modern bulb keels. They don't rate IOR anymore, they race under IRC.

Many of the top boats have even re-rigged with big, modern fractional rigs with swept spreaders and non-overlapping jibs. So basically they are IRC boats with old IOR hull shapes.

Can you post a picture of your 1/2 Tonner? At 1800kg it is very light, you must have been taking a big penalty. How did you meet the rating, with a very small rig compared to the rest of the fleet I assume? Did you ever do a Worlds to compare performance with the best of the 1/2 Ton fleet?

By the way, other boats with similar specifications to the GP33 (TP52, GP42, STP65, etc) sail well in all conditions. I would guess the RM should be more than 1.5x that of your light 1/2 tonner. Even though the GP33 "length" is not much different from you their sailing length is much greater, and they don't "dig a hole" downwind in the same way as an old IOR shape would.

Now the Melges 32s sail around the course as fast as the IOR 50 Class used to and the TP52s are faster than the last of the IOR Maxi Sleds (68 feet long, rating 70 IOR).

I have done a lot of sailing a modern 48 footer against very good IOR 50 footers (with modified keels), and there is no comparison on any point of sail or in any weather. We see them at the start and then at the dock after the race.

[Charly Setter]

Yes, we took a lot of penalty....

At the start of the building process (from Aug. 1982 to Aug. 1984) it wasn´t that bad at all. But we caught a 5% penalty in winter 1983, when a penalty on low displacement boats was imposed.

Consequently we had to reduce sail area (shorten the rig by app. 1m) and to install a engine with large IOR-Style folding prop. The boat was originally planned
without fixed engine.

Due to the preferences of IOR to deep hulls the hullshape is no U but more or less a trappeze with a extremely small waterline, leading to small initial stability.

In the end the boat depends extremely on crew weight. On upwind legs it costs nearly 0.5 knots, if the foresail trimmer is not sitting on the high side.

We never had the chance to compete in a world championship (money rulez), but we had the chance to compete against a lot of former and coming boats that ended in the top ranks of the WC´s.

It was difficult, but we had some good days competing against them. But before I blame the hull or the conzept:
- We never had a compareable equipment concerning sails and rigging (no rod-rig). In the beginning we used the old sails and heavy rig from our old halfton.
- we never had a full crew, using the full crewweight allowed
- we had to learn a lot about handling of flexible fractional rigs in the beginning.

It takes a lot of time and when every thing was fixed the time of IOR was gone.

Today we are sailing against a lot of old, larger IOR-boats and some modern IMS-racers (Germany is IMS-Country ;-) ) or OD´s. In 1992 we got a new main with E one meter longer (increasing Main area from 21 to 27m². No longer a 1/2-ton, but there are simple ways to fix this.) and the boat improved in all conditions. Last autumn we got a set of modern sails (North / Elvström) and I´m very interested seeing what´s the effect of modern sails.

cu