IOR influenced?

[CFarr]

Hi. I wondered if any of you racing experts would mind putting me straight on my yacht please.
She's a 1986 Sigma 362, so classed as a cruiser/racer, but with the same hull as the 36' which was a racing yacht.

I've heard the design was influenced by the IOR rules but what does that mean for the boat?
What are the features on the boat that show that influence - Raked back bow? sloping transom? narrow-ish stern? Tumblehome?

Finally, what are the drawbacks and benefits of having the yacht influenced by IOR?

many thanks in advance
Hoping to be educated
Chris

 

[Racecruiser]

Hi. I wondered if any of you racing experts would mind putting me straight on my yacht please.
She's a 1986 Sigma 362, so classed as a cruiser/racer, but with the same hull as the 36' which was a racing yacht.

I've heard the design was influenced by the IOR rules but what does that mean for the boat?
What are the features on the boat that show that influence - Raked back bow? sloping transom? narrow-ish stern? Tumblehome?

Finally, what are the drawbacks and benefits of having the yacht influenced by IOR?

many thanks in advance
Hoping to be educated
Chris

I'm not too sure about the IOR influences in detail but typically the included lots of beam midships and narrow sterns with tiny mains and massive genoas. Pigs downwind in a blow. Think the 36 moved on from that and they were reasonably vice-free although I do remember one of my two Fastnets on a 36 with a lot of water below which got all the bunks wet from beneath - don't recall where it came from. Most 36s are tired and ex-sailing school while you do seem some nice 362s. Seen a couple of 362s in JOG that rate well under IRC and are sailed well and get good results. Good boats to cruise too I expect.

Anyway if you're thinking of racing don't worry about IOR and see how 362s are under IRC.

 

[michael_w]

Sigma 362 is a fairly late IOR design; probably to the Mk III version of the Rule IIRC. The extreme headsail versus main era was over by then and a more moderate approach was the way forward. The hull was measured using girth chains and a critical measurement was the inner aft girth station, usually near the rudder. IOR boats often feature a tuck up here. The idea was to fool the measurements to think the boat was shorter than it really was. Steven Jones and the late Paul Whiting were a masters at distorted hull lines to gain waterline length. They may have not been pretty, but they sure won lots of silverware.

IOR boats forte was to hurl themselves to windward. I vividly remember steering an S&S 44' through the Alderney Race, carrying a tuck in the main and the blade #3. Apparent wind speed 25Kts boat speed 9 Kts, steering with 2 fingers. Glory days

For more on this interesting subject have a look at Peter Johnston's Yacht Rating book. http://www.amazon.co.uk/Yacht-Ratin...8&qid=1437762740&sr=8-1&keywords=yacht+rating

 

[CFarr]

That's great, thanks you Gents.
I'm not sure I'll ever race her but I would really like to know as much as I can about the design, why she's built like she is and what the consequences of the design are.

Thanks again

 

[Roberto]

The hull was measured using girth chains and a critical measurement was the inner aft girth station, usually near the rudder. IOR boats often feature a tuck up here. The idea was to fool the measurements to think the boat was shorter than it really was.

+1

Without being too technical, the length was measured between bow and stern girths having predetermined lengths, the aft one had to be placed no further aft to where the transom intersected the deck, that's one reason for the rather longish stern overhangs (and for the bustle at the rudder level).
Also, the displacement was measured taking a few canoe body drafts not at the centerline but transversely at some %age of the beam from it, this led to hull shapes being flat at the centreline (a V-shaped hull would have had some displacement not taken into acocunt by the formula).
The Beam was not measured at the deck level but on the canoe body, some level below --> this led to midship sections being vertical in their upper part.
There was also a stability measurement which had a strong influence in the final rating, in a number of boats some keel bottoms were sliced (and the metal replaced with hardwood), and ballast added inside the boat to keep the same displacement, in itself not catastrophic if done with a bit of thought but playing with stability uniquely for racing rating hmmm.
I designed an IOR One-tonner when the limit was taken to 30.5' rating ('83-84 ?), should I design a similar size racing boat today it would be very different..

 

[temptress]

Hi

I used to own a 362 and I raced a few 36s before I bought the 362. At the time of the design IOR was being replaced in the UK by CHS which eventually became IRC. The Sigma 36 was a compromise design that while it paid attention to the IOR rules so the handicap was not overly penalised the design was not driven by that rule. That said the designers of the time only knew the IOR rule then as the other rules were new and contradictory. So you could describe the Sigma 36 as an early chs/IRC design with IOR influenced bits.

The CHS system was released in 1983 by thet Rorc/uncl. It had been under discussion for a few years before due to the decline of the IOR. David Thomas the designer of the Sigma along with most other prominent designers of the time were involved in the discussions.

 

[yoda]

I raced a Sigma 36 for 2 or 3 seasons and the only real downside was the flat bilge that would allow any water that did get in to slosh around in places you didn't want it when going to windward. That said it could take a beating and I managed to do the first 400 miles of a Fastnet race all to windward without coming to grief. I never found it had any real vices when it came to sailing characteristics and certainly none of the downwind issues associated with the mainstream IOR influenced boats. The 362's were always difficult to shake off and in my mind had the benefit of a more traditional rig and an improved design due to the different deck moulding and layout down below. Of course they are all getting on a bit now and it will be the quality of the maintenance over the years that will make the difference. Still a good looking boat which has to be important.

Yoda

 

[Birdseye]

Hi. I wondered if any of you racing experts would mind putting me straight on my yacht please.
She's a 1986 Sigma 362, so classed as a cruiser/racer, but with the same hull as the 36' which was a racing yacht.

I've heard the design was influenced by the IOR rules but what does that mean for the boat?
What are the features on the boat that show that influence - Raked back bow? sloping transom? narrow-ish stern? Tumblehome?

Finally, what are the drawbacks and benefits of having the yacht influenced by IOR?

many thanks in advance
Hoping to be educated
Chris

The 36 wasnt a racing boat but a cruiser racer aimed at creating another OD like the 33. The 362 was the prure cruising boat developed from the 36 when the latter failed to create an OD fleet. Both were past the heyday of IOR influenced shapes - boats like the Sadler 32 with a very pinched in stern and big overlapping genoa were the IOR types. The Sigma reflected a more sensibly balanced rig and hull shape.

 

[Judders]

DT didn't really design to a rule, he just designed good boats that people wanted to sail.