Fast boats and slow boats

[sighmoon]

Looking at PHRF handicap ratings, the difference between a fast boat and a slow boat is not that big at all. Looking at boats of a similar size

FARR 31 81
X102 120
BENETEAU OCEANIS 321 168
CONTESSA 32 180
ISLAND PACKET 320 198

This means that the out and out racer, the Farr would be about 2 minutes per mile faster than the Island Packet (198-81). In normal conditions, say the Island packet is going 5 knots, that would be about (5 * 2/60 miles=) 1/6 mile, just under 300 meters, after an hour's sailing. Part of the Farr's advantage is probably pointing ability, so on most points of sail, the difference would be even less.

Considering the very different emphasis in design, I find the gap surprisingly small.

Perhaps more surprising is the miniscule difference between the Island Packet 320 and the Contessa 32. The former being 6.1 tonnes, chubby and long keeled - the latter being 4.2 tonnes, pointy, sleek and deep fin keeled. The difference is only 18 seconds per mile, or after an hour at 5 knots, they'd be only 45 meters apart.

(source of ratings: http://www.phrfne.org/page/handicapping/base_handicaps)

 

[ytd]

it just confirms that waterline length is the main determinant of speed. How many races would be run in a wind range between 5-15 knots? Above 15knts they are all going at hull speed. Below 5 they will be drifting around and a heavier boat may have the momentum to glide through the calms.

 

[Seajet]

Even allowing for varying conditions, as the handicap has to, I find the gap of 18 seconds a mile between Farr & Island Packet simply unbelievable.

More likely the Farr could sail 18 circles around the IP in a mile !

Waterline length is gradually becoming discredited, I know from personal experience it certainly doesn't apply all the time to all boats ( and I'm not talking about planing or surfing ).

 

[sighmoon]

Waterline length is gradually becoming discredited, I know from personal experience it certainly doesn't apply all the time to all boats ( and I'm not talking about planing or surfing ).

The length (and so speed) of the wave hollow between bow and stern is the determinant (unless planing), because to go faster, the boat has to climb out of the hollow in the middle. Boats like the Farr have a long, straight run aft, which makes the stern wave form further back - lengthening the wave, and thus increasing the speed of both wave, and the boat stuck in it.

 

[sighmoon]

Even allowing for varying conditions, as the handicap has to, I find the gap of 18 seconds a mile between Farr & Island Packet simply unbelievable.

More likely the Farr could sail 18 circles around the IP in a mile.

18 seconds between the Contessa and IP. The Farr was 2 minutes ahead of the IP

 

[flaming]

PHRF is a one number system. As such it will never be perfect, and will never satisfactorily rate lightweight flyers and "leadmines" against each other as they have such different performance characteristics.

However, that to me looks like a gift rating for the Farr, as when the wind is sub 8 it will actually be moving, wheras the heavy boats will be parked, especially downwind. And in 15+ it will be planing downwind, and even if they got to the top mark together (Which I wouldn't expect) I'd expect the Farr to more than make its time up with the kite hoisted. 8-14 knots (ish, I'm only guessing a Farr starts planing in 15, but it seems reasonable) it would be close though.
What normally happens however is that lightweight boats such as the Farr do not race against similar sized boats, but much bigger boats with similar ratings. And this is why they struggle, because then they're slower upwind, and faster downwind, making it hard for them to sail their own race at the start, and leaving them with a catch up job to do on the downwind legs.

Given that PHRF is an "observed performance" handicap system rather than a measurement system, I suspect that this rating is due to watching it sail against larger boats of similar rating, rather than similar sized slower boats.

 

[doug748]

Good post.
Before the point gets lost in a miasma of side issues about this boat or that. I have long felt that the quest for a fast boat, putting all else aside, was a bit daft. The true difference in speed is often pitiful.
Of course it means everything when serious racing but in a cruising boat, so what? A lot better to find a boat that will make progress in a chosen range of conditions. Some will make progress in light airs, some won't. If you hate engines, that can make all the difference to your perspective.
It has been said many times: If you want to go fast, buy a motorbike.

 

[flaming]

Of course it means everything when serious racing but in a cruising boat, so what?

Range.

If you are a "typical" working person with a 2 week summer holiday period, you can get much further and see much more if your boat can make passage at 5 knots instead of 4. That efectively adds 25% to your range, and increases your choice of cruising ground. You can of course still visit the closer harbours, but you can also travel further afield.

And those are still very modest speeds for a modern 30-35 foot cruiser racer.

Of course if you are retired or world cruising this might not be such an issue.

 

[Seajet]

There is also the point that in coastal cruising speed IS safety, getting one into port before bad weather hits.

The boat herself will be safer too; safer from being promptly sold on ! A fast ( not extreme ) responsive boat is much more fun and rewarding to sail.

 

[savageseadog]

Having been ground to dust by a slow boat with a high rating over the years I can justifiably say that racing a slow boat in a fleet of largely different boats is a waste of time. Rating systems come up with a theoretical speed based on waterline length, ballast ratio rig size etc etc. No rating system can compensate for newer lightweight fast designs and sailing into a current. With planing conditions, high and low wind speeds ratings can be binned.

 

[awol]

Looking at PHRF handicap ratings, the difference between a fast boat and a slow boat is not that big at all. Looking at boats of a similar size

FARR 31 81
X102 120
BENETEAU OCEANIS 321 168
CONTESSA 32 180
ISLAND PACKET 320 198

This means that the out and out racer, the Farr would be about 2 minutes per mile faster than the Island Packet (198-81). In normal conditions, say the Island packet is going 5 knots, that would be about (5 * 2/60 miles=) 1/6 mile, just under 300 meters, after an hour's sailing. Part of the Farr's advantage is probably pointing ability, so on most points of sail, the difference would be even less.

I'm more used to CYCA (minutes in the hour) and PY systems but my brain is having a wee bit of difficulty with the above which I'm sure the forum will put right for me.

If the Farr is 2 minutes per mile faster than the IP then after an hour at 5kts it should be 10 minutes ahead which is a wee bit more than 300m. And, incidentally, 1/6 of a nm is >300m.

I await correction!

 

[flaming]

Having been ground to dust by a slow boat with a high rating over the years I can justifiably say that racing a slow boat in a fleet of largely different boats is a waste of time. Rating systems come up with a theoretical speed based on waterline length, ballast ratio rig size etc etc. No rating system can compensate for newer lightweight fast designs and sailing into a current. With planing conditions, high and low wind speeds ratings can be binned.

Indeed. Rating systems work very well when you have boats that are broadly similar in type and speed potential. Too broad a rating spread, or too broad a spread of "weights" and the conditions start to have a bigger say than the crew on the winner.

 

[sighmoon]

Range.

If you are a "typical" working person with a 2 week summer holiday period, you can get much further and see much more if your boat can make passage at 5 knots instead of 4. That efectively adds 25% to your range, and increases your choice of cruising ground.

Aye, but my point is that the speed advantage of a very fast boat compared to a very slow one seems to be about 10%, which is much smaller than I'd have thought from experience.

 

[sighmoon]

If the Farr is 2 minutes per mile faster than the IP then after an hour at 5kts it should be 10 minutes ahead which is a wee bit more than 300m. And, incidentally, 1/6 of a nm is >300m

My brain ached a bit while trying to work it out. I think you're probably right. Where's that 'ooh how embarrassing!' smiley?

Still a smaller distance than I'd have expected.

(1/6) nautical mile = 308.666667 meters

 

[johnalison]

Aye, but my point is that the speed advantage of a very fast boat compared to a very slow one seems to be about 10%, which is much smaller than I'd have thought from experience.

10% sounds about right to me. On a North Sea or Channel day crossing there has to be a significant difference between boats for there to be a two-hour gap on arrival.

When we used to race in the Blackwater there was usually a downwind start and a run for 7-10 miles down tide. Almost invariably we all arrived at the downwind mark together, from 1 tonners to Pandoras.

 

[Clive]

Most rating systems are not just based on the diamentions of the boat. ie the Portsmouth system is adjusted acording to the results supplied by sailing clubs. Even the IRC system has some adjustment for age. However the IRC system does not adjust the rating of boats due to the ability of the helms.

If you look at the results of the Round the Island race in 2009 for the IRC division and take two simular sized boats eg Sigma 33 and X332, both 33 foot, but some years apart in design.

Sigma 33 TTC rating 0.914 top boat finished 30th in a corrected time 9:09:33
X332 TTC rating 0.988 top boat finished 23th in a corrected time 09:04:39
Only 294 seconds apart (on Handicap) after some 9hrs sailing this looks a good even handicap. now look at the slowest boats in each of the two type of boat. Sigma 14% slower and x332 19% slower.

This shows two things,
1) design matters to speed, ie X332 is 9% faster than a Sigma 33.
2) the nut on the tiller matters more.

 

[Lady Campanula]

I have long felt that the quest for a fast boat, putting all else aside, was a bit daft. The true difference in speed is often pitiful.

It has been said many times: If you want to go fast, buy a motorbike.

Monomarans are slowish, slow, and slower....

If you want to go fast, buy a trimaran.

 

[Twister_Ken]

To the man who said speed doesn't matter when cruising, maybe you were thinking of tideless waters? The ability to sail faster and get to tidal gates before they swing shut can make a HUGE difference to passage times.

 

[dt4134]

Monomarans are slowish, slow, and slower....

If you want to go fast, buy a trimaran.

Would a quadmaran be faster still?

Back to the general discussion, you have to wonder what a Farr31 was doing racing PHRF. Maybe they weren't the pick of the bunch.

 

[flaming]

Would a quadmaran be faster still?

Back to the general discussion, you have to wonder what a Farr31 was doing racing PHRF. Maybe they weren't the pick of the bunch.

I've just noticed that it was a Farr 31, not a 30. It's the 30 that I was thinking of, a Farr31 is (I'm pretty sure) an old IOR design, not a downwind flying machine.
Which probably means PHRF was it's best option.