Passage Speed

[osirissail]

Originally Posted by goboatingnow

folks, folks, just a reality check here , the OP wants to spend money that would just about buy a good bath...
Dave

Since has "reality" every even slightly slowed down the members of CF from going off in directions not even remotely related to the OP's question?

There's no fun in that . . .

[limejucer]

Under good conditions my cat an old slow heavy cruser has held ave speeds well above hull speed for equivelent mono. it will run at 7 kn with 25 hp input. few 25 year old monos can do this. with 50 square meters of sail up i can shift in comfort. These are crusing conditions.
In a storm she struggles to windward but few boats go well then. I have sailed a number of mono hulls who were better in storms to windward and even surfed a rival34...
they still healed and bounced alot.
all boats are different as are the skippers.
Good boat and skipper is better than bad boat and skipper surley no one can argue with that....

[markpierce]

Originally Posted by Stumble

The reason this is important is that very narrow long hulls (like trimarans and catamarans) have length to beam ratios closer to the 8:1 ratio as compared to monohulls which are more in the 4:1 range

Hah! How's about 2.5 to 1 providing more interior room and carrying capacity in relation to length.

[sneuman]

Originally Posted by 44'cruisingcat

I disagree. We almost always do significantly better than monohulls of similar length, or even boats considerably longer. On a recent 800 mile passage we arrived nearly 24 hours before the first monohull making the same passage.

You should enter the Carib 1500, because their multihull entries suck! Why is that??!

[mark_morwood]

Originally Posted by Adelie

Among the boats already finished, both boats over 6kt were monohulls (Moody54 and Oyster 46), 2 of the 6 boats under 5kt were multis, a Lagoon42 and an Outremer.

I couldn't see the average speeds on the website, but those numbers don't seem to match with the results I can see. The Outremer finished about 5 hours behind the Moody 54, but motored for only 15 hours as opposed to 63 hours for the Moody. This is over an 11 day passage of around 1500 miles by cruising boats (some of them fast) but none of the ones I met before they left had "racing" crews.

My personal opinions, as an ex-monohull racer and cruiser, and now full time cruiser on a catamaran, who has spent time offshore in both:

- Big boats go faster than small boats.
- Catamarans keep moving in lighter wind without the turning on the engine
- Catamarans usually have more space and are generally more comfortable/drier - at least in the conditions I have been in
- They both move around at sea - the motion is different on a catamaran than a monohull - drinks stay on the table, but you can still get sea sick
- Monohulls typically have much greater load carrying capacity than an equivalent speed catamaran
- In our previous 36' heavy monohull I used to plan on 100 mile days
- In our current overloaded 48' catamaran I plan on 150 mile days

Mark.

[Adelie]

Originally Posted by mark_morwood

I couldn't see the average speeds on the website, but those numbers don't seem to match with the results I can see. The Outremer finished about 5 hours behind the Moody 54, but motored for only 15 hours as opposed to 63 hours for the Moody. This is over an 11 day passage of around 1500 miles by cruising boats (some of them fast) but none of the ones I met before they left had "racing" crews.

I strictly looked at the leader board results, I did not delve into any underlying narratives that would have indicated how much motoring occurred.

I also appear to have misread the results, I took the VMG listed to be the average speed for the whole course.

Just looking at finish times 2 cat were in the first 10, taking 4th & 5th places. Still don't know about motoring times.

[AiniA]

I think it is simplistic to ask the question about relative speeds since what applies in one size/price range does not apply in another. If you asked about 30 foot boats you would get a different answer than if you asked about 50 foot boats. In the smaller size the mulithulls, loaded for genuine cruising would be slugs, while in the larger size the catamarans are better able to handle the weight and would generally be faster. BTW, you rarely see trimarans out doing extended cruising - there a few older home-built ones from the 70s and 80s but that is about it.

A better comparison is to say which $75,000 boat type is faster or which $500,000 type is faster since that is the world that we actually live in. We buddy-boated with a 44' catamaran across much of the Pacific last year (we are a 45' mono) and found that there was not much to choose in terms of speed, although they had an enormous amount more space than we did. BUT, their boat would cost more than 3x what ours did. Ours is 30 years old and one wonders what 30 year old cats built currently will cost in 2042 - ie will they hold together well for such a long time.?

An interesting question but the OP needs to consider what type of sailing he wants to do in the future and what sort of budget he might have when he gets his future boat.

[rgscpat]

So, where does one look up the VMG * ton / dollar (Euro, lb. sterling etc.) statistics?
(of course, with Motion Comfort and Lots of Room on Board adjustments)

[Captain Jeffry]

Originally Posted by westsail374

In a displacement hull (ie mono) maximum speed is a function of waterline length.

The formula, as I recall, is 1.5 times the square root of the waterline length.

It is possible to exceed this speed while surfing, but maintaining surfing depends on conditions that would not be consistent over a long passage.

Sail on, sailor!

Bill

1.34 X square root of waterline....

[Jimbo485]

Max hull speed = k x square root of LWL
(LWL in feet)

Change the fineness ratio and you change K. Typically K is 1.34 for the average mono. Lower for a barge or a raft. Higher the more you stretch the hull lengthwise without increasing the beam.

The following are the K values which correspond to the ratio of the LWL:BWL: (NB. It is the ratio of the waterline length to the waterline beam of the individual hulls in the case of a cat, NOT the overall beam. The difference is irrelevant in the case of a mono since there is only 1 hull to analyse):

LWL:BWL K

4.5 1.4
10 2.8
12 3.3
14 3.8
20 5.2

This was taken from p74 of Cruising in Catamarans by Kanter.

Racing cats have a ratio of 16 and up. The charter cats are around 8:1. The rest of us are somewhere in between. Note this is the max speed, is a little crude and does not give you an average passage speed. However, in our case, with a 39' LWL and 12:1 LWL:BWL, the result of this formula is pretty close to our max speed.

[shomewo]

I did the last two handed Round Britain and Ireland race (2500 miles, 4 x 48 hour stops) which was an interesting case for comparing multihull to monohull racing speeds. Unfortunately the results do not appear on the web at this time, but... I was sailing a one off 37' monohull and we beat (on elapsed time) all of the multihulls bar 3. Those being Paradox and Drama Queen (Dazcat designs) and a Corsair F32R and none of those beat us by more than 36 hours. So we beat a 40' Schionning, a Dragonfly 35 and several others. I was quite surprised at this as I expected them to shoot off and we'd never see them again.
On further analysis and discussion the following was observed
In light airs the monohulls were faster particularly downwind
In medium multihulls faster
In heavy, particularly downwind (35knts and BIG, steep waves in the North Sea) the monohulls were faster. The main reason for this last difference was while we were sailing at 170 degrees true with a single reefed main and poled out jib, covering 240 + in 24 hours with a max speed of 22.7, ALL the multis were under bare poles and mostly towing tyres trying to not pitchpole (which none did). I will admit that our windy sail was scary, but nothing like as scary as if I'd thought that one wrong luff would have capsized us.

So what does all this mean? Generally speaking in the conditions we chose to sail in multis are faster. But at either end of the range, they lose out.

Since then I have bought a KL28 catamaran, which I sail with my family and we get great short passage speed and only go when the weather is right. But then again who goes sailing with a young family when the weather isn't right? Hope this helps

[Factor]

Race results are sometimes misleading, but at least you Know all boats are racing, unlike the Carrib 150 thingy where some boats are motoring. I would have thought a Dragon Fly 35 should be as quick/nearly as quick as a corsair 32R (no such thing by the way - presume it was either a Farrier 32 or a corsair 31 and probably an F32). Still - talent and skill etc.

What design was the Schionning?

[shomewo]

I stand corrected, twas a Corsair F31R, previously breathed on by Randy Smythe, I think. The big difference between the two is definitely weight. The D 35 is very heavy.
I agree on the misleading nature of race results. But they do at least give a "level" playing field. Level in as much as one assumes that everyone is trying. Biggest issue around here is the lack of regular multihull racing at any level, because it's only racing that hones racing skills and teaches you where the edges are and how not to fall off them.

[44'cruisingcat]

Got a link to these results?

A few things in your post surprise me - do racing boats really car old tyres to use as drogues? We're humble cruisers, but even we have a purpose-made drogue. They're not expensive, and weigh much less and take up far less space than old tyres.

And deploying a drogue in 35 kts? We recently had 3 days of 30+ knots, 2 days were over 35, peak recorded by the ST60 was 47.8 knots, but we never looked like needing a drogue.

[shomewo]

I guess they didn't take anything with them and if you're in Lerwick and tyres are the only thing you can get your hands on...
On your second point. Under "normal circumstances, we would fly a spinnaker in 35 knots, the difference was the sea state. It takes a pretty steep wave to send a 37 foot 4.5 tonne boat at 22 knots on a regular basis. The F31 had the tack of its jib ripped out by the force of a wave coming through the boat. The North Sea cuts up pretty rough when it gets going due to a combination of wind against tide and shallow water.