Best indicator of catamaran speed?

[yellowwducky]

Hi all,

I am just curious what the best indicator is of speed capability for catamarans. I was thinking it might be displacement? For example, I have dug up the following cats info...

Orana 44, 9800kg (light)
Antares 44, 10,205kg (weight is 7937kg, not sure if 10,205 is light or full)
Atlantic 42, 14500kg (unknown if light or full)
Gunboat 48, 8025kg light, 10,200 full
Lagoon 44, 12,152 light, 13,500 full

Now I am pretty sure the Gunboat is the fastest (heck, its the lightest even full and is a full 4 or more feet longer) but its carbon fiber so I kind of expect that. But do the other numbers give any real indication of relative performance? Would one expect an Orana to be faster than an Antares which would be faster than a Lagoon which would be faster than an Atlantic? The Atlantic number here seems oddly large - its pitched as being fast yet that number is huge; granted I don't know if thats a light or full number but either way its the largest of all the numbers. I have a feeling something is off there.

Regardless of the anomaly of that Atlantic number, is displacement a good (the best?) indicator of speed potential?

Regards,

Yellowwducky

edit - the Atlantic number I am seeing now looks to be fully loaded. Still seems very high compared to the others given its a tad shorter and is meant to be designed to be fast/light compared to the competition.

[sailingdog]

Hull speed is a difficult thing when it comes to multihulls in general. It depends on the hull shape, how heavily loaded the boat is, the sail plan, and about a dozen other factors... Generally, a wider catamaran will be capable of carrying more sail than a narrower catamaran of the same LOA. However, a wider catamaran generally is going to be a bit heavier than a narrower catamaran, since it has more bridgedeck between the hulls, and the bridgedeck contributes nothing to buoyancy.

Just out of curiousity, have you priced what mooring or marina slip costs are like for a 40'+ catamaran, much less haul out costs... They're close to astronomical, and not many places can handle a boat with a 24+' beam.

[chucklesR]

There are a lot of factors that go into speed potential; sail plan, hull shape and hull length to beam ratio being some of the factors that SailingDog left out.

Weight matters, a lot. The horsepower the sails can produce is finite, the weight of the boat they need to lift up on plane is not.

Calculators & Conversions
Has a calculator for hull speed that proports to give multihull speed. If so it is absolutely wrong.
I have a waterline length of 32 feet and the site lists me at 8.3kts. I've done 10.3 and have friends that have pushed it to 14kts, and some have taken photo's of the speed log at 18.2kts.

My polar plot shows 14kts with 22knts of wind, I'll take that as max because I reef there.

On the other hand, 8.3kts is a comfortable speed that my 40 ft mono buddies
can't touch.

[sailingdog]

Originally Posted by chucklesR

There are a lot of factors that go into speed potential; sail plan, hull shape and hull length to beam ratio being some of the factors that SailingDog left out.

Huh... did you even read what I wrote? I did say:

...It depends on the hull shape, how heavily loaded the boat is, the sail plan, and about a dozen other factors... Generally, a wider catamaran will be capable of carrying more sail than a narrower catamaran of the same LOA (otherwise known as Length to Beam ratio)

Of course, on a multihull, there's also the individual hull's Length to Beam ratios too, but that can be lumped in with hull shape.. since the hull shape determines the Length to Beam ratio.... doesn't it.

Weight matters, a lot. The horsepower the sails can produce is finite, the weight of the boat they need to lift up on plane is not.

Most multihulls aren't technically planing hulls and don't get up on plane.

Calculators & Conversions
Has a calculator for hull speed that proports to give multihull speed. If so it is absolutely wrong.
I have a waterline length of 32 feet and the site lists me at 8.3kts. I've done 10.3 and have friends that have pushed it to 14kts, and some have taken photo's of the speed log at 18.2kts.

My polar plot shows 14kts with 22knts of wind, I'll take that as max because I reef there.

On the other hand, 8.3kts is a comfortable speed that my 40 ft mono buddies
can't touch.

That calculator is whacked.. It says my hull speed is 7.5 knots... I sail at 9-12 regularly.

[chucklesR]

Obviously, I didn't read what you wrote , I missed that part. For beam to length ratio I meant the hulls themselves, not the overall beam of the boat.
A 9:1 is considered a fast cat, gunboats IIRC are in the 10:1 range. My Gemini is 33 ft long, with a 4 foot wide (maximum) beam at the waterline or a solid 8:1; not particularly speedy in that regard.
It does have a nice teardrop shape optimized for stability - necessary because it's only 14 feet wide which is a very skinny cat indeed (much like my avatar, skinny cat, cool shades and nice attitude).

I dispute the 'most catamaran's don't plane' comment as neither of us are experts on the subject; and every catamaran I've been sailing on (5 different ones) have in fact planed.

[yellowwducky]

"have you priced what mooring or marina slip costs are like for a 40'+ catamaran, much less haul out costs... They're close to astronomical, and not many places can handle a boat with a 24+' beam"

Nope, but I am hoping that if you can afford the boat, you can afford to park it Just like cars, if you can afford a Ferrari, you don't ask about the price of high test gas versus regular. I am assuming this applies to boats as well.

A 500,000-750,000 boat of 42-48 foot size (and 20-26 foot beam) for taking out of the water is what, 2,000 dollars? Keep it on land for a month is what, 3,000 dollars? Completely guesses here. Bad, yes, but you do that for anti fouling once a year and its on land for a week tops? Mooring, yea, that probably costs double what a monohull does? I keep seeing sailing estimates of costs with people claiming to get by on 6,000-10,000 a year! I mean, wow, sign me up for that, my rent is more than that a month! How bad could a mooring fee possibly be?

[US27inKS]

I just look at the polars.

[TOMINDC2]

Originally Posted by yellowwducky

"Nope, but I am hoping that if you can afford the boat, you can afford to park it Just like cars, if you can afford a Ferrari, you don't ask about the price of high test gas versus regular. I am assuming this applies to boats as well.

A 500,000-750,000 boat of 42-48 foot size (and 20-26 foot beam) for taking out of the water is what, 2,000 dollars? Keep it on land for a month is what, 3,000 dollars? Completely guesses here. Bad, yes, but you do that for anti fouling once a year and its on land for a week tops? Mooring, yea, that probably costs double what a monohull does? I keep seeing sailing estimates of costs with people claiming to get by on 6,000-10,000 a year! I mean, wow, sign me up for that, my rent is more than that a month! How bad could a mooring fee possibly be?

Apparently money is no object to Yellowducky, so I will focus mostly on the inconvenience factor. If you are fat, you cannot even fit into a Ferrari. Same applies to parking big multihulls. Boats in the 40+ foot range may not even fit two 40 foot standard slips and how many end of pier berths are there? Mooring may be the only option. Shuttling supplies is a pain. As for haulout, some marinas on the Chesapeake will no even try to haul a wideboy due to worries about fragility of the bridgedeck-to-hull connection. So hauling may require a cruise to the nearest industrial strength facility. Doubtless, they will drop everthing to accommodate the needs of a noncommercial customer.

If you live in an icing latitude, you will be storing for more than a week tops, add the trouble and cost of running multiple water agitators all winter. Then there is draft. Most big multihulls (Gunboat excepted) have fixed keels that can draw 4 to 6+ feet. Thus, a big advantage of multihulls - gunkholing - is diminished. Wideboys also drag twin screws through the water which is anode fodder and compromises some of the speed that more sail surface promises. Smaller multihulls have outboards or drivelegs that can be raised when under sail. Lastly, anchoring can be a nuisance due to the greater hull sail surface and weight. Wideboys need more rode out, bigger hooks, and more anchorage space to swing.

[camaraderie]

As far as annual expense goes...a good rule of thumb is 10% of your invested value as pure maintenance...i.e. $30k a year on a 300k boat. PLUS dockage, insurance etc. etc.
New boats will need less maintenance for a while...and even older boats will have good years and bad years...but eventually you either pay it or lose it big time when you go to sell the boat and the surveyor finds blisters or core delamination etc.

[sailingdog]

Originally Posted by yellowwducky

Nope, but I am hoping that if you can afford the boat, you can afford to park it Just like cars, if you can afford a Ferrari, you don't ask about the price of high test gas versus regular. I am assuming this applies to boats as well.

That isn't always the case... a lot of the big, and very expensive powerboats at the marinas this year did very little traveling.

A 500,000-750,000 boat of 42-48 foot size (and 20-26 foot beam) for taking out of the water is what, 2,000 dollars? Keep it on land for a month is what, 3,000 dollars? Completely guesses here. Bad, yes, but you do that for anti fouling once a year and its on land for a week tops?

You've never priced a haul out for a 40'+ catamaran, have you???

Mooring, yea, that probably costs double what a monohull does? I keep seeing sailing estimates of costs with people claiming to get by on 6,000-10,000 a year! I mean, wow, sign me up for that, my rent is more than that a month! How bad could a mooring fee possibly be?

The people who are usually claiming to be getting by on $6000-10000 are often cruising with fairly spartan boats that are equipped to be mostly self-sufficient—ie, have the ability to generate electricity and make water—and are living at anchor for the majority of the time. I seriously doubt any one of them has a 40'+ catamaran...