Quick question from a moboer

[lisilou]

For any of you who were out on the Solent today, you all looked like you were having a whale of a time, with plenty of wind in your sails but watching you all (and trying to give you a wide enough berth at the same time of course ) I was trying to guesstimate the speeds of some. A friend reckons I'm way off in my guesswork when I said I reckoned some were pushing 12 knots. It looked very achievable to me but was my friend right when he said it was more likely to around 6 knts? Anyone out there today help me out here? Just curious.
Thanks
L

 

[rotrax]

If our boat reaches 7kts. in the solent we are well happy.

We plan passages at 5kts. average.

Some of the lightweight racing yachts with laminate sails could approach the speeds you estimated-our boat is a heavy, fat cruising boat.

 

[Firefly625]

Lisa, was not out today in a flappy thing, but knowing a bit about the dark side, a multihull will regularly achieve those speeds, mono hull rather less, indeed the "average" sail boat circa 25 to 45 ft would acheive between 5 and 8 knots as a general rule, 14knots would be for special occasions!

F10 through the needles channel wind over tide we reached 16 knots in a moody 419... That was a special occasion. Not to be repeated.

 

[mjcoon]

... It looked very achievable to me but was my friend right when he said it was more likely to around 6 knts? Anyone out there today help me out here? Just curious.

Usual expectation for a displacement (non-planing) monohull is ca 1.4 times square-root of length in feet.

Mike.

 

[lisilou]

Well I was way off then and more to my utter disgust...I'm gonna have to tell my friend he was right! (grrr). Thanks all, much appreciated.
L

 

[Bru]

Ah, perhaps it was a fleet of Anderson 22s out for a genteel jolly. As we all know they do 15 knots on an angels breath

(Sorry Andy, I just couldn't resist it!!)

 

[Tomahawk]

The big top notch racing jobs are good for about 8-9 kts on flat water, However with a bit of surf and going downhill, they will easily do 10 kts plus. You will probably be able to hear the screeching exitment from the crew above the sound of your engines :encouragement:

 

[Seajet]

lisilou,

actually your over-estimate is completely understandable; though the actual speed is low compared to mobo's, the sensation of speed, what with bow wave, spray, wind in the rig & feeling of power in the sails, heeling etc, it feels much faster !

In fact when I bought a fancy sailing dinghy catamaran years ago I was disappointed; though the thing was much faster than monohull sailing boats, it was all an academic exercise, I had to keep telling myself how fast I was going as with the pencil thin hulls there was no spray and sensation of speed.

You and yours really must try it some time !

 

[blackbeard]

Given flat-ish water and a decent breeze on the quarter, it's surprising how fast a sailing dinghy can go - even sedate-looking ones can get on the plane and go quite a bit faster than your average sailing cruising yacht

 

[dave_gibsea]

The foiling Moths can and regularly do 30Kts in the right conditions, some of the skifs will regularly exceed 20, I know the record for a 29er which is a junior boat is 24!

 

[Seajet]

I was generally talking in cruiser terms as that seems what lisilou was asking; but it will be interesting when Dan gets even his old Osprey going with a GPS onboard, never had such things in my day and the trail log only goes up to 10 !

 

[Ripster]

I was out on a J109 (35ftr) with every thing up no reefs pointing at about about 45 deg with new very slippery Carbon fibre sails in about 18kn of wind and we were doing about 7.5 - 8kn max and the helm reckoned the speedo was a bit ambitious.

 

[flaming]

I was out on a J109 (35ftr) with every thing up no reefs pointing at about about 45 deg with new very slippery Carbon fibre sails in about 18kn of wind and we were doing about 7.5 - 8kn max and the helm reckoned the speedo was a bit ambitious.

Only a tiny bit probably. We think we are slightly, only slightly, faster upwind than the 109s. My target speed in that breeze would be 7.1 at 37 -42 degrees TWA (dependant on chop).

 

[johnphilip]

The one that got away....

As this thread has progressed the speed achievable by a sailing boat has increased with nearly every posting.

 

[johnalison]

Some of the boats will be firing off on AIS, so you might be able to see what their ground speed is from that. Actually, testing your own judgement against reality is a worthwhile exercise, and we sometimes do the same thing re distance, which you can get from AIS or radar.

 

[Greenheart]

...it will be interesting when Dan gets even his old Osprey going with a GPS onboard, never had such things in my day and the trail log only goes up to 10 !

Thanks Andy, I hope she's still robust enough to be pushed that hard!

What you said about the sensation of speed, is critical. I recall a force 6 arriving at Bosham completely out of the blue, 30 years ago. With my sail unreefed, the Topper no longer wallowed noisily in a flurry of foam, but reared up and skimmed rather alarmingly for a hundred yards, before capsizing calamitously and pressing her masthead into the mud.

But the speed seemed to be almost beyond calculation. I suppose the Topper must have been edging towards eight or nine knots? Much less than newer, lighter and spectacularly over-canvased dinghies manage; all the same, I think the sensation of any substantial boat thrusting forward in the relative silence of sail-power, is palpably greater than higher speed in a slender-hulled catamaran, or much higher speed when accompanied by the racket of engines.

 

[Tidewaiter2]

Elderly Southerly 115, genoa and in mast main, Good Friday, off Ryde to Cowes, per GPS max speed 8.1kts, avg. 7kts, but the tide was with us

 

[lisilou]

lisilou,

actually your over-estimate is completely understandable; though the actual speed is low compared to mobo's, the sensation of speed, what with bow wave, spray, wind in the rig & feeling of power in the sails, heeling etc, it feels much faster !

In fact when I bought a fancy sailing dinghy catamaran years ago I was disappointed; though the thing was much faster than monohull sailing boats, it was all an academic exercise, I had to keep telling myself how fast I was going as with the pencil thin hulls there was no spray and sensation of speed.

You and yours really must try it some time !

My dad was a raggie thru and thru (his face when I told him we were going mobo was a picture! lol) so I was brought up on it but I could never get on with the 'sensation' and it used to terrify me when it healed. That was a fair few decades ago now so maybe you're right SJ...I should try it again if only to feel what it's like as the mobos thunder past.
L

Some of the boats will be firing off on AIS, so you might be able to see what their ground speed is from that. Actually, testing your own judgement against reality is a worthwhile exercise, and we sometimes do the same thing re distance, which you can get from AIS or radar.

Hi John. That's exactly what I was thinking re judgements. Don't have AIS myself so my guesstimates need a bit of fine tuning.
L