Boat speed

Mr Cassandra

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Hi
I own a Jeanneau 44 foot cruiser /racer in about 16 -17 knots of wind it will achieve it boats speed of 8.4 -8.6kt without a reef.

How can a Benny First 38 footer be able to be faster in the same wind speed, as was said in a threads below .I know it carries more sail and a deeper fin. But how can it get above it water length speed?
I sail in the med so little surfing ,just true boat speed
 

Twister_Ken

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Hi
I own a Jeanneau 44 foot cruiser /racer in about 16 -17 knots of wind it will achieve it boats speed of 8.4 -8.6kt without a reef.

How can a Benny First 38 footer be able to be faster in the same wind speed, as was said in a threads below .I know it carries more sail and a deeper fin. But how can it get above it water length speed?
I sail in the med so little surfing ,just true boat speed

It's not LOA but LWL when sailing that counts in determining max theoretical speed. Have you compared them? My Twister had a static LWL of 21' but more like 25' when sailing on the wind.
 

Pagetslady

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is that speed through the water or in the case of the 38ft SOG with tide ? is his or your log correct who knows boat logs are not often 100% Perhaps he likes to think his boat is faster than it is and has his log cranked up a bit. Does it really matter.
Mike
 

Mr Cassandra

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It's not LOA but LWL when sailing that counts in determining max theoretical speed. Have you compared them? My Twister had a static LWL of 21' but more like 25' when sailing on the wind.


Hi Ken
Yes My boats LWL increases by 3ft when on the wind.I am not sure about comparing with a First 38 but would think I am longer?
 

E39mad

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Too many variables here to assume the 38 is definately faster than your 44 footer in the same conditions. Initially the log may not be calibrated or the paddlewheel is too high on one tack and spins faster! Also how clean are each of the hulls, who has a feathering/folding prop? What are the weight to sail area ratios? What sails did each boat have - cruising set up (furlers) or a full set of racing headsails and main?

Modern hulls can be very slippery so not doubting totally that the 38 is faster as extra waterline length does not always equate to extra speed!
 
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Mr Cassandra

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is that speed through the water or in the case of the 38ft SOG with tide ? is his or your log correct who knows boat logs are not often 100% Perhaps he likes to think his boat is faster than it is and has his log cranked up a bit. Does it really matter.
Mike


Hello
Its not a case of" My" boat faster than yours I just want to know how a shorter sporter boat can go faster than it water line length speed in the same amount of wind without the aid of tide or surfing I allways have two GPS on so not paddle wheel or hull clean problem "It How can a shorter boat go faster"?
 
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flaming

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Hi
I own a Jeanneau 44 foot cruiser /racer in about 16 -17 knots of wind it will achieve it boats speed of 8.4 -8.6kt without a reef.

How can a Benny First 38 footer be able to be faster in the same wind speed, as was said in a threads below .I know it carries more sail and a deeper fin. But how can it get above it water length speed?
I sail in the med so little surfing ,just true boat speed

There will be surfing in the med - I know we often surf in the Solent, which I'm told is slightly smaller than the med.
here's a friend of mine on her mini transat in the med. Those waves look surfable to me!

http://www.youtube.com/user/pipoceanracing?feature=mhsn#p/a/u/2/TsTVmyYYaoo

I love these threads about boat speed, as some of the claims are completely unreal. If you race, you get a really good idea of how fast you actually go.
However, I do believe those speeds if we're talking downwind, we (37 foot cruiser racer) would expect those speeds with the kite up, perhaps more.

Hull speed is not a definite, as it simply marks the point that the bow wave is the length of the boat, and any further increas in speed will result in then bow wave being longer than the boat and the boat essentailly having to climb uphill.

"Slippery" hulls produce less of a bow wave, so the steepness of the wave that the boat then has to climb is less. So where fat boats really do hit a wall, sleaker sailing boats are able to excede this number, if they have the stability and sail area to generate the necessary power to get up that wave.
Some have bags of power, and really get up and over the wave, and that's planing. Some merely have a bit more, and they just go a little bit faster, essentially sailing uphill.
 

Seajet

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The waterline length rule has been consistently proven to be bogus.

My 22' boat has averaged just over 7 knots across the Channel, in a broad reaching F4-5; admittedly perfect conditions but still 'against the laws of physics, Jim ! '

My boat, 19'3" on the waterline, has repeatedly beaten well sailed 34' + boats, in non-surfing conditions; a lot has to do with low windage and penetration through waves ( combination of hull shape, weight disribution - not necessarily light if beating into waves, and rig - , nothing to do with me being a wonder-sailor or something, but the smaller a boat gets - for offshore sailing - the better the design has to be...
 
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doug748

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Take all these speed claims with a pinch of salt.
It is easy to see two figures on the magic screens and recycle them as fact. My personal best is 11kts on the screen in 30kts of wind on a 24 ft waterline. Does this disprove the laws of Physics? No, It just shows how frail is humanity in the face of temptation
As Flaming has said, If you really want to know, look at the racing results/handicaps. The Round the Island stats are often a good starting point for your investigations. You may end up asking yourself why all these brilliantly fast boats end up at the back of the fleet.
 

flaming

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The Round the Island stats are often a good starting point for your investigations. You may end up asking yourself why all these brilliantly fast boats end up at the back of the fleet.

And take 2010 as a good indication of light wind performance, and 2008 as a great indication of high wind performance. Take 2009 with a lorry load of salt - due to the massive park up at Bembridge.
 

snowleopard

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The 'hull speed' limitation is a very flexible thing. The formula K x sqrt(lwl) can give very different values depending on hull form. For a start you have all those pre1960 boats with long overhangs so as soon as they start to move the LWL increases considerably. The 'constant' K, often given as 1.4 actually varies depending on hull form.

Then we get the circumstances where the hull speed can be totally overridden: surfing is one, the others are planing which is now fairly common with wide flat aft sections of modern designs and the very narrow hulls, particularly of multis. Once the length:beam ratio exceeds 8 the hull speed formula no longer applies and, within limits, piling on more power continues to increase speed because the speed/resistance graph is relatively linear as opposed to the J-curve of heavy displacement monohulls.

Then we come to exaggeration - did you actually see this 38 footer sail past your 44 or was it claims in the club bar?

I passage plan on 7 knots but I have had Prout owners making claims of 9 knots which could lead one to think they are the faster boats but I've yet to be passed by one!
 

Mr Cassandra

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Can i try again please .
My 44footer in 16-17 knots of wind no tide will make 8.4 -8.6 on the GPS`s close -hauled/ close -reached
Can a faster design boat say a First 38 go faster than 8.4- 8.6 in the same conditions.?

I am not saying my boat is faster than yours.I have had 13.9 on the GPS but that was in over 40 knots of wind and is not the question.
 

flaming

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Can i try again please .
My 44footer in 16-17 knots of wind no tide will make 8.4 -8.6 on the GPS`s close -hauled/ close -reached
Can a faster design boat say a First 38 go faster than 8.4- 8.6 in the same conditions.?

I am not saying my boat is faster than yours.I have had 13.9 on the GPS but that was in over 40 knots of wind and is not the question.

Not if you actually mean upwind, as in sailing upwind at your optimum VMG.

But then I don't believe that your 44 footer can do that, as I think that might actually be faster than a Farr 45 goes upwind...

But assuming you mean close reaching... No, I don't think a first 38 (which has to be at least 10-12 years old...?) can go faster than that white sail reaching in 16 knots of wind. I'd expect somewhere between 8 and 8.5.
 

johnalison

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I wish I had earned a pound for every time someone told me about some high speed they've achieved, only to tell me later that it was on the GPS. There may be no tides in the Med but I would be surprised if there are no currents, as there certainly are in the equally tideless Baltic. There are a few places in the Baltic where currents of a couple of knots occur, but it is common to find nearly a knot and in my opinion only a calibrated log will do, if there is such a beast. My log is calibrated by me to read correctly at about 6 1/2 knots but I know it over-reads at higher speeds.
 
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I love these threads about boat speed, as some of the claims are completely unreal. If you race, you get a really good idea of how fast you actually go.
However, I do believe those speeds if we're talking downwind, we (37 foot cruiser racer) would expect those speeds with the kite up, perhaps more.

.

I agree. Most people make claims that at best are figures seen intermittently as a wave passes underneath, and whats more seen on inaccurate / non checked logs.

That said there is a world of difference between a cruiser, even a sporty one, and a boat like a First or a J boat. Those sort of racer cruisers have low weight , well shaped and usually narrow hulls and big sail areas. Even then the big difference in performance seems to be either hard on the wind or on a run, and particularly in light airs
 

cmedsailor

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Hi
I own a Jeanneau 44 foot cruiser /racer in about 16 -17 knots of wind it will achieve it boats speed of 8.4 -8.6kt without a reef.

How can a Benny First 38 footer be able to be faster in the same wind speed, as was said in a threads below .I know it carries more sail and a deeper fin. But how can it get above it water length speed?
I sail in the med so little surfing ,just true boat speed

Are you talking about the Beneteau First 38, designed by J.Berret and built in the 80's? Because despite the name it's not a 38 footer.
From Beneteau official site:
Overall Length 12.25m
Hull Length 11.75m
Waterline 10.32m
Beam 3.90m
Draft 2.10m
Displacement 7100kg
Ballast 3000kg

I have sailed one lots of times (including races). Going upwind, there's no such thing as "round up" no matter how aggresive you are (it's an amazing boat).
Flying a spinnaker in 20knots and 2 meters wave in the Med (not in a racing mode!) we saw speeds (occasionally; 9-10 was more common) of around 13-14 knots surfing down the waves.
 

sighmoon

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To faintly echo what snowleopard said:

Hull speed is proportionate to the speed of the wave the boat sits in, which in turn is proportionate to the sqrt of the wavelength of that wave.

For some hull forms at displacement speed, the wavelength approximates to the waterline length. But if a boat had a long straight run aft, and wide enough aft sections to stop the stern squatting, the wavelength could be longer than the waterline length. Correspondingly, a double ender is likely to produce a wavelength (and hence hull speed) shorter than waterline length suggests.
 
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