macd
Well-Known Member
I suspect they've evolved to have only a very small low pressure area in their wake, so not good for drafting (unlike Rob McElnea*)
* one for the two-wheeled petrolheads.
do dolphins slow you down
- Thread starter dylanwinter
- Start date
I suspect they've evolved to have only a very small low pressure area in their wake, so not good for drafting (unlike Rob McElnea*)
* one for the two-wheeled petrolheads.
Woodlouse
Well-Known Member
I believe dolphins are like rats in biscay, in that you are never more than 10 metres from one at any time.
macd
Well-Known Member
There are plenty there, but nowhere I've been has rivalled the Celtic Sea. Only place I've ever been tempted to write in the log "...and more bloody dolphins".
charles_reed
Well-Known Member
No, on the contrary I've run out of diesel twice, trying to keep up with the smartarse Smalls pod.
On the other hand they did me a good turn.
LadyInBed
Well-Known Member
do dolphins slow you down - Only when you have hooked one and are trying to reel it in 
ghostlymoron
Well-Known Member
This is a similar question to 'do wind farms reduce the amount of available wind?'
AntarcticPilot
Well-Known Member
No, the situations aren't comparable. A wind turbine extracts energy from a flow of air; by doing so it must (Laws of Thermodynamics) reduce the energy remaining in the flow of air.
The dolphin riding a bow-wave take energy from the wave, but the energy has been put into the wave by the boat causing it. So, the net result is that the boat uses the same amount of energy to create the wave whether or not a dolphin is riding it, but the wave loses energy to the dolphin so a wave ridden by a dolphin ought to have less energy than one that isn't. I very much doubt if there is a measurable difference; dolphins have extremely efficient hydrodynamics! The main point is that there is no feedback between dolphin and boat (unless it was VERY close to the boat's hull).
yodave
Well-Known Member
Dylan: There's a pod of six or seven including a baby around Anstruther - we enjoyed their company last week for an hour or so (photos on my blog). Perhaps you can do some tests while you're up there and let us all know?
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ProDave
Well-Known Member
I see them regularly and they are a delight.
I was sailing with a pal once, and all of a sudden he shouted "stop the boat"
I said "Why?"
he said "there's a dolphin under the bow you are going to run him over"
I carried on sailing enjoying it. The dolphin is much better in the water than I am and there's no way he was in any danger. They clearly love swimming alongside or in the bow wave of boats for whatever reason.
The highlight for me was seeing a mother and her baby (what's a baby dolphin called?) swimming in perfect harmony.
I was sailing with a pal once, and all of a sudden he shouted "stop the boat"
I said "Why?"
he said "there's a dolphin under the bow you are going to run him over"
I carried on sailing enjoying it. The dolphin is much better in the water than I am and there's no way he was in any danger. They clearly love swimming alongside or in the bow wave of boats for whatever reason.
The highlight for me was seeing a mother and her baby (what's a baby dolphin called?) swimming in perfect harmony.
AntarcticPilot
Well-Known Member
I remember one amazing moment in the 1960s. We were sailing my Dad's Halcyon south somewhere off Fife Ness in quite heavy weather - it was the end of a holiday, and we had to get back to Dunbar, so were sailing in rougher conditions than usual. I (in my late teens) was at the helm; everyone else was huddled up either below decks or sheltering at the front of the cockpit, looking aft. The Halcyon is quite tender, so from the windward side of the cockpit, I was quite often looking down into the water on the lee side. Suddenly, a large dolphin - probably a bottle-nose - breached immediately alongside the cockpit, just where I was looking. No-one else saw it; the weather was too rough to spot it any distance from the boat, and so I just saw it the once. If I'd leant over the side of the boat, I could have touched its back.
Perhaps that was an ancestor of the pod you know? It was roughly in the same waters, and Dolphins range widely.
ProDave
Well-Known Member
Some of the pod normally resident in the Moray Firth, were spotted this summer having a holiday in the Firth of Forth.
no28
Well-Known Member
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TSB240
Well-Known Member
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no28
Well-Known Member
Thank you, lovely to see.
dylanwinter
Well-Known Member
I have spent two nights brushing up on my Hydrodynamics and have worked it out - it was a real two pipe problem
Bow wave riding dolphins have the same effect as Bulbous bows. The bow wave of each individual dolphin pushed the bow wave of the vessel forward resulting in an increase in performance.
Dolphin has a Cp of around .5428 and a L/B of around 4.89972.
Stack three or four of these torpedoes on your bow and you are likely to see a S/l close to 1.782 of course depending on how many dolphins.
The S/L of each individual dolphin may vary but they take a square function of the boat speed so it evens out. The more dolphins the greater the predicted accuracy of the S/L increase. Obviously.
actually boat designer Bob Perry - his words
Bow wave riding dolphins have the same effect as Bulbous bows. The bow wave of each individual dolphin pushed the bow wave of the vessel forward resulting in an increase in performance.
Dolphin has a Cp of around .5428 and a L/B of around 4.89972.
Stack three or four of these torpedoes on your bow and you are likely to see a S/l close to 1.782 of course depending on how many dolphins.
The S/L of each individual dolphin may vary but they take a square function of the boat speed so it evens out. The more dolphins the greater the predicted accuracy of the S/L increase. Obviously.
actually boat designer Bob Perry - his words