An Interesting Interlude

[Guest]

Remember Sunday! East Coast, Force 3 southerly, Just collected my new aquisition - a Hunter 26.5 from Levington - en route to Burnham where I'm based, so long tack way out passed the Medusa, lovely sail - boat going like a dream, start on the reciprocal tack (heading about 270 degrees ) When we espied a yacht under sail with a helicopter (yellow) swooping in and hovering, was it a rescue? has the entire crew contracted foot and mouth? is there a yellow duster flown?, - no just the helicopter keeping station for something like 15 mins, and all the time I'm closing!! The chopper decides to do a couple of circuits and the yacht takes its sails down, and moves away to my port under power, mean while my crew and I settle down now that the exercise is over to discuss the excitement of the past half hour. The next thing we notice is that the helicopter is still buzzing about the yacht, which my crew member has identified as a sail training vessel, and the yacht is now unde power and heading straight for our port beam and by this time 400 yards away! (we are sailing at around 5 Knots still on a port tack) The Helicopter is again keeping station with the sail trainer on his starboard quarter at 50ft. altitude, and the water underneath him is in a turmoil from his downdraft, This sail trainer now within 50yds and closing fast , whats more seems determined to ram me! If I turn to port I'll hit him so I swung to starboard, jibed and now faced an ever changing vortex of downdraft from the chopper, well I let the main sheet loose, and was in a maestrom of wind and spray, which seemed to take 5hrs but was I suppose 5 secs. in passing, the question is, was my craft and crew in real danger from the down draft from the helicopter? and as this was an obvious training excercise I would not expect them to involve any outside craft. Whats your views!!! PS I did have my radio on, on Ch 16. but heard no calls to me during the whole excercise advising or instructing me of their intentions, The radio was in the cabin however and inaudible over the noise of the helicopter.

 

[Guest]

Re:Yes you were...

in real danger. Helicopter downdrafts have been known to rip loose objects out of boats, sprayhoods, warps, fenders,washboards charts etc. Get hit by one of these and you'll be hurt.

Normally rescue you should keep clear of this kind of excercise, both as a courtesy and out of self preservation. They're so well managed as a rule it's unusual, and sloppy, for the kind of situation you experienced to develop.

Tom

 

[Guest]

Re:Yes you were...

Years ago I was sailing my 24ft Trident (just in a very light breeze and flat sea, pinned home, beating to windward) across Lyme Bay, watching Ark Royal on a parallel course about a mile away flying aircraft on and off.

A Wessex approached, hovered close to starboard, had a good look then turned away back towards the Ark.

The downdraught nearly flattened us and a crew member was thrown across the cockpit, bruised and sprained an ankle.

After correspondence with the Admiralty I was informed that the pilot of the helicopter had been reprimanded and taken off flying duties. Apparently, just before turning, he had laughed and said to his crew "Watch this for a laugh!"

It was a glorious hot sunny day, a light breeze and the injured crew member, only dressed in a bikini, was a non-swimmer.

 

[Guest]

Think about the mechanics (apologies in advance if I'm wrong - this is off the top of the head). If the Wessex weighs (say) 10 tonnes which is held aloft by its wings you can work out roughly the force on your sails. The wing will generate about 2/3 lift in upward low pressure above and 1/3 lift from below, so you get 0.33 x 10 tonnes divided by the area swept by the rotor. If that area is about 4 times your sail area (??) you'll get up to (depend on your heel) 0.33 x 0.25 x 10 tonnes on your sail - 0.8 tonnes. What do you think? Will that tip you or give you a good acceleration boost?

There's a lot of assumptions in this of course and I look forward to someone refining the maths, but it ought to be in the right order.

Sorry RK - couldn't resist it!! DB