Picture Quiz

[marese]

Dave,

I also think the quizzes are great, especially for beginners/improvers. Latest edition of Tnd also great, am a bit worried about flying slates though, and can\'t figure out how much use Dave C would be if the roof did cave in unless he takes in the homeless!!!!

[Dave]

Could the klaxon be from a fire station in Balbriggan?

[DavidH]

Interesting excercise - I\'d have brought my GPS.

What about getting run down by a larger faster boat - anyone have an audible warning \'foghorn\' with them? I\'ve been in a similar situation near the Copelands - and hearing the sound of the fast ferry approaching can loosen the bowels! What are the \'rules of the sea\' on kayaks in thick fog near shipping lanes/harbours? If possible I would prefer not to be caught out like that again!

See Section III - conduct of vessels in restricted visibility (Rule 19)

Interesting debate David!

PS the magazine is exceptionally good - the Group Dynamics article was excellent - ACKC of course have always been strong at maintaining group morale and group hug stuff!

[DaveWalsh]

Some people are losing sight of the known the facts. The group saw and heard the lights/klaxon/tannoy after 1.00 hours. Ten minutes later they heard the siren, at 1.10 out. They landed after 1.30 hours.
Therefore there were two events at sea, not three, AND, 2 hrs 40 mins doesn\'t come into it.
Everyone is agreed that they were swept north. The big question surely is first, what are the parameters as to how far north a tide can push you in 90 minutes, second, with the info as to lights klaxons and sirens, does that pin it down a bit more. AND, in each case, WHY.
Slates being taken off people’s houses happens when they don’t or can’t pay their bills and are in deep trouble with the law, a situation best avoided really. Its an old saying, young people wouldn’t understand. I was attempting to encourage everyone to get certified to the best of their ability. The piece of paper may save you or your friends a bucket load of trouble some day.
Anyone alleging that ACKC is into the group mollycoddling suggested in the Adler article is a knave or a fool.
DWalsh

[brianforrest]

ok I\'m going to stick my head above the parapet................

Rock to Skerries RNLI is 265.5(T) or 272magnetic but hell let\'s call it 275(M). The lads headed in not correcting for the tide.

At 2 to 3hrs into a spring flood you\'d need to allow 0.75Kn. It\'s 4knM Rock to Skerries - your drift is going to be 2knM. That has you headed in at 227(M). Which has your boat pointed about 1km south of Shenicks on the map!

The lads landed in Balbriggan.

Lights what lights? Unlikely to be the pittiful red flashing light on the Perch (bouy out from Skerries RNLI). The other lads (RNLI) were clearly open for business that evening - their floodlights would have been on and showing on the left if steering 275(M). Klaxon / Tannoy - ever been near an RNLI rib thats operational? The VHF\'d burst your eardrums! The tannoy was either coming from the rib on the slip or from the RNLI boathouse. Noise carries along way in the conditions described. The RNLI \"confirmed the sound as being correct\".

Sirens? It doesn\'t say which direction the siren was coming from. There are Fire Stations in both Balbriggan and Skerries - the one in skerries is only 1 street back from the beach after the harbour on the left. There are also Police stations in both towns. The \'police\' could have been coming / going to anywhere! Again a siren would travel a long way in the conditions. Dependant on direction of sound they were probably right to ignore it.

On balance better to aim-off and be sure of hitting your target than miss it - that is, if anything over compensate and hit south of Skerries rather than put more than an hour of paddling on your trip (30mins extra out and \'handrail\' back).

3 in the group? Have two paddling line astern on the same bearing and the remaining paddler checking. Impossible though when you only have one deck compass between you!! Alos given the severity of the fog probably not practical.


STOP PRESS..................................
The suspected author of this puzzle and great protaganest of \'scenarios\' was spotted this very evening having a solitary rolling session in Skerries Harbour. Hmmm....must be expecting dodgy conditions this weekend!

[EMurphy]

You seem desperate for an answer at this stage Dave so I\'ll put you out of your misery and suggest you go to Sheet No83. Have a look at that horse of an island just off Ballinskelligs Harbour.

Eileen

[brianforrest]

Hah! Noone spotted the deliberate mistake. erratum - drift is 3knM not 2 (4 at 0.75kns).................

[DaveWalsh]

Brian Forrest is seriously confused, unless of course we were to spot the deliberate error he repeated. In one and a half hours at 0.75kn, the drift factor is 1.15 nautical miles, not 2 not 3 and certainly not 4. The distance out they started from is irrelevant. They were in a drift of a certain strength for a certain time. That’s all that matters.
Also, no-one has described a reliable methodology for retracing the steps of this group. Forensically looking backwards at known facts so as to figure what did happen and why is a different operation altogether to planning to get things right. Some are speaking of both operations as though they are the same.
Also, no-one acknowledges that their guess is approximate only, within parameters, indicating how the sights and noises on the water make them favour one end of the spectrum over the other?
I’d like to have a go myself, and I might if others are finished ? I have enjoyed knocking other people’s theories. Perhaps its time to let people knock mine ?
And well done Eileen. I agree its Horse, with its pirate cove clearly visible, and where urchins abound. Are we right quizmaster ?
DWalsh

[brianforrest]

Conceded. The target is 1hrs paddling with a north going flood left to right - aim-off 0.75knM south.

D\'oh! Yours confused and headless.

[DaveWalsh]

Here is my best effort, and I know that after handing out stick the last few days, even been unkind, I will get it in the neck for any slip up. Also, the enthusiasm I showed for this quiz seems to have led some folk to believe I set it. I didn’t. I don’t know who were the party. I just love these things. Anyway, here goes.
By the time the group were leaving Rockabill coming back, the tide was fairly strongly into the flood. I would guess its direction as NNW/NW hugging the coast rather than absolutely N as most assumed. That actually doesn’t make much difference, but purists, please note. In fact the tide jinks and varies round the islands and eddies in the bays, but NNW/NW would be average, and does well enough for the first hour of this journey anyway.
Now these guys made no effort at all to lay off for the tide. If they had had slack water they would have hit Skerries beach about halfway between Skerries and Balbriggan. My guess is they simply reversed their plotted course out, when they laid off for the ebb (095 out = 275 back) ? Because of this oversight they got dragged even further north up the coast.
To prevent that, they should have wound down the course to steer. They didn’t, but that isn’t one of the questions asked. We are asked what happened to them, and knowing the facts, we are asked to rationalise it all with hindsight.
If we know the duration they were on the water (we do), and the direction of the flood (we do, approx), and its strength (we do, very approx), and the course they steered (we do approx, their word anyway), figuring out where they should end up after a given time is theoretically straightforward. Yachties call it “dead reckoning”. Here is how you do it. Begin by drawing a pencil line on the map from Rockabill NW/NNW the distance the tide dragged them in the 90 minutes they were out. I always work back towards kilometres because I like OS maps. I guess that distance conservatively at 3km and less conservatively at 4km. Assume the flood was at 1.00kn at least, possibly a tad more, but not less (where does BF get 0.75?). I convert that then on the basis that 1kn for 90 minutes – 1.5nm = 1.75 land miles = = 3km , very approximate I know, but everything in this game is. The whole thing is that it is as though they began their journey downstream of where they actually did, and then paddled on slack water. Look at the map. Its as though they set out, not from Rockabill on gridline 625, but more like 650 or 660, and closer a bit to land, maybe on the 300 grid, about 10km offshore.
Now draw another line. They steered just a whisker S of W, just under the 270 degrees, so when they hit, they would have gained a tad of southing, and my guess is they would have hit just at Balbriggan, say 645 or 655.
Now the ability to steer a compass course in mist for an hour and a half in a kayak is limited even by day. My own experience is that a steering error factor, by day, of five degrees has to be allowed for. So the reasonable parameters would be even worse, Balbriggan 640 to Gormanstown 665, by day. Worse again if you show sympathy for their inaccuracy at dusk/night, but lets ignore that for now.
So now do the land topography or especially the noises and sights they heard and saw en route help in all that. Would anything in all that make you favour the southern or northern end of that spectrum ?
Draw another few lines, from Rockabill in each case to Balbriggan and to Gormanstown and the other possibles, 640, 645, 655 and 665. These represent possible routes the group took. They saw/heard the lights/klaxon/tannoy 60 minutes into a 90 minute trip, so mark a spot 6/9 the way in on each line, and they heard the siren another 10 minutes in, so mark another spot 7/9 the way in.
Notice that in all cases they were well out when they saw and heard the lights/klaxon/tannoy, but there is absolutely nothing out there. On any route parameter they should have been all alone. So whatever they saw/heard has to have been a boat. There is an unsubtle hint in the text that it was an RNLI boat, a big one too, but that is irrelevant. It was a boat, so it doesn’t matter where it might have been, RNLI or not. It could have been any boat anywhere. It is entirely irrelevant.
The second incident, the siren, is more interesting. The more you hypothesise they might have been dragged awful far north, the less you can imagine hearing a siren. There is no town up there and the road goes inland. If they were more south though, coming into Balbriggan say, they would have been just off a projecting housing estate called Isaacs Bower, maybe 1km out, a siren hearable surely. Emergency people use sirens to tell others to get out of the way, and for no other purpose. So they aren’t used or needed in remote spots. And absolutely not at sea. On land only, and then in congested areas only. What sort of siren is irrelevant. If they heard a siren they were near land, with a road, and probably a built up area.
Consider also the topography. There is a projection of land 2km north of Balbriggan with a set of rocks off it. It is difficult to see them missing that target altogether, and its remote up there, no place for sirens at all. No way they ended up north of there.
So it pains me to say it. I agree with that leading light in the Irish Sea Karrahering Association, they arrived in Balbriggan, most likely its north side, at about gridline 645.
By the way, you can judge sound direction quite well in mist I find. They should have trusted their sense of direction and headed for the siren is my guess. They probably considered but rejected as OTT ringing 999 after being nearly run down. I have the feeling they mightn’t be so reticent again ?
How to avoid all this happening is of course an entirely different project. It is necessary to lay off, bear up into the flow, ferry glide, there are many terms. How much to bear up is the real and everyday challenge. 240(M) was about right, though you could argue for 235. The calculations made by some contributors weren’t bad, but again the methodology wasn’t always apparent and in at least one case, unsatisfactory, but then kayakers in kilts, who trusts ‘em?
The calculation depends on knowing or guessing the speed of the tide and the speed of the kayaks. How to calculate all this, without a calculator, in your head, paperlessly, while sitting in your kayak off Rockabill, is, I understand, about to be made ridiculously simple in one of the talks at the forthcoming Symposium in Mullaghmore next month. I can’t remember who is the speaker, but I am assured he is absolutely wonderful.
DWalsh