AGM 2012

Viewing 15 posts - 41 through 55 (of 55 total)
  • longa
    Participant
    Post count: 472
    #5027 |

    Interesting indeed. Where is this analysis Jonathan?

    Fat Git
    Participant
    Post count: 342
    #5028 |

    It’s a long way from the subject of this string but here you go. http://www.landforms.eu/shetland/Library/Hall_Hansom_Jarvis_2008.pdf

    Anonymous
    Inactive
    Post count: 88
    #5023 |

    I was keen to see how this rock removal worked so I spent a bit of time studying it in real time. Here’s a brief outline.

    I observed that as the waves ran up the ramp they lost very little power and some wider swell almost gained speed due to the funneling effect of the two walls leading up to the hole. As the water pushes through the narrow restriction an updraught from the hole forms a cushion of air that gets trapped under this weight of water- likley several tonnes and forces the water to again accelerate. When this volume of water is finally slowed from hitting the obstruction that is the stepped area around the pool the air beneath the water pushes its way up with explosive force and lifts the blocks with relative ease. The larger swells easily capable of lifting and moving one tonne+ blocks across the 25m pool area.

    I have this written in detail if anyone is interested and it is my original work so is covered by copyright and not for unauthorised reproduction. I’ve added a couple of photos that show this wave action at work and the same copyright applies to them.

    I’d recommend getting out to see this if you can handle the abrasive weather and don’t mind dodging the flying boulders of several pounds that whip past whilst being engulfed in heavy spray! Its also not great for photographic or video equipment!

    Anonymous
    Inactive
    Post count: 88
    #5012 |

    You can see in image 1 the water is level with the left wall of the crag, about 12m high. In image 2 as the water volume colapses over the hole the air cushion escapes from the front of the wave. If you go to see it this rush of air can clearly be heard and sometimes produces a vapour rather than a spray, it’s quite unusual.

    The third photo in the sequence was of me running away so much less interesting, as such I didn’t post it. 😛

    longa
    Participant
    Post count: 472
    #5013 |

    Very good. The water presumably draws water up the hole by Bernoulli’s effect which then increases the flow, reducing the pressure so that the rocks are effectively “sucked” out. An interesting idea, in complete contrast to the classical “water-hammer” effect. Maybe this is mentioned in the paper – I’ve only glanced through it.

    The hole acts like a slat on the leading edge of an aerofoil section, delaying boundary-layer separation and reducing induced drag…………….(wanders off muttering into grey beard)

    Al
    Keymaster
    Post count: 860
    #5014 |

    Nice one Paul. I’ve just added another photo from Dec ’11. As you can see I was considerably closer (read: more stupid) in my survival suit! Ha! I was being constantly drenched and got a bit too close on one occasion. After 30 minutes, and now completely sodden, I wandered back. My brand new camera had done well, but unfortunately my pocket had filled up with seawater. End of camera… Maybe get a waterproof one next time!

    Shame it was dusk really – was all a bit blurry. Plus it was a case of point-shoot-duck.

    Al
    Keymaster
    Post count: 860
    #5015 |

    OK, after that slight deviation, back to the AGM! You should have all received an email about the AGM/Social/Voar Redd Up weekend

    I need to know numbers for the food, so please let me know, preferably by adding a comment to the news item.

    Bina, I’ve promised that the agenda will be up on the site a week beforehand – hope that’s ok! Email me it once you’ve done it and I’ll put it up.

    Anonymous
    Inactive
    Post count: 88
    #5009 |

    Just quickly on the Grind rock action, Andy, I think the hole acts like a piston, as water is forced through the subtterranean and begins to fill the hole from below the large volume of water from above doesn’t fall but is forced forward on a compression of air then with a sound similar but much louder than the canon south of Eshaness it blasts up around the pool area.

    This doesn’t happen very often, possibly only once or twice even in the ideal storm, but I have been fortunate enough to see it.

    The massive volumes of water that run up the ramp (See Al’s photo) generally don’t do the damage due to them being in the wrong direction for the subterranean and the hole to play its part, they do however move the lifted blocks back across the pool. Too much energy is removed from the lower part of the wave as much of it drops into the hole when the piston effect is not in play. From what I’ve seen when there in optimum conditions it would be possible for a significanty smaller wave to punch a 250kg block clean over the pool!

    Anyway, back to the AGM.

    (could always lift this to a new thread Al?)

    Al
    Keymaster
    Post count: 860
    #5077 |

    Agenda now online (thanks Bina). Add a comment to the news item if you have anything to add. Food is organised but just to remind you that you need to book camping/wigwams yourself.

    longa
    Participant
    Post count: 472
    #5078 |

    Thanks for letting me know!

    longa
    Participant
    Post count: 472
    #5080 |

    Could anyone who’s not paid their membership yet please do so. I need to send off the stuff to the MCofS. If you’re coming to the AGM could you bring your cash/chequebook with. PERLEES!

    Who’s coming now? Are we OK for transport etc?

    Al
    Keymaster
    Post count: 860
    #5081 |

    There are quite a few going from town/Bressay so probably worth sharing lifts. Don’t know who’s staying over though.

    pete s
    Participant
    Post count: 355
    #5090 |

    ive got hold of a set of sherelegs (just like the coastguard clif teams use!)handy for hauling bags.

    L’escargot
    Participant
    Post count: 142
    #5091 |

    At what time are we meeting up and where exactly?

    Al
    Keymaster
    Post count: 860
    #5092 |

    Climbing on sat: see other post
    Food @ 5pm
    AGM @ 7pm
    Sunday VRU: meet @ lighthouse 10am?

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