Latest News: Forums Technical Stern crutch design

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  • #3856
    Anonymous
    Inactive

    Please could somebody point me to a design for the stern crutch needed to hold the boom up when using a Mk 1 tent?

    #7707
    Swiebertje
    Participant

    I have one here in PDF format. I shall email it if you pass me your email address off list (through the personal message system).

    #8495
    tempest51
    Member

    Swiebertje old chap,

    I received your photos regarding the mast crutch you made, and excellent they were too. I have a lingering question as to how the whole arrangement stays in place, for example, the bottom of the legs? How exactly are they secured to stop them moving around. I can understand that the top of the crutch holding the boom can be strapped securely, but the base defeats me.

    Regards,

    tempest51

    #8496
    Swiebertje
    Participant

    The base fits the “gutter” exactly and wedges in it. It is stable enough to keep it upright. The whole package is stabilized by the boom’s weight and the pressure from the main sheet. Once the sheet pressure is on the legs cannot slide inward, only outward, but the gunwale prevents them from sliding outward. The crutch can’t slide forward or backward because it is wedged in the “gutter” (It is a MK1+S boat).

    To prevent the boom from sliding backwards and slip from the goosneck, I usually yank the downhoul taut. This too creates a small down force on the crutch that would hold it in place should the main sheet come loose. And finally the weight of the boom tent and the fact that the tent is it is tensioned to the gunwale also keeps the crutch in place.

    #8498
    Dave Barker
    Keymaster

    I’m just putting together a Mk1 tent and have decided to try managing without a boom crutch, using a bridle and topping lift instead. Can anyone think of an argument against this arrangement?

    #8499
    Swiebertje
    Participant

    Yes, the weight of the tent, helped by a good gale wind and some sheet tension will overload the mast top and create a permanent bend. Remember that the Wayfarer has a 3/4 rig (or is that a 5/8 rig?). The mast top is not supported by stays or shrouds. Also the mast is made to bend easy to flatten the sail. Basically it is a racing mast. Such a light mast is easily overloaded without proper support.

    While setting the tent it is virtually impossible to adjust the topping lift, the mainsheet and kicker such that the boom is in the exact position the tent requires. With a crutch it is a no brainer.

    I use a topping lift only while cruising and to avoid fouling the helm and engine. As soon as circumstances allow I replace the topping lift by the crutch. While the boom is on the topping lift I take care not to put any tension on the mainsheet and kicker. With the mainsheet loose and no kicker, the boom does swing about a little. But rather that then damaging the mast. Basically I need the topping lift only if I need to switch from sailing to motoring in a hurry. In all other cases I try to avoid using it.

    Two pieces of wood and some paint seem a small price to pay compared to a new mast. And the crutch stores easy once folded.

    A crutch is also helpfull in lowering the mast while shooting bridges or while removing the mast if you have a compass on it that, due to a stubborn builder, will hit the CB horn when the mast is lowered.

    By the way, my topping lift is at the mast top for it is also my spare halyard. Some use a topping lift at the hounds where the mast is supported by the shrouds and forestay. Perhaps you could do without a crutch if your topping lift is at the hounds, I am not sure. Still, it would be easier to use a crutch with a tent. Just think of the forces on the rig when the tent is set and the topping lift taut while on anchor in a gale wind and 2 feet waves…….. I wouldn’t sleep well, but I would with a boom crutch.

    #8500
    tempest51
    Member

    Thanks for that Swiebertje,

    I thnk my MK1 composite may have a slightly different aft deck design to your +S, which may account for my confusion with understanding how the crutch stays up.

    Tempest51

    #8502
    Dave Barker
    Keymaster

    Hi Swiebertje,

    I should have clarified that I don’t have (or intend to use) a separate topping lift – just the main halyard re-assigned to the end of the boom at night.

    The Mk2 hooped tent currently offered by Rob Wagstaffe requires the weight of the tent and boom to be taken by such a topping lift. The stern hoop isn’t strong enough to bear any significant weight. I have spent a number of weeks sleeping in such a tent and although I can’t deny having any sleepless nights, none of them (yet) have been for fear of bending the mast. Perhaps I will now begin to worry about that…

    Personally I doubt whether I would sleep soundly at anchor in a gale and 2 foot waves, but if tired I might do.

    Thinking aloud, I ought to make myself a decent boom crutch – I have a rough and ready one for bridges, but it’s poorly designed and the wrong height for the tent. I suspect the mast is plenty strong enough, but there is no need to take the risk, certainly when using the new (Mk 1) tent. The Mk 2 may be a different matter – I’m not sure until I’m back with the boat tomorrow.

    I appreciate your feeedback.

    #8503
    Swiebertje
    Participant

    Well, at least use the spinnaker halyard as a topping lift. Because it is at the hounds where the mast can take much more abuse without risk of bending it permanently.

    You may not be sleeping in it if it gets rough but the tent and the rig will still get a pounding if you are at home sleeping. I would sleep better if the tent and boom rest on a crutch rather then on a topping lift. BTW, we haven’t discussed chaffing of the topping lift yet…. 😉

    #8504
    Dave Barker
    Keymaster

    we haven’t discussed chaffing of the topping lift yet….

    Now I will not sleep a wink! 😆

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