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26-10-2017, 03:04
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#46
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Registered User
Join Date: Feb 2010
Posts: 897
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Re: Lagoon 42 loses mast
Quote:
Originally Posted by Lagoon42
En français car je ne connais pas le mot anglais je parlerais de "mise en résonance"
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My poor french translation is "resonance / vibration due to useage". C'est tout?
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26-10-2017, 03:15
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#47
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Registered User
Join Date: Oct 2017
Posts: 7
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Re: Lagoon 42 loses mast
Cela peut-être une cause en plus
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26-10-2017, 04:47
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#48
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Moderator

Join Date: Aug 2009
Location: Solent, England
Boat: Moody 31
Posts: 18,717
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Re: Lagoon 42 loses mast
Folks, the forum language is English.
Regards
Peter
Moderator
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26-10-2017, 06:46
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#49
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Registered User
Join Date: Feb 2006
Location: Eastern Caribbean for the 2020 season then east coast or Panama
Boat: Lagoon 470 cat
Posts: 701
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Re: Lagoon 42 loses mast
Re-tensioning the shrouds is always easier when sailing instead of at the dock. Just sail hard on the wind or close reach and tack slack out of leeward shrouds. Tack and repeat the process. Less load on the turnbuckle threads and worker. Much easier than trying to do while at the dock.
Bill
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26-10-2017, 07:05
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#50
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Registered User
Join Date: Dec 2010
Location: W Carib
Boat: Wildcat 35, Hobie 33
Posts: 13,500
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Re: Lagoon 42 loses mast
Quote:
Originally Posted by Moontide
Re-tensioning the shrouds is always easier when sailing instead of at the dock. Just sail hard on the wind or close reach and tack slack out of leeward shrouds. Tack and repeat the process. Less load on the turnbuckle threads and worker. Much easier than trying to do while at the dock.
Bill
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Most pro riggers do a static (at dock) tune and then a dynamic (under sail) tune.
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26-10-2017, 09:13
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#51
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Registered User
Join Date: Jul 2016
Boat: lagoon 400s2
Posts: 53
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Re: Lagoon 42 loses mast
Quote:
Originally Posted by Lagoon42
It is a reply comment by à sailor in a other forum:
No one injured... Great news !
However, I've noticed the rigging is getting loose with sea condition over 2/3 meters high due to high excessive shaking of the rigging under load on the new models 39, 42, 52s I have been sailing recently. (shroud and stays must be monitor from close after each day).
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Interesting ... all 3 these models (39, 42 and 52) have a mast that is positioned more aft than other Lagoon models
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26-10-2017, 15:33
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#52
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Registered User
Join Date: Feb 2010
Posts: 897
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Re: Lagoon 42 loses mast
Quote:
Originally Posted by Lagoon42
Cela peut-être une cause en plus
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"This may be a cause in addition"
Sorry Pete, thanks for doing your job. I won't keep up the crap translations, but many are very keen to know the reason for Lagoon42's dismasting.
So, it looks like the rig wasn't tensioned as part of the commissioning process. It seems that turnbuckles may not have been locked as vibration or "resonance" may have made the rig more loose "in addition".
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26-10-2017, 15:46
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#53
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Marine Service Provider
Join Date: Dec 2006
Location: Brisbane Australia
Boat: Multihulls - cats and Tris
Posts: 4,886
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Re: Lagoon 42 loses mast
Given the amount of lagoons launched and the relative rarity of issues like this - it certainly doesnt sound like a design or build issue rather a reminder to keep an eye on rig tune, on any boat
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26-10-2017, 16:07
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#54
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Registered User
Join Date: Sep 2014
Location: On the boat
Boat: LAGOON 400
Posts: 2,373
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Re: Lagoon 42 loses mast
avoiding resonance / shaking seem to be best way by reef or slow down.
resonance can bring down bridges, buildings so it is extremely powerful force that no material can withstand forever.
learned something new here : new criteria when to reef.
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29-10-2017, 00:56
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#55
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Registered User
Join Date: Jan 2011
Posts: 802
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Re: Lagoon 42 loses mast
Quote:
Originally Posted by Factor
Given the amount of lagoons launched and the relative rarity of issues like this - it certainly doesnt sound like a design or build issue rather a reminder to keep an eye on rig tune, on any boat
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Well said, I believe that is twice in a year I have agreed with you, but I may just be getting old and forgetful.
__________________
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29-10-2017, 03:26
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#56
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Registered User
Join Date: Aug 2017
Boat: Lagoon 400S2
Posts: 3,755
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Re: Lagoon 42 loses mast
The 42 is a new construction, they moved the mast aft and the compression pole is located at the entrance of the salon.
It could be, that the deck at this point is dynamically not that stiff / rigid than the construction of the good old lagoons, the deck and the roof are not very strongly interconnected because of the large opening between cockpit and salon. The structure on the old design was stiffer, having the glass front as enforcement for the structure / support for the mast and the compression pole. The aft position can cause dynamic deformations between top and lower deck being interconnected only by the compression pole and 2.5 meter side-wise by the salon walls. Also the main sheet traveler at the aft of the upper deck adds some dynamic load and is transferred through the poles to the structure of the hulls. If the rig is not under tension and the mast base is not high enough, it could lead to this incident.
I am curious, if other new lagoons have the same issue, they all have this "new" design, where the mast was moved aft and is standing alone on the compression post in the mid of the salon/cockpit on the weakest point of the deck structure with long levers in all directions.
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29-10-2017, 23:16
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#57
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Registered User
Join Date: Sep 2014
Location: On the boat
Boat: LAGOON 400
Posts: 2,373
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Re: Lagoon 42 loses mast
I think there is destructive force of structure resonance possible. Like bridge that collapsed due to wind only in US. Resonance produces extreme short term loads that can cause structural damage.
I doubt rigger tensioning rig can adjust properly to avoid resonance issues with single test sail.
Owner should really adjust rig tension if noticing resonance. Alternative is that boat works itself out to let it go in some place so that resonance disappears by itself (if lucky without damage) . Noticing resonance during sail is critical issue to get rid of it asap, before damage occurs.
Wonder how many masts was lost due to resonance. Would imagine monohull going windward can produce some serious resonance as well - mast/keel shaking.
there is more to the boat/rig than I thought up until recently.
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30-10-2017, 01:07
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#58
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Registered User
Join Date: Mar 2007
Location: Santa Cruz
Boat: SAnta Cruz 27
Posts: 7,213
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Re: Lagoon 42 loses mast
Quote:
Originally Posted by Factor
Given the amount of lagoons launched and the relative rarity of issues like this - it certainly doesnt sound like a design or build issue rather a reminder to keep an eye on rig tune, on any boat
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Given that the L42 is a different design than most previous Lagoons, the jury is still out. The problem could be (1) poor rig tension, (2) a mast step lower than previous versions, (3), the new configuration with the mast and shrouds further aft and a free standing compression post, or (4) a combination of all three.
If I was a L42 owner, I'd immediately check rig tension, and work on a redesigned mast step which captures more of the mast.
The owner says the mast jumped out of the step, but I'm mystified as to how it could disappear into the ocean without putting large divots in the fiberglass around the step. It appears that there are turning blocks on deck for the halyards and mainsheet, which would not only put hundreds of pounds of downforce on the base, but would also limit how far the base could travel if it did jump the step.
Comparing the L42 to the L400, I note that the shrouds are attached much further back on the hulls. If the structure of the boat starts to twist in larger seas I can see that the L42 would be more prone to having the shrouds go slack than the L400, and perhaps create the observed 'resonances'.
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30-10-2017, 02:10
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#59
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Registered User
Join Date: Aug 2017
Boat: Lagoon 400S2
Posts: 3,755
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Re: Lagoon 42 loses mast
 The longer the lever, the lower the resonance frequency and the higher the amplitude of the waves.
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30-10-2017, 13:31
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#60
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Registered User
Join Date: Feb 2016
Location: Afloat - Mediteranean
Boat: Lagoon 450 F
Posts: 387
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Re: Lagoon 42 loses mast
Quote:
Originally Posted by SV DestinyAscen
Video makes it clear owner has a habit of flying the parasailor only without the main - someone can correct me but I recall certain cat manufacturers precisely recommending against such practices because of a lack of backstays. I'd bet a drink the mainsail was down, mainsheet and topping lift loose.
Rig might have just been a little loose without being retensioned after expected stretch - voila rig gets lifted forward and comes down.
Prob a good thing the mast isn't pinned - pins won't save the rig from coming down and will definitely breach the hull and give you problems in rough seas.
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I would imagine, when flying a kite with no main up, you keep tension on rig by Tightening up on Topping Lift + Main sheet, effectively acting as a backstay ?
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