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Kicker load on an Ent

Printed From: Yachts and Yachting Online
Category: General
Forum Name: Repair & maintenance
Forum Discription: Questions & tips on the subject
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=13299
Printed Date: 15 Oct 19 at 6:26pm
Software Version: Web Wiz Forums 9.665y - http://www.webwizforums.com


Topic: Kicker load on an Ent
Posted By: Eisvogel
Subject: Kicker load on an Ent
Date Posted: 28 Mar 19 at 11:09am
I want to attach the kicker on my Ent to the boom with a snap shackle, so I can take it off easily during launching, as it fouls the centreboard and has already sheared it off twice (don't ask).

What is the maximum load that the shackle should be able to withstand? The one I'm looking at currently comes in three sizes, with loads of between 1000kg to 3000kg.

I'd never thought of it in that way, but I assume that there can potentially be quite a lot of pressure, and I wouldn't want the shackle to break just at the wrong moment. Would the 1000kg one be big enough?


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Enterprise 20361 (Eisvogel), Laser 102727 (Halcyon), Laser 121986



Replies:
Posted By: Sam.Spoons
Date Posted: 28 Mar 19 at 11:23am
What is the purchase on the kicker? If it's 8:1, you can probably pull 100kg so that's approaching 800kg after friction losses. The 1000kg one will probably be rated as SWL so actual max load will be at least double. I think that might get exceeded in a high wind gybe so I'd be inclined to go for the 2000kg one.

However, I don't recall either of my Ents kickers fouling the CB head? Fittings are pretty strictly controlled in the Ent so are the kicker attachments in the correct places?

Also it will be easy enough to reattach the kicker when the wind is light/moderate but in a blow it might be difficult on the water so a kicker that can be attached before launching might be a better choice if it can done.


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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"


Posted By: ttc546
Date Posted: 28 Mar 19 at 11:39am
Hmmmm...I can see some smacked heads while launching in a breeze with the boom flailing around with no kicker to keep it vaguely under control.....

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Chris


Posted By: Rupert
Date Posted: 28 Mar 19 at 11:40am
The shock loads can be far higher than you can pull. However, I'd think a couple of tonnes would be plenty.

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Firefly 2324, Lightning 130, Puffin 229, Minisail 3446


Posted By: Eisvogel
Date Posted: 28 Mar 19 at 1:11pm
I think the kicker is 16:1, so pulling 60kg would get me almost to 1000kg if I worked that out correctly.

The grip at the front of the centreboard is just in the wrong place for the kicker; it's fine once the board is down even a little bit. I had problems on the shore with the boat still on the trolley with the wind gusting and shifty; the boom moved across, kicker got stuck on the handle, and off broke the top part (the bit that was out of the case at the top).

Rupert: so you think the 2000kg should suffice?


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Enterprise 20361 (Eisvogel), Laser 102727 (Halcyon), Laser 121986


Posted By: Sam.Spoons
Date Posted: 28 Mar 19 at 2:07pm
The weakest point in an older Ent kicker system is probably the lower fixing. Not sure how your's is fixed but mine were both screwed into the hog (early wooden boats, I can't remember but I imagine the kicker was no more than 4:1 TBH).

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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"


Posted By: Granite
Date Posted: 28 Mar 19 at 2:16pm
I think that 1000kg will be more than enough. Sure there is a lot of purchase, but do you think you could feasibly lift 60kg, equivalent to a small adult with one hand using 4mm control line? Also think about the strength of other components in the system. Look at the final line strength, or final block type they will give you a good steer for strength of the system.




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If it doesn't break it's too heavy; if it does it wasn't built right


Posted By: ChrisJ
Date Posted: 01 Apr 19 at 1:06pm
Enterprise 20361: When new, that had the lower kicker attachment as a U-bolt, bolted through the hull, with a backing plate underneath. It would take a lot of rotten wood and close to a complete boat failure for that to pull out! 

And if the boom is still the original, then the fitting on the boom could easily be in the wrong place. When new, it had a complex highfield lever system on the boom for the top of the kicker, to allow a coarse as well as a fine adjustment on the kicker lever. I suspect this was all replaced with a proper cascade system years ago!


Posted By: Rupert
Date Posted: 01 Apr 19 at 3:36pm
I've bent 1 tonne ones before,(they distort enough that they no longer meet) but never a 2 tonne one, and the pressures cannot be that different between Ents and Minisails in the great scheme of things. My other boats have always used either closed shackles or keys.

Moving the boom take off point forward would reduce leverage, but mostly take out the forward component. It would create more crew room, too. But the big draw back it it shortens the length of travel for the last purchase. Do Ents have strict rules on the length of handle the centreboard needs?

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Firefly 2324, Lightning 130, Puffin 229, Minisail 3446


Posted By: Sam.Spoons
Date Posted: 01 Apr 19 at 5:09pm
Originally posted by Granite

I think that 1000kg will be more than enough. Sure there is a lot of purchase, but do you think you could feasibly lift 60kg, equivalent to a small adult with one hand using 4mm control line? Also think about the strength of other components in the system. Look at the final line strength, or final block type they will give you a good steer for strength of the system.



Good point about the block types, they will indeed be the weakest link (most likely) but I reckon I could pull 60 kg onto my kicker line so, with a 16:1 cascade 960kg less friction losses (which will be a fair percentage) but it's the additional shock loads in a windy gybe that will be the issue and they could easily be double or triple the static load.


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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"


Posted By: Eisvogel
Date Posted: 01 Apr 19 at 7:09pm
Originally posted by ChrisJ

And if the boom is still the original, then the fitting on the boom could easily be in the wrong place. When new, it had a complex highfield lever system on the boom for the top of the kicker, to allow a coarse as well as a fine adjustment on the kicker lever. I suspect this was all replaced with a proper cascade system years ago!

Not sure if the boom is original; it could well be. And yes, it has a cascade kicker which is attached to the floor.

My problem is that the kicker is already maxxed out before I get the right setting for stronger winds, so ideally I need to move the attachment point on the boom further back (obvs in line with class rules), but that makes it even worse with the centreboard interference.

I think the consensus here is that the 1000kg ought to be enough, but might be borderline; and the 2000kg would be a safe bet. Thank you for all the useful comments!


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Enterprise 20361 (Eisvogel), Laser 102727 (Halcyon), Laser 121986


Posted By: Sam.Spoons
Date Posted: 01 Apr 19 at 11:48pm
It shouldn't be too difficult to have a coarse and fine adjustment with a cascade kicker, take up the slack with the coarse and use the fine for power?

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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"


Posted By: Neptune
Date Posted: 02 Apr 19 at 12:37am
I think some people here should go to the gym and recalibrate how strong they think they are... 

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RS300, ex Musto Skiff


Posted By: Sam.Spoons
Date Posted: 02 Apr 19 at 9:11am
I'm getting older but I do have a pretty good idea how strong I am (a couple of different jobs and hobbies over the years). 60kg I can lift and pull on a line in a favourable position. I could not pull that much from the side deck but we have to take into account the max loads when speccing rigging. Good quality snap shackles will have a SF of 3 but cheaper Chinese stuff likely no more than SF = 2. The shock loads possible on a kicker are likely to be at least 2 x static load so a strong crew setting up the kicker while leaving the beach and a strong wind gybe will probably exceed the breaking load of a 1000 kg rated shackle. 99 times out of 100 the l tonne shackle will be fine, the OP wanted to know what to use for maximum confidence. 

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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"


Posted By: PeterG
Date Posted: 02 Apr 19 at 10:50am
I once got caught under the boom of my Contender and tried straightening up a little and snapped the 4mm dyneema, which made getting out a lot easier. OK, it snapped at a knot, so effective bs probably only around 1000kg, but it taught me a thing or two about the loads that can be generated by an 18:1 kicker.

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Peter
Ex Cont 707
Laser 189635
DY 59



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