450: Rigging tension cap shrouds and lowers

[ReneJK]

Does anyone know the exact rigging tension for the cap shrouds and lowers ? , they were at 3800kgs and 2600kgs and i am wondering if this is (too) high or correct

[thinwater]

From Seldon Spars:


Sail Delmarva: The Folding Rule Method
Basically, the standing tension on conventional monohull rigs is generally 5% of breaking strength. Then take it sailing in a just-before-reefing breeze and see if the mast is in-column and the lee side not loose, which together are nearly as important as getting the tension right.

[ReneJK]

Originally Posted by thinwater

From Seldon Spars:


Sail Delmarva: The Folding Rule Method
Basically, the standing tension on conventional monohull rigs is generally 5% of breaking strength. Then take it sailing in a just-before-reefing breeze and see if the mast is in-column and the lee side not loose, which together are nearly as important as getting the tension right.

So the breaking strenght of 16mm 1/19 stainless is 18200kg

By that calculation the tension should be around 910kg , seems odd that according to this calculation its 4 times that number ?

[thinwater]

Originally Posted by ReneJK

So the breaking strenght of 16mm 1/19 stainless is 18200kg

By that calculation the tension should be around 910kg , seems odd that according to this calculation its 4 times that number ?

In fact, the Seldon reference said 15%. See the 5th bullet. They quoted stretch per 5%, which is a little confusing.

That makes yours 2730 kg, which is about where you are. Just get the spar straight. The uppers are at 21% BS static, which is too darn high. Someone just kept tightening them!


You don't want the working tension over 20% to get a good working life, and 5% additional load will just make the lee side go to 5%, which enough to prevent it getting slack. So about 15%. Some people go 10%.



https://l-36.com/pt2.php

[ReneJK]

AFter more research on the Selden (mast manufacturer) website they actually recommend 10% of the breaking strenght as tension , for multihulls, for the lagoon 450 the cap shrouds are 16mm and the breaking strenght is 18202kg , this means that the tension should be 1800kg , 3800kg is double the recommended tension !

For 12mm (the lowers) the breaking strenght is 10000kg and the tension should be 1000kg , not 2600 !

http://www.seldenmast.com/files/597-143-E.pdf

[transmitterdan]

It’s also important to understand what is creating the tension. The chain plates are attached to something. Make sure you understand what that is and the loads it can handle. You will sometimes see a decks and bulkheads damaged by blindly tightening shrouds without paying attention to the below deck structural integrity.

[Tin Tin]

How are you measuring the tension?

[arsenelupiga]

tension should be as little as possible but to achieve your goals, say no slack shroud in 20 kn beam reaching with full sails.

Note that this tension is not same for avery lagoon 38 due to tolerances during build.

Definitely would not crank it to 10 % as per instructions but increase tension as rigging settling down.

Actually for lagoon, best you can do get proven french lagoon expert to do it. There is lack of knowledge how these boats operate in anglo speaking community so they may do more damage than good.


oops sorry just realized you talking monohull.

[arsenelupiga]

so, you actually asking for L 450. Here are instructions from real professionals for L 38-410. I bet principle have not changed since, so you croscheck your riggers to ensure no structural damage to your boat. Once damaged, no way back.

[ReneJK]

Originally Posted by arsenelupiga

oops sorry just realized you talking monohull.

I am not talking about a mono ? I am talking about a lagoon 450 that has a rig tension of 3800 & 2600 kgs on the cap shrouds and lower shrouds , which is around 26% of the breaking strenght of the wire currently , and inwas wondering if anyone has the lagoon specs of rigging tension ?

[arsenelupiga]

Originally Posted by ReneJK

I am not talking about a mono ? I am talking about a lagoon 450 that has a rig tension of 3800 & 2600 kgs on the cap shrouds and lower shrouds , which is around 26% of the breaking strenght of the wire currently , and inwas wondering if anyone has the lagoon specs of rigging tension ?

that feels a bit tight. Mine beam reaching with full sails, i can go in 25 kn and no loose shrouds. There is no deterioration of tension after 7.5 years so tension seem okay for mine. Actually i have never seen my shroud loose. Previous boat i had, shroud played in the wind at 15 kn beam reaching. However moment forces were significant when hull pulled back the shroud slack. And there is danger of getting loose. And these top loads destroy rigging. So I am in favour of tighter shrouds.

[fxykty]

Originally Posted by ReneJK

I am not talking about a mono ? I am talking about a lagoon 450 that has a rig tension of 3800 & 2600 kgs on the cap shrouds and lower shrouds , which is around 26% of the breaking strenght of the wire currently , and inwas wondering if anyone has the lagoon specs of rigging tension ?

I’m impressed that you have actual numbers - how were they measured?

In any case, follow the instructions in the earlier attached guide: use a tape measure to capture the current settings in the respective turnbuckles, loosen the cap and lower shrouds until just supporting the mast, then check the prebend. If it’s as it should be then your diamonds are fine. If not, adjust the diamonds until you have the correct prebend. The diamonds also should not be too tight.

Once your prebend is fine, start tightening your cap and lower shrouds. Do a few turns at a time on one side, then the other. Since you can measure the tension, alternately tighten until you’re at 15% of breaking strength for each shroud. Don’t bother with more. If you can’t get there by hand get longer spanners or add some pipe to lengthen them. Otherwise, tighten on the lee side when sailing.

Go sailing with a good offshore breeze so you have flat water. It should be strong enough that you’re fully powered up, sailing close hauled, such that your reefing guide shows that you should reef. The leeward side should be soft but not loose; that is, just a little bit of play in the wire but you can’t turn the turnbuckle by hand. If too loose, tighten to remove most but not all of the looseness, then tack and check/tighten the other side the same amount.

Both sides should be adjusted exactly the same so that the mast stays in column and centred.

Too much tension, even if it doesn’t bend your hulls and cause doors and drawers to stick, is not good for longevity. I’m not sure if it’s worse or better than too loose, but at least too loose is easier to see.

[ReneJK]

Originally Posted by fxykty

I’m impressed that you have actual numbers - how were they measured?

I received a rigging report where these numbers were noted , i assume they used a rigging tension gauge

Originally Posted by fxykty

Go sailing with a good offshore breeze so you have flat water. It should be strong enough that you’re fully powered up, sailing close hauled, such that your reefing guide shows that you should reef

I am sure this is a great and accurate way of setting and tuning the rig , but I assume Lagoon uses some set of numbers as they put on the mast and tune the rig , instead of go sailing with every boat they build

were in the process of buying a boat and there were some issues noted and i am wondering if they are caused by overtensioning the rig (plywood loosening from bulkhead under the mast behind the sofa cusions)

I also find it strange that it seems so hard to find official numbers from the factory for initial installation ?

[meirriba]

Originally Posted by ReneJK

I received a rigging report where these numbers were noted , i assume they used a rigging tension gauge



I am sure this is a great and accurate way of setting and tuning the rig , but I assume Lagoon uses some set of numbers as they put on the mast and tune the rig , instead of go sailing with every boat they build

were in the process of buying a boat and there were some issues noted and i am wondering if they are caused by overtensioning the rig (plywood loosening from bulkhead under the mast behind the sofa cusions)

I also find it strange that it seems so hard to find official numbers from the factory for initial installation ?

My experience is somewhat dated but it may be still relevant according to the posts here.
In 2011, we have received new L400. The manual suggested to tighten shrouds after initial sailing.
I could not get a coherent answer from Lagoon as to the proper tension. After long emails exchange they referred me to the the company that set up the rigging on behalf of Lagoin during boat comissioning. The nice guy there, advised me to do the process by touch and feel, rather similarly to the process described by fxykty (without tension gauge).

[ReneJK]

Just talked to a rigger here in Panama that has a multhull himself , retired now (72 years old) but with 40+ years of experience

When i told him about the tension his face went pale exclaiming ‘that is way too high for a self supporting mast/rig !!’

According to him the cap shrouds and lowers should be between 5 and 10% of breaking strenght , ‘go sailing and the lee should be loose , not slack’ and ‘with that much pressure you are going to bend the boat , its not a mono that needs its mast cranked down to the keel, these are self supported rigs where the shrouds hold up the mast , nothing more , amd certainly not pulls it down onto the deck , put enormous pressure on the mast step or pull the hulls toward the mast’

I guess that 3800kgs (not Lbs !) and 2600kgs (not Lbs!) is too high