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How a 2:1 halyard works


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sorry boo boo, what did i miss /

I have read all the pages.

The only increase on mast compression that I can see is by added purchase.....how you add that is completely not the point. You can use an electric winch, you can do a five to one on the aft side of the mast......

The loads are how you CHOSE to add them.

A two to one dose not, in any way lessen them.

What have I missed ?

 

A ten to one on the front of the mast makes it way easier, (halyard over a sheave to aft) and lots of rope....but the force is the same.!!!

Its just that the force is on the sail, and therfore a vector between the fore and aft points of that sail.

It is still pulling the mast down. (and sideways).

 

Maybee I am off topic?

But a two to one does not lessen mast compression.

You may have missed that I mostly agree with you ?

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100% spot on MB. its also worth noting that a halyard not holding tension via deck or mast mounted block at the base of the mast removes ALL the compression load normally transferred by the halyard to the mast foot and hull structure. the load instead is taken by the section of the mast between the halyard lock and the sheeve.

 

I think that where people get confused, is that they are thinking about the total load on the mast induced by halyard tension is equal to that halyard tension, when it is actually twice that with a conventional system.

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I'm not talking about halyard layouts anymore, HOWEVER

 

I learned yesterday that North 3DI sails offer greater mast (fwd/aft bend) support than any other sail construction method. Because they have 90° fibres across the sail offering fwd/aft rig support. So your rig will bend slightly less with 3DI

 

Draw us a picture of how that works Josh…… 8)

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I'm not talking about halyard layouts anymore, HOWEVER

 

I learned yesterday that North 3DI sails offer greater mast (fwd/aft bend) support than any other sail construction method. Because they have 90° fibres across the sail offering fwd/aft rig support. So your rig will bend slightly less with 3DI

 

Draw us a picture of how that works Josh…… 8)

 

 

Are ditching Doyals and moving to Norths now WT?

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Not ditching Doyle as such, as for my level of boat they do a really nice job, probably just as good as North.

 

However, the only guy I had dealt with at Doyle now runs a North Sails loft up in Opua. It’s just that this particular guy is magic to deal with and has made a big difference to my sailing over that past 20 yrs.

 

So I tend to follow this sail maker rather than the brand because I know that this particular guy was behind a lot of the good experiences people were having at Doyle. North just saw the value of this guy and did the work to make sure he was on their team.

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I'm not talking about halyard layouts anymore, HOWEVER

 

I learned yesterday that North 3DI sails offer greater mast (fwd/aft bend) support than any other sail construction method. Because they have 90° fibres across the sail offering fwd/aft rig support. So your rig will bend slightly less with 3DI

 

Draw us a picture of how that works Josh…… 8)

 

If I wasn't so busy doing work for you WT I could have shown you that AGES ago.

 

jk

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oh god here we go again.......

Really IB do we have to explain the 2:1 halyard thing yet again or can you just go back a few pages?

 

Boo yes please explain your theory again

 

If you put a set of scales under the mast and throw 1:1 - 2:1 - 20:1 or even 100:1 purchase on a halyard, the load (compression) on that set of scales cannot decrease.

Youre saying that load (weight) read on those scales will get lighter the more purchase you put on the halyard ??? - Maybe the stays are there to hold the whole shootin match from liftimg off

 

Tell me if Im wrong

 

D.

 

PS . San Fran was a blast, a pretty cool city

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actually it does reduce the compression load induced by the halyard. but of course never by more than the halyard tension . of course the real issue is that BC a standard 1:1 halyard puts twice the halyard tension into the mast! motorbikes diagram on the previous page explains it perfectly.... review that if this is difficult to follow. other diagrams further back do the same. :D

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if the halyard is terminated at the masthead, without going around a sheave, then the total mast compression induced by the halyard is equal to the halyard tension. this compression is carried in the mast from the gooseneck to the halyard termination at the masthead.

 

if the halyard goes up and around a sheeve, then the compression is twice the halyard load, unless it is a 2:1 halyard....

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Sorry Booboo, but you and several of you are quite wrong on this. You do not reduce the mast compression no matter how many purchases you have. The Mast compression comes from the tension you have in the luff of the sail plus the weight of the Sail material itself.

Lets say that total load is 100Kg. 1:1 will see 100Kg on the halyard also. But that does NOT Sum to make 200Kg of mast compression. It is 100Kg @ 1:1 = 100Kg on both sides.

2:1 simply makes the Halyard tail "see" 50% of the 100Kg. But the Sail side of the halyard never changes. The sail and the halyard still exerts 100Kg from the top of the mast sheeve to the foot of the sail where ever the point of connection of the bottom of the sail is. eg, the Gooseneck.

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Ever heard of the term "every action has an equal an oposite reaction"?

 

How in gods name does the main pull down 100kg of luff load in a 1:1 halyard without transfering that around the sheave and down the halyard? - you now have two things pulling down - main halyard and main luff.

 

The 2:1 part of the halyard halves the amount of load the main halyard inside the mast puts onto the tube.

 

Maybe because your guys masts have the main halyard inside the rig you forget about that part?

 

All the worlds riggers (me included) and mast designers cant have got it so wrong surely Wheels?

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Ok, now I cannot still get my head around this one.

 

SO, say with have a 2:1 system , all up and tensioned.

No lines are moving.

____________________________________________

Now we have a static system. If we then deleate the blocks and replace them with knots. Same lines, same lengths.........same everything.

This is now static....why is that providing less mast compression ? In affect we just have two bits of string to the top of the mast instead of one.

On the single down side halyard, we can pin that at any point progressivly up the mast, but it only makes a defferance by its streach. If it was a steel rod it would make almost no differance.

 

 

Now dont get me wrong, I understand the whole mechanical advantage thing. I also understand the equal and opposite force thing....

and thats the point.

The more "advantage" you put on one side the greater the force on the other. PLUS friction.

 

__________________________________________

 

I think that this whole thing is screwed up between static, and dynamic loads.

I cannot see for a second, as my "knot tying example hopefully shows how any kind of purchase changes mast compression in a static situation.

___________________________________________

 

As much as my small brain is worth....

I can only see that there is a confusion between dynamic loadings and static loadings.

That once in equalibriam, there cannot be any differance. Otherwise we have invented something for nothing.

SO...once the sail is up, tension has been applied....it dont matter weather you use a 2:1 or a nuclear bomb...the mast compression is the same.

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Simple terms

 

1:1 halyard 100% of the load is compressing the mast

 

2:1 halyard 50% of the load is compressing the mast

 

Ask any mast man which is easier (not faster) and the 2:1 will be the answer

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What ?

did you read what I posted ?

No that is bullocks....

you are just transfering the load to the other side of the mast...not getting rid of it.

You cant get rid of load by putting a block in it....

You decrease the effort, but you dont decrease the static load.

 

I get 2;1

(and a lot more with the serious loads (non marine that I have played with)

*(It decreases effort, but it does not decrease static final load in equilibrium).

hence my whole stupid thing about getting rid of pulleys and changing it to fixed knots......

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wheels you are wrong. think about I again. yes a 1:1 halyard would see 100 kg but that is only if it was fixed at the masthead ie not going around the sheve. just like a halyard lock.......

really guys its a fact honest. simple really.

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