Can newbies really be that thick

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Daydream believer

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In practice no boat is perfectly symmetrical.
You say that; but modern mass production techniques are so good & the fit of internal parts is so clever, that it suggests that, (when new) a modern yacht is extremely accurate. I certainly hear stories of people amazed when they visit their vessels in production, how well parts fit. I know of a Stephen Jones one off, where the deck was made in one factory & the hull in another. The owner went to see the 2 parts matched together. He says the 2 parts were millimeter perfect & needed no adjustment whatsoever. I doubt that the robotics used by the big manufacturers would work if the boats were not built accurately.
 

Fr J Hackett

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You say that; but modern mass production techniques are so good & the fit of internal parts is so clever, that it suggests that, (when new) a modern yacht is extremely accurate. I certainly hear stories of people amazed when they visit their vessels in production, how well parts fit. I know of a Stephen Jones one off, where the deck was made in one factory & the hull in another. The owner went to see the 2 parts matched together. He says the 2 parts were millimeter perfect & needed no adjustment whatsoever. I doubt that the robotics used by the big manufacturers would work if the boats were not built accurately.
You have more faith in hand laid up GRP components than I Gunga Din
 

Daydream believer

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Halyard or tape…..

Stretch in the halyard? Innaccuracy on where exactly you are measuring to, etc. A measure is best, that’s all. We’d ideally like to be within 2mm, certainly within 5
So how do you attach the tape & to what? Surely the halyard coming from the wheel at the top of the mast is a fixed point & is better than a tape tied on to it. Does a linen tape stretch? Yes it does. More than a dynema haylard halyard I suspect. It just needs sense on what tension one applies to the measuring medium.
One does not need to know the length. One only needs to know that it is equal. We are talking about vertical alignment port to stbd. Not rake fore & aft.
 

Chiara’s slave

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Steel tapes still stretch, just not much. Getting the stays equal is what it’s about, indeed. Rake is variable on the fly for us and every other XOD. Steel tape pulled hard against the main halyard wheel is how you do it. It’s just the law of 0.5%. Just cos the hull might or might not be a bit off, no reason not to do your best with what you can control.
 

Mark-1

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Steel tapes still stretch, just not much. Getting the stays equal is what it’s about, indeed. Rake is variable on the fly for us and every other XOD. Steel tape pulled hard against the main halyard wheel is how you do it. It’s just the law of 0.5%.

We’d ideally like to be within 2mm, certainly within 5

I'm jealous. With 40cm shrouds you should be able to store your mast over winter in a cupboard.
 

MisterBaxter

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How far off centre would a mast need to be to make a measurable difference to sailing speed? And how would that difference be caused?
 

flaming

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How far off centre would a mast need to be to make a measurable difference to sailing speed? And how would that difference be caused?
That's going to depend on if the mast is just leaning, but is still straight in section, or if the lowers are holding the middle straight but the top is off to one side, or if the top is central, but the lowers are off so it's a bit like a banana.

If it's just leaning then you probably don't need a huge amount off to make a noticeable difference. Principally because the mast is a very long lever, and if it's off centre then it will be heeling the boat. Thus on one tack you'll be slightly stiffer than the other. As even when heeled the mast top will be either further from the centreline, or closer to it, so changing the heeling moment of the weight of the mast. In one of the cups in the IACC boats one of the challengers spent huge amounts of money trying to design a system that used the flex in the keel to pull the windward shroud and thus cant the mast to windward on each tack. They were talking about tiny amounts but clearly thought it was worth it until someone got wind of it and it was ruled illegal.

If the lowers are ok but the caps are off, then a similar thing, but a bit less marked as the range of movement would be slightly smaller. You'd also have some sail trim issues to deal with. If the caps are just loose on both sides so the mast head sags to leeward on either side then you're just giving up performance.

If the mast is a banana then you will have sail trim issues. And eventually probably defying gravity issues.
 

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And you are wrong about threads having to be located equally in the barrels. The threads are adjusted to make the mast sit vertically in (or on) the boat. It may be a matter of parts of a millimetre more on one side or the other, but I have yet to come across standing rigging which is perfectly symmetrical. I suggest your assumption is facile.

My stays are unequal ... not my fault ... but true. So the bottle screws are not equal threads each side. But I use the lock nuts as indicator of quick setting of stays when tensioned.
 

Refueler

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Hoist a plumbline up a halyard?

The best way and means even a boat that is not exactly level this can be used :

Take spinnaker halyard (preferred as it usually clears forestay etc) ... now slack it down till the end in your hand touches chainplate one side .. make off ..

Now take halyard to other side and see if it touches that chainplate same .. The difference is the mast leaning to one side.

Plumblines are great - IF boat is actually truly level.
 

Refueler

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I sailed a whole season with the shrouds not held captive in the spreader ends.
I didn't find out till the mast was unstepped by the yard .
Ultimately my fault for not checking.

My SR25 has shrouds free running through spreader ends ... not all boats have captive shrouds to spreaders ... many like mine - the shrouds pass through eye at spreader ends.

My Conq38 has them 'captive' but also spreaders set by their own short stays to mast.
 

flaming

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The best way and means even a boat that is not exactly level this can be used :

Take spinnaker halyard (preferred as it usually clears forestay etc) ... now slack it down till the end in your hand touches chainplate one side .. make off ..

Now take halyard to other side and see if it touches that chainplate same .. The difference is the mast leaning to one side.

Plumblines are great - IF boat is actually truly level.
It's one then the other.... Line the mast up with the boat using the halyard / tape measure to the chainplates trick. Then use a plumb line to see if that's vertical to the waterline. If not, measure chainplates to waterline, and chainplates to mast on both sides to see if that's your issue...

Then at some point you'll find yourself in the boat yard with the boat in the cradle and all sorts of laser levels deployed trying to work out if it's your keel that's 4mm off centre, or if one chainplate has slightly thicker layup under it and is 2mm further from the centre of the boat than the other....
 

Snowgoose-1

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My SR25 has shrouds free running through spreader ends ... not all boats have captive shrouds to spreaders ... many like mine - the shrouds pass through eye at spreader ends.

My Conq38 has them 'captive' but also spreaders set by their own short stays to mast.
Mine were retained in the spreader grooves with rigging wire . Agree that more modern systems are much better now.
 
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