Preventer Rigging -- Lessons from the Platino Disaster

[jmh2002]

Originally Posted by MartinR

Yes, of course, for racing this is obviously a big advantage. But I doubt you would get any noticeable increase of speed on a cruising boat. The energy wasted in rope stretch is extremely low. But, yes, the foil profile is better maintained with Dyneema. For racing, 0.1% in speed gain means a world, for cruising basically nothing. Also, most cruising boats fittings are not designed to take the shock loads from Dyneema. Racing boats are. Needs thinking about.

Yes, I agree, it always needs thinking about.

But on the other hand I have also never really understood this idea of 'oh it's a cruising boat it doesn't need to go fast'. Cruising compromises, yes ok, but going slow for no good reason, I don't get (conditions dependant of course).

This is how we arrive at these fat, overloaded, and slow boats - Island Packet, with a huge arch, bimini, jerry cans on both rails, tender on davits, roller furling piece of washing line and laundry for a headsail, etc

And then these are same owners say catamarans don't sail upwind...

Also I think the difference is more than such a small percentage when taken as an overall concept, ie: the whole boat modernised. In a cruising context this could be the difference between being able to beat off a lee shore, or not...

NB: I understand that is probably not you, with a 70ft ULBD for 'cruising' - that is my kind of style too

[Dockhead]

Originally Posted by MartinR

Yes, of course, for racing this is obviously a big advantage. But I doubt you would get any noticeable increase of speed on a cruising boat. The energy wasted in rope stretch is extremely low. But, yes, the foil profile is better maintained with Dyneema. For racing, 0.1% in speed gain means a world, for cruising basically nothing. Also, most cruising boats fittings are not designed to take the shock loads from Dyneema. Racing boats are. Needs thinking about.

It's not so much a question of speed, as responsiveness and control. Polyester sheets just feel mushy compared to dyneema. You can't precisely control the shape of the sail, because the sheets stretch and let the sail shape change and bulge out under load. This is especially bad sailing in strong wind and hard on the wind, when stretch in a puff will defeat your flattening and streamlining of the sail and give you precisely the opposite of the shape you want, and just at the wrong time. With laminate sails and dyneema sheets (and outhaul), you can sail in maybe a whole wind force more without reefing, because you can precisely flatten the sail and feather it a bit when you need to.


YMMV, but I personally will never go back to either woven sails or poly running rigging. For me, laminate and dyneema just totally revolutionized sailing and made it vastly more fun and interesting. That it's also much faster is just a bonus.

[jmh2002]

Edited my post, sorry for the delay.

[Kenomac]

Originally Posted by Dockhead

It's not so much a question of speed, as responsiveness and control. Polyester sheets just feel mushy compared to dyneema. You can't precisely control the shape of the sail, because the sheets stretch and let the sail shape change and bulge out under load. This is especially bad sailing in strong wind and hard on the wind, when stretch in a puff will defeat your flattening and streamlining of the sail and give you precisely the opposite of the shape you want, and just at the wrong time. With laminate sails and dyneema sheets (and outhaul), you can sail in maybe a whole wind force more without reefing, because you can precisely flatten the sail and feather it a bit when you need to.


YMMV, but I personally will never go back to either woven sails or poly running rigging. For me, laminate and dyneema just totally revolutionized sailing and made it vastly more fun and interesting. That it's also much faster is just a bonus.

We have Dyneema and Spectra laminate tri radial sails, if I added dyneema sheets it wouldn’t make a bit of difference timewise on my getting from point “A” to point “B.” But it would place an extra shock load on components not designed to take the load... so I’ve chosen instead to keep the boat stock, just as the engineers designed it to be.

[Dockhead]

Originally Posted by jmh2002

Yes, I agree, it always needs thinking about.

But on the other hand I have also never really understood this idea of 'oh it's a cruising boat it doesn't need to go fast'. Cruising compromises, yes ok, but going slow for no good reason, I don't get (conditions dependant of course).

This is how we arrive at these fat, overloaded, and slow boats - Island Packet, with a huge arch, bimini, jerry cans on both rails, tender on davits, roller furling piece of washing line and laundry for a headsail, etc

And then these are same owners say catamarans don't sail upwind...

Also I think the difference is more than such a small percentage when taken as an overall concept, ie: the whole boat modernised. In a cruising context this could be the difference between being able to beat off a lee shore, or not...

Amen. Or sail out from under a weather system. Or or or. And as someone said in another thread, in reference to some performance cat -- a faster boat has a wider RANGE of speed -- you have more choices about reducing sail increasing comfort and safety and still making a decent pace.



To each his own, but a decent turn of speed makes sailing SO much more fun, and gives you so many more options.

[jmh2002]

Yeah, I did a lot of miles on a Swan 51 way back when. When the boat was purchased it still had all wire to rope spinnaker guys! And halyards of course, and runners, and, and... Damn!

Well, on deck we pretty much changed everything, going down to I think 8 winches instead of 30 (ok, joking, but there were a lot of winches), all harken ball bearing deck gear, mast stripped and lightened plus harken sheaves, carbon pole, all high tech lines of much smaller diameter, kevlar sails, etc, etc. You get the point.

The boat was much lighter, much faster, and much more easy to sail (faster or slower as desired). I often single handed the boat around the Caribbean because it was so easy to sail. Really. Much easier than the average fat cruising boat of the day.

In full cruising mode, loaded with a bilge full of rum and months of provisions, but sporting a big roach full batten cruising mainsail (somehow radical at the time), all this modern gear, and 3m of deep draft fin keel courtesy of German Frers, she went up wind like a train, running rings around the generic Beneteau charter boat back then.

We were never worried about a lee shore and sometimes sailed out on the windward side of the islands and reefs on purpose, because, it was nice out there, and well because we could.

This was around 25 years ago. So I can't understand why anybody would not have ONLY high tech lines on their boat these days.

For cruising the benefits are endless.

[waterman46]

Originally Posted by accomplice

Yes!

Our standard practice is to drop the main sheet further than the point of sail calls for, even if it puts the sail against the spreaders, then secure the preventer, then tighten the main sheet such that the preventer is in significant tension. If the boom were allowed any movement from a backwinded sail, the situation could get dangerous fast.

Yes, SOP on my boat. We also use a double loop of heavy line around the boom positioned about 2/3 of its length from mast, as a point to clip on the very heavy (9/16 or 16mm I guess) preventer which is tightened with a 4 part inline 9/16 block and tackle, the other end of which is clipped into a 3/4" line tied into the "midships" mooring cleat which is located at toerail about even with the mainmast. Using the double wrap of line around the boom rather than a hardware bail, greatly lessens the twisting force on the boom that could be exerted by the preventer.

All of this combined with fact that boom is short and we don't have all extra weight involved with in-boom reefing, makes me confident we could survive a similar occurrence.

But I still wonder why it did not seem to occur to the crew, that they could have stabilized that boom instantly by either releasing the topping lift and/or rigid vang, as case may be, to dump aft end of boom on deck whete iy could be easily tied down.

[Dockhead]

You're wasting your money on laminate sails, if you control them with polyester sheets. The mush in the sheets defeats the shape-holding quality of laminate sails. It's not about speed (not primarily), it's about control.

Originally Posted by Kenomac

We have Dyneema and Spectra laminate tri radial sails, if I added dyneema sheets it wouldn’t make a bit of difference timewise on my getting from point “A” to point “B.” But it would place an extra shock load on components not designed to take the load... so I’ve chosen instead to keep the boat stock, just as the engineers designed it to be.

[Kenomac]

Originally Posted by Dockhead

You're wasting your money on laminate sails, if you control them with polyester sheets. The mush in the sheets defeats the shape-holding quality of laminate sails. It's not about speed (not primarily), it's about control.

Nope. It’s all about longevity, reliability and the sails retaining their shape over 10 years and 30,000 miles. We’re not trying to be a racing boat.

BTW... ours came with Sailcote for protection and to help slide nicely into the slot, did you end up applying Sailcote to yours?

[fxykty]

Originally Posted by Dockhead

Amen. Or sail out from under a weather system. Or or or. And as someone said in another thread, in reference to some performance cat -- a faster boat has a wider RANGE of speed -- you have more choices about reducing sail increasing comfort and safety and still making a decent pace.



To each his own, but a decent turn of speed makes sailing SO much more fun, and gives you so many more options.

Agree about the speed. But not sure about attributing all that extra speed just to low-stretch sheets. 1% of extra speed matters to a racer, but surely does not matter to a cruiser. That 1% does not make the difference between a slow boat vs a fast boat. And are the sheets really worth 1% extra speed?

Let’s compare:
- Italian 14mm pre-stretched double braid polyester line. Stretch at 30% of break load is 5.5%.
- NZ-made 10mm UHMWPE braid with polyester cover has stretch at 30% break load of 2.6%.

So half of not much. For a 10m sheet that’s 29cm of extra stretch. Is that enough to change your sailing from mushy to fun, from slow and sluggish to speedy?

[fxykty]

Though I totally agree changing to low stretch/ high strength lines to reduce line diameters, reduce windage, and (sometimes) improve handling. Similar motivations as changing out blocks for low friction rings and hard shackles for soft shackles. Where it makes sense.

[Dockhead]

Originally Posted by Kenomac

. . . BTW... ours came with Sailcote for protection and to help slide nicely into the slot, did you end up applying Sailcote to yours?

Yes, the SailKote works really well. During this coming winter I will have the sails laundered and refurbished and professionally coated with the stuff. A "must" for in-mast furling, I think.

[jmh2002]

Originally Posted by fxykty

So half of not much. For a 10m sheet that’s 29cm of extra stretch. Is that enough to change your sailing from mushy to fun, from slow and sluggish to speedy?

29cm of stretch? That's huge. Imagine easing the sheet almost a foot each time a gust comes on...

And the point really is that, just like sail stretch, line stretch is not only not converting wind to power, it is also constantly changing the sail to a non optimal shape.

I don't have any reference facts at hand but the 1% or 0.1% was just hypothetical I think. I expect that the overall effect is quite a bit more, and over a passage that will add up significantly.

[Dockhead]

Originally Posted by fxykty

Agree about the speed. But not sure about attributing all that extra speed just to low-stretch sheets. 1% of extra speed matters to a racer, but surely does not matter to a cruiser. That 1% does not make the difference between a slow boat vs a fast boat. And are the sheets really worth 1% extra speed?

Let’s compare:
- Italian 14mm pre-stretched double braid polyester line. Stretch at 30% of break load is 5.5%.
- NZ-made 10mm UHMWPE braid with polyester cover has stretch at 30% break load of 2.6%.

So half of not much. For a 10m sheet that’s 29cm of extra stretch. Is that enough to change your sailing from mushy to fun, from slow and sluggish to speedy?

Halving the stretch is huge. Yes, that can be mush to fun. But in my case much more than that, because I didn't go down in size so aggressively. I went from 16mm poly to 14mm racing dyneema with considerably higher breaking load than the 16mm poly. From memory, the stretch is something like 5 times less at the same load in tonnes (not % of breaking). The difference is truly night and day.



And one more time -- it's not primarily about speed. It's about precise control over the shape of the sail. It's about the sail staying in the shape you chose, even in the puffs. It's about the sail not bellying out into a draggy shape when the wind blast comes.



You do get more speed, but that's a bonus for us cruisers and not the main point.

[Dockhead]

Originally Posted by jmh2002

29cm of stretch? That's huge. Imagine easing the sheet almost a foot each time a gust comes on...

And the point really is that, just like sail stretch, line stretch is not only not converting wind to power, it is also constantly changing the sail to a non optimal shape.

Exactly. It amounts to more or less the same thing as sail stretch.


Polyester sheets belong in the same trash can where you left your old Dacron sails.


I actually tested this in real life for a few thousand miles of sailing. A couple of years ago, I stupidly chafed one of my dyneema sheets and had to put back one of the old poly ones. So I had a 16mm poly sheet on the starboard side, and a 14mm dyneema one on the port side. Wow! Night and day! Like a different boat sailing on starboard tack compared to port tack.