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Is a boom vang on an unstayed mast a bad idea?


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I know the Nonsuch uses a system like that, but I'm talking about a dinghy-sized boat with a 20', 2-piece, unstayed, aluminum mast that wasn't designed with a vang in the plans.  There's no headsail, so no forestay to help offset the pressure, though one may be added in the future.  

I'm unclear just how much force is put on the vang on your typical dinghy when sailing downwind, but the multiple blocks in the system would suggest, to me anyway, that it could be quite a bit.  For this reason, I'm concerned that I'll bend the mast if I tie the boom down and put all the force into the mast, that would normally be relieved by letting the boom lift.  

This is Max.  Max is 82 years young and has been sailing his, heavily modified, WR16 for 15 years.  The jib is not stock.  Nor is the vang, but he seems to make it work.  

Your thoughts?   :unsure:

 

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4 hours ago, JohnMB said:

Bending the mast is one of the benefits of a vang on this type of mast, just don't overdo it :),

 

Bending it back as opposed to allowing the top to fall away to leeward and close up the leech could be a win.

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On a laser you can bend the mast or pull the boom into two pieces. Look at a set up on a laser: lots of purchase! The problems occur, typically, when you leave all the upwind vang tension on when going downwind in a breeze (sidenote: it is not fast, but more stable). 

In any case, if used with some moderation it should be totally fine, and I would recommend it.

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Winston,

You can fit a boom vang to most rigs without too much trouble you just need to make shore you don't put to much tension on it if the mast or boom isn't sleeved. 

 

If you are worried about bending the mast or boom just make shore you only use a vang system that is only a 3:1 or 5:1 system 

 

Pulpit

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Vang is usually not super tight going downwind, should be just enough to keep the boom from rising. It also is a bit of a backstay holding the mast from bending forward, between the sheet and the vang they keep the mast in column down wind, otherwise the mast can actually bend forward and break that way.  Upwind it takes the load off the mainsheet a bit and can be used to induce mast bend just don't overdo it if your mast isn't designed for it.

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45 minutes ago, ROADKILL666 said:

But the mast rotate 

Not sure what your point is. Laser and Finn rotate. I don't believe opti masts rotate, and I have no idea about the Topper but regardless: if a mast does not rotate, you just need to let off a bit more vang. This is true for most keelboats as well.

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7 hours ago, AnotherSailor said:

On a laser you can bend the mast or pull the boom into two pieces. Look at a set up on a laser: lots of purchase! The problems occur, typically, when you leave all the upwind vang tension on when going downwind in a breeze (sidenote: it is not fast, but more stable). 

In any case, if used with some moderation it should be totally fine, and I would recommend it.

Laser with Vang off sailing by the lee is far more stable than DDW or broad reach with boned on vang.

Sourch: am laser sailer.

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On reasonably small boats it isn't - see posts above.

On bigger boats, an unstayed mast is a bad idea. *

 

 

 

 

 

*) I know I will get flamed for this by the usual suspects, but somebody just has to tell the truth!

 

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If you want to keep it really simple, just fit a single span of 3/16" spectra as a non-adjustable vang.  Adjust the length with a light spectra lashing one end so it's slack on the wind, and just the right length to stop the boom rising too far off the wind.  Don't forget a simple D-shackle one end so you can disconnect it to pack the boat up.

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3 hours ago, P_Wop said:

If you want to keep it really simple, just fit a single span of 3/16" spectra as a non-adjustable vang. 

I wondered about that.  Thanks for the input!  B)

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Vang is an indispensible piece of kit. That the old timers didnt use one shows that they were astounding seamen. It is veryt much more difficult to keep a boat under control without a vang

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The very first ones were called (and still are in the UK) a "kicking strap", which may explain the usage.  They weren't generally too adjustable, just rigged to stop the boom skying, generally limited to dinghies and small day keelboats. 

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20 hours ago, Looper said:

Laser with Vang off sailing by the lee is far more stable than DDW or broad reach with boned on vang.

Sourch: am laser sailer.

The infamous death roll is instigated when the leech is going fw of the mast, pushing the boat to "windward" (the side where the mast is not - when sailing by the lee this is actually the leeward side). Think about the dynamics here: with the vang off the leech will be loose and DW will be fw off the mast (unless you sheet in, which will not be fast). Yes, sailing by the lee helps, a lot, but it is not far more stable to sail with the vang off, as you suggest. Ainslie writes about this in his laser campaign book: the looser the vang, the faster you sail, and the closer you are to the death roll. It is a fine line between sailing fast and wiping out. 

And I am not talking about just a few knots of breeze here...

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On 10/5/2021 at 2:16 AM, AnotherSailor said:

On a laser you can bend the mast or pull the boom into two pieces. Look at a set up on a laser: lots of purchase! The problems occur, typically, when you leave all the upwind vang tension on when going downwind in a breeze (sidenote: it is not fast, but more stable). 

In any case, if used with some moderation it should be totally fine, and I would recommend it.

Not dumping the upwind vang when you go downwind is a problem on a lot of boats, not just those with an unstayed rig. Almost anything with a powerful vang can snap its own mast or boom this way. Seen it happen on E-scows a few times.

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11 minutes ago, JM1366 said:

Not dumping the upwind vang when you go downwind is a problem on a lot of boats, not just those with an unstayed rig. Almost anything with a powerful vang can snap its own mast or boom this way. Seen it happen on E-scows a few times.

I would posit it is worse on nonrotators. The section modulus is much less transversely on stayed masts.

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Modifying my earlier response, you don't need spectra.  A length of ¼" dacron 8-plait (the core of a halyard from your local rigging shop), with a simple tucked eye splice at the lower end to take the light lashing should be fine.  Since it's a loose footed sail, do a 3 turn back and forth wrap round the boom, and hitch the end after the 3 reverse wraps back to its standing part.  The only fitting you need is tiny dinghy eyestrap screwed or riveted into the top of the boom at the aft end to stop the lashing sliding forward.  You can do it all for $25, including the beer for the rigger.

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1 hour ago, fastyacht said:

I would posit it is worse on nonrotators. The section modulus is much less transversely on stayed masts.

Quite a bit worse in some cases where the mast extrusion is designed to be as aerodynamic as possible.

It's also really common to break booms when people don't release the vang at the windward mark, especially on boats with a noodle boom and an oversize mast (Flying Scot comes to mind).

 Bigger scows (E, A) have a rigid vang that is incredibly powerful, and it's perfectly capable of breaking both a spar and your wallet. 

 

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Vang sheeting is perhaps the most important skill to learn as a dinghy sailor. Elvstrom is given credit for inventing the kicking strap.

Laser sailing down wind with the vang on is sketchy because the boom is long and it's easy to catch the tip of boom in the water and suddenly you are swimming. Letting the vang off downwind accomplishes a ton of stuff. It makes the sail fuller, the rig goes vertical or even forwards, the leach is allowed to move freely.

Sailing by the lee is inherently less stable. If done properly and deep enough the wind is flowing in the reverse direction. In order to make that happen you are sailing as close to limbo(moment of gybe) as possible. How could that possibly be more stable than going downwind? Here's a neat trick for you Laser guys. Watch your windex when sailing by the lee. If it starts spinning you are right on the edge of gybing. You have a second to head up a bit before you go for a swim. 

He may be confusing sailing by the lee and simply heeling the boat to windward, which is supposed to change the center of effort to some benefit.

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  • 1 month later...

I can't swear that it's making a difference, but I can definitely see that it's taking up some tension.  

Maybe I'll notice it more when sailing downwind in faster conditions.  There wasn't a ton of wind out there on Tuesday.  

 

One day I'll learn to edit the ending of my videos so they're a bit smoother.  

 

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