Solid boom vang, why is it a bad idea?

[Quandary]

For the last twenty something years all the yachts I have owned have had a vang strut with spring but the current one has a topping lift and a simple 6 to 1 x 2 to 1 kicker tackle. The topping lift is not as much hassle as I anticipated but I would still like to dispose of it. A Selden strut is expensive for a bit of alloy tube with a spring inside it and I have some worries about the long term durability of the much cheaper Barton boomstrut, I can not imagine that permanently bent GRP will not eventually begin to lose its elasticity?
The Sigma 33 I sailed for 9 years back in the 80s came with a solid vang, it was a simple design but we found it both powerful and positive. It comprised a one and a half m. length of strong alloy tube (about 32mm. dia.) from near the mast foot to a 6 wheel car running along a length of X section track below the boom, the car ran back and forward to move the boom up or down controlled by a tackle for down pulling back and a less powerful one for up, pulling forward, both ran down from the boom end to the deck and back to the bank of clutches by the companionway, we had it routed to allow the operator to control it from out on the side deck, but this would not be necessary on a lightly crewed cruising boat where we tend to sit in the cockpit.
It would seem easy to cobble this up from a bit of mainsheet track and car, a suitable tube and the existing tackles for about the same expenditure as a Boomstrut, so why have I never seen it anywhere since?

 

[Daydream believer]

The UFO 34 i sailed in had what was basically a giant bottlescrew with wings to grip the bottle part. Rotated it to adjust the threads in or out and the boom had no play in it whatsoever, just up or down dependent on how much one rotated the outer part.the sail had a large triangle of cloth that could be released on the run and the boom would be lowered right down, decapitating any one in the cockpit. Other than that the flattener was hauled in and the boom raised up.
if we broached the idea of releasing the kicker was never a possibliity as it would have taken ages to wind it out.

 

[patrigo]

I have had in the past, a topping lift with vang, a gas strut with vang, and now I have a Barton Boomstrut with vang. Life is now a whole bunch simpler. I have a boom gallows so the Boomstrut spends a lot of time bent. Does not seem to worry it at all!

 

[PetiteFleur]

I've a Barton Boom Strut on my Moody 33 and it's excellent. One strut did snap after a couple of years but was replaced FOC by Barton - it looked as though it had been poorly manufactured. They sent a pair so now have a spare, but I do make sure to release the strut when not aboard which obviously reduces the stress on it. It's simple, uses the existing kicking strap and easy to fit, and of course raises the boom when released so making reefing a quick and efficient operation.

 

[savageseadog]

I've seen a setup similar to the one the OP's talking about on a SJ36 (Stephen Jones) It's the only one I've ever seen in 30 years.

 

[lw395]

One of my dinghies has a lever-based vang which pushes the boom down.
These things can be made push-pull, as could the old-type lever kickers.
The problem can be limited travel, you may want to let the boom rise a long way in a broach.

 

[Quandary]

No, what I was describing is nothing like the levers which I am familiar with. They have limited movement whereas the movement of the car and thence the boom is only limited by the length of track used, the power is a condition of the angle that the rod makes with the boom and the multiples of the tackle used to shift it. I vaguely recall the maker as IYE? I think the system is a very good one, very powerful, fast to dump and responsive but probably overkill for a Moody S31.

 

[TLouth7]

In dinghies this is normally implemented as a gnav which is above the boom. This offers a couple of advantages - clear space at the base of the mast for the crew, the tackle can pull either forwards or down (depending on which end is free) which is easier to rig, the strut is in compression so can run on the boom (or mast) section itself rather than a track. On a yacht all of these considerations can be mitigated so having it in the conventional place (below the boom) probably makes more sense. Especially as the gnav requires a loose-footed main.

As for why they are not common, I suspect that the hardware is too expensive (though gas struts are not super cheap) and quite complex to fit. For what it's worth, I can't imagine the Barton strut is so badly designed that it creeps appreciably over time.

PS - What about the topping lift is a hassle? I ask because with the solid kicker you would in effect still have a topping lift in the form of the boom-raising tackle. This would still occupy a clutch, and you would still have to remember to release/tighten it like a conventional topping lift.

 

[johnalison]

I have a Selden strut but without the gas thingy, as well as a topping-lift. For me the advantage of the strut is that is ensures that the boom cannot drop onto my sprayhood/screen and cause damage. I have also heard of injury caused by a dropped boom, so I would be loath to do without one, in spite of having sailed for half a century with only a topping-lift.

 

[lw395]

No, what I was describing is nothing like the levers which I am familiar with. They have limited movement whereas the movement of the car and thence the boom is only limited by the length of track used, the power is a condition of the angle that the rod makes with the boom and the multiples of the tackle used to shift it. I vaguely recall the maker as IYE? I think the system is a very good one, very powerful, fast to dump and responsive but probably overkill for a Moody S31.

Yes I know the IYE traveller cars which run on I-beam track. Ithink there's a couple of broken ones in the shed.
They were popular as mainsheet travellers once upon a time.
Even with 6 wheels, I think they fret away at the alloy track over time, then get rough and friction increases.
You could use a recirculating ball traveller I suppose.
The other advantage is that the track reinforces the boom whee most needed.

The car and strut system doesn't in itself have much mechanical advantage.
So you still need a big strong purchase system.
I suppose a car and strut which was only there to support the boom, alongside a cascade of pulleys as a vang could be an option?
The car would be lightly loaded, provided you didn't try to fight the vang or sheet with it!

 

[lpdsn]

It would seem easy to cobble this up from a bit of mainsheet track and car, a suitable tube and the existing tackles for about the same expenditure as a Boomstrut, so why have I never seen it anywhere since?

It's handy to have some shock absorbtion capability in the kicker/vang. Other than that it sounds workable.

 

[Quandary]

It's handy to have some shock absorbtion capability in the kicker/vang. Other than that it sounds workable.

Struggling to understand what you mean here, I presumed there would be just as much elasticity in a tackle running along the boom as there is in one running at an angle from mast to boom? Anyway, since other than WHYW I am unlikely to go racing again, power, speed and efficiency of the kicker is not such a priority so I will probably go for the easy option and buy a Boomstrut. I think I was attracted by the idea of a bit of retrospective innovation. Thanks for all the responses.
Another thing that puzzles me about our Moody, is why with a stiff masthead rig supported by so much wire in all directions, did someone think it worth fitting a 24 to 1 wire and dyneema cascade purchase for the backstay? Not that I mind though, I just haul on it when it seems appropriate, I find it hard to detect any bend but at least the forestay must be straight.

 

[Hinata Sailing]

Hi, it seems this is an old trace but i want to hear more about it as I am struggling to figure what to do on our yacht.
On our 1985 Southerly 115, there is a similar setup to what you have described.

It comprised a one and a half m. length of strong alloy tube (about 32mm. dia.) from near the mast foot to a 6 wheel car running along a length of X section track below the boom, the car ran back and forward to move the boom up or down controlled by a tackle

Only difference is the car and how the tackle operates. Instead of a car, it is a metal bracket sliding inside the slot of boom section. And the tackle is only working for pulling bracket towards the mast to raise the boom. But no means of pulling the boom down. I have a doubt if this setup is correct. To be honest, I cannot even pull that line as it goes inside the boom over a pully and then comes out a hole under the boom and goes onto a jammer. I supposed to pull 1:1 and lock? That doesn't sounds right at all.

We purchased the yacht recently and previous owner had done some unprofessional work on it. I think the issue comes from time when the engine got broken in Fiji and they had to ship the yacht from Fiji to NZ and there wasn't any professional rigger to drop the mast down but somebody literally cut all cables, lines etc and loaded to a container ship. Then the owner set all lines up and laid many things wrongly.

I couldn't find any photo of a similar setup. As you said, all vangs consists of spring loaded solid vangs, hydraulics, Barton vangs etc... Does anybody know more about this kind of setup? I am nowhere close to be able to upgrade whole vang system but need to work with this system in most efficient way. Any help, photo, schematic would be helpful. Thanks in advance.