Boom Brake

[fishermantwo]

Discussing boom brakes with a mate and I said I was considering making one. He said that he has a figure 8 descender that cost $20 and works perfectly. Looking at it logically makes sense but why are they not in widely used?

 

[Neil_Y]

Seeing as the main sheet should have enough purchase to control the boom I've always found that sheet in and controlled release work fine. I tend to use a preventer if running with the main or just twin headsails though if it's for more than a mile or two. Having a boom brake adds a rope obstruction to going forwards I would guess but a fig8 should work nicely if you want one.

 

[lw395]

They have their uses, in light winds and rolly seas, but mostly you either want a proper preventer rigged to the end of the boom, or nothing.
Booms are not usually built to be controlled by a brake in the middle, and if you ask too much of a brake, it will break the boom.
You also need to be able to release it quickly and easily to do a proper controlled gybe, as a brake is not a substitute for gybing safely with the mainsheet in control IMHO.

 

[NUTMEG]

This topic came up a while ago. I bought a large 'descender' climbing thingy, as you say, about £20odd.

Rigged it on mooring and it seems as if it would work, the only problem is getting the rope tension just right. Too tight = boom will not move but too loose then it does nothing.

Never used it in anger, under way though, had no occasion to do so.

 

[rotrax]

This topic came up a while ago. I bought a large 'descender' climbing thingy, as you say, about £20odd.

Rigged it on mooring and it seems as if it would work, the only problem is getting the rope tension just right. Too tight = boom will not move but too loose then it does nothing.

Never used it in anger, under way though, had no occasion to do so.

.We bought a Petzl? figure of eight. Not done much sailing this year-**** weather plus a funeral- to test it but alongside it works fine. We have reasonable control over tension through two snatch blocks forward and cleats on the outside edge of the cockpit. I used a snap shackle to mount it on an extra boom bale I fitted. I have heard others suggesting that it may break the boom. Our mainsheet bales are only a couple of inches behind the bale for the brake and with its purchase can apply big loads. I want the ability to slow the boom down in an accidental gybe. I get the feeling from my alongside testing that we have a good chance of it doing just that. Time will tell.....................

 

[lw395]

If your mainsheet is in the middle of the boom, it will probably be a heavier section than one designed for a sheet at the clew.
It could still break the boom if you are going fast down wind and roll or broach to the point where the boom hits the water.
How far you have to roll to do that varies a lot from boat to boat.

I've been on boats that have put the clew well in the water, but I'm more careful who I race with these days....

I just think you need to be clear about what these things are for and know when you need a proper preventer instead.

 

[rotrax]

If your mainsheet is in the middle of the boom, it will probably be a heavier section than one designed for a sheet at the clew.
It could still break the boom if you are going fast down wind and roll or broach to the point where the boom hits the water.
How far you have to roll to do that varies a lot from boat to boat.

I've been on boats that have put the clew well in the water, but I'm more careful who I race with these days....

I just think you need to be clear about what these things are for and know when you need a proper preventer instead.

Thanks for your concern and advice. Our boat is a fat 'ol cruising long keeler and is very stiff. We usually use jib or staysail when running in strong conditions, a wing on wing mainsail and jib in light winds. For the boom end to touch the water in a roll would be highly unlikely due to the shortish boom and the position of the aft shroud. Went to Chichester Harbour from Gosport recently, blowing a good six from the SW. Full jib only, 7.6 kts. against the tide, not too much roly poly either. Having suffered two acidental gybes with a flukey wind from dead aft when using the main, I thought a figure of eight for £15.00 off EBAY was worth a punt. When its tested for real, I'll let you know...................

 

[[2574]]

I just think you need to be clear about what these things are for and know when you need a proper preventer instead.

I always think that a "proper preventer" led from the boom end forward to a block at the bow must exert enormous forward force to the mast at the gooseneck (in the event of an accidental gybe) because of the acute angle of incidence between the preventer (from boom end to bow) and the boom itself as it is forced toward midships by the gybe when great tension comes on to the preventer line. There is no support for the mast preventing it being forced forward by the boom. For that reason I've always favoured the idea of a preventer from the toe rail near the (aft swept shrouds) chainplate up to the boom as the angle is almost perpendicular thereforemuch less forward loading on the mast. My thinking could well be utter tosh though; I ain't no rigger!

 

[lw395]

I always think that a "proper preventer" led from the boom end forward to a block at the bow must exert enormous forward force to the mast at the gooseneck (in the event of an accidental gybe) because of the acute angle of incidence between the preventer (from boom end to bow) and the boom itself as it is forced toward midships by the gybe when great tension comes on to the preventer line. There is no support for the mast preventing it being forced forward by the boom. For that reason I've always favoured the idea of a preventer from the toe rail near the (aft swept shrouds) chainplate up to the boom as the angle is almost perpendicular thereforemuch less forward loading on the mast. My thinking could well be utter tosh though; I ain't no rigger!

I'm afraid to say I think your thinking is a bit misguided.
If the preventer is rigged to the clew, and the clew hits the water, the main force goes directly from the clew to the preventer line.
There will be some compression in the boom but a fraction of the preventer force.
Whereas a preventer rigged at the kicker will put the force at the clew into the gooseneck, multiplied by the lever ratio of the boom, taking the preventer point as a pivot.
That's not very clear, I might re-write that, sans Merlot, tomorrow. (sorry)

The best defence for accidental gybes is a decent helmsman and a course to steer at least 10 degrees off downwind. Unless you are racing, steering 10 degrees off and putting a controlled gybe in won't even cost you a a pint's worth of drinking time. It's often actually faster.

 

[rotrax]

I always think that a "proper preventer" led from the boom end forward to a block at the bow must exert enormous forward force to the mast at the gooseneck (in the event of an accidental gybe) because of the acute angle of incidence between the preventer (from boom end to bow) and the boom itself as it is forced toward midships by the gybe when great tension comes on to the preventer line. There is no support for the mast preventing it being forced forward by the boom. For that reason I've always favoured the idea of a preventer from the toe rail near the (aft swept shrouds) chainplate up to the boom as the angle is almost perpendicular thereforemuch less forward loading on the mast. My thinking could well be utter tosh though; I ain't no rigger!

I agree that a preventer may be a more suitable method of controlling the boom when running. The advantage of my cheapo boom brake (I hope) is that it will not require moving from the cockpit once rigged. I would have to go forward with the line to rig a preventer on opposite side. It might be different on a long ocean passage where winds are reliable, but most of our sailing seems to be with unreliable and changeable winds. Some years ago I did a fast night passage on a Brixham Trawler from Dartmouth to Brixham. Blowing hard from due West. The skipper got the crew to rig a preventer and we ran dead downwind in big following seas with the boom kissing the tops of the waves. Exiting stuff- especially going forward to rig the line with the covering board under water. I hope that the friction I can put on the figure of eight will hold the boom enough, and by relaxing the line, allow some control of the speed the boom makes changing sides.

 

[William_H]

Boom brake

The figure 8 devices you refer are used for abseilling where they are an easily manged brake on the rop you are sliding down. Brilliant IMHO.
For use as a boom brake the size of rope through the figure 8 and the tension on the rope would dictate the friction provided while the position of the attachment on the boom ie midway or at the end would dictate the actual slowing down power. If you have a loose footed main I would suggest a webbing loop around the boom which can be located by a screw or similar so that you can try it at various points on the boom and a small tackle on the rope so you can adjust tension.
My solution to gybes was a new carbon fibre light weight boom. Brilliant. olewill

 

[lw395]

I can see some attraction in a figure 8 type device, but I would want to be able to quickly lose all that friction to gybe the boom properly. That seems to imply some sort of tackle led back to the cockpit.
Likewise with a proper preventer, you can pre-rig the lines and lead them back to the cockpit.
We used to use the spinnaker foreguy pulley on the foredeck and the aft mooring cleats. You could probably use the bow cleats on many boats as the turning point on the foredeck, they don't need to be adjusted under load.
If you have both sides rigged, you obviously need to avoid any slack lines crossing the boat during a gybe. For cruising we would normally just use one and gybe through a bigger angle, then bear off after the preventer was sorted. There was no need to go forward of the mast to change preventers.

There does come a point where having this kind of gear encourages you to carry a little more sail than might be prudent...

 

[rotrax]

It is easy to almost lock the boom solid with our f-o-e just by pulling the line-on either side-a little tighter and cleating it off. No need to go forward at all. To rig it the snap shackle at the f-o-e is clipped on the boom bale, the two snatch blocks are attatched to the midships cleats by their caribiners and the line led through and back to the cockpit side cleats. Obviously rope stretch must be watched,and adjustments made to suit. As I said, we have only rigged it while alongside, but reasonable tension on the f-o-e makes it very hard to push the boom over. Also, according to the instruction leaflet, another turn around the flanks of the f-o-e increase friction substantialy. I will post a progress report when we have used it in anger-you never know-summer may yet appear..........