Why are booms on larger boats so high

[Daydream believer]

on my megre 31 ft boat i can drop the sail & if it is rough I can lay across the boom to help trap a flogging sail.
I notice how 40+ footers have things like mast steps etc to reach the sail at the gooseneck. this seems extremely dangerous & as long as the boom clears the crews head at cockpit level is there really any point in going higher. Or am I missing something?
I recently read a post where a husband & wife team ( 50 ft boat)got into trouble trying to lower the sail as they could not secure it safely without getting up onto the boom.
There are all sorts of sail catching systems including one which consists of brackets with webbing between to catch the sail. Once the sail is down the crew has to clamber up, walk along the boom zipping up the cover.
I can appreciate that the vang needs to be extended along the boom for leverage purposes but if that is the only reason why not have a vertical vang on to a track curved to match the radius

So why have it so high one might be thrown overboard trying to climb mast steps to reach the sail

 

[pvb]

I don't think booms are generally excessively high. They're usually positioned so that there's space for a sprayhood.

 

[johnalison]

I think one reason is the popularity of centre cockpits. Many of these boats have in-mast furling mains, so the height of the boom is not a problem to the crew. On the other hand, it presumably also means the centre of effort is high in relation to the sail area.

 

[prv]

I don't think booms are generally excessively high. They're usually positioned so that there's space for a sprayhood.

I suspect it's more about biminis for hot places, which are higher than a sprayhood because you need to be able to stand up under them.

Pete

 

[TQA]

The Lagoon 52 holds my personal record as the highest boom.

Mind you there is a flybridge steering setup.

 

[DannyB]

I nearly bought a Hanse a few years back, but after a trial sail, I stood up on the mast step to help put the sail away. The mast step pulled out of the mast pitching me on the deck, it appeared that the rivets failed. I decided to get a boat with a gooseneck I could reach without steps. It also made me wonder about the quality of build if the mast step failed on a new- ish boat.

 

[sailorman]

I don't think booms are generally excessively high. They're usually positioned so that there's space for a sprayhood.

even my Co32 had space for a hood below the boom

 

[Quandary]

Could it be anything to do with efficient rig controls, a vang (even a solid one) angled at less than about 30 degrees or so to the horizontal might put some extreme stresses on the mast. I know some multihulls manage without them but a proper mainsail needs one.

 

[Ludd]

Might it be that larger yachts are more likely to be coded for charter, necessitating a head- avoiding boom?

 

[dunedin]

Certainly this can be a bit of an issue above 36 feet or so.

To a degree it is not purely the boom height that causes a need for mast steps - a fully battened laminate sail with quality batten cars tends to be quite high above the boom when stowed.

One minor but very important suggestion from our recent experience - get a stack-pack/lay-bag. But make sure the zip closes from the boom end towards the front NOT the other way around. It is relatively easy to start the zip at the boom end with very little sail there. Then pull forward as far as can get to and sort the rest at leisure. The alternative of aligning two zip ends and starting the zip from the front requires 3 hands, telescopic arms, patience of a saint and vocabulary of a Glaswegian

 

[Tranona]

even my Co32 had space for a hood below the boom

That has a deep cockpit, unlike boats with aft cabins or centre cockpits.

 

[Daydream believer]

One minor but very important suggestion from our recent experience - get a stack-pack/lay-bag. But make sure the zip closes from the boom end towards the front NOT the other way around. It is relatively easy to start the zip at the boom end with very little sail there. Then pull forward as far as can get to and sort the rest at leisure. The alternative of aligning two zip ends and starting the zip from the front requires 3 hands, telescopic arms, patience of a saint and vocabulary of a Glaswegian

Which is totally the opposite to my experience.
When we first had our boat we were off Barfleur in a rolly sea & due to zero wind we dropped the main. My wife stood on the cockpit seat( without taking in the mainsheet) to grab the boom to start the zip off. She had nothing to hold on to to steady herself. As the boom swung across it hit her in the midriff, she was dragged over the side , hanging in mid air. Fortunately she hung on and as the boat rolled back she was flung back on the opposite side of the cockpit. On another occasion one of my crew nearly lost his balance & managed to wrench the slider off the zip as the boat rolled.Standing up on a cockpit seat with little or no support is dodgy to say the least. Even with the mainsheet in the boom still waggles about

As I now sail single handed I had the zip changed to start at the mast. I can now hold the mast to start the zip off ( greater safety)& do not have to go aft to do so & then back to the mast a second time

I would never revert to a zip starting at the boom end. I also have cords with toggles & loops inside the cover that I can fasten first to trap the sail so there is no load on the zip & I do not even have to do the zip up if it is really rough, Just 4 straps at the mast end

 

[geem]

Which is totally the opposite to my experience.
When we first had our boat we were off Barfleur in a rolly sea & due to zero wind we dropped the main. My wife stood on the cockpit seat( without taking in the mainsheet) to grab the boom to start the zip off. She had nothing to hold on to to steady herself. As the boom swung across it hit her in the midriff, she was dragged over the side , hanging in mid air. Fortunately she hung on and as the boat rolled back she was flung back on the opposite side of the cockpit. On another occasion one of my crew nearly lost his balance & managed to wrench the slider off the zip as the boat rolled.Standing up on a cockpit seat with little or no support is dodgy to say the least. Even with the mainsheet in the boom still waggles about

As I now sail single handed I had the zip changed to start at the mast. I can now hold the mast to start the zip off ( greater safety)& do not have to go aft to do so & then back to the mast a second time

I would never revert to a zip starting at the boom end. I also have cords with toggles & loops inside the cover that I can fasten first to trap the sail so there is no load on the zip & I do not even have to do the zip up if it is really rough, Just 4 straps at the mast end

I don't understand this. Are you saying that you didn't restrain the end of the boom before you started to do the zip up? Why not? We have a line made up that clips to the backstay and boom to hold the boom then we sheet the main in tight. The boom can't move, it's over the cockpit and you zip up. Simples. This would be difficult from the other end. At the back end of the boom the zip can stay together full time. Not possible at frot so lots of messing with zip ends

 

[Deleted member 36384]

I suggest that the higher freeboard of modern boats effects the air flow over the deck. The effect of the wind hitting a slab of hull and being diverted has probably been modelled and is now accounted for in the sail plan and rigging design to improve efficiency. Why have a lower boom on a wide stern, flat sailing, high sided hull that puts the lowest part of the main in some disturbed air zone? Just a thought but the larger cross sectional area of hull will effect the air flow to a power law ratio; would it not? As all modern boats are modelled to the finest degree before manufacture it would make sense to design the rig and sail for optimum efficiency. Just a thought.

 

[geem]

I suggest that the higher freeboard of modern boats effects the air flow over the deck. The effect of the wind hitting a slab of hull and being diverted has probably been modelled and is now accounted for in the sail plan and rigging design to improve efficiency. Why have a lower boom on a wide stern, flat sailing, high sided hull that puts the lowest part of the main in some disturbed air zone? Just a thought but the larger cross sectional area of hull will effect the air flow to a power law ratio; would it not? As all modern boats are modelled to the finest degree before manufacture it would make sense to design the rig and sail for optimum efficiency. Just a thought.

I can't see how that works. Higher boom means higher centre of effort on sail so more leaning over for same sail area. If you want to lean over less, ie stiffer boat, you need more keel weight. Not something you see a lot of in modern boats.
I suspect the higher boom will result in less performance but provides less risk of injury from boom but since most modern designs use in mast reefing the high boom is not such an access issue until you get a problem

 

[RupertW]

I don't understand this. Are you saying that you didn't restrain the end of the boom before you started to do the zip up? Why not? We have a line made up that clips to the backstay and boom to hold the boom then we sheet the main in tight. The boom can't move, it's over the cockpit and you zip up. Simples. This would be difficult from the other end. At the back end of the boom the zip can stay together full time. Not possible at frot so lots of messing with zip ends

I'm even more amazed at the need to zip up except at the beginning and end of a cruise. On a recent month long cruise it was undone at our starting marina when the boat was snugly tied up then done up again at our destination marina. Particularly when we are at anchor I want to be able hoist the main with minimum fuss.

 

[RupertW]

I can't see how that works. Higher boom means higher centre of effort on sail so more leaning over for same sail area. If you want to lean over less, ie stiffer boat, you need more keel weight. Not something you see a lot of in modern boats.
I suspect the higher boom will result in less performance but provides less risk of injury from boom but since most modern designs use in mast reefing the high boom is not such an access issue until you get a problem

I think you are probably right about the reason for higher booms - it's all about avoiding inexperienced sailors getting injured. However a stiffer boat comes from form first, and only when the boat is already significantly leant over does the keel really come into play, so a wide stern and flat bottom keeps the boat upright until...suddenly it isn't and trips unless there is a very deep heavy keel to get it quickly back upright.

 

[Deleted member 36384]

I can't see how that works. Higher boom means higher centre of effort on sail so more leaning over for same sail area. If you want to lean over less, ie stiffer boat, you need more keel weight. Not something you see a lot of in modern boats.
I suspect the higher boom will result in less performance but provides less risk of injury from boom but since most modern designs use in mast reefing the high boom is not such an access issue until you get a problem

The design takes all this into account, the wide beam, the form stability caused by the high volume hull. The design iteration that modern boats go through is quite intense. I don't see any conflict in a higher centre of effort and flat sailing with wide beam high sided yachts. It is not about inexperienced sailors and all about performance that modern sailing demands, that and interior space. Even on my lowly, centre cockpit Rival 41C, the boom easily clears everyones head.

 

[Poignard]

That has a deep cockpit, unlike boats with aft cabins or centre cockpits.

As does the 28' Twister. If I accidentally gybe, the boom just brushes my hair as it whizzes by! Yet the boom is only level with my waist when I stand on the coachroof to secure the sail.

 

[dunedin]

I'm even more amazed at the need to zip up except at the beginning and end of a cruise. On a recent month long cruise it was undone at our starting marina when the boat was snugly tied up then done up again at our destination marina. Particularly when we are at anchor I want to be able hoist the main with minimum fuss.

UV amongst other things.