SailNet is a forum community dedicated to Sailing enthusiasts. Come join the discussion about sailing, modifications, classifieds, troubleshooting, repairs, reviews, maintenance, and more!

Advantages of midboom sheeting?

6286 Views 20 Replies 16 Participants Last post by CalebD, Oct 21, 2009

jbarros

Discussion Starter · Oct 19, 2009

I was reading about the history of the C30 when I saw it had been improved and updated during the mkI phase, to midboom sheeting. It would seem to me that endboom sheeting would give you more leverage, and put it closer to the tiller/wheel for easier singlehanding.

What is the advantage which makes midboom sheeting an upgrade?

Thanks

- James

1 - 20 of 21 Posts

davidpm

· #2 · Oct 20, 2009 (Edited)

I suspect that the most likely reason to go to mid boom sheeting is that on boats of that size end boom sheets tend to be angled pretty close to the helmsman's head.
In fact on a 28' boat I was on recently you had to sit or the sheet would take your head off.
Which for those of us that wear hats would be an inconvenience.

There is no good solution AFAIK for main sheets.
Mid Boom on the cabin trunk like the Catalina 30 and you have to have a lot of tackle which takes time to sheet in and it is too far from the helm for single-handing.

Bridgedeck sheeting is in the way of the companionway.

Sheeting in the middle of the cockpit like the j24 is perfect for the helmsman but cuts the cockpit in half and interferes with parties.

End boom sheeting means the sheet is behind you and keeps taking your hat off on every tack.

The best solution I have found is to drop the sail, sheet the boom to far port and dock on starboard so it is easy to get off the boat without hitting your head.

See less See more

Faster

· #3 · Oct 20, 2009

Mid boom sheeting has few (if any) advantages from a performance/handling point of view, but what it does do is clear the cockpit of obstructions. This facilitates lounging there, and simplifies installations of dodgers and biminis.

For short handed sailing, though, without elaborate sheeting arrangements generally the mainsheet becomes inaccessible to the helmsperson, esp on wheel-steered boats.

captbillc

· #4 · Oct 20, 2009

on my nimble 30 express the traveler is across the front of the seats and a little over a foot aft of the hatch so the sheeting is about 3/4 back from the mast to the end of the boom. this works out well.

sailortjk1

· #5 · Oct 20, 2009

Faster said:
Mid boom sheeting has few (if any) advantages from a performance/handling point of view, but what it does do is clear the cockpit of obstructions. This facilitates lounging there, and simplifies installations of dodgers and biminis.

For short handed sailing, though, without elaborate sheeting arrangements generally the mainsheet becomes inaccessible to the helmsperson, esp on wheel-steered boats.

Nailed it!

scottyt

· #6 · Oct 20, 2009

i have cabin top mid boom. the line does go thru a cam cleat, which i can control from behind the wheel. i like it with 2 exceptions, one it stops me from having a dodger, two it is a fair amount of line to pull to go from a reach to a tack. but honestly the line is not a big deal, it only takes a few seconds to pull it all in.

yes end boom does give better leverage but they normally offset that with more pulleys, but that means more line.

i think each boat is different, what works in one will not work in another. maybe the "upgrade" just works better on that boat

BarryL

· #7 · Oct 20, 2009

Hello,

Advantages of mid boom sheeting:

Main sheet is out of the cockpit so guests don't trip on it.

traveler becomes more effective because the working length gets longer the more forward the sheet is.

Disadvantages of mid boom sheeting:

more force is required to move the boom
the main sheet may be a far away from helmsman

Barry

JohnRPollard

· #8 · Oct 20, 2009

Some of the mid-boom sheeting arrangements I've used worked fine. Others were terrible. So while there are some general observations about pros/cons, like ScottyT said, it can really depend on how it's implemented on the specific boat.

davidpm said:
Bridgedeck sheeting is in the way of the companionway.

It can depend partly on the design of the bridgedeck. Our traveller is mounted there, but it's not in the way because our bridgedeck is deep. There's very little effort getting around it.

I prefer having the mainsheet traveller mounted on the bridgedeck while sailing. The traveller is readily accessible for tweaking, and the mainsheet attaches to the boom about 4/5 of the way out toward the end, giving it plenty of mechanical advantage.

The mainsheet unclips from the traveller and secures outboard of the cockpit at anchor. So there's no issue with the mainsheet impeding occupants of the cockpit when lounging.

klem

· #9 · Oct 20, 2009

Many good points have been brought up, one more that I can think of is that it allows your boom to be built a little lighter to have the sheet partway up it. You don't put as large a bending force on the boom by decreasing the unsupported distances. It is a similar theory to why the shrouds on small boats only go about 2/3 of the way up the mast. Be wary though, this is not true for loose footed sails where you really should have the sheet come from where the clue attaches.

paulk

· #10 · Oct 20, 2009

Not quite, Klem

klem said:
Many good points have been brought up, one more that I can think of is that it allows your boom to be built a little lighter to have the sheet partway up it. You don't put as large a bending force on the boom by decreasing the unsupported distances. .

Unless I read you wrong, midboom sheeting requires a stronger, heavier boom because the lever arm that the sheet has to work with to hold the boom in place is that much shorter. The sail still pulls with the same force, regardless of where the sheet is, so to overcome that force with less of a lever arm, (as in mid-boom sheeting) the power of the sheet needs to be increased. A sail that you could control with 3:1 sheeting at the outboard end would need 6:1 to give the same control if it were attached in the middle of the boom. 6:1 pulling down in the middle of the boom is much more likely to bend (read: break) the boom than 3:1 pulling on the end. Booms with mid-boom sheeting therefore need to be stronger and heavier, not lighter. Mid-boom sheeting also requires beefing up of the cabin tops and traveler rails that they're mounted on for the same reason: you don't want to be increasing the headroom below when you trim your mainsheet.

Faster

· #11 · Oct 20, 2009

klem said:
Many good points have been brought up, one more that I can think of is that it allows your boom to be built a little lighter to have the sheet partway up it. You don't put as large a bending force on the boom by decreasing the unsupported distances. It is a similar theory to why the shrouds on small boats only go about 2/3 of the way up the mast. Be wary though, this is not true for loose footed sails where you really should have the sheet come from where the clue attaches.

With respect, I think the bending forces on the boom are greater with a midboom sheeting arrangement. The loads from the main are primarily at the tack (well supported in any configuration) and the clew (well supported with end (or close to) boom sheeting) This is true whether the sail is loose footed or not. This leaves (with mid boom) a large unsupported section aft of the mainsheet attachment, and esp in an uncontrolled gybe a mid boom sheeting arrangement will, IMO, be more likely to fail than end boom.

deniseO30

· #12 · Oct 20, 2009

I should take a pic of it. My O30 has the traveler across the bunk just aft of the companion way. it's 5.5 ft long! I love it! garhaurer! The lines are long enough for me use from behind the wheel. the Mainsheet connects about 3/4 back on the boom it's not in the way when move it to one side while docked. I did want to move it to the cabin roof but glad I didn't.

CalebD

· #13 · Oct 20, 2009

A fellow racer at our club on the Hudson River recently BENT his boom on a gusty day (> 30 kts.) after a jibe of his main in his C30 with mid boom sheeting and no preventer rigged. Perhaps partly operator error, gusty conditions and insufficient tolerances in rigging.
I am not convinced that end boom sheeting would have prevented the damage he sustained in a forceful jibe.
I am also not convinced that a bridge deck traveler and main sheet would have prevented the same damage.
A good 'preventer' system may have but other damage could have been sustained as the winds did gust to near 40 kts. that day.
Mostly, racers love to push the envelope and usually end up breaking things, which my friend did by bending his boom and stressing his goose-neck fitting.
I am not sure that different boom sheeting strategies will decrease the number of failures one can expect. My guess is that someone at the helm who can see the gusts coming can compensate for the wind shifts that come with a gust better then where the boom is sheeted and try to avoid an accidental jibe, knock down, round up or whatever you want to call it.
This is an extremely important topic for those who want to sail the oceans blue as you will be jibed at some point. Your gear and rig has to be able to handle it or your life is at stake.
Meanwhile, racers who are close to home can risk it all by keeping all sails up and winging it.
Stuff breaks, but more on racing boats.

See less See more

Yorksailor

· #14 · Oct 20, 2009

There have been deaths reported, in racing situations, when an 'end of boom' mainsheet caught the helmsman's head or neck during an accidental gybe.

Yesterday while practising MOB drills with my wife we had and accidental gybe, the 'end of boom' mainsheet caught the bimini and ripped out half the bimini supports..fortunately nobody's head/neck was in the way.

JohnRPollard

· #15 · Oct 20, 2009

paulk said:
Unless I read you wrong, midboom sheeting requires a stronger, heavier boom because the lever arm that the sheet has to work with to hold the boom in place is that much shorter. The sail still pulls with the same force, regardless of where the sheet is, so to overcome that force with less of a lever arm, (as in mid-boom sheeting) the power of the sheet needs to be increased. A sail that you could control with 3:1 sheeting at the outboard end would need 6:1 to give the same control if it were attached in the middle of the boom. 6:1 pulling down in the middle of the boom is much more likely to bend (read: break) the boom than 3:1 pulling on the end. Booms with mid-boom sheeting therefore need to be stronger and heavier, not lighter. Mid-boom sheeting also requires beefing up of the cabin tops and traveler rails that they're mounted on for the same reason: you don't want to be increasing the headroom below when you trim your mainsheet.

That's exactly right, Paul. Mid-boom sheeting requires a heavier-duty boom.

We were recently slipped next to a Bristol 41 that had been re-rigged with in-mast furling, including a new boom to go with it. While sailing between Block Island and Cape May, the new boom snapped at the mid-boom sheeting attachment point.

It turns out that the spar company had spec-ed the boom for a Bristol 41 center-cockpit, which uses an end-boom sheeting arrangement. This was an aft-cockpit Bristol 41, which uses mid-boom sheeting and therefore requires a much stronger (heavier) boom extrusion.

klem

· #16 · Oct 20, 2009

Wow, I didn't think that I was going to start such an argument over what is probably one of the least important aspects of mid boom sheeting (providing it doesn't break). All of the boom failures that I have seen from mid-boom sheeting have always been due to improper attachment of the sheet to the boom which causes stress concentrations. Simply putting a bolt through the boom or a rivet is really poor design. If you look at modern race boats, they often use strops or high surface area metal fittings to distribute the load. All of the failures that I have seen due to end of boom sheeting have been bending failures at the midpoint of the boom.

Whether this is a valid point or not really rests on where the force applied by the sail acts on the boom. Obviously the tack and clue are high force areas (and the only ones for loose footed). However, many sails are cut to distribute the force along the boom in which case you develop a very large bending moment in the center. This is the situation where mid boom sheeting makes sense. And mid boom sheeting does not necessarily mean right at the midpoint in my definition, it is generally something like 2/3 of the way back. The case mentioned above with in mast furling was a case of a loose footed sail which should not have mid-boom sheeting.

On a boat that I sail on a lot, the boom actually snapped due to the bending forces mid-boom(end of boom sheeting). The solution was to have the sheet start on the cabin top, run to an ironwork mid-boom, run to the end of the boom, down to a block on deck, back to the boom, along it to a turning block mid-boom and down to the cabin top. This provided a 4:1 purchase although 2 parts had much less leverage and a boom that does not ever show signs of failure anymore although it is the same boom as before.

Sorry for dragging this one kind of of topic, it is important that your boom be strong enough but that is up to the designer and how it works for the people sailing the boat is probably the real point of this thread.

See less See more

Jeff_H

· #17 · Oct 20, 2009

"However, many sails are cut to distribute the force along the boom in which case you develop a very large bending moment in the center. "

Virtually all modern sails that I know of are not made to distribute the load onto the boom. Pretty much all modern sails, even ones with boltropes for the boom are made with some shelving in foot area so that they can be flattened going up wind and rounded on a reach and run. Even in the case of an older sail where there was some load going into the boom, the clew loads were far greater and so in no case that I can think of would the boom be lighter because of mid-boom sheeting.

As has been said, other than the fear of having mainsheet in the cockpit, Mid-boom sheeting offers no advantages in terms of ease of handling (loads are much greater since the leverage of the boom length is lost. This lost leverage can be partially offset by using higher purchase tackles but at the price of much higher frictional losses.), sail shape control (leech tension upwind in a breese is nearly imposible to properly control with most mid-boom sheeting set-ups), or ease of operating the boat (mainsheet and traveller adjustments generally mean walking to the forward end of the cockpit and using a winch to make adjustments).

To me a cabintop mounted mainsheet is a deal killer as a serious safety issue. I consider that fact that cabin top sheeting eliminates the ability to respond to a sudden change in conditions as endangering the vessel and its crew. Then again I tend to sail in a much wider range of conditions than most so this may be an acceptable feature for the casual sailor.

Jeff

See less See more

Faster

· #18 · Oct 20, 2009

klem said:
Wow, I didn't think that I was going to start such an argument ....
Sorry for dragging this one kind of of topic, it is important that your boom be strong enough but that is up to the designer and how it works for the people sailing the boat is probably the real point of this thread.

This is no argument.... this is just a debate. You want arguments there are other threads here for that!

I do agree with your last statement; that regardless of set-up obviously the boom has to properly engineered. I still, however, disagree that there is any significant non-compression load on the boom along the mid-foot area of any mainsail, except possibly in extreme downwind conditions (with an attached foot sail).

However, for all our sakes lets hope our booms hold together even when we make a handling error!

Melrna

· #19 · Oct 20, 2009

Buy a Hunter with the ARCH,, end boom sheeting, No worries about heads, hats getting cut off, better control over the mainsail, longer travellers and all lines are at the helm for single handling sail and cockpit is free from all sheets and mechanic equipment.
If you don't want a Hunter build a ARCH. Enough said.

blt2ski

· #20 · Oct 21, 2009

2

Ummmmmm,.....one can still break a boom with end boom, or in my case 90% to the end.

This broke right behind where the vang is, and where the lower shrouds hit the boom. so a combo from a mid 30 knot winds, accidental gybe, with a double reef no less too!

Any way, My traveler is right behind the cabin entry too. here is a side shot.

For my boat, well with in the reach of the tiller, genoa sheets come to the same general area. so two or even one can get to all the controls from one spot.

marty

See less See more

1 - 20 of 21 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.