Square top main sheet loads

[TJ D]

Hi forum,

To you performance guys out there-

Rocket Science is coming due for a mainsail replacement, and I'm really thinking about going to a square-top sail.

The boat has no fixed backstay if you're wondering.

Currently, we have a very heavily roached full-batten carbon/technora laminate main, (it's practically square-topped now) I can't remember the roach projection, but it's along the lines of 6 feet. Think performance multihull main on a monohull.

We have mid-boom sheeting, and the loads currently are about as high as we want to go.

So, here's the question-does a square top sail require even more sheet tension than what we're currently using? I'm guessing not, as we're pulling damn hard now during times that twist is not desirable. But, it would really be a bummer to have to replace the traveler and add carbon to the traveler backing as a result of a new sail!

Any thoughts? I haven't consulted a sailmaker yet, figured I'd start here.

TJ

[thinwater]

Originally Posted by TJ D

Hi forum,

To you performance guys out there-

Rocket Science is coming due for a mainsail replacement, and I'm really thinking about going to a square-top sail.

The boat has no fixed backstay if you're wondering.

Currently, we have a very heavily roached full-batten carbon/technora laminate main, (it's practically square-topped now) I can't remember the roach projection, but it's along the lines of 6 feet. Think performance multihull main on a monohull.

We have mid-boom sheeting, and the loads currently are about as high as we want to go.

So, here's the question-does a square top sail require even more sheet tension than what we're currently using? I'm guessing not, as we're pulling damn hard now during times that twist is not desirable. But, it would really be a bummer to have to replace the traveler and add carbon to the traveler backing as a result of a new sail!

Any thoughts? I haven't consulted a sailmaker yet, figured I'd start here.

TJ

I'd get an inexpensive load cell and figure out where I was. It may not be as high as you think.

[TJ D]

The load cell is not a bad idea. But, I'm pretty sure that I'm as high as I really want to go on loading now.

We had a chap on board who I allowed to sail the boat very aggressively on our recent transatlantic, and he managed to vaporize some torlon balls in the traveler. Ok, granted, they were probably old and worn out anyway, but that and the loading on the mainsheet winch sort of indicate that we're probably not well advised to increase the force required for a new main by very much without beefing up some components. I'd rather not do that, and simply stick with the same design if the square top sail does in fact require a lot more grunt on the sheet for essentially the same area.

Most of the reason for wanting to go square is that we should see some lighter batten loads than anything. I don't think that we'll actually gain all that much area.

Thanks, TJ

[flatop]

The angled top batten in a square topped main is a pain in the ass if dropping main into a boom bag mate. If you take the main off after every sail then no probs. The angled top batten has to be taken out to get a good flake of the mainsail or the top car on the mainsail track on mast has to be released to allow mainsail to flake into boom bag. A lot of hassle for not much more sail area really IMHO.

[TJ D]

Well, disconnecting the headboard slider's not that big of a deal, we can get at it pretty easily.
.
Like I said, it's mostly about batten loading. I think we'll gain a bit of power too.

Thanks, TJ

[TJ D]

But, back to the original question-

If these sails require significantly more mainsheet tension, that would probably be the only deal breaker for me.

Anybody know?

Thanks, TJ

[barnakiel]

I believe, all other things equal, same tension will see the top of the sail open more now. This is the idea behind the long top batten, not just the aerodynamics of the tip and the extra sail area. Control. You need the topping lift less now.

Imho it takes more tension to close the top of a square top sail. You will often see the sheeting moved to the end of the boom and the track run either across the whole beam or even curved. Plenty of control.

I love square top sails and would love one in my boat. I would go for it.

b.

[out42]

Barnakiel has it for me. From 3 boats with square-top mains, you will love it and yes, the sheet loading will increase if you really want to close off the top of the main. However, do you want it that tight? One of the reasons a square-top is nice is that it will twist off in gusts losing you power right at the top of the sail - generally a good thing. If in light conditions, it won't. Again generally a good thing.
Sounds to me like you've got work to do anyway on the traveller set-up, so beef it up this winter, increase the strength of your 2:1 halliard and make sure the top two batten cars are up to it.

Sounds like an awful lot of hassle but I guess it will be worth it.

[Boatguy30]

You will only want to close the top in light winds. I have a square top sail of about 400 sq ft run off a 7:1 sheet. I can trim it to stalling based on my sheeting angle of my jib leads into the low 20s apparent.

I doubt the sheet loads on a pin head sail would be less, I'm fact in gusts I bet they would be more as you have less twist up top. For the same sail area.

There are a bunch of ways to deal with the top batten issue including some rather expensive headboard auto release cars.

I used s simple dyneema bridle that probably wouldn't suite a 55' boat

[bsurvey]

fat head mains are very in right now as are full batten mains.


the are nott easy to depower ie twist off the top to keep the boat ffrom sailing on its ear.


bettter to be conventional where the vang, Cunningham out haul and main sheet can be used in various combinations to keep you more up right going to weather, less stress and stran on the mast and rigging


I am from SF in blows 30 here on a normal day

[FSMike]

Who designed your boat?
Who produced/designed your rig?
Seems like they would be the people to ask.

[TJ D]

Well, the boat was designed by Paul Bieker, the rig was designed and produced by Hall Spars.

But, neither of these people will have mainsheet loading at their fingertips. And, Paul's a busy man designing AC hydrofoils in Bermuda at the moment. I don't like to contact him for stuff like this.

We fortunately already have the 2:1 halyard way oversized, but I actually think that our halyard loading won't be different with a square top. The roachy beast that's on there is probably at least as heavy on the halyard. Maybe even more so.

Our gear is not undersized for what we have on the rig now, but if we were having to come up with, say, 50% more sheet tension to trim the sail right, I would find that to be too much. So, I guess that's really the question.

We simply can't switch to end-boom sheeting. We already have a full-width curved traveler, but it's staying right where it is.

I'm not too worried about stowing the sail, especially if we can just disconnect the sail from the headboard slider. That's not a big deal.

So, I guess that was my question all along-how much more load on the sheet. Since we're not using what would be called a 'pin-head' by anybody anyway, It's possible that we're not going to see a big increase.

Probably time to call our sailmaker! I was hoping somebody here might have that information in hand here on the CF as a first step, however.

I do believe that the performance gains will be pretty good.

Good posts, friends. Thanks, TJ

[Gmcgyvr]

Originally Posted by TJ D

Well, the boat was designed by Paul Bieker, the rig was desiwhen you get the new main; have the sailmakergned and produced by Hall Spars.

But, neither of these people will have mainsheet loading at their fingertips. And, Paul's a busy man designing AC hydrofoils in Bermuda at the moment. I don't like to contact him for stuff like this.

We fortunately already have the 2:1 halyard way oversized, but I actually think that our halyard loading won't be different with a square top. The roachy beast that's on there is probably at least as heavy on the halyard. Maybe even more so.

Our gear is not undersized for what we have on the rig now, but if we were having to come up with, say, 50% more sheet tension to trim the sail right, I would find that to be too much. So, I guess that's really the question.

We simply can't switch to end-boom sheeting. We already have a full-width curved traveler, but it's staying right where it is.

I'm not too worried about stowing the sail, especially if we can just disconnect the sail from the headboard slider. That's not a big deal.

So, I guess that was my question all along-how much more load on the sheet. Since we're not using what would be called a 'pin-head' by anybody anyway, It's possible that we're not going to see a big increase.

Probably time to call our sailmaker! I was hoping somebody here might have that information in hand here on the CF as a first step, however.

I do believe that the performance gains will be pretty good.

Good posts, friends. Thanks, TJ

When you have sailmaker make new main; get the top batten of the square top feeding in from the luff, not the leech. Easy to remove when stowing away.

[TJ D]

Originally Posted by Gmcgyvr

When you have sailmaker make new main; get the top batten of the square top feeding in from the luff, not the leech. Easy to remove when stowing away.

I wonder if I'm missing something here.

I have to go to the headboard to disconnect the halyard anyway, so it's really not a problem to disconnect the headboard from the slider (we have an Antal external track). This would be quite simple. Do I also have to remove a batten to get it to store on the boom, or is that enough? Not that taking a batten out's a big deal anyway.

Thanks, TJ

[admiralslater]

Would it be possible to use another car on the track to reduce point loading or are you concerned about the overall load .In theory and feel free to correct me, the main load would be generated from the end of the boom straight to the mast head so if you are running a big roach now the square head may not increase the load all that much . In fact the biggest load differences may be in lightish winds before the tops falls away.
I love buying new sails