New extreme roach flat top main?

[monte]

Well it's a 2m length of 6mm dynema with no sign of chafe after 10,000 miles, but we do have 60m of 8mm dynema on board just in case...

[tuskie]

The Lagoon system works well, the sail top tensions evenly and drops down straight into the bag. No sign of chafe on our boat either, but then again we motor 100% of the time as well.
Thinking of replacing it however; as I'm a bit nervous about dyneema being exposed to sun long term. Ours is nearly 5 years old. If it let go under load due to UV degradion it could ruin our morning.

The only drama I've heard of has occurred when the dyneema has been replaced and Monte's diagram has not been followed.

Of coarse, all square top main designs I've seen have the disadvantage of needing to have the main halyard disconnected before the sail bag can be fully zipped closed.
Not a big problem in the scheme of things.

[monte]

We generally clip the halyard to the lazy jack on the lazybag and then zip up to that. Forward of that the bag pulls over the sail quite nicely with just a small gap. One benifit of square tops is no more halyard slap 🙉
Edit: we could actually just release more halyard and secure it at the mast if we want to zip the bag closed..

[44'cruisingcat]

Originally Posted by donradcliffe

Has anyone reported any chafing issues with the square top battens?

Chafing against what?

[UNCIVILIZED]

You've already got a lot of SA from your current, heavily roached, main. At least by the numbers you're giving (67% of P x E). So barring going to a main with a super big square top, you're not going to gain that much more SA, 7.8% by your numbers.

The biggest perk to the switch would likely be from a square top having a lesser drag coefficent. So it's worth asking your sailmaker how much gain he can categorically state that you'd gain by making the switch. Especially as your current sail should be fairly efficent, as is.

Thus, odds are, you'd be doing better to optimize what you have. And or getting a bit more of an eliptical tip shape up high, on your new main. In order to save you both some money, especially on the new; sail, headboard, battens, batten hardware, & sail track hardware. Plus not needing to reinvent the wheel.

If you really want to up your boat's performance, consider look at filling the holes in your headsail inventory. Making it easier to power the boat up & down, sans much effort on the part of the crew.

So, if you do decide to go with a square top rig, then you're faced with both new hardware, as well as some new learning curves. For the trimming all of your sails, possibly to include new sheeting angles/tracks for your headsails. And too, a new driving style to go with the new sailplan, also.
Plus there's the picking & dialing in of new hardware for everything.

On battens, you're sailmaker should be able to fix you up with some. They'll be able to make recommendations on battens based on your sail's; size, shape, & material. Plus the boat's performance characteristics, including weight, beam, righting moment, etc.
That, & they should have some of the better batten maker's on speed dial. In adition to being able to explain to you, their top 3 choices, & why they chose such.

Though, keep in mind, that in order to find ones which fit the handling characteristics of the sail, may require some trial & error. And custom battens for a sail of that size ain't cheap.
But I'll skip the whole custom designed batten thesis thing.


PS: If you're toying with the idea of flying a hull, make sure that your foils are up for such loads first.

[tomfl]

Originally Posted by davecalvert

Of the current main doesn't have much roach the increase with a wide square top can be quite a bit. On racing mains, we use head widths around 40% to 50% of the foot length. On performance cruisers less. There is an issue with square top mains for cruisers having trouble releasing the head from the top slide assembly. Doyle Sails has a special headboard assembly to allow larger square top mains to automatically have the head come away from the top slides when lowered but, these start at around $2,200.00. I recommend not going with square top mains on cruisers but, going with an elliptical head design. This has the same sail area using a rounded head supported with a couple of battens spaced close together. These top battens are parallel to the boom for easy stacking.
The advantages of the extra sail area up high and better upper leech twist are simular to square top mains.

All true and worth quoting in full.

But the big advantage a square top has over a main with lots of roach is best explained by this story. On his death bead Albert Einstein said 'I have two questions for God, why relativity and why turbulence; I am optimistic on getting an answer to the first". There is a reason all the racing boats have a square top regardless of how much roach they have, to reduce turbulence.

Back in the day my mass transport phenomena class used a book we called brightfoot which was a combination of the last names of the two authors. I was unable to find it on Amazon, but here is this years model of a text on the subject. You probably need to have completed a partials class before you start reading that book.

No wonder little Al didn't like turbulence.

On the bright side there are less expensive options to the Doyle solution, one was posted earlier and it is easy to find more details, google is your friend.

[geoff326]

Originally Posted by tomfl

All true and worth quoting in full.

But the big advantage a square top has over a main with lots of roach is best explained by this story. On his death bead Albert Einstein said 'I have two questions for God, why relativity and why turbulence; I am optimistic on getting an answer to the first". There is a reason all the racing boats have a square top regardless of how much roach they have, to reduce turbulence.

Back in the day my mass transport phenomena class used a book we called brightfoot which was a combination of the last names of the two authors. I was unable to find it on Amazon, but here is this years model of a text on the subject. You probably need to have completed a partials class before you start reading that book.

No wonder little Al didn't like turbulence.

On the bright side there are less expensive options to the Doyle solution, one was posted earlier and it is easy to find more details, google is your friend.

Presumably a square top main has the advantage of being able to twist off in the gusts, which I would have thought on a catamaran would be a desirable feature re safety.

[Barra]

The one problem I foresee with the squaretop main is with the topping lift (at least for my rig which uses twin mainsheets)

ie in light air I use topping lift tension to steady the boom against the 2 main sheets. On tacks or gybes i then need to switch it to the windward side on opposite tack - easy enough with my current roached main but on a fat head i can see this being a bit more fiddly.

Anyone else had to deal with this issue?

[monte]

Yeah it wouldn't be possible Barra. A second topping lift would be needed (or a trip up the mast each tack )

[44'cruisingcat]

TBH that wouldn't really be possible even with our current normal roach sail. You'd need to loosen the topping lift by a huge amount to get it round the head of the sail.

[Nicholson58]

One of my other boats is a Tornado Cat. Extreme gaff-top Kevlar as you describe. In most winds the added top makes the top of the mast & main functional. In a normal main, the top of the sail is significantly wind shadowed by the mast. I figure the Nicholson with in-mast roller furled main, the top 5 feet is worthless. On the Tornado, the top adds way more to boat speed than the area calculation alone would suggest. On a Tornado, this is + 15% over the original design. The tuning of this sail with various tweakers lets the top be let-off in high wind but the battons prevent flapping. This is quite versatile as sails go. I must remove the Tornado top batten every time the sail comes down but we remove and roll it.


A good sail maker should be able to make sure the fit & function is good.

[Barra]

So what do you guys do when your boom is flopping around in light air with some adverse wave action given most cats dont have a vang?

I find traingulating the 2 main sheets and the topping lift anchors the boom and stops the main depowering. After a tack i just give the loosened topping lift a little flick and retighten to the new windward side of the main.

Ive got a decent roach but not that much up high (see the avatar) so the "flick" is pretty easy. I can see that getting more tricky the longer the fat head.

What do you guys do in these conditions?

[monte]

Originally Posted by Barra

So what do you guys do when your boom is flopping around in light air with some adverse wave action given most cats dont have a vang?



I find traingulating the 2 main sheets and the topping lift anchors the boom and stops the main depowering. After a tack i just give the loosened topping lift a little flick and retighten to the new windward side of the main.



Ive got a decent roach but not that much up high (see the avatar) so the "flick" is pretty easy. I can see that getting more tricky the longer the fat head.



What do you guys do in these conditions?

Turn the engine on of course
No we just deal with the flop. Usually tighten the main as much as possible. Even though generally a fuller main is ideal in light air, when it's light a flatter main works better for us. A lot of our sailing is on one tack so we raise the main to leeward of the topping lift usually. Our traveller is on the Bimini so there's not as much slack as it was in the transom of the 380, but the duel mainsheet setup on catanas makes a lot of sense, combined with the topping lift, for pinning the boom in place.

Btw, once you leave the med, light upwind sails are a thing of the past 😎✌️😜🏄👙

[UNCIVILIZED]

Originally Posted by Barra

So what do you guys do when your boom is flopping around in light air with some adverse wave action given most cats dont have a vang?

I find traingulating the 2 main sheets and the topping lift anchors the boom and stops the main depowering. After a tack i just give the loosened topping lift a little flick and retighten to the new windward side of the main.

Ive got a decent roach but not that much up high (see the avatar) so the "flick" is pretty easy. I can see that getting more tricky the longer the fat head.

What do you guys do in these conditions?

You needn't have a topping lift at all; even lacking a conventional vang. As, assuming that the mast will take the loads, the simple (theoretically) solution is to "invert the vang". So that the section which would normally attach to the mast underneath of the boom, does so, instead, above the boom, on both sides of the mast.

Although, as I said, the mast needs to be strong enough to handle such loads. Since it's not a configuration which commonly designed for, in many vessels, when a Naval Architect first starts to pen a design... Let alone retrofitting a boat for such.
But... sleeving masts (internally), & or adding doublers (externally), may be viable options. That, or adding more laminate, if it's a CF mast.
Both of which are done fairly commonly on racing boats. Though, much less now, than a decade or 3 ago.

Also, if you go with said variety of unconventional vang. You'd likely need to do a bit of "re-wiring", regarding the running rigging in that neighborhood.

Plan B:
Is KISS. And it's to simply beef up your lazy jacks enough so that the windward one acts as topping lift. Assuming that you have/can make, attachment points for the lazy jacks, which are strong enough to bear such loads.
Likely this is doable, sans too much trouble or expense. Plus, then, you can also dispense with the conventional topping lift entirely, as a 'free' perk.

Plan C:
Do something vang wise, akin to was done on the 12m's. In that you mount a hemispherical (or semi-curved) track to the deck (cabin house roof). And attach a vertical vang (hydraulic or mechanical), with an integral return force/system, to a car on the cabin house track, as well as to the boom's underside.

Needs be, even adding a short section of track to the boom's underside, & a car to same. If you require some ability for the vang to be moveable on the boom. So as to compensate for a non hemispherical track on the deck/cabin house roof.

The caveat to this idea being, that you'd need to consult with your boat's designer, in order to get the nod, regarding the cabin house taking those kinds of loads. And, or, for his specs delineating how much to beef up the house, where, & how.

Plan D:
While this would be far from cheap. You could go to a cored carbon fiber laminate, type boom. So that it's weight would be much, much less than a conventional one.
Meaning; you have an inner composite shell (to the boom), laminated to a core, & then an outer composite shell on top of that. Just as is done in hulls & decks.
They're very light, & very stiff; in addition to also making your wallet "very, very light", as well

PS: There are also many other unconventional vang configurations out there. Most can be found on various classes of racing dinghies... although they'd need a bit of scaling up of course.

But even Bruce Schwab's Ocean Planet went though a few different variations of unconventional vangs (& booms). Even with her freestanding mast. So finding a solution's possible.

[tomfl]

Originally Posted by Barra

So what do you guys do when your boom is flopping around in light air with some adverse wave action given most cats dont have a vang?


SNIP

Traveler and preventer.