Square top main on water ballast?

rgranger · Aug 30, 2023

I'd do it and strategically locate the first reef point so that the total area with one reef is slightly less than the normal main sail. That would allow you to set a sail that has comperable surface area with LESS area up high.

SkookumZac · Aug 30, 2023

I have one on order

I discussed square top vs roachy main with my sailmaker. He suggested that the square top will spill excess wind automatically, allowing you to pull the vang down tight and manage heeling with the mainsheet. I'm also adding a cunningham and switching to loose foot, which will give better options for tuning sail shape.

Also, just having a new sail with proper shape will help a lot with heeling vs an old baggy sail.

-Z

shemandr · Aug 30, 2023

Aerodynamically a high aspect ratio sail is more efficient - i.e. more lift less drag. You can see the trend of sails evolving to be more square topped. I don't think the the concept is in question. The limit is in construction mechanics.
I think the spitfire wing is considered the most efficient shape for a foil, at least at sub jet speeds. The more a sail, centerboard, or rudder can look like that wing the better.
Regarding the spilling of wind, that is a characteristic of fractional rigs. The top of the mast will bend to leeward opening the the top of the sail to spill wind. I'm not aware if that depowering is directly related to the amount of roach built into the main.
But I'm a fan of fractional rigs.

rgranger · Aug 30, 2023

SkookumZac said:
Also, just having a new sail with proper shape will help a lot with heeling vs an old baggy sail.

-Z

This was definitely true on my Hunter 26 after I got a new Maine she sell a lot flatter

David in Sandusky · Aug 31, 2023

Shemandr is right. A high aspect sail is always more efficient. So I'd go ahead with the new mainsail if the improved performance is worth the price to you.

Having a "tender" boat is a different issue. Every sailboat has an optimum heel angle. For our h27, that angle is 15 degrees. Going beyond that angle of heel reduces efficiency because of increased hull drag, and loss of effective sail area exposed to the wind. (Despite the thrill some experience from excessive heeling.) Reefing is the solution if heeling is excessive. You will actually go faster with a reefed sail and optimal heeling than with a full main and excessive heeling. I would go with your sailmaker's recommendation for reef points. Reefing to match your current sail area is interesting, but irrelevant with the new sail shape. You reef to keep your boat at the optimal heel, given your sail shape and the wind.

A last thought about "tender." It often refers to a boat that initially heels quickly as the wind increases. In some designs, initially tender boats may become "stiffer" as they approach optimum heeling. Over time, you will learn how your boat responds beyond its initial tender response.

rgranger · Aug 31, 2023

David in Sandusky said:
A last thought about "tender." It often refers to a boat that initially heels quickly as the wind increases.

This is a great point, especially for a water ballast boat. When the boat is flat, there is zero contribution to righting moment from the ballast. MAXIMUM TENDERNESS! You only get a net moment when the boat starts to heel. This is the design trade-off made when choosing a larger-ish trailer sailboat.

If you feel your boat remains tender even after heeling, I would check the gasket on the ballast tank valve to make sure you are not leaking water from your tank while heeled.

patbratton · Sep 12, 2023

The square headed trend seems to be catching on. However, to me it gives the appearance of a gaff headed main with a truncated topsail. Time will tell.

Crazy Dave Condon · Sep 13, 2023

Regardless, experience with any Sail configuration ,max heel for Hunter water ballast sailboats is 12-14 degrees. Achievable thru sail control

SkookumZac · Oct 23, 2023

I'm happy to report that my square top sail has arrived and it is spectacular.

-Z

shemandr · Oct 23, 2023

Who built the sail? I can’t make out that insignia.
Looks good to me. Nice tri-radial design, reinforced attachment points and a very nice draft forward shape.

rgranger · Oct 23, 2023

Two sets of reef points.... very nice!

caverun · Oct 23, 2023

shemandr said:
Who built the sail? I can’t make out that insignia.
Looks good to me. Nice tri-radial design, reinforced attachment points and a very nice draft forward shape.

Looks like Evolution Sails, very nice sail!
Evolution Racing, Cruising, Membrane, One Design and Superyacht Sails. (evolutionsails.com)

SkookumZac · Oct 23, 2023

I am fortunate to have an Evolution loft right here in Charleston. They did the measurements and design and even showed me how to install the battens. The top "Gaff" batten has to be removed to put the boom cover on! Even still it looks like I'm going to need a bigger cover.

I spent some time rearranging things in the boom to rig the 2nd reef but didn't need it in the strong breeze yesterday. The top twists off as advertised and the full length battens keep the luff from flapping when the sheet is eased. I was worried the extra sail area would increase weather helm but the tiller was nicely balanced.

Altogether a happy customer

-Z

rgranger · Oct 23, 2023

SkookumZac said:
….it looks like I'm going to need a bigger cover.
-Z

shemandr · Nov 1, 2023

Regarding price a tri radial is going to cost more.
For me I would have the sail fitted to the boat with the correct mast rake - which is, in my opinion the most important rig tuning parameter.
I wouldn’t change the rig dimensions to allow for a dodger. It’s a sailboat and needs to be able to sail optimally.

shemandr · Nov 2, 2023

For many boats that are performance oriented and/or have class associations the forestay length is often a published number. That makes it easy. It is determined through the experience of the members.
If not, sailmakers can provide an approximate number. Lacking that you could start at 3 degrees of rake determined by the plumb bob method. In the end it’s about the helm balance. When sailing in 10 -12 knots the helm should be about 3 degrees off of center. Much more than that and the rudder drag is slowing you down. Less than that you will not adequately feel the helm and will find it hard to not wander.

pgandw · Nov 14, 2023

massnspace said:
Rake: How does one even know what the “correct” mast rake is? The rigging is not original, so who’s to say how a previous owner(s) set the stays, and thus the rake?

And even if one could confirm the original rake angle, how would it be possible to accurately set it? How can one even get the boat “level” to start with?

On the ODay/Stuart Mariner 19, the rake is measured by (securely!) taping a tape measure to the main halyard and taking the end to the top. Then measure the distance from mast head to transom on center. Adjust rake with the forestay. I also measure to the chain plates on each side to verify mast is centered. Recommended mast rake starting point on Mariner (3/4 rig with uppers and lowers aft of the mast) is measurement of 28ft or just under. Back stay is set to minimum tension but not loose. The racers have started incorporating split back stay with purchase to center back stay and to allow adjustment while underway. The measurement scheme eliminates need to get boat level fore and aft.

Without the original rig data or a known backstay length, I would use measure where you are at, then go for a sail. Excessive weather helm may indicate too much rake, lee helm indicates mast has too little rake. This assumes sails are in good shape, and boat would have fairly neutral helm under the sailing conditions.

Fred W
Stuart Mariner 19 #4133 Sweet P
Yeopim Creek, Albemarle Sound, NC