The Mast as a Problem: a Legend

[CarlosK2]

Fabio Fossati (-2015), may he rest in peace, Wind Tunnel of the Polytechnic University of Milan, micro pressure sensors

At AWA 20, we can observe a slight increase in pressure in the MainSail low-pressure area due to the Mast effect, a minor detail: note that, as we know, sharp leading edges on the jib or genoa are not ideal

And look at the mainsail at AWA 35

The Mast as a problem is an old myth

 

[CarlosK2]

Mikko Brummer - Wikipedia https://en.wikipedia.org/wiki/Mikko_Brummer

Mikko Brummer has repeatedly pointed out the positive effect of the mast on this forum, and once, in a CFD study of a case, he gave a figure: the mast produced 6% of the sailboat's forward thrust

Intrigued, I did some simple calculations, and in the case studied, the mast produced 4% of the sailboat's forward thrust.

The mast (along with the mainsail and the headsail) becomes a sail that isn't very efficient, but a sail nonetheless

AWA: 30°
AWS: 16.87 (TWS @ 10 m h: 15 knots)

Lift: 67 Newtons
Drag: 20.8 Newtons

Drive Force: 15.69 Newtons
Lateral Force: 67.5 Newtons

The boat travels at 5 knots, propelled by a force of approximately 400 Newtons, which is not shown in the drawing

 

[skaraborgcraft]

What if its a box-spar? Effective down wind for sure.
Areofoil shape and wingmast sections i can understand being some drive.

 

[CarlosK2]

In summary: for 30-35 AWA, a rig consisting of one mast and two sails is excellent.

And if the Mainsail is worthy of the name and quite large, then it's a rig that's also suitable for downwind sailing.

 

[CarlosK2]

The mast as a supposed problem is a clear case of self-sabotage and making a mountain out of a molehill

+ a better shape
+ a realistic AWA for most yachts; we're not talking about skimming across ice
+ a boom and a MainSail
+ the downwash of the staysail

and the supposed problem dissolves like a sugar cube in a cup of hot tea

 

[CarlosK2]

"a box-spar"

Exactly

Four Sitka Spruce planks, epoxy resin, and three coats of polyurethane from two cans, along with Dyneema* shrouds and galvanized turnbuckles

Simple, reliable, and mechanically clean, without the hassle and nightmare of a rig based on a very expensive Aluminum mast

*: There are two possibilities:

Plan A) pure or
Plan B) with a Dyneema core and polyester shirt

Plan B seems like a magnificent solution to me: the Dyneema soul well protected from the sun and friction

 

[CarlosK2]

Actually, the main criticism of the single-mast, double-sail rig is: what's the point of having a mainsail for those snail-yachts that carry their entire house on their backs if they're not going to hoist it?

Plenty of snail-yachts have sailed around the world without ever raising their mainsails

Why on earth would they want such a mechanically complex rig, prone to failures, mechanical scares, and crevice corrosion of the stainless steel

Crevice corrosion - Wikipedia https://en.wikipedia.org/wiki/Crevice_corrosion

 

[CarlosK2]

A mast made of four Sitka Spruce planks, well waterproofed with epoxy resin, the resin well protected from the sun with polyurethane.

Completely enclosed, without the superstition of drilling holes in the mast to hide the halyards

the mast is sacred; drilling holes in it is barbaric, and then letting water in—are we crazy or what?

Damage the mast for 4 fuxxx Newtons of Aerodynamic Drag ... Upwind

... and then install large solar panels facing the wind, a zodiac at the stern, and a large awning ... this yachting world tends toward madness

 

[CarlosK2]

In Europe ...

TOUCHWOOD — Marine https://sitkaspruce.nl/touchwood/marine

The wood has to be brought from far away; but in the USA, having Alaska, and even more so in Canada, an aluminum mast is ridiculous

 

[CarlosK2]

Freed

Freed from the (silly) Aerodynamic fear of the Mast...

we can opt for a mast 2 cm large and it turns out to be lighter, the same weight, or slightly heavier than its aluminum equivalent, and much much more resistant

From a simple version 1.0, a simple rectangle (12 cm x 10 cm) of four Sitka Spruce planks, to a possible version 3.0 with a hollow Paulownia nose, there are many possible variations

 

[skaraborgcraft]

My last big spar, 3 layers, hollow, aluminium chafe in the top 2m.

Its lost a further 3kg in weight while being stored over the past years.

 

[Doug Halsey]

This thread seems like a bunch of random postings about masts.

What exactly is the "problem" that you're trying to refute?