Genoa Size

A looong time ago, I learned to sail on my grandfather's Alberg 35. One thing I remember is the really large genoa, with the sheet running through the spinnaker car near the transom, and the foot hugging the rail all the way. I'm told it was a 200% sail. In a strong breeze, us grand-kids would lay-out on the sail, heeled over, our feet in green water, but our faces dry.

Yet on every bareboat I've chartered in the last 5 years, the genoa ranges from 110 to 135%, and since they all are roller-furl, the foot is very high. The track for the car usually stops even with the forward end of the cockpit. On many of these boats, the fully battened main over-powers these "hankerchiefs". I realize that charter companies worry about overpowering the boats, but seriously...

Now I assume that technology and techniques have changed in the past 30 years...

What are the design guideline for determining the "optimal" size for a genoa? Is there any benefit to having the foot tight to the rail (like on the Americas Cup boats)?

-Laz

 

Prada Genoa

Laz:

I believe that you are correct about the genoa meeting the rail.

On the 2002 America's Cup yacht 'Prada', the foresail had a "skirt" that extended BELOW the clew of the jib. I assumed that this was UNMEASURED area and that it helped to gasket the sail to the foredeck. I did not read anything on the web about this feature so I am guessing about its function.

Do you suppose that the deck would act as a foil-end to eliminate spillage around the foot of the sail?

 

"Do you suppose that the deck would act as a foil-end to eliminate spillage around the foot of the sail?"

That exactly what its there for. In windsurfing it was called "closing the slot" when the foot of the sail was on the deck you could get a bit more power out of it.

In cruising yachts a deck sweeping genopa is not really practical but you can drop a skirt off the boom to give the same effect on the main - The Dashews talk about it here http://www.setsail.com/c_central/techtalk/endplating.html

Having the foot tight to the rail is for windward ability - the closer to the center line - the closer to the wind you can get before the genoa luffs. Hence the modern genoas that sheet inside the rail. - and so have to be smaller.

I dont remember where I read it but I seem to remember anything over 135% is wasted - unless there is some racing rule to be taken advantage of.

Cheers

Paul

 

Thanks Paul!

That link is very interesting. I was actually considering raising the clew of the genoa to be level with the lifeline, but keeping the foot parallel to the lifeline/deck all the way aft. Now having read that article, it seems that if the foot isn't sealed completely, it's not as effective. More to ponder...

Do you have a Rhino hull file that I could play with?

-Laz

 

sure, sorry, you mentioned it in another thread, my hull is 50ft not 37 but happy to send you a copy to play with - how fast is your connection?

 

for cruising leave it high - otherwise you get excess sail wear, pick up every other wave on a beat, you cant see a thing, and anything/one on the foredeck gets whiped off!

Cheers!

Paul

 

Thanks all around. My main goal is to balance the genoa with the main to get a near neutral helm. Chartered a Hunter once with a main with a big roach and a 110% jib. Had one nice broad reach in 15kts where I had to wrestle the wheel the entire time, I was exhausted and frustrated within 30 minutes. Balance was achieved with the main at the first reef!

I'm on a cable modem (fast!), but AOL limits incoming files to 2Megs. Let me know if that is an issue. Also, ZIPped is good. I also asked (sort of) ErikG for his 33' hull. So we'll see.

-Laz

 

hmm the full lot resides around 15 Mb I'll see what I can do, just the hull should be fairly smal

 

OK Laz I got the hint!



Well my design is a wee bit diferent but I can certainly get you "a" hull design to work with. Also I'm not quite ready to get my hull scrutinized by others just yet...

What size hull do you need?

Erik

 

I'm figuring 36' is about right, but I'm flexible. It's really just to play with for now, until I get really serious.

Thanks!

-Laz

 

Hi: The last owner of my newport 27 cross a lot of miles cutting the mast 3 feet for eliminate heel problem and of course the main. He prefer to use a reefed main and a 180% Genoa with roller furling. He toll in that way its more easy to control the boat in rought seas and the boat was incredible balance. He toll me he dont lost preformance on windward because he have a lot of power in the Genoa that the boat never stop in that way with a good speed he can point better.

 

First off, the Alberg 35 was drawn during the era of the CCA Rule that encouraged large overlapping genoas. 170's were common and larger didn't pay much of a rating penalty. Likewise, the IOR, the CCA's successor, assumed a 150% genoa and no credit was given for anything smaller. Since you were being charged for the size, might as well have it.

PHRF and the newer measurement rules (IACC excepted) give credit for smaller overlaps and many boats are designed specifically to accommodate this with the largest jib being as small as a 100%. These designs generally compensate by carrying a large main.

IACC boats are pure racers, of course. They're relatively narrow forward, have no lifelines and crews and gear specifically meant to handle large jibs. And keep in mind that in their most prominent role, they only have to avoid hitting one other boat. This specialized purpose allows use of sails we wouldn't tolerate on a cruising boat or even a typical offshore racer.

If the boat is designed to sail well with a smaller genoa or just a jib, it won't benefit much from adding overlap to the Alberg proportions you remember. It will also be easier to tack shorthanded and work well with roller furling. And, as has been pointed out, the absence of a foot skirt allows you to see under the sail from the helm.