West Coast
Well-known member
question raised last week, to which I had to confess I could not answer!Bigger than 100%, becomes a genoa?
When is the forward sail a genoa, and when is it a jib?
- Thread starter West Coast
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question raised last week, to which I had to confess I could not answer!Bigger than 100%, becomes a genoa?
duncan99210
Well-known member
A genoa is a type of jib which exceeds 100% of the fore triangle in size.
nimbusgb
Active member
In other words if it extends back past the mast it's a genoa.
VicS
Well-known member
Bigger than 100%, becomes a genoa?
From The Oxford Companion to Ships and the Sea
a large foresail used in racing and cruising yachts. Its features are (a) its size, considerably larger than a standard jib and often larger than the mainsail, and (b) its shape, with the clew extended much farther aft than in an ordinary jib, overlapping the mainsail by an appreciable amount, its foot often parallel with the deck sheer. In effect, it combines jib and staysail in a large single sail. As well as transferring the main driving power of a yacht's sails to the fore-triangle, it also, by the sheeting of its clew well aft of the mast, increases the speed of the airflow over the luff of the mainsail. This increases the partial vacuum there which helps to pull the yacht forward.
Javelin
Well-known member
Hmm, this is incorrect information, in truth it does the opposite but I guess that's not for this thread.....
silver-fox
Active member
A little explanation would go a long way, otherwise you are just expressing opinion as fact!
Leighb
Well-known member
I believe, but expect I may be corrected , that it was originally conceived as a way of adding "unmeasured" area to the sail plan of racing yachts. Back then it was assumed that foresails were no longer in the foot than the distance from tack to mast.
There may of course be alternative explanations.
, that it was originally conceived as a way of adding "unmeasured" area to the sail plan of racing yachts. Back then it was assumed that foresails were no longer in the foot than the distance from tack to mast.There may of course be alternative explanations.
charles_reed
Active member
Except that sailmakers' to confuse us poor sailors, regularly mark my 100%, deck-hugger, blade-jib (or solent) as a "Genoa #3".
Keen_Ed
Active member
Invented by Raimondo Panario in the six metre class in 1926 in Genoa. Hence the name.
Javelin
Well-known member
A little explanation would go a long way, otherwise you are just expressing opinion as fact!
A short answer for a complicated question.
The airflow between the leeward mainsail luff and the windward side of the genoa (the slot) is artificially slowed down and NOT as the "The Oxford Companion to Ships and the Sea" suggests, speeded up.
This is a common misconception.
However this slowing of the airflow on the windward side of the genoa increases the differential compared with the flow on the leeward side of the genoa which in turn does increase the partial vacuum there which helps to pull the yacht forward
In very short - the slot effect decreases the efficiency of the mainsail but significantly increases the efficiency of the Genoa which on balance makes the boat sail faster than having no slot effect.
Apologies to the OP
Dockhead
Active member
A genoa jib is, however, but only one type of jib which overlaps the mast. The other common type is the so-called yankee jib, which has a high clew. Unlike the genoa jib, whose foot is generally parallel to the deck. The yankee jib is commonly seen on cutters, as the high clew is easier to tack around a cutter's inner forestay. But the yankee jib is also easier to trim, as the ideal sheeting angle varies less. If you are a cutter with a staysail - so goes the logic, anyway -- you can use that to sweep the air at deck level, so you don't mind the lost sail area at deck level.
charles_reed
Active member
Now you're really complicating a simple question. Who was asking about yankees?
D
Deleted member 36384
Guest
I have read the books, accepted the explanations, repeated them ad nauseam and even argued the case. However, after various threads on the forum it became obvious that this position was not tenable. The man responsible for both researching how sails work and challenging perceived wisdom is Arvel Gentry and his articles can be found here: http://web.archive.org/web/20130824192227/http://www.arvelgentry.com/ His stuff, as I now know, is legendary and backed up with testing and analysis, the original papers were written for aerodynamics professionals but he also reduced the articles for the wider sailing community to read and understand; worth downloading and reading.
Lakesailor
New member
I just call it a headsail. Bound to be right.
Twister_Ken
Well-known member
A pedant speaks. I maintain there is no such thing as a partial vacuum (as there is no such thing as a partial virgin - well, not in that sense of partial, anyway). A vacuum either is or isn't. Your partial vacuum is simply an area of reduced pressure.
Hydrozoan
Well-known member
A pedant speaks ... A vacuum either is or isn't. Your partial vacuum is simply an area of reduced pressure.
In your terms, there is no such thing as a vacuum, other than as a construct in the minds of physicists. All 'vacuums' are 'partial vacuums', in the common sense of reduced pressure relative to atmospheric: even deep space has the odd few hydrogen atoms per cubic metre, we're told. But must dash - Mrs H is pointing meaningfully at the reduced-pressure cleaner
.West Coast
Well-known member
Sounds good to me :encouragement:
30boat
N/A
Is that why many times when hard to windward the mainsail has to luff a bit in order for the the genoa to work well?'ve noticed that if the sails are trimmed so that the main is perfectly full the efficinecy is lower.
savageseadog
Well-known member
Or foresail
mjcoon
Well-known member
A pedant speaks. I maintain there is no such thing as a partial vacuum (as there is no such thing as a partial virgin - well, not in that sense of partial, anyway). A vacuum either is or isn't. Your partial vacuum is simply an area of reduced pressure.
So how do you define a vacuum, then? When my research apparatus, back in the 1960s, included a "hard" vacuum (mechanical pump followed by diffusion pump) I thought I was creating a vacuum, but nowhere as good as outer space, solar wind notwithstanding...
Mike.
