Visit our Popular Forums

arsenelupiga · 16-05-2021, 15:45

Quote:

Originally Posted by 44'cruisingcat

More sail area is likely to produce more speed. This will have the effect of widening the gap between AWA and TWA. You may not be doing 90' tacks any more. However your VMG could improve.

it is bit of expensive shot in the dark.

When I upgraded to square top and gained 4.5m2 improvement was clearly noted in light winds. But this was 4.5m2 extra sail at the top of mast which is most efficient.

Adding ~13m2 to increase genoa (without prodder extension) will total 109 m2 upwind area, vs current 96m2, ie 13.5% improvement.

Now we sail at 4 kn in 10 kn true at 31, then one HOPES to sail at 5 kn in 10 kn true at 31 which means extra 0.5 kn VMG. So expecting 25% increase in boat speed, which appears optimistic.

Looks lots of trouble for little benefit....

Extending prodder for say 0.5m will add extra ~5m2 which is not that great gain.

I do not know enough about sails in light winds to make any meaningfull guess but at present i do not believe $$$ effort and extra work (swapping sails) would yield enough gain.

44'cruisingcat · 16-05-2021, 16:25

Quote:

Originally Posted by arsenelupiga

it is bit of expensive shot in the dark.

When I upgraded to square top and gained 4.5m2 improvement was clearly noted in light winds. But this was 4.5m2 extra sail at the top of mast which is most efficient.

Adding ~13m2 to increase genoa (without prodder extension) will total 109 m2 upwind area, vs current 96m2, ie 13.5% improvement.

Now we sail at 4 kn in 10 kn true at 31, then one HOPES to sail at 5 kn in 10 kn true at 31 which means extra 0.5 kn VMG. So expecting 25% increase in boat speed, which appears optimistic.

Looks lots of trouble for little benefit....

Extending prodder for say 0.5m will add extra ~5m2 which is not that great gain.

I do not know enough about sails in light winds to make any meaningfull guess but at present i do not believe $$$ effort and extra work (swapping sails) would yield enough gain.

Fair enough. Same kind of reasoning has prevented me from getting a screecher. It'd be nice to have, but they're expensive sails and the endless line furlers are dear too.

A 2nd hand assymetric does some of the things a screecher would do, for far less.

arsenelupiga · 16-05-2021, 16:59

Quote:

Originally Posted by 44'cruisingcat

Fair enough. Same kind of reasoning has prevented me from getting a screecher. It'd be nice to have, but they're expensive sails and the endless line furlers are dear too.

A 2nd hand assymetric does some of the things a screecher would do, for far less.

i have carbon gennaker and failed to see any benefits of that as it is crap upwind - bad shape. Much cheaper classic material one would produce same benefits, like Taskers code C. Lately in stronger winds (>15kn app) screecher cannot be any faster than jib. Not sure whether there is some sort of gennaker deterioration or my trimming skills of jib improved. One cant trim gennaker much.

fxykty · 16-05-2021, 23:52

Quote:

Originally Posted by arsenelupiga

i have carbon gennaker and failed to see any benefits of that as it is crap upwind - bad shape. Much cheaper classic material one would produce same benefits, like Taskers code C. Lately in stronger winds (>15kn app) screecher cannot be any faster than jib. Not sure whether there is some sort of gennaker deterioration or my trimming skills of jib improved. One cant trim gennaker much.

You have an obsession with tight AWA, which makes sense for your type of boat. That is because your boat - relatively heavy and high drag for its length - cannot go enough faster despite extra horsepower to gain the benefits of speed. So don’t bother looking for extra speed as you won’t go fast enough to make the higher AWA pay off.

Do note that gennakers are typically designed for 50-80* AWA, maybe that’s your problem? Screechers are designed for 40-70* AWA. But it takes a cat that can go fast enough that it can still make good VMG despite wider TWAs of 50-55*.

arsenelupiga · 19-05-2021, 16:45

Quote:

Originally Posted by fxykty

You have an obsession with tight AWA, which makes sense for your type of boat. That is because your boat - relatively heavy and high drag for its length - cannot go enough faster despite extra horsepower to gain the benefits of speed. So don’t bother looking for extra speed as you won’t go fast enough to make the higher AWA pay off.

Do note that gennakers are typically designed for 50-80* AWA, maybe that’s your problem? Screechers are designed for 40-70* AWA. But it takes a cat that can go fast enough that it can still make good VMG despite wider TWAs of 50-55*.

we can still go 7-8 kn upwind, heavy or not in 20 kn true. But at 50 app this makes 3 kn VMG. However at 30 apparent this is 6 kn VMG! That is where is the juice

And yes we can do 8kn at 30 app. Probably down to 27 app actually which adds to 6.35 VMG. That is not slow in any language.

Regarding our carbon gennaker we do now 3.1kn VMG in 10 kn true sailing inside shrouds. This sail was not designed for inside shrouds so shape is bad. Cutting size around 7m2 will allow me to elegantly sail inside shrouds and swap inside/outside easily. With good shape will sure improve 3.1 VMG that can't be achieved with white sails. So, yeah whatever the name of sail, it can be used for efficient upwind work in relatively smooth seas that appear more often than I originally thought. If i only knew if gennaker (?) designed to sail from jib leads would be better upwind?!?! Sure better sheeting angle, but cut away another 15m2 or so of sail leaving around 50m2.

malbert73 · 19-05-2021, 17:56

6.35 VMG upwind? Really? Remember 27 AWA is not your true angle

arsenelupiga · 19-05-2021, 19:10

Quote:

Originally Posted by malbert73

6.35 VMG upwind? Really? Remember 27 AWA is not your true angle

we would not sail at this sustainably as it is with full sail but can be done and have done it to prove

fxykty · 19-05-2021, 22:47

Quote:

Originally Posted by arsenelupiga

we would not sail at this sustainably as it is with full sail but can be done and have done it to prove

No leeway? No wind waves, so close to shore with an offshore breeze? Current assisted?

I have to call BS on this - maybe you had a brief moment where your instruments showed 8.0 knots STW and 30* AWA but I don’t believe you could hold those numbers and 0* leeway to achieve that VMG. Sorry, but not believable for a fat hulled 40 foot cat.

And you’re using full sails - that’s a hell of a lot of load - but if that follows your reefing guide then OK.

arsenelupiga · 19-05-2021, 23:01

Quote:

Originally Posted by fxykty

No leeway? No wind waves, so close to shore with an offshore breeze? Current assisted?

I have to call BS on this - maybe you had a brief moment where your instruments showed 8.0 knots STW and 30* AWA but I don’t believe you could hold those numbers and 0* leeway to achieve that VMG. Sorry, but not believable for a fat hulled 40 foot cat.

And you’re using full sails - that’s a hell of a lot of load - but if that follows your reefing guide then OK.

no idea about leeway but my guess would be very little. In relatively calm waters of course. Reefing should happen at 20 apparent but we do go to 25 apparent by easing main bit by bit again in relatively calm waters. So, yes, was pushing it and not sustainable except in emergency.

Your experience around NZ may be different but I realized situations with relatively calm seas are more common than I originally expected based on extrapolation from Sydney and surroundings where i started. So calm water performance is now more important for us.

double u · 20-05-2021, 00:51

"...leeway but my guess would be very little..."

seeing as the L400 is low-windage, rounded-edges, sleek...
(another "my-boat-is-best"-post...)

arsenelupiga · 20-05-2021, 01:04

Quote:

Originally Posted by double u

"...leeway but my guess would be very little..."

seeing as the L400 is low-windage, rounded-edges, sleek...
(another "my-boat-is-best"-post...)

2 to 3 degrees. One measurement at 6-8 kn true, the other at 10-20 kn. I tried best to cancel current.

I know what you mean, and i thought the same but this are measured angles so i have high confidence that leeway is definitely less than 5 degrees. Until hulls stay glued to the sea. Our boat is bit lighter than average L400, else standard.

double u · 20-05-2021, 01:08

Quote:

Originally Posted by arsenelupiga

2 to 3 degrees. One measurement at 6-8 kn true, the other at 10-20 kn. I tried best to cancel current.

I know what you mean, and i thought the same but this are measured angles so i have high confidence that leeway is definitely less than 5 degrees. Until hulls stay glued to the sea. Our boat is bit lighter than average L400, else standard.

hmmm...? This would mean a mono-performance-cruiser has more leeway than a L400?...

double u · 20-05-2021, 01:10

...& of course this depends on the way it is "measured"...
(I as a layman would halve the difference between the compass-tacking angle & the over-ground tacking angle, but what do I know...)

arsenelupiga · 20-05-2021, 01:18

Quote:

Originally Posted by double u

...& of course this depends on the way it is "measured"...
(I as a layman would halve the difference between the compass-tacking angle & the over-ground tacking angle, but what do I know...)

here is one 43 true on autopilot and the track shows 91 average tack in 6-8 kn. this was in lake with changing winds but managed to get this portion. Also you can see my AP does not like tacking in windwane mode so that is why balooned tacks.