Dealing with the genoa

[mikedefieslife]

Curious, when on a say a starboard tack, sailing on a beam or broad reach. Is there anything that can be done to prevent the genoa from collapsing and filling again as the boat rolls starboard and port over the waves?

Seems to put a lot of stress on the rigging.

EDIT: I should add 'on a catamaran' not so much of and issue on a mono since it would be healed.

[Herreshoff]

It's just a case of not enough wind, and thus not enough pressure on the sails to keep the boat heeled enough, and therefor not enough forward momentum to resist rolling as the swell passes under. Not much you can do about that. You need more speed so you might need to motor sail through light patches like that, or, if you want to stick to sailing solutions, then get more sail up and try to gain as much forward momentum as possible. You should find that any forward momentum gained should help your boat resist rolling and should keep the sails from collapsing.

If it's on a broad reach then tightening everything up a bit should also help.

I get the same thing offshore with my MPS if winds are too light. I use to mess about getting tossed from side to side, now I just motor sail through it.

[UNCIVILIZED]

Just prior to the wave striking you, fall off about 15 degrees, & then once the wave has passed, come back up to course. So that you wind up driving "S's".
That, or you can overtrim the jib. Permanantly, meaning while those conditions persist, or overtrim it just prior to the boat passing through/over a wave.

As to stress on the rigging, is yours properly tuned? Since there shouldn't be any looseness in any of your shrouds, even the leeward ones, especially in light air. But not even when going upwind in 20kts true.
Metal doesn't like suffering through (millions) of bending cycles, even if it is "flexible" wire rope, which comprises shrouds & stays. And that's what happens to it if your rigging's too loosely tuned.

[thinwater]

Are you pulling the lead forward and down with a barberhauler or similar? The sheet should be coming from near the midships cleat when the apparent wind is on the beam. This will give better shape and stabilize the sail.

This is a time when the beam of a cat should be put to use.

("Faster Cruising for the Coastal Sailor," in my bookstore, http://sail-delmarva.blogspot.com/2017/01/the-book-store.html, covers this sort of thing, with a certain bias towards catamarans.)

[basssears]

Poling it out can help to a certain extent, although doesn't completely eliminate the flogging / flapping.

[mikedefieslife]

Well today it was 10 knts apparent on the beam and then slightly aft of the beam. Really struggled to get any decent speed, perhaps around 3-3.5knts, with the genoa flapping around on every roll.

As soon was the wind picked up to a steady 11/12knts then I was fine, moving along at 5knts while also towing the dinghy, which probably costs half a knot.

The genoa is maybe 150%, so perhaps not so easy to fill in lighter airs.

[guyrj33]

you might try heading up to create apparent wind and build up speed, then when you have your speed built up and the apparent wind has moved forward steer back to your desired course.

[StuM]

Originally Posted by mikedefieslife

Well today it was 10 knts apparent on the beam and then slightly aft of the beam. Really struggled to get any decent speed, perhaps around 3-3.5knts, with the genoa flapping around on every roll.

As soon was the wind picked up to a steady 11/12knts then I was fine, moving along at 5knts while also towing the dinghy, which probably costs half a knot.

The genoa is maybe 150%, so perhaps not so easy to fill in lighter airs.

What make/model of cat? Those figure sound very low.

[UNCIVILIZED]

I concur with StuM on the point about speed. But I'm also wondering what your telltales are doing? Are you perhaps getting an excessive amount of wind spilling out of the top of the jib?

[thinwater]

Something is very wrong with the figures IMO. If there is 10 knot apparent on the beam, the true wind should be at 120 degrees off the bow and about 15 knots. Under those conditions...

a. The wind would be holding the sail full, even with the rolling.
b. Boat speed would be at least 7 knots in a cat that wears a genoa.

At 11-12 knots app aft of the beam, the true wind is in the high teens. You couldn't keep the boat from doing 6 knots. Something does not add up.

[mikedefieslife]

Boat is a Prout Snowgoose, of course is a slow cat.

In 14 knots on the beam she will be going 7+ knots, but in lighter winds she struggles.

I think we've been here before on the speed on of this cat, as the previous owner had a post about it. It has a skinny furling main (practically useless, since the original main on these is tiny anyway), and a massive genoa despite being a cutter rig.

I don't think I have ever got all the telltales flowing nicely.