Is my mainsail really helping?

Nov 17, 2009
20
Catalina C-310 Falmouth
Recently I've been singlehanding my Catalina 310 alot and I've noticed that in similar wind conditions on a beat or a close reach I can attain the same (or nearly the same) boat speed with just the 150 Genny as I can get using both the genny and the main. Also, the boat seems to point just as well with just the genny and of course there is a lot less heel. I just don't seem to gain anything upwind by using the mainsail. Both sails were new last year. Any thoughts on whats happening?
 
Nov 8, 2010
11,385
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
You boat has a masthead rig, and with a 150% is VERY headsail driven. What you are experiencing is not that uncommon.

You could probably crank out a couple of 10ths more if you make sure your boom is on the centerline of the boat (traveler to windward) and you are sheeted on hard. That at least makes sure your main is working in what the genoa gives it. The main has to come up because it is sailing in a relative header created by the genoa.
 
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Nov 26, 2012
1,557
Hunter 34 Berkeley
Your boat, like mine is very much jib driven. With good wind and close hauled you can reach hull speed with just the jib and with a 150 you can really get there. It will not be as fast in lighter wind and certainly not on a beam or broad reach. Hull speed is hull speed so with big wind you can get there with just the headsail
 
Jul 14, 2015
840
Catalina 30 Stillhouse Hollow Marina
When I sail with the Genoa only, I get good speed. The difference comes when Tacking. Boat comes to and up to speed better with the main up. Genoa only when I tack with auto-pilot it wants to keep pushing around too far. With main up it gets on it's feet much better in a tack.
 

druid

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Apr 22, 2009
837
Ontario 32 Pender Harbour
I had a similar experience yesterday: with my 120% jib, I was making 4.5-5 knots upwind with jib alone. When I raised the main with a single reef (had passengers that didn't like to heel...), I found the boat went even SLOWER (with more heel). But the sail-shape was awful - I couldn't get it to look even close to right. Shook out the reef and got better sail shape and a BIT more speed (closer to 5+).
I've ordered a new main from North Sails - I'm really hoping it will help upwind performance!

druid
 
Mar 2, 2008
406
Cal 25 mk II T-Bird Marina, West Vancouver
I got a new 115% fulling Genoa and a new mainsail (3 reefs) from North Sails last fall. Made a huge improvement in pointing ability, heel and speed. My only complaint is that the main sail is so stiff that it was difficult to reef and difficult to put on the sail cover. One often does not know how bad the old sails are until you get new ones.
 

druid

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Apr 22, 2009
837
Ontario 32 Pender Harbour
Yes, Jalepeno, that's my (only) complaint about my new 120% jib - VERY hard to fit in the bag! But the new main will have full battens, which I find makes flaking and folding onto the boom much easier.

druid
 
Mar 26, 2011
2,967
Corsair F-24 MK I Deale, MD
I suggest you look at VMG to windward too. Many boats "seem" to point just as well with genoa only, but because they are sailing with lee helm (they will turn away if the helm is released) the rudder is actually pulling them to leeward instead of providing lift.

The main can be more important for balance than drive.

And it will make real difference off the wind.
 
May 17, 2004
2,039
Other Catalina 30 Tucson, AZ
Come on guys -- when God created sail boats he designed them to work with both a mainsail & a jib. It's easy to learn how to make both of them work efficiently together. Personally, I hate to see a sail boat being powered by only the jib.
 
May 24, 2004
6,841
CC 30 South Florida
In cruising, for a masthead rig, it is said that the large Genoa powers the boat while the main sail provides stability. There will be conditions where you would not want to sail under Genoa alone. For cruisers speed is not the only criteria, helm balance and comfort of movement are very desirable. On the other hand the newer design boats are powered by large roach mains and working jibs.
 
Feb 26, 2004
22,017
Catalina 34 224 Maple Bay, BC, Canada
Come on guys -- when God created sail boats he designed them to work with both a mainsail & a jib. It's easy to learn how to make both of them work efficiently together. Personally, I hate to see a sail boat being powered by only the jib.
Personally, I do it a LOT. Poor man's main sail furling system. :):):)
 
Nov 8, 2010
11,385
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
While indeed marconi rigged sloops are designed to fly two sails; there are often times when one is actually better or more convenient. Stu mentions the ease of leaving main under the cover. In big breeze fractional boats are very well mannered and a pleasure to sail with just the jib out.
 
Mar 26, 2011
2,967
Corsair F-24 MK I Deale, MD
Another reason I dislike sailing with jib-only in a big breeze (the only time it would really make sense) is furling. I can't stand the jib flogging required and the load on the furling gear (you will have to winch it if it is really blowing) stands my hair on end. with a main I can blanket. Lowering that main, at least on my boat, is independent of windspeed. It also means that the sheet loads on both sails are half, so sail trimming is easier. No strain for me or the boat.

Of course, in a big blow, for me, 2 sails are much faster. No hull speed limit! 2 reefed sails means double digits with the boat on autopilot and holding a nice conversation. Big smiles.
 
Nov 13, 2013
646
Catalina 34 Tacoma
On my C34 with a 150% jib I sail jib only almost exclusively when single handed. Soooo much easier than messing with sail cover, and cranking the main up. I'll get all 70% to 100% of speed that I would with the main up depending on wind speed. Sailing for me is also about using the least personal energy to achieve maximum boat speed.
 
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Jul 7, 2004
8,059
Hunter 30T Cheney, KS
On my C34 with a 150% jib I sail jib only almost exclusively when single handed. Soooo much easier than messing with sail cover, and cranking the main up. I'll get all 70% to 100% of speed that I would with the main up depending on wind speed. Sailing for me is also about using the least personal energy to achieve maximum boat speed.
And you call yourself Head Sail ;)
My concern with sailing a huge genny alone is visibility. That sounds like more continuous work than prepping a mainsail.
My Hunter is a fractional rig with a huge main and smaller genny. I prefer to use the main when I'm short handed.
 
Oct 3, 2014
249
Hunter 33.5 & Lake City, MN
When we started the sailing season (our first) this summer we started by having an instructor on our boat for 3 days of on-the-water training for my wife and two boys.

On the third day, with wind at 18 kts and gusts to 25kts, I was a bit nervous going out. He suggested we fly only the jib and to my surprise, the boat handled wonderfully. We had a blast sailing that day. It would never have occurred to me to sail with just the jib in a wind that strong but now we know it's another option for us and it's led to us experimenting with different sail plans in different conditions to see what works best for us and our boat.
 
May 20, 2016
2,995
Catalina 36 MK1 94 Everett, WA
Personally, I do it a LOT. Poor man's main sail furling system. :):):)
same here - If I'm just out for a relaxing evening with the admiral on Possession Sound it is so much easier to go Jib alone. going down wind stinks - but I really haven't figured out down wind on my new to me boat.
 
Nov 13, 2013
646
Catalina 34 Tacoma
And you call yourself Head Sail ;)
My concern with sailing a huge genny alone is visibility. That sounds like more continuous work than prepping a mainsail.
My Hunter is a fractional rig with a huge main and smaller genny. I prefer to use the main when I'm short handed.
Visibility is a issue but easily managed by paying attention and that's less energy than hoisting and flaking the main. I'm in Puget Sound so usually ample time to see in all directions if day sailing. Now if I had in boom or in mast furling, I'd probably think otherwise.
 

druid

.
Apr 22, 2009
837
Ontario 32 Pender Harbour
I suggest you look at VMG to windward too. Many boats "seem" to point just as well with genoa only, but because they are sailing with lee helm (they will turn away if the helm is released) the rudder is actually pulling them to leeward instead of providing lift.

The main can be more important for balance than drive.

And it will make real difference off the wind.
Actually Not True. I still get weather-helm sailing jib-only. There is a tendancy to go off the wind when the boat's not moving, but as soon as it gets going, there's enough weather-helm to do the "poor-man's upwind autopilot" with jib alone.

And downwind it's great: you don't need to worry about the main blanketing the headsail.

druid