Smaller Mainsail - impact on performance

TonyMills

TonyMills

Well-Known Member
Joined
29 Dec 2001
Messages
119
Location
Western Australia
Visit site
I have 30' 1/2 tonner which has a somewhat tired mainsail. It has been repaired several times and stretched to b....ry.

I cant afford a new one at this time but I have been offered a reasonable priced second hand sail.

The s/hand sail is 20cm longer in the luff and 20cm shorter at the foot. The sailmaked handling it will recut the sail so that the luff will fit the mast, but obviously nothing can be done about the shorter foot measurement.

I'd appreciate any thoughts as to whether using a smaller footed main will materially affect performance of the boat. I am hoping for an improvement in performance because the s/hand sail is in much better condition than my old one.

The self furling 110% jib is also tired, but that will have to wait a while longer!

Regards
TonyM
 
An expert I am not, but I would have thought that the difference over all wouldn't make that much difference? if the "new" sail sets better than your old one, ie. better shape, the chances are that it will perform a bit better, I have always thought that it is the shape of the slot between the main and the headsail that is the major governing factor, but like I said, I aint no expert.

Be interesting to see what others have to say on this one?
 
Slightly smaller area will almost certainly be ofset by the better performance in sail shape - esp if its a masthead rig where more power comes from your headsail.
 
Is the 'new' sail to be loose footed? I would think,in my limited personal experience of playing around with these things-that that would be more significant and allow more adjustment than the simple loss of 20cm at the leech. Flatter and higher aspect ratio may theoretically mean reefing a bit later and better upwind.Be interesting to see if you feel the bow tending to fall off (the wind) at all..
 
No expert, but I would expect a small reduction in weather helm. If this turns out to be a problem, it could probably be ofset at least partially by raking the mast aft a little.

Otherwise, as others suggest, I would expect the improved shape to more than outweigh the loss of area.
 
Re: Reduced weather helm or....

Does new main have more or less roach than old main? If more, the loss of length on the foot will be more or less cancelled out.
If less, the improved cut will offset impaired performance from knackered main anyway. If weather helm turns into neutral, or lee, helm then rake the mast aft a bit more.
 
For my money I'd go for the jib every time.

Upwind the jib is the powerhouse, the slot is the most important to get right, with the leach of the main holding her up to wind.
Downwind it's all about sail area so get the kite up. Sail shape and condition is not important on a run just area.

Where you might lose in is on the reaches but remember that the top third of both sails do nigh on 70% of the work so as long as you don't loose too much roach area and you control it well with the kicker you should be OK.

I agree about the rake if your getting lee helm but make sure you have good leach tension with the kicker before you make that call.

It also depends on your keel design and where you sheet the boom to as well, I am assuming in a 1/2 tonner you are centerlining the boom?

Hope it helps.

/forums/images/graemlins/smile.gif
 
For my opinion the old sails will have good performance off the wind and in light airs. A soon as you you beating into a stronger wind the shortcomings of older sails will become obvious.
You will get more heeling and poorer pointing into the wind.
The "new" sail will be a lot better under these conditions. Although as already stated the jib is the one that matters more. You need to ensure that the jib if being used partly rolled is set up for the best performance. ie correct sheeting point and sufficient luff and sheet tension. (I prefer a dedicated non rolling jib for performance).

As for the sail size. every sail size is a compromise so you will be slightly better off with more wind with the smaller main.
I would n't expect any noticeable improvement in weather helm. My guess is that any real weather helm is caused by too much heel (overpowering) good luck olewill
 
Thanks Mac..
I have a boom sheet track and move it upwind or down depending on conditions. The track is forward of the hatch and has very good tension capability. She has a shaped fin keel with the rudder on a thin skeg not unlike an S&S34. Above the waterline she has a similar shape to an Elizebethan 30 though a little sleaker. She is a masthead sloop.

Regards
TonyM
 
You must log in or register to reply here.

Share this page

Top