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Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation > Heavy Air Mainsail Trim
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Topic Review (Newest First)
06-09-2001 07:44 AM
JeffH
Heavy Air Mainsail Trim

I certainly agree with your last couple sentences but what you seem to be ignoring is the vang. Once the boom gets past the point where the mainsheet''s position of the traveller results in a predominantly downward force, the boomvang should be used to control twist. At that point you are ''vang sheeting'' which is very effective in blading out a sail. Going back and reading this string at least some of the posters have Hunters without backtays and so the option of increased backstay tension is not offered to them, but on boats with fractional rigs and masthead boats with flexible spars, backstay tension and mast bend are one of the most useful controls that you have in heavy air. On boats that have more primative rigs about all that you can do is to just tension outhaul, and halyards, drop your traveler and reef early.

Jeff

Jeff
06-08-2001 11:19 AM
Headman
Heavy Air Mainsail Trim

I went back to the original message to review the parameters that were set for this question.
If you are above a beam and below a beat, then my guess is that the boom is going to be outside of the sweep of the traveler. Therefore, the effort of the mainsheet is going to pull the boom towards the centerline of the boat and induce twist to the sail. If I remember the sailing characteristics of most Hunters I have sailed, they have a tendency to weather helm. Depowering the headsail while at the same time adding twist to the main is going to unbalance the helm towards weather helm.
If the sailing conditions are as you describe, the boom end will most likely not be outside of the beam. If it strikes the water at that point, well, your day has gotten exciting hasn''t it?
Now with the wind on the beam at 20-25knts, I believe there will be some kind of sea running. In this beam to situation, there is bound to be some rocking and rolling going on. I have one scar on my forehead from a boom, and while it does add character, one is sufficient. When I am cruising, I am way to laid-back to want to worry about ducking a swinging boom.
Anyway, I feel that the great attraction of sailing is the test of each sailor''s ability to solve his/her problems. There are many right answers: Whatever works for you at the time you need it to work- that is the answer.
Tom S.
06-08-2001 10:46 AM
EscapeArtist
Heavy Air Mainsail Trim

Re: "release the topping lift"

No kidding. One day I was slogging along to windward and looking up puzzled at my sloppy, open leech--even though the main was sheeted in hard.

Sure enough, the topping lift was up tight.

Now I watch for it, and I see boats on the water with an overtight topping lift all the time. I''m shopping for a solid vang right now, it''s the only way to go with these huge roaches.
06-08-2001 10:32 AM
JeffH
Heavy Air Mainsail Trim

Tightening the backstay is standard proceedure when in heavy air because tightening the backstay does a couple things at once. When you tighten the backstay you tension the forestay. This flattens and depowers the jib while opening up the leech area up high. This moves the apparent center of effort forward and downward. Tightening the backtstay on a modern righ also induces a little mast bend which blades out the mainsail and opens the leech up high moving the mainsail apparent center of effort forward and downward. Combined this reduces heeling and weather helm.

I really question the purpose of applying the preventers when beating or reaching in a blow. Proper use of the vang and properly dropping the traveller in gusts really should be all that is necessary to stabilize the miansail. Applying the preventor really puts the boom and mast at risk should the end of boom dip in the water.

Jeff
06-08-2001 08:06 AM
Headman
Heavy Air Mainsail Trim

Escape Artist,
Most of the advice you have received is correct. However, I would disagree with tightening the backstay. That would only move the center of effort aft, thereby increasing weather helm.
The one additional sail shaping tool you might want to consider is a preventer line from the toe rail forward of the boom attachment up to the boom. By triangulating the boom between the sheet and the preventer you can flatten and stabalize the sail just at the point of luffing. Any puffs that over power you get immediately dumped from the sail yet the boom stays stable. I rig my preventer lines ( I rig port and starboard lines if I am having to tack in through heavy seas) back to the cockpit through snatch blocks attached to strongly backed pad-eyes. It is a simple matter to release the preventer before beginning a tack, and with practice, you will become proficient in cleating off the preventer before trimming the main at just the right place so that when the main is trimmed,the preventer is tight.
A preventer line is a life saver if you are having to jibe your way home. I single-handed a lot, and by controlling the boom with both the mainsheet and preventer, jibing was a nonevent.
Don''t forget to release the topping lift.
Tom S.
06-07-2001 07:07 PM
EscapeArtist
Heavy Air Mainsail Trim

Exactly the source of my confusion.

I''ve often heard/read to flatten the sails in heavy air. That means traveller down, leech tight, backstay tight (if you have one--I don''t).

I''ve also heard/read to spill air by twisting the main. To me, that means a looser leech, traveller high and sheet eased.

I''m getting it sorted out now. In my original scenario I''m reefed, so Bob''s advice is correct. But spilling air out of the upper leech is available as a depowering tactic short of reefing.

Thanks to you both. By the way, "Escape Artist" is a Hunter 336.

Paul
06-07-2001 05:04 PM
cditzen
Heavy Air Mainsail Trim

Hm, I think there might be two different scenarios in heavy air: overpowered, and not overpowered. In the overpowered case (more than ~6degrees of weather helm amongst other things), I think twisting the main off (actually the same for the jib if heeling too much) is a pretty good idea. In general, to depower, I do the following:
- outhaul on (flattens lower part of the sail. Be careful not to overdo it, or it tightens the leech too much, thereby untwisting the top and overpowering you again)
- backstay on (flattens esp. the middle of the sail. Also helps to twist the top off)
- cunningham on (opens the leech!, as well as flattens the luff and brings the draft forward)

If these don''t do it, you can move the traveller to windward, and allow the boom to ride up a bit to twist the top off even more. If you are still overpowered after all of this, you should definitely reef. If you can''t/don''t want to due to tactics, it''s most often faster to just ease the main and stop fighting the helm than to be overpowered, even if you backwind the main a bit.

Hope this helps.....Chris
06-07-2001 03:06 PM
hamiam
Heavy Air Mainsail Trim

In heavy air you want to reduce area thru single, double, or even triple reefs, a flat sail shape, and no twist in the sail. To achieve this you want to tighten the outhaul, tighten the boom vang to remove the twist, tension the main halyard, tension the backstay and drop the traveller to the leeward side of the boat. Many of us trim the sail and keep the traveller amidships. In this way you can depower by dropping the traveller to the leeward side during a puff and then bring it back to the center after the puff. You might want to tell us what kind of boat you have..

06-07-2001 12:30 PM
EscapeArtist
Heavy Air Mainsail Trim

I remain confused about how to trim the main in heavy air. I''m talking gross trim here, not little tugs on the outhaul or the cunningham.

I am a cruiser, not a racer. I want to get where I''m going without dumping the contents of the galley lockers on the cabin floor, or losing my crew/wife in a mutiny.

Let''s say I''m properly reefed in 20-25 knots, sailing above a beam reach. How should the sheet and traveller be set up? Why? What should I look for in the shape of the sail?

Thanks!

Paul

 
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