Association Forum - big race this weekend

Assn Members Area · Join

Home.

Association Forum

Ships Store

Cruising

Racing

Technical Tips

Photo Gallery - New

Boat Search - Updated

Manuals & Brochures

Swap Meet

Links

Officer Flag Line & Staff

Bylaws & Constitution

Members Area

Join the Association

Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.

Association Forum

Username:	Password:
Save Password
Forgot your Password?

All Forums

Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

big race this weekend - advanced trim question

New Topic

Topic Locked

Printer Friendly

Author

Topic

JimB517
Past Commodore

Member Avatar

USA
3285 Posts

Initially Posted - 07/29/2009 : 13:35:09

Hi, Fin Keel Standard rig. Rig tensioned according to the Crawford/Milby method with Loos gage. Adjustable backstay. New full batten loose footed Ulman main. Old but good condition 155 deck sweeper dacron, 145 mylar/laminate plus many other jibs. Outhaul, cunningham, vang, all race controls are available (18 lines lead to the cockpit). I have an inner jib car track right along the windows on deck and I can "skirt" the jib inside the lifelines very, very flat for max pointing. Balanced rudder. Boat super well balanced, almost unnoticable weather helm. Let go of the tiller and she'll keep right on trucking on most tacks (for a minute or two). Also my mast is raked and pre-bend farther aft than any boat on the dock.

San Diego summer conditions are usually light wind, 6 to 10 knots. I am fully powered up and begining to think about depowering the sails with the 155 up in 12 knots. Waves usually 2 to 3 feet at 8 to 10 seconds (light chop, enough to pound the boat).

Ever since I got the loose footed full batten Ulman main, it seems the main outpoints the jib.

If I sheet in the jib and sail to the luff telltails streaming for max pointing, then flatten the main, travel boom to centerline for max pointing the main leech telltales stall, especially the top. To get all the main telltales flowing I have to let go the mainsheet and get some significant twist in the main.

Most (bigger) boats in the racing fleet outpoint me somewhat.

Suggestions???

(1) Its just wind sheer, the wind is stronger up high and you need some twist to retain attached flow up higher

(2) main significantly newer than the jib nothing much you can do

(3) move jib cars forward, flatten jib, less twist will match less twist, flatter main

(4) more backstay, less jib sag, flatter main in the mid sections.

(5) more vang, outhaul, cunningham, super flatten main (if I do this it seems to really depower the boat)

(6) harden jib halyard, move jib draft forward

(7) rig jib barberhauler (I've done this, seems to depower the boat)

Other ideas???

Indiscipline 1978 FK SR #398

Edited by - on

Derek Crawford
Master Marine Consultant

Members Avatar

USA
3321 Posts

Response Posted - 07/29/2009 : 13:51:47

Jim, I've noticed that if my jib (155%) is flat that we slow down.
I always make the trimmer keep a small draft in it (i have no experience of inside-the-lifelines trimming).
One of the first things I was taught about the main was that optimum speed is obtained by flying telltales 1, 3 & 4 and stalling 2 (counting from the top). This still seems to hold true with my new loose-footed full batten main. Only off the wind do I fly all 4.
I will often foot off a very little to pick up an extra fraction of a knot which helps me correct out over a J24 and a J80 which both outpoint me.
In light air (up to about 7 knots) I keep the backstay off, the halyards not rock tight, the cunningham off and the outhaul loosened.
If the wind increases then, in order, we add outhaul, cunningham, halyards and last the backstay.
Sure hope that this helps! Go get 'em!

Edited by - on

Dave Bristle
Master Marine Consultant

Members Avatar

Djibouti
10005 Posts

Response Posted - 07/29/2009 : 18:36:45

I was told by a big-boat racer (with his own custom Peterson) that 3-5 degrees of weather helm is faster than a neutral helm. We've debated here why that might be... My theory is that it creates a slight leeward angle of attack for the keel, which creates more pressure on its windward side, keeping the rig more upright to generate more power. But I was told here that I was wrong...

...although not about the "faster" part.

Edited by - on

Steve Milby
Past Commodore

Members Avatar

USA
5902 Posts

Response Posted - 07/30/2009 : 08:57:29

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by JimB517
Ever since I got the loose footed full batten Ulman main, it seems the main outpoints the jib.<hr height="1" noshade id="quote"></blockquote id="quote"> The mainsail should outpoint the jib. Remember when you were first learning to sail, the instructor told you to first trim the jib for your closehauled course, and then trim the mainsail by sheeting it in tight and then letting it out until the luff of the sail just begins to lift. The jib on a C25 is the power sail, but the mainsail helps it point. The wind applies pressure on the mainsail aft of the keel's CLR, and that pressure pushes the stern to leeward, which, in turn, causes the bow to point to windward. The wind applies pressure on the jib forward of the keel's CLR, and that pressure counteracts the pressure on the mainsail, and pulls the bow to leeward. The shape of the hull and keel and rudder cause the forces on the sails to be released so that the boat slips forward in the water. Thus, you shouldn't trim each sail separately, for maximum power. You have to begin by establishing the proper relationship between the two sails, and then adjust their shape, while maintaining that relationship, to maximize their power.

Like Derek, I have no experience with trimming to an inside genoa track, but I have often wondered how it could significantly increase the C25's windward ability. When sailing closehauled (for best overall speed and pointing ability), the leech of my 155 was never trimmed closer to the spreader tip than about 6" (OK maybe 5"). If I trimmed it closer, the boat might have pointed a skosh higher, but the boat began to lose speed drastically. If the 155 was trimmed too tight, it changed the relationship between it and the mainsail, i.e., the mainsail was backwinded. When the mainsail is backwinded, it's losing power. That's why I have difficulty understanding how an inside genoa track can help a C25 significantly. It enables you to trim the leech of the genoa even closer to the spreader, but I can already trim it so close that the boat loses power, and I can't understand how it would help the boat to be able to trim it even closer.

It's conceivable that the inside genoa track might help the boat point better in very light air, when you would ordinarily ease the sheets a bit for more power, or, it might help the boat point in strong winds, when you're flying a jib smaller than 100%, that can be trimmed closer than the spreader tip without touching it, and that doesn't overlap the mainsail and can't backwind it.

My best guess is that you're using the inside genoa track in conditions that aren't well-suited to it, and over-trimming the genoa in relation to the mainsail. I would only use the inside genoa track with the 155 in very light air or with a small jib in very strong winds.

I suggest you use the outer track in the next race (when you use the 155), and trim the leech to about 5-7 inches from the spreader (you'll usually want to be closer to 7" than to 5", to power through any chop), and then trim the mainsail accordingly, and see if your overall speed and pointing improve.

The C25 was designed to sail at about a 45 deg angle to the wind. It's very tempting to think you can change that significantly by installing an inside genoa track, but I don't think it's that simple. The positioning of the track alters the relationship of the sails to each other.

Edited by - on

JimB517
Past Commodore

Members Avatar

USA
3285 Posts

Response Posted - 07/30/2009 : 16:18:35

Well, thanks for the tips. As to sheeting inside the lifelines, the jib does not get any closer to the spreaders. What it does is improve pointing about 5 degrees, greatly flatten the jib, and most importantly decrease the sheeting angle.

I'll be most likely be going with the borrowed asym to the island, gybe around, then be hard on the wind all the way back with the 155 up and sheeted tight, main eased off and twisted a little. For sure over trimming and over flattening robs a lot of power.

I won't know how the redistribution of weight helps or hinders until I see how we do against the other race boats.

Final prep tonight (Thursday) leaving from work tomorrow directly to the boat. Rig lines, eat, sleep, and get up early for the 3 hour delivery to the start line.

Edited by - on

Topic

New Topic

Topic Locked

Printer Friendly

Jump To:

Association Forum

Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.