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Rounding up (weather helm)

Posted: Mon May 05, 2008 2:08 am
by RickJ
Last time I was out I got the full effect of the X's weather helm. :(

I'd been making good progress close-hauled to a 10 kt wind with one reef in, then the wind picked up to 12-13 kts. This started pushing the heel angle to 30+ deg. at which point I felt the boat was behaving like a (very large) dinghy. :|

Beyond a certain angle it just looses all steering, and from a side-on viewpoint turns hard towards the keel - i.e. into wind. It seems to me this is the effect of centerboard drag together with loss of steering because the rudders are no longer vertical in the water, just what you get in a dinghy if you can't hold it flat enough.

Ideally I should have put another reef in, but as I was nearly home it wasn't worth the effort so I just carried on in what must have looked like an interesting attempt to emulate a snake. :D

I know some aspects of weather helm can be a case of sail balance, but I don't think that's the case here, this felt entirely like hull dynamics. Some boats use cambered rudders to keep the in-water rudder more vertical at high heel angles - just musing on whether anyone's done that mod to a Mac (and if so does it work). :?:

I'm curious as to how you guys who report heeling at 40+ deg. have kept the boat in a straight line. Or is there a difference between X & M here?

Any ideas on dealing with the problem, or is it like the old joke: "Doctor, I keep rounding up when I lean over" - "Then don't lean over". :D

Cheers, Rick

Posted: Mon May 05, 2008 3:32 am
by Moe
Rick,
I don't think the weather helm is the X's hull dynamics as much as it is having the center of drive outboard to leeward. I've intentionally oversheeted and chugged the 26X across the lake at 45º heel without rounding up. That was probably possible because there's not much forward drive left at that point.

I think the doctor analogy is a good one, and that reefing the X to keep heel reasonable is the answer.

Degrees

Posted: Mon May 05, 2008 11:06 am
by pokerrick1
Moe;

Where is that degree circle (as in 45 degrees) on your keyboard - - - I can't find it on mine :| You probably have a professional engineer's keyboard, huh - - - not like this one I got at Wal Mart :(

Rick :) :macm:

Posted: Mon May 05, 2008 11:31 am
by Kelly Hanson East
Google ascii 0176 iirc to see how you can add symbols to your reportoire

Posted: Mon May 05, 2008 12:36 pm
by Bawgy
Press and hit ALT while hitting 167 . º

Posted: Mon May 05, 2008 1:54 pm
by Moe
I use a Mac. Here are the most common symbols I use:

option zero º (degree)
option 2 ™ (trademark)
option Shift 2 € (euro)
option # £ (pound)
option $ ¢ (cent)
option 8 • (large dot)
option Shift 9 · (small dot)
option Shift - — (double dash)
option = ≠ (not equal)
option Shift + ± (plus or minus)
option r ® (registered)
option p π (pi)
option g © (copyright)
option z Ω (omega/ohm)
option x ≈ (approximately equal)
option m µ (micro)
option < ≤ (less than or equal to)
option > ≥ (greater than or equal to)
option / ÷ (divided by)

Not sure how these will look viewed on a PC.

--
Moe

Posted: Mon May 05, 2008 4:04 pm
by Alex
Bawgy wrote:Press and hit ALT while hitting 167 . º
Hm, sorry not clear for me. Try again....

Posted: Mon May 05, 2008 4:23 pm
by BKAFER1
press the alt key and hold it.
while holding the key type in 167
and this appears.
º

ascii codes were used quite often when I started playing with computers in 1982 on my zx80

now practice and see what else you can find
I like alt 255 for passwords.

ooh sorry this is a sailing site not a computer site.

Were planning a Tortugas trip for next year. We intend to stay at least 7 days
and planning 4 extra for weather.

Posted: Mon May 05, 2008 4:24 pm
by Moe
Hold down the Alt key while typing the number on the numeric keypad on the right side of the keyboard. The numbers above the letters won't do it.

Posted: Mon May 05, 2008 4:48 pm
by Snow Goose
Try decreasing mast rake. It worked for me. :macx:

Posted: Mon May 05, 2008 5:15 pm
by RickJ
Moe wrote:Hold down the Alt key while typing the number on the numeric keypad on the right side of the keyboard. The numbers above the letters won't do it.
If you can't remember the numbers etc., open Start->Programs->Accessories->System Tools->Character Map. Select the character you want, copy to clipboard, and paste where you need it.

Back to the thread ... (:wink:)
Snow goose wrote:Try decreasing mast rake. It worked for me.
I noticed when I first put the boat on the water that the mast seemed excessively raked backwards. I reduced the rake as far as it would go - the forestay turnbuckle is now all the way in - but it's possibly still more raked than it should be. I think I'd need a shortened forestay to reduce it further, and I'd also have to cut the furler down a bit. Either that or raise the forestay hound on the mast.

I think I'll live with it for this season, maybe something to do next winter. :)

To pose one of my earlier questions again - has anyone done anything with cambered rudders, is it even relevant?

Cheers, Rick

Posted: Mon May 05, 2008 5:29 pm
by Moe
The forestay on our 26X was set as short as the turnbuckle would allow. However, when I did that, the backstay was about 1-1/2" too short to reconnect. That's when we got a couple of blocks and made it adjustable. The shroud adjusters were also pretty close to their ends, such that each adjustment tighter was a pretty big jump. Maybe our forestay was shorter than the average.

Posted: Mon May 05, 2008 5:41 pm
by Don T
Hello,
I had the same quandry with my 95 Mac. I shortened the forstay and trimmed the luff channel on the CDI RF. Still plenty of room for the sail. My shroud adjusters are extended to the point where they are no longer "fine" adjustments. It really helped with rounding although I left it with some weather helm. I can neutralize it by raising the centerboard just a smidge to move the center of resistance aft.

Posted: Mon May 05, 2008 8:38 pm
by johnnyonspot
I agree, check mast rake. Should only be a degree or two of aft rake. I am curious about one thing, though, is it common for the power sailors to reef as early as ten knots? And to be heeled over at 30 degrees in 12 knots seems odd as well, at least to me. I don't even have reefing ability with my Mac 25, so its a bit academic, but I would not think of reefing in 10-12 knots. Heck, that's right where it starts to get really fun, from there on up to about 18 knots. Perhaps the power sailors are more tender, I don't know.

Posted: Mon May 05, 2008 9:47 pm
by delevi
10 kts wind shouldn't require a reef and shouldn't produce more than about 10-15 degrees heel upwind with full main & jib and roughly 20 degrees with full main and genoa. Most likely your sails were oversheeted. Were you using jib or genoa? What point of sail? Are you sure the wind wasn't higher than 10 kts? Reducing mast rake will help a lot, but proper sail trim is the first remedy. Not to sound like a smartass, but this can happen to any of us. Did you fill the ballast tank?

Fair winds,
Leon