All good ideas. The one thing I would add about the bear off ? it helps if
you start out sailing a bit loose (footing). Then bear off only about 45-70
degrees (ie to just past beam reach) and let the boat accelerate even more.
Once the boat is up to scary speed, then bear off the rest of the way ? or
alternatively two-sail reach at 110 -120 degrees off the wind. The
two-stage bearoff has three salubrious (positive) effects:
1) it allows the boat to accelerate before the full downwind load is
placed in the bow thus reducing the force pushing the bow down
2) a faster boat generates more lifting power out of the hull so it
gives the bow shape more power to lift out of the water (buoyancy during the
initial stage 1 bear off and planning lift during the latter bear off)
3) it reduces the loads on the rudder ? by reducing the weather helm
force of a buried lee-bow, you reduce the force on the rudder, plus since
you are bearing off a bit less, you don?t crank the rudder as hard over
which in turn reduces the loads.
The real gotcha is the puffs you were facing. It sounds like you had 20kn
steady with 15-20+kn gusts (that would explain the 20 degree shifts ?
velocity shifts). Hammering gusts like these place maximum loads on
EVERYTHING especially the mast. In fact I?d take the time before the next
sail to check everything on the mast ?just in case?..
Another thought on the rib. Bram what do you thin of inlaying a ¼? or 3/8?
carbon kite batten into the foam on both sides? This isn?t quite the full
cross sectional rib, but it provides the surface stiffness.
_____
From: BDally6107@xxxxxxx [mailto:BDally6107@xxxxxxx]
Sent: Monday, August 20, 2007 8:58 AM
To: mwhite@xxxxxxxxxxxxx; swiftsolo@xxxxxxxxxxxx
Subject: Re: rudder blues
I
Mark,
Let me preface all of this by saying that it is always easy to give good
advice while sitting in the calm behind a computer. You are correct about
this being a discussion that needs to happen.
Let's start with the bear away. It's probably good that you failed since the
round up in 40 knots when you had to turn back upwind would likely have
thrown you head fist into the mast at the spreaders. When sailing alone in
strong winds we really need to be wearing a helmet.
The load on your rudder is really high when the bow goes down and the boat
heals to leeward in a bear away. The obvious things are to heal the boat
to weather and get as far back as possible before initiating the bear away.
The prudent thing would have been to go head to wind and to have taken down
the main. This is where the friction of grip tape in the tiller extensions
really comes into play. It will act like auto pilot for that short time
when you need both hands for something else (like taking down the main).
As far as the rudder goes there are a couple of things. First, I think you
use a spartite gasket? If so, there is little that could be done other than
using more material in your rudder of by installing a rib in the rudder at
the thickest point. The rib could be built out of eight layers of hybrid
and installed by running the foam blank through a table saw to make a single
cut from two inches below the top down 18 inches. Be sure to cut a deep V
in the end of the rib to eliminate point loading at the bottom end (you'll
be cutting the blank off at the top when it's done down to the rib). Before
inserting the rib into the saw cut, rough up the outer edges to make it look
like a wool sweater. The rib should be cut about 1/8" (3mm) narrower than
the blank and installed centered with a few small dabs of epoxy / silica.
After the epoxy goes off, use a utility blade to cut a small V in the foam
about 3mm wide and 3mm deep on each side of the rib (both sides of the
blank).
At this point you'll lay up the rudder like normal except you'll use thick
epoxy/silica to fill the V on both sides just before laying up the rudder
(while it's still wet).
I'll lay one up this way next week and post a PDF.
I hope this helps Mark.
Bram
n a message dated 8/20/2007 7:22:32 A.M. Pacific Daylight Time,
mwhite@xxxxxxxxxxxxx writes:
To all,
I made the mistake of misjudging the wind speed yesterday. I left the shore
where it was fairly well protected from the wind, thinking the wind was
blowing around 20. I knew it was in deep dodo as soon as I hit the wind
about 200 yds off shore. The wind was not steady, it was like rolling, or
twisting constantly. My heading was constantly shifting 20 degrees or so,
just trying to maintain a straight course. The battens kept popping from
left to right, while I bounced in and out of the water. The only thing I
could think to do was to bear off, run down wind, gibe, and come back to my
starting point on the beach. I tried 3 or 4 times to bear off but the boat
refused to do so. Every time I tried, the bow went down to the gunwale and
would start to heel over. The last attempt I tried as fast as possible.
The boat heeled, and I heard a breaking sound, like wood tearing. I thought
I had broken the transom, or the transom bar. After capsizing I couldn't
find any damage. Luckily someone was there and helped me get the mail down
while capsized. Thinking all was well, I started heading for shore under
the jib, and noticed the boat steered very sloppy, that was when I noticed
what broke. The rudder was kicked off to starboard. It lasted about 3/4 of
a minute, and broke off behind the boat. Needless to say the boat without a
rudder just spins in circles. The ride out lasted about 1 minute, the tow
back in lasted about 20 minutes. I had left my wind gauge at home and the
one at the marina was broken, but the folks that run the place thought the
wind was blowing 35 gusting to 40, I didn't think it was that high, but I
really don't know.
So it appears that the rudder was the weak link. I still can't imagine the
rudder could have had enough pressure on it to break. The question is do
you make the rudder stronger, then possibly breaking the next weaker link,
or let the rudder be the weak link? Obviously the best solution is to stay
on the shore on days like this, but you can still be caught in big wind
while out on the water. I think now it would be a good idea to have a hand
held VHF in my PDF. If I had been farther out, or out of sight of the
marina and this had happened, and no one right there to assist, it would
have been ugly. I believe I would have been ok, but the boat would have
eventually wound up on the rocks. I now have a new found respect for the
wind, and the need for a new rudder blank.
I'm not sure what else I could have done, but it would be good to know what
to do if found in this situation in the future. In hind sight, I think I
could have tacked, and maybe tried to stall the boat and drift back to
shore, but if it wouldn't stall, and drift, I would have headed towards the
floating piers. I just knew I didn't want to get any further away from
shore. I don't think I could have gotten the main down and kept the boat
up-right. In a one man boat the options seem limited.
I think this is something that should be discussed, here or on the website,
since anyone could end up in a situation similar to this.
Mark
_____
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