Posted by Nick Wigen (216.26.63.29) on May 08, 2000 at 08:06:45:
We've had some discussion on this forum about Moonspun's problems. Their loss of the rudder under normal sailing conditions gives me some worry. It sounds like they had some fairly heavy going on their trip to Hawaii but most of the trip was not too bad. In any event, no boat should ever lose it's rudder unless it hits something very dense very hard.
Moonspun's logs are pretty sort on details but it sounds like they lost the entire rudder (it broke off) but only after a period of partial failure. They don't say if the upper portion of the stock stayed in the tube, etc. I also gather that there must have been some hull damage since the logs make mention of a leak in the skeg and evidently Jim has been trying to stop a slow leak with epoxy while they are in the water. I've tried to send an e-mail to them to ask for more information but it bounced back as non-deliverable.
I doubt that there is a serious design flaw in our boats since there are something over 700 hulls out for up to 11 years but the 2 reported failures do give me pause. The deeper, elliptical rudder retrofitted to Moonspun would result in higher overhung stresses on the stock and bearing systems compared to the original design. If the stock is the same as for the shoal draft rudder it would follow that failures would first occur on deep draft rudders if the operational histories are similar. How this translates to the hull damage and leak on Moonspun is unknown.
I crawled into the aft compartment this last weekend to look things over and have also looked at the drawing that is on the brochure showing the general arrangement of the rudder structure. I'm not a naval architect but am a Mechanical Engineer so have good familiarity with the stresses and machine elements involved. The bearing arrangement looks basically sound in general layout. The cantalever loads on the rudder are carried mainly by the bearing surface at the bottom end of the rudder galley (FG tube bonded to hull) and the bearing at the top end of the stock. The packing gland will contribute a small amount of support but I would expect that the tube, even with the gussets, will flex very slightly as the rudder stock flexes. Please keep in mind that the amount of flex I'm talking about is very small. Any load added to a beam results in some displacement. The important part of structural design is keeping the amount of flex within safe limits.
Again, this is mostly speculation but I expect that Moonspun's failure began with the rudder stock. The log reports some period of jerky operation before everything when to pieces. It looks like the main rudder stock consists of 2 tubes one inside the other. I wonder if there wasn't some problem with an initial failure of one of the tubes followed a few hours later with total failure.
I've written to Catalina but haven't received a response. I doubt that I will. I think it would be very good to get more details from Moonspun. Does anyone know how to contact them?
Nick WigenPosted by Jim Goodrich (Moonspun) (152.163.213.176) on May 23, 2000 at 10:17:18:
Cindi and I just splashed Moonspun, after having her in the boat yard in Kona (Big Island) for a week. The new rudder is installed and the skeg has been
repaired. Catalina, and specifically, Gerry Douglas, have been very helpful in getting us seaworthy again (Thanks Gerry).
Here's what we know:
1. The rudder broke at the weld inside the rudder sleeve (about 6 inches above the main body of the rudder). The sea/wind conditions during the crossing were
fairly normal (nothing too strenuous), with winds generally between 12 and 18 knots, and seas on the beam and quarter between 3 and 8 feet.
2. We recovered the broken rudder (it floats) and shipped it back to Catalina for their analysis.
3. We don't know yet why the rudder broke and we're going to let Catalina give the definitive answer after Gerry has a chance to analyze the rudder
post.
4. The leak in the skeg was caused when the rudder, no longer attached to the quadrant, swung hard against the skeg's trailing edges, breaking the thin
fiberglass there. Also, the seating ring are at the bottom of the skeg (where the rudder enters the boat) was broken as the rudder slid down and tilted back as
it left the boat. All this was relatively easy to fix once the boat was out of the water.
5. Someone on this page asked about rudder stops. We have an aluminum bracket that acts as a stop for the quadrant, so it doesn't have a chance to swing
too far and touch the skeg's trailing edges. The boat this person saw out of the water may have had a quadrant failure or a broken stop that allowed the
rudder to overswing.
If anyone wants to ask some specific questions about this, please email me at WCE2485@sailmail.com. These messages come in over the single sideband radio and are very slow, so keep messages under 5,000 characters and include no attachments.
Jim & Cindi GoodrichS/V Moonspun, Hull #101
Honokohau, Hawaii
Posted by Tony Williams (149.199.62.254) on May 09, 2000 at 17:01:21:
I happened to be walking through a boat yard this morning and lo-and-behold, up on the hard, I noticed a 6-to-7 year old Catalina 42, equipped with the older, squarer rudder. Having followed the Moonspun incident quite closely, I used the opportunity to scrutinize the rudder and its attachment to the hull quite closely, and I noticed some very interesting things...
The Catalina 42 has a small skeg that protrudes from the centerline of the hull, beginning just aft of the prop shaft, and ending at the rudder. (I'm not sure that "skeg" is really the correct word, perhaps "fin" or "ridge" is more accurate.) It's about 8" deep where it meets the rudder and about the same width as the rudder post.
At the extreme limits of its travel it's obvious that on this boat, the side of the rudder hits the skeg. The rudder itself was quite severely damaged by the impacts. A deep depression had been impacted into the rudder on both sides of the rudder post, revealing a 1/2" wide 4" long area of exposed fibreglass matting surrounded by severely crazed gelcoat (albeit painted-over with bottom paint.)
Presumably, the rudder had swung with some force to the limits of its travel and crunched the fiberglass.
I immediately thought of my boat, a 1999 model with the new elliptical rudder, and realized that the rudder limits are enforced by a short stainless steel cable attached between the rudder quadrant and a padeye at the transom. If I turn the wheel too far on my boat, the side of the rudder (presumably) doesn't hit the skeg because it's stopped short by the cable pulling tight. I'll certainly check this when my boat is hauled-out next month.
I wonder whether Moonspun (or 42's in general) has such a restraining cable attached to the quadrant, and if not, whether the owner remembers any incidents of the wheel being thrown over hard while reversing...?
Food for thought,Tony.
