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hanschristian.org • View topic - Stress cracks in rudder and pintle show through new paint

Stress cracks in rudder and pintle show through new paint

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Stress cracks in rudder and pintle show through new paint

Postby reno_geo » Sat Apr 20, 2013 10:23 am

After putting two fresh coats of barrier coat on the hull and rudder of Bettina, I cranked the rudder hard over to do more painting, and stress fractures showed through the new paint over the pintle, directly below the prop, running several inches into the rudder. Cranking hard over in the other direction produced the same fractures in the paint on the opposite side of the rudder. This makes me nervous. What is failing, or getting ready to fail under there? Has anyone else encountered anything like this? What is the best way to investigate the problem?

Ed
HC34T Bettina
Hull #13
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Re: Stress cracks in rudder and pintle show through new pain

Postby edelweiss » Thu Dec 12, 2013 3:17 am

I am repeatedly surprised by reports of the capacity of water to creep in thru gelcoat defects. The relief is that is takes a very long time for it to go vary far unless it is under pressure from freeze thaw cycle or maybe this far under water. It unfortunately never gets better only worse with time. The standard answer to your question is usually that you can take a dremel to it and make like a dentist and follow the crack untill it bottoms out. Then fill it back with reinforced epoxy and cover with gelcoat ( yes it will stick if you mixed the epoxy correctly ) or an epoxy type paint. If in your explorations you find a big cavity then you have another answer your question also and you have discovered early that he rudder is at risk. Better now then you know when. You can also check for saturation with a meter. Ours was also measuring saturated and we decided to replace the rudder with a new one. The gudgeons and pintle on the HC are on the outside of the rudder so there is not going to be anything inside the rudder to rust as in some designs. You can also hammer tap it for sound ( a learn skill ) Ours tapped out and was more like a thud. YOU could have it xrayed. I have never done this but the boats with steel hulls have that done. It may be obvious or hard to interpret. Homogeneous structure would be a great finding. If you decide to rebuild it, be very sure to let it dry out for long time

Mark
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Re: Stress cracks in rudder and pintle show through new pain

Postby reno_geo » Thu Dec 12, 2013 6:46 am

Mark, I was applying the epoxy-based barrier coat to prevent just the thing you mention when Bettina goes back into the water. She's been out of the water for over eleven years, so everything is dried out, and that should make investigations and repair, if necessary, easier. What I don't know is: 1.) how long are the straps attached to the pintle that capture the rudder; 2.) what metal they are made of; and 3.) how are they attached? My first hope was that this sort of fracture in a brittle coat of paint could possibly be caused by normal flexing of the rudder under the strong pressure of being cranked hard against the stop. But if there is any danger that the rudder has been somehow compromised, I'm willing to go in with a dremel, as you suggest, and investigate the structure of the rudder and find out if the fracture in the paint reflects something structural. (I've had a rudder on a smaller boat break at sea - it's not something I want to repeat.) It sure would be nice to have a drawing of the construction of a typical HC rudder so I'd know in advance what to expect. Is removal of the rudder a straightforward process?

Ed
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Re: Stress cracks in rudder and pintle show through new pain

Postby edelweiss » Thu Dec 12, 2013 7:52 am

Ed
The lower Gudgeon and Pintles on HC are bronze. Yours seem to buried and faired over. My best guess ( and Im using my words carefully) is that this crack follows a joint of separation between the bronze metal and fairing material. Each material having having slightly different flexing characteristics. To that end it is probably not structural. Typically the gudgeon/pintle assembly would be exposed and it would have a sacrificial zinc. The flanges can vary in length in different models ours are about 10 inches. The appearance of the crack raises another potential problem and that is the possibility that stops for your quadrant are set too wide and not doing their job allowing the rudder to lever over and stress these joints. You might want to check on that.

Having said all that there are still unknowns and that is the certainty that the crack does penetrate into the rudder material ( fiberglass ) I would suggest comparing a rudder from a similar model for details mentioned above. I believe the only way to know for sure is to dismantle the gudgeons and pintles from the rudder. tak ethe rudder off. Explore it, repair it , and reassemble it. Short of that I would avoid backing down with the rudder allowed to hardover.

This is a picture of our rudder.
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Re: Stress cracks in rudder and pintle show through new pain

Postby reno_geo » Thu Dec 12, 2013 8:48 am

Mark - Thanks for the photo and description. That's all good information. I'll take a look at the setting of the rudder stops, and look into removing the rudder and exploring this issue in the shop.

I could use any suggestions from owners of the earlier HC's from that boatyard - HC 34, Union 36, etc. on the structure and mechanics of the rudder before I dive into this.

Ed
HC 34T Bettina
Hull No. 13
Reno, Nevada
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Re: Stress cracks in rudder and pintle show through new pain

Postby edelweiss » Thu Dec 12, 2013 9:04 pm

I know of a union 36 still in the yard in Port Townsend. THere was a HC34 near the south end of Puget Sound, but I havent seen it for 5 years. I am not there. Maybe someone could take a picture of the 36 for you.
Hope your project goes well
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Re: Stress cracks in rudder and pintle show through new pain

Postby reno_geo » Thu Dec 12, 2013 10:28 pm

Thanks, Mark. That HC 34 in Puget Sound may very well have been S/V Saviah - Andrew and Diana Steiner. They've been cruising since 2010 and are close to finishing a circumnavigation.

Ed
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Re: Stress cracks in rudder and pintle show through new pain

Postby bigsmile » Tue Jan 26, 2016 11:16 pm

Hi Ed,
How did your rudder project work out? Did you find any info from a Union 36?

We are trying to assess rudder for a Union 36. The rudder blade movement to port binds for about last 2 inches, and there appears to be some non-concentric rotation at rudder stock / hull interface, and very possibly lower hinge at the same time. We are looking for information about the rudder & rudder hinge makeup (is it pintle/gudgeon? are there washers? etc.) and rudder stock at hull penetration, and any upper bearings in use, or issues others have experienced with smooth, full-range rudder blade movement.

This application has a metal housing bolted to underside of the cockpit deck, which has a delrin(?) bushing, all of which the rudder post/stock passes thru (so a tiller can be dropped onto the top of the post/stock). And with repeated swings of the rudder blade, the delrin busing eventually walks out of the housing.

Appreciate any insight.
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Re: Stress cracks in rudder and pintle show through new pain

Postby reno_geo » Wed Jan 27, 2016 12:57 am

Hi Bigsmile,
Your setup sounds a bit different from mine. Primarily in that I have wheel connected to the rudder by a rack & pinion. The attachment points for my pintles and gudgeons are well lined up. It sounds like yours are not, if you are having the binding you describe. My specific problem was that when I had put a fresh layer of epoxy paint on the rudder and cranked it hard to the stops either way, cracks in the paint showed up. Not totally surprising, but it made me question the construction of the pintles as they attach to the rudder. The only way to find out on my boat would be destructive removal of most of the gelcoat on the rudder just to inspect things underneath. I never did that because stress cracks in 1/16" layer of epoxy could be accounted for by normal stress of cranking the rudder hard over. Better to sail the boat (conservatively) and learn from its handling if anything is amiss. Long-term plan is to have a hydrovane wind vane which also acts as a duplicate rudder, and rely on that for redundancy. Obviously I feel pretty confident my rudder is in good mechanical shape because if I had any real doubt I'd start tearing it apart and rebuilding it without hesitation. I don't think that's warranted.

It looks like the Union boat yard did more than add 2 feet to the length of the HC34. I have seen 3 of the 14 HC 34's built, and all have the rack & pinion + wheel steering rather than a tiller. Can you remove your rudder and use a laser pointer to check how well your gudgeons are aligned with each other? It sounds like a slight misalignment is causing all the symptoms you describe.

Ed
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Re: Stress cracks in rudder and pintle show through new pain

Postby clonjers » Tue Feb 02, 2016 8:00 pm

FYI
There were more than 14 HC34s built. Mine is hul #27. It is also rack and pinion.
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