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Old 10-16-2020, 06:07 PM   #1
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CHB 42 Rudder Size

I have a CHB 42 twin Lehman trawler. I've noticed when she is on the hard that the rudder sizes seem rather small compared to the props. She is also slow to respond at slow, above idle speeds. I've wondered if I should consider adding to the material size of the rudders. I'm concerned though, that in adverse, following seas when running at hull speed that excessive rudder pressures might occur. There must be a reason for the rudder size on the boat so before I go too far into this I'm wondering if others with the same configuration have had the same issues and how you have handled it?
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Old 10-16-2020, 06:09 PM   #2
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Any chance of a picture so we can see if they look excessively small?
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Old 10-16-2020, 06:11 PM   #3
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Your lucky to have two. My 42 CHB has a single Cummins engine.
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Old 10-16-2020, 06:22 PM   #4
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As always when considering increasing rudder size consider carefully the structural ramifications. Al components that are subject to rudder forces need to be up to the task. And the rudder input forces to the helm need to be easy enough to handle for many hours at a time. I like big rudders but they need to be safe.
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Old 10-17-2020, 02:29 PM   #5
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Rudder Photos

Attached please find two photos of the rudders.
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Old 10-17-2020, 02:31 PM   #6
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Quote:
Originally Posted by rslifkin View Post
Any chance of a picture so we can see if they look excessively small?
I uploaded two photos for your review.
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Old 10-17-2020, 03:34 PM   #7
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I just looked at the photos of my 41í to see if I had any photos of the rudders. No luck. I think that they are a similar size to yours. At low speeds I rarely use the steering wheel but rather the shifters. We are going to haul out boat in the next week or so for the winter. I will try to remember to measure them and see how big they are.
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Old 10-17-2020, 03:40 PM   #8
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I think my rudders (38 foot planing hull) are slightly bigger, but not much. I've never really felt mine are too small, although at low speeds it would sometimes be nice to have less than 5 turns lock to lock, as it can take a bit of wheel work to move the rudders enough. Full lock has never provided insufficient rudder authority.
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Old 10-17-2020, 05:00 PM   #9
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Those props look like they are designed/chosen for big engines, lots of thrust and not much speed. But still probably capable of enough speed to benefit from the small rudders.

To put significantly bigger rudders on one would probably want/need a strong shoe. That will add to the drag and cost.

But the rest of it may be strong enough for bigger rudders.

If it were mine I’l go for the bigger rudders look fwd to more authority from the helm on following seas.

The cost may be mostly from fuel burn but that would depend largely on how you cruise.

But don’t forget what comodave said about steering w throttles.
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