Trawler Rudder Sizing
- Thread starter Don L
- Start date
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If you have answers, please help by responding to the unanswered posts.
If you have answers, please help by responding to the unanswered posts.
mvweebles
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- Weebles
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- 1970 Willard 36 Trawler
The faster the boat is intended to go, the smaller the rudders become (generally). Small rudders are not as effective at low speeds so the A/P may work a bunch more.
No specific guidance though. Certainly nothing truly actionable as there is rarely specs in for sale descriptions. The Nordic Tugs and American Tugs seem to have decent sized rudders but are single engine boats. Some of the twins - probably the Present 46 you asked about on another thread - have smallish rudders. Workable, but compromised.
I'll say something a bit snarky at the risk of offending. I don't know why folks defend Semi-Displacement hulls so vigorously based on fuel economy potential when the apparently run at displacement speeds 98% of the time. Why not just get a boat that's designed for the 98% of the time and make adjustments for the 2%? I posted the other day being on a friend's boat where we powered up to make a bridge opening. Had it been my boat, would have ended up waiting 20-mins. Big deal.
Peter
rslifkin
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It's not a big concern on most boats and it'll slow up pretty quickly on a sea trial. Some SD trawlers and planing hulls have small rudders to reduce drag. Not a problem once you're going fast enough, but it can make rudder authority a challenge at low speeds in a following sea, for example.
It's not a universal concern though, plenty of boats have plenty of rudder for low speed use. And a faster boat doesn't always mean tiny rudders. My boat tops out around 25 kts but still has generously sized rudders and a lot of rudder angle, so it steers just fine in following seas below hull speed.
As far as the defense of SD and planing hulls, I figure they can be worthwhile if they have a good, usable fast cruise. But if it's going to do 3 kts over hull speed at full throttle then it's a waste as you'll never realistically run it faster than a similar size FD hull could go.
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rslifkin
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So is this mostly something to consider on a SD (I am getting the lingo some) with big engines? That the builder maybe did smaller rudders because they designed the boat to be fast than displacement speed?
Exactly. If there are pictures of the boat out of the water you should be able to tell if the rudders look particularly small. And you'll be able to tell by steering response on a sea trial. Rudders can often be up-sized with a bit of work if it's an issue on an otherwise perfect boat.
I don’t think there is a distinction between power or sail, any boats rudder can be inadequately sized, or have other issues affecting performance.
Doesn’t make them unusable, you just need to learn that boats particular handling characteristics.
Doesn’t make them unusable, you just need to learn that boats particular handling characteristics.
ancora
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Some years ago, we went out on a demo ride with a broker and some other potential buyers. The boat was a new 44 foot SD trawler. Once out there the broker allowed me to take the wheel, I put it hard over and the boat skidded around the turn. It seems the person who ordered the boat requested no keel, as it would be used in shallow water. Said person changed their mind and the broker was stuck with a lemon. All the rudder in the world would not help this boat.
