Is a larger rudder a bad thing?

[jweir]

Ok, I’m posting this here possibly for a wider audience. As many of you know, I’ve been rebuilding a 32 Holland. I dropped the skeg and as a result need a longer rudder. The original was fiberglass over a bronze shaft. I’m about to order SS plate to start fabricating my new one . I’m planning on 3/8” plate like Glen’s shop uses and I spent a half hour under @Leakys 32 this afternoon templating his (from Holland). My question is this, Glen’s rudder is 24” tall and 17” wide (tapers to 15 1/2” at the bottom). From a 24x24” sheet I can go to 19” wide with enough stock for my horizontal braces. Is there any downside to a larger rudder besides steering stiffness? I have power steering so I’m guessing that is a non issue.

 

[kehoff]

I dont think 2 inches will matter , but a small rudder is a problem

 

[Genius]

Stop, read.

 

[Quik Fix 16]

Stop, read.

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I just ordered this book. Know I have never paid that much for a book before. Why now that I'm quitting?

 

[southshore30]

consult or do more research before final decision. If your going to add 2"+ to the trailing edge then add a half inch or so to the leading edge in front of the rudder post to offset forces.There is a formula for this, I'm just throwing those numbers out there. Also don't bevel the edges, just break the sharp edge. Better hydrodynamics

 

[GLA]

I am not an expert on design, my provincial does have a big rudder
it makes it easy to go in reverse, touch it in gear and just steer it left or right
it does have a flair on the back end of it, not just a straight piece of plate

 

[Scooby]

My 34’ Robert chummy rich has a large rudder. Chummy said he used it so boat can turn at right angles. It pretty much does.

 

[MBILL]

Here's a pic of my large rudder (35 Duffy). I'm very happy with its performance both running forward and backing down.

 

[SOU'WESTER]

Nice project. Might want to consider what the increased forces on the larger rudder would mean to the rudder bearing and shaft seal re: potential increased wear and/or leakage, but all solvable.

 

[Keelboater]

Increasing the unbalanced area by 48 sq. in. will most likely require re-balancing - moving the rudder shaft. Even though you have power steering I would do the math to verify things before cutting and welding. I went from a fiberglass rudder to a larger stainless one as well. No regrets doing it and very happy with the steering.

 

[Old Mud]

The design of that rudder looks good to me. You might want to check with Glens shop on making any drastic changes. I'm sure they have tried many different styles and shapes. Also Mo Jo /Chris on here can probably give you his input. Anyone who polishes his rudder so you can shave in it has input.

IMHO if it were me I would cut the top shaft off and replace it with the length you need.

 

[bigjay]

When we repowered our Cape Dory, we found anoxic corrosion on the rudder shaft and had to replace it.
We replaced the fiberglass rudder with a stainless steel one almost exact dimension and 3/8 thick SS
The leading and trailing edge dimensions exact, height also the same except the original had 2 inches additional material on the lower end behind the lower shaft post. The original rudder was 1 1/4 thick fiberglass with a rounded leading edge.
My turning performance when backing has diminished and I suspect it may be due to the thickness of the new rudder. The difference in surface area is minimal.

Greatly appreciate any thoughts/comment

original 3" leading edge, 12" behind shaft, 24 "height , 1 1/4 thick * height increases 2 inch behind lower shaft post
new 3" leading edge, 12" behind shaft, 22 "height, 3/8 thick

 

[tunamojo]

Mojo inc’s Rudder , boat handled like a Ferrari

 

[Kailua Kid]

Mojo inc’s Rudder , boat handled like a Ferrari

View attachment 155466

Some of us will just have to take your word for it as regards how a Ferrari handles!

 

[Alexpsa]

My H&H 32 has quite a large rudder, makes it easier to steer in tight quarter and slightly more sensitive under way
The only thing I would keep in mind is rudder stock and bearing size making sure you are not on the lower limit on both, ram too, the idea to offset the forward part is a good one
Ps this is right after take her out of the water, just some slime that cleaned up with a soft sponge, prop speed for the win !

 

[capecodda]

+1 on Southshore's post. From experience with blow boats, not with my DE (but water is water), bigger probably doesn't hurt much (drag vs control), might even give you more control, but the ratio of area forward of the post vs aft does. There is a balance of forces that affect the amount of torque you need to apply to the post. Think about making a turn, the part forward of the post is trying to turn the rudder into a sharper turn, and the part aft of the post is trying to turn the rudder into a shallower turn.

 

[ShaftMan]

Ok, I’m posting this here possibly for a wider audience. As many of you know, I’ve been rebuilding a 32 Holland. I dropped the skeg and as a result need a longer rudder. The original was fiberglass over a bronze shaft. I’m about to order SS plate to start fabricating my new one . I’m planning on 3/8” plate like Glen’s shop uses and I spent a half hour under @Leakys 32 this afternoon templating his (from Holland). My question is this, Glen’s rudder is 24” tall and 17” wide (tapers to 15 1/2” at the bottom). From a 24x24” sheet I can go to 19” wide with enough stock for my horizontal braces. Is there any downside to a larger rudder besides steering stiffness? I have power steering so I’m guessing that is a non issue.

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When you're ready to make your rudder, give me a call and we can make it up for you
Rose's 978-283-0280

 

[enginecom]

Think the rule of thumb is 1/6 forward which helps with force needed to turn it. With two bearings bigger rudders work great. I tried larger ones on a twin engine pleasure boat with only one bearing at the stuffing boxes. In a sharp turn it popped apart the tie rod due to flexing the fiberglass. I added a second inside bearing on the elongated rudder shaft and that cured it. The new rudders were twice the size as the originals. Worked great once that problem was solved. Hopefully your skeg is strong and that boat isn't fast. This one did 30kts.

 

[Brooksie]

More rudder area will have more drag but then switching from an airfoil to flat plate has more drag anyway.

 

[tunaorlater]

consult or do more research before final decision. If your going to add 2"+ to the trailing edge then add a half inch or so to the leading edge in front of the rudder post to offset forces.There is a formula for this, I'm just throwing those numbers out there. Also don't bevel the edges, just break the sharp edge. Better hydrodynamics

Spot on.