Consequences of shortening rudder

[MGRodems]

As for the handling while heeled over, I owned and raced a C&C 35 MKI extensively for 11 years in some pretty rough conditions (Lake Erie). It had a small and shallow rudder that was known to be inadequate. I did not have issues with steering while the rail was in the water, so I assume the type of sailing I expect to do while cruising with the Irwin will not be a problem.

If I lose up to 6" of a 60" tall rudder at the point where the chord is the shortest, I don't think the steering will be any worse than the smallish rudder I had been used to in racing conditions with the C&C.

Just my personal feeling.

[thinwater]

Originally Posted by Snore

My bar napkin engineering says this would move the center of lateral resistance forward. To avoid having issues with the boat rounding up, you would need to go with a smaller headsail. This would move the center of effort forward.

Actually, I think you mean you would need to reef the main earlier for two reasons:

• Reduce rounding up in gusts.
• Reduce the lateral load, since area is reduced.

Yes, you can simply turn the rudder farther, but that will increase drag and it will stall if the angle is too great.


Unless the rudder is very, very nearly as deep as the keel, I would leave it alone. I've sailed short rudders and they aren't nearly as good, more than the difference in area suggests, because the aspect ratio is also reduced.

[jtsailjt]

Sounds to me like you’ve made up your mind. Good luck with it and please come back in a year or so and let us know how it works out regarding sailing performance.

One thing to be aware of that you may already know is that many rudders have a metal framework embedded in foam and then covered with fiberglass and unless you can get info from manufacturer or get your rudder X rayed, it’s hard to know how far up from the bottom of the rudder the metal begins.

[MGRodems]

Yes, I understand. Since I have to repair the bottom of the rudder already, I can work my way up little by little.

[Bill O]

Originally Posted by MGRodems

As for the handling while heeled over, I owned and raced a C&C 35 MKI extensively for 11 years in some pretty rough conditions (Lake Erie). It had a small and shallow rudder that was known to be inadequate. I did not have issues with steering while the rail was in the water, so I assume the type of sailing I expect to do while cruising with the Irwin will not be a problem.

If I lose up to 6" of a 60" tall rudder at the point where the chord is the shortest, I don't think the steering will be any worse than the smallish rudder I had been used to in racing conditions with the C&C.

Just my personal feeling.

Two totally different boats and under bodies.

As a scientist I like to look at factual data or papers from professionals that have done a lot of previous research in the area of interest. This will provide you w/more info to either reinforce your belief(s) or discount them and then come up w/a better plan.
As suggested previously, look at as many papers as possible on rudder design before you start modifying your rudder. In the lab we had a saying, 1 hour of research saves 10 hrs. of development time.

If you feel confident/believe that cutting the rudder down will work for you, then go ahead w/the experiment.

[TrentePieds]

Shrew and BillO have it right :-)!

Wouldn't it be simpler and better just to train/discipline yourself to stay out of water that's too skinny for your boat?

Isn't that the very essence of sound pilotage?"

TrentePieds

[jtsailjt]

Originally Posted by TrentePieds

Shrew and BillO have it right :-)!

Wouldn't it be simpler and better just to train/discipline yourself to stay out of water that's too skinny for your boat?

Isn't that the very essence of sound pilotage?"

TrentePieds

Sounds like good advice for most places but unrealistic in the Bahamas unless you want to almost always anchor outside the harbor and dinghy a long ways in. Lots of places have a 6’-10’ channel or cut leading into a deeper harbor or anchorage. But the problem is that since there’s so much sand it’s not unusual for the sand to shift around a bit so the deep part of the channel isn’t quite where it was last year, or when your charts were last updated. The Bahamas is the only place I’ve ever sailed where you can sail with no land in sight all day long and the depth sounder never read more than 20’. In water that shallow and frequently less than 10’, just a couple feet worth of sand shifting around can make the difference between an uneventful passage and “touching bottom.” But the good news is it’s usually pretty soft sand and even your bottom paint will probably survive mostly intact unless you’re really moving fast when you touch. I was a little flustered and embarrassed the first time I went aground down there but even though I was trying to be careful it happened again and again with no damage so I decided as long as I was going under about 2 knots when it happened, it was no big deal and was able to easily get myself “unstuck.”

So I think the OP is wise to consider how he’s going to handle this situation with his winged keel. That’s undoubtedly going to make it a little more challenging but still very doable unless he’s going fast at high tide when he hits.

[seabreez]

Originally Posted by Tetepare

Our rudder is also the same draft as the keel, and when I grounded on rock it took a beating. I’ve often thought about shortening it, but I’m sure it would negatively impact high-heel sailing and already iffy reverse. Each boat will respond differently.

Two things here... one about modifying a rudder, stand alone rudder I modified, I made sure I had the same or more square inches of wetted surface. In one case I added more surface as the vessel was not responding enough for the experienced owner. I, we modified, added 15" x 4" forward and 12" x 2" at the rear to have a more balanced rudder. This made a huge difference of 84" square inches of wetted surface which made a huge difference in turning ability control sand ease or turning and less force for the operator to turn.

On another note... I have pulled many sailboats off sand bars and stuck in the mud and rocks. By heeling them over by using the main halyard to heel them over with a very small pull, made a rescue very easy and without damaging any vessel or any rudders. I remember one in particular, a 50 footer, the owner was very nervous and asked if I was insured? I replied that I was the only one for miles that could solve his problem in minutes without any damage. He gave me permission to proceed and when he saw how easy the pull was done, he was surprised and we talked this out more and he realllly learned from that experience.

Modifying a rudder takes planning and is expensive and has to have a very good reason to do so... not only getting stuck in the mud or rocks...

[Searles]

Have rebuilt a number of rudders for a number of reasons,shortening that rudder 6inches and radiusing the bottom leading edge plus a smaller radius on the trailing edge and may achieve wot you wish ,you will not notice any change in the handling of the vsl .⚓️⛵️

[Jim Cate]

By heeling them over by using the main halyard to heel them over with a very small pull, made a rescue very easy and without damaging any vessel or any rudders.

Yeah, but... the OP has a rather wide wing keel, and that pretty much makes the induced heeling approach not work at all.

IMO, that alone rules out the wing keel as part of a cruising boat's design. But it's what he has, and he's trying to improve his odds of getting off the putty on his own.

And to say that he can, by exercising "good seamanship" never run aground is just silly. One can never be sure of such an outcome... improve the odds, sure, but that's about as much as one can actually do in the real cruising world. Whether it is poor charting, changing conditions, operator error, equipment failure, actions of other boaters... whatever, even superb skippers run aground if they do a lot of miles in strange waters. Folks like Jimmy Cook come to mind...

Jim

[MGRodems]

While I would like to follow the advice of those I agree with, I also like to hear from others who disagree. I always say, "If skipper and tactician both agree, and there is no discussion, there is still a chance they are both wrong".

I need to make a small repair at the bottom of the rudder already, so I will proceed with caution on slightly reducing the draft and rounding the edges.

I hoped to have avioided most of the groundings in my future endeavors by selecting a shallow keel. I just do not have any experience getting off with a wing.

[Jim Cate]

A reasonable decision IMO... do it!

But then,

I just do not have any experience getting off with a wing.

I guess you might need that old theory about trying with a "wing and a prayer"... most of us do when aground, no matter what the shape of our keel!

Hope it works out for you.

Jim

[skyhawk]

just as a thought experiment.... part of the problem is loss of rudder authority because of the reduced control surface area.
As part of the project, you could in theory replace the lost area by making the chord of the rudder a bit longer.
Certainly changes centers of pressure and such...but how so?

I'm not saying I would consider modifying the rudder at all..... Just on the surface of it it rings like a solution in search of a problem to me. My time in power boats with inboard engines have told me how precious rudder authority can be. I'd instead, as others have already pointed out, focus on tools and habits to stay out of such a mess to begin with... and for solutions if/when you do get into it.

It is an interesting thought experiment though....

[Tetepare]

Originally Posted by MGRodems

While I would like to follow the advice of those I agree with, I also like to hear from others who disagree. I always say, "If skipper and tactician both agree, and there is no discussion, there is still a chance they are both wrong".

I need to make a small repair at the bottom of the rudder already, so I will proceed with caution on slightly reducing the draft and rounding the edges.

I hoped to have avioided most of the groundings in my future endeavors by selecting a shallow keel. I just do not have any experience getting off with a wing.

Short of waves much taller than you think are necessary, wait for a fishing boat. AMHIK. My favorite cruising grounds are skinny rock water. The best hide aways are those others are afraid to approach. I can’t tell you the number of times I’ve been relaxing in the cockpit when a dingy motors by, and I can tell from their faces they’re wondering how the heck did this guy get in here?? So bumps happen. This year it was sand, and luckily I was able to power off.

[MGRodems]

Resolution:

Here is what I did. I cut 3" off the bottom of the rudder (less than 4% of the surface area). It was damaged a bit from a bounce the prior year (in my very shallow slip), so I needed to do some repair work. I sealed it and launched this past spring. We took a 1,500 mile trip through the Great Lakes and I did not notice any adverse effects on control or steering whether by hand or using the autopilot. I feel I will have a slightly better chance of keeping the rudder free when the keel is on the bottom.

I did not touch bottom this year, but when we get off the Greast Lakes next year we most likely will. Still haven't experienced getting off a grounding with a wing keel.