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mikenmid 11-29-2011 12:49 PM

Modifying rudder - us yacht 25
I have a US Yacht 25 with the shallow keel. The rudder on this boat extends about 8 inches below the keel and is therefore the first thing to hit bottom. In any case the rudder now needs repair and I'm wondering what problems I might cause by reducing it's length. The rudder is about 42 inches deep.

mitiempo 11-29-2011 12:57 PM

Are you going to reduce the area of the rudder? If so it will make for a worse handling boat.

mikenmid 11-29-2011 01:11 PM


Originally Posted by mitiempo (Post 801600)
Are you going to reduce the area of the rudder? If so it will make for a worse handling boat.

I could compensate for the reduction in height by increasing the width. It's now about 42 x 14 inches. If I chop 6 inches off the bottom, I'd have to increase the width by 2.33 inches.

Faster 11-29-2011 02:06 PM


Originally Posted by mikenmid (Post 801608)
.... If I chop 6 inches off the bottom, I'd have to increase the width by 2.33 inches.

Another issue will be with the rudder balance... if you add all the extra width at the trailing edge you'll end up with a heavier helm... if you add it fwd you'll probably overbalance it. Ideally you'll need to split it fore and aft to maintain the current balance. You'll also have to consider maintaining the original foil shape overall... not a simple matter.

GalileoX 11-29-2011 09:01 PM

Hi there, I'm too new to be allowed to send emails or private messages via Sailnet so I hope you don't mind me getting off topic here. I also have a US Yacht 25 (swing keel). You do not find much on the internet, or Sailnet, about these boats, probably due to their short production run and multiple company production lines, i.e Bayliner, US Yacht/ Pearson. I was curious to know about your experiences with the boat. Are you satisfied with it's performance? What year is yours? How do you feel about it's build quality? Personally this is my first boat which I received in July of 2011 so I do not have a lot to compare it to. None the less I find that it points reasonably well and accelerates to hull speed pretty quickly.

mikenmid 11-29-2011 09:28 PM

I've had the boat for about 10 years. I'll have to look at the registration to get you the build year. It was a bit run down when I got it with lots of topside leaks mainly around the windows. The balsa core in the topside compounds the leak problem since you have no idea where the water is coming from. I dug out the balsa in the window openings and replaced it with epoxy and reset the windows and ports. I've also reset most if not all of the deck hardware and I now have no topside leaks. I've replaced the teak main hatch rails and the grab rails. I sail the boat on Lake Mendota in Madison Wisconsin about 9000 acres; smaller than the lakes in Kentucky I imagine. The boat is adequate for my purpose which is mainly day sails with an occasional overnight. It's quite stable with the heavy keel; I usually put in a reef as the wind gets over 15 mph as we often experience quite gusty conditions. I think the boat is over powered at winds above 15 mph without a reef. As you know the cockpit is a bit cramped but ok for 4 people. I've noticed people complain about the head door. I fixed that problem by replacing the door with two doors. One at the rear the width of the aisle that can be left half open closing off the aisle to expand the head when in use. The other smaller door is on the forward side. I also run the mast wiring down through the mast step and connect the wires to a terminal block in the head eliminating the on deck connector and it's attendant problems. The wire passes through a rubber stopper that gets pinched as you raise the mast. Let me know what else I can tell you. My email is mike.z.dorl AT

bljones 11-29-2011 11:33 PM

mike, I have a US 25 that I am parting out. The rudder is in good shape. If it helps, it's yours for the cost of shipping. It's one less part for me to toss in the dumpster.

mikenmid 11-30-2011 11:30 AM


Thanks for the reply about the US Yacht rudder. I'm certainly interested. I might also be interested in some of the other parts; things like the engine mount and the jib turning block cars. Could you send me some pictures of the rudder to make sure we are talking about the same thing and so I can assess it's condition? This is going to take some effort on your part and I'd like to help with any expenses you have such as packaging. Maybe I can arrange for pickup at a place convenient to you. Drop me a email at as that's a much more convenient way for me to correspond with you.

Regards, Mike Dorl

Hudsonian 11-30-2011 12:51 PM

I’m not an expert but have modified several blades over the years with good results. Based upon this limited experience your plan seems feasible. As you proposed you could compensate for the reduction in height by increasing the width. If you chop 6 inches off the bottom and increase the width by 2.33 inches, you’ll still have a reasonable aspect ratio if all 36” remain immersed. You’ll probably want to move the leading edge forward .6” and extend the trailing edge aft 1.7” to keep the maximum depth of chord in the same location.

Assuming your rudder currently has a foil shape and you wish to retain a fair foil shape, you should refer to NACA foil shapes. A quick Google search came up with is link Foil FAQ It appears quite useful. As I recall, epoxyworks has a good article on fairing a keel which would give you a good idea what you’re getting into.

emoney 11-30-2011 01:18 PM

My first boat was the 22' version of yours. When I got her, the rudder was missing, so I had a guy in Texas fabricate one. We had nothing but a couple of 'net pictures to go by, so the one he made was nothing near the factory's original. Matter of fact, I had him make it into a "kick-up" rudder, which might be another option for you to explore, and it seemed to work well. The 22', of course, had a transom hung rudder, which is different from yours, but the concept of the overall geometry is the same. Having said that, I don't think shortening yours will cause that much effect, at least not enough that it can't be compensated for. Now that I've gained some experience owning these things, I'd make my own, for whatever that's worth.

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