— The official website of the Peterson Cutter Owner's Group

by Greg Rodgers

KP44 #205 (1978)

This article is similar to Removing the Rudder except that it goes further into rebuilding the internal structure of the rudder.

The Problem

We decided to rebuild the rudder after noticing that it weeped a black, smelly fluid during two successive haul outs. The fluid turned into a sort of plastic when it dried so we had a good idea that there was resin deteriorating inside. We drilled holes in the rudder the first time and tried to make a better seal between the shaft and rudder. However, we still had weeping at the next haul out so we knew something further had to be done.

The Story

We were also concerned because we had heard one story of a Peterson rudder breaking. This story also indicated that the internal structure of the rudder consisted of several "rods" that were butt welded to the stock, sticking out like fingers into the rudder. The breaks occurred at the butt welds. Knowing the quality of the welds on the water tanks, we were very concerned about the welds in the rudder structure being exposed to acidic water.

We consulted with Joshua Johnson, a marine engineer in Norfolk regarding the approach to a repair. Josh is highly regarded in the Norfolk area. He suggested that we cut a "window" in the side of the rudder as opposed to cutting the rudder along the seams and splitting it. I think a Peterson rudder would be difficult to split due to the aperture in the leading edge.

Finally, in June 2002 we hired Josh to do the rebuild. I didn't have the guts to do it myself. I was concerned that I would get into the rudder, find I was in over my head and not be able to find anyone to help.

Removing the Rudder

The haul out and removal of the rudder went pretty much as Rick Crane described in his article "Removing the Rudder" which is also located in this documents section. Blocking the boat 8" off the ground will definitely give adequate clearance to get the rudder shaft out of the rudder aperture in the hull. We were able to drop the rudder without pulling the prop and shaft We have a Max Prop feathering three bladed prop installed. We disassembled the Max Prop, removing the end cap, blades, and spinner, leaving the hub on the prop shaft. Turning the rudder slightly, we had just enough clearance to slide the rudder past the shaft. You have to shorten the shaft slightly when you install a Max Prop and I think this made all the difference. 

Opening the Rudder

Once the rudder was removed, Josh drilled a two-inch hole into the rudder and pulled a core sample. The sample consisted of an outer layer of about two inches of fiberglass and then wet, crumbly, smelly plywood. Using a die grinder, Josh then cut a "window" removing most of the right side of the rudder.

We found that the skin of the rudder was about two inches of fiberglass lay-up. The plywood was intended to be part of the "skeleton structure", which I'll get into next. Lastly, there was foam "board" (not poured) filling up the remainder of the void.

Josh cleaned out all of the interior material, exposing the metal structure. Even though parts of the structure were rotten, there was no delamination. In fact, the fiberglass was still sticking to the rotted wood very well. Removing the material from the interior was more difficult than expected.

The Metal Structure

The internal metal structure turned out to be two Stainless Steel plates in the shape of an Epsilon (å ) that were welded to the left and right side of the rudder stock and lower "hinge". This left a gap the thickness of the rudder stock between the two plates. Plywood was inserted in between the plates, extending out into the rudder. Apparently, the engineers didn't feel the metal plates extended far enough into the rudder, so they made the plywood/plate sandwich.

When cleaned up, we found that the metal was in great shape as were the welds. Therefore we decided to keep the original structure and just strengthen it.

We didn't plan on putting plywood back into the rudder, so Josh took the rudder to a welding shop and had them insert S.S. flat bar stock in between the two plates at the top, middle and bottom. They then tied them together with a piece of round stock the same diameter as the rudder stock.


The Rebuild

We decided to rebuild the rudder with a solid fiberglass lay-up even though it would make the rudder much heavier. Josh started by pouring a slurry of WEST epoxy and 3M Scotchlite glass bubbles into the void between the two plates where he couldn't lay in cloth. He then glassed the metal structure to the remaining left side of the rudder with bi-axial fiberglass roving and WEST epoxy He filled out the rest of the area with bi-axial roving, various weights of cloth, and WEST. Josh also ground out the area at the top of the rudder where the rudder stock enters the rudder and filled it with WEST and the glass bubbles.

Josh left a small amount of the top, bottom and sides of the right side of the rudder intact so he could reproduce the curve of the rudder. He ran a batten over the surface of his work that was curved to the original shape of the rudder.

Lastly, Josh put three layers of Interlux Interprotect 2000E on the rudder.

All of this effort left us with what we hope is an indestructible rudder that now weighs about 100 pounds more than it did (total 200 pounds). I am not sure what the original weight was because I did not have a scale at the beginning of the project. Besides, the rudder was saturated with water. I did find a scale to get the final weight. Since there is no void, it will be very difficult for any moisture that does intrude to get very far into the laminate.  

Cost Break Out

This is the bad part about the rebuild, the cost. I have included it so that people can use it as a benchmark. Hopefully, others can find economies based on this knowledge. Although we might have been able to trim some cost, the hours charged were reasonable for the work performed. Josh offered to let us do some of the fiber glass lay-up to save money. However, I wanted to make sure the final result was of the highest quality. After spending this much money, I didn't want voids or a mediocre finish based on my so-so skills. The work Josh did was meticulous and excellent.

The following tables detail the labor and material break out for the project:



1) Remove starboard rudder skin, all wood and foam core inside, and grind interior smooth


2) Sketch up changes to rudder


3) Transport rudder to and from metal fabricator


4) Glass metal structure to intact port skin


5) Fill and fair starboard side of rudder


6) Sand entire rudder and apply three coats of Interlux Interprotect 2000E and deliver to owner


Total Hours




Labor (30 hours @ $52.50)


Metal fabrication and welding


Materials (included 5 gallons of WEST epoxy and 40 lbs. of biaxial woven roving)


Total Cost



I didn't include the cost of the haul out itself since the work was included as part of a regular haul out. However, we did spend more lay days than we would have otherwise. That would have added about $100.


Although the rudder showed symptoms of big problems, the interior structure was not badly compromised and the metal was in good shape. We probably could have gone for many years without a failure. However, even the REMOTE POSSIBILITY of a rudder failure is something that the offshore sailor cannot tolerate.

Knowing what we now know, we MAY have been able to do the job ourselves. I have learned many skills on the job while working on my Peterson. Occasionally I've had to do a job several times but I finally learned to do it right. The rudder is such a crucial piece of gear to the successful and safe operation of the boat that I just didn't feel comfortable using it as a learning aid. Also, if the structure had required redesign, I'm certain that I do not have the skills to calculate the necessary parameters. I do what I can to maintain and upgrade the boat myself. I decided that discretion was the better part of valor for this project. J

Josh also said that he would be happy to discuss this project with anyone interested. He can be reached at (757) 460-0971. If you have to leave a message, tell him the subject you want to discuss. Josh doesn't do email.


One thing we've learned about Petersons is that they vary from year to year and some times from boat to boat (We've seen differences between #205 and #206.). The internal structure of other rudders may be different from what is described here. About the only way to tell is to x-ray the rudder or to open it up and look. It would be a good idea to have a metal fabrication and welding shop lined up if you decide to open it up. It would also be a good idea to know where to buy the materials to do the fiberglass work and how fast it will take to get it before you start.

Editorial note

For those concerned about the added weight of a solid GRP rudder, foaming the interior with a closed cell foam is an option.  This can be done professionally or by using a high-grade low expansion polyurethane foam in a can.  Make sure it is closed cell foam.

Also be careful to inspect the stainless for crevice corrosion that might not be obvious (See the Canopus article below).

Tim Balfour on Canopus notes that on his boat, manufactured only a year later, had good fiberglass and bad steel.  "The core is poured foam throughout , as far as I can tell, squished between the two halves - no ply in sight. Interesting to see that the ply was the problem, as a surveyor/designer here told me not to use foam at all (no structural strength) but to re-build with wood filler pieces".  Tim wrote he is going to fill his rudder with lots of glass and epoxy. 

Whatever is used, microlite bubbles in an epoxy matrix, or wood, is going to increase the density of the rudder more than foam.  Perhaps a lightweight non-rotting wood like cedar or balsa would be a good filler?  I expect increasing the rudder mass will give it more inertia, but the exact effect on the "feel" of the steering the boat, or on the stability (more weight at the stern) will have to wait for additional reports from Tim and Greg.  Perhaps a naval architect could tell us more about the best way to do this.  If anybody else has some comments or ideas let me know.

-Jeff Stander

Website Moderator

See Related Articles:

Rudder shaft exposed on Canopus

Removing the Rudder

Rebuilding the rudder on Persistence

Last modified: February 20 2018 20:03