Rudder gelcoat cracks

[David]

Al, I have been away so I don't know if you may have covered my problem. I have a 1981 Hunter 36 with the spade rudder. Two years ago when it came out for winter storage the rudder started to get horizontal cracks on the port side only (facing the sun). With my moisture meter and hammer I determined the rudder was dry with no delamination. I scraped off the paint and sanded into the gel coat. I then applied epoxy resin to the area. Last year the same problem so I repeated the process. This year again the same problem. This time I repeated the process and in addition I incorporated a layer of FRP cloth AND I painted the rudder with a white bottom paint as we did when I worked for a Hunter dealer. Within a month the cracks have again appeared. Any suggestions?

 

[Al Walker]

There must be a reason

David, It is my guess that the rudder is delaminated. The foam core will gas off as the temperature warms up (on the sunny side). Try using something smaller than a hammer like a big washer to sound out for a delamination. I bet if you cut the area away you will find the area delaminated. It is good that water hasn't found it's way in. That will make glassing over the area easier. Thanks for your question, it wsa a new one. I can't think of any other reason for gel cracks to appear. I would be interested to hear what you find. If you have any other questions please feel free to ask.Sincerely,Al WalkerFoss Foam

 

[Bob]

Whats the best way to do that...

I have the same problem and I'm getting ready to attack it for the first time. I do have a little seepage from the cracks but only minor and I believe the pockets to be localised in the vicinity of the cracks. I will know more when I've exposed it. My question for Al or anyone is: What is the best method for exposing the foam core or removing the gel without damaging the rudder. I was planning on using a wood chisel and hammer or a drill with a sanding wheel, but is there a trick or a method that you would share with me before I do something stupid?

 

[Al Walker]

Easy on the chisel

Bob, I usually use a cutting wheel and cut around the delaminated area. With a grinder, I make sure to feather the glass back about an inch or so. If you are neat in cutting away and grinding it will make the repair easier. You won't hurt the foam if you cut a little too deep. Right as I begin to glass the rudder I use resin putty (resin with filler) to fill any cuts/gouges. Laminate your fiberglass while the putty is still wet.  The key is to fix/repair delaminated areas as soon as they are detected. The longer you wait the bigger the repair you will have. Please don't hesitate to contact me of you have any further questions.Sincerely,Al Walker