As I said in the previous post, I don't recommend that you try this at home. I'm experimenting a bit as there are some significant pitfalls to attempting to stiffen things with carbon fiber on the outside. I think it will work well though.
To recap:
The strut is solidly mounted in these boats. No danger of it coming out completely. However, it was installed by centering with a wooden wedge on each side and then pouring resin around it and the putting two through bolts through the hull structure.
The loss of a prop blade put a lot of strain on the strut as the one bladed wheel coasted to a stop and then more as I unknowingly limped about a mile to anchor at idle thinking the vibration was just a snarl of rope. The wooden wedges had turned to mush years ago and the strut developed a slight wiggle even though the glass layup around it is sound. Water was going up around the strut into the filled area of the hull skeg.
Here is the strut prepared for reinforcement with Mainesail's bearing puller having just removed the old Cutlass.
The strut felt solid by this time as I had dug out the punky wood wedges and stuffed Marine Tex up into the space on each side. This is tough stuff but I'm not sure it would hold up to maintain a water seal under the constant vibration or the strains if I pick up a lobster pot or have a prop strike.
Here is the second stage of the fix:
I first made a fairing of that quick acting epoxy that you knead together from a roll and also used that to shape the curved transition at the top leading edge. This part isn't significantly structural.
Next, I ran a piece of 1" fiberglass tape around the strut just above the barrel to make a clean edge finish (Thanks to MaineSail for this suggestion) and coated all of the strut above with T88 epoxy. Once this had barely set up, I put on another layer of T88 and pressed a piece of unidirectional carbon fiber into it. This piece tapered to a point at about the middle of the fiberglass tape strip. The next piece is the full width of the strut as seen in the photo. An additional strip between the two layers runs from the hull portion forward of the strut diagonally back along the strut to increase the hull contact area.
The carbon fiber is difficult to wet out and the thick structural epoxy doesn't help. I put another layer of T88 over the CF and then laid a piece of Saran wrap over each side of the strut which let me knead and push the epoxy to get it to penetrate the fiber without making a sticky mess. Poor man's vacuum bagging.
The photo shows the strut just after the plastic wrap was pulled off when the epoxy was barely cured. I was able to slice off some of the larger wrinkles and push some of the edges into place.
The next step will be run a fiberglass tape around the trailing edge to provide some strength against anything fouled in the prop hitting the strut. Sanding and filling will then finish the job and give me a strut I can put bottom paint on without furthering the dezincification begun by an old electrical fault.
I'll let you know next year how it worked.
To recap:
The strut is solidly mounted in these boats. No danger of it coming out completely. However, it was installed by centering with a wooden wedge on each side and then pouring resin around it and the putting two through bolts through the hull structure.
The loss of a prop blade put a lot of strain on the strut as the one bladed wheel coasted to a stop and then more as I unknowingly limped about a mile to anchor at idle thinking the vibration was just a snarl of rope. The wooden wedges had turned to mush years ago and the strut developed a slight wiggle even though the glass layup around it is sound. Water was going up around the strut into the filled area of the hull skeg.
Here is the strut prepared for reinforcement with Mainesail's bearing puller having just removed the old Cutlass.
The strut felt solid by this time as I had dug out the punky wood wedges and stuffed Marine Tex up into the space on each side. This is tough stuff but I'm not sure it would hold up to maintain a water seal under the constant vibration or the strains if I pick up a lobster pot or have a prop strike.
Here is the second stage of the fix:
I first made a fairing of that quick acting epoxy that you knead together from a roll and also used that to shape the curved transition at the top leading edge. This part isn't significantly structural.
Next, I ran a piece of 1" fiberglass tape around the strut just above the barrel to make a clean edge finish (Thanks to MaineSail for this suggestion) and coated all of the strut above with T88 epoxy. Once this had barely set up, I put on another layer of T88 and pressed a piece of unidirectional carbon fiber into it. This piece tapered to a point at about the middle of the fiberglass tape strip. The next piece is the full width of the strut as seen in the photo. An additional strip between the two layers runs from the hull portion forward of the strut diagonally back along the strut to increase the hull contact area.
The carbon fiber is difficult to wet out and the thick structural epoxy doesn't help. I put another layer of T88 over the CF and then laid a piece of Saran wrap over each side of the strut which let me knead and push the epoxy to get it to penetrate the fiber without making a sticky mess. Poor man's vacuum bagging.
The photo shows the strut just after the plastic wrap was pulled off when the epoxy was barely cured. I was able to slice off some of the larger wrinkles and push some of the edges into place.
The next step will be run a fiberglass tape around the trailing edge to provide some strength against anything fouled in the prop hitting the strut. Sanding and filling will then finish the job and give me a strut I can put bottom paint on without furthering the dezincification begun by an old electrical fault.
I'll let you know next year how it worked.
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