tangled-lines
08-02-2013, 02:26 AM
I'm adding this post for informational purposes only, and hoping it might be helpful for others with similar problems. I'm no expert with fibreglass, but this seems to have worked for me. I mention WEST system epoxy in this post, and if you do a search, you will quickly find they have some excellent videos and articles/books for download on the use of this material. All I can say is it is bloody tough stuff. Just allow a few drops to get between two sheets of marine ply accidentally and try to pull them apart the next day, you will need a pry bar, and the epoxy doesnt give way, the marine ply is what comes undone.
A while back had some issues with cracking of the gelcoat where the transom meets the outboard well. A fibreglass repairer said it was a soft transom,but the transom core felt quite solid, so I guessed it was due to excess flexing of the outboard on the transom. I recalled a grounding sometime earlier, and my outboard sits on an alloy transom block whcih raises it a few inches. Had thought about this when I installed a new outboard, and the dealer felt it was advantageous to keep the alloy block as this keeps the power head up away from the salt water.
The cracks went right throught to the interior, and I could feel them opening up slightly when applying force to the outboard leg. My mates all said all fibreglass boats develop gelcoat cracks, nothing to worry about. But it all meant fatigue to me.
The solution for me was to take the outboard off, and grind out the cracked areas thoroughly, ensuring a rough key for the new glass.
Instead of using the original material of polyester resin, I went to the superior WEST system epoxy. I wet the area first with straight catalysed epoxy to promote a good bond, using acetone to wipe the area clean first, then followed a number of stagered layers of biaxial glass cloth, possibly some double bias as well, then some epoxy bog to finsh off before gelcoating.
On the inside, I ground out the cracks, filled these with an epoxy bog and laid glass/epoxy immediately over the bog while it was still wet, which seems to promote adhesion as well as smoothing out the radius of the bog. I also noticed that the interior outboard well was adhered to the transom by bog alone, so I ground that back, and laid some epoxy resin and glass cloth layers to boost the strength in this area as well.
Since doing this, there have been no more signs of flexing/cracking in this area again, probably stronger than it ever was.
Have attached some photos of the damage, and after repair. The outer transom isnt like original, needs a lot more cosmetic repairing, but you can see that the area hasnt cracked, and the repaired photos were taken tonight, a good year after the repairing.
A while back had some issues with cracking of the gelcoat where the transom meets the outboard well. A fibreglass repairer said it was a soft transom,but the transom core felt quite solid, so I guessed it was due to excess flexing of the outboard on the transom. I recalled a grounding sometime earlier, and my outboard sits on an alloy transom block whcih raises it a few inches. Had thought about this when I installed a new outboard, and the dealer felt it was advantageous to keep the alloy block as this keeps the power head up away from the salt water.
The cracks went right throught to the interior, and I could feel them opening up slightly when applying force to the outboard leg. My mates all said all fibreglass boats develop gelcoat cracks, nothing to worry about. But it all meant fatigue to me.
The solution for me was to take the outboard off, and grind out the cracked areas thoroughly, ensuring a rough key for the new glass.
Instead of using the original material of polyester resin, I went to the superior WEST system epoxy. I wet the area first with straight catalysed epoxy to promote a good bond, using acetone to wipe the area clean first, then followed a number of stagered layers of biaxial glass cloth, possibly some double bias as well, then some epoxy bog to finsh off before gelcoating.
On the inside, I ground out the cracks, filled these with an epoxy bog and laid glass/epoxy immediately over the bog while it was still wet, which seems to promote adhesion as well as smoothing out the radius of the bog. I also noticed that the interior outboard well was adhered to the transom by bog alone, so I ground that back, and laid some epoxy resin and glass cloth layers to boost the strength in this area as well.
Since doing this, there have been no more signs of flexing/cracking in this area again, probably stronger than it ever was.
Have attached some photos of the damage, and after repair. The outer transom isnt like original, needs a lot more cosmetic repairing, but you can see that the area hasnt cracked, and the repaired photos were taken tonight, a good year after the repairing.