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driver0606

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Hello,
My passerelle/lifting crane is causing hairline cracks in the gel coat near the hinge mounting on my Azimut 43. I understand this happens often with other makes also. There is a stress point where the box section is narrower than elsewhere.
I am proposing to fill this area with glass and resin, introduced through a 30mm hole.
Can anybody suggest whether its better to use polyester or epoxy resin, please? I am particularly wondering what will best adhere to the existing resin.
Thanks,
John.
 
driver0606 said:
Hello,
My passerelle/lifting crane is causing hairline cracks in the gel coat near the hinge mounting on my Azimut 43. I understand this happens often with other makes also. There is a stress point where the box section is narrower than elsewhere.
I am proposing to fill this area with glass and resin, introduced through a 30mm hole.
Can anybody suggest whether its better to use polyester or epoxy resin, please? I am particularly wondering what will best adhere to the existing resin.
Thanks,
John.
Click to expand...
I would use polyester; there can be an issue bonding epoxy and poly resins.
Remember the strength comes form the tight matting of cloth and resin- you cant just bung in a wad of it !
 
Thanks for that. I did not know whether my hull would have been built with polyester or epoxy resin. From your reply I assume it would be polyester. I would cut the cloth into strips and poke them in one at a time, soaked in resin. then use a brush to compact them.
 
Polyester resin does not stick well to cured polyester resin or vinylester resin. Umpteen experiments have shown this.

Epoxy does stick reasonably well and is the weapon of choice. Also if mixing and using in large amounts it is a little easier to control with retarder.

What you plan on doing will help but you really need access to the underside and to apply several layers of cloth with thickened epoxy. A truly messy job.
 
TQA said:
Polyester resin does not stick well to cured polyester resin or vinylester resin. Umpteen experiments have shown this.

Epoxy does stick reasonably well and is the weapon of choice. Also if mixing and using in large amounts it is a little easier to control with retarder.

What you plan on doing will help but you really need access to the underside and to apply several layers of cloth with thickened epoxy. A truly messy job.
Click to expand...
I think the conventional method would be to grind out the fracture and rebuild from above, and if it is then to be gel coated, polyester would be the norm. Gel will cure onto epoxy, but only if the epoxy is super- well cured.
I admit that for something semi structural like this mounting, I would get someone to do the job. I am not convinced bunging some resin and cloth into a hole will fix it ;)
 
Tanks for your replies. I am confident the cracks are only in the gel coat and not structural. They are very fine, almost invisible and I think esthetically they will look worse if ground out and filled due to difficulty in matching the colour. I don't really feel worried about the structure, but it would be nice to reduce the incidence of the hairline cracks. I will take some photos the next time I am on board.
 
I will get Joan, one of our accounts team (also known as silly old bat) to get the resin. We sent her to the local diy store a few years back to get us some poxy resin, she couldn't understand why the staff were killing themselves laughing. :D
 
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