Does old gelcoat need to be fully removed?

ALWAYS GRIND THE GEL COAT OFF TO THE GLASS BELOW TO GET A DECENT BOND WHEN YOU USE POLYESTER !!!DONT EVEN THINK ABOUT IT JUST DO IT !!as stated some where gel coat is the weak link !!

 

Hi Guys
I'm having problems with my gelcoats on my catamaran boat. I was just final polishing my gelcoat upper deck when i saw halo line (boundary line between repaired gelcoats and existing gelcoat) starting to develop. I've tried few things
1- spray gelcoat only
2- spray gelcoat with catalyst and styrene
3- spray gelcoat with catalyst, styrene and wax
4- spray gelcoat with catalyst, styrene, wax and flowcoat
However none of the above successfully removed the halo lines. Can you advise me please?

 

Live with it !! Its the differance between the old and the new and will just keep coming back . Differant spray, differant batch , differant catalyst , probably has wax , styrene and what ever else so how can you exspect it to be the same as the old that had non of those things ! even if it did have the same gel coat from the same drum with the same catalyst it will show over time . Its where you put the edges of your sprayed repair thats the important part of trying to hide the join up .Theres also the uv time factor as well and that will always make a differance . Been doing repair work for many years ! you need to joint the old and new on an edge where the light changes the colour !.

 

There are so many ways to repair GRP. Because there is no exact ways to repair GRP as there is with steel it all goes on personal experiences.

I think that there is no prob with the advice given by Fanie. The pop-rivets will provide a more secure bond for the time the GRP needs to reach total cure. So even if that is all it was used for it an an advantage. However any job is totally useless if the right preparation is not done.

Good luck and hope you have a better idea on what you need to do to get the best result.

 

Thanks Vince..I have learned alot about epoxy and grp repairs/mods since I posted that thread...I have purchesed 3 gallons of epoxy from US Composites and they ship in Florida in 2-3 days. Heeding PAR's advice(my, we will miss him...) I got the slowest cure activator and the 635 thin resin...seemed a good deal for $120.00 plus tax and $11.00 shipping i think,,still came in well under $50.00/gal. which isn't bad if your not buying a barrel of the stuff I guess...Seems like a good product so far.. I have been practicing on my new dinghy...an old racing pram that I got cheap and am bolstering up the transom to take my 5 hp tohatsu and getting practice with the epoxy before I do the new cabin roof on the H-20. I have been prepping alot..it is a long process but it feels good to know I am doing my best to make sure I get good bonds when I get knee deep.I am hoping to be done with the prep in another week and then await a good Bermuda high with some dry weather that can be counted on to hold for three or four days...we are due for such a system here...and some warm weather and low humidity it should bring...