Mods to GRP Hull

[the big jetski]

I have purchased an Australian built boat manufactured by Whittley in 1985.
I believe the material used to build this boat is GRP (Glass Reinforced Polyester) The boat has a gelcoat finish.

This boat is an unfinished project and the previous owner has replaced transom and rear section of stringers and floor section using structural ply and epoxy.

The previous owner planned to use the 18ft cruiser for inland lakes and rivers - therefore he has only laid 1 layer of very thin tissue (fiberglass) over the timber.

I will be using the boat for offshore fishing where the hull will be stressed by rough seas so I was planning to put more layers of woven roven or chopped strand mat to add strength. I am also planning to convert the boat to a walkaround design - this will require major fibreglass fabrication - mainly a raised bow section to prevent water entry into the front walkaround.
I was also going to apply a gelcoat.

I am unsure how to finish this project because the previous owner has used epoxy for repairs.

I have just learnt the following:

1. You can not put polyester over the epoxy!! I am not particularly keen about waiting longer for the epoxy to set.

2. You can not put a gelcoat over epoxy!!

3. I have also read Epoxy is not UV resistant.

How do you think should I finish this project?

Shall I bite the bullet and finish the project using epoxy, then paint over epoxy to match the existing gelcoat?
The boat will not be garaged - Is epoxy more suseptable to cracking in the sun compared with Polyester with gelcoat?

OR

Shall I grind away as much epoxy as possible and complete the job using polyester? (remember previous owner only has a very thin layer of glass over the transom and rear stringer sections - certainly not strong enough for offshore fishing.)

Regards,
Ad












by raising the front section of the and raising the

[geo6246]

Hi, You will need to remove all of the epoxy as epoxy and PE resin will not bond. not even mecanicaly, which is your only hope. any place where the two meet will shortly delaminate. you should replace any matterials laminated with epoxy with what ever the hul lwas originaly built with be it PE or VE resin.Good luck with your project. Cheers, Geo

[fiberglass jack]

it is possable to put polyester over epoxy you have to use a transistion resin use derakane 411 its a vinylester and will allow u to bond to epoxy

[zerogara]

GRP stands for Glass Reinforced Plastic, not polyester. So Glass and any resin is GRP. FRP is Fiber R. Plastic, which may include Glass but not limited to.
Neverteless it is most likely a polyester built hull.