cleaning glass

[bobsbikini]

What would be the best solution to use aside from a 60 grit disk to prep the inside of the hull to tie in new stringers,heavy duty degreaser? Dry cleaning solvent? What works that isn't going to kill the universe? I know PD-680 isn't cool anymore and purple cleaner is a bitch to get the residue off. I know where I tie in new glass has to be scuffed but I need to clean everything first. Is there a primer for fiberglass?

[ondarvr]

The first thing is to start with 36 grit grinding discs.

Many times nothing is used to clean the surface after grinding, just sweeping and/or vacuuming to remove the dust. Other times you can use a solvent of choice, most are flammable, so be careful if you use one. TSP is a good cleaner to use before painting or glassing also.

Cleaning the surface well before sanding will help prevent spreading, or grinding in any contaminate that may be on the surface. If the surface has a great deal of oil and gunk try waterless hand cleaner, then wash with TSP

[Ilan Voyager]

I assume it's GRP-glass and polyester resin.
First a good cleaning with an alkaline degreaser like TST (Trisodium phosphate) whatever the boat is new or no. You have to remove any contaminant like paraffin on new GRP, oils, greases etc.
Second a good grinding-the 36 works well- it must be rough to give good teeth to the polyester resin. Polyester doesn't glue, even on other polyester which has fully cured, so you have a key on the glass fiber itself to get on good gluing of the new element (stringer for example) on the hull.
That means you have to sand through the gelcoat and attain the first or second layer of mat.
Do not wipe with a solvent. For several reasons; a-most solvents are toxic and/or flammable, b-a lot of solvents are recycled and are enough contaminated to jeopardize the gluing,c-wiping it's the best way to fill the "teeth" with the sanding powder.
Use a good vacuum cleaner. Do not forget to use a true dust mask (not the little things in paper) and goggles, polyester and fiberglass are not good for the sinus, lungs and eyes.
At my knowledge there is not a primer for gluing polyester.
Another alternative, more expensive but less work, is to make the element ( stringer etc...) in polyester and to glue it on the hull with epoxy epoxy and a filler, after good sanding with a 60 grit if the hull's surface is smooth or a good sand blasting if the surface is irregular. That gives very strong joints. It's the system I used on old GRP hulls to be sure of the result.

[The copper guy]

You must be careful polyester resin wont bond with every thing?
Basically the more expensive resins will stick to a cheep one but the cheep one wont bond well with the other.
It is a big subject on which i am limited so please ask this specific question in the forum.
I have seen structural repairs fail with a (BANG) when lifted in the slings.
Fore warned is fore armed good luck m8

[Herman]

Actually price has little to do with adhesion.

most resins stick resonably well to each other, with aforementioned preparation.

However, bonding on DCPD resins (cheap, chemically resistant and low styrene), especially the older ones, is more difficult, and relies heavily on preparation. The cure of DCPD is near to 100%, so any chemical bond is not to be expected.

[gonzo]

Use a pressure washer to get the worse off. If you can, sandblast the area. It cleans the surface and gets in the holes without cutting the fibers like a grinding disc does

[Ilan Voyager]

Originally Posted by gonzo

Use a pressure washer to get the worse off. If you can, sandblast the area. It cleans the surface and gets in the holes without cutting the fibers like a grinding disc does

In fact sand blasting, even a very cheap one makes the best job. Fast and a good surface ready for an epoxy gluing. Unhappily for gluing with polyester you have to go into the fiber (in the first thick layer of mat) to get a hope that the fresh resin will grab the exposed glass fibers, so the grinder is required.

Gluing with polyester do not offer any guarantee on structural work as I saw while refitting mine hunters for the French Navy.

[Ilan Voyager]

Originally Posted by Herman

Actually price has little to do with adhesion.

most resins stick resonably well to each other, with aforementioned preparation.

However, bonding on DCPD resins (cheap, chemically resistant and low styrene), especially the older ones, is more difficult, and relies heavily on preparation. The cure of DCPD is near to 100%, so any chemical bond is not to be expected.

Yes it sticks reasonably well (the word reasonably means all about the reliability of the glue joint...). In a fully cured resin that becomes very unreliable in structural work, and on old GRP, as you have explained, the polyester does not work.