Removal of Primer on a 1964 hull

[Clip]

I'm working on making a 1964 fiberglass Navy (RCN) Whaler of the montague type more functional. I was wondering if anyone would know about the materials they would use on fiberglass back then?

The interior fiberglass woven mat is impregnated with a white chalky like primer (at least I think it is) under 40 years of grey navy paint. I tried paint remover, scrubing, but little seems to affect it as it is right into the weave of the matt. I need to bond additions to this with epoxy resin but I'm hestitant untill I know more with what I'm dealing with.

I also understand the fiberglass in the 60's wasn't epoxy, are there any problem using epoxy resins with this older material?
Boat can be seen at site:
http://www.members.shaw.ca/Klipit/Whaler/index.htm

[bcooke]

...also understand the fiberglass in the 60's wasn't epoxy

Actually, most fiberglass boats built today don't use epoxy either. Someone else might be able to pontificate on the modernization of polyester resins but I can only say with some confidence that you have a polyester resin mixed in with your matt. That is what most boats then and today use. It is cheap and it gets the job done adequately. Epoxy is a lot more expensive.

Now as for getting out the old paint... Everything has been tried and most of everything has been discussed on this forum. From my personal experience I find good old aggressive sanding to be the best for me. Use whatever grit works for you - think 36-60 grit as a starting point -and a good respirator and simply grind down the laminate until you have removed the paint.

I think you are right on with your plan to use epoxy for the laminations you are adding. That is the only right answer (IMHO) Epoxy excels at gripping physically to the underlying material unlike polyester which adheres better when the materials are all in the curing stage and the applications can bond on a chemical level. Epoxy will have no trouble bonding with your older material. I would wipe off the dust (or vacuum) and wipe down with acetone to make sure there is no chemical residue left behind and let the epoxy do its magic.


Cool looking boat...

-Britton

[Summersdawn]

I once talked to a guy who claimed to have worked building fiberglass boats for the Canadian Navy. He said the boats were all laid up with polyester resin. He said it was difficult building them as they had very strict timelines on how the layup was to proceed. They were only allowed so many hours between each layer, and it all had to be documented, otherwise the Navy would reject the boat. This was to ensure a chemical bond between each layer.

Britton is right - epoxy is definitely the way to go. With epoxy you don't need to worry about a wet on wet layup to get good adhesion, and epoxy will adhere very well to polyester.

[Clip]

Thankyou for the advice.
-Summersdawn "I once talked to a guy who claimed to have worked building fiberglass boats for the Canadian Navy."

The hull is thick and seems in excellant shape. The only problem areas appear to be cracking in the gelcoat near the gunnels in couple of spots due to improper handling with a crane and a couple of bings near the bow.

It has massive floatation chambers that I will need to sample for moisture in the interior foam. One problem is the way the rudder attaches to the stern. The 6 bolt holes that hold the rudder hinge appear to be in big need of work. I do have alot of modifications to do with her though and it will take a while. It sat in farmers field for the past 10 years and was covered in mold and moss.

[Tim]

I find that grinding using a variety of tools and grits is the most effective way at removing old paint from fiberglass. Please be aware, however, that there is a limit to how much you may be able to--and should--remove from the weave of the material. You could certainly grind away till the paint is all gone, but this may require removing more material than necessary or desirable.

I think it's OK for this sort of thing to allow some of the old paint to remain in the low spots (the dips and divots in the weave of the material), as long as all the loose paint is gone, and as long as the area has been substantially sanded. This tends to expose more than enough raw fiberglass to ensure good bonding with subsequent layers.

Epoxy will of course bond with paint, too, but the problem here is that all the strength, as it were, is hinging upon the paint's bond with the material beneath--hardly a good situation. But if you do a thorough grinding job, even if some paint remains in the low spots, you'll find that you will get excellent bonding.

As others have said, epoxy resin is the ONLY resin to use for ANY repair work on fiberglass boats. It is the ONLY resin that will provide the strongest secondary (non-chemical) bonds with the material below--whether polyester or epoxy.

[Duncan]

I need to bond additions to this with epoxy resin but I'm hestitant untill I know more with what I'm dealing with.

So long as it's only additions, that would limit the issue to certain areas? Even if you were a bit agressive with acetone/scrubbing/grinding in those areas, you could build back up with epoxy once you have a solid surface to bond to?

little seems to affect it as it is right into the weave of the matt

If it's in there that well, and resists chemical and physical attacks, sounds like you probably have a pretty good surface to work from?

[Capn_Tom]

A stripping wheel made by Norton called the Rapid Strip is recommended by West System as an effective prep tool for woven mat. The flexible wire spindles reach into the depressions and rough up the surface.