1981 bottomside make-over - anyone this old gelcoat ?

[hockeyfool]

I am committing to having my bottomside blasted clean to the gelcoat - wondering what I can expect
for a mostly freshwater hull this old ; any barrier coats ?
  Gonna probably have a guy blast it with corncob or walnut shell media , and see how many coats or mills thickness
to recoat  with barrier coat product.  Read all the test reviews on anti-fouling products
from practical sailor and for us freshwater guys it seems that the top performers after 14 & 24, and 30 months are ;
for hard bottom products; Bluewater's Coppershield 45, Petit's vivid, Seahawk's sharkskin,
and for ablative products; again Bluewater's  coppershield 45 ablative, scx45, Interlux's fiberglass bottomcoat act,
Micron 66, Micron csc, and Petit's Horizons, Hydrocoat, and west marine pca gold.
   How much barrier coat in llayers or mills is sufficient ? 

[noonmark]

I am getting my new to me 1983 19' back from the soda blaster tomorrow. I am strictly salt water and I don't think any paint has been removed in the almost 30 years of existence although it looks like only a few layers thick (a number of years spent on land). I'll be posting before and after pics as soon as I can.

I am also in the stage of researching barrier coats and ablative paints and would so too welcome any advice.

Curious why you are not going with baking soda?

[capras801]

I am no expert and all this is new to me but I just put on 4 coats of Pettit Exposy follow by 3 coats of Hydro coat for a thickness of appox. 12 mls ( thickness of bussiness card).[[

[Bob23]

Gents:
   I haven't done this project although it's on the list. I understand that 3 coats of InterProtect is sufficient. The word on the street is that before the last barrier coat dries completely, it's best to apply a coat of hard bottom paint for maximum adhesion.
   I have been using Hydrocoat for the last 5 years and it's a great ablative coating. I understand that it's best to apply it over a coat of hard bottom paint of contrasting color so you can see when the ablative is wearing thin. The first time I used Hydrocoat, I got 3 years out of one coat, touching up each spring when before launch. For some strange reason, subsequent years I did not get the same long service...maybe they changed the formula.
   Anyway, it is affordable, relatively non toxic (to humans), fast and easy to clean up bottom paint that works great. I aslo am a salt water guy.
   I have a 1985 23/2 with many coats of bottom paint from me and previous owners. I plan to either have it soda blasted (if the price is right) or use Peel Away. A friend of mine used Peel Away on his Morgan 30 and he raved about it.
Bob23

[brackish]

Arion's bottom had been barrier coated  by the P.O. prior to my purchasing and had anti fouling applied.  I have no idea what was used or what total millage.  I did notice some bubbles that I thought might be small gel coat blisters but they turned out to be bubbles in the barrier coat, the gel coat was smooth.  I applied two coats of Blue Water Marine  45 coppershield ablative (the one with the slime additive,) at the beginning of last summer over whatever ablative coating existed and the boat has been in the water continuously since then.  So far it has performed admirably, no slime or grass growth even at the waterline which is usually the problem area.  I think it was one of the highly rated coatings in the Practical Sailor tests.  Hoping to get at least two years out of it. 

[Davo]

I did my old Catalina 22 with Interlux 2000e, two coats, and then trailer sailed it for a while.  When I went to put it in a slip for a season I had a guy "sand" and apply CCP antifouling from west marine, worked great for the season but when I powerwashed the boat after hauling out a LOT of the antifouling came off.  Either the guy did not sand it well enough, or else it's just that it really is that hard to get good adhesion to a cured epoxycoat.  I'm betting it's a mixture of both.

[wes]

Just want to add to Bob23's comment. I did my bottom last year with the Interlux system (Interprotect 2000 epoxy barrier coat followed by Micron CSC antifouling) and the product instructions are very clear that the first coat of antifouling MUST be applied while the final epoxy barrier coat is still in the "thumbprint" state (wet enough to take a thumbprint, but dry enough that no paint comes off on your thumb). If the barrier coat dries all the way, they say you must sand and reapply another coat of the epoxy or the antifouling will not adhere. There is not much of a window of time, at least if (like me) you are working during a hot NC spring/summer. But I followed the directions, and the adhesion of the antifouling has been excellent.

I don't have enough experience to say the Interlux system is any better or worse than other brands, but I would definitely advise picking one brand with matching barrier coat and antifouling, and follow the manufacturer's procedure as closely as you can. Not a good idea to mix and match.

- Wes

[noonmark]

Back from soda blasting today. Overall pretty satisfied. I stripped the bottom of a 37' Irwin years ago and had no need to ever do that again.
A few blisters and nicks to repair but thats not surprising for an 83. I'll do one last quick sanding before the barrier coats. Wish they could get all the paint off (like under the boot stripe the whole way around) as I told them not to worry about damaging the boot stripe since I will be redoing it. But thats as close as they felt comfortable getting to the waterline. It was $650 for the 19.

Before:


After:

[NateD]

$650 is hard to shell out, but after stripping my 16 with peel-away, I'll be shelling out the money next time I need a bottom job too.



What's the best tool for removing bottom paint? Your checkbook.

[skip1930]

hockeyfool  "...blast it with corncob or walnut shell media..." if it's not too late, using corncob or walnut shell peeked my antenna. A warning...

The concern is that this blast media would be fine on the soft anti-fouling and harder barrier coat HOWEVER the substrate under these coatings is only fiberglass and is a very soft and easily a scratched coating. One reason you don't use Soft N Scrub on the hull or your car's finish. It dulls the gloss of the Gel coat. Of course this doesn't matter if your going to repaint over the blasted areas.

This is the ONE reason why I don't compound the hull seasonally with a POWER Buffer and an aggressive compound. I'm afraid I'll burn through the 'gel coat'. All my buffing is one square inch at a time with #9 Mequire's and hand buffing. Then several coats of Mother's Wax. I even wax my bottom paint.

Having used Church and Dwight Arm and Hammer Baking Soda Blast Media and a Schmidt pressurized blast pot [ soda blasting won't work if the pot is not pressurized ] and copious amounts of air...a Sulaire 250 scfm diesel compressor comes to mind...is what usually is required to soda blast. And a little water to control the dust, which will kill off the plants by changing the pH of the soil so be ware.

In a shirt and tie Binks demonstration I soda blasted the Boss's fiberglass top from a 1956 [?] Ford Thunderbird with the port holes in place.
First I depainted the clear coat.
Then depainted black color coat.
Then depainted primer.
The glass was polished but un damaged, the chrome surround looked new without pits, and the sealing rubber was undamaged.
Layer by layer down to the fiberglass without profiling [flatining] the molded curves of the fiberglass.

Can not do that with corncob or walnut, and like any blasting the speed is about one square foot per minute per layer.

I had my 1957 CJ 5 A Jeep walnut blasted and that made the sheetmetal warm to the touch.

skip.

[hockeyfool]

Thanks -everyone that helped with experience & info on my bottomside concerns !
   I will push for the soda blasting -- sounds like corncob & walnut shell can be
    a bit high on friction and heat, and good to hear about applying antifouling when last coat
of barrier epoxy is still soft.

[millsy]

I would suggest using a very high-quality roller when applying the Interprotect and AF.  Because you are not sanding between coats, you don't want to end up with a bunch of fluff in the final product.  If you re-tape the waterline before appliying the AF you will end up with a cleaner looking edge also, and for the ultimate crisp edge use fine-line for the AF. 

I've been using the Micron CSC for the past couple of seasons (salt water) and this has worked well, particularly because I can haul the boat out and leave it a few weeks without having to repaint.

Chris
Dolce C-23