Sandblasting antifouling

[simon]

Good day everyone,

I would be interested in experiences in sandblasting antifouling on fiberglass hulls. My boat does not have gelcoat and below the antifouling is immediately the fiberglass.
Anything I do have to pay attention? I want to preserve the fiberglass layer and think that this would be also a good preparation for painting.

Cheers

Simon

[wardd]

i believe it would dissolve your hull

you could try dry ice blasting

[Submarine Tom]

I soda blasted (baking soda) my Fiberglas on plywood houseboat hull to

remove epoxy bottom paint and Gelcote in order to apply epoxy barrier and

it was brilliant!

-Tom

[simon]

it seems to work as explained on page:
http://www.maddyhome.com/canardpages...ndblasting.htm !

Sodablasting seems to be very expensive.

Cheers

Simon

[Itchy&Scratchy]

There should be no reason to sandblast, unless you have water ingress, which you would probably only know if you had osmosis, which is unlikely if you have no gelcoat below the waterline- as I thiink (I may be wrong on this, but I have only seen this in the last few years) this is a new thing leaving the bottom clear.

The other question , you need to possibly find out is whether or not your hull has been epoxied in the area with no gel? , also a fairly standard practice nowadays.

If the hull has already been keyed up and antifouled properly, you shouldnt need to remove it,but if you really must, use a DA sander with about a 60 or 80 grit disc.
J

[Submarine Tom]

Sodablasting was cheap for me. The guy gave me the machine for the day

for 100 bucks (US85). It took me the better part of the day, with breaks.

Like I said, it was slick. I'd do it again in a heartbeat.

-Tom

[missinginaction]

FWIW I'm going to second Itchy&Scratchy here. While replacing thru hulls and seacocks last summer I found it necessary to fill and repair a couple of holes in the bottom of my Silverton that were no longer necessary. As part of the repair I had to remove the ablative antifouling paint in the area. I used a dual action (da) sander and found it cut right through the paint to the gel coat very quickly with a #40 disk. I'd also recommend a good OSHA approved canister type respirator to save your lungs.

Regards,

MIA

[SamSam]

There are different grades of sand available according to mesh size used to screen it, the higher the number the finer the grains, the finer the grains the more controllable as to how fast or it eats away whatever you're blasting and how deep it cuts. Gravestone makers can probably steer you to sources.

Protect your lungs. You not only have the danger of silicosis from the powdered sand but the danger of powdered heavy metal dust from the bottom paint.

MIA, you do realize to do thruhull repairs with fiberglass, that a repair won't stick to gelcoat and you have to grind through the gelcoat to get to actual FG laminations ?

[Herman]

About blast media, there are more options than (various grades of) sand.

glass
walnut shells
metal spheres
soda
solid co2
solid n2

And probably more...

[missinginaction]

Hi samsam,

Regarding the hull repairs.....I did the repair from the inside of the boat, layering up about 5 laminations of biaxle cloth and mat that I had leftover from making my stringers. I filled the hole with epoxy resin (the hull is actually about 1/2 inch thick solid laminate in that area), then applied increasingly large pieces of fiberglass cloth to the inside of the hull building up the laminate.

I sanded off the paint so that I could apply a piece of tape to the outside of the boat (over the hole) to keep the epoxy goo from running out while I made the repair.

Thanks for the concern, I'm grateful for folks like you that keep an eye on me

Regards,

MIA

[Herman]

Solid laminate? You mean single skin I suppose. Cored laminates can be solid as well.

[missinginaction]

Nope Herman....it's a 1973 Silverton 25 1/2 foot sedan. I've been restoring it over the past 3 years. Built like a battleship. The bottom of the hull is 1/2 inch thick solid fiberglass laminate in the aft area under the engine. No core, just layup. I was amazed when I pulled the old thruhulls and saw how heavy they made it. The laminate appears to be even thicker at the chines. It thins a bit as you go forward. Ah for the good old days....when petrochemicals were cheap and the livin was easy!

Didn't want to hijack the thread though so back to the original question about sandblasting. I think that sanding might be cheaper. How much would sand blasting off the paint cost?

Regards,

MIA

[simon]

I have had a sample patch done and it looks very well. Going to do the rest next week.

Simon

[Guest62110524]

I have done plenty of blasting, you just cut back the pressure, and distance off, for instance balsting steel 120psi, but I would start at 20 psi and work up
a good resharpenable scraper like a skarston is perfectly controllable too
cheerrs

[souljour2000]

On this topic...is there a reason anyone might not recommend pressure washing to get rid of really old and flaky bottom paint on a good condition sailboat hull from the mid-80's that has been on a trailer most of it's life?