Sandblast Help

[Geoff McLaughlin]

Boat had some deformation (port quarter under the aft berth, cam down hard on that strut, which was too high for the keel blocking) on haul out last fall. I want to take the bottom down and possibly barrier coat, or West System, or something to seal the damaged area and the entire undersides (she is '83 vintage and hard miles anyway, though no blisters ever, and no obvious severe damage). My immediate question is has anyone out there any knowledge of local contractors int he Milwaukee area who might do it, or has anyone rented sandblasting equipement and done it on your own? I'd like to avoid the time and hassle of sanding - want to get it done right and FAST.She is H34, hull no.1.Any input or help welcome.ThanksGeoffRunning Tide

 

[jim oursler]

sandblasting is destructive

Everything that I have read says that sandblasting is erratic, so high probability for deep penetration of gel coat and imbeds particles.. Better to have it pealed if you insist on the fast way with sacrifice of gel coat. So you will need about 5 barrier layers of epoxy. It is a mess to do. Had a friend who did it on his own on a catalina 30 , and said never again.. way too much work and time..

 

[Tim Schaaf]

deformation

it is also possible to permanently deform a hull from poor blocking, WITHOUT significantly weakening it. It needs to be somewhere hot, and the phenomenon is called "creep". Talk to West Systems (Gougeon Brothers) about this. There would be no stress cracks on the inside in this case.In which case, it might be as well to leave it alone. Has a competent surveyor looked at it? There are also times when the hull regains its shape in the water.

 

[Geoff McLaughlin]

I hope so, Tim

Tim:The hull popped back out when the load was relieved. She was surveyed right after - we saw some minimal interior cracking in the area, with some (2-3) hairlines, around a half inch long, where the wooded box frame for the quarterberth is glassed in. We also saw evidence of older similar cracking, but altogether, total evidence was very, very light. Surveyor was not conclusive about corrective action. Since my post, I have been reading on barrier coats and etc, and seen some arguments for not doing it - I really don't know what if anything, I should do.Thanks for the note - and thanks to Jim also -

 

[Dick Hall]

plastic bead blasting

I have heard of a process by which paint is removed by blasting with plastic beads. The benefits are said to be lack of damage to the FG and easy separation of paint dust from re-usable beads. Don't know of any vendors.

 

[RP]

don't sandblast (long)

don't do it...everIf I sent you a picture of the bottom of my boat, you'd never ever ever want to chance sandblasting. I have a 78 hunter that someone sandblasted in 85 to fix blisters.. it seriously scars the gel coat BAD.you won't see it as first, but over time the gel coat has fine scratches and if any moisture gets in, the gel coat comes right off in tiny little strips.they put west system over the top (which would have worked fine)but a not so bright previous owner had the bottom redone in 95 and forget to mention to NOT sand off the west system.(he also thought putting really thick bottom paint would protect the hull without barrier paint. Can anyone say bottom paint an 1/8 of inch or more thick? enough said)needless to say, I'm currently in the process of totally stripping, sanding and redoing the bottom. I don't have much (if any) decent gel coat left.it'll take about 100+ hours to do it right.I found a manual labor place called Labor Ready and hired a few guys as manual laborers to sand, sand, sand, sand and more sanding.I don't know how much sandblasting is, but I know anybody competent is going to be expensive. $500 bucks will get you about 60 hours of sanding and you sitting back with a beer supervising. maybe less if you can find some summer kids with time and willingness to work for minimum wage.If the paint is really thick (like micron ultra) use a chemical stripper first. If you have something thin, like vc17, it'll come right off.