SailNet Community banner
  • SailNet is a forum community dedicated to Sailing enthusiasts. Come join the discussion about sailing, modifications, classifieds, troubleshooting, repairs, reviews, maintenance, and more!

OK, so I'm Sanding My Bottom...

12K views 97 replies 23 participants last post by  Squidd 
#1 · (Edited)
But I'm from the Midwest and not so sure what I'm looking at...(all we paint out here is houses barns and tractors...)

Is this supposed to be so "lumpy"...



Doesn't look like any "paint" I've ever seen before... It looks "thick"... like an 1/8" thick and like it was put on with a spatula and back brushed with a whisk broom...that's just the "Red" layer...



And it's "Soft" almost chalky or powdery...some of it flakes off (in the blistery ares and the "layered" areas.. and then the rest is stuck on tight...

Below that is a light blue/gray also "Thick" powdery layer...





I think it had popped blisters as well and then the red went over that...

Below the Gray is a greenish chopped fiberglass layer that is hard...

The whole thing down to Glass is almost 1 1/4" thick...



But you can see some of the red also goes all the way down to the glass matt..

So what do I got here and what do I do with it...??

I'm thinking continue sanding all the blisters/bubbles down to the green glass matt and then fair and fill with some sort of epoxy/poly "filler"...?

Then fair the bulk of the bottom to smooth out the "lumps...

Prime (type) ??

Bottom paint...

What I'm looking for is advice on getting it to the "primed" stage...There's enough arguments/threads on bottom paint choices already...

Thanks in advance...
 
See less See more
5
#2 ·
Wow Squidd, it look s like you've opened a real can of worms. My guess it this boat as been filled and faired,, and fillled and faired,,, and filled and faired again, and not once was it done right.

I couldn't begin to tell you all the steps but you have to get down to a firm foundation. I hope you got a good deal on the boat.
 
#5 ·
Wow Squidd, it look s like you've opened a real can of worms. My guess it this boat as been filled and faired,, and fillled and faired,,, and filled and faired again, and not once was it done right.

I couldn't begin to tell you all the steps but you have to get down to a firm foundation. I hope you got a good deal on the boat.
Deal wise I'm doing OK... bought it at auction for under a grand, hauled it home for under a grand...and have it rigged and readied to sail for just a little over a grand (lottsa work on my part)....So depending on what the bottom takes I'll be on the water well under 4...

I'm not looking for a 30 year repair or "investment"...

I want to do it "well" and reasonably economical for now...I don't think I'll be going down to glass and re gelcoating the bottom, I just want to get it faired, waterproofed, hard coated and back in the water...
 
#3 ·
The "gel coat" if there is one is whats throwing me...

I would assume the ablative coat(s) <red> would be soft and when sanding I should "hit" a hard coat layer (gel coat) but it just kind of mixes and blends with the gray coat and then bango...glass matt...??

Here's a couple more shots...where you can see glass and depthe of "gray matter"





Blisters aren't "watery" blisters more like air bubbles between layers...and then when they open, they kinda peel away at the edges to become open "sores"..

Some in the red just down to gray... and some in gray that were covered by red...

And a couple that went thru both layers down to glass matt
 
#4 ·
Pretty cool pictures of the surface of the moon!!:eek:

What are you using for this job? Looks like a very aggressive abrader, I'm a little worried you're going too deep. Some of these spots look well into the laminate.

Huge fairing job ahead!
 
#6 ·
60/80 grit in 5" random orbital...

There are some deep grooves in the glass but you can also see the red in grooves that were there before I got to it..
 
#7 ·
Squidd,

Ditto what jfdub said.

If you want to be in the water this season, forget you saw what you saw, mix up some slightly thickened epoxy, slather it on the exposed mat, roll it out, mix up some fairing compound, slather it on, sand and shape it, cover it with some barrier coat, bottom paint and go. In the fall, soda blast it and spend the winter cleaning it up.
 
#8 ·
Squidd

You don't have to re-gelcoat it. But you have to get rid of the bottom paint from the previous 3 decades or so to get any fairing material to stick to it. Apparently no previous owner bothered.

I don't think it would be very expensive - a lot of work though.

After the bottom paint is gone, fill any dips with thickened epoxy, fair with epoxy mixed with low density filler, a coat or 2 of straight epoxy and then bottom paint.
 
#10 ·
Since you're sanding that super toxic stuff, I assume that you have all 147 permits that are required and that you've conducted fish impact studies as well using EPA certified salmon psychiatrists....

:)

MedSailor

PS That grey matter looks like the real fiberglass of your hull. Me thinks you went a little too deep there. Perhaps a lighter grit sandpaper would be better?
 
#11 ·
What you have is very thick old bottom paint (the red) and ground out blisters ( the craters). Remove most of the red stuff with your sander. Fill the craters and holes with epoxy mixed with low density plastic filler, put it on with a putty knife. Sand it smoothish, no neeed to be obsessive about this on an old boat. Put a layer of thin epoxy over the filled areas. Do not try to seal the boat with epoxy, it will not work. Then put on your bottom paint and go sailing.
Blister "repair" is almost always a waste of time, fixing something that isnt broken. Ignore any more blisters that are not broken open.
 
#13 ·
What you have is very thick old bottom paint (the red) and ground out blisters ( the craters). Remove most of the red stuff with your sander. Fill the craters and holes with epoxy mixed with low density plastic filler, put it on with a putty knife.
I agree, but don't use a putty knife - you will be sanding until June.

Use a wide flexible piece of plastic, the wider the better. Used carefully there will not be much sanding required.
 
#14 ·
Brian is right about making a mold for the surface when applying 'putty'. Something like a thin plexiglass sheet can leave a nice fair surface or cut up a plastic milk gallon and use the smooth side for small patches. You will have to come up with a way (duct tape, dead men) of applying light pressure to your repair to hold the mold in place evenly. Even thin plywood (< 1/8" thick) can make a decent mold and bend to the shape of the hull. Any wood left on is easier to sand off then fiberglass/FRP.
 
#15 ·
I wasn't exactly recommending that. I was just recommending using a wide flexible piece of plastic instead of a putty knife. The thickened epoxy should be mixed just thick enough that it doesn't run or sag. If you can fair the epoxy as you put it on over 12" or 16" width the sanding will be a lot less than if using a putty knife.
 
#20 ·
Since you're sanding that super toxic stuff, I assume that you have all 147 permits that are required and that you've conducted fish impact studies as well using EPA certified salmon psychiatrists....
We tend not to have many environmental regulations in Wisconsin... less in the past 18 months... oops did I say that out loud?
I just filter that stuff threw my cigarette butts anyway...at least till they clog up...

Heck, cut my smoking in half...
 
#19 ·
I agree with the wide flexy plastic thingy. This is really an easy repair if you use epoxy, forget Bondo. Get some epoxy (you need about a qt) with those little metering pumps. Save a bunch of butter tubs for mixing it in. Get the reddish plastic low density microballoon filler. Get some of those cheap chip brushes from Wal Mart, get a bunch of em. Mix some epoxy unthickened and paint it in the cavities to seal them. Next, mix up some epoxy thickened with the filler and put it in the cavities using the plastic thingy to spread it to shape of the hull.

Something I'd try, tape wax paper over the craters on top of the epoxy. The wax paper does not stick to the epoxy and will give you a smooth surface.
 
#29 ·
I agree with the wide flexy plastic thingy.
The wide, flexy thingy is called a screed. An old hand saw blade works well - just grind the teeth off so you have a flat edge.
 
#24 ·
Yep... The more I read up on it the beter I feel about it...

After reading some of these commentaries, I'm left wondering if there is a "do it right" solution....

In which case whatever I do will be the correct responce <solution>...
 
#25 ·
Just finished up sanding... Feels like I've been sanding for a week...

Wait a second...I have been sanding for a week...

Anyway, after laying under this thing, staring at it day after day...It really doesn't look all that bad...Overall shape is still discernible just has a hundred or more "divots" to fill, so it shouldn't be too hard to "fair out" and get smooth...



After the 1/8" of ablative coating was sanded off, the resultant divots were only a 1/16" deep on average so not much filler will be required...



Worse one was the big one in the front (first page) but even that one is less than an 1/8" deep..



I think the late afternoon "shadows" were making it look worse than it is in the first couple photos...

Plan is to fill and fair with Fiberglass Marine Filler and then a coat of Polyester Resin overall, scuff sand and then hard biocide finish...
 
#26 ·
Just finished up sanding... Feels like I've been sanding for a week...

Wait a second...I have been sanding for a week...

snip...

Plan is to fill and fair with Fiberglass Marine Filler and then a coat of Polyester Resin overall, scuff sand and then hard biocide finish...
Can you remove that sea strainer and lightly sand that area too? I took mine off this year allowing me to paint under the strainer but I had to take out the 4 screws holding it in place.

The 3M Marine Filler is a vinyl-ester product but seems to be intended for what you plan on using it for.

Conventional wisdom has it that epoxy resins have better adhesion than polyester resin which is why people barrier coat with epoxy. However, David Pascoe doesn't seem to think that conventional wisdom knows very much about blister repair.

Your hull does not look so bad after your sanding so have at the next phase.
Good luck with your plan.
 
#27 ·
There was another cover/strainer over that sea strainer...(blue rectangle)...that I took off...

I think that bubble is part of the thru hull, But I can take another look...

Using Evercoat 574 Marine Fiberglass filler supposed to be for below water use...Don't know if that's different than 3M product.

As far as epoxy vs poly...sounds like there is no expert schedual for permenent repair of blisters so whatever I put on is going to fall off...or not...
 
  • Like
Reactions: OPossumTX
#28 ·
Congrats on the job! I'd suggest one more thing to do before you start filling and fairing. Make sure large (and small) areas the remaining gel coat are not peeling, loose, or barely holding on. Good luck!
 
#30 ·
I'd only use epoxy and epoxy mixed fillers myself, but I've been using the stuff for over 20 yrs. My son and I used to build strip canoes... glass and epoxy clear coated in and out. Even when we stopped that and started traditional boat building there was still plenty of things to use it on. Now on bigger boats it's amazing.. the barrier coat is like armor.. the bottom paint scrubs off from river debris but the barrier coat is untouched even from the mooring buoy scuffing it.
just saying..
 
#31 ·
That's probably the worst looking bottom I've seen in 50 years--bar none. Squid, the first thing you want to do is get rid of that sander. The easiest and best thing I've come across for sanding a boat bottom is a tool used by sheet rock hangers for sanding spackle paste. It's a fairly coarse, stainless-steel screen fitted over a flat, cushioned pad attached to a relatively long handle. The screens and handle can be found at Home Depot, Lowes, etc..., the screens do an outstanding job, don't wear out quickly like sand paper, and you do the entire job wet. Just dip the head of the screen in a bucket of water, and scrub the bottom. The finish will be flat, smooth and ready to paint in just a couple hours. For some reason I thought everyone knew about this technique, but I guess I was wrong.

Good Luck,

Gary :cool:
 
#32 ·
I'll give the screen/pad a try to flatten things out on the next step when I fill and fair the bottom... I have the toolage here...

I don't think it would have worked on the ablative though, I needed the sander to "clean out" the divots without taking the whole hull down to fiberglass matt...

The divots were actually in the hull prior to ablative being applied as witnessed by the red ablative at the bottom of most of the "divots"... Looks like someone had ground out the blisters previously, but rather than fill just overcoated with the ablative...

Good news is there weren't any "new" blisters or soft spots forming in the 4-5 years the boat was in the water since the ablative was put on...

Here's an older photo from before I started, you can see the blister divots under the red ablative...

 
#33 ·
Squid,

I'm seeing red, white, blue and brown on your finished sanding. Lots of work, btw, nice job.

I assume the brown is where the blisters got into the mat. The red is remnants of the ablative, since you've referred to it.

I'm confused by what the porous white stuff is? Previous filler? Is it secure enough to apply over again? What's the blue?
 
#34 · (Edited)
The blue on that later picture is where I took off a larger rectangular screen box that was covering the brass sea screen seen..But it too was "paint" over the gray/white porus stuff, it just hadn't been sanded down in a previous "redo"...

What the white/gray stuff is ...I don't know...but it's been on there for awhile...although in most places it sanded out and "flaired back" nicely and seems "tightly attached".. a couple places (first pictures) show "air bubbles" in the mix, but they sanded out to tight material as well..

The only "history" I know on the boat is the PO bought it in the water 5 years ago and never had it out.. so everything we're looking at has been soaking for 5 years ... and/or "redone" 5 or more years ago...

The blister/divot/craters were "pre-ablative" and as far as I can tell no new blister/loose spots/cankers have developed under the ablative coating...

Also looks like in a previous "redo"... someone drilled and spot filled the blisters with another "something" seen as the perfect "yellow" circle in some of the blister craters...



I believe they predate the preablative divot creation...

Quite the premordial "chemical soup" I need to cover...
 
#35 ·
Squid,

Couple of semi-educated guesses here:

o The beige colored repairs in your most recent post look to be made with resin thickened with West System Microlight filler. It could be either epoxy or poly resin, but I'd guess epoxy.

o The "white chalky" stuff is likely a poly filler (Bondo or an equivalent) with white cream hardener.
 
#38 ·
o The "white chalky" stuff is likely a poly filler (Bondo or an equivalent) with white cream hardener.
I've never had much sucess with that "stuff". My earliest memory of it is my uncle scraping it out of an old car repair to redo it.

The few times I've tried it, may have been from it sitting on the shelf of an auto parts store too long, but I got the same results.

Once the benzoyl peroxide cream, (yes the same stuff you put on zits), couldn't completly harden the resin leaving me with scraping out a mess the consistancy of silly putty mixed with bubble gum.

I've had good luck with polyurathane, and with polyester. I would skp the bondo.
 
#36 ·
I would guess the yellow circles are some form of epoxy used to fill the early blisters.

I don't know how much time and money you want to spend on this, but you really dont want to kick the can down the road any more either.

Once you get it as clean as you can epoxy can fix a lot of past sins.

My opinion is if it doesn't leak, the surface is sealed, and the bottom is smooth after painting. You have a boat.

Regelcoating the whole bottom may not be what you want to do right now.
 
#41 ·
Regelcoating the whole bottom may not be what you want to do right now.
Don't EVER bother with that. If & when you decide to do the bottom properly, get it soda blasted or sand & scrape it down to a good surface, fill the blister divots properly with thickened epoxy, fair it up with orbitals and longboards then coat it with Interprotect per the manufacturers directions.

Presto changeo - a racing bottom! :)
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top