Bottom Paint (Fresh water Lakes)

[tidalwave]

Last year when I bought my 26M, there were forum discussions about whether or not a Mac HAD to have bottom paint to protect the gelcoat when kept full-time in fresh water.

I kept LOKI for just two months in Mille Lacs Lake, here in Central MN...
I had put six coats of Poly-Glo wax on before launch...

I found out this spring that more than ten square feet of the gelcoat on the hull had developed small osmosis blisters...which has now cost me
a small fortune to have sanded out.

I am now in the process of applying two coats of Interlux Epoxy to protect from further water damage plus three coats of anti-fouling paint. The Interlux company has quite a few reports of blistering of unprotected hulls kept in Minnesota lakes.

The marine painting shops in this area have found that fibreglas hulls kept more than one month unprotected in Minnesota lakes will almost certainly develope osmotic blistering...they aren't certain what is in our fresh water lakes chemically to do so much damage.

So if any forum members are planning on keeping a new Mac at a marina here in MN...get the bottom protected BEFORE you ever launch...you will save a lot of headaches and cash!

[zuma hans 1]

Osmotic blistering? Wouldn't a sacrifical zinc plate or three prevented this?

[Chip Hindes]

Scarificial zincs are to prevent galvanic corrosion. Osmotic blistering is a completley different chemical reaction and neither has anything to do with the other.

[March]

I had a similar problem keeping the Mac on a local lake. After several months, the bottom got covered with some greenish gung, of biological origin, one might hope. It became harder on the sides (I suspect where the light still managed to hit it, so the stuff might be photo-sensitive) less hard on the under-belly. It still took forever to scrape it off, at the end of the season. Didn't notice any blisters, though.

Now here's the weird part. I had patched some scratches with marine Tex epoxy (can't remember the correct name, amazing stuff though that I couldn't live without) and appplied some scotch tape over to keep the patches smooth before they hardened. Forgot to remove one stretch of taape--it was still there at the end of the seaason, and I could peel it off easily... and no gunk under that patch!

The idea of covering the whole bottom with wide scotch tape appeared as a natural infernce. The gunk doesn't stick to it, and peeling it off at the end of the season is worth more than cleaning the entire bottom.

It still sounds like too crazy an idea to try... or not to try?

If the stuff sticks, there would be no reason to expect exfoliation and messing up the ecology of the lake....

[DLT]

Sweet! So where can I get some scotch tape in foot or more widths?

At first, I was joking...but the more I thought about it (yeah, I know - dagnerous) it seems like a decent idea, at least for the water line... You could keep the ring at bay...

[ChrisNorton]

I would like to say for the record on this subject that botton epoxy and anti-fouling paint are a MUST IMHO on any body of water for boats left in for more than a couple of weeks...period!!!

I grew up on the Great Lakes (fresh water) and now sail on salt. For salt this is a given (unless your a racer and pay a guy to scrub it every week)but unless you enjoy serious power washing everytime you pull your boat to get rid of the green algae slime that grows in nearly every body of fresh water and then sanding the blisters from your bottom from the osmotic reaction, put an epoxy barrier and bottom paint on your boat. The type of material you use will depend on the type of water and your location (sub-tropical vs. northern waters). IMHO, I use high-cost yet highly effective Micron Ultra or Extra bottom paint over my epoxy barrier coat at $160 a gallon. Believe me, it is worth it. The ablative properties prevent sanding from season to season and the anti-fouling chemicals work perfectly.

Again, this isn't necessary for boats that aren't kept in water for extended periods.

[Dimitri-2000X-Tampa]

I've kept boats in water for years in a canal that lines up in a perfect East-West orientation. This means one side of the hull faces South and the other faces North. The side on the South where it gets more light always had thicker growth on it than the North side. Not sure if same applies to fresh water fouling, but I would guess it may be the same.

[Lorne Colish]

Both my Macs,a1988 26D and now my 2002 26X, developed osmosis sitting at the dock in freshwater before being repaired with a barrier coat and antifouling. So I emphatically recommend protection for those in similar situations.

[Night Sailor]

Where were you guys last year before I put my wax only X bottom in the lake for a year?

On the advice of a few on this forum I used only three coats of wax. Today after pressure washing and scraping the bottom i found dozens of blisters. So, I'm now convinced that at least in hot water lakes (it hit 86 degrees last summer) in TX, barrier coat and bottom paint is a necessity. I have no place to do it at home, so it's going to be an painful expense I had hoped to avoid this year. Thee goes the chance for that new S1 wheel pilot I had my eye on.

The good part is I think the X looks better with a nice black botom job.

[MAC26X]

I have a 2001 X that has spent the summers in my slip on Lake Erie since 2001. We use VC offShore, 3 coats first year, touchup second year, recoat alternate years. I have never done the barrier coat. I have had no problems with osmosis or bubbles.