Chip off the old hull

[T37 Phil]

After haul out, I spotted a place around where the prop strut is attached to the hull and another along the bottom of the keel (shoal draft w/centerboard) where large chips were lifting up (1rst winter for me and this boat). It sort of reminds me of old paint flaking off of a house. The bottom has several coats of Interprotect and then Micron. Anywhere else on the bottom, I would just assume that it's many layers coming off together in slabs (paint held together, but not to hull). In that case I suppose I'd sand around it and reblend paint layers back up to thickness. On the other hand, it could be fairing compound with very little filler (cohesive, not powdery), in which case I might grind, refair, then sand and paint. I'm not really worried about the fractions of a knot lost if that part of the bottom isn't completely smooth, but I have this nagging feeling that I'm missing something about the proper repair.

I admit I don't have tons of experience looking at bottoms and diagnosing their problems (and of course kibbitzing about solutions), so I'm wondering in general, what thougt process do you go through when see a defect somewhere on your bottom (er, that is, on your boat's bottom) after hauling out for the season? What levels of attention are there between, argh, that can go another year, and, whew boy, grind down to glass and redo it all?

 

[Roger Long]

Due to forums like this a digital camera is now an indespensable boat maintenance item. You'll find it handy as well for sticking into odd places that you can't get a direct view of to do things like read and record equipment data plates. When not using if for maintenance tasks, you can stick it over the rail while sailing and have nice memory joggers for the long, dreary winter.

Later: Reading posts carefully is indespensable as well. I looked back after Maine Sail's post and see that the 10,000 words of information I was looking for was actually in there

 

[Maine Sail]

Phil..

Phil,

It sounds like a fairly common occurrence when the bottom paint is not "hot coated" over the barrier coat. When the barrier is allowed to kick for too long it needs a thorough washing, to remove amine blush, and a thorough sanding before the bottom paint is applied. Even this is sometimes not enough for long term adhesion. When doing a barrier coat job it is best to have access to an indoor shop or multiple days of good weather where you can hot coat (next coat applied before previous has totally kicked off) each layer including the paint layer..

Applying a barrier coat is tricky and many boat yards & DIY's fail to do it properly. The fix for your situation... Time and elbow grease. You could also try Pettit paints next time. I have had, as has the dealer where I bought my Catalina, and my current yard, better luck with Pettit Ultma SR for adhesion than the Micron CSC line..

 

[Roger Long]

Say, that brings up a question I wish I'd asked when you were in my boat shed. All around every area where there is bronze on the boat's bottom, there is a large area of blushing in the copper based bottom paint. These are large areas, extending out about a foot and merging together. I haven't been able to get a picture that shows it well.

It wouldn't look abnormal if not for the comparison. It may be a normal reaction between the copper and the bronze. This is the first year I've cleaned the bottom myself in the fall. I also changed from blue to red VC17 M last winter.

I plugged into shore power very little last year in the marina and had a big zinc fish hanging over the side at the dock and attached to the boat's bonding system. Both my shaft zincs were completely gone at haul out.

I wonder if I should be checking for a DC leak?

 

[Maine Sail]

Say, that brings up a question I wish I'd asked when you were in my boat shed. All around every area where there is bronze on the boat's bottom, there is a large area of blushing in the copper based bottom paint. These are large areas, extending out about a foot and merging together. I haven't been able to get a picture that shows it well.

It wouldn't look abnormal if not for the comparison. It may be a normal reaction between the copper and the bronze. This is the first year I've cleaned the bottom myself in the fall. I also changed from blue to red VC17 M last winter.

I plugged into shore power very little last year in the marina and had a big zinc fish hanging over the side at the dock and attached to the boat's bonding system. Both my shaft zincs were completely gone at haul out.

I wonder if I should be checking for a DC leak?

It is possible that you have a galvanic issue but with your zinc snake....? I'd check your bronze for any signs of dezinctification (turning a pinkish coppery color). If it looks fine and is uniform in color it could just be that when the thruhulls were rebedded/faired a PO used a fairing compound like Bondo that can absorb moisture??

 

[kloudie1]

Chip Off Hull

Be careful with this one, Phil.. The T-37's have had some blistering problems (as have many boats) and what you are seeing may be the barrier coat from a blister job.. Just a thought from having done a complete bottom blister job on a friend's T-37. Make sure that there is still some barrier between the fiberglass and whatever it is that you are looking at that is left on teh hull under the flakes..

 

[Brian D]

Wow, Phil! Hope it isn't anything major. I need to haul and paint and I am scared I will see blisters. Have my fingers crossed.

 

[T37 Phil]

I'll see if I can get a picture this weekend. I haven't seen any sign of blisters, but it never hurts to look again.