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Top-Gun
05-24-2010, 09:57 PM
In the process of prepping our 22 ZX for the season I came across something rather unsettling while waxing the hull. It appears that a number of nasty looking stress cracks have formed on the aft end of both of the inner strakes. There are also a number of fine spider cracks running parallel to the stringers and some parallel to the aft bulkhead:

http://inlinethumb10.webshots.com/44425/2102805040038916256S600x600Q85.jpg

http://inlinethumb45.webshots.com/45292/2955163010038916256S600x600Q85.jpg
http://inlinethumb64.webshots.com/32063/2864163720038916256S600x600Q85.jpg

http://inlinethumb32.webshots.com/47391/2774485220038916256S600x600Q85.jpg

http://inlinethumb59.webshots.com/46202/2786770440038916256S600x600Q85.jpg

It appears that the previous owner had this happen and had it fixed at some point (which they neglected to mention). I'm wondering what could possibly be causing these to form and what I can do to fix them? I plan on grinding them out, filling with West epoxy, and then topcoating with some gel but I know unless I find the root cause these will likley return. Any information is greatly appreciated.

thehow33
05-24-2010, 10:25 PM
i'm guessing you might need to add some support stringers near the motor.

VetteLT193
05-25-2010, 07:44 AM
stupid question because I can't see the whole hull bottom... are those standard strakes from the factory or are they totally added on? The pics make it seem like they might have been added on after the fact.

Top-Gun
05-25-2010, 09:44 PM
They're the original stringers, the one pic makes it look added on as this area was repaired once before. It looks like the previous owner had a decent repair done, the gel was sprayed on but its a slightly different color so that tipped me off. The gel is built up pretty thick making it look out of place. I intend on grinding this down and blending it nicer when I repair the cracks.

By support stringers, do you mean bracing the existing stringers to the transom or just adding to whats there already? The boats running a stock 454 mag with stainless marine manifolds, so its not putting out much more power than stock. I was concerned that I may have stringer or bulkhead separation or something serious going on but everything looks good from what I can see without cutting the floor out of it.

thehow33
05-26-2010, 08:45 AM
http://www.donzi.net/forums/showthread.php?t=60197
This is a thread that Trueser posted showing how he redid his.

And its not a stupid question:)

Trueser
05-26-2010, 09:35 AM
Looks to me that it was a previous repair that went bad.

rchevelle71
05-26-2010, 10:02 AM
Looks to me that it was a previous repair that went bad.

I agree,

He said the gel was thick, which can cause cracking on its own, but in one pic, ya see a rock chip or something similar, my guess is this is where it started.

RickSE
05-26-2010, 11:44 AM
I bet it's like mine, a putty problem. A lot of these guys grind the stress cracks out in the gel and glass then build the surface back up with putty before they re-gel. When they do this the surface is too soft and thick and just cracks all over again. As mentioned before the gel needs to be thin so it can flex w/o cracking. If you don't have cracks inside the hull then it's probably not a structure problem and is only the finish coats on the bottom of the hull. Either way it's going to have to be opened up.

The guy who fixed mine after the previous repair went wrong, ground everything out again, built the surface up with glass then re-gelled the bottom. Funny thing was that he knew it was a putty problem even before he opened it up.