What did I do wrong?

[vindo40]

There was an instrument here. I cut a piece of plywood and filled the hole. Then I filled the cracks with the product in the pictures above. Afterwards, I sanded and painted the surface. One year later, the cracks started to show up. What went wrong???

[CharlieJ]

Your pictures are too small for these old eyes to see, but I'd guess shrinkage of the filler. You didn't mention putting any glass over the surface. If I use ply exposed on the outside of the boat I ALWAYS add at least one layer of cloth over it. Stops those little cracks around the edges and stops any checking from happening in the plywood.

My two cents based on a guesstimate

[vindo40]

http://images.kodakgallery.com/photos45 ... _0_ALB.jpg

[vindo40]

My fault or filler????

[Rachel]

Edited to say: I assumed you were patching fiberglass, but perhaps it's all wood and you want the bright wood showing on the inside of the cabin? If that's true, I'm not qualified to comment, but if it's fiberglass, or wood-and -fiberglass type construction, then this should hold true:


I wouldn't say the filler failed as much as the process wasn't quite right. Wood and filler alone just won't do the trick in an application like that.

Really, you might be better off without the wood. But whether you use wood, or a build up of fiberglass layers, or a disk of prepped, pre-formed fiberglass, the rest of the procedure is similar:

Basically, you want to use cloth and resin to make the of the patch (this can include some kind of disc if you need the thickness, but that's not necessary), and then the "filler" (or fairing compound) is just used to smooth it out cosmetically. So you've got the inner bulking layer, and the cosmetic filler, but you don't have the actual patch that you need for strength (in this case not strength that you need to hold your cabinside together; but strength that you need to keep the patch from "breaking out").

I'm just typing a long-winded version of what Charlie said, really. But it boils down to the fact that you want to use resin and fiberglass cloth (woven cloth, biaxmat, or etc.) to make the repair, and then just use the filler to smooth it out before you paint or finish it.

If you look up how people have filled in small machined holes (i.e. old through hulls) you'll get the basic idea (there are several threads here), although the ultimate strength/failure of your patch isn't quite as critical since it's above the waterline.

Rachel

[Tim]

Don't blame the product (though I know nothing personally about the product you used and wonder if it's polyester-based); it's the process, in this case. The others have summed it up pretty well. The products are the secondary cause of concern here since the process was basically flawed.

To fix this, grind it back a bit past the cracking, and create a tapered low area deep enough and wide enough to allow you to apply some fiberglass reinforcement over the patch--a layer or two of cloth is adequate for this sort of thing where the patch is essentially non-structural. Then, fill and fair it smooth with the surrounding areas, and paint.

Patching a piece of wood--plywood or otherwise--into a hole like this without the overlay of fiberglass to protect and reinforce the area is guaranteed to fail eventually because of movement of the wood and other factors. Even plywood is subject to the natural movement of wood. The plywood is OK to fill the bulk of the hole the way you did, but unless you tie it into the surrounding areas with fiberglass reinforcement (which also protects the wood from the elements), this sort of cracking will occur every time.

If the area containing the patch is entirely made of wood, then there may be other factors to consider in terms of patch failure and how to fix it now. We're all just assuming it must be a fiberglass boat, I guess.

[vindo40]

OK I got it.....
Thakns

Tim, what happend with the pictures I posted ? They are gone !!!

[Tim]

Tim, what happend with the pictures I posted ? They are gone !!!

This problem is common with the photo hosting sites. If you right click on the image icon and select "view image", then the photo will show up in the forum, in this case at least. Sometimes the photos just disappear for no apparent reason.

I have no idea why this happens with free image hosting sites, but it often does. It's an issue with where or how the photo is hosted and not related to how this forum works, so there's not much I can do about it, unfortunately. All I can do is suggest another outlet for your photo hosting, like a personal website or some such.