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Garboard plank replacement..
Posted: Tue Mar 09, 2010 1:51 pm
by 240sxguy
Okay I am not dealing with rot but need to remove my garboad plank on at least one side of the boat due to it sagging from sitting on a trailer. The wood looks somewhat damaged an I want to replace it.
Now, looking at it.. it appears I can just flip the boat, cut and remove fasteners and replace the entire piece. Is this my best bet?
I am sure it will make more sense once I really tear into it.
Thanks guys.
Evan
Posted: Wed Mar 10, 2010 1:44 pm
by thegammas
There are others on this site much more qualified to reply than I, but of course I will reply anyway
Very typical for a hog (concave) section to form in the garboards after a wooden boat sits incorrectly on a trailer for a period of time. Usually the bunks aren’t extended past the transom, and the weight of the motor presses the bunks up in to the bottom deforming the bottom shape over time.
Sadly, I have this problem and it does indeed affect handling.
I would suspect that you cant resolve the hog by simply replacing the garboard panel. The structure, frames (ribs) and maybe keelson and sister keelsons, are likely also warped out of shape, and a new panel will just follow this shape.
If the hog is not too bad, maybe you can fill and fair it out to the correct shape (this is my plan). Or, perhaps you can remove the panel and add new structural material to achieve the proper shape (ex: laminate on new wood to the warped ribs, fair it out to the shape needed).
Posted: Wed Mar 10, 2010 1:48 pm
by 240sxguy
Peter, you are very correct in that the ribs are deformed as well. Only one side of the boat really appears to have taken a beating from sitting on the trailer so I had planned on copying the ribs from the side without the hogging.
Yes, this is much too bad to fair out with epoxy or anything of that nature.
Thanks.
Evan
Posted: Wed Mar 10, 2010 3:50 pm
by txcaptdan
This is one way to correct this I believe, I have done this on one hull. Unscrew fasteners that go through garboard into ribs and also the next lap up depending upon size of hog. There is a screw at each lap and sometimes a screw between lap joint and keel, or possibly into sister keelson. I would release all in area of hog and a couple of ribs forward and back. The laps can be pushed away from the ribs fairly easily at this point.
Make some white oak blocks, the same width as the ribs, of different thickness, lengths and shim under ribs between laps at screw holes. This will push out laps to correct shape. Pilot drill holes through new shims and replace screws into ribs through blocks.
The problem is the the ribs are deformed and will not return to correct shape easily, this way you can leave ribs alone and push laps out to correct bottom shape. This method takes some experimenting with block thickness and how many ribs need to be shimmed to get correct shape.
I did this method on a 14' hull and balanced one side to match the other.
Posted: Wed Mar 10, 2010 5:35 pm
by 240sxguy
Seems like a good idea as well. Once I get this thing flipped I had best take some photos.
Evan