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post #3 of Old 12-09-2019
Jeff_H
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Re: Keel Damage Repair 1986 H40 Legend

If you have damaged a cast iron keel enough for it to be visible, then you have have probably done a lot more damage than simply the visible part that you can see. Cast iron imparts much higher stresses into the fiberglass than lead in a hard grounding. Most keel losses occur long after the initial hard grounding. The hard grounding typically weakens the laminate in the area of the keel and the bonds between the internal framing and pans. Over time the weakened structural components allow the damage to migrate into adjacent areas of the hull until ultimately there is a failure of the hull and the keel drops away. (A good case of this is the Cynthia Woods, and the Cheeki Rafiki incidents (Google them to find the reports). Both of these boats were built to a much higher standard than a Hunter 40 with much higher engineering and quality control measures in place than most production boats, and yet both lost their keels killing crew members after an impact that sounds much lighter than the one that you are describing.

As far as the repair, I would make the repair with lead rather than cast iron since lead is much easier to rough cast to shape and then do a final fairing on, and can be gotten for almost free from a shooting range. No matter which material you use, I would drill and tap the cast iron keel and bolt the filler piece in place. You should not try to weld to the cast iron since its very difficult to reliably weld to cast iron and there will be a void left behind the weld. I would probably bed the joint in either 5200 or thickened epoxy. I would cover it and the surrounding keel area in glass and epoxy and then fair with an epoxy based fairing material. (Or as an inferior but cheaper and easier material to work with, fair with a thickened vinylester resin and apply a barrier coat.)

Jeff


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