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Keel Cavity Repair
By Rex Miller (Shadowfax II, #165)
Shadowfax Too, Renegade #165, was launched after replacement, using U.S. Paint products, of the failed Interlux 3000/3001 barrier coat. Since I am contemplation possible approaches to recovering some of the over $6000.00 this, in my opinion, product failure cost me I will defer that topic to another time.
Of interest to Renegade owners was the discovery of a large quantity of water in the keel weight cavity. As you are aware the lead keel weight is encapsulated in the forward half of the keel. This space is not a tight fit for the weight so Pearson put a bed of sawdust in the bottom of the cavity and scraps of end grain balsa around the sides to secure the weight. Over time water fills this cavity with the resultant deterioration of the balsa and potential damage to the hull and keel structures in climates where temperatures fall below 0ºC.
I detected the presence of water in the keel cavity using a moisture meter I purchased to test the overall condition of the hull. This was subsequent to Interlux's divinely inspired proclamation that the hull was saturated, as the Interlux representative did not have a moisture meter to assist in making this judgment.
Not wanting to leave the situation untreated my approach was to open the area by drilling 24 to 26 1-1/2" holes in the forward section of the keel on both sides. I kept the plugs for use in closing the holes after refilling of the cavity had been completed. The size selection is the diameter for my vacuum hose end so I could use it as a plug cutter. What I could not get this way I broke up with a bent steel rod moving the broken pieces towards the direction of vacuum nozzle in an adjacent hole.
The removal process took an entire day. If I were to do this job again I would cut some larger holes to facilitate easier access to the interior of the keel. I then left the area open for a couple of weeks during which time I would periodically attach the vacuum to drawn air through the area to assist drying. I would not use an air compressor to blow air in unless I had a very good water separator.
The next step was to fill the void with closed cell expanding "Froth-Pak 12" foam. I purchased this material locally, as it was substantially cheaper than from Defender Industries. Contact Froth Pak to find a local distributor.
Working from the bottom up I decided on a fill plan and taped over most holes only leaving open ones where I was going to blow in the foam. Over fill is not a problem because it is easy to clean away spill once the foam has cured. The first step in closing the holes was to remove some of the foam and clean the laminate to allow good bonding of the repair epoxy. I worked the 1-½" hole saw in the holes to clean the sides of the holes. Mixing a heavily filled resin I spooned it into each hole followed by inserting a plug so it was approximately level with the original surface.
This was left to cure over night. The next step was to grind out the hole areas to get a good bevel to lay glass cloth squares in. Then 6 or 7 layers of glass cloth and resin were applied over the plugs. I did not attempt to build the center of the ground out areas to the original surface height, just to have a suitable structure of glass laminate over the plugs. At the edges of the hole areas there was over build. Again, once suitably cured the over build was ground down to the original keel surface.
The next step was to fair any hollowed areas with 3M Blister Repair compound and re-sand to remove over-fill. I have found both the 3M underwater Blister Repair pastes to be excellent products. Once the above work was completed all that was left before launching were the laborious tasks of prime, barrier coat and anti-foul painting the hull.
Suggestions to assist effecting repairs: Use a Stud Finder to locate the vertical partition in the keel. Drilling large holes in the wrong section of the keel creates unnecessary work while exercising ones expletive vocabulary. When drilling at in the bottom areas of the keel set the guide bit of the hole saw very shallow so you don't drill into the lead too much. Do not drill too far down the keel. (See pictures) The weight is a tight fit at the bottom of the cavity so very low holes will have little use. The laminate is also very thick in this area and it is possible to jam the saw in the laminate/lead structures.