Dorade Base-plate Replacement
The base plates for our dorade boxes were deteriorating. The plywood was damp and spongy in areas. The screws that hold the dorade boxes to the base plates were not holding well. We considered repairing the base plates in place but decided to replace the plates instead. The major decision for us was whether to use teak or a plastic wood such as Starboard for the base plates. We decided to use 4-quarter inch teak.
Each base plate was replaced using the following process:
1. The first task was to measure the original base plates and have the 4-quarter inch teak milled to the correct size and angles. The location of the holes and drain channels were transferred from the original base plates and cut with a combination of hole saws, saber saw, and router. The bottom side of the base plate was fit to the curvature of the cabin roof using a belt sander after removing the original base plate.
2. Ten (10) screws were removed from each base plate. The heads or the screws were sunk approximately 1/8" under the surface of the base plate and appeared to be filled with caulk. Eight (8) screws are located about one inch away from the 3" air tube that enters the cabin. The other two (2) screws are located about 1-inch in from the rear corners. After removing the screws, putty knives were carefully driven under the base plate to break the bond between the bottom side of the base plate and the cabin roof. The bonding material was a relatively soft black rubber sealant of some kind. After removing the old base plates, the remaining sealant was removed using acetone, putty knives, and scrapers.
3. The original air tube was separated from the old base plate and was thoroughly cleaned with acetone. Be aware that the a material similar to oakum was packed in between the old base plate and the air tube. We choose not to use the material when replacing the base plates.
4. After verifying the air tube fit properly between the base plate and the cabin roof, the bottom side of the base plate was sanded with the belt sander to improve the fit on the cabin roof. When everything fit properly, the location of the ten (10) screws were transferred to the new base plate by using a paper template. A piece of paper was placed on top of the cabin roof and taped down. The air tube hole was cut out of the paper, then the base plate, with air tube in place, was placed on top. The edges of the base plate were marked on the paper to be used for future alignment. The base plate was then removed and the holes in the cabin roof were located and poked through the paper template. After all holes were located, the paper was removed from the cabin roof and taped to the bottom of the base plate using the lines that were previously marked.. Holes were drilled through the base plates where the template indicated and the top of the base plate holes were countersunk to allow the screw heads to be sub-surface and filled Finishing nails were then placed into the holes in the cabin roof which served as alignment pins to verify the base plate fit properly. The location of the cowl vent hole and drain channels were marked on the cabin roof so they would not be filled with sealant in the next step. The cabin roof was masked off around all edges of the base plate to allow the bedding material to flow out and be removed in the next step.
5. Final assembly was accomplished by caulking the lower section of the air tube with 3-M 101 sealant before it was inserted into the cabin roof. After the tube was in place and properly oriented, the cabin roof and next section of the air tube was caulked with 3-M 101 sealant (be sure NOT to caulk the area where the drain channels and cowl vent hole are located). The new base plate was placed on top of the sealant and screwed firmly into place.
6. The air tube was caulked once more around the top of the base plate where it meets the air tube. A large bead of 3-M 101 sealant was placed around the joint and smoothed out with a wetted finger to look similar to the joint on the original base plate. The masking tape was removed and the area was thoroughly cleaned.
7. The next day, the ten (10) screws were tightened to further compress the sealant between the base plate and cabin roof. The heads of the screws were covered with wood filler. The dorade box was placed over the base plate and pilot holes were drilled into the edges of the base plate for anchoring the dorade box in place.
We did not finish the teak base plates, believing that it would not improve the job and might contribute to holding moisture or causing the areas with sealant to loose their effectiveness as the finish deteriorates.