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Styrons 15' Tunnel Hull
Note the sweep of the bow, decreasing planing area, although great for getting through vegetation in shallow water when planed.
Sweep of bow. We're talkin' flat bottom here. Well, I didn't buy her for offshore, you know...
Old, worn and nasty carpet. Where it wasn't worn through, the glue seems to be 3/16" thick. The carpet glue defies all chemical removal systems. Elbow grease, here we go...
Carpet and glue has been removed, aluminum sanded and ready for primer. The aluminum floor is riveted to the stringers. After several years of hunting, fishing and shrimping, some of the rivets are loose. SS screws with threadlock were used to tighten the floor up and reduce rattling.
Bow storage is open inside all the way forward with no floatation. A bulkhead will be added inside so foam can be added to very front.
Bulkhead is 1/2" treated plywood fastened to aluminum angles with SS screws and washers (don't forget the Threadlock). The edges were sealed with aerosol foam. Polyuretane foam (2 part, 2 pound) was poured into the void, creating approximately 250 pounds of floatation/displacement.
Note the space under the seat as evidenced by the gas tank below it. A bulkhead and bottom will be added to contain floatation foam, while allowing water to pass below for drainage.
Space under seat was utilized for floatation by adding a 1/2" treated plywood bottom attached to the tops of the stringers. This allows water to pass through below. Also, as shown in this photo, is the vertical bulkhead to complete the enclosure. Foam was poured into the holes for the seat mounts. These small holes created quite a challenge to keep up with the rapidly expanding foam. Approximately 320 pounds floatation/ displacement was created.
Transom configuration. Tunnel is 5"ht. x 9"w, tapering to zero about 5' forward of the stern.
This portion of the project was designed to solve several issues: 1. Add floatation: The pods are constructed as tanks and pressure tested, then welded to the transom. Approximately 140 pounds floatation/displacement was added. 2. Add planing surface to reduce or eliminate porpoising and aid in planing in shallow water. 3. Provide dog platform for waterfowling. 4. Provide steps to get back into boat for dogs (or people). 5. Every good yacht has a party platform!
Note the tunnel at the transom. The tunnel as designed was ventilated, which I don't understand, as air is introduced where a channel of water is being created, thus causing cavitation. The ventilation hole was welded shut when the pods were added. The skeg protects the OB and helps keep out weeds, sticks and small logs.
Note the prop position relative to the boat bottom. With new pods, the boat now floats dead level, with the water line just below the top of the bottom step. Sea trials in Galveston Bay proved porpoising was eliminated. The boat was tested with just me, a half tank of gas and a bottle of water in it. One side issue arose in that the Merc 40 is too much power for that light a load-especially going upwind. The bow came up on me...
Carpet removed and Durabak Roll on liner applied. Beige (sand) and grey were used. The product was very easy to use. Be sure to mask areas not to be painted and wear gloves, as it sticks to everything! Aluminum deck was sanded to bare metal, washed with water, then washed with a 50/50 water/vinegar mix. Then a zinc chromate primer was applied. The first coat of Durabak was applied within 12 hours, starting with the grey trees, then beige background. Two coats of each were applied. The smaller branches were painted after 2 coats of both colors were built up.
This Doel Fin was put on the OB to reduce porpoising before adding the pods, and it worked great. The boat still needed floatation and quicker planing, so after much thought, sketching and considering other ideas, the pods were added.