Part Five: Adding Fins
Just the wooden shape alone does not provide enough surface area to move the fish in the wind. Adding fins give the needed leverage to point the fish into the wind and react to small changes in the breeze. If you just want the fish as a static display with little movement, small or no fins will get you what you want. I am sure some aeronautical engineer could explain the dynamics of pressure on the tail fin, weight and drag to define the perfect shape and size to move the fish into the wind. For me, I have found that larger tail fins that extend above and below the fish appear to turn the fish into the wind and move with light winds.
Sheet Metal: Recall that you have been driving over the galvanized sheet in the garage for days now. Your tires and weight of the car have flattened the corrugations to a manageable flat surface. It is not too soon to start considering your use of muriatic acid to strip the galvy protection from the metal allowing it to rust and have a nice rustic appearance. I guess you could apply whatever paint on the fish and fin for whatever look you want. I like the wood tones of red cedar and rewood combined with rust patina on the corrugated metal for my application.
If you are considering muriatic acid to strip the galvy, go to the big box, sheetrock or concrete sections and find a big tub for mixing texture mud/concrete and buy some muriatic acid -- paint section. You will need that big area to lay the fins while the acid removes the galvy. More later. For now, consider the shiny, paint or rustic finish:
The The above show three different tail fin selections. NOTE: This is important. The corrugation ribs add some rigidity to the metal. Orienting the fin with the ribs horizontal to the ground assures the tail does not flex in the wind. If you want the tail to flap in the wind, then consider an articulated shape, hinge in the tail area to give some additional movement. Hinging could be a simple pin hinge allowing movement. That adds another dynamic to the shape, materials and wear. So, I am opting for simple. Finally, consider the lower/pectoral fins. They add some finish and scale to the fish. The above show one, two and three pectoral fins. The dorsal fin is a must IMHO.
This is an attempt at a Koi representation. Four pectoral fins, a BIG dorsal fin and a curved long tail. The tail has lost some of the rigidity from the shape. I have seen it deflect in light winds, nothing serious. The other fins probably assist in heading the fish into the wind. Muriatic acid and a rust etch to start the rusting. The glue line is visible in the middle of the shape. Wester red cedar, knots and all. The fish, wood alone is probably 44".
Next: Part Six the shape and installation of the fins.
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