Shrimp trawl doors also known as otter doors or nets, are an essential component of shrimp trawling operations. These specialized doors keep the mouth of the trawl net open as it’s dragged along the seafloor allowing fishermen to catch more shrimp. While ready-made shrimp trawl doors are available for purchase, many fishermen prefer to build their own. Custom doors provide an opportunity to optimize the design for your specific fishing conditions.
In this comprehensive guide, we’ll walk through the entire process of constructing shrimp trawl doors step-by-step. Whether you’re a seasoned fisherman looking to upgrade your gear or just getting started in the shrimping business, this tutorial has everything you need to build effective trawl doors from scratch.
Step 1: Choose Your Materials
The foundation of the trawl door is the frame, typically made from marine plywood, planks, or aluminum plates. Plywood is affordable and easy to work with. Hardwood planks make a sturdier frame that can handle higher stress. Aluminum plates are more expensive but extremely durable, especially in saltwater.
In addition to the frame you’ll need
- Angle iron or steel bar for weight and reinforcement
- Rubber discs, tires, or high-density plastic to reduce drag
- Bolts, nuts, washers, and epoxy for assembly
- Paint or wood sealer for weatherproofing
Pick materials suited for your fishing conditions. Areas with small shrimp and gentle currents only require lightweight doors. Heavy doors are needed to maintain spread in areas with large shrimp, strong currents, and soft bottom.
Step 2: Cut and Shape the Frame
Cut your plywood, planks, or aluminum plates according to your design plans. Most shrimp trawl doors have a rectangular or triangular shape, but specialized curves and edges can improve performance. Diamond, elliptical, or circular edges may cut down on drag. Just ensure the completed frame is symmetrical to swim properly.
Before final assembly, seal all wood surfaces with epoxy. This prevents water damage and makes the frame stronger. Next, pre-drill holes for mounting the angle iron or steel bar. Drilling the holes now makes installation easier later.
Step 3: Add Weight Along the Frame Edges
The angle iron or steel bar provides ballast to keep the net open horizontally. This weight must be precisely calculated based on net size and fishing conditions. Too little weight won’t hold the net open. Too much will overload the cables and winches.
Position the ballast along the outer edges of the frame. The front edge often has lighter material to reduce resistance while trawling. Heavier ballast goes along the sides and back to counteract spreading forces. Epoxy and bolt the ballast securely to the frame.
Step 4: Attach Rubber Discs for Reduced Drag
Rubber discs, cut from used tires, are mounted on the front corners of the doors. The smooth, rounded shape allows water to flow around the door with less turbulence. Reduced drag and friction means less strain on the cables and engine.
Carefully center and align the holes in the rubber disc with the pre-drilled holes in the plywood frame. Use oversized washers and tightly bolt the discs in place. High-density plastic can also be used instead of rubber for lighter weight.
Step 5: Add Finishing Touches
With the main assembly complete, add any final reinforcements and flourishes:
- Extra epoxy/varnish protects from moisture damage
- Paint or bright colors aid visibility
- Reflective tape improves detection on radar
- Identification numbers help track gear
- Floats can be added for buoyancy
Getting creative helps your doors stand out on the fishing grounds. But avoid anything that adds excessive drag or weight.
Step 6: Rig the Bridles and Cables
The bridles connect the trawl doors to the towing cables at the proper angle. Adjusting bridle length and height is key to achieving optimum spreading performance.
Bridles are typically made from chain, wire rope, or a combination of the two. The front bridle is shorter and mounted higher on the door. This tilts the door outward as it’s towed. The rear bridle is longer and lower, providing leverage to open the net.
Use galvanized hardware and swivels at all connections. Stainless steel won’t corrode as quickly in saltwater. Careful rigging prevents fouling that can ruin a trip.
Step 7: Test and Troubleshoot Your Design
Before relying on new trawl doors for critical fishing trips, test them under realistic conditions. Drape a net between the doors and tow them fully submerged to simulate trawling. Pay close attention to:
- How the doors spread and hold the net open
- Stability while towing and maneuvering
- Amount of drag on the cables
- Any signs of excessive strain or fatigue
Make adjustments and reinforcements to address any issues observed during testing. Small tweaks to the bridles or ballast often improve performance. Testing identifies flaws in the design before they become catastrophic failures on the fishing grounds.
Constructing effective shrimp trawl doors requires precision design, quality materials, and proper assembly. But the effort pays dividends for decades in the form of bigger catches and more efficient fishing. Whether replacing worn-out doors or expanding your fleet, building your own doors allows complete customization for your needs.
Shrimp – Cambered Doors & Super Fibers
What is a shrimp trawl net?
Recreational shrimp trawl net consist of long, open at both end, nets with a wide mouth that has two “doors” or “trawl boards”, which are solid metal and wood wings that serve to open the net so shrimp can be gathered up as the boat is slowly motored forward. Quality built trawl boards should last you a good long time.
How do trawl doors work?
Correctly rigged, the trawl doors keep the mouth of the net open by operating at an outward angle from the direction of the tOVled trawl. This angl e varies between 300 and 400 (fig. 2). If a tra”l-Tl net is improperly assembl ed, the twine in the net webbing will be subjected to uneven strains.
How wide is a shrimp trawl net?
When it comes to rigging the boat for a shrimp trawl, Ishee advises, “A shrimp net is measured across the front of the net, so a 16 foot net is 16 feet wide. Most people pull a ‘super 16’ net which has higher wings- the sides of the net.
How is a trawl door made?
The ground ·Hires are held by a figure- e link at the trawl-door rin E; stopper . The door end is made upon a stud from a 5/8 inch comcination wire rope 6 feet in length w~th an eye splice in each end. Gften a roller chain is spliced in one end end fastened by 2. sha~le or reeved through the eye splice .