Installing A Bimini

By Dan Armitage
Illustrations By: Marcus Floro

How to select and install a bimini that functions like a convertible top for your boat.

Boat with bimini illustrationThe fore and aft supports can be either additional poles, or webbing straps depending on preference. Straps make it easier to collapse the top into the down position, but aren't as rigid if you are going to be adding side curtains in the future.

Bimini tops offer boaters the flexibility of a convertible, combining shade and sun protection when we want it with the option of putting the top down when we don't. When fitted with side curtains, bimini top frames can also be used to create portable "cabins" to cut wind and water from the sides — yet be easily stowed when it's time to soak up some sun, catch a cooling breeze, duck under a low bridge, or tow the boat on a trailer.

The versatile tops can be made in practically any size to fit a variety of applications, and the supporting frames, or bows, can be mounted just about anywhere and are designed to fold out of the way. Basic bimini tops use support bows of aluminum or stainless steel with pivoting hinges that are anchored at the gunwales and held tautly in place by straps of webbing or rigid metal beams snapped to fittings atop the gunwales fore and aft of the pivot point. Here are the materials needed and steps to take to select and install a basic bimini top:

1. Determine Top Size

Measure the beam amidships where the bows will be mounted to the gunwale, which will determine the top's width, and note the height and length measurements you require, based on how much deck or cockpit you want covered and how much headroom you need. Keep in mind that the height, as well as width and length, and how much rounding down of the top you want will determine how much shade the top will provide. Stock or semi-custom, special-ordered bimini tops generally range from four to eight feet in length, with 6-foot-long tops being standard. Bimini bows can flex as much as three inches in or out where they attach to the gunwale, so there is a six-inch range that can be accommodated by generic tops to allow them to match most any trailerable boat's beam. These tops cost significantly less than custom biminis and come in a variety of colors.

2. Determine Top Position

Hold the deployed top in place and determine where the pivot point should be secured along the gunwale. It's important that those hinge points are exactly opposite and parallel to each other to keep the top from binding when folded. If there's no space along the top of the gunwale, you'll need hardware for side-mounting the deck hinges. When deciding where to mount the hardware, make sure the folded top will stow where it is out of the way. Check where the folded top will drop when it is in the folded, stored position. Most boaters stow their bimini tops in a storage cover, called a boot, across the aft end of the cockpit, but some frames are designed to fold forward to rest along the top of the windshield or across the bow. Make sure that there is enough distance in front of and behind the deployed top's support bows to mount eye straps or braces for attaching the angled straps that help secure the bows.

3. Mount The Bow Hinges

Put masking tape on the mounting surfaces and use the hinge hardware to mark the places for drilling holes. For the installation to be strong enough, you need to through-bolt the mounting bolts and secure them with nuts on the underside. Make sure the underside will be accessible and clear of wires and hoses. Drill and chamfer the holes
with a countersink to reduce gelcoat cracking and remove the masking tape. Apply marine-grade silicone sealant or butyl tape to the mounting surface and secure each deck hinge into place using high-grade stainless nuts and bolts.

4. Install The Strap Eyes

With the main bow secured to the deck hinges, deploy the top, and extend the fore and aft web straps to create an M-shape on each side. Doing so will show you where to mount the strap eyes, which should be mounted in the same plane fore and aft as the bows and directly across from each other along the gunwale port to starboard. Put tape down where the eyes will be secured, which should be oriented parallel to the gunwale. Mark, drill, chamfer, bed, and mount each eye using self-tapping high-grade stainless screws at the same position on each side of the boat. Attach the strap snap hooks to the strap eyes and use the buckles to adjust the top so that it is taut and the cover is parallel to the deck.

5. Test The Top

With the top deployed, operate the boat from low to mid-range speed, checking the frame and cover to make sure they remain secure. Adjust or tighten the straps to reduce flapping or shaking and to maintain headroom fore and aft. Note, most manufacturers recommend operating at speeds no more than 30 mph with the bimini top deployed. Stop the boat, stow the top, and perform the same test, making sure it remains in its stored position when the boat is underway. When the top's fit and security are confirmed in both the stowed and deployed positions, it's time to start enjoying one of the most practical accessories you can add to the family boat. 

Dan Armitage is a syndicated radio show host (buckeyesportsman.net) and outdoor writer, who leads seminars on boating and fishing.

— Published: Fall 2014


Secure Options

  • Tracks for securing the bows' pivot hinges are available for mounting atop or along the gunwale to allow the top to slide fore or aft for deploying, or for out-of-the-way stowing. You can even set two anchor positions for the top using a track and two corresponding sets of four strap eyes for each.
  • Aft braces are popular alternatives to web straps to support the bimini's main bow, allowing the forward web straps to keep the top taut. The rigid braces, usually made of aluminum or stainless steel and often with a telescoping feature, allow the top to be folded back in a semi-elevated position to keep aft cockpit space clear, and can be detached or collapsed to allow the top to be fully dropped to gunwale level for stowing or towing.
  • Quick-release pins, rather than bolts, are available for easy removal or positioning of the bow hardware and rigid aft braces to the deck mounts.
  • Protective zippered boot covers are offered to match each bimini top in color and size, and are recommended to protect the fabric when stowing or storing. These are a must when trailering to keep it from blowing open at highway speeds.

 

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