Bimini Tops

Revised by BoatUS editors in April 2012

Boat - bimini topBimini tops can make a real difference in your boating comfort, protecting you from direct sun, wind, cold and rain. Depending on the type and construction, they can be easy to put up and take down for storage.

Which Material?

Cotton Duck

Inexpensive, but won't last as long as other fabrics due to UV degradation, and tends to leak.

Vinyl

These are actually vinyl coated fabrics (usually polyester) such as Stamoid, and are the most popular choice because they are waterproof and will divert water to the sides of the top for runoff. They are non breathable but easy to clean and high quality ones can be very durable. 

"Solution-Dyed" Polyester

Polyester, such as Top Gun, that is solution-dyed has an extremely rich color and holds up very well to UV-rays. Polyester tops are very strong and resist stretching so they retain their shape. They're more water repellent and abrasion resistant than acrylics, but will fade faster.

Acrylic

This top-of-the-line soft woven fabric, Sunbrella, looks and feels terrific. It holds up well to UV rays and has exceptional fade resistance and strength. However it is prone to leaking and will need to be re-waterproofed after extensive cleaning. Acrylic tops are usually more expensive, and may not be as abrasion resistant as others.

There are new and better products on the market every year.  Check with your canvas craftsman for the best. The more you spend now, the less you’ll spend later.  Labor is a very high part of the cost of a bimini top. There’s more to it than the material.

Threads:

The thread holding it together can be a very weak point in the system. Sun, UV, moisture, bird droppings and other elements can cause this to rot long before the material itself.  Use only high quality thread recommended by your professional. Typical polyester thread usually will have to be re-stitched before the fabric wears out. Now there are excellent, but very expensive threads available, such as Tenara, which promise to last the lifetime of the fabric. Check www.sailrite.com for information on thread and fabric.

Frames

Bimini top frames are available in aluminum and stainless steel. In freshwater environments, aluminum is probably adequate for your needs and much more economical. Aluminum tubing should be anodized to resist pitting and oxidation. Stainless steel is much stronger, will not corrode, and is nearly twice as expensive as aluminum. Plus, stainless steel's strength allows you to travel at higher speeds and it allows the top to withstand higher winds, so it's the ideal choice for powerboats. For saltwater applications, stainless steel is well worth the extra cost.

Tube size ranges from 1/2-1" OD; 7/8" is standard and provides plenty of strength in both metals. Whether the tubing is drawn or extruded has a profound effect on the strength of the tubing. Drawn tubing is pulled through the die process, giving it a denser consistency and more strength. Extruded tubing may have weak spots because it's pushed through the die process.

Fittings

Fittings that hold the tubes together should preferably be high quality stainless steel. Stainless fittings are more expensive than others, but are the strongest and most durable. Coated brass fittings are inexpensive but they have a tendency to corrode and peel and deform or break. Again, the more you spend the more you’ll probably save in the long run.

Helpful Accessories

Slide tracks allow you to install the top onto the track rather than directly onto your boat so you can slide the entire bimini to different locations. This also makes it easier to fold the top down in the optimal location when not in use. However the fittings connecting the tubing to these tracts often provide a weak point in the system.  Good tie down points and methods will help here.  Easily adjustable straps are important to “cock” the bimini if needed and to help secure it when you put it up.

Storage

Always take the bimini down for winter storage. Bimini tops should be cleaned, dried and stored whenever your boat is laid up for long periods. They should not be used as substitutes for a winter cover. Storm winds or snow load can destroy a bimini in a season. Bird droppings left on the bimini will quickly deteriorate the cloth and threads.

Cockpit Enclosure

You can entirely or partially enclose your entire cockpit or steering area with front, side and rear curtains which are attached to the Bimini and to the boat.  There are many methods for doing this, depending on the boat and its usage.  However, particularly with the use of heavy duty stainless tubing, with cross connecting tubes for additional strength, and quality hardware and material, you can provide yourself with protection almost as good as that obtained from an enclosed pilot house.  You will also add value to your boat.

There are various types of clear vinyl "see-through" material.  The less expensive is prone to scratch easily and crack with UV and age.  The more expensive such as Strataglass can last for many years. You can even use material for the front “windshield” that’s almost as clear and rigid as quality glass.  Ask your installer about what’s best when you do it.  Again, saving money here will cost more later because labor is a large part of the cost.  Take care to not fold or roll see-through material which has salt or other dirt and wash it off with fresh clean water before wiping it down with very soft cloth. If cleaners are available for your specific fabric, these should be used.

Zippers are usually used to attach curtains to the top. These are a weak point in the system. Do not use any metal zippers, even the zipper pull, as these corrode quickly in the elements. Most plastic zipper material will deteriorate quickly in UV, so make sure that the zipper is covered by a flap of fabric. If RiRi zippers are available to your canvasmaker, these promise to be much more UV resistant than the more common brands.

The method of attachment of the curtains to the boat can vary. Snaps, Lift the Dot and twist fasteners are commonly used.

 

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