what are stringers on a boat

What Are Stringers on a Boat?

Written by Boatsetter Team
November 11, 2021

Stringers are part of the structure of a boat. They can be made of solid wood, plywood, fiberglass, or a combination of wood and fiberglass. On completely wooden boats, stringers are usually painted or sealed with varnish or epoxy. In contrast, stringers on fiberglass boats are generally wood encapsulated in epoxy and fiberglass.

Even if you can keep water from penetrating your boat’s stringers and frame system time, stress and water penetration can cause a stringer to rot. When boat stringers develop rot, they become weak and compromise the integrity of your boat’s hull.

If you own a boat or consider purchasing a boat, a rotten stringer can be expensive. A handy boat owner may be able to fix the problem. However, for most of us, replacing a part of or an entire stringer is beyond the skill set of many boaters.

What is the purpose of stringers in a boat?

Stringers are longitudinal forms that are laid in line with the keel to add extra strength and structural support to the boat. Along with the boat’s ribs and bulkheads, the stringers form a grid that holds up the boat’s decks (floors) and stiffens its hull. Stringers are somewhat like floor joists and traditionally are attached to the boat’s ribs and bulkheads. So, if they are weak, your boat is, too.

what are the purpose of stringers

Some boats don’t have ribs or bulkheads due to modern construction techniques. However, they will still have stringers to support the floor. Stringers are made of wood in wooden boats and of wood, or fiberglass encapsulated wood in fiberglass constructed boats. Newer pre-fabricated boats often have stringers constructed of fiberglass only.

Many essential items are attached to boat stringers, besides your boat’s decking. The inboard engines of boats are mounted on stringers, as are other boat components in some boats, so they need to be solid. Stringers are an integral part of your boat’s hull and overall structure, and if one is rotten, you have a problem. As with any boat maintenance, the sooner you find an issue and make a repair, the better.

How do you know if your boat stringers are bad?

Brown spots on stringers, where water is weeping from the inside out, are a sure sign you have a weak or rotten boat stringer. It is easier to detect a rotten stringer made from only wood. You can easily see any rot or cracks in the bare wood and catch a waterlogged stringer quicker than one sealed in epoxy or fiberglass.

It can be challenging to determine if a wood stringer encased in fiberglass is rotten. One thing to look for is impact damage, just as you would with a wood stringer. Suppose the fiberglass encasement of a wooden stringer is cracked or broken. In that case, you need to inspect the location further to be sure there is no rot beneath the fiberglass.

You can inspect a stinger by drilling a small hole through the fiberglass into the wood core. If the wood shavings coming from the drill bit are wet or rotten, you need to probe a little deeper to determine if you have a problem. If you do take this approach, reseal the holes you drilled so that water cannot penetrate the stringer at this point.

Another indicator of a rotten stringer can be a soft spot in the deck, delaminating fiberglass, age, the quality of the original stringers, and a bilge that stays filled with water. However, weak spots can also be an indication of rotten deck material over the stringer. In either case, the rot needs to be repaired, and upon moving the rotten decking, you may find that the stringer it is attached to also needs attention.

Can you replace part of a boat stringer?

Yes, you can; however, it is best to replace the entire section of the bad stringer, if possible. Stringers, as part of the hull, are under a lot of stress. Replacing only part of a stringer may not be strong enough to handle the stress of pounding waves, the weight of your boat, and its contents. 

Again, however, it depends on the size of your boat, and a craft with inboard engines, with a rotten stringer, needs an entirely new stringer.

Whether you replace part of a boat stringer or its entire length, it needs to be replaced with the same wood type used originally. For example, suppose your boat’s stringers are wood encapsulated in fiberglass. In that case, you need to use wood with the exact dimensions as used originally, and you should apply fiberglass at the same thickness as before.

Whether you replace your boat stringers yourself or have them done by a professional, the work being done should follow the original construction as closely as possible. It would be best if you fit the new stringer in the exact location as the old one.

Unless you keep your bilges dry, wooden boat stringers will eventually develop rot. Therefore, you should keep your bilges dry and repair any fissures in stringers with fiberglass casing as soon as they form. By doing so, you can keep water from penetrating the wood beneath, ensuring that these repairs need to be done later rather than sooner.

How much does it cost to fix a stringer on a boat?

The cost to fix a boat stringer is dependent on the size of the boat. It also depends on how the stringer is constructed. For example, boat stringers can be wood only, wood that has been fiberglassed, or stringers can be made entirely of fiberglass.

The estimate to replace a boat stringer of any kind is around $1000. The cost can hit the sky if you are replacing a stringer made of composite material or if you have a huge boat.

Boat maintenance is expensive. A repair such as a rotten stringer requires someone with the expertise and knowledge to make a repair that will restore the integrity of your boat’s hull. This type of repair is expensive and is one of the costs of owning and maintaining a boat.

On large boats and boats with an intricate stringer, frame grid system, the cost to replace a full stringer can run over $10000. For some boats, that cost may exceed the vessel’s value, and unless you love the boat, you may find that the cost for repairing its stringers, transom, or decking is not worth the cost.

Learn how you can help pay the cost of boat maintenance!

Every aspect of owning a boat has a price. From the cost of buying it to keeping it ship shape and ready for a day’s adventure on the water. Would you like a bit of help with offsetting the costs of owning your boat? At Boatsetter, we have helped boat owners worldwide list their boats with us and rent them to those who would like to go boating near you.

Many boat owners only use their boat occasionally, and renting your boat to other water lovers will help you and them. With Boatsetter, you have the option of a bareboat or captained rental. So, you can go along and captain a trip in your boat while being paid. Or, you can send your boat off for the day with others who wish to enjoy a day on the water, too.

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