Installing Pedestals In Aluminum Boats: A Step-By-Step Guide

Installing a seat base pedestal on an aluminium boat is a challenging task that requires careful consideration and planning. The process involves drilling holes for mounting hardware, but the toughest part is achieving perfect alignment to avoid crooked screws, which can lead to a leaking deck. It's crucial to determine the position of the seat base for comfortable steering access and to assess the decking material and underlying structures. DIY boaters often face the challenge of deciding between screws and bolts, considering factors such as decking thickness and the presence of supporting structures. Proper installation techniques, such as using backing plates and washers, are essential to ensure the pedestal can withstand the exerted force without damaging the boat's floor.

Drilling holes for mounting hardware

Drilling holes in aluminium boats for mounting hardware is a common task for boat owners. Here are some detailed instructions to ensure a successful and secure installation:

Planning and Preparation:

Before drilling any holes, it's crucial to carefully plan the location of the holes. Consider the positioning of the seat base or hardware you'll be installing. It should be easily accessible and not obstruct your steering or other boat functions. Inspect the decking material and its solidity. Determine if it's plywood or fiberglass and whether there are any supporting structures underneath. This information will help you choose the appropriate drilling technique and hardware.

Gathering the Right Tools and Materials:

For the drilling process, you'll need a drill and the appropriate drill bits. A metal-cutting hole saw is highly recommended for creating clean holes in aluminium. You can find these at hardware stores or online. Additionally, gather safety gear such as safety goggles to protect yourself during the drilling process.

Drilling the Holes:

Once you've determined the exact locations for your holes, mark them with a centre punch to create a small indentation that will guide your drill bit. This will help prevent the drill from wandering. If possible, clamp some scrap wood on both sides of the drilling area to provide additional stability and prevent the drill from wandering. Use a liberal amount of lubricant, such as liquid dish soap or WD-40, while drilling to prevent aluminium chips from clogging the drill bits and to facilitate a smoother cut. Drill slowly and steadily, allowing the drill to cut through the aluminium at a controlled pace.

Finalising the Installation:

After drilling the holes, it's important to deburr them to ensure smooth edges and a secure fit for your hardware. Use a metal file or a deburring tool to remove any sharp edges or burrs. Finally, seal the holes with marine caulk or an appropriate adhesive/sealant to prevent water intrusion and corrosion. Allow the sealant to cure completely before using the boat.

By following these steps and taking your time, you can successfully drill holes in your aluminium boat for mounting hardware. Remember to always put safety first and work carefully to avoid any mishaps.

Positioning the seat base

Before you start drilling, it's a good idea to check the type and solidity of the decking under the seat and the structures (if any) under the deck. If you have a plywood deck, you won't be able to see under the deck, but plywood offers better screw retention than fibreglass. Make sure the fasteners you use are the right size and type. If you have a fibreglass boat with thin decking, you may want to screw or bolt the seat into a supporting structure, rather than just using the thin deck. Bolts are often better than screws because you can add substantial backing washers and nuts.

If possible, try to peek under the deck before installing your seat base. You can do this by installing an inspection port near the area where you want to mount the seat pedestal. Don't position the inspection port too close to the seat base, as this could weaken the deck. Then, use an inspection mirror to see what you're working with.

When positioning the seat base, make sure it's not too close to the hull. You don't want the end of your screw or bolt to be too near the hull.

Determining decking type and solidity

When installing pedestals in an aluminum boat, it is important to determine the decking type and solidity to ensure the safety and longevity of the installation. Here are some factors to consider:

First, it is crucial to identify the type of aluminum alloy used for the decking. Common alloys used in boat decking include 5052, 5083, 5086, 5454, and 6061. Each alloy has unique properties that influence its suitability for decking. For example, 6061 aluminum alloy is known for its excellent corrosion resistance, weather resistance, and slip resistance, making it a popular choice for ship decks. Understanding the specific alloy used in your boat will help you assess its strength and durability.

Next, consider the thickness of the aluminum decking. The thickness can vary depending on the intended use and structural requirements of the boat. For instance, in a Jon boat, some boat builders may use thinner aluminum sheets (as low as 0.090 or 1/8 inch) for the decking, while others may opt for thicker gauges (up to 1/4 inch) to accommodate heavier loads or more demanding applications. Thicker aluminum sheets will provide a sturdier and more solid base for your pedestals.

Additionally, it is important to assess the underlying support structure of the decking. Proper bracing and support are critical to ensuring the strength and rigidity of the deck. Closed-cell foam or other types of reinforcement between the stringers can enhance the overall stability of the decking. This will also impact the thickness of the aluminum sheet required, as adequate support can allow for the use of thinner material while maintaining the necessary rigidity.

Before installing pedestals, it is advisable to inspect the underside of the deck to identify any supporting structures, such as beams or ridges. This can be done by installing an inspection port or using an inspection mirror. Attaching the pedestals to these supporting structures, rather than just the thin deck, can provide a more secure and durable installation.

Lastly, consider the fasteners you will use to install the pedestals. It is important to select fasteners that are compatible with the type and thickness of the aluminum decking. For example, bolts may be preferable to screws as they can provide stronger and more secure connections. Using the appropriate size and type of fasteners will help prevent issues such as crooked screws or leaking decks.

By carefully considering the decking type, thickness, underlying support, and appropriate fasteners, you can ensure a safe and solid installation of pedestals in your aluminum boat.

Using bolts vs. screws

When installing a seat pedestal in an aluminium boat, you may be considering using either bolts or screws. Both have their advantages and disadvantages, and the best option for you will depend on factors such as the type of decking in your boat, the accessibility of the underside of the decking, and the level of security you require.

If you are installing a seat pedestal on a plywood deck, screws can be a good option as plywood offers better screw retention than fiberglass. However, if you are working with a fiberglass deck, it is important to note that threads cut by wood screws into fiberglass lack the strength, consistency, and durability of machined threads inside a metal nut. In this case, bolts may be a better option, especially if you are securing a component that is essential to the boat's function and safety.

Another factor to consider is accessibility. Bolts typically require access to both sides of the fastener hole, as they need to be secured with nuts. If you don't have access to the underside of the decking, screws or blind rivets may be a more feasible option. Blind rivets can be installed from one side of the fastener hole and are commonly used by boat owners. However, it's important to note that blind rivets are the weakest option in terms of strength.

The level of security required is also an important consideration. Bolts are generally considered more secure than screws, especially for withstanding tensile forces. Pedestal seat bases can exert significant upward force on their fasteners, and bolts with backing washers and nuts can provide a stronger and more secure hold than screws. Screws can weaken the decking around their threads over time and work loose, especially when subjected to the stress of a person sitting in the seat.

In summary, when deciding between bolts and screws for installing a seat pedestal in an aluminium boat, consider the type of decking, accessibility, and the required level of security. For plywood decking or when access to the underside of the decking is limited, screws or blind rivets may be a suitable option. However, for fiberglass decking or when a more secure hold is required, bolts with backing washers and nuts are generally recommended.

Installing an inspection port

If you don't already have access to the inside of your boat, you may want to consider installing an inspection port. This will allow you to see what you're working with when installing a seat pedestal.

First, you'll need to decide on the location of the inspection port. Choose a spot near the area where you want to mount the seat pedestal, but not too close, as this could weaken the deck. Sound the deck first to check for underlying structures that could interfere with installation.

Next, you'll need to create an opening for the inspection port. One method is to make a plate out of material similar to that used in your boat's tank. Place the plate on top of the tank, watching out for baffles, and drill a series of holes about half an inch in from the edge through the plate and the tank top. Remove the plate and open its holes for screw clearance. Tap the holes in the top of the tank and then cut a hand hole about half an inch inside the holes. The hand hole should be at least 5 inches to fit your fist.

Alternatively, you can cut a larger hole, such as 6 inches, in a spot where there is space and that will allow you to peer inside once the tank is back in place. You can use a saber saw for this, and if necessary, reverse the blade to make cuts that won't allow for "full clearing" of the saw. Cut a cover for the hole out of 1/2-inch thick Lexan Polycarbonate. To secure the cover, you can use bolts, such as 12 1/4-20 bolts, threading them from the inside to create "studs" sticking out from the surface of the tank. Use a sealant, such as Permatex blue form-a-gasket, and stainless steel washers and nuts to complete the installation.

Another option for creating an inspection port is to use a pre-made port light or porthole, which can be purchased from marine supply stores or online. These come in a variety of shapes, sizes, and prices, so choose one that fits your needs and budget. You can install the port light by drilling holes and bolting it in place, using a sealant to ensure a watertight fit.

Once the inspection port is installed, you can use an inspection mirror to see the underlying structure of the boat and determine the best location for the seat pedestal. This will help you avoid drilling into beams or ridges and ensure that your screws or bolts are securely fastened.

Frequently asked questions