Product Focus: Boat Trim Extrusion

O Boat Trim Fender Extrusion With Insert
O Boat Trim Fender Extrusion With Insert

An Aluminium Boat Trim is an aluminium extrusion designed to act primarily as a boating fender. It is used on the sides of boats and other mobile vehicles and equipment as a bumper apparatus to absorb the initial energy or shock experienced in the planned or unplanned collision of the vehicle or equipment with other objects. A typical example of this would be a boat or vessel berthing against a jetty or quay wall. To do this, an Aluminium Boat Trim Extrusion complete with a rubber insert, needs to have high energy absorption and low reaction force. Historically, boat trims or boat fenders were woven from rope into various designs and simply hung over the side of the boat. Boat fenders of woven rope are still used today by some historic boat owners.

Examples of Woven Rope Boat Fenders
Examples of Woven Rope Boat Fenders

Aluminium Boat Trim Variants

Aluminium Trading stocks 3 different Boat Trims:

These extrusions are available in alloy grade 6063T4. This alloy provides good corrosion resistance and has a medium strength with good mechanical properties. The alloy can be easily welded and machined provided you have the right equipment.

*Please note that all three of these extrusions have different inserts.

Installing an Aluminium Boat Trim Extrusion


We recommend you have the following tools available when fitting our aluminium Boat Trim extrusions:

  • Tape measure,
  • Variable speed reversible drill,
  • Putty Knife,
  • Sealant applicator gun,
  • Hack saw,
  • Hot air gun (if available)
  • Tub of hot water,
  • Drill bits (with appropriate screwdriver bits).


  • Aluminium Boat Trim extrusion with insert,
  • Marine grade silicone sealant,
  • Stainless steel screws,
  • Safety goggles.


For best results we recommend that 2 persons undertake the fitting of our aluminium Boat Trim extrusions.


The simplest method to calculate the amount of trim required is to double the boat’s length and add the boat’s beam (width), then round up to the nearest full length of aluminium trim. This will give you a total length of required trim in meters.

Our aluminium Boat Trim extrusions are supplied in 6 meter lengths and the inserts in rolls with lengths of up to 200 meters.

We strongly recommend taking a bit of time to properly plan the fitting of your boat trim in order to be fully aware of where any bends or mitres will be required before commencing with the installation.

Fixing method

Place the Aluminium Boat Trim against the hull. If the boat trim profile has a lip, then the lip should cover the underside of the deck moulding. Using the centre line within the aluminium as a guide, drill directly into the hull and secure it in place with the stainless steel screws.

Lengths should be butt joined to give the appearance of a continuous length.

Trimming may be required of the body in order to finish the transom. We recommend using a hack saw to achieve this and an end cap should then be used to complete the finish.

Pro Tip: By applying some sealant to the end of each of your screws before fitting them, you will help ensure that each hole is well sealed.


Important: Be sure to wear your safety goggles at all times!

If you are replacing an existing boat trim or fender then it will more than likely be held in place by either screws or pop rivets. The following instructions will cover replacing your boat trim in both instances.

1) Remove end caps to allow access to profile. These are usually held in place by screws and maybe some silicon sealant.

2) If there is an insert within the profile remove this too. This will then allow you to view how the existing trim or fender has been fixed:
a) If it has been screwed in then simply loosen the trim using a standard screw driver or a drill on reverse with a low speed setting.
b) If the existing boat trim is fixed with pop rivets, then the heads will need to be drilled out. It is important that you do not use a drill bit that is bigger than the shaft of the existing rivet in order to ensure that you only remove the head of the rivet. Once done the shaft can then be pushed through.

3) Fixings will usually be found every 20-30 cm. Depending on your setup and the size of the existing profile, it may be easier to remove the old trim in sections.

4) Remove the end caps, inserts, fixings and existing trim. There will more than likely be silicone sealant behind the trim or fender which should pull away when the existing trim is removed.

5) Next, use your putty knife to carefully remove the excess and loose silicone sealant that was revealed with the removal of the old trim/fender.

6) You are going to need to create new holes to install your new boat trim so put some silicone sealant in an applicator gun and fill in all the existing holes left by the old trim or fenders fixings.

7) Mark a centre point on a length of aluminium trim using a pencil or relevant marker then hold this mark against the centre of the bow.  Proceed to ‘roll’ the trim around the hull of your boat until you reach the end of the length. This will give you the first fixing point to start the installation of your new boat trim.

8) Drill and secure the new boat trim with your choice of screws or rivets every 22-30 cm.

Tip: Apply some sealant to the end of each of your screws before fitting them to ensure that each hole is sufficiently sealed.

9) Pull the boat trim extrusion around the radius of your boat, fastening as per instruction (8) as you go.

Important: For the bow of the boat and other tight radii it is highly recommended that you pack the internal corners of the aluminium trim with wire or a piece of the insert which covers the area to be curved. This will prevent the extrusion from collapsing whilst it is being formed as this could hinder the fitting of the insert. Whilst the aluminium boat trims are suitable for bending, they may require preforming or mitreing where very tight bends are needed.

10) Soak the Rubber Insert in a tub of hot water (approx 40C ) for approximately 10 minutes to make it softer and easier to fit. If this is not a practical solution then either leave the profile in the sun to soften it or gently warm it with a hot air gun. Be careful not to heat the insert up too much as this will make it more susceptible to tearing and damage during installation.

11) Once you are ready to fit the insert, start at the transom and allow approximately 300 mm to overhang the end of the boat trim to allow for any shrinkage that may occur once the insert cools. Push the insert into the boat trim profile and work your way around the boat. Do not attempt to slide the insert into the profile as this will cause the aluminium to shave and damage the edges of the insert. Tight bends may require you to reheat the insert with a hot air gun to ensure a good fit.

12) Once the insert is in place do not trim the ends for a couple days in order to allow for any further shrinkage.

13) Trim off any excess insert and secure the ends of the insert in a suitable fashion.

Custom Trim Designs

If you are a retailer who sells boating equipment and spares we can assist you with the production of exclusive boat trim dies to extrude your own fender designs or even just aesthetically appealing trims.

If you are looking for a one-off custom trim or fender, our workshop uses the latest technology to deliver customised profiles with relatively short lead times. Contact us for more information.

Whether the product is a stand-alone boat trim, fender or a complete fender system incorporating elements of PVC, aluminium or stainless steel, our team are on hand to offer their advice and guidance at every step of the design process.

The information contained on this web page is for general information purposes only. By using this website you agree to be bound by the disclaimer.


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