taking removable fin systems to the next level

Under-the-glass

Boxes are placed beneath the glass to ensure structural integrity and a watertight installation.

Adjustability

The system provides 3/8" of adjustment for precise fine-tuning, which greatly influences performance.

Strength

The system's design emphasizes strength in every aspect. The elliptical shape maximizes stability while effectively distributing loads.

Easy Install

The box features a unique dam shape that facilitates effortless installation, allowing the glass to drape over it smoothly. It uses a single rout installation method.

Installation

Fin systems are commonly utilized with various construction techniques, and the routing system is designed to encompass all of them.

Critical information is provided here to help simplify the understanding of how the system is intended to be used.

There is only one installation methodology. This guide outlines the pre-lamination installation process and discusses the post-lamination (post-lam) installation process.

The routing system is a comprehensive tool that facilitates a successful installation. Thanks to the box's distinct shape, it features a unique capability for trimming down the box dam. The guide below provides additional information on this topic.

The installation guide discussed here is also available for download as a PDF file from the RESOURCES page.

Step-by-Step Guide

A guide through the entire installation process.

Preparation

Before the installation process can continue, we must ensure everything is on hand and ready.

Before the installation process can continue, we must ensure everything is on hand and ready.

For individuals, this begins with purchasing a STARTER KIT, as it includes everything needed to install the fin system. The kit provides all the parts mentioned in this guide. The starter kit does not include a router; we recommend using a trim router because they are easy to handle.

Other routers with wider bases will work, as guiding the router is managed by the router bit, not the router itself.

Preparations Steps

Click on the PLUS icons for details on each step

Starter Kit

Routing System

Routers

Attach Router Base

Router Bit Setup

Box Preparation

Layout

Fin systems are installed according to the shaper's preferred fin layout on the board.

The routing system allows for the precise positioning of the router jig on these marks. It must accommodate both side and center box layouts.

This section will outline the layout process.

Layout Steps

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Shaper’s Mark

Jig Placement

Layout Guide

Routing

This stage of the process involves creating the box cavities.

Now that the router jig is aligned with the shaper's marks, we are ready to proceed with the routing process.

Routing Steps

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Remove Layout Guide

Router Base

Cavity

Box Install

Now that all the box cavities have been created, the boxes can be installed.

We suggest pre-potting the boxes before the lamination process. This procedure minimizes stress and ensures a precise fit between the glass and the box.

The boxes will be secured with polyester laminating resin for polyurethane foam or epoxy for EPS blanks.

Box Install Steps

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Foam Collar

Box Installed

Laminating

Finishing

The sanding and finishing process can commence after the boxes have been installed and the bottom lamination has been completed.

At this stage, the bottom lamination and hot coating will be done. Everything is now prepared for sanding and finishing.

Finishing Steps

Click on the PLUS icons for details on each step

Trim and Sand

Glossing

Finish

Post-lam Install

In addition to the standard installation process described above, another option is a post-lam install.

A post-lam install is conducted after the glass on the bottom of the board is applied. This method is commonly used with a tinted or opaque-color glass job where having the color over the box's flange is not desirable.

Due to the unique shape of the GB24 box's dam, it looks fantastic with a color lamination directly over the box. This post-lam methodology is optional. Post-lam installs add strength to the box installation. This is because the box butts against thehe edge of the glass when installed in the cavity, helping to dissipate side loads.

Post-lam Steps

Click on the PLUS icons for details on each step

Create Box Cavities

Install Foam

Install Box

Add Glass Layer

Trim Dam

Finish Prep

Finish

Misc

Things we learned about the system installation process. This information will help achieve a better installation.

Introduction

As with any installation methodology, it helps to run a few test installations before making any changes. This will give you a better feel for the process and boost your confidence that the right choice was made.

For now, the most essential detail regards installing boxes in deep concaves.

As always, if there are any questions, CONTACT us; we are here to help.

Deep Concave Installs

When installing boxes on a board with deep concaves, an extra precaution must be taken to ensure the boxes are installed cleanly.

When a router jig is placed over a deep concave area, it can span the curve, as illustrated in the figure below. In this case, using the standard router depth will prevent the box from sitting flush against the bottom of the board.

To compensate, you'll need to increase the depth by the amount of bridging that occurs. Your goal is to position the box below the lowest point of the concave surface. Be aware that the depth gauge by itself won't provide sufficient measurement due to the curvature.

For typical concave surfaces, you'll need approximately 1/32" (0.5 mm) of extra depth.

Always perform a test run to verify adequate depth.

The illustrations below show what things will look like with a standard rout and the compensated-depth version.

Router jig sitting on a deep concave

End view shows how the router jig spans the concave

After routing with the standard depth, the box would end up sitting slightly above the lip of the cavity

Normal rout would leave the box sitting above the lip of the cavity

Box set slightly below the lowest lip of the cavity by utilizing a deeper rout

The box needs to be sitting below the lip of the foam at the lowest point

Routing System Details

The routing system is fundamentally key to the successful installation of the system. It is essential to understand the role of each of the components.

Routing system details

The illustration details each component of the routing system. The router jig is the central component—everything revolves around it. The jig's primary role is to guide the routing cavities where boxes are installed. A guide insert in the jig, made of phenolic material for strength and wear resistance, serves as the guide. This insert is removable for easy replacement and allows different inserts to be swapped in for future system parts (e.g., a canard box or leash plug).

The jig features optional tape tabs that help attach it to a board during routing. Multiple tab positions facilitate the attachment process. A soft rubber pad on the bottom protects the board, while a beveled edge around the outer perimeter creates a narrower bottom and makes lifting easier. The layout guide, when inserted into the jig insert, helps position the jig on the shaper's marks using engraved layout lines.

A replacement router base, wider than the standard base, is provided for our recommended trim routers. This increased width enhances stability during the routing process and is compatible with our router bit and bearing.

We also provide a replacement base that incorporates a bushing guide and a straight router bit. The router bit must be precisely sized to create the box cavity. The standard router bit features a ¼" diameter shaft, ⅜" diameter cutter, one-inch cutter length, and ½" diameter bearing. The straight router bit has a ¼" shaft and a ⅜" diameter cutter with a one-inch cutter length.

A depth gauge is provided to help quickly set the initial depth of the router bit in the router. Details on the trim spacer can be found in the next section.

Trim Spacer Details

The trim spacer can save time when sanding down the boxes' dams, but it is crucial to understand how it is utilized.

Trim spacer details

As part of our routing system, we provide a TRIM SPACER to remove the excess dam material before sanding the board. It is utilized after the board has been hot-coated and before sanding.

The trim spacer is designed to sit underneath the router jig and raise it by a fixed amount off the bottom of the board. It has two locator pins that align the router jig correctly on top of the spacer. The shapes are symmetrical, but to keep things simple, we ensure that the labels on the jig and spacer are at the top when assembled. The arrow on the jig points towards the rail of the board.

The spacer has four feet, two movable on either end. These movable feet can be relocated to avoid sitting on adjacent boxes or if one is off the rail's edge. The two center feet are fixed and hold the locator pins for the jig.

Each end of the spacer has seven holes into which the feet can be inserted. Each foot has a pin that fits in these holes.

Rubber pads on the bottom of the feet protect the board. Double-sided tape can also be attached to the bottom of these feet to secure the spacer on the board and prevent it from moving during the trimming operation.

Once the jig and spacer have been assembled and placed on the board, the trimming operation can proceed.

WARNING: Before proceeding, ensure the router bit's bottom is above the bottom of the board. If not, the router bit must be adjusted by placing a small spacer between the trim spacer and the router jig, enough to raise the jig without changing the router bit height. We provide small rubber spacers that can be used if needed. The bottom of the router bit should be at least 1/16" [1.5mm] above the bottom of the board.

Place the router on top of the jig and make small passes around the dam, removing the excess material. Following the jig edge is unnecessary, as we are not routing that far out. We recommend going slowly and removing small amounts at a time. Ensure the spacer and jig do not move during the process.

WARNING: It is crucial that when the boxes are prepared for installation, the screws are either removed or turned down well into the box, as we do not want to run into them in this trimming process.

NOTE: This process can be skipped if the sander is willing to sand down the dams with a grinder. We recommend using a 40- or 50-grit disc and running the grinder slowly, which helps reduce the plastic's melting. Go slow!

BE VERY CAREFUL WHEN USING THIS PROCESS. IF THE HEIGHT OF THE ROUTER BIT IS NOT SET CORRECTLY, IT COULD EASILY DAMAGE THE BOARD. DOUBLE-CHECK EVERYTHING BEFORE PROCEEDING. GO SLOWLY WHEN REMOVING MATERIAL, AS THE ROUTER BIT COULD BIND IN THE PLASTIC.

Still need help?

If you want more personalized help, you can contact us with questions. Also, check out our FAQ, as answers might be found there.

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Evolution of a fin system

GB24 takes the GEARBOX fin system to the next level, adding simplicity, adjustability, strength, and ease of installation.

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Use the dropdown menus for in-page navigation on the Install and Resources pages.

Starter Kit

This guide will use our Starter Kit as the starting point, containing everything needed.

The kit includes three sets of side boxes and a center box, each with foam collars.It also includes the routing system, which consists of a router jig to guide the routing of the box cavity.

We also provide a replacement router base for our recommended routers. There are two replacement bases: one with a bushing guide and one without a guide for use with a router bit with a bearing. The non-bushing guide version is the standard that ships with the kit.

A depth gauge sets the correct initial depth for the router bit. Finally, a layout guide is provided to help position the jig on the shaper's marks.

The kit also includes a TRIM SPACER, which helps trim down the box dam after installation. The replacement base is provided to increase its width. The standard base is too narrow for the jig, allowing the router to tilt easily during the routing process.

Routing System

This is an introduction to the parts that make up the routing system.

The routing system comes in a single configuration, providing everything needed for installation.

1. ROUTER BASE: This replaces the existing router base of our recommended Makita routers. We provide a replacement base because it needs additional width to make it more stable than the original.

2. ROUTER JIG: The jig is the primary means of positioning and routing the box cavity.

3. TRIM SPACER: For trimming down the box's dam after installation using the router.

4. LAYOUT GUIDE: The layout guide fits inside the jig and positions the jig on the shaper's marks.

5. DEPTH GAUGE: Used to set the depth of the router bit in the router initially.

6. ROUTER BIT: This bit performs the actual routing operation, relying on a bearing at the top of the cutter to guide the router around the inside of the jig.

7. HEX KEY: Used to adjust the screws in the boxes.

More details here.

Routers

Almost any router can be used for the installation process. It just needs to be able to fit a 1/4" shank router bit.

We recommend the MAKITA trim routers shown here because they are very effective and easy to handle.

We also manufacture a custom replacement base for these routers. These bases are used with a router bit with a bearing.

There are two versions: a battery-powered version and a corded version. Both versions are almost identical except for the means of powering them.

Our provided replacement base has additional width for your safety and peace of mind. While not mandatory, it significantly enhances stability and support, making your experience safer and more enjoyable.

The router bit has an upper bearing that guides the router as it cuts around the inside of the router jig.

Attach Router Base

If you use a Makita trim router, install the provided router base before setting up the router bit.

The GB24 routing system ships with the replacement router base for Makita trim routers. Before proceeding, it needs to be installed on the router.

The standard base provided with these routers is too narrow for safe use on the GB24 jig. The replacement base adds additional width for improved stability.

Base installation steps.

1. Install the router bit

2. Remove the existing base saving the countersink screws.

3. Position the base on the router using the arrow on the base top. The arrow faces the router's back.

4. Re-apply the screws but don't initially fully tighten them.

5. Ensure the router bit is centered within the base.

6. Tighten the screws.

Now, we can proceed to the next step, which involves setting the depth of the router bit.

Router Bit Setup
Router Bit Setup

Before any routing can begin, the depth of the router bit needs to be correctly set.

First, use the provided depth gauge. Place it on the bottom of the base with the router base facing up, as shown in the illustration. Now, adjust the bit's depth until it touches the underside of the gauge. After setting the initial depth, proceed to the second step to check the accuracy of the setting.

Secondly, place the router jig on the base with the base facing upwards. Set the bottom of a box on the rubber pad on the bottom of the jig alongside the router bit. Check the bit's depth and adjust if necessary; it should be roughly 1/32" [0.8 mm] above the lip of the box, as shown in the illustration.

We always want the box flange to end below the lip of the cavity, which makes for the strongest and tightest installation. Attention to depth is critical, as it can severely impact the installation process. Due to the length of the box, any rocker at the bottom of the board must be considered when setting the depth. Ensure that the ends of the box are slightly below the lip of the routed cavity. This might require setting the depth a little deeper to meet this requirement.

After setting the router bit depth, we strongly encourage making a test rout in scrap foam. This will help verify that the correct depth has been set before routing a board. For further guidance on deep concaves and adjusting the bit depth, refer to the INSTALL→ MISCELLANEOUS section at the end of this page.

NOTE: if needed, the depth gauge can be skipped in favor of the second step.

Simple Router Bit Setup
Router Bit Setup
Simple Router Bit Setup
PREP Screws
Box Prep

The final step in preparation for an installation is to get the boxes ready.

Firstly, make sure that the screws are either removed or turned down into the box so that they are protected from being touched during the sanding process. This is very important if the trim spacer is used to remove the excess dam material. You do not want to be hitting the screws with the router bit.

Secondly, the box's slot needs to be covered with masking tape. The tape must be at least 3/8" wide and compatible with the resin system. We recommend 3M 233+ or 301+ masking tape, which we sell in rolls if needed.

The screw holes should be filled with a small amount of clay. We provided chunks of clay with the starter kit for this purpose. Be careful not to leave any clay residue on the dam, as this could interfere with the adhesion of the glass.

NOTE: The original GEARBOX die-cut tape can also be used, as it fits, and is ideal for finishing, but it is a tight fit.

Tape can also be used over the screw holes; for this purpose, 1/4" wide tape is ideal. We hope to eventually supply die-cut tape that fits over both the slot and the screw holes.

WARNING: if covering the screw holes with tape, ensure that the tape does not extend down onto the flange. Otherwise, it will be left under the glass when the dam is sanded down.

Lastly, remove the foam collars from the bottom of the boxes. These must be installed before the boxes.

Everything is now ready for the installation.

PREP Masking Tape
PREP Screws
PREP Masking Tape
Shaper’s Marks

As part of the setup the blank must have the shaper’s marks and fin layout lines for the desired setup.

After a surfboard has been shaped, the shaper will lay out a series of marks on the tail of the board where the fin system is to be installed. The laminator will then utilize these marks to correctly place the boxes for the fin system. The back and front marks are key indicators in the installation process. The typical approach is to measure the back marks, with a front mark also established to indicate the amount of toe-in. Connecting these two dots with a line aids in installing the boxes. For the GB24 system, it is also helpful if the shaper's marks are placed 4 1/2" [114 mm] apart, as this matches the layout on our guide.

Router Jig Placement

Place the router jig on the marked surfboard blank, roughly lining up with the marks.

The router jig has marks indicating its orientation. There is also an arrow pointing to the board's rail. Although this is not strictly required, as the jig is fully symmetrical, it is a good habit to help it stay oriented. NOTE: The jig features an optional attachment system. This system consists of two tabs on either end of the jig. Masking tape can be applied over these tabs to anchor the jig to the surfboard. This is handy when performing a post-lam install, as the jig is more likely to slip on the bottom lamination. The tabs can also be placed in a couple of alternate positions.

Layout Guide

Next, place the layout guide inside the router jig.

The layout guide helps place the jig exactly on the shaper's marks. Its bottom features a meticulous arrangement of lines, crosshairs, and windows designed to align with the marks.

For side boxes, the inner lines (closest to the stringer) mirror the inner faces of the box slot, serving as a guide for placement. The window and crosshairs are positioned over the BACK shaper's mark, enhancing visibility. For center boxes, the centerline is the key to accurate placement.

The detailed illustration of these lines shows what each line represents.

Here are the steps in the process.

1. place guide within router jig

2. for a side box, the inner line (closest to the stringer) and crosshair are used

3. adjust the jig and guide until the crosshair is on the BACK shaper's mark; the window makes it easier to see the mark

4. align the inner slot face with the line between the shaper's marks

5. for a center box, use the centerline and crosshair positioned on the shaper's mark

The key takeaway for this task is that you always work with the BACK mark for an individual box.

Once the jig has been positioned, it can be anchored using the tape tabs. These tabs are optional and can be removed if not required.

Remove Layout Guide

Remove the layout guide from the inside of the router jig. Use the center handle for this purpose. Try not to move the router jig.

Now that the layout process is completed, we can begin routing the cavities for the boxes.

The jig's tape tabs are recommended to anchor it in place. This will help prevent accidental movement, which could result in a poorly routed cavity. Alternatively, double-sided tape can be placed on the bottom of the jig to secure it to the board.

Router Base

Ensure the replacement router base has been attached to the router before proceeding, only for the recommended Makita trim routers.

The replacement router base enhances the routing process. It has two characteristics over the regular base.

Firstly, due to the shape of the router jig, the inner cavity is slightly wider than the standard router base when following the inner guide. This raises the potential problem of the router rocking on the jig. To prevent this, the base is broader for improved stability. Use of this base is optional, but be aware of the risks.

Secondly, the bushing guide version provides an integrated guide bushing. This allows a standard straight router bit to be used, lowering costs.

This step can be ignored if a large base router uses a legacy bit with a guide bearing.

Cavity

Start the router and plunge it into the foam until the router base rests on the router jig.

Move the router towards the edge of the jig until either the guide bushing or the guide bearing contacts the inner surface of the jig.

Now, meticulously follow around the inner edge of the jig with the router bushing or bearing in a clockwise direction. This precise movement should leave a clean perimeter. Next, carefully slide the router around within the jig to remove the excess foam left behind by the initial routing process. Remember, do not push too hard on the jig during this process, as you do not want to move it.

If a center box is being routed and a stringer is present, it is advisable to make shallow passes along the stringer's length to remove wood slowly. Once complete, follow the procedure described above by following the guide perimeter.

Ensure there are no pieces of foam left in the cavity that might need to be routed away.

Turn off the router.

WARNING: ALWAYS WAIT FOR THE ROUTER BIT TO STOP SPINNING BEFORE REMOVING IT FROM THE JIG. THIS WILL HELP PREVENT ACCIDENTALLY KNICKING THE JIG.

NOTE: Check the cavity depth with a box before removing the jig. If necessary, make the cavity deeper.

Finally, remove the router jig and repeat the process for the remaining boxes.

Foam Collar

The first thing that will be installed is the foam collar.

Prepare a mixture of resin for the installation process.

Here are the steps in the process.

1. coat the inside of the cavity with a coating of resin

2. coat the sides and bottom of the foam collar

3. push the collar into the cavity, ensuring it is all the way down

4. coat the top and inside surface of the collar with resin

5. pour about a 1/4" of resin into the middle of the foam collar

Install Box

With the foam collar installed, the box can now be added.

1. push the box down into the cavity, making sure it goes all the way down flush with the collar

2. brush up any excess resin, leaving a thin film over the box flange and dam

Box Installed

Once installed, the box should sit slightly below the cavity's lip at its lowest point.

Ensure no excess resin is left on the surrounding foam or the box. This will result in a cleaner installation when laminating over the box.

Now, continue installing the remaining boxes for the chosen fin setup.

If the boxes are installed without pre-potting, proceed straight to the lamination process.

Laminating

We can proceed with laminating once all the boxes are glued in.

Prepare some extra 4 oz football patches that will be placed over the boxes once the bottom lamination has been applied. We recommend adding at least one additional layer, but two are better.

DO NOT PLACE THESE PATCHES UNDER THE MAIN LAMINATION!

They should be placed ON TOP of the primary lamination. If two patches are used, they should be different sizes. The larger one would go down first, followed by one 1/4" smaller.

We place the patches on top of the primary lamination to strengthen it. During the sanding process, the edges of the patches will be sanded and serve as indicators of the sanding depth. If the patches were under the primary layer, there is a risk of sanding through this layer at the edges of the patches. This would weaken the whole installation.

See the image for a visual.

If the boxes are being installed during the lamination process, follow the instructions for installing the foam collar and box before proceeding with the lamination. This can all be done at the same time.

Once the glass has been laminated over the boxes, run a finger around the bottom of the dam to remove excess resin and flush out any air bubbles. The extra layer of cloth can be applied at this time or after the primary layer has kicked off.

Trim and Sand

To facilitate the sanding process, we provide a unique trimming operation. This operation can be skipped in favor of simply sanding down the dam.

As part of our routing system, we provide a TRIM SPACER to help remove the excess dam material before sanding the board. At this stage, the board should already be hot-coated.

Its use is optional.

A separate section at the end of this page describes the trim spacer in more detail and how to utilize it.

Trim Spacer details here.

Glossing

Now that the board and boxes have been sanded, if a gloss coat is going to be added, that is the next step.

If a gloss coat is to be applied after the sanding, we must first ensure that the boxes' slots are covered.

The slot can be covered with 3/8" masking tape or die-cut tape. The screw holes can be filled with a piece of clay or covered with the die-cut tape.

Once all of the boxes have been covered, the glossing process can proceed.

Finish

If a gloss coat was applied, polish the board!

After the gloss coat is applied, the board can be polished, which is the final step of the process.

The masking tape over the box slots should have been removed during the gloss process before the gloss completely kicked off. This smooths the polishing process.

After polishing, a deburring tool can be used to clean up the edges of the box slots to remove any burrs from the sanding or glossing.

STEP 1

Create the box cavities.

The first step is to create the cavities in the bottom of the board. This process is identical to the normal one, except we will route through the bottom lamination.

Follow the process as described previously for laying out the boxes and routing the cavities.

Once the cavities have been created, a little sanding might be needed on the edges of the glass to allow the box to slide into the cavity. By default, the cavities are designed to be a tight fit; however, because the glass is more rigid, it may need to be eased slightly to allow the box to slide in easily.

STEP 2

Install the foam collar.

The next step is to install the foam collar into the cavity. As before, use a small amount of resin to wet out the cavity's interior and the foam's edges. Press the collar into the cavity, ensuring it is fully seated.

STEP 3

Now install the box.

With the foam collar in place, coat it with resin and pour some excess resin into the cavity. Press the box down firmly in the cavity until all excess resin has been squeezed out.

STEP 4

Add reinforcement layers over the box.

Once the box is fully seated in the foam collar, use the excess resin to apply a football-shaped layer of cloth over it.

One or two layers can be used; we recommend using 4 oz.

Remove all excess resin and squeegee down the cloth. Run a finger around the dam's base to push the cloth tight to the dam and remove excess resin.

Router Bit Setup
STEP 5

To facilitate the sanding process, we provide a unique trimming operation. This operation can be skipped in favor of simply sanding down the dam.

As part of our routing system, we provide a TRIM SPACER to help remove the excess dam material before sanding the board. At this stage, the board should already be hot-coated.

Its use is optional.

A separate section at the end of this page describes the trim spacer in more detail and how to utilize it.

Trim Spacer details here.

Router Bit Setup
PREP Screws
STEP 6

Finishing the install process.

With the boxes trimmed down and the sanding process completed, the board can now be gloss-coated if one is going to be applied.

In preparation, cover the slot with masking tape or die-cut tape. The screw holes can also be plugged with clay.

Once all of the boxes have been covered, the gloss coat can be applied.

Remove the tape as soon as the gloss-coat gels.

PREP Screws
PREP Screws
STEP 7

Finish the board.

The board can be polished and finished if a gloss coat has been applied.

PREP Screws