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Greenlight Surfboard Building Guide - How to Shape a Surfboard


Tracing the outline on the blank is where all of your hard work making a template gets put to use. Too bad this step is over in an instant. You always trace the outline of your board on the bottom of the surfboard blank. Line up the straight edge (or stringer points if you are using a spin template) of your template along the center of the stringer, and adjust the exact location of the template fore-aft on the blank to line up with the intended rocker that you want. Remember that the blank is longer than your template, so sliding the template forward on the blank will give you more nose rocker, and sliding it backward toward the tail will give you less nose rocker and more tail rocker.

Once your template is lined up in the right place, simply hold it down flat on the blank and trace the outline onto the foam using a Shaper's Pencil. Then you flip over the template, center it on the stringer and fore/aft, and trace the other side of the board. Make sure you have the same fore/aft location on both sides to insure symmetry of your outline.


Once your outline is traced on the bottom of your blank, you need to cut it out. For EPS blanks, you can use a jig saw with a long blade or a simple hand saw. Most shapers just use hand saws to cut the outline on PU blanks.

Cutting the outline on your blank is similar to cutting out your template: STAY OUTSIDE THE LINE by at least 1/8” inch to give yourself some room for error. Cutting inside the line gives you a dip in the outline that cannot be fixed unless you change (narrow) the dimensions of your shape. Try to avoid this.

One final tip in cutting your outline is to keep the sawblade as square as possible (90 degrees). You can clean this up later in the process, but the more vertical your outline cut, the easier it will be to get a good, clean shape.


Once your outline is cut, you need to perform one of the most important, yet underappreciated tasks of shaping: squaring the outline cut. If you can have a nice 90 degree vertical rail for the full length of the outline, your rails and board will turn out much better.

Experienced shapers usually use a power planer to square and smooth up the outline cut. We don’t recommend this for beginners unless you have significant experience with power planers. Instead, square up your outline rails using a Rail Runner Tool to clean up and remove material from the rail, or you can also use a G-rasp or a hard sanding block and sandpaper.

You can place the blank either flat on the shaping racks (with your shapers weight holding it down) or sideways in the saddle with the rail facing up. Start with the Rail Runner Tool to shave away all of the high spots from your cut. Now is the time to carefully hone in on the line you traced on the blank. The Rail Runner will automatically shape that flat, 90 degree rail outline.

The goal here is simply to clean up and smooth out the outline as much as possible, getting rid of hills and valleys in the outline, and honing in (but not yet touching) on the traced line. You want to end up with a nice, smooth outline curve, so take some time to step back and look down the full length of the rail to identify if there are any unwanted dips in the outline. This is a good time to use your sidelights or handheld flourescent light. Another trick to ensuring your outline is bump-free, use the hard handing block without sandpaper and run it along the rail. You'll feel any wobbles through the block that your eyes can't see.

Once you have gotten close to the line and smoothed out the hills/valleys in the outline cut, it is time to breakout the combination square and hard sanding block. This final step in “truing” the outline is where you want to make sure the outline rail is as close to 90 degrees vertical as possible. Run your combination square along the rail of the board and you can quickly see where the outline needs to be squared up. Work slowly here, using the hard sanding block with medium grit sandpaper (60 grit) to flatten and square up the rail areas that that aren’t straight and flat. Keep checking with the combination square as you make adjustments.

Once you are satisfied that the outline cut is “true” and square, do some final sanding with a hard sanding block and 80 grit sandpaper, making sure you have sanded away the outline mark and that the outline cut is smooth, bump-free, and square. Again, don’t be a slave to the outline mark. It is better to trust your eyes and look at the entire curve to ensure it is smooth. If you do a good job in this step, you stand a much better chance of turning out a good looking surfboard. We can’t stress this enough.


Once you have squared up and smoothed out the outline, it is time to mow some foam and define the thickness and rocker profile on your blank. To get your blank to the proper thickness, you should be removing at least 1/8” of material on both the top and bottom of the blank. For example, if you want your board to be 2.5 inches thick, your blank should be at least 2 ¾” thick, giving you some room to remove some material and make sure the deck and bottom of the board are finished flat and square to the outline cut. When you finish foiling, the cross-section of the blank at any point along its length should look like a rectangle. Nice and square.

Most shapers begin foiling their blank on the bottom, which allows them to define the rocker of the board and hone in on the thickness in the nose, center, and tail area. Once the bottom is finished, the task of foiling the deck of the board becomes much simpler, as the goal is just to make sure the deck is flat and enough material is removed to arrive at your desired final thickness throughout the board.


 Before you put blade to foam, you need to have all of your rocker and thickness measurements handy. Specifically, you should know:
  1. Nose Rocker (at the tip)
  2. Nose Rocker (12” from the nose)
  3. Tail Rocker (at the back)
  4. Tail Rocker (12” from the tail)
  5. Board thickness 12” from nose
  6. Board thickness at center of board
  7. Board thickness 12” from tail

If you designed your board on a CAD program, you should also have access to intermediary thickness and rocker points such as 24” from nose and tail. With these thickness and rocker measurements handy, your first task is to make some pencil/Sharpie marks on your blank to act as guide points as you are removing material and shaping your rocker and thickness. 

You will need a Versasquare, Tape Measure, and “Rocker Stick” to identify and mark the key points on the blank. A Rocker Stick is simply a long, straight stick placed along the stringer of the board to measure the depth of the rocker. Shapers typically use angle iron or square aluminum sticks that are cheap and easy to find at home centers. Find one that is at least as long as the board you plan to make. You can use any long stick to measure rocker, as long as it is straight and not too heavy so that it will bend the blank when placed on the stringer.

Use your Versasquare to mark the rails (Shaper's Pencil) at the points 12” from the nose, 12” from the tail, and at the center of the board. To find the center point, use the tape measure to find the center on the stringer, then use the Versasquare to extend that stringer center-point out to the rails. Make your marks on the rails extending down far enough so that when you sand/plane the bottom, the marks don’t disappear. You may also want to mark the intermediary points on the rails as well, particularly 24” from the nose and tail. Conveniently, the Versasquare is exactly 12” long, so when you set it flush to the nose and tail, the other end of the Versasquare is exactly where you want to make your marks.

 Once these rail-marks are placed, you can measure the rocker of your blank at key points. Place your rocker stick on the stringer and find the level point with a bubble level by sliding the rocker stick back and forth. You can now measure the distance between the bottom of the stick and the stringer at key points along the board. Remember that the low-point of the blank has a rocker of zero, so if the nose rocker measures 5” and you want your nose rocker to be 4 ¾”, than you will be removing more material from the middle of the board to effectively “lower” the rocker to your desired 4 ¾”. Typically, the tail of blanks is thicker with less rocker than most boards have, giving you more flexibility in defining your tail rocker. So if your rocker stick shows 1.5” of tail rocker and you want to have 2” of tail rocker in your board, you will be shaping more material off the tail of the blank than the middle, in order to increase your tail rocker to the desired 2”.

Once you know what type of adjustments need to be made to your nose and tail rocker, you can make marks on the rail (at the same 12”, 24”, and center points you already marked) to define how much material you need to remove in each area to get the desired rocker. Use your combination square to make these marks on each side of the board. At the same time, you must be mindful of the final thickness you want to make your board in each of these areas. Remember to have at least 1/8” thickness “leftover” to remove from the deck of the board once you have marked and foiled your bottom rocker.

A final note on marking your blank: don’t get overly caught up in the numbers! Water flow doesn't care about numbers, only curves. It’s OK if the blank does not allow you to get your exact rocker and thickness profile. It is more important to have smooth, continuous curves in your rocker than to try to “manipulate” the blank into fitting your exact thickness and rocker numbers.


Now that your blank is marked, and you have a game plan and guide points for shaping the rocker, it is time to have at it. We recommend using the 'Rasputin' Foiling Rasp Tool or G-Rasp on your first board but you can also use a power planer to foil your blank. It is by far the most efficient means of removing material quickly and cleanly, especially in the stringer area. If you are a beginner with a planer, it is safer to set the cutting depth low (less than 1/16”) so you can get comfortable using the planer without removing too much material at a time. We also recommend doing some YouTube searches on “shaping surfboards” so you become familiar with what planing a blank actually looks like. 

Your blank should be set on the shaping stand bottom-up. Don’t forget the eye protection and dusk mask, as foam/stringer debris will be flying out of the planer’s dust chute. Plane one side of the blank at a time, from rail to stringer, keeping the passes parallel to the stringer. To start, it helps to draw guidelines on the blank with a shaper's pencil that are parallel to the stringer and spaced about 3" apart. You'll see the lines are long near the stringer and short near the rail due to the outline curve of your blank. This is a critical visual to help you plane the foam evenly and flat.  Start with the planer resting flat on the board, at about a 45 degree angle to the stringer, near the outermost line you drew at the rail. Turn on the planer, and work your way along the line at a slow and steady pace, letting the tool do the work. When at the end of the planer pass it is best to "follow through" and not stop abruptly or just turn off the planer. Follow through like an airplane taking off a runway, smooth and upwards. Do not turn the planer downwards at the end of the pass or you'll take a chuck out of the rail. After the first pass is complete, go back to the 2nd line and start planing again. Basically planing your blank is like mowing a lawn: try to make parallel passes that are slightly overlapping. Make sure the planer stays at a 45 degree angle each pass for a smoother cut and the baseplate of the planer (not to be confused with the front 'shoe' that is adjustable) runs on the area you just planed. This will ensure you are planing flat. If you have big gouges in the foam after your first few passes, you're either not running your planer at a 45 degree angle to the stringer or the planer base is not flat on the previous cut...

If you have to remove more material in a certain area (like to increase your tail rocker), make extra passes in the tail and either slowly lift the planer off the blank where you want to feather the cut back to the existing rocker, or reduce the cutting depth to zero as you are approaching this feathering area. Good shapers become very adept at adjusting the depth of the planer blade as they are planing. This is a somewhat advanced skill to master, but certainly worthwhile to practice as soon as possible.

Once you have made a few passes with the planer, you should smooth out the lines and flatten the deck with the 'Rasputin' Foiling Rasp Tool ,G-Rasp , or hard sanding block and Tigershark sandpaper. Take long, smooth strokes with medium pressure , and keep at least part of the sanding block touching the stringer so you are not removing too much material and leaving the stringer “high”. Remember that foam will sand away much faster/easier than the wood stringer, so it is a good idea to take a few passes with your trim plane along the stringer during this foiling process to keep it level with the foam.

Remember to keep moving around the blank with your sanding block. Don’t focus too long in one area or you will create a dip in that area. Try to give the entire surface area of the blank “equal time” so that you can retain a symmetrical, flat bottom. Once you’ve smoothed things out with the sanding block, take your combination square and measure board thickness at the marked points on both sides of the rails. You want to make sure the thickness is the same on both sides at each of the marked points. If you find the thickness is off by more than 1/16”, try to even it off with a few strokes of your hard sanding block.

You can repeat the above planing/sanding process until you achieve the desired flatness, thickness, and rocker profile. The planer removes material, the sanding block smoothes it out. Take your time and measure thickness CONSTANTLY with your combination square during this process. Also take your yardstick and place it across the bottom to make sure you are keeping the bottom flat. Make any necessary adjustments with your trim plane (on the stringer) and G-Rasp.


With your bottom rocker shaped and smoothed, the final step in foiling your blank is flattening and foiling the deck. This process is similar to foiling the bottom, but now you are trying to flatten and foil the deck of the board to its final thickness in the nose, center, and tail of the board. Flip your board deck-side up on the shaping stand and place the shapers weight on the deck. Use your combination square to mark both rails at the final thickness points at 12” from the nose/tail; 24” from the nose/tail, and at the thickest point of the blank (near the center) to give you your final guidelines for foiling the deck.

Once your final thickness points are marked, you follow the same procedure as the bottom with the planer and hard sanding block to remove material and flatten the deck down to your desired thickness. However, you will find it is very difficult to effectively plane material in the nose area of the deck because of the upward curve of the blank. In this area, you need to reduce the stringer thickness using a spokeshave and remove foam with a G-Rasp. Once again, use your yard stick to make sure you are keeping the deck flat, and use your trim plane, spoke shave, and G-Rasp to make any necessary adjustments.

Keep checking your thicknesses with the combination square as you work on the deck, and stop when you have reached your desired thickness measurements in all marked areas of the board. At this stage in the game your blank should have a smooth, flat bottom with the correct rocker, smooth vertical rails, and a smooth, flat deck. Everything should be sanded to a medium grit (60) finish. You will come back and re-sand everything with higher grit sandpaper (80) and a foam sanding pad once the rails are shaped.



DESIGN: Other design elements have an effect on the shape, length, and depth concaves, particularly board rocker, thickness, and the kinds of waves the board is intended for. Once these factors have been determined, the shaper then decides on the general length and depth of concaves to use, and how multiple concaves will interact and influence the flow of water along and across the bottom of the board. (See Design Notes on Bottoms)

Basically you're making a spoon shape in the bottom of the board. If you can envision that shape of a spoon then shaping concaves will be easy for you.

MAP: Measure and mark where your concaves will begin, end and reach their maximum depth. Light pencil marks on the stringer should mark where your concaves begin and end; and light lines across the bottom of the board, perpendicular to the stringer, will help novice board builders cut concaves with symmetry and accuracy.


Single Concaves:

With just a trim plane and sandpaper. Single concaves are usually roughed out using an electric planer but you can certainly use a trim plane to dig out the stringer and then follow up with a hard block and Tigershark Sandpaper to scoop the foam to shape a concave. Starting at the center of your concave (where it is deepest) take small passes with the trim plane and gradually work your way out to the ends along the stringer with longer passes. Keep in mind you'll want to go in one direction and follow the stringer wood's grain. By digging out the center with multiple passes you'll see the concave take shape on the stringer with the deepest point in the middle fading out to shallow at the ends of your concave.  

Once the stringer concave is set you can use a hard block and paper or a G-rasp to scoop out the foam from the stringer outward to the edges of your concaves. Again, work from the center out to the rails and use more pressure to remove more foam at the center and less towards the outer edges of the concave.

If you're using an electric planer without on-the-fly adjustment you can set the planer at the deepest cut and follow the same procedure as using trim plane starting from the center of the concave and working towards the ends. Once the stringer concave is set you can stap left or right of the stringer and plane a small section to remove some foam then finish with the hard block and sandpaper or G-rasp as described in the above section.

If using a Modified Hitachi Planer with on-the-fly adjustments, same thing but starting at one end of the concave with the planer depth set to zero, begin your first pass down the stinger, through the middle of the concave, slowly opening, then closing, the blade to gradually fade the concave in, and then out, as you make the first pass. This can be tricky and take some practice, but by adjusting your planer’s depth of cut “on the fly,” you can time your pass and blade adjustment to fade the concave in and out, and hit maximum blade depth precisely at your max depth line in one pass. The trick is opening and closing your planer blade from zero, to max depth, then back to zero, in order to rough in your concave’s depth profile smoothly and in a single pass (or two, depending on the desired concave depth). Once the center of your concave profile is roughed out with the planer, you may proceed with the planer to blend in the rest of the concave, or switch to your G-rasp or hard block and Tigershark Sandpaper.

No matter what tool you use, the idea is to blend the center planer pass edges into a smooth, arcing concaved curve out to the rail. If using a G-rasp and/or sanding block, this is done using a “diagonal blocking” technique. Take your tool and place it along the raised edge of your planer pass. Starting with firm pressure on the tool, pull it diagonally down and across the bottom of the board, toward the rail, while easing up on the pressure as you slide toward the rail to feather out the amount of material removed. Firm pressure toward the middle of the board will remove more foam in the deeper part of the concave; lighter pressure as you move the tool toward the rail removes less material, resulting in the bowl-shaped concave form you’re trying to achieve in the bottom of the board. Pay attention to how the shadows fall across the bottom of the board, and tip the board from side to side to get more information from the sidelights as you go. If you can, turn your sidelights off independently… left and right… and let the shadows tell you where you need to go with your tools. Remember to leave about 10% of the foam remaining for the next tool to remove – the padded side of your sanding block or foam shaping pad with sandshark screen. Using the same diagonal blocking technique, stroke diagonally from the middle of the board outward, toward the rail, with decreasing pressure. Start with low grit, and work your way down to finer grits.

ROUGH OUT – Double Concaves: In boards with single-to-double concaved bottoms, the double concaves are shaped into the single. As is the case with single concaves, determining the length and depth of the concave is part of the design process, and up to the shaper. The process for shaping double concaves is similar to shaping singles, the difference being in the primary tool used, which is the G-rasp or hard block and Tigershark Sandpaper rather than the electric planer. The double concaves are mapped out with light pencil marks, then roughed in with the tool, starting down the middle of the concave. Cut in the depth profile of the concave through the middle of the concave (where the concaves being, reach max depth, and end), then feather out this center surform pass toward the rail on one side, and the stringer on the other. Do this with a scaled down version of the diagonal blocking technique described above, finishing with the padded side of your sanding block once the double concaves are sufficiently roughed in and blended with the tool. Remember to use your shadows to help you create smooth, symmetrical concaves on both sides.

FINISHING: If you’ve done a good job cutting the depth profiles, blending and feathering in the concave’s arcing shape, and have been paying close attention to what the shadows have been telling you as you progress, finishing the concaves is the easiest step. Using fine grit sandpaper or screen under a foam pad, use light pressure to finish your concaves. Floating the pad through the concave array with long, lengthwise strokes will remove any remaining scratches or irregularities. However, putting too much pressure on the pad will result in “finger dents” in the surface of the concave, which will have to be shaped out, deepening your contours. Finish with the mini block plane along the stringer. Be sure to use a sharp blade and not to gouge or “chatter” the foam along the stringer.


Shaping the rails can appear to be the most confusing step for a beginner shaper, but if you’ve done a good job smoothing and truing your outline, shaping nice rails is actually relatively easy. Rails are shaped with multiple angular cuts called “rail bands.” These rail bands are measured and laid out to determine the shape and volume of your rails. They are shaped with a G-rasp or power planer to create flat planes which are then rounded off with SandShark Rail Screen for a smooth, hydrodynamic shape. There are typically two or three rail bands shaped on the deck and one rail band on the bottom, called the "tuck", that determine the rail shape. See the illustration below:


 Surfboard Shaping Rail Band Layout

Before you start making these cuts, you need to determine what type of rail profile you want in your board. Like bottom contours, rail shapes are a mix of art and science subject to debate, but fortunately Greenlight has simplified this area of shaping by offering guideline rail-band measurements for the two basic kinds of rails: higher volume “boxy” rails and lower volume “knifey” rails.

Click to download sample Surfboard Railband Layout Examples for Boxy and Knify rails:



Basically, boxy rails have more volume and therefore more buoyancy/resistance when engaged into a wave face. Knifey rails have less volume and therefore penetrate the wave face easier. Knifey rails are used for higher performance shortboards where rail-penetration is desired, and boxy rails are used for longboards and less performance-oriented boards where flotation and stability are the desired characteristics. If you want to learn more about rail design, sign up for Greenlight's Design Newsletters.


Once you’ve determined the rail profiles you want, print out Greenlight’s Rail Band Measurement Sheet for Boxy or Knifey Rails and bring this sheet to your shaping space. Keep in mind that you are free to improvise on Greenlight’s recommendations, just avoid any extreme differences from point-to-point, as you want the rails to flow smoothly and not change shape/volume suddenly.

Use a combination square to mark the appropriate rail band points on the rails (for both top and bottom rail bands) and use your Versasquare to mark your deck and bottom rail band points. Some people draw lines to connect these dots to create guidelines, but we prefer not to do this, as the lines are very difficult to draw accurately, and they will end up throwing you off. As in many other steps of shaping, it is better to trust your eyes, step back from what you are doing, and try to get your rail bands cut as smoothly as possible by eye. The rail band marks on the deck and rails at a few key points along the length of the board should be enough to guide you through the process.

Below is a chart of common rail shapes and the railband dimensions.


For a 2 1/2" Thick Surfboard (see notes below)

Rail Type Tuck Rail Mark Deck Mark 1  Deck Mark 2 Deck Mark 3
Modern Rails
Thin 1/2" 1 1/8" 2" 4" X
Medium 3/4" 1 1/2" 2" 4" X
Full 5/8" 1 1/2" 1 1/2" 3" X
Other Rail Types
Full Soft 3/4" 1 5/8" 2" 4" X
Boxy 1/2" 1" 2 1/2" 4" X
Down Rail 3/8" 7/8" 1 3/4" 2 3/8" 3"
True 50/50 * 1 1/2" 3 /4" 1 3/8" 2"
Egg ** 1 1/4" 1 1/4" 1 3/4" X
Pinched *** 1 1/8" 2" 3" X
"Angular" Down 3/8" 1"  7/8" X X

Railband Notes:

*True 50/50 rails, like those on many classic longboards, require rail bands on the bottom of the board, rather than a simple, curved tuck. For 50/50 rails, flip the blank over, and repeat the same marks and rail band patterns on the bottom of the board as you did on the deck.

**Egg rails require one bottom rail band. To shape this band, make a rail mark 1/2" up from the bottom corner of the rail, and a bottom mark 7/8” in from the bottom corner of the rail. Connect the two marks to create a single flat plane to become your bottom rail band. Blend this band into the curves of the rail and bottom as you do the other bands.

***Pinched or Knifey rails require one bottom rail band. To shape this band, make a rail mark 5/8” up from the bottom corner of the rail, and a bottom mark 1” in from the bottom corner of the rail. Connect the two marks to create a single flat plane to become your bottom rail band. Blend this band into the curves of the rail and bottom as you do the other bands.

FOR STANDUP PADDLE BOARDS: Use the "BOXY RAILBAND" numbers and multiply the rail band dimensions by a factor of 2. For example your SUP tuck measurement will be 1", Rail Mark is 2" , Deck Mark #1 is 3" , Deck Mark #2 is 8" 

One final note on rail bands: For the most part, the vertical surface that remains along the outside of the rail once the tuck is shaped and primary band is cut, determines the overall volume of the rail. It is important that this “band,” which will become the rail apex once the rail is finish shaped, is widest at the widepoint, and tapers smoothly toward the nose and tail. This taper will determine the “foil” of the rail – how the volume of the rail flows from nose to tail.


Most shapers begin with the smaller rail band on the bottom of the board. Besides old-school longboards, most boards have a sharp bottom edge running from the tail to about 16-20 inches up from the tail. This sharp edge then slowly tapers into a rounded bottom rail through the nose area. Some shapers shape the bottom rail band with a Greenlight's Rail Runner Tool for ease of accuracy. You can also use a planer, or by hand with a G-Rasp and then a hard sanding block.

To begin shaping your bottom band, place the blank bottom-up on your shaping racks with your shaping weight near the center of the board. Start shaving with the Rail Runner or shaping tool of your choice with light pressure where you want the hard edge to begin tapering, and work your toward the nose. Use the tool to remove most of the foam down to your bottom rail band marks, then smooth and clean up this band with your hard sanding block. When completed, this bottom band should get wider toward the center of the board, then taper slightly towards the nose of the board. Once again, as you’re shaping this band, step back and take a good look with your eye. This is another good time to utilize your sidelights or fluorescent handheld light. Ideally, the band has a nice smooth curve to it, with no sudden changes in width or angle.


The top rail bands are substantially larger than the bottom. You can do them by hand with a G-rasp, or power planer. Just like with foiling your board, you can always adjust your planer to a low-depth to minimize potential mistakes while planing your rail bands. There are typically two main deck railbands that you cut before you begin smoothing and rounding the rails. The first cut is the steeper band which is closer to the rail on the deckside, the second band cuts further toward the stringer, but not as deep as the first rail band.

You need to be very careful with the planer as you approach the nose area, as you don’t want to take out a big chunk of nose by accident. It is safer just to plane your railbands with the planer up to about 10" or so away from the nose. You can finish the rail bands in the nose area by hand with a G-rasp and hard sanding block.

Since top rail bands reach their maximum depth toward the center of the board, you will also want to try to adjust the planer depth “on the fly,” keeping it lower in the tail and nose area, and higher in the center. Like everything else in shaping, the key is just to try to have nice, smooth bands with no sudden changes in width or angle. Once you remove the majority of material with the planer, finish off the first rail band with your hard sanding block, trying to have the band meet up with your first rail-band markings. It doesn’t have to be perfect, just try to have the band come out as smooth as possible.

Once the first rail band is cut and smoothed, you plane the second band, using the marks on the deck as your guideline, and intersecting the first rail band at about its mid point. Use the planer to remove most of the material for the second band (except in the nose area), and finish up with the hard sanding block. Use the sanding block to smooth out the second band and get it close to your second band marks on the deck. Don’t worry if you still have pencil/Sharpie marks all over your blank at this point. You will sand them out in the final sanding step.


At this stage you should have two distinct rail bands carved into your deck, and one on the bottom of your blank. Now you need to use your hard sanding block to “break down” the distinct lines connecting each rail band.  Use your hard sanding block with medium grit (60-80) sandpaper to flatten the hard edge between the two top rail bands. You will create two new edges by doing this, but the angles on these new edges are lower and not as sharp. Blending the bands is the continuation of this process until you have a series of very small bands with low-angles, forming a rough curve which represents your final rail shape. The very top rail band should almost invisibly blend into the deck.

You also should continue to have your vertical rail, which represents the original outline of your board.  Since you’ve carved out your rail bands, this vertical section is much smaller than it used to be. As you continue breaking down the rail bands with your sanding block, try to make sure you maintain that small vertical band down to about 1/2” width or so. If you sand into this band, you are changing your outline.

You must also blend your bottom rail band into the bottom of the board and the vertical band on the side of the rail. The process is the same as the top, albeit you will only need to take a few passes smoothing out the distinct lines on the bottom as it is a much smaller radius curve than the top. Try to leave a nice, smooth distinct line where your bottom rail curve meets the bottom of the board. This is done by making smooth, long strokes with your sanding block without changing the angle of the block as you are blending the underside rail band into the bottom of the blank. Remember to be careful toward the tail of the board, where you want to maintain that 90 degree sharp edge.


Once you have broken down all of your rail bands, it’s time to smooth the remaining small bands into a nice, round final rail shape. For this step, most shapers SandShark sanding screen, pulling the screen back and forth over the rails to smooth out the remaining bands into a nice clean curve. Take your time with the sanding screen and don’t pull/push too hard. The screen can remove a lot of material quickly if you are putting too much pressure on it. Start by screening the top side rail, then the bottom side rail. Finally, quickly smooth out the top and bottom at the same time by wrapping the entire rail with the screen to radius the entire rail smoothly. Remember to use a light touch here, as removing material from the former vertical band will change the outline of your board. 



At this stage, you are in the home stretch of the shaping your board. All that is left to do is do a quick smoothing of the entire shape with a soft sanding pad and medium grit sandpaper (80 grit) or sanding screen.  You can screen the board with progressive grits to tighten up the small voids or simple seal the board with sealing spackle at this point if shaping EPS foam (see below). Start with 100 grit and progress to 150 and 220 for a really smooth board that will look great under a tinted lamination.

When final sanding, use a surfboard shaping foam sanding pad and hold the sandpaper or screen under the pad by folding one corner of the pad up and grasping the screen with your fingers on one hand while the other hand presses down on the pad and screen to sand. Holding the leading edge of the pad up will stop the screen from rolling over and scratching your board. Keep the pressure light, as you don’t want to remove much foam at this stage. You just want to smooth everything out and get rid of any rough spots.

This is also a good time to sand away any pencil/Sharpie marks that are still on the blank. Just be sure to sand lightly to avoid making dents in the blank. Now is also a good time to check your stringer one more time and plane high spots flush to the foam with a spoke shave.

Sealing the Blank (Optional)

Sealing the EPS blank is optional but we recommend it to make your board look great while eliminating a lot of fine sanding and screening. This smoothes out any holes, provides a nice white surface for artwork, and seals up the pores of the blank so it doesn’t absorb too much resin when you are glassing. Our Engineered EPS doesn’t need to be sealed as it will not have as much bead tear out as other EPS foams, but if you want a clean looking white board, painting the blank, or tinting the resin, here’s how:

Use a bag of our EPS Surfboard Sealing Spackle (one bag will seal a board up to ~7'0" long). It is bright white and light, so is the preferred spackle for sealing EPS blanks. Scoop a hunk of spackle into a mixing cup, and add a little bit of bottled or distilled water (NOT TAP WATER - the minerals in tap water will turn the spackle yellow) to the mix to turn the spackle into a whipped cream consistency.

Pour this water/spackle mixture over your blank and spread it around smoothly and thinly over the surface of your blank with an epoxy spreader.  Scrape off the excess spackle back into your mixing bucket, as you can re-use it for the other side of your board. If you have any small dings or chunks missing from the blank (common in the stringer area), you can fill these holes with the spackle.

The idea is to just fill the small voids in the foam and not put a thick later on the board. Scraping the spackle off with the epoxy spreader will take all the excess off and leave just what is needed in the holes. 

You can apply the spackle to the rails with your hands and just glob it on since your hand can conform to the rail shape easily. Then follow with the epoxy spreader to clean it up.

Allow the spackle to dry, flip the blank over, and repeat the process on the other side. Just add a bit more water to your old spackle mix and it should be ready to go again. Once the spackle is dry, you can lightly sand the entire blank with a soft sanding pad and 220 grit sanding screen or sandpaper.



If you choose to install FCS Fusion, FCS II, or Futures fin boxes now is the time.. Installation of these fin systems requires a trim router and install jig designed specifically for each fin system. You also have the choice to use FCS X-2 plugs or FACTORY plugs and install them after glassing the surfboard is done.

Fin installation starts with laying out where the fins will go before routing the pockets. Greenlight's Versa-Square or G-square layout tools do the work for you to ensure proper fin alignment and toe in angles. 

Click to download Greenlight's Surfboard Fin Position Layout Guide for tri-fin, quad, and 2+1 fin setups


Fin placement is always measured from the tip of the surfboard's tail and a certain distance "in from the rail" as shown in the fin placement guide.

There is a lot of detailed installation instructions for each fin system and how to videos on the product page links below:

How to Install FCS Fusion Fin Boxes

How to Install FCS II Fin Boxes

How to Install Futures Fin Boxes

*Glass-on fins are attached to the surfboard after the fiberglass lamination is complete, but before the hotcoat.

Download Greenlight's Glass-on Fin Cant template here




Before you glass your board, you have the option of preparing a few cosmetic touches to your blank. This is the stage where you would airbrush or paint the foam blank and it is also the stage you would design and print any logos that you want to laminate under the fiberglass.


We are not going to give detailed advice on airbrushing or painting your blank, since it is primarily a creative process. However, there are a few things you need to know if you are going to airbrush or paint your blank. For airbrushing, you should use water-based tempera surfboard paint. You will also need an airbrush and compressor. If you plan on spray-painting your blank with a rattle-can, you must also use water-based spray-paint, especially on EPS blanks. Regular spray-paint contains styrene, which will literally melt your EPS blank. Water-based poster paint has proven to be the best for surfboards for durability and to ensure a good bond between the blank and the fiberglass/resin.

There are some great airbrushing videos on YouTube and also a great airbrushing DVD in JC’s 101 DVD Series if you want to get a detailed look on ideas and details for airbrushing your blank.


If you would like to put some logos under your laminate, you can design them on your computer and print them out using Greenlight’s Logo Printer Paper.  Once you have designed your logo, set your ink-jet printer to print on medium resolution. You need to tape the Logo Printer Paper to a regular sheet of paper, and manually feed this paper into your printer. Make sure the logo paper is facing the proper direction to receive the ink jet ink.

Once the logos are printed, remove the logo paper from the backing paper and cut the artwork/logo out leaving a small margin around the design. You should print as many logos as you can on each piece of logo paper, since you can only send it through the printer once. Details on laminating the logo into your glass-job will come up in the Glassing section of this guide.

Next Page: How to Glass a Surfboard


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