This has been my most ambitious 3D Printing project yet. There have been other people who have 3D printed a surfboard before but not like this. I wanted the surfboard to have a full color "skin" and be surf-able and not something to hang on a wall.

So I started this project last year and I just finished it, a lot of time was spent designing and then test printing.

Before this, I had almost no experience with 3D design, except printing other people's designs. So I had to figure out how to design the surfboard in CAD (lucky there is software to do this) and learn how to cut it apart for printing. Sounds simple but it took a lot of time to design, test repeat, as Adam Savage says creation is iteration!

One thing I do have is experience with making surfboards and traditional techniques, so I bring that knowledge and apply it to designing this surfboard.

Some stats about this 3D printed surfboard project:

Total Weight before fiberglassing: 6.90 lbs (3.1 kg)
Final Weight after fiberglassing: 13.9 lbs (6.3 kg)
Total Time Printing: 218.47 Hours or over 9 full days of printing.
Total Cost to Print in Electricity: $5.24 (@ 2.4 cents per hour to run the printer)
Total Cost of 3D Filament: $150
Total length of filament used: 1050 meters
95 Individual Pieces and a lot of alignment pins.
Dimensions of the surfboard: 6'4" x 20" x 2 5/8"
Volume of the board: 37 litres

Took just over three 1 kg spools of filament but with all the testing five rolls were used and I estimate at least 100 hours of test printing that does not factor in the total time printing for the finished surfboard. I have no idea how many hours I spent designing hunched over my computer.

I wanted to actually get out and surf this before posting this Instructable but due to Covid19, getting out to the beach locally is not possible for a while. Also I posted a build video at the end of this Instructable if you want to check it out.

I have shared my project files on Thingiverse. I don't expect anyone to actually to print and surf it but it might make for a cool object to hang on your wall. If you like this Instructable, vote for me in the 3D printing contest :)

https://www.thingiverse.com/thing:4274699

Also I provide and update at the end of the Instructable since initially posting this on how well the board is holding up.

Step 1: Equipment, Materials, Software

This is just a basic list of what I used, I'm sure I forgot stuff

Equipment

Anycubic Mega-S 3D Printer (Affiliate Link: https://amzn.to/2x4bop9)
Equipment to glass a surfboard (I have another Instructable on how to do this)
Dial or Digital Caliper for Measuring (Affiliate Link: https://amzn.to/2RtnDTp)

Materials

PLA Filament (5 rolls)
Weld-on 16 (best glue for PLA)
Materials to glass a surfboard

Software

The software I used to design and print:

AKU Shaper http://www.akushaper.com/
Meshmixer http://www.meshmixer.com/
Cura https://ultimaker.com/software/ultimaker-cura
Tinkercad https://www.tinkercad.com/

Step 2: Theory and Design

Background

Essentially what I am making is a surfboard blank. A surfboard blank is typically a block of foam that is the main support structure for a surfboard. The blank is shaped into a final surfboard design and then the surfboard is covered with fiberglass and resin.

What I did was replace the foam with a 3D printed "blank" that was designed in CAD. So how did I do this? Well lucky for me there is software out there to design surfboards that is used in the surfboard industry. So lets talk a little about how I came up with my design.

Design Challenges and Theory

Most of the designs that I have come across, use a honeycomb structure frame and then they put fiberglass over it. The advantages of this type of design is it is very light and strong as vertical braces that are spaced closely are very strong. However there is a balancing act to this, if you space the honeycomb structure to closely the surfboard will be very strong but it will be heavy. Space the gaps to far apart and it won't be very strong and the fiberglass will get crushed from your feet.

My idea for a 3D printed surfboard was to have the filament be the color the surfboard, in my case I wanted to try red. This inherently has some design challenges, firstly the board must be hollow or else it will be way too heavy. A big issue with a hollow surfboard is if it is not vented the board will be like a big balloon. The air inside the board will expand or contract depending on the temperature. When the board heats up the air expands and it has to go somewhere. If the surfboard is not vented the surfboard will have big problems with delamination of the fiberglass skin.

Things to Consider When Designing
What a decent surfboard should:

Be light (exceptions to this of course but generally speaking)
Durable
Perform the way it was designed

I'm not a 3D modeler so this leaves me with a few issues, I was not sure how to take a huge object like a surfboard and make it printable on a consumer 3D printer. The idea was simple enough, I would cut the surfboard apart, hollow out the pieces, add alignment pins and then print. To get to final printable pieces took a lot of trial and error.

My Design

My design is far from perfect and I like to think that this is just revision 1.0 but it works. I'm sure someone with proper 3D design experience could make a better model for printing.

I designed my surfboard in AKU Shaper, it's software used in surfboard manufacturing and will interface with CNC machines to shape surfboard. What makes it great is I can design the surfboard 2D profiles, make changes and view what it looks like in 3D. I think this would be considered parametric design.

You can even import a picture of an existing surfboard and use it to trace the outline. I ended up designing a retro looking surfboard, I really like that style of surfboard. Dimensions are: 6'4" x 20" x 3" (Length x Wide x Thickness)

I could have designed a smaller surfboard to cut down print time but I wanted something that I could reasonably ride.

What made designing this surfboard so easy with this software is I could export it as an STL file that would be ready for 3D printing, provided you either had a printer big enough or scale it down.

I did scale the surfboard down and do a test print to make sure the STL had no mesh issues.

Step 3: Cutting the STL Model Surfboard Apart

Cutting the Model Apart

So here comes the fun part, how to cut the full size model down into parts that could be printed. My print area is 210 x 210 x 205 mm, so each part must be smaller than that.

Lets just say that I spent A LOT of time iterating and testing this process. If anyone is familiar with agile development this was a good test of that methodology.

My constraints or requirements are:

keep the pieces light
keep the pieces strong and rigid
print in a reasonable amount of time
be able to vent every piece of the surfboard

To solve the issue of keeping the pieces light yet strong and rigid I had to cut the model up (using Meshmixer) by keeping the pieces small enough so they didn't flex too much since they would be hollow. I did a lot of experimenting with this and ideally if someone was good enough with CAD, they could cut the model up and include or model support structures inside each piece but not have them all connect together.

The reason I say not connect all together is if you have any experience with using slicing software like Cura, PrusaSlicer, Simplify3D etc. The slicing software will automatically set the infill for you so there is lots of support. The issue is the way these programs add infill is they make sure to support the print but it doesn't optimize for hollowing it to be a single air chamber, if that makes any sense. As I need to be able to vent each piece of the surfboard.

I tried playing with setting the infill to 1%, 2%, 5% and higher, what I found was either there was too much infill (too heavy but very strong) or the infill was not contiguous (hard to vent). An added complication was I had to connect each piece of the surfboard to each other so I make one continuous hollow chamber, so I could vent it with one vent. I thought about drilling holes through all the infill but when I increased the infill amount the infill designs were too complicated. My solution is explained later.

Solution - sort of

What I ended up doing was using Meshmixer to cut apart the model, using the plane cut feature. I had to make sure not to make the pieces too big or else they would flex too much since they would be all completely hollow with the edges of each piece providing the support.

Cutting the model apart took some trial and error as I did not want to print the model using supports, this would add extra print and waste. I found the best way was to make sure to keep the pieces cut like triangles as you can print at a 45 degree angle with no supports (since the pieces will be hollow), anything less than that the "overhang" may need supports to print correctly. As an example, try printing a hollow cube, the top will collapse as you are printing over air (called "bridging"), unless you use supports.

Alignment Pins and Venting
While designing the cutting and hollowing of the surfboard pieces I kept in mind how I would vent the surfboard, as that was the main reason why I had the above mentioned issues or else I could have just printed with less infill.

To make assembly of the surfboard pieces I added alignment pins for each piece, two pins per side on average, times 95 pieces times 3 sides per piece equals a lot of repetitive work. The pins are a cylinder primitive in Meshmixer sized to 10 mm.

I then manually aligned the pins on each piece and using the "boolean difference" function to subtract the pin shape from the piece of the surfboard. This is not a trivial task as they have to match up exactly between each piece, it's not hard to do, just making a mistake means having to go back and reprinting the pieces later.

Each pin had a hole through the center of it, this connects each individual piece of the surfboard to the other forming a connected continuous chamber. The actual pins were resized to 15% smaller in diameter than the hole they would fill to account for any tolerance issues. I actually modeled the hollow pins in Tinkercad and adjust as needed until I had a pin that fit right.

After adding alignment pins I used the "hollow" function and tested what was the minimum thickness I could get away with for the "skin" or "shell". 1 mm was a good all around thickness but after doing some test printing and calculations the board would be too heavy. So I ended up with 0.75 mm but the issue with this and I only realized it after I had a lot of the surfboard printed was parts of it were almost too thin where the pieces had a lot of curve to it like for the deck of the surfboard.

When I printed the surfboard at 1.25 mm, it was very strong, almost wouldn't need to fiberglass it (of course it wouldn't be water tight) but it would use a lot of filament and be very heavy, so I scratched that idea. Also it looked really good because there was no flex to the pieces. The skin being 0.75 mm was at the limit of what was acceptable in my opinion, like I said if there was a way to model supports manually in each piece that would be idea.

At this point I test printed at least a roll of filament, between testing different infills and hollowing, I actually lost count as I was using different colors but I had many boxes of test or failed printed. I even tested out using larger nozzle sizes.

Once I was happy with the slicing and hollowing, I also added to the bottom of the surfboard two holes for vent and leach plugs using Meshmixer.

Finalized Process

So what I ended up with was the following steps:

Import the STL surfboard model into Meshmixer.
Cut the model into pieces, keeping to the triangle rule (see above)
Add alignment pins between all the pieces
Hollow out each piece of the surfboard
Export each piece as an STL file.
Import into Cura to slice the file for printing and export as Gcode.

I should also mention since I was dealing with so many pieces, a naming convention is super important for the exported pieces. I did it by row and then a number for each piece, I will use this as reference to label each piece once they are printed.

Step 4: Slicing and Printing

Slicing

Before the pieces can be printed they need to be sliced for printing. This is not to be confused with cutting up the surfboard for printing. Slicing is a term used in the 3D printing world for preparing a 3D model for printing. The slicing software takes the file and "slices" it into Gcode that it can be interpreted by the 3D printer as movements for printing. I'm sure someone can explain it better than that but that's the basics.

The software I am using is Cura but there are lots of them out there. In the slicing software you can adjust all kinds of settings for printing. Such as temperature, speed of printing, support, infill etc...

I modified the Draft print setting in Cura and made my own profile for printing the surfboard pieces, the basic settings I used are the following:

100 % infill,
Hotend Temp: 210 C (I printed hotter to ensure lots of adhesion between the layers because the walls were so thin)
No Support
Build Plate Adhesion Skirt
Built Plate Temp: 60 C

The reason for the 100% infill is I hollowed out the pieces myself and am controlling the density of each piece myself. I want the wall to be 100% solid, in actuality setting the infill value lower doesn't change the density of the pieces, the wall line count and top and bottom layers are more important. Honestly the shell thickness I just left them the default value and they worked fine. I experimented with the changing the shell values but it didn't make much of a difference.

Lots of testing occurred here with many test prints. Once I was happy with the slicer settings it was time to start printing.

Printing

The printing was pretty simple once I got all the previous steps figured out. For the filament I chose a nice red as I thought it would look cool. In hindsight, I would have picked a lighter color for when I fiberglass the surfboard from an aesthetics point of view. I will explain this more later as it has nothing to do with 3D printing but the properties of the epoxy resin.

As each print was completed i would label the print by row and number. This was just so I could easily organized them for assembly once I was ready. During the printing process I also test assembled sections to make sure the alignment of the pins was good.

Surfboard Fins

Someone on Thingiverse was nice enough to post a set of standard surfboard fins ready to be printed, so I printed them off (removing the mounts). (I can't seem to find the link anymore). The other option was to use photogrammetry and try to scan and model set of fins for 3D printing. These fins will be attached later when fiberglassing. Update - Also I recently found this set of fins https://www.matterhackers.com/articles/design-lab-3d-printing-surfboard-fins

Step 5: Glue and Assembly

Glue

I did a bunch of testing to see what glue was the best for PLA plastic and turns out there are few different types of glue that will work but there was a clear winner: Weld-On 16. This is a glue made specifically for gluing acrylics and polycarbonates together. It's sold by companies that sell plastic sheets for construction and commercial use. Also the stuff gives off some vapors so it's best to use it in a well ventilated area while the glue dries.

What makes it work so well is no sanding is required to rough up the surfaces as Weld-On 16 will slightly melt the PLA so it creates a weld between the pieces. The glue itself isn't strong, it's the melting of the PLA that makes it strong.

A suitable substitute also would be Cyanoacrylates (CA) glue. Other glue would work but either the drying time or surface preparation would take too long.

Assembly

The assembly of the surfboard was my favorite part, this is where all the planning and designing comes together.

Before any glue was applied, I laid out all the pieces of the surfboard and test fitted each piece to the one next to it. Surprisingly all 95 pieces fit!

Since each piece of the surfboard was a self-contained hollow chamber, they had to be connected together for venting. This is where the alignment pins comes in, besides making aligning up all the pieces easy, I used them as a way to connect each piece together to form one big air chamber. Every alignment hole had a hole drilled in it and as mentioned earlier the alignment pins were printed with a hole through each one.

I started gluing together the pieces using Weld-On 16 to make each of the rows first, in total there were 17 rows. To hold each piece in place while the glue set I tried a few different clamps but what worked the best was using pieces of duct tape to hole them in place, specially Gorilla tape (has excellent adhesive that holds but also leaves no residual when removing). This took a few days of gluing.

Then starting from the bottom I started gluing each row together. There really wasn't anything special with this part. Insert pins, apply glue, put pieces together, apply clamping tape, repeat.

I should mention that if the pins were a bit hard to insert into the alignment holes I used a heated metal rod to slightly melt and burnish the sides of the hole. I did this outside to keep the small amount of fumes out of the house, funny melted PLA smells sweet (PLA is made from fermented corn starch essentially).

I let the assembled surfboard sit for 24 hours before removing the tape.

Step 6: Lessons Learned and Final 3D Printed Surfboard Pictures

Lessons Learned

As a project this was a super challenging. I lost count of how many hours this took in total but I really enjoyed the challenge of trying to do this. Designing something on the computer and being able to send it to a machine that can replicate physically is amazing. So a few of the things I would do differently:

Try printing a smaller surfboard before taking on a such a large object.
Increase the thickness of the skin to 0.09 mm or 1 mm, the reason for this is some of the pieces had "divots" as the skin was almost too thin and the distance between the edges of the pieces were a bit too long so "bridging" these areas at 0.75 mm did not leave enough material to support itself. When the pieces are printed with a thicker skin, there is no issue with this and the surfboard looks really good (I test printed a whole row and assembled).
Find another way to slicer apart the surfboard or
Cut the pieces smaller to help avoid the problem with the surface "divots",
Design the surfboard in something like Soildworks and add support structures

Final Pictures before Glassing

So technically the surfboard is finished from a 3D printing point of view. It looks amazing and is actually very light but it is delicate. On it's own it's not water tight and not strong enough to be surfed. Essentially what I created was a finished shaped surfboard blank in place of a foam or wooden one. So if you are here for the 3D printing information of this project you can stop here.

However I'm not finished and I'm including a short write up about getting this surfboard ready so it can actually be surfed in the water. So the project continues!

Step 7: Traditional Surfboard Building

So to finish the surfboard I used traditional surfboard building techniques, using fiberglass and resin (polyester or epoxy). This is where I have lots of experience but because this surfboard is 3D printed there were a few additional challenges (of course there is LOL).

The things that made this surfboard harder to fiberglass:

The surface of the PLA is smooth, adhesion for the epoxy could be a challenge
The "divots" creates low spots that is not ideal for sanding the surfboard smooth and
I did some testing and I needed to use 3 layers of fiberglass on the deck to make sure it would stand up to the punishment of my feet hitting them when surfing
Epoxy pools in those spots that create thicker spots

Again more testing was done to see how well PLA would take a fiberglass job and it seemed that it would hold well.

I have created other Instructables on how to fiberglass a surfboard so if you are interested you can go check those out. For the sake of brevity I will just do a high level overview of what I did and the issues I ran into with this project.

Fiberglassing a surfboard is the process of covering the surfboard blank with layers of fiberglass and then saturating the it with a resin, either polyester or epoxy. I am using epoxy for this surfboard build because it's what I have on hand and it's very strong compared to polyester resin.

So are here are the high level steps:

Shape a surfboard blank, in this case the 3D printed surfboard
1. Prep the surface of the surfboard blank by wiping it down with acetone or alcohol.
2. Cover bottom of the surfboard with fiberglass cloth
3. Saturate the fiberglass with epoxy resin, let harden, clean up the edges of the fiberglass
4. Cover the deck of the surfboard with fiberglass cloth
5. Repeat step 4
6. Attach surfboard fins to the board using some hot glue to hold them in place. Apply fiberglass to them and saturate them with epoxy and trim off excess when hardened
7. Install the vent and leash plugs
8. Apply a piece of tape around the middle part of the rail of the surfboard
9. Apply a layer of epoxy resin to the deck of the surfboard (called hotcoating), let harden, pull the tape
10. Apply a layer of tape at the midpoint of the rail, overlapping the layer epoxy from step 8
11. Apply a layer or epoxy resin to the bottom of the surfboard
12. Sand and polish epoxy

A few things to note after fiberglassing and coating the surfboard. The board doesn't look as good as it did before fiberglassing because the diviots makes it hard to sand the whole surface smooth and the trapped air bubbles in the epoxy that is introduced into the mixture when mixing are visible as a cloudy layer (very hard not to mix in air).

Also the pooling of the epoxy and the dark red color of the surfboard makes the little tiny air bubbles show up even more than on a lighter color. There are a few ways to avoid this:

Use a lighter color filament
Try not to have divots in the surfboard
Use a vacuum chamber to remove the bubbles from the epoxy after mixing (there are timing issues when doing this)

Regardless, the fiberglassing made the 3d printed surfboard super strong. I was worried that it could be dented but it's not a problem. I can hit the deck really hard with a hammerfist to mimic my feet hitting the deck after popping up on the board when surfing and holds up with no issues. Also the weight of the board is still very reasonable.

Step 8: Summary and Video

The 3D printed surfboard took months of planning, designing, testing, printing and building but I had a blast making this and I am already thinking about how I can improve upon this and will try this again, this is version 1.0. The real only issue is the aesthetics of the board, regardless the weight, strength and performance of the board I except is the same as a regular surfboard.

So I finished this board back in February and it has been too cold to get out to test surf it and now that winter is ending I still can't get out to test it due to the situation with Covid19. Lets hope things calm down by the summer and when I get a chance to test ride it I will post a video on how to make this surfboard and will amend the Instructable once I finish that.

If you made it this far and enjoy this project, please consider voting for me in the 3D printed contest!

Also I got around to making a video for the build of this surfboard, hope you enjoy it.

Update 2019-05-22: The beaches have reopened and I got out to at least test the board, haven't had it in good surf yet and the water temp was 4 C, so not exactly tropical. Regardless I can report that this board floats fine, paddles well and my glassing job held up with no de-laminations. The waves were a bit mushy and it was hard to get any good rides with it yet. The board is best suited to clean powerful waves, due to the thinness.

So this is a totally viable way to make a surfboard, who would have thought!

The way to improve upon this design I think is to increase the wall thickness of the skin, so the board isn't as lumpy looking. Also printing it with PETG or a satin finish filament should give maximum adhesion to the epoxy and fiberglass. I am definitely going to iterate and make another board like this!