Introduction: Foam Core Kiteboard

Learn to make your own foam core fiberglass kiteboard! This will provide you with a stylish lightweight ride at a fraction of the cost of commercial boards.

The price of boards seems to have skyrocketed here in Canada over the last season. Why buy what you can easily make? This is a great beginner fiberglass project that allows for tons of creativity and fun.

Step 1: Materials and Tools

- 3/8 in 4ft x 4ft Core-cell or Dyvini-cell foam. $40 CAD
These can be found at marine supply stores and generally come in 4ft x 8ft sheets. Look for appropriately sized 'scraps' to save money. I found the core-cell to be extremely durable and resistant to dings while building.

- 3m x 1.5m of 6 ounce bidirectional fiberglass. $22 CAD
This should be enough to put 3 layers of glass on the top and bottom of the board.

- 30cm x 50cm uni-directional carbon fiber. $9 CAD
This will provide added support under the foot straps.

-1.25L of Marine Epoxy. $55CAD
West Systems 105 and 205 Resin and Hardener worked very well for me. The pumps made measuring the correct ratio of Resin to Hardener a breeze and allowed me to work with smaller amounts of epoxy at once.
-Glass micro bubbles. Commonly referred to as 'Micro'. These are mixed into the epoxy as filler and result in lighter weight. Use a mask so you don't inhale.

-Hardware $10 CAD
-Stainless threaded inserts for the foot straps and grab handle
-Stainless Screws for the foot straps, handle and fins.
-finishing washers for the fins

-Fins and Footstraps
This is where things can get expensive. Foot straps are easy to build. See some of the other great instructables for more information on making your own. I found old Dakine ones for 30$. One can probably get away without fins. Fiberglass kite fins sell for roughly $150 CAD, I found plastic ones for $50 CAD. There is also the possibility of shaping fins into the foam as you see on some wakeboards.

A one or two part polyurethane should do the trick. Forget about spray paint.

-Utility Knife
-Scrap wood
-Old credit card type plastic card for spreading epoxy.

Step 2: Design the Shape

You can draw it by hand, you can use CAD, there are no rules. There is a great idea in the instructable for the plywood kiteboard involving CAD and a large printer.

The approach I took involved creating an elipse in Maplesoft 11, then transferring the equation to excel and solving for points every 5cm. I plotted these on the foam myself and connected the dots with a pencil then a knife.

You will see that the board in this project has two layers of foam epoxied together. This was done to save on the cost of the thicker core cell foam. Foam was cut out of the upper layer near the tips to provide more flex.

The equations for the lower and upper ellipses used here are:

Put these into excel with 'x' as points every 5cm from the origin and voila. The board here is 136cm long and 44cm wide.

Step 3: Cut the Foam

Cut along the lines you've traced out onto the foam. Fiberglass cannot be layed around a 90degree edge. Use a power sander or a knife to round down the edges of the upper layer of foam so that they meet the lower layer and the glass will not have to round any sharp corners.

For the lower layer of foam one could leave the edges flat and simply lay the glass to the edge of the board and not around it. I chose to shave the foam to a sharp edge (this could come back to haunt me) and have the top and bottom layers of glass meet.

I found shaving off the core-cell foam with the knife to be the most effective means. Remember to always cut away from yourself! Sanding this foam down will take a long time but it works well for finishing the knife-cut surfaces.

Step 4: Glue the Foam Together

Mix the Micro into the epoxy in a 1:1 ratio and use this to glue down the sheets of foam together. You may need to use weights to hold the sheets together as it dries.

Mix 2 parts volume of micro with 1 part epoxy and thinly spread this over the foam. This will fill any perforations in the foam and provide a good surface for the glass to bond to.

Mix 3+ parts volume of micro with 1 part epoxy and use this thicker mixture to fill around the edges where the lower sheet of foam meets the upper sheet. This will provide a rounded 'fillet' transition for the glass to bond to rather than sharp corners.

Step 5: Add the Threaded Inserts

Mark down the desired locations for the inserts where the foot straps and grab handle will screw into. If you're going to be adding fins mark down where the screws will pass through the board and where the fins will sit.

Use the dremel to cut out foam where the inserts will sit. Do not cut all the way through the foam. With the screws inside the inserts place them in the board and fill with a 2:1 mixture of micro and epoxy.

For the fin screws simply dremel out where the screws will pass through and fill it with the same mixture of micro and epoxy. This way the screws will be passing through epoxy and not just foam.

If you are concerned about the strength of the inserts leave out the micro from the epoxy you are using to secure them. Same with the fin inserts. The micro does save weight and expensive epoxy though.

Step 6: Cut Out Your Glass

Lay the foam board on the glass and cut around it leaving a decent (5+cm) margin of glass around the edges. Do this so that 2 of 3 layers of the glass that will cover the top and bottom sides of the board have one of their weaves running parallel to the length of the board. For the other layer on each side of the board have the weaves running each at 45 degrees to the length of the board. You may ultimately chose the direction of the weaves and number of layers at your discretion but make sure to have some weaves running lengthwise.

Step 7: Pull in the Rocker

The rocker is the deflection from the center of the board to each tip. A larger rocker will keep the nose of the kite board out of the water more but this may come at the cost of up wind performance. Many people build boards without any rocker at all. I used a small 2.5 cm rocker, that is the tip is 2.5cm higher than the center of the board.

Some board also have a small amount of concave. Think of the inside of a waterski. The outside edges on the sides of the board are lower down than the center of the board. Due to the added complexity and lack of necessity a concave was not added to this board.

To pull in the rocker for fiberglassing find a scrap piece of wood that is at least the length of the board. Use Screws to attach the foam to the scrap wood where the screws for the fins would normally pass through. You will have to drill pilot holes through the epoxy. You can probably use the screws for the fins to do this job. If you are using other screws make sure they are smaller than the diameter of those used for the fins. Now wedge pieces of wood between the foam and board to give the desired curve.

Step 8: Start Fibreglassing the Bottom

Use the credit card to spread a thin layer of epoxy on the foam (which is still screwed into the board). Now lay down your layer first layer of glass as evenly as possibly, try not to bend or warp the fibers to get them flat. Keep the longitudinal weaves as straight as possible. Now start wetting it out. Mix small amounts of epoxy to work with as required and use the credit card to spread it over the glass. Use as little as possible while still completely wetting out the glass. Excess epoxy is only non structural weight.

Now repeat with the other layers. Once the glass has dried trim it so there is only a slight overhang on the edges

Step 9: Glass the Top of the Board

Once the bottom has completely hardened you may remove the kiteboard from the scrap wood and it will hold its shape. Put Vaseline into the inserts so they don't fill with epoxy and begin glassing the top. I used two thinner layers of 4 ounce glass and 1 layer of 6 ounce on the top of this board. The thinner glass was easier to have conform to the shapes on the top of my board without lifting up around the corners. The micro-fillets added early help with this problem.

Here is where you can add the carbon fiber over where the foot pads will be.

Once everything has hardened trim the glass down with scissors. Then using the dremel with a grinding bit, cut the hardened glass around the edge of the board. This will produce a lot of dust so wear a mask! Now sand the edge of the board gently to shape and seal it with a coat of epoxy.

Use the dremel to cut out the glass over the inserts and drill the holes for the fin screws. Make sure everything fits.

Step 10: Paint the Board

Forget the spray paint, i tried it and it peeled off right away and left me with a mess to sand off. Go pick up some purpose designed paint (fiberglass covering) at your local marine supply store. Paint on cool designs (something I haven't done yet).

My sister's yoga pad worked really well for the foot pads. She hasn't noticed that its been shortened 12 inches yet.

Screw in whatever type of strap you can find for the grab handle (not shown). If you've measured the holes correctly you can use a commercial handle.

Step 11: Enjoy

Get those boardshorts on over that wetsuit and go tear it up! This design has worked very well compared with the limited number of commercial boards i've ridden.

If you have any questions or comments please send them my way.

If you've built something like this yourself and have any tips please contribute! I will definitely be making more boards myself (careful its addictive) and would love more advice.

Good luck!

Step 12: Make More!

This time I pre-designed in Solidworks and built a rocker table. Then I followed the same steps as before and used a vacuum bag. Voila! Super Strong and Super light weight.
The fins are made from the rapid prototyper at work. Was going to use them for a mold but they were so strong that they worked on their own. There is a little wax left over.
In conclusion: board building is addictive. Proceed with caution

Step 13: More Pictures of the Vacuum Bag Process

Here are some pictures I jacked from my friend Eric of us building the second generation of kiteboards last year. This time we tried vacuum bagging and it worked really nicely. We use a small 1/3 horsepower motor with a regulator valve and a pressure gauge to suck down to about -12 Psi while the epoxy cured. 

On each side of the board we had a layer of Nylon, a cloth bleeder to allow airflow and absorb excess epoxy and then the plastic bag itself. This gave a much nicer nylon finish than the last board which still showed the weave.

We also used colorant in the epoxy. This worked well and saved us from having to paint the boards later. It also saved weight. The sun will slowly deteriorate epoxy but if you don't store your board in your backyard you should be fine.

Eric also bought some fabric a layed it in under the last layer of glass. This gave him a sweet pattern on the surfaces at the expense of a small amount of weight. 

This time we were a little more confident in the process and invested in some better bindings. These amounted to about 70% of the cost of each of our boards.

Step 14:

I was thinking about making a new instructable for kite-surfboards but there is already so much information out there on the internet. I'm still considering it as it might benefit those like me who don't want the 100% solution which takes much more time, tools and expense and will settle for the 95%. Here is a quick overview of the process. If you want more detail let me know.

This is a 5ft 8in fish style board i built for light wind and for the 10 days or so every summer where the waves get big enough to surf at Sandbanks provincial park (and you can actually make it out to surf them). I forgot to take pictures over some of the earlier steps but they are pretty similar to the other boards, just more shaping. 

1. To start do a rough drawing of the board in CAD I copied a friend's real kite-surfboard (can you guess which one?) and added a few minor changes. From there  print out templates of the top and side views of the board.

2. A big block of blue PU (polyurethane) foam works nicely. I hear expanded polystyrene is more desirable but i had the foam left over from another project. Use the templates to wire cut out the two dimensional shapes from each side. I can't really think of a way to do this conveniently without a wire cutter. You can always buy blank foam cores for surfboards. Wire cutters are pretty easy to make, in fact someone has documented the process on this website.

3. From there, you spend a couple of hours sanding the contours around the edges of the board going as slowly and patiently as you can. I'd recommend forcing yourself to take breaks every half an hour. If you're having a bad day stay far far away from this project. Your frustration will show in the final shape. Doing this in good lighting will make a world of difference as you will be able to perceive the curves much easier.

4. Unless you are using carbon fiber, glue a thin sheet of corecell foam to the upper deck with epoxy. This will stop your feet from depressing into the soft PU foam and distribute the load. It will also hold the inserts in nicely. If you want footstraps add the inserts on the top of the deck on the centerline. I sanded this down so it met the shape of the blue foam and filled the edges with micro bubbles to blend as much as possible. Now draw the centerline down the top and bottom surfaces.

5. Now simply lay up the bottom surface of the board as is shown for the other boards in this instructable. I used 2 layers of 4oz bidirectional cloth and then one layer of 6oz tight weave on the surface. The tight weave doesn't like to conform around the edges as much but it makes finishing the surface much easier and requires less filling.

6. Once dry, trip the excess fabric overhanging around the rails with a dremel and then blend the cut edges of fiberglass into the foam with micro. Now lay up the top surface the same way. When its dry, trim the edges and blend them onto the later below. Vacuum bagging each layup is optional but it will help the glass adhere to the foam. The tight weave was hard to spread bubbles out of and the vacuum will help.

*Tip: turn off your cell phone. This way your girlfriend can't call you stranded at the carpool on her way home from work because she forgot her keys. Getting a vacuum bag to seal nicely requires your complete attention and you have to make sure there are no leaks while it pumps down. Mine had leaks, I had a few small bubbles on the bottom surface which i had to cut out and fill. 

7. Make a template for where you want to position your fins relative to the centerline of the board. Again, I copied my fin positioning from a real life board (no point in reinventing the wheel). Trace it on to the board and cut out the holes for the fin inserts. I bought a set of FCS quads and inserts to hold them. This contributed about 80% of the cost of the board as I was using left over foam and epoxy. Put the fins in the inserts and then position them in the board as desired. A square ruler is a nice way to measure the tips relative to the centerline. Use tape to hold them in place as shown. Pour in some epoxy. When it is set, remove the fins and fill the rest of the hold with epoxy/micro up to the surface. Cover the fin and screw holes with tape so none gets in there.

8. You are nearly done! Add, at your discretion, add a thin layer of micro over all the surfaces to make them smooth. Sand it down smooth. Add the gloss coat of colored epoxy (if you want to go the colored epoxy route, use it throughout the project). I found going around the edges with a squeegee annoying so i painted on epoxy with a foam brush. This produced small bubbles in the surface. I bet a normal paint brush would work better. Please post if you know..

9. Getting a nice finish on a fiberglass product without the use of molds is tough! I found my edges were not completely smooth where epoxy had accumulated in some places. At the cost of a fully glossy finish I sanded along the edges to make them smoother and then wet sanded them and other imperfections. You can see the dull grey finish in some places. In the end its really about performance. 

10. Wait until the winter rolls through in Canada to ride your new board. Better yet go on vacation!