I'm building a 6'4'' Hollow Core Cardboard Fish

I’ve been working on a 6’4’’ Fish, made from router cuts in cardboard that Mike Sheldrake, the inventor of this board design creates in his garage.  This board is unique in the way its designed, its core materials, and that it is being built in the Marshall Islands.  Ive had the board kit for over 3 months, waiting on supplies.  Now that they are here I have spent a few solid days getting it to the glassing stage.  A few pictures to show where its headed. 

Im not the first person to built this board kit.  One other person, Nick in New South Wales beat me to it. I am impressed.


There is a back story to my kit.  It goes- Nick (the other Nick in New South Wales…doppleganger!), built this same board kit a few months back.  He originally ordered the kit and had it mailed to his apartment complex in AU. It never made it to his doorstep.  It was lost in the mail.  Meanwhile Mike was in his lab, building up another kit for Nick in New South Wales.  He sent it out, and soon enough the original kit landed back at Mikes doorstep.  Mike posted the board on his site, by chance I saw this and bought it.

I began deciding on the supplies I’d need to build this thing.  I ask Mike Sheldrake for a simple shopping list.  Glass and resin was going to be the hardest, most challenging.  I dont have a local board supplier who can ship a few bottles of resin over.  Resin will have to come out by vessel, a barge that travels from Hawaii, to Guam, then to here.  A long 2.5 month trip.  I got the materials a week ago.  Im almost finished.  I start glassing today.  I thought to myself would this be interesting for sways?  I figured my audience would grab a beer and enjoy the experiences that I, a new builder- never shaped a single board would go through.

Sheldrake has explained that these kits are very durable, light weight and can be experimented on.  Its a fairly “new” process, but has been done a few times in the past by others.  Sheldrake has a short history on boards built out of cardboard years ago.  But not well documented, and probably failed to catch on due to the lack of technology available at the time.  Today computers are making that a possibility.  I think Mike Sheldrake also has the patience of a saint.  Building the pieces like a puzzle, hand numbering all of them (HUNDREDS) after they get cut out, making videos and how to guides.  He’s got the heart to do it.  I spent less time building up the pieces than it took him cutting them, Im sure.  About 2.5 hours or so to set all the pieces together.  A few minor mistakes along the way, but all in all a simple process, it did require an extra pair of hands.  Thanks to my co-worker Jeff!

To Mr. Sheldrake and all others…I hope I can post more builds from the Islands.  Its extremely difficult to get materials here, which helps me get into a creative mode.  I have a few ideas I will experiment on and eventually surf.  This kit from cardboard makes it possible to ship a board practically anywhere.  A serious plus.  The other easy way is by HWS.  Paul Jensen mailed out a kit and is here, waiting to be built.  Another day…

To put a spin on the build process I will attempt deliver a build that is very transluscent with the use of glass.  So far these boards are frosty, but light travels through them well.  I think my theory will work. We shall see.

Here’s the pics of my build up.  Slowly coming together.   Thanks :wink:

…and if you’re doing a cardboard build, post pics here if you like…

I’m using dial-up. So, these shots will take me some time to post.

Heres the box when it arrived.  Wooow!  lol

Here’s the board Nick in New South Wales built.

These are the stringers, all 10 of them.  Not yet glued.  I used Loktite brand superglue from the store, and some painters tape.  Thats about all the gluing needed for these boards.  

Sheldrake did a great job of numbering the pieces. Once I pulled the cut-outs from the box and glued them, everything else fell into place…well, sort of. 

Nice dining room table build-up @ the Fire Station on Meck Island.

The stringers had key cuts, resembling a skeleton key  down them.  Certain ones had to be lined up with the cross sectioned ribs.  This is how you align everything properly.  Once the grid pattern is layed out you begin to see the Fish come to Shape.

When the cross sectioned ribs were done, this is what I ended up with.  I had to trust the numbers, and go with it.  Even though it looked odd. 

I then had to slide the board (right side, the high side) down to even out the fish tails, or butt cracks.

Now to build up the side rails.  This is the unique part o f this board.  It provides little tiny cardboard fingers that hold the glass to form the rail.  Very delicate process, but over all satisfying.

Nick, This is really cool ! beats the crap out of milling coconut wood !!! you were lucky to get one of Mikes kits. That guys got some smarts to figure that out. Since I first saw these boards I have wanted to do them with balsa wood and wood veneer skins. But right now he has nothing avalible. I know what kind of CNC machine he used and I could aford to buy one but would have no idea how to write a program to do what he did. If we could combine my wood working with his computer and CNC skill we could really make magic !!! Oh well, Someday!!! You will have fun with the Paul Jensen board. Some times I miss Kwaj. Such a strange place !!! Do they still have the windsurfing club ? What kind of planes are they flying up to Meck. They were discussing discontinueing the Carbous. Are they still useing the UH-1 chopper? 

im sure it is light… but how much does that core weigh?  Please post pics of glassing procedures… extremely curious.

The boards holow core is complete.  Here’s a profile shot of the board.  Im holding it up here.  Whats neat, is that this board is very light weight, stirdy, and all the pieces hold quite snug. 

Next I lay down a coat of RR epoxy, no glass.  I delute the resin with Isopropyl rubbing Alcohol so it soaks into the honeycomb support structure. I want the resin the harden the top surface of the honeycomb structure.   A good tool to use here is a sponge brush, or what I ended up using was a faux sheep skin polish pad for shining shoes.  Kiwi Brand, and only cost about $1.50.  The deluted resin worked well, although I poured enough to apply on 3 other boards all together. 

*Notice the dark colored areas on the honeycomb pattern.  Thats where Ive put resin down.  Then notice dry light colored cardboard on the rail pieces.  Those dont have epoxy which I will explain in a later step. 

For even more fun, I went to a local shop on Kwajalein where the store owner, known as the Bali Lady, sells goods from her annual trips to Bali.  I found a shell pendent neckelace that looked like it’d be cool to inlayed on the tail of the board.  20 bucks!  Perfect fit too.

The next step.  MONOKOTE. 

Tools:  Background music, an iron with an old t-shirt covering the iron surface.  Crank the heat up to YOWZA!

Side note:  These shots were taken during an incorrect application of the Monokote.  I did not realize this, but I was supposed to remove the top part of the film.  When peeled off, the protected side is the heat reactive adhesive side.  OOPS!  I thought this was supposed to be easy, instead I kept ironing.  1 hour later i realized this.  Damn!  I peeled up the monokote,did it right.

My hypothosis.  Monokote, normally used in model airplane construction, is fuel proof polyester film that will not yellow or deteriorate in time.  It resists high temperatures over 300deg.   When applied (correctly) it is “as tight as a drum” literally.  I believe that this is what will give the glass coat a backing, thus creating a transparent look.  I was affraid if I ironed the monokote straight onto the cardboard surface without applying deluted epoxy  it would stick on there like scotch tape and cause delamination problems. This method should prevent that.

Just unroll the stuff, drape it over the side.  Cut it to length, and peel off the adhesive backing.  Flip the material onto the deck and iron away!

The side rails are left bare, and going back a step, I did not apply deluted epoxy to the rails becuase I want the resin to stick and suck to the cardboard during the glassing stage. Glassing over the rails directly should make for an interesting transition of clear board to frosted rails.  Should hide my laps as well.  Ive never glassed a board totally by myself and only one time before then.

Well, I took the board home from work that night.  I finished both sides in about an hour.  Its not perfectly clean along the edges but it looks so much better.  You can tell that the reflection of light is even better…  I was tired, and had to spend quality time with the wife.  I watched Distract 9 while entertaining myself with Monokote.  



We take a catamaran up to Meck these days.  The Uh-1 are still operational.  Although slated to be retired next year.  I still want to do a friggin coconut tree board.  I got dibs on that build!!! 

The build process for me right now is difficult becuase I have to move all my tools from place to place by hand.  I dont have a shop, and Im using the safe places at work to hide and build most everything.  Hauling everything on my bike is hard.  I miss having a truck.  Kwaj is an island full of fit and happy people who dont think about fueling up thier cars, ever.  I ride my bike or walk to most places I want to go.

Today I worked on this posting, the weather is crap.  We have Typhoon weather in the Pacific and are creating some big swells, but very choppy and windy.  Its very humid right now and dont want to risk warping my project.  Perhaps tomorrow will be better…Im anxious to get started.

The fins are going to be a test of my abilities.  Im going to us Lokbox fins.  Ive been told to go with 6 deg of angle on the keel fins, to give a loseer feeling.  Is that a good idea?

These are my board dimensions.  The fin placement is going to be hard, but I have to do it.


And I agree, I got very lucky picking up this board.  This board has been a joy!


This is awesome, I want one! cant wait to see glassing pics!

MONOKOTE!  That's probably what the guy uses when he made the honeycomb bamboo boards... what was his name... a very nice looking translucent board, not transparent but overall a very attractive build. 

I wondered how he was able to drape and wet out the glass without it sagging between the ribs.  Now I know - it's MONOKOTE over the ribs.  I'm vaguely familiar with it for model airplane builds.

I do wonder, though, whether the lamination will bond at all to the plastic MKote.  If no bond, no shear strength, and the board is quite likely to buckle in compression, same as many inadequately glassed EPS cores.

Nick, have you thought of this, and how do you anticipate to address it?

Please to continue posting your build, including how well your clothes iron works as a MK iron.  I thought one had to acquire the made-for-the-purpose MK iron, and was bidding on several via fleabay.  Never won, and now I have a couple wings downstairs that lack skins.


Nick, This is really cool ! beats the crap out of milling coconut wood !!! you were lucky to get one of Mikes kits. That guys got some smarts to figure that out. Since I first saw these boards I have wanted to do them with balsa wood and wood veneer skins. But right now he has nothing avalible. I know what kind of CNC machine he used and I could aford to buy one but would have no idea how to write a program to do what he did. If we could combine my wood working with his computer and CNC skill we could really make magic !!!


Yeah, mike sheldrake talked about doing a board originally from Balsa, the cardboard was a prototype.  He liked how strong the cardboard was &  just stuck with it.  I was thinking what you were thinking regarding the balsa build up.  It'd be tough.  There is a required bit of flex in the build and im not sure how the balsa would hold.  But, if it was done it would be one hell of a surfboard!  I tell you what...you buy the CNC router, I'll come over and learn the software.

Honolulu-I wasnt affraid of using a clothing iron for the Monokote.  It gets it right up to heat.  And, the flat surface of the board is much like that of an ironing board.  AIrplane wings are small and have tight access voids where the monokote is hard to apply with a home iron. The shirt over the bottom of the iron allowed me to move the iron friction free, and softented the pressure a bit.

Ive thought about the delam issues, Oh boy have I thought about them… but the glass is going over such a large area supported by the honeycomb that it should hold.  Im 170lbs, and with 3 layers of glass 4,6,4 in S glass it should be strong enough.  I might go over the Monokote with a scoring pad…but not sure yet…I think it will hold.  The rep at Monokote said this stuff will work well with epoxy.  This is my experiment.  Time will tell…


Stay Tuned…

Durbs- Sorry about the delay, I dont know how much the core weighs. I didnt have a scale.  My guess however would be 2.5/3lbs? 

Glassed some this weekend.  Pictures coming soon.  I respect the art so much more now.

“The rep at Monokote said this stuff will work well with epoxy.”

Yabbut normally it would be monokote over epoxy, not the other way around.  Did you ask him about that?