Use simple scrap supplies to make these cardboard secret message sailboats! A visual language exercise and upcycled summer craft for kids. | via barley & birch
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All, Make

Make: Secret Message Cardboard Sailboats

Ahoy loveys! It may be dipping into negative degrees outside, but indoors we’re celebrating picture-perfect regatta weather. Yes, this Valentine’s Day we have blue skies, a fair wind, and following seas for the 1st Annual Cupid’s Cup.

Use simple scrap supplies to make these cardboard secret message sailboats! A visual language exercise and upcycled summer craft for kids. | via barley & birch
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Super-sleuth sailors may notice our flags are flying a secret message for the day…care to guess what we’ve spelled out in nautical code?

Use simple scrap supplies to make these cardboard secret message sailboats! A visual language exercise and upcycled summer craft for kids. | via barley & birch
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Inspired by our own secret message morse code valentines, we thought it would be fun to use the nautical flag alphabet and turn our secret code into a high-seas STEAM-learning adventure. You can make these to use for play, decoration or as small tokens to gift to friends – OR – turn them into actual sailing boats. Read on for the details!


Is your kiddo stoked about secret codes? You may want to try this unique character alphabet activity or sharing their message with chalk spray paint next.

To make your own secret message cardboard sailboats you’ll need:

Note: We prefer to shop locally or use what we have at home, but this list contains a few Amazon affiliate links for reference. As Amazon Associates we make a small commission on qualifying purchases.*

BASIC SUPPLIES:

  • Scrap cardboard
  • Scissors
  • Paint and a foam brush
  • Paper
  • Twine, string, or ribbon
  • Scrap fabric, newspaper or similar for sails
  • A craft stick, basswood dowel (like these) or a twig for the mast
  • A glue stick and hot glue gun (I like using this low-temp kind with kids)

OPTIONAL SUPPLIES:

Secret Message Valentine Art Instructions:

  1. Print Morse code and nautical flag alphabet references

    You can download and print our handy secret message printable pack or just google reference pages to use for coding your own secret messages.

    Secret Message Alphabet Sets Printable Preview
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  2. Cut a simple boat shape out of cardboard

    Cut a simple boat shape out of scrap cardboard.

    Cut a simple boat shape out of scrap cardboard.
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  3. Paint your cardboard boat

    Paint the top of your boat using tempera or acrylic paint and a foam brush.

    Paint the top of your boat using tempera or acrylic paint and a foam brush.
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    Tip: If you’re making boats you plan on setting sail in real water, you can either use a water-safe paint (I get samples of exterior house paint from the hardware store) or seal your painted cardboard boat with a coat of Outdoor Mod Podge or similar.

  4. Cut our your nautical flag letters and arrange

    Before you start putting your string of flags together, cut out the flag letters you’ll need from our nautical flag alphabet set and arrange them in order. For our sailboats, we wrote out “I LOVE YOU” in nautical flags.

    Cut our your nautical flag letters and layout your message.
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    Note: When you cut out your letters, be sure to leave a white tab at the top as we did. This will allow you to fold the tab around your flag line and glue.

  5. Create your nautical flag message banner

    Cut a long length of twine (longer than you’ll need – this gives you some extra twine to hold on to when you glue).

    Create your nautical flag message banner.
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    Fold the tab of each nautical flag around the twine and glue it on with a glue stick.

  6. Add your mast

    Using a glue gun add a mast to the middle of your boat. I had some small basswood dowels I used for ours, but you could use craft sticks, thick cardboard, or a twig instead.

    Using a hot glue gun, add a mast to the middle of your boat.
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    Before hot gluing in our masts, we made a small hole in the top of the cardboard we could push them in. This isn’t necessary but is an added layer of stability for the mast.

  7. Hot glue a sail and your nautical flag banner to the mast

    Cut a simple sail from scrap fabric, cardstock, newspaper, or whatever you have! Hot glue it to the mast, then add your nautical banner. Once the hot glue has completely dried, trim the excess twine from the banner string – your sailboat is complete!

    Hot glue a sail and your nautical flag banner to the mast.
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  8. Gifting these? Print out or draw you own decoder sheet

    Once you’ve finished your boat, print out or draw a decoder sheet to fold up and send along with it to help the recipient crack the code!

You can make this into an honest-to-goodness seaworthy craft (well…backyard sea-worthy) by hot-gluing a few wine corks or a piece of old styrofoam to the bottom. You’ll want to make sure you have them equally and evenly spaced (2 wine corks at the front and two at the back for example) to keep your boat from tipping.

Use simple scrap supplies to make these cardboard secret message sailboats! A visual language exercise and upcycled summer craft for kids. | via barley & birch
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More ways to have fun with nautical flags

Use simple scrap supplies to make these cardboard secret message sailboats! A visual language exercise and upcycled summer craft for kids. | via barley & birch
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If you’re eyeing our “sails” and wondering where I found the hip fabric patterns, I have to admit, they were gifted! I received the amaaaaazing fabric scraps I used for this project from Bergen of Lilla Barn Clothing. She very generously sent her leftovers my way and if you’re a fan of modern patterns, you MUST visit her shop full of cute clothing and handmade gifts for kids and adults. Not sponsored – I just swoon over her selection every time a new season rolls around!

One more tip…finding that you need to stiffen your sail? I have found that using a foam brush to paint on a thin layer of Elmer’s glue, then hanging to dry works just as well as using an old fashioned fabric stiffener.

For more handmade valentine projects, try making your own mixed media heart bouquet cards, or send your message of love via (paper!) messenger pigeon.

For sugar-free entertainment, try these poseable conversation hearts, create wearable art with our heart pennant pin DIY, or build a STEAM-powered cardboard love shack.


*A note about Amazon affiliate links: We strive to use simple, earth-friendly supplies that can be purchased locally whenever we can, but sometimes we find the best universally available options, a rare eco-friendly find, or a niche product only available on Amazon. When included in our supply list, these products are affiliate links, and if you click-through to make a purchase, we receive a small commission that helps us re-order these supplies!

Use simple scrap supplies to make these cardboard secret message sailboats! A visual language exercise and upcycled summer craft for kids. | via barley & birch
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About Amanda Eldridge

With a passion for cultivating imagination, Amanda aims to help families discover their creative potential and be inspired to make the world a better place through art, play, adventure, activism, conservancy, and community. When not playing with ideas, designs, and projects for barley & birch, Amanda enjoys working as a freelance graphic designer and modern art curator.

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