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How To Build The Best Balloon-Powered Sponge Boat!

Let’s set sail for a STEAM Summer starting with a Balloon Powered Sponge Boat! Most of our kiddos’ activities are completely canceled or at least significantly altered. But, that does not mean we can not have a great summer.

This sponge boat is the first post for a summer of fun STEAM-themed summer activities.

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Balloon Powered Sponge Boat


1. First, measure the short side of the sponge and mark the center.

Balloon Powered Sponge Boat

2. On the same end of the sponge, measure down the long sides the same distance as it was to the center in #1. Mark it on each side. Connect the side mark to the center mark, on each side, to create 45-degree angles for the bow of the boat.

3. Cut along those lines to make the pointed bow. Discard the pieces.

Balloon Powered Sponge Boat

4. Next, from the bow point, find the center of your sponge by measuring halfway down the length of the boat.  Mark just behind that. 

5. Adults, use the scissors to make a vertical slit/ hole.  This will be pretty easy in a dry sponge.

6. Put the end of the balloon through the hole.

Tips: Before you position the balloon stretch it and inflate it to make it easier to blow up once assembled.

Also, I used the tip of a dull pencil to make the hole a little bigger. Then “catch” the rolled “lip” of the balloon to squeeze it through the hole. The tighter you can keep the hole the more secure everything will stay together.

Balloon Powered Sponge Boat

7. Trim the straw.  

I took off about 4 inches.  You want to leave enough that you can wrap a rubber band around once it is assembled.

Balloon Powered Sponge Boat

8. Insert the straw into the balloon.

If it is a bit tight fold over the end of the straw on itself to make a bit of a point.

Balloon Powered Sponge Boat
Balloon Powered Sponge Boat

9. Use the rubber band to secure the balloon to the straw.

10. Finally, inflate the balloon through the straw and angle the straw toward the back of the boat before you put it in water.

11. Pinch the straw until you are ready, then…

12. Set sail!

13. Wring out the sponge and repeat!

Switch out the balloon for the smaller and see what happens.

Bon Voyage!

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