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SketchUp for RC Aircraft Design Tutorial #7
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Hi guys it’s Mike again. With another hot summer here in Maryland, I decided it was good time try some water flying with my HobbyKing Bixler glider. That’s right, I decided to add floats to my Bixler.
In this article, I walk you through the process of adding floats to your Bixler RC Plane. These floats should work on similar RC powered glider planes like the BlitzRC SkySurfer, Multipex EasyStar, Dynam HawkSky, and AXN Floater.
So here’s what I did. I bought some GWS floats. I could have made my own floats, but found that GWS makes a set that are just the right size for only $15. I’ll walk you through the build process for floats, show you how I attached them to the plane and show you how to add an optional rudder. If you would rather make your own floats, check out this article.
PART 1: FLOAT INSTALLATION
First, let’s put together the GWS floats. They come with written instructions, but there’s nothing like a video to show you how to do it. Here are the components that come in the box. You get:
Here is what they are going to look like when we are done. Note, the optional rudder is installed.
When you are done, you can you just slip the floats up into 2 slits cut in the bottom of the glider.
Step 1. Cut out plastic float bottoms. For each plastic float bottom, carefully cut around this groove around the perimeter.
Step 2. Epoxy float top and bottom together. For each float, test fit the foam top into the float bottom. Right and left floats are identical. Apply a continuous stream of 30-minute epoxy to the perimeter of the foam top. Don’t worry about getting a 100% water-tight seal here, we’ll come back and add another coat of epoxy. Put the float top and bottom together and secure with masking tape about every couple inches around the perimeter. Wipe the excess glue off with a paper towel.
Step 3. Apply second epoxy coat. For each float, remove the tape after the epoxy dries. Apply a second coat of 30-minute epoxy coat around the perimeter. If there is a gap make sure the epoxy gets in there. Wipe excess off with a paper towel and allow it to dry.
Step 4. Apply stickers. The instructions say to apply the included stickers now, but I think you can wait and apply them later if you want. I decided not to use them.
Step 5. Drill holes in wood mounts. Place the wood mounts on the foam float tops. Use a marker to mark the center of where these rounded areas are. Remove the mounts and drill 1.5mm (1/16 in.) holes at these locations
Step 6. Epoxy wood mounts. Epoxy the wood mounts to the float tops, making sure the holes line up with round areas.
Step 7. Install 2 wire cross beams. Install the 2 wire cross beams in the holes between the floats.
Step 8. Install 4 plastic latches. Install a plastic latch at each location where the wire goes into the wood. Make sure the strap is centered on the wooden mount. Mark and pre-drill a 1.6mm (1/16 in.) hole for the 2 screws. Install the screws and repeat for the other 3 straps.
Step 9. Install struts. Install each side of a strut into a strap. They give you some tubing that you can cut and add to the end of the strut, but I don’t think it’s necessary.
Step 10. Install cross bracing wires. GWS doesn’t have this step in their instructions, but I thought it was very helpful for attaching the floats to the Bixler. Put a wire under each strut bend here. Make sure the strut wires are perpendicular with the floats. Notice how the wire is too long. Cut the wire, leaving about 10mm (1/2”) excess on each side. We are going to solder the wire together at these joints. Make a note where the joints are, remove the struts, sand at these joints and solder them together. To help these stick together, make sure use some flux and 60/40 rosin core solder. Also, make sure both wires are good and hot before connecting. Don’t forget to hold these wires perpendicular when making the connection. Later, I wrapped some stranded copper wire around my soldered joint and soldered over them to give extra support. You can put the wires back onto the floats.
Step 11 Mount floats to plane. You need to cut 2 slits in the bottom of the plane to receiver the struts. As a rule of thumb, you want the center of your floats to be slightly in front of the CG of your plane. For me this worked out so the front slit was 60mm in front of the wing leading edge. The rear slit was 183mm back from the front slit. The slits were about 30mm wide. Make sure to measure these for your own plane.
The float construction is complete.
PART 2: RUDDER INSTALLATION
Optionally, you can add one or two water rudders to your floats. I decided to add a 4.5gram servo to the right float, but you could add one to both floats if you want. I found out later that a 9-gram servo offered more control and swapped this one out. Steering without a water rudder may be difficult, especially in the wind. Here is how I added the rudder
Parts needed for rudder:
Step 1. Construct rudder. Cut out a rudder out of a used gift card. You can start kind of large and then cut the size down later. Install a control horn on the gift card. I used one similar to what comes on the Bixler. You could also just cut a piece of gift card into the shape of a control horn and glue that into a slit in the rudder.
Step 2. Hinge rudder. Attach the rudder to the end of the float using a hinge of your choice. I used Beacon Foamtac glue. You could also use strapping tape.
Step 3. Paint components (optional). Options you can paint your rudder, control horns, control rod and servo. White spray paint helps them blend in well with the floats.
Step 4. Install rudder servo. Position the servo on top of the float where you want to use it. Install the servo horn on it. Run the servo wire up one strut and underneath the canopy. Plug a Y servo cable into your rudder channel on the receiver. Connect the air rudder and water rudder servo cables into the Y. Before gluing the servo, turn on your plane and test the servo movement to make sure it’s moving in the correct direction and if necessary flip the servo over. Use some CA (or superglue) to carefully water seal the edges and seems around the servo. Don’t put any near the gears. Make sure the rudder trim is centered on your radio. Cut a control rod and put a Z-bend in each end (or you can just use a HobbyZone HBZ7128 control rod and clevis set and just put a Z bend in one end). Install the control rod between the control horn and the servo horn. Move the servo until it’s positioned so the rudder is exactly centered. Test the servo again, then while the servo is centered, glue the servo down here.
Step 5. Install zip ties. Secure your servo wire to the strut with a zip tie. I also secured the push rod to the rear strut with a zip tie to keep the push rod from bending.
PART 3: CONCLUSION
After doing the installation there were some things that I learned: