These floats intended for parkflyer type models are constructed from a single sheet single sheet of 20” x 30” Sturdyboard that you can buy at Walmart for $1.97. The only tools you will need are a straight edge and a X-Acto knife. Using the foam core of the Sturdyboard and full size patterns you cut out interlocking pieces that you glue together to form lightweight floats.


Sturdyboard- is a display board that has a 3/16” foam core (Depron) covered with poster board type material. The covering comes off cleanly by soaking it in water but it does take a little effort. It’s sort of like taking off multiple layers of wallpaper. As with wall paper it best to soak it's and let the water do the work.

Patterns
The pattern for 24” floats that were designed for my Slow Stick is located here. These are the same size and shape as those I have cut from solid foam. Normally I wouldn’t post anything I haven’t actually flown but the pattern for a 17” version that I believe will work for a Tiger Moth size plane is here. Both are in PDF format with overlapping pages so you can print them on 8.5” x 11’ paper. Carefully align the pages together using the alignment marks and tape them together.

To attach the patterns for cutting lightly spray the back of the pattern with a spray adhesive. I used Duro all-purpose spray adhesive but other spray adhesives should also work. Let the adhesive dry for a minute or so and then smooth the plans on to the Sturdyboard foam. The adhesive will hold the pattern on for cutting but will come off cleanly and easily after cutting. Use a straight edge and X-Acto knife for cutting. You will find that the foam is very easy to cut. For a straight edge I use a steel ruler(a Dollar Store buy) with a cork backing that prevents the ruler from slipping.

Glues
There are all sorts of glues that you can use for assembling these floats. You can search the Foamies group for the merits of each type. Among them are epoxy, polyurethane, hot glue, perfect glue #1, foam safe CA, Titebond II, and Weldbond. Because exposure time is brief glue rated as weather resistant should be sufficient. For laminating parts I used either epoxy or foam safe CA. For quick gluing I used the foam safe CA and for wood parts I used epoxy. For most the joints I used Weldbond which dries clear and flexible. It is also inexpensive and widely available. I avoid the harder glues as much as possible as it is difficult to sand the hard glue with the very soft foam.

Assembly
After cutting out the parts check to see that the bulkheads line up squarely with the sides. You may have to trim the tabs slightly to make sure this happens. First glue the ½” wide F1 parts centered on both ends of the top. Before gluing the front one you will need to bevel it to roughly match the side. You’ll find the foam is very easy to sand.


Also glue the B4 and B3 parts together. The B4 part supports the bottom behind the step.

Working on a flat surface protected with wax paper, glue the bulkheads in place. Once dry, glue on the sides. Use pins to keep B3 aligned with the step and anywhere else needed to keep the side in position. Make sure to use weights to keep the top flat against the surface. This will assure a straight float. Glue in the two F2 parts to strengthen the rear of the floats. Make sure they are in contact with the B5 part.


Once every thing is dry check to see that the bottom pieces fit nice and flat and sand out any misfits. To glue the rear section on just use some weights to hold it in place while drying. For the front section use weights and pins to hold the curved section. To reduce the chance of cracking you can pre-bend the front of the bottom by sticking it hot water and then bending it around something about the size of a small coffee can.


After drying trim and sand the bottom the top to be square with the sides. Try to avoid sanding off the surface of the sides. Now epoxy on the 1/32” ply to the back of the step. This protects the step as well as strengthening this critical joint. It’s a good idea to smear a thin layer of epoxy over the ply to protect it from water. Examine the seams and tabs and seal any holes with glue to make sure that the floats are watertight.

From this point on finishing these floats is the same as it would be if you had cut from solid foam or bought the cores already cut.

Covering
The first thing is to cover the bottom of the floats. This protects them from dings and adds considerable strength. The easiest thing to do is cover them with packaging tape. To add color you could also use the colored covering tape they sell for covering foam wings. Because the tape is not wide enough I use two pieces overlapping in the center. I also overlapped the edges to come up the sides about ¼” to protect the edge and further seal the bottom joint. To make the tape adhere better you can give the floats a light coating of spray adhesive. (Test your spray adhesive on the foam before doing this) If you find the tape lifting where it overlaps on the side I find smearing it with epoxy will hold it down.

Mounting plates
The next thing to do is to glue on mounting plates made with 1/32” ply. This ply comes in 6” x 12” pieces that you can find at your LHS, craft stores like Michaels and at some home supply places. I made mine the width of the floats and 1 ½”long. They are positioned so that when you mount the floats to your plane the step will be at or a little behind the CG. I glued these on using epoxy.

Cross Braces
Next you want to glue on cross braces to keep the floats aligned and flat. On most of mine I used ¼” x 3/32” basswood. Other choices might be spruce, bamboo skewers or 1/8” carbon rods. I even used bamboo salvaged from an old rake. On my recent set of floats I added a bamboo skewer under the basswood to stiffen them. I glue the braces to the front of the front plate and the back of the back plate.

Mounting System
Finally you have to decide on a mounting system. The simplest, lightest, cheapest and my favorite is to use ½” x ¾” tabs made from 1/16” to 1/8” ply. Cut a slot in the center of the mounting plate (before gluing them to the floats) and push the tabs through the slot about 1/8” and glue in place. An advantage of the tabs is that they accommodate short axles and a less than perfect bending job of the landing gear. You also can drill a vertical line of a few holes so you can experiment and easily change the angle of floats relative to the wing. Make sure to use a wheel collar on the inside as well as the outside as a hard landing may flex the landing gear and push it through the mount.

For a fancier mounting system you can use landing gear straps as shown below.


Finally protect any wood parts from water with a clear coating.

For those of you living where there is snow on the ground now is a perfect to start float flying. Floats work great on snow so you can get a feel for flying with floats before committing your plane to water.

Article and photos by 'jimsp' of Sayre PA

RC Groups Thread:     http://www.rcgroups.com/forums/showthread.php?s=&threadid=195067

To make it easy Jim added a ZIP file of the TIFF files for the 24” floats. You can find it here.