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Feb 01, 2004, 02:26 PM
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jimsp's Avatar
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Build Log

$1.97 Floats

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.

The pattern for 24” floats that were designed for my Slow Stick is attached. 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 also attached. 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.

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.

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.

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.
Last edited by jimsp; Jul 30, 2009 at 03:42 PM. Reason: fixed links
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Feb 06, 2004, 04:02 PM
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FlattyFlier's Avatar
How long do you have to soak the board?
Feb 07, 2004, 09:46 AM
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jimsp's Avatar
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Originally posted by Mchone, Jake
How long do you have to soak the board?
Prolonged soaking the board just makes it easier to remove the paper. When I’m in a hurry I try to peel off the shiny top layer and then using the sprayer on the kitchen sink I repeatedly spray with hot water and peel off the paper. For the last layer of paper I find gently rubbing with a sponge works well. I don’t try to get every last bit of paper off. I just wait to the parts are cut out and remove any residue left behind. It probably only takes about a half-hour to clean up a board.

To make things easier you can peal the top layer off and then soak it in the bathtub for an hour or more. Some people leave it in overnight but that seems somewhat extreme. In any event you will find that the paper comes off cleanly leaving a very smooth surfaced (and cheap) sheet of foam.
Feb 07, 2004, 10:09 AM
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FlattyFlier's Avatar
Thanks, Jim
Feb 07, 2004, 04:47 PM
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Thank you for your plans here. Made up a set of floats, attatched them to my slowstick and couldn't believe the fun on snow! They even make the stick more stable in the air. Sometimes I think the planes are getting too light making them somewhat of a handfull even in light breezes. Looking forward to some sunny calm days. This has made my winter!
Feb 07, 2004, 05:45 PM
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FlattyFlier's Avatar
Good to here the flight report, Rick! I had the same experiance with my SS!
Its more fun to taxi around on snow, than to fly it!
It flies better, if you ask me, with floats on it, even if loops have to be
You might want to put a keel on them. I found with a simple balsa keel, the floats trak straiter(on water and snow) than the wheels did!
Hope you have fun!
Feb 09, 2004, 01:35 AM
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Kevin Murray's Avatar
Jim thanks for linking me to this page and for the float plans you provide here.
Feb 27, 2004, 05:24 PM
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Titch's Avatar
could someone who can open the pdf file please give me the dimensions of the floats all over... for some reason i cant figure out whenever i click on a link to a pdf file my system get cought in some kind of loop, seems like its trying to download and open over and over and over... will keep going till i force it all to close... anyway... now that i have rambled.... is there anyone who could maybe convert the file to a non pdf format... or somethiing along those lines... i really wanna build these floats for my SS and i even cleaned up my foamboard already... thanks in advance to any help [email protected]
Feb 27, 2004, 05:42 PM
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jimsp's Avatar
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Make sure you have the latest version of Adobe Reader, which I believe is 6. The PDF format is nice because it prints out the long pieces on overlapping pages with alignment marks. If this still doesn’t work for you I have the TIFF files from which I made the PDF file and the VISIO 5 files which I used to create the drawing. Let me know and I can Email them to you.
Feb 27, 2004, 05:54 PM
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Fredrik W's Avatar
I have the same problem with my computer at the office.

I have to right-click on the link and choose "Save as..." from the drop-down menu to save it to my harddrive, then I can open it.

// Fredrik Wergeland
The Great Electric Motor Test
Feb 27, 2004, 06:06 PM
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Titch's Avatar
I already tried that and it still does the same thing... im at a loss on how to fix that... but ...on the other hand... iv had this OS running for about a year now... could be time to format sys... maybe upgrade. hmmm thanks anyway.... Paul
Feb 27, 2004, 08:49 PM
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jimsp's Avatar
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I tested it again with Adobe Reader 6 and it will open the file by either saving it and then opening it or will open it directly from the browser. You will need to install this option but the first time you run Adobe Reader 6 it should ask if you want to install the capibilty to open the PDF files directly from the browser. Again if you continue to have problems I can E-mail you the TIFF files.
Feb 27, 2004, 09:23 PM
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jimsp's Avatar
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To make it easy I added a ZIP file of the TIFF files for the 24” floats. You can find it here.
Mar 05, 2004, 04:22 AM
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Dick Adams's Avatar
Jim these look interesting!

I have a 35" WS Speed 400 Tiger Moth that weighs 21 oz's ready for flight without floats.

Tried a set of balsa sheeted foam floats 21" in length last fall, but too much weight.

Two questions:

1. Do you think your floats would support my bird?

2. What do your floats weigh??

Thanks, Dick
Last edited by Dick Adams; May 20, 2004 at 05:38 AM.
Mar 05, 2004, 07:36 AM
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jimsp's Avatar
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The 24” floats ready to fly with the cross braces strengthened with bamboo skewers and using the slightly heavier landing gear straps for mounting weigh 3.1oz. Also I used packaging tape which I think is a little heavier than the colored wing covering tape. I have had some floats of this size weighing closer to 2 oz. From you photo because of the way you are mounting the floats you might not need the cross braces although in general I think they are a good idea because they keep the floats aligned and level.

I think these would be big enough for your Tiger Moth. I found that the key thing for getting the floats to come up on step and quickly move across the water is the width of the float. For example when I was experimenting with my Slow Stick I found that going from a 2” wide float to a 2.25” wide float made a big difference. Give the floats a try and see how they work. If you are still having problems you can make them 3/16” wider by simply adding a ½”- ¾” wide strip to the outside of the float from the step forward. Make sure it overlaps the bottom a little so you can sand it flat with the bottom.

One additional thought. I would not bother with the water rudder. In calm conditions or with little wind you really don’t need the water rudder. As the wind picks up you do need the rudder but if you try to taxi cross wind you are likely to tip over(the most common cause of dunking while float flying). It’s better to let the plane weather vane into the wind, float backwards a little and then take off.
Last edited by jimsp; Mar 05, 2004 at 08:02 AM.

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