RCCanada - Canada Radio Controlled Hobby Forum

Hey way to go with trying to finding something better than the old dubro and bent music wire float setup. That way works and one can be successful doing it but change over is often difficult and all too often I see people dealing with issues both on the water and in the air from not so perfect setup.

The few airplanes I have done with metal supermarket aluminum have been better... IMHO The struts look more scale and changing from floats to wheels and back again is also quick and easy.

My first attempt at floats was with my Yellow telemaster. This attempt failed as both struts were identical. That put the angle between the wing and floats at around 12 degrees... FAIL!!

I then read Chuck Cunningham on floats following his advice and complimented his method using 3/32 6061 (bar stock or sheet as required) to build up struts. Using a metal blade on a band saw allows you to cut the metal and if you are doing rounded cuts a high quality scroll saw blade will work if you use lots of oil and take your time.

So here is my procedure more or less

1. On your plans extend the line of the flat bottom wing forward to the prop. For a semi or symetrical wing eyeball it you won't be far off.
2. From this line draw a 90 degree vertical line at both the recommended aircraft cg and at the prop line all the way down.
3. Mark the vertical prop line 2" below the largest prop you will use. (I've tried bigger and smaller props and coarser and finer pitch props just stick with the basic 10-6 for and old 40 or an 11-6 for a new 40 or 46 engine it won't matter.) Add Paper to your plans it it helps.
4. Measure that first mark and make the same mark on the vertical CofG line.
5. Connecting these two marks parallels the wing and will not work. Even on the step you will not have enough +'ve angle of attack to get airborne, the tails of the floats will drag as you try to horse the plane off the water. You need a couple of degrees difference between the tops of the floats and the bottom of the wing. So using SOHCAHTOA figure out how far UP from the CofG mark to get a 2-3 degree line between the TOPS of the floats and the BOTTOM of the wing and you will be about right. (keep two inches between the bottom of the prop and the top of the floats)
6. Once you have drawn this line then draw in where the mounting screws will be on the floats and the aircraft. Check out the yellow telemaster... the mounting points required large angles and lots of cutting but once I had my angles figured and struts cut properly it was a rockin' little float plane. The mount points just need to be convenient!! The float step should be about 3/4" behind the recommended C of G line.. Some say less but float planes tend to fly better a bit tail heavy so mine probably winds up closer than 3/4" in reality.
7. Draw in your float struts (be creative!!) they DO NOT have to be symmetrical nor do they have to be large. Once the Spreader bars are attached the structural arrangement is incredibly strong and practically unbreakable. I have pounded airplanes hard into rough water at extreme angles and only once have I bent the float struts. Check the Miniplane pictures, the lower strut is 3/4" wide upper strut is 1" wide and I could have even shaved a bit off that... Check the LT40 1/8" stock at 1.25" wide this was over kill but it was what I had on hand and it worked... just a bunch heavy.
8. Once your creative juices have flowed and you like the side profile draw a head on view. This will help you get the width and diagonal distances correct. I use large graph paper for this. The float width is usually around 25% on center of the wing but make sure you like the way it looks. Miniplane is a smidge wider than 25. LT-40 and Eagle 2 are a smidge narrower. Telemaster was right on 25%. Just prop everything up as best as you can with some books and stare at it a while... make small changes... you will know when the width looks right.
9. Now for the plat de résistance.... draw on graph paper the cutting profile for your aluminum stock. Consider all of your proper distances. Note that all the mounting holes will be properly in scale fore and aft but because of the diagonal, the width will be more than a scale top view if you catch my meaning.
10. Transfer this drawing onto your metal (any 6061 3/32 stock will work, sheet is good as well as the bar stock)
11. Here is a sweet trick... Make sure you have a good METAL blade on your band saw...Please of course all blades are made of metal.... TPI should be 18ish to cut metal the 6 TPI blades for wood are just a mess and really noisy and will break... ask me how I know....
12. Sorry back to the sweet trick... Using double sided tape, tape a length of straight hard wood stock about 1/2 thick onto the lines of your aluminum stock one line at a time and use it as a cutting guide.. works like magic and then use some cheap sand paper to knock of the cutting lines while clamped in a vice. It takes a while but when you are done you'll have a rocking float strut cutout.
13. Drill out all of your mounting holes and then bend in a vice.

Additional advice.

Usually I make a fore and aft float strut but have found that no matter how accurate your measurements and bending you wind up reaming out mounting holes to make the plane sit straight and the left and right floats sit even. This last plane I'm working on (eagle 2) Metal Supermarket didn't have sheet stock long enough for me so i took four short pieces. I then split the fore and aft into separate left and right sections. This made it very easy to make them identical and the mounting holes spot on. Two mounting holes on the fuse three on the floats, two on the floats would work as well. (Just cut one on top of the other). Once everything is bent set up your Mark 1 homemade jigs and start sticking everything together. Once you figure out that your homemade jig is ---- and no matter how many laser levels and strings you have swinging around it ain't going to work and you throw it in the can, look for the nearest linoleum floor with a grid type appearance. Find the biggest area and double side tape the floats down with the rear propped up even and the tops level ... lining everything up with your mark 1 eyeball to the linoleum grid prop up the plane on the struts that are double side taped down and then once it looks right mark the holes... drill them out... tap them or use t-nuts, both are equally effective. Where the split struts come together you may find that the left and right side do not come together evenly. As you slowly drill and tap your floats first then your fuse second, the struts may need a tweak in the bend here and there. Once they are close (within about an 1/8th") just drill and tap then round off the struts creatively so that it isn't as noticeable :)... just make sure the floats are parallel and aligned and the plane is straight and level and everything LOOKS right!! For both float and aircraft mounting locations I use 3/8 bass wood. Tee nuts work and tapping the wood and painting thin ca over the wood threads works great as well. Although tee nuts would be quicker to change out if need be I like the drill and tap method with 1/4 - 20 nylon machine screws just because i think it looks cooler.... today anyway.

In regards to spreader bars lately i'm using 9/32 CF arrow shafts that slide into a brass tube mounted in the floats. The end of the shaft is plugged with dowel drilled to fit a 4-40 threaded plug which is carefully glued in. The float mount is a bit tough in that you have to make sure the brass rod is level otherwise it's a pain to correct after the float is finished... ask me how I know... The brass mounting tube is set into bass wood or whatever hardish wood you have lying around. The outboard end is capped with a washer that the CF rod will butt up against when you tighten down the 4-40 machine screws. It is easy to toe your floats in or out a few degrees using this method but I have not seen any advantage doing either (I experimented a bit) just keep the floats parallel. I have also used the 5/8 airfoil shaped aluminum stock successfully and it looks very scale and cool but it's a lot more work in the lining up and creating mounting points area.

You can also consider insetting your float struts into your fuse for a more scale appearance as well as flush mount the float attach points but of course these would need to be designed into the initial building phase of the plane and floats. Easy to do but a bit of planning is required, also do not over build anything!!! It is amazing the strength of wood and metal and the structural setup of the floats is near bullet proof... You are building the plane to fly not to crash so any extra weight in wood or metal to "Strengthen" the frame is likened to building the proverbial brick outhouse...

BALANCING!!! I've had good luck with most of my planes in the balance department. On floats your plane will fly better with the C of G a bit further aft than normal but PLEASE PLEASE PLEASE be careful as I'm talking only fractions of an inch... Going from flying better to holy crap this thing is going crazy happens in about an 1/8th (again... ask me how I know...) of an inch and floats certainly don't enhance the control of any airplane much less when it is tail heavy. Once you have found a good and safe balance point mount your weights, if required, in the floats that way it is wicked easy to switch between floats and wheels.

All my finished floatplanes have flown off grass, snow and water. The Miniplane floats are Greatplanes 20 size built-up floats covered in light fiberglass with Zpoxy and Canadian tire Armour Coat ENAMEL. The red floats... Yep floated three planes and still going.... are solid foam cores picked up from a swap meet covered in balsa and ply and fiber, ZPoxy and CT Enamel. (telemaster had an incident on skis.. the LT-40 is still going... Eagle to be continued (:

If you want to see any more pics or want some simple drawings on how i built up the floats or fuse of these airplanes let me know I have a bunch. My float knowledge is still a work in progress but lately I have been more successful than not... :)