Floats n’ Stuff
Amphibious helicopters can be lots of fun if you do your home work. While installing a set of “bags” is pretty basic, often unexpected problems arise. I shall convey all of the snags that I have encountered along with the appropriate corrective actions. Certain precautions will be noted as to handling during normal operation.
There are different commercial float kits available for the 30 and 60 size helicopter. Not all are good. One particular set would not keep my Shuttle a float since it lacked the proper amount of buoyancy. In the case of the 30, I guess the only thing to be said is let the buyer beware.
A 60 size set caused ground resonance but otherwise was fine. The destructive ground resonance phenomena was cured by making new cross tubes from a stiffer material. The original was manufactured from strips of thick, flexible and heavy aluminum plate. The replacement system was constructed from 6061 T-6 aluminum tubing, being much lighter and stiffer for an additional cost of about ten dollars. The only difficulty here was to find a new method of fixing the bags to the cross tubes and the cross tubes to the side frames. I am a firm believer in keeping the parts count down so I figured that if I was going to make my own attachment method, the landing gear spacers had to go in favour of the proper height cross-tube fixture blocks. This was so that the dimension for adequate tail rotor ground clearance would be maintained. I also now had the option of picking my own landing gear stance or width, which could be made adjustable simply by sliding the bag assemblies in or out on the cross tubes. This was great since no drilling in this particular area is needed due to the clamp up nature.
Although this is not a product review, I have found the Hobbico 60 size floats to have more than enough buoyancy for a slightly more massive gasser. The supplied cross braces are heavy and flexible as mentioned earlier. They should be trashed in favour of a lighter and stiffer attachment method. The instructions are not clear at all on how to install these floats. The small screws that hold the cross tubes to the plywood float inserts are counter sunk at the under side. They are also glued in position and stick up like studs on the top of the float. This is where the cross tubes (braces) are attached. In order to get the proper C of G small holes for these screws may have to be cut in the to the vinyl float pocket where the plywood slides into.
The cross tube fixture blocks can be made by hand using a hack saw, file and drill press.I manufactured mine from plastic so as to enjoy its electrical insulating properties, there by eliminating any chance of the machine becoming a “Glitch Master”. As far as carving the blocks go, take your time and leave enough material to ensure that the plastic doesn’t split. One eighth inch of plastic on either side of the cross tube hole will be fine. You might even find some square plastic stock of the proper dimension. This will mean you can slice it like bread rather than cutting from thick sheet material as I did. When sizing the blocks keep in mind that float gear incidence should be parallel to that of a flat rotor disk (neutral cyclic). You will need longer bolts to attach the blocks to the side frames. These bolts offer a nice clamping action of the cross tubes in the fixture blocks and disallow any shifting of the float gear to the side frames.
In order to have the helicopters C of G centered to the floats center of buoyancy, which is best to do, some measurements must be made prior to bag attachment. Mark the bags left and right and note which end is forward. Double check your measurements and drill the required holes in the wooden mounting plates, tubes or brackets. Don’t be lazy and try to get away with drilling while the bag is attached because you might just have to repair a hole in the float bag .The floats may be fitted to the cross tubes with “DG” clamps or longer screws substituted in the plywood mounting plates. Water proof any wooden parts with fuel proof paint. Route the exhaust outlet away from the float bag to avoid any vinyl melt downs.
The chopper by now is looking pretty fine sitting on your new floats, so up to the bath tub we go (if it fits) for the two big tests, the buoyancy check and secondly the sporting spousal acoustical level check! My favourite, since I may be told to jump in a lake, which is fine by me at this ready to float and fly point in time.
Since the helicopter floats well, lets see how it works on land. Start the rotor up and watch for ground resonance. If you encounter some, try a different air pressure in the bags. Try tightening up the blade bolts if adjusting the air pressure doesn’t work. The machine might shake a bit in the air which is to be expected since the floats may behave like a tuning fork as vibration is amplified. Since the floats have such a large area that is exposed to the rotor down-wash, another input for float vibration can occur.
A person might get the idea that due to the high aerodynamic drag, flying the helicopter could be tricky. Nothing is further from the truth and the machine will respond as before with a reduced forward top speed. If anything, handling becomes more docile. The difference that really matters is on the water. Engine torque will cause the helicopter to rotate when spooling up until the tail rotor arrives at its effective rpm. If you want to start up on the water make sure enough distance is maintained from any obstacles. It can be fun to see how smooth a start up can be made by counting the torsional rotations. When you are ready for take-off under smooth water conditions a certain amount of suction tends to hold the floats to the surface. While the effect is small, it is there. I wouldn’t recommend a water skiers take-off since it is quite possible to nose over into the drink. The same goes for run-on landings! Treat the water like terra firma and make gentle landings. Avoid tail rotor water strikes by not preforming large flaring angles close to the surface. Once on the water you should easily be able to pull several degrees of negative pitch without the floats sinking.
Autos on water have frightened many but other than a slightly different sink rate and rpm it is really no big deal. Some have this idea that if the tail touches the water during an auto the machine will self destruct. Well, I don’t have a driven tail so really other than acting like a water rudder this is not an issue if it accidentally happens. Keep in mind that we are not talking a submarine here! As an accessory you might want to add a small plate to the bottom of the vertical fin. If the machine happens to dip the tail into the drink this anti water strike plate may help.
Using floats on land can cause premature wear especially on rough surfaces or pavement. Grass is about the easiest on the vinyl material. If the mounting system is designed correctly, changing to another landing gear configuration is a cinch.
Having floats on your helicopter opens up a whole new world of flying advantages. One might even hang out at a plank “float fly” or hover above the boat guys rooster tails. You could even convert some of these people to helicopters! Think of all the flying areas that have just become available to you or what a nice short drive you now might have. While this is all well and good we must never over look the safety factor. Consideration to others must be paramount whether they are part of the hobby or not. I really hope people reading this article try using floats on water instead of basically using them just for training gear. It’s a lot of fun…..so go for it!
Just a short note on a different topic. The Internet is getting to be a very big place. Many modelers now have access and are exposed to much commercialized information. While this is great for new products and ordering items there are some grass roots areas that are teeming with uncluttered expertise. One such area is called “Runryder.com”. By enrolling, one has near instant access to hundreds of people operating nearly every type of model helicopter invented. There are many popular individuals who are more than happy to answer questions. Most are motivated only in the satisfaction of helping a fellow human being. It works off of your Internet browser program by sending interesting topics to all members to which anyone can share their opinions. If you have a snag someone will help you fix it.