Material that floats
 

Hey, In our field there is a big lake in front of us where if a plane crashed it would go into the lake, we have a boat that we use to get the planes back. Sometime's we deadstick and land on the water which sometime's destroys the electronics. Is there something where I can put on the bottom of the fus. if I ever do land or crash on the water for whatever reason it would float instead of soak into the water to keep the electronics dry? (there's a hobby shop inside the lake) We take off on land.

RE: Material that floats
 

Foam floats. As does balsa.

What you really want to do is put your RX and battery inside plastic bags, and seal them in there good. Use a bit of silicon or something to seal where the wires come out of the bag. You can test the bagging job in a sink if you go carefully.

RE: Material that floats
 

just get some big pieces of foam and put it on the fuse and on the wings...

RE: Material that floats
 

Yeah Newb, won't that effect the flying just a bit?

RE: Material that floats
 

I have a nitro truck (savage) and what I do is put my receivers and servos in a balloon and it keeps away from getting wet. would I be able to do that with the plane? I dont see why not?

RE: Material that floats
 

No good, he's in Jersey... The lake water there will eat right through Foam or Plastic :D

(Just kidding - Ex-Jerseyman myself)

RE: Material that floats
 

It would be OK as long as he stays away from Lake Erie. Used to be you could walk on the pollution there.

Forgot to ask, What color balloon did you use? This could be important.[:'(]

RE: Material that floats
 

bruse, I don't think it would effect flying too much, long as he did it evenly... Or you could just stuff the inside fo the fuse with foam...

RE: Material that floats
 

You said "just get some big pieces of foam and put it on the fuse and on the wings.." this would lead to a lot of parasitic drag and probably kill all of the wing's lift. It would also probably make the plane fly like a dog in general. NOTE: No insult intended to any actual dog out there. Fuselages are already fairly well stuffed with things like radios, fuel tanks and pushrods that you wouldn't want to interfere with or do without. Also, aside from building a foam wing, they would be a little tough to "stuff" also. Not a practical solution I'm afraid. He would be much better off just staying out of the water completely or building a float plane

RE: Material that floats
 

a few friends of mine did hit the water and their servo's and receivers started to rust and mess up as soon as we got it back, you gotta quickly dip it in alcahol and let it air dry, that usually works.

RE: Material that floats
 

Well, a float plane won't help when it comes to the crashing part. Landing in the lake isn't the problem, it's the crashing that's the problem.

You could sheet the fuse in foam, and the added drag wouldn't be a huge deal. Most models are drag farms anyway, and our planes are so over-powered that you just wouldn't notice it that much.

Messing with the wing is more of an issue though.

If you are reall concerned, go foamie. Look at how planes like the JKAerotec and TufFlight combat planes are built. They are all foam, and the radio gear can be made totally water proof. I don't think you could sink one of those if you tried. So, look over the building techniques, whip of a foam cutter (not hard to make at all), and start building your own large foamies. Not hard to do at all.

RE: Material that floats
 

Yep, water and electronics/gears don't mix. VERRRRRY quick action by competent tech could have saved the gear. I work on electronic stuff every day cleaning corrosion and other "stuff" from aircraft avionics and re-protecting it. NOTTT an easy task. Our crews pour (accidentally) coffee and cola into them, that's worse than water. [:'(] First step is prevention and then you have to act quickly if it does get contaminated.

Another of my favorite sayings: When they develop a better idiot proof system, someone will develop a better idiot to screw it up.

Just protect your gear as best you can and keep it as dry as you can. if it goes in the water-get it out as quick as you can and dry it quickly. If you feel competent to do so, remove the covers and GENTLY blow compressed air to dry. Be sure to hold the nozzle with your hand to try to reduce the static charge on the air from the nozzle. Use dry Nitrogen if you can find it

RE: Material that floats
 

BTW, if you are going to use the alcohol get denatured alcohol. The rubbing alcohol you get at most drug stores is highly diluted with (you guessed it) water. Denatured alcohol has very little water and you can get it at some better pharmacies and at Home Depot I believe.

RE: Material that floats
 

Is it fresh or salt water? I fly waterplanes annually and DONT protect my gubbins, just check 'em after every flight and if I know somethings got wet then it gets a good blast with a hair-drier and a couple of weeks before I even think of flying it again.
My £0.01

RE: Material that floats
 

Anything can float, even concrete. The college of engineering at my Alma Mater used to build concrete canoes every year and race them. :)

It's Archimedes' principle that's behind floating vs. not. In basic terms, if the weight of the water displaced by the volume of an object is more than the weight of the object, it will float; otherwise it will sink.

You have two issues to deal with if you want to try to sink-proof your plane:
1) waterproof the electronics by either sealing the compartments they are in or sealing the components themselves
2) Make sure that the total sealed volume of the plane displaces enough water for the thing to float. If the fuse and wing fill up with water then they are no longer displacing water. You could put sealed air filled bags inside the wings and fuse so they wouldn't fill with water for example.

Interstingly, you're not the first to have this idea. :) One of the unsuccessful pioneers of powered flight was Samuel Langley. He had the idea to launch his "aerodrome" from a house boat on the Potomac river. Just to be safe, he also added air-filled tanks to provide flotation in case the thing went in the water (which it did).

[link=http://www.flyingmachines.org/lang.html]http://www.flyingmachines.org/lang.html[/link]

Mark

RE: Material that floats
 

eaglelope,
that's only part of the story. Water has a density of ~1 g/ml. Anything with a density less than that will also float--whether or not it displaces it's weight in water. Balsa has a density of much less than one, therefore it will float. However, airplanes aren't entirely balsa, now are they? There's the landing gear, motor, covering, etc. Problem is, if the density of the balsa can't float the ship by itself, then you have to go to the displacement theory. The only way it will float using that principle is if the bird is sank up to the wing--there is probably enough wing surface to float the airplane. by this time, however, the electronics are probably filled with water. I would do what a lot of people have suggested--wrap them in a baggie and seal them up real good. In this case, simple works. It's the KISS principle--keep it simple, stupid! (no offense).

RE: Material that floats
 

hhmm, how about floaters with wheels?

RE: Material that floats
 

if we can have the regular landing wheels and on top of the wheels have a floater ?

RE: Material that floats
 

Correct me if im wrong, but isnt that the same thing? If it has a density of less than 1g/ml, then it will still displace its weight in water, just the lower density means that it will take up less space in the water. In other words a 1 pound block of wood displaces the same amount of water that a one pound block of foam would displace, specicly a volume equivalent to one pound of water. The difference being, the less dense foam will be larger in volume at the same weight, and since they are displacing the same amount of water, will consequently ride higher in the water.

RE: Material that floats
 

Airstrike- how about putting pontoons on top and wheels on the bottom. Then if you are going into the water just roll inverted and land inverted on the floats. Shouldn't be too hard? :D

RE: Material that floats
 

In my note I said, "In basic terms, if the weight of the water displaced by the volume of an object is more than the weight of the object, it will float; otherwise it will sink. "

I think we're saying exactly the same thing. I was just trying to avoid density calculations and keep it in terms that were easy to follow.

Mark

RE: Material that floats
 

no, water displacement is due entirely upon volume. The larger the object is physically, the more water it will displace. Also, volume shaped correctly will help as well. Volume is independent upon mass, and mass is independent of bouyancy. However, density is dependent upon both mass and volume, and is one factor in bouyancy. Just technicalities, and it really doesn't matter. I just brought it up because someone in a post above said that balsa would float, and they are correct.

RE: Material that floats
 

I disagree, an floating object only displaces a volume of water that weighs the same as the object. If volume was what mattered then boats wouldnt sink lower when they are weighed heavier becuase they would still have the same volume. However when you load an object into a boat, the boat will sink more and displace an amount of watere whose wieght is equivilent to the added wieght of the boat. To carry the idea further a 1 cubic foot chunk of wood will displace more water than a 1 cubic foot chunk of foam. Volume only becomes important whan an object sinks completely. But anyways im just being pedantic now. Like you said, either way Balsa will float.

RE: Material that floats
 

well, again, the boat displaces more water when more people get in, because it sinks further. Anytime mass changes and volume does not, then you have changed density. That is what I'm talking about. The density of the boat/cargo/people system is dependent upon all of the factors adding mass--not just the boat itself. If you get too much weight in the boat, then it will eventually sink all the way. The boat's bottom is shaped to make sure it displaces more water the deeper it goes--which is what i said previously (shape matters). The farther the boat bottom sinks, the more volume is exposed to the water surface for bouyancy. Again, the displacement potential is due entirely to the shape/volume of the object. The farther the object sinks, the more water is displaced. Turn that same boat on it's side and load it with the same amount of weight, and it will sink to the bottom--because there is not enough surface exposed to displace enough water.

BTW, a 1 cubic foot chunk of wood will displace more water than the foam because it sinks further into the water--again, because of mass, which is due to density, not just volume. If you push the foam down into the water as far as the wood sinks, then they will both displace the exact same amount of water. Again, the wood sinks further because it weighs more--which is what you are saying. What I'm saying is that it weighs more because of it's density--which is one controlling factor in bouyancy. Archimedes described density because he was given a job by the king to make sure his crown was solid gold. He said that different materials would displace different amounts of water, if they all had the exact same mass.

However, the density factor can be overcame by adding more volume to the interface between the object and the liquid it is floating in.

RE: Material that floats
 

I never thought I'd be having a discussion abouth the density of airplanes... Most discussions I have about density are with my wife about my brain. :)

Density = mass / volume. The shape of the volume has no effect at all on buoyancy (unless you get into surface tension but we're not). However, you can take materials with the same amount of surface area and change the volume (take a box and flatten it, the volume went to nearly zero but the surface area stayed the same). The shape does matter if you care about stability (like keeping a boat right side up) but the objective here is just simple flotation for recovery purposes.

If you suspend an object of a given density in a liquid (or gas) of greater density, it will float. If they are the same density, the object will be neutrally bouyant, neither floating/rising nor sinking. If the density of the object is greater than the density of the liquid or gas then it will sink. It's that simple. That goes back exactly to what you said about the desnity of balsa being less than that of water; therefore it floats. I think we agree there.

Where it get's complicated is figuring the volume of complex objects, like an airplane. For starters, it's a combination of complex shapes. To make it more fun, those shapes aren't generally watertight so the volume of a fuselage effectively looks like the volume of the sides, formers, stringers, etc. and not the entire outer volume. If you can seal the fuselage or fill the non-watertight spaces with watertight volumes (like plastic, air-filled bags) then you can keep the volume larger.

Even so, calculating the volume is tricky so one method is to just measure it. Take an object and completely immerse it in a container that is full to the top with liquid. Measure the volume of the liquid that overflows (is displaced) and you have the volume of the object you immersed. If it's a plane then you have the volume of everything, engine, radio, servos and all. Archimedes figured that out in bathtub while trying to measure the volume of a king's crown. He got so excited he went running around naked yelling eureka!

Back to the story. Now, weigh the water. If the weight of the object is less than that of the water, it floats. Why?

Density of object = mass of object / volume of object
Density of water = mass of water / volume of water

We just said that in this simple case the volume of water and volume of the object are the same because we measured displaced volume.
So, Density of object / Density of Water = mass of object / mass of water. If the volumes are the same, then the densities are directly proportional to the weight.

Like kluivertfan2 said though, when you put a floatable object in a liquid it will only displace enough water to support the weight of the object. For recovery purposes, just floating seems like a good starting point.

So, are you going to dunk your plane to figure out it's volume? Let me know how that goes. ;) Instead, I'd figure the weight of the plane and then determine what volume of water that corresponds to. Like 2slow2matter said, the density of water is 1g/ml (a gram is actually defined as the weight of 1ml of water at 4C) so if you know the weight in grams, the minimum volume needed is the same number in milliliters. Then I'd figure out a way to stuff enough sealed volume (bags again) inside the plane to make up that amount of volume. If you can seal enough volume inside the plane it will float (assuming it doesn't come apart on "landing").

Disclaimer: A physics purist will point out that mass and weight are not the same thing. Weight is the force subjected on an object of a given mass by an acceleration (like gravity). All experiments noted will take place in constant gravity on the surface of the earth so we'll say that mass and weight are directly proportional and treat them equally for now.

In a desperate effort to have this note apply to flight :), I'll point out that it is the same exact principle that makes a blimp float. The density of a blimp has to be less than the density of air in order for it to float. That's why light gases like Hydrogen or Helium are used, they are much less dense than air.

I will never float as I am more dense than any object on the planet. Just ask my wife.


Mark