RE: Material that floats
 

Roger that

RE: Material that floats
 

i also have a nitro truck, tmaxx, and i used something called rubberize-it, plasti-dip or something like that, you can buy it at almost any hardware store, home depot, menards, and so on. you take your servos and reciver and dip them in it and it makes a coat around them so nothing can get through, works great

RE: Material that floats
 

lightly brush the bottom of the fuse with thinned epoxy and wrap the electronics in plastic using the water connectors from tower for the servos. though i would think that deadsticking on a lake with landing gear attatched to the bottom would do bad things for the fuse...

RE: Material that floats
 

thanks guys for the input and a 3 credit course no make that 4 credit course on why things float haha. I will give a few things a try such as plastic wrapping electronics, and the rubberize-it formula. Thanks!

RE: Material that floats
 

Either way, the box still floats, right? That's because the material it's made of has a density less than 1.
Now, as you said, if the box fills up with water, then it will sink--just as your airplane will if it fills up with water.
Displacement method is the best way to attain volume for irregularly shaped objects, but I (as you pointed out) will not be dipping my planes in water to find out how much volume they take up.

BTW, H2 is lighter than air, but not a good idea to use in a blimp--just ask those on the Hindenburgh. Helium, an inert gas, is a much better alternative. (That statement was just for kicks and grins).

I agree with everything you've said, except that shape doesn't matter. If a boat had square sides, instead of slanted sides (or a V bottom), then it would in no way be able to hold as much weight. Obvously that has a lot to do with stability, but it also allows the boat to displace more and more water as it sinks further and further under the surface due to weight loading--because (as you hinted to) there is more boat at the interface of the water.

I think we are trying to say a lot of the same things, just going about it in a different way. I love discussions like this. In the grand scheme of things, it really matters zero--I don't think any of us will intentionally land our models in water without floats or other provisions.

RE: Material that floats
 

2slow2matter-
If you take a look at various barges (both river and ocean going) you would find that they are flatbottomed. This is because this allows for the greatest load carrying per sq ft of deck area. The fore and aft ends are sloped slightly to reduce drag during the tow. I believe we can trust these naval engineers, who have spent years and millions of dollars in research, to determine the greatest LOAD carrying ability. Please notice I have made no comments on stability as these are generally so wide with relation to their height/depth that it does not become a significant factor.
BTW, the Germans wanted to use Helium, and did in their earlier airships, but the US refused to sell it to them. But that is another story also.

RE: Material that floats
 

As are some boats flat bottomed, but they have sloped sides to compensate for this. Anyway, enough bickering about physics. I do that all day long.

BTW, you are correct sir, with the Germans starting to pull the crap they were pulling (invading the rest of Europe and such), we told them no more Helium. Since Helium was not readily available to them, they picked the next best thing, Hydrogen. It just so happens that Hydrogen will react very violently. Ask our astronauts, its one of the fuels they ride into space on.

RE: Material that floats
 

Yep, I used to work with a couple of ex-NASA engineers. One was there during the time of the capsule oxygen fire that killed the crew on the pad.

RE: Material that floats
 

Not neccessarily. If the material has a density less than 1 (like balsa), you are correct. Otherwise it will sink. The example was meant to illustrate that shape affects volume. If the box is made of steel (like a ship) and you crush it, it will sink.

Maybe. It will only sink if the density is greater than 1 even if it's full of water (the material still has some volume even if the box/airplane is full of water). It's the total density of the object, not any one material that composes the object that will determine how it floats. If, when filled with water, there is still enough displaced volume to keep the overall density less than 1, then the object will float. That's why I suggested plastic air-filled bags in open spaces of the plane. The fuse and wings are full of air anyway, all you add weight-wise is the the weight of a plastic bag to seal that volume of air in place.

Yeah, kinda figured that would be tough to talk someone into. :)

But, you can figure out some estimate of buoyancy without doing that. Let's say you had a volume that looked like a box 20cm on a side. That's about 7.8 inches on a side. A typical .40 size plane probably has at least that much volume. You could just do some basic estimates treating the fuselage as a box and the wing as a box to check.

A cube that size has a volume of 20x20x20 or 8000cc. 1 cc = 1 ml. So an 8000cc volume would displace 8000ml * 1g/ml = 8000grams of water. 8000g/ (454 g/lb) = 17.6 lbs. So if the weight of the plane is less than 17.6lbs it has a density less than 1 and will float. It probably wouldn't fly though. :)

A plane that size is hopefully more in the 8 pound range. That weight would only need a total volume of about 3600ml (or cc) to float. That's a cube about 15cm or 6" on each side.

The point is that if you know how much volume is needed to support the weight of the plane, you just have to make sure that you have at least that much sealed volume (without adding additional weight) in order to keep the overall density less than 1. You don't need to know the actual total volume, you just need to know it's more than the minimum required.

I think we agree on most everything as well.
The shape doesn't affect bouyancy but it does affect stability and to some extent efficiency. Like bruce88123 pointed out, barges are often flat bottomed. Supertankers don't have much of a V either. The shape does affect things like stability with increasing load (like your example), drag due to frontal area, and the amount of surface area (material) per unit of volume. But, the shape doesn't directly affect the density (and therefore buoyancy), that's strictly a function of mass and volume like you pointed out in an earlier post. You can use most any shape to make any volume you like.

Ditto on all counts. Usually this kind of discussion just devolves into a slander-fest. It's nice to have the occasional civilized exchange on an internet forum just to prove it's possible. ;)