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Float design safety

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Doggzilla

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Was recently watching a video of a ground effect aircraft skimming the water on a lake and it occurred to me how the design of most floats is unstable after a crash and could drown an unconscious pilot.

Consider this...

If you take a float aircraft and turn it sideways and drop it in water... what happens?

For most aircrafts the top half would sink, since that’s the heavy half, and the bottom half would float due to having the floats attached.

A quick google shows this is quite common in float plane crashes.

Landing on any side but the bottom of the floats will likely invert the aircraft and leave it floats upward.

What solutions are available for this?

Personally I believe adding a small floats similar to a large head rest would greatly reduce the threat. This would result in a sunken aircraft turning sideways and not being completely inverted by the floats. Not perfect, but definitely superior to being completely inverted. Especially as it would give vastly better access to any boaters acting as rescuers.
 

Mad MAC

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I seem to recall Darrol Stinton (of the text books) promoting applying yacht bow shapes to flying boat hull design, but I don't recall what became of it (its been while and his website has disappear so the details are a bit foggy).
 

wsimpso1

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Sailboats have been running masthead floats for decades to prevent inversion, called "going turtle". They are substantial in both volume and in height even for relatively low mass catamarans, suggesting that such an anti-inversion float on a float airplane might need to be quite large and or quite high to be effective.

I would suggest a calculation of righting moment needed to simply prevent inversion from both a 90 degree pitch angle and from a 90 degree roll angle position of a common float plane. This will then suggest the range of height and float volume needed to work for this task. I suspect much more mast height and float volume is needed than will be practical to carry in flight.

I might suggest that one that is stowed in a recess high in the airplane and automatically deployed could be useful. To be useful, it would have to:
  • Be able to wait without maintenance;
  • Sense the plane being in water and upset with great reliability;
  • Be able to reject spurious sensing and deployment;
  • Reliable deployment once called upon;
  • Either be:
    • Fast deploying to catch the airplane while still in capsize or pitch-pole position or be;
    • Large enough to restore capsize position from inverted position- righting moments needed from inverted are much higher than from capsize, and the moment arms are very small.
I might suggest that since this has already been thought about, there may be little in the way of novelty to the idea. Perhaps there is room in the design space for executing something new. If so, please remember to include my name in the Patent filings. You can reach me for specifics through PM.

Billski
 

BJC

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Perhaps there is room in the design space for executing something new. If so, please remember to include my name in the Patent filings. You can reach me for specifics through PM.

Billski
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If you need a late night cable TV ad catch line, let me know.


BJC
 

BBerson

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"whatever floats your boat" :D
Nothing will right an upside down seaplane. But enough flotation or foam on the upper cabin might help. The problem is most floatplanes are already too heavy.
The little RC floatplanes are made of foam so they mostly float above the water with the floats high above.

Landing nose first on the front of the float is what flips them upside down.
 

wsimpso1

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"whatever floats your boat" :D
Nothing will right an upside down seaplane. But enough flotation or foam on the upper cabin might help. The problem is most floatplanes are already too heavy.
The little RC floatplanes are made of foam so they mostly float above the water with the floats high above.

Landing nose first on the front of the float is what flips them upside down.
Or leaving the wheels down for a water landing.

I have met Jan Gougeon (at Sun-n-Fun, Mister Fiberglass Boat was flying an all metal RV-4). Jan built and demonstrated a racing boat designed for long single handed races that was able to be self rescued. Based upon his work, I do think there are ways this could be done to make a float plane that just tripped over its gear settle to capsize position, then with more manipulations, back on its feet.

Billski
 

Doggzilla

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Ya I think Billski is right here.

An automatic inflatable system would likely be the best option.

To prevent accidental deployment it should require at least two switches, one sensing water, and one sensing orientation. The only chance of a premature deployment would be if the pilot pulled a negative G while experiencing some sort of leak. Which is an unlikely combination and far less likely than a crash.

There should also be lights to indicate if a sensor is shorting, and a switch on each sensor to allow the pilot to disable them if the light indicates a short.
 

Hephaestus

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Wasn't there some work in the naca era on hydrofoils for this type of scenario?
 

Doggzilla

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Yes, the reason they weren’t adopted was because they are unsafe during collisions. Hitting a log or rock will damage floats, but it will likely completely separate a hydrofoil and cause extreme unsafe behavior.

To safety use a hydrofoil it would have to be designed like a hydrofoil surfboard so that there is a backup surface after a collision.

Putting a hing on the rear and a shock near the nose would allow it to flex during an impact and reduce the chance of fatal detachment.
 

Hephaestus

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Compared to a float hitting a submerged object and result being the same?

I thought it was a hinged device that rotated down beneath the standard floats? Or am I confusing similar ideas?
 

Doggzilla

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Since floats run on top of the water they tend to survive impacts but with chunks of foam missing.

The hydrofoils tend to be within the water and therefore take much more direct hits.
 

Hephaestus

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Just going by the crashes this year ;) floats haven't been bouncing off submerged objects so well - usually ends up with an upside down spamcan.

I think that was the point of the NACA study... That's why I mentioned it.
 

Hephaestus

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Perhaps - but they also didn't have microprocessors and quarter sized GPS,Gyro and INS systems like we have today.

It would take 2 very small and light hydroplanes with minimal electronics to add a heading and attitude control to a float aircraft.
 

choppergirl

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Cut out big chunks of white styrofoam to fit the empty spaces and put inside the last couple of feet of the tips of your wings? Will help in a sideways, but won't help in a nose over flip though.

Another problem to me seems like the fronts of floats are designed to pull you under water once they go past a certain angle...
 

Aerowerx

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What's that stuff that generates hydrogen when in contact in water? Used to inflate balloons in WW2 life rafts.

Just put a balloon on the top of the plane, with some of that stuff. Then when it gets wet it will automatically inflate the balloon and right the plane.
 

Himat

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As BBerson say, a high wing RC floatplane will float upside down on the wing and forward part of the floats. The cabin will stay mostly out of the water. That is if the plane still is in one piece. If the airplane stays in one piece, the wing and floats stay buoyant, a full-size plane will probably do the same. D Hillbergs ping pong ball scheme may actually work.

A high wing flying boat configured like the Lake or Seabee would need a buoyancy in the wing and in the nose of the airplane. Still, the cabin may be partly submerged if the airplane float upside down.
 

bifft

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Would foam core composite wings work for this? They should float pretty good.
 
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