J3 on floats: how does it fly with floats

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RonP

Pre-takeoff checklist
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I have pondered this for a long time and maybe someone can explain it. I only know some specs about the J3 and never owned one or flew one so I can only talk text book.

The stock J3 has a 65hp engine and can’t lift a lot, maybe 2 average adults and maybe 10 pounds of baggage. How does it fly with floats strapped to it? Doesn’t adding floats significantly increase the weight? Plus with only 65hp out front the floats add a lot of drag to haul around.

What’s the secret? Could it be what I am missing is the J3 on floats has a bigger engine such as 85 or 95 hp?
 
J-3, 65 hp is a challenge.
But, when you learn how, you can fly anything with wings off the water.
 
RonP said:
What’s the secret?
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The airflow is curved (or deflected if you prefer) to follow the top and bottom of the airfoil, and in accordance with Newton's laws, this results in a low pressure on top, relatively higher pressure on the bottom, and, voila! Lift! :)
 
I thought most of the J3s with floats had 85HP.
 
DFH65 said:
I thought most of the J3s with floats had 85HP.
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Brother had a J-3 w a C-90 that would perform really well even with two big guys.........

He also noted a Taylorcraft would do as well on floats w low hp as a J-3. Apparently the secret is the long wingspan.
 
nrpetersen said:
Brother had a J-3 w a C-90 that would perform really well even with two big guys.........

He also noted a Taylorcraft would do as well on floats w low hp as a J-3. Apparently the secret is the long wingspan.
Click to expand...
It just takes a bit longer & more room to get the floats up out of the displacement mode in the water and on step on top of the water. You will learn the J maneuver with the stick to get the first one planing and then the second one comes up easier.
 
I flew a J-3 with floats at Jack Brown’s I’m Florida. As I recall, they had C-90s or had otherwise been upgraded for more power.
 
Thanks to everyone that replied. The only item that makes sense to a non-aeronautical engineer is horsepower increase (greater than 65) to get a J3 off the water with floats.

I dismiss having the skill on floats to get anything airborne regardless of the additional weight. The floats definitely add weight and drag. Pilotage is definitely a positive however additional weight and drag can only be overcome by horsepower.

The floats are an upside down airfoil if you look at the side profile. A wing is curved more on the top than the bottom except for under cambered with the best example being a Clark Y. Floats are curved on the bottom and flat on top;I.E. an upside down airfoil which would lift down and not up. If the angle of attack of the floats add to lift then again drag is increased and only horsepower will get over the drag.

I did find a reference that a 90hp engine was used with an optional float kit. However I will fold my cards to those that have real world experience with a 65hp J3 on floats.
 
Curves vs flats have nothing to do with the fundamental physics behind how a wing generates lift.
The Clark Y airfoil is 98 years obsolete.
 
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