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PA18-105 special.

While we are on the subject, here is reason #3.

The only difference between the EDO 1650 and 2000 floats is 23 3/8" in length. All of which is forward of the step. An additional 8" made them 2130s.

In rough water, the ability to remain on the step is effected by the length of the forward section of the float in relationship to the distance between the wave tops. Primarily the flat section of the keel between the step and the location where it starts to curve upward to the bow. Also the optimum angle between the keel and the water surface while on the step is approximately 8 degrees.

With that in mind the 2000 floats can remain on the step with the wave tops being 2 feet further apart than the 1650s. When the waves are too far apart but also higher than just a few inches, on 1650s the plane would climb up one side of the wave and down the other. As you can imagine, if the airplane does not change it's pitch attitude the angle of the bottom of the floats to the water changes considerably depending on the shape of the waves. From minimum drag angle to maximum drag angle and back again. Low power and short floats just can not overcome these obstacles.

I had a friend with a homebuilt (Acey-Ducy) 100 hp on 1650 floats. He had trouble getting off in rough water because it kept falling off the step between the waves. This because that 8 degrees disappeared between the waves so it had to start over. We solved his issue by making a new longer set of wings to reduce stall speed and added 50 hp to the nose. Now it had the power to jump from wave top to wave top. But it still had a float/wave issue which the engine and wing were more able to overcome.
 
While we are on the subject, here is reason #3.

The only difference between the EDO 1650 and 2000 floats is 23 3/8" in length. All of which is forward of the step. An additional 8" made them 2130s.

In rough water, the ability to remain on the step is effected by the length of the forward section of the float in relationship to the distance between the wave tops. Primarily the flat section of the keel between the step and the location where it starts to curve upward to the bow. Also the optimum angle between the keel and the water surface while on the step is approximately 8 degrees.

With that in mind the 2000 floats can remain on the step with the wave tops being 2 feet further apart than the 1650s. When the waves are too far apart but also higher than just a few inches, on 1650s the plane would climb up one side of the wave and down the other. As you can imagine, if the airplane does not change it's pitch attitude the angle of the bottom of the floats to the water changes considerably depending on the shape of the waves. From minimum drag angle to maximum drag angle and back again. Low power and short floats just can not overcome these obstacles.

I had a friend with a homebuilt (Acey-Ducy) 100 hp on 1650 floats. He had trouble getting off in rough water because it kept falling off the step between the waves. This because that 8 degrees disappeared between the waves so it had to start over. We solved his issue by making a new longer set of wings to reduce stall speed and added 50 hp to the nose. Now it had the power to jump from wave top to wave top. But it still had a float/wave issue which the engine and wing were more able to overcome.

Pete,

Thanks for sharing all your knowledge with us. I very much enjoy learning from your posts.

Jeff


Sent from my iPhone using SuperCub.Org mobile app
 
Priceless information that is only obtained through years of experience. I’ve learned more from a few paragraphs of Pete’s then I have entire books on the subject.


Sent from my iPhone using SuperCub.Org
 
I too will chime in. Thank you for sharing all your experience and knowledge. Folks like you are what make this such a great site.

Thank you Pete

Bill
 
For whatever airplane to determine the minimum sized float. Take the maximum gross weight (1760 for a PA-18 X 0.9 = 1584 X 2 (two floats). FAA requires a 100% reserve buoyancy. So the smallest float for a PA-18 at 1760 pounds would be a pair of 1584s. The nearest float which meets these numbers of which I am aware would be the EDO 1650.

Educate me.. What am I missing? If required reserved buoyancy is 100%, wouldn't each float be required to float the plane at gross? IE, 1750 gross, each float floats 1750?
 
For whatever airplane to determine the minimum sized float. Take the maximum gross weight (1760 for a PA-18 X 0.9 = 1584 X 2 (two floats). FAA requires a 100% reserve buoyancy. So the smallest float for a PA-18 at 1760 pounds would be a pair of 1584s. The nearest float which meets these numbers of which I am aware would be the EDO 1650.

Educate me.. What am I missing? If required reserved buoyancy is 100%, wouldn't each float be required to float the plane at gross? IE, 1750 gross, each float floats 1750?
Now your making me look up numbers instead of relying on my old memory. ;-) What I've described is the way I was told about the procedure to do the calculations.
If we take the max gross of the 172 seaplane of 2222 lbs for an example. 2222 lbs X 90% = 1999.8 lbs (size of the float) X 2 floats (100% reserve). CAR 3.370(b). OK, so they rounded up the number by 2 tenths for the EDO 2000.

CAR 3
3.370 Buoyancy (main seaplane floats). Main seaplane floats shall have a buoyancy in excess of that required to support the maximum weight of the airplane in fresh water as follows:
(a) 80% in the case of single .floats,
(b) 90% in the case of double floats.
Main seaplane floats for use on airplanes of 2,500 lbs. or more maximum weight shall contain at least 5 watertight compartments of approximately equal volume. Main seaplane floats for use on airplanes of less than 2,500 lbs. maximum weight shall contain at least four such compartments.

FAR 23
[h=2]§ 23.2310 Buoyancy for seaplanes and amphibians.[/h] Airplanes intended for operations on water, must -
(a) Provide buoyancy of 80 percent in excess of the buoyancy required to support the maximum weight of the airplane in fresh water; and

(b) Have sufficient margin so the airplane will stay afloat at rest in calm water without capsizing in case of a likely float or hull flooding.
 
This is how I read it: The floats should support 190% of the gross. 1.9 x 2222 = 4221.8. I still don't know how 100% reserve pencils out from the equation.
 
...your 125 hp Cub...
Don't I wish. I'd give anything for even an O-290 right now but I only have an O-235 - Bummer. But like I've said, I'm just hoping to lighten this Cub enough to make a reasonable single place floatplane.
...An under floated seaplane is a recipe for trouble...When you have a choice of minimum or excess floatation and you are looking forward to a safe operation, always choose the larger float. Until you accumulate an amount of seaplane experience, you will not understand…
Got it! And thank you for that advice.
...The Cub which I flew on 1650s easily took double the time and distance to get on the step than an identical Cub on 2000s. Once on the step the remaining distance was similar. So in other words, if you can comfortably operate a Cub on 2000s out of a 900 foot pond, you may never get on the step with the 1650s...
The smaller lighter floats took double the distance to get on the step, Holy cow - This is good stuff!!!
Thanks so much for sharing your knowledge.
 
Don't I wish. I'd give anything for even an O-290 right now but I only have an O-235 .
Oops, you're right, you did say that. I got carried away with the discussion. With an 0-235, what I've said is even more important.
 
This is how I read it: The floats should support 190% of the gross. 1.9 x 2222 = 4221.8. I still don't know how 100% reserve pencils out from the equation.
Then by your calculation, the minimum sized approved float for a 172 at 2222 lbs max gross would be a 2111 displacement sized for use in fresh water.
The method I've described in calculating the float size above was taught to me by EDO's chief engineer. We did a lot of work together in flight testing a new design. Only later did I look up the regulations. It should be noted that it is not unusual for FAA regulations to be worded in an ambiguous manner.
 
One should not forget that with your same 0235 engine, Piper chose Edo 2000's for the original PA-12. Which contrary to popular believe; was actually not much heavier than your airplane....... ( My factory W/B on our Cruiser w/115 was under a 1000 lbs)......
There is a darn good reason they had 2000's under most Cub style models that sported a Lycoming engine.
Good luck with you new Cub
EScreenshot_20220722-033201.png
 

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Then by your calculation, the minimum sized approved float for a 172 at 2222 lbs max gross would be a 2111 displacement sized for use in fresh water.
The method I've described in calculating the float size above was taught to me by EDO's chief engineer. We did a lot of work together in flight testing a new design. Only later did I look up the regulations. It should be noted that it is not unusual for FAA regulations to be worded in an ambiguous manner.

I certainly don't doubt your calculations or what the engineer told you, I am leaning towards the ambiguous manner of wording.
 
Just curious, how did it do on 1400's with the O-235? I just got a "Special" with an O-235 also. I'm hoping to put it on a serious diet and hoping it will make a reasonable single place floatplane?

Sorry for the late reply. I never flew 18K with the floats installed. The 1400s were pretty tired. I sold them to a Champ owner in Maine. I arranged a fittings swap between the Champ owner and a SCub owner in Vermont.
 
swatkins1950
Just bought N181T. Looking for information or pictures of original paint design and color/s. Thought I saw someone post that they had a black/white picture of N181T, but can't locate the post.
Thanks
 
Swatkins,
I got my Tango Cub from the Civil Air Patrol in the ‘60s and it was all silver. During rebuild I found yellow underneath. N number originally was on the rudder and I have that drawing if you are interested. I believe they left the factory in “Cub yellow”, don’t know about the lightning stripe down the side. Still have mine, N227T.
 
Swatkins,
I got my Tango Cub from the Civil Air Patrol in the ‘60s and it was all silver. During rebuild I found yellow underneath. N number originally was on the rudder and I have that drawing if you are interested. I believe they left the factory in “Cub yellow”, don’t know about the lightning stripe down the side. Still have mine, N227T.

Thanks, would greatly appreciate any info. Just starting on getting mine flying after 20 years sitting in a hanger. It appears to have some yellow paint under the cowling, as well.
 
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