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Old May 30, 2011, 09:28 AM
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My floats use 1mm foam.

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Originally Posted by JoeR View Post
Has anyone tried 1mm foam? My hobby shop only has 1mm and 3mm. I did see a picture of a Vapor on floats made of 1mm foam in the latest MA mag in Joe Malnichek's(sp) column.
Here's a pic of my Champ, with its 1mm Depron, flat-bottom floats. I need to put some rudders on them, and get a place with a little water in it, and I
will try them out.
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Old May 30, 2011, 11:33 AM
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Here it is with a sub-fin added;

Using 1mm Depron, I sketched a pattern on a business card, then, using the natural curvature of the Depron for the sides of the fin, I glued the sub assembly together. It was necessary to remove the tail-wheel assembly, but
I have decided that this Champ will be permanently water-based, so it is not a problem.
Now a little paint, and the sub-fin is ready to fly.
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Old May 30, 2011, 11:41 AM
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I am not familiar with the sub-fin...What is it for?

That set of plans was the first set of floats i built for the champ and they worked,and i was using the 500 mah battery which is about 10 g more heavy than the stock battery.

Ridgewalker
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Old May 30, 2011, 01:12 PM
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Sub-fin;

For any given air vehicle, there needs to be a certain amount of lateral, (side) area, aft, to provide stability, (to keep it going straight ahead).
For example, if you took the scissors to the tail-feathers of an arrow, nipping off a little bit at a time, eventually, your arrow would not fly straight.
It took many years for airplane designers to understand the proper rel-
ationship of the size of vertical fin, to the rest of the aircraft. Sometimes they erred on the big side, but traditionally, they were too small.
When you add a fairly large amount of lateral area, like a pair of floats,
it is usually a good idea to add some vertical fin area aft. You will often see
this on Beavers, and many other float-planes.
The sub-fin I have installed is typical. It could be accomplished in other ways, but a sub-fin has little structural impact, so is practical.
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Old May 30, 2011, 01:33 PM
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@Lancer31 - The sub-fin is a very good idea. I guess that most people aren't doing this because they want to be able to go between water and land use. Still I like it!

Brian
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Old May 30, 2011, 01:35 PM
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Quote:
Originally Posted by Lancer31 View Post
For any given air vehicle, there needs to be a certain amount of lateral, (side) area, aft, to provide stability, (to keep it going straight ahead).
For example, if you took the scissors to the tail-feathers of an arrow, nipping off a little bit at a time, eventually, your arrow would not fly straight.
It took many years for airplane designers to understand the proper rel-
ationship of the size of vertical fin, to the rest of the aircraft. Sometimes they erred on the big side, but traditionally, they were too small.
When you add a fairly large amount of lateral area, like a pair of floats,
it is usually a good idea to add some vertical fin area aft. You will often see
this on Beavers, and many other float-planes.
The sub-fin I have installed is typical. It could be accomplished in other ways, but a sub-fin has little structural impact, so is practical.

Thank you!...for taking your time to give such an helpful explanation.

On real planes i have seen a vertical surface attached to the horizontal stab...is that done for the same reasons as the sub-fin?

Will a sub-fin also improve on the water tracking?


Ridgewalker
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Old May 30, 2011, 03:49 PM
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Quote:
Originally Posted by ridgewalker View Post
Thank you!...for taking your time to give such an helpful explanation.

On real planes i have seen a vertical surface attached to the horizontal stab...is that done for the same reasons as the sub-fin?

Will a sub-fin also improve on the water tracking?


Ridgewalker
A definate yes to both questions!
You will doubtless find full scale aircraft with both types of fins added, on the same plane, on float versions.
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Old May 30, 2011, 03:57 PM
Occupying RCG
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For example...
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Old May 30, 2011, 07:14 PM
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Glad you had that pic!

I wanted to mention the later Champ's dorsal fin addition, but didn't spend the time looking for it. This was done to the land-plane version, after Aeronca found that their original fin was less than adequate. Showing a seaplane, with the little fins on the horizontal stabilizer really closes the loop!
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Old May 30, 2011, 07:21 PM
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One of Mr. Bellanca's last...Just fer da fins.
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Old May 31, 2011, 10:36 PM
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Quote:
Originally Posted by Lancer31 View Post
For any given air vehicle, there needs to be a certain amount of lateral, (side) area, aft, to provide stability, (to keep it going straight ahead).
For example, if you took the scissors to the tail-feathers of an arrow, nipping off a little bit at a time, eventually, your arrow would not fly straight.
It took many years for airplane designers to understand the proper rel-
ationship of the size of vertical fin, to the rest of the aircraft. Sometimes they erred on the big side, but traditionally, they were too small.
When you add a fairly large amount of lateral area, like a pair of floats,
it is usually a good idea to add some vertical fin area aft. You will often see
this on Beavers, and many other float-planes.
The sub-fin I have installed is typical. It could be accomplished in other ways, but a sub-fin has little structural impact, so is practical.
No one couldn't have explained this any better...And no, this won't help at all with controlling the direction on water...Only a water rudder will do this...

To help with some degree of directional stability on the water you could add a fixed pair of rudders to the floats...There is enough rudder to help guide the plane straight...For ultimate water control a working water rudder is best...

Kevin
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Last edited by Kevin Greene; May 31, 2011 at 10:44 PM.
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Old May 31, 2011, 10:44 PM
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I tried my float modded Champ and it won't ROW...I know that it will fly because I hand launched it...It got too dark for me to experiment any further but I did increase the elevator to max throw and will try again tomorrow...I also know that a head wind helps and it was DEAD calm when I tried to ROW...The air temp was rather high too giving me not so great altitude density #'s which is not conducive to the power system making max thrust...

One more thing...I have this plane bound to my 10X..What a DIFFERENCE in flight control!!!....The plane is MUCH smoother than with the stock TX due to the better resolution of the 10X...In windy conditions is where you really notice the difference...

Kevin
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Old May 31, 2011, 10:53 PM
The lunatic is on the grass
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Try and be sure the plane gets up on step before pulling up elevator.

I first held up elev and just plowed through the water...after i let it get up on the step and pulled up elev it took off..i did need about 15-20 feet of water to get going.


Ridgewalker
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Old Jun 01, 2011, 10:38 AM
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Quote:
Originally Posted by ridgewalker View Post
Try and be sure the plane gets up on step before pulling up elevator.

I first held up elev and just plowed through the water...after i let it get up on the step and pulled up elev it took off..i did need about 15-20 feet of water to get going.


Ridgewalker
Good to know...It's been 20 years since I have flown from water----Ugly Stick w/ home made floats cut with my hot wire machine...

Kevin
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Old Jun 02, 2011, 01:12 PM
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I tried to get it to ROW and it's just not gonna happen on the small pond that I fly from without a stronger motor....Just as the plane gets up on step I run out of pond...And without a water rudder the plane is all over the place then straightens out when on step...

I'm going to put a UMX Mustang motor in mine and make a working water rudder that will be tied to the rudder servo...I've got the plans all worked out in my head...I will use a light weight flexible cable for the water rudder control...I'll post pics when I get all of the pieces together...

Since I have two Champs this one will be a dedicated float plane..

Kevin
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