Advice? My First Time Off Water
07-20-2003, 06:54 AM
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Advice? My First Time Off Water
Hi everyone, I haven't been on this site much this year since I crashed my last CUB flying it off the snow with some floats I made. I have cautiously gotten back into the hobby with a new Clipped Wing Cub from World Models, and I just recently built a new set of floats from the Cunningham plans (just like the set I built for my old full wing cub). I want to fly this one off water first, as I have a house on a lake, and will be up on vacation the first week of august. I will likely not be able to fly this thing on wheels first, so I want to be sure it will be ok on floats. The setup currently seems about perfect. The step is .5" behind the CG, the wing incidence is +3 degrees to the top deck of the floats, and the plane floated exceptionally well in a boyancy test. The plane is heavy (about 6.5 lbs i'd guess), but its powered by an OS .46FX, which flew my last cub off the snow with no problems at all. I have heard a lot of guys here talking about props getting sprayed and loosing power, and am concerned about the spray pattern on my floats. They are balsa decked/foam hulled that I carved and sanded by hand. They are veed in the front, and have a pretty deep-V to them along the keel. Is a V-hull going to push more water out to the sides than a flat hull? It would appear to me that the spray should be pretty flat, but I want to be sure. I also am not going to put a rudder on because the one I have (ernst) is too big, and I have a power boat so chasing the plane isnt a problem. What other tips can you guys give me about flying off water that I may not be thinking about? I know to get speed and not to force it off the water, but also should I consider using some flaperon or any other stuff? Thanks!
07-20-2003, 12:21 PM
#2
Advice? My First Time Off Water
Kevin,
It sounds as if you have done your homework well. You reference the Cunningham article, which is the most concise information I have ever found.
there are at least two ways to keep water out of your prop.
1. technique.
Start your takeoff run with full UP elevator to (a) tilt the airplane so the prop is further away from the water(b) align the thrustline so the plane gets extra lift to get up on the floats (c)moves the spray point back on the floats (d) Tilts the floats up for more initial hydrodynamic lift.
Just remember to relax the elevator as soon as you are up on step. It should not take more than a second or 2.
2. Chines.
You can add chines (Spray deflectors) to the front half of the floats. 3/8" triangle stock works well. If they are on the inside only, they act to keep spray out of the prop. If they are on the inside AND outside, they noticeably improve the time it takes to pop up onto the step. These are especially effective if you find your floats submarine when you add power. They can make the difference between taking off or NOT.
You said you were not using a water rudder. I take the somewhat controversial stand that you can do quite well without water rudders if you exercise appropriate technique.
I won't re-type it all here, but look at this thread
http://www.rcuniverse.com/showthread...0&pagenumber=2
see post #28..
It sounds as if you have done your homework well. You reference the Cunningham article, which is the most concise information I have ever found.
there are at least two ways to keep water out of your prop.
1. technique.
Start your takeoff run with full UP elevator to (a) tilt the airplane so the prop is further away from the water(b) align the thrustline so the plane gets extra lift to get up on the floats (c)moves the spray point back on the floats (d) Tilts the floats up for more initial hydrodynamic lift.
Just remember to relax the elevator as soon as you are up on step. It should not take more than a second or 2.
2. Chines.
You can add chines (Spray deflectors) to the front half of the floats. 3/8" triangle stock works well. If they are on the inside only, they act to keep spray out of the prop. If they are on the inside AND outside, they noticeably improve the time it takes to pop up onto the step. These are especially effective if you find your floats submarine when you add power. They can make the difference between taking off or NOT.
You said you were not using a water rudder. I take the somewhat controversial stand that you can do quite well without water rudders if you exercise appropriate technique.
I won't re-type it all here, but look at this thread
http://www.rcuniverse.com/showthread...0&pagenumber=2
see post #28..
07-20-2003, 05:54 PM
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Advice? My First Time Off Water
Thanks Jim,
From my float testing, it appears that I will have no problem with submarining. The floats are very buoyant, and they are covered in monokote, which seems very slick in the water. Also, my setup puts the plane pretty high over the floats (with a 12" prop, the bottom of the prop is 2.5" above the float deck). The floats tips extend 4.5 inches infront of the prop, although the key float angle plane (3 degrees before the front curve as per Cunningham's design) ends almost directly below the prop. The more I think about it the less worried I am about the prop hitting water.
One thing I haven't seen much written about is proper landing technique. What is the likelyhood of rolling the plane over on landing. How forgiving are the floats for less than perfect touchdowns, and how slow should it be coming down (upwind, downwind)?
From my float testing, it appears that I will have no problem with submarining. The floats are very buoyant, and they are covered in monokote, which seems very slick in the water. Also, my setup puts the plane pretty high over the floats (with a 12" prop, the bottom of the prop is 2.5" above the float deck). The floats tips extend 4.5 inches infront of the prop, although the key float angle plane (3 degrees before the front curve as per Cunningham's design) ends almost directly below the prop. The more I think about it the less worried I am about the prop hitting water.
One thing I haven't seen much written about is proper landing technique. What is the likelyhood of rolling the plane over on landing. How forgiving are the floats for less than perfect touchdowns, and how slow should it be coming down (upwind, downwind)?
07-20-2003, 06:28 PM
#4
Advice? My First Time Off Water
If you can land comfortably on a runway, you should not have much trouble. If you fly taildraggers, the technique is much like doing a "wheel" landing. Come in a little faster than stall speed, fly it an inch above the water's surface, an just let it touch gently. If you touch too hard it will bounce, and since you still have flying speed it will go pretty high. In essence, you get to make a second landing from 2-3 feet altitude.
you can do "Full Stall" landings, they're just not as pretty.
It's almost impossible to get a plane to nose over on landing.
THe worst thing you can do is to land crosswind. Then the plane will trip over the floats, the downwind wingtip digs in, and it'll tip right over.
Mostly, just don't sweat it. Land it like every other airplane you have flown. THe biggest danger is hitting the trees on the opposite bank as you turn final. I find that I work really hard at making smooth, gentle touchdowns,and that has improved my wheel landings noticeably.
you can do "Full Stall" landings, they're just not as pretty.
It's almost impossible to get a plane to nose over on landing.
THe worst thing you can do is to land crosswind. Then the plane will trip over the floats, the downwind wingtip digs in, and it'll tip right over.
Mostly, just don't sweat it. Land it like every other airplane you have flown. THe biggest danger is hitting the trees on the opposite bank as you turn final. I find that I work really hard at making smooth, gentle touchdowns,and that has improved my wheel landings noticeably.
07-20-2003, 07:06 PM
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Advice? My First Time Off Water
Kevin, I've included a photo of a landing that was a little too hard! The float filled with water, then the wing tip started taking on water and almost filled the wing before the plane was retrieved.......Seaplane
07-20-2003, 07:09 PM
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Advice? My First Time Off Water
Here's another too hard landing. The damage was not noticed and the pilot too off again, but noticed a severe trim problem. This was due to the water sloshing around in the float.....Seaplane
07-23-2003, 02:03 AM
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Advice? My First Time Off Water
If you touch too hard it will bounce, and since you still have flying speed it will go pretty high
you can do "Full Stall" landings, they're just not as pretty
07-23-2003, 10:10 AM
#9
Advice? My First Time Off Water
By "full Stall" landing, I mean the conventional wheeled-type landing where the plane touches down just as the stick comes full back, and the stall horn peeps juat as the wheels touch. This is the absolute minimum speed landing, but it is not rough on the plane. Conversely, stalling the plane at 20 feet and having it fall into the water would be bad.
WHat's really pretty in a seaplane is to come in really low, establish a bare minimum rate of descent, and fly the plane at a slow cruise speed. One minute it's flying, and the next minute it's making a wake on the water. the water will progressively slow it down until it drops off step. It's hard to get it juuuuust right, but I have gotten lucky a few times.
WHat's really pretty in a seaplane is to come in really low, establish a bare minimum rate of descent, and fly the plane at a slow cruise speed. One minute it's flying, and the next minute it's making a wake on the water. the water will progressively slow it down until it drops off step. It's hard to get it juuuuust right, but I have gotten lucky a few times.
07-23-2003, 04:53 PM
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Advice? My First Time Off Water
By "full Stall" landing, I mean the conventional wheeled-type landing where the plane touches down just as the stick comes full back, and the stall horn peeps juat as the wheels touch. This is the absolute minimum speed landing, but it is not rough on the plane. Conversely, stalling the plane at 20 feet and having it fall into the water would be bad.
