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PA-12 outperformed by identical PA-12 on floats

That's exactly what it is. It is not exclusive to Cubs, it's all 1650, 2000, and 2130s.

I put together a new set for my Citabria in 1978 but of course don't recall any specifics as it was a once in a life time deal. Float top to wing bottom angle was about 4.5* to 5*. I later put the same floats on a PA-18A and PA-12 with different rigging of course. I ended up lengthening the rear struts one bolt hole or 3/4" (non-extruded struts) on the 18 to get a bit more speed but the rest of the rigging for the other two was factory dimensions.

If 4-7 is installed incorrectly front or rear any idea of the change in angles? Like how adverse is the rigging?

Gary
 
I never measured it. Off the top of my head I'm guessing there is about 1/2" difference. It will also effect the toe in/out of the floats slightly. I never asked EDO but should have, why this is like this?
 
Toe in/out; non-parallel floats...well that would cause problems. Very good info.

I recall the eyebolts now because there was some green chromate tape that had to be applied to some fittings to seal and prevent corrosion. That and several weird aluminum bolts and nuts at the end of the spreaders.

Recommendations above to check the two PA-12's for float rigging, deck angles, and static thrust might be the clue to the different performance noted. Great discussion for the curious.

PS: I'd not lengthen the rear struts again on a PA-18 as the rear floats hit the tops of big waves during landing and T/O. Speed: Some more but not worth the stress up into the rear fuselage fittings.

GAP
 
I put together a new set for my Citabria in 1978 but of course don't recall any specifics as it was a once in a life time deal. Float top to wing bottom angle was about 4.5* to 5*. I later put the same floats on a PA-18A and PA-12 with different rigging of course. I ended up lengthening the rear struts one bolt hole or 3/4" (non-extruded struts) on the 18 to get a bit more speed but the rest of the rigging for the other two was factory dimensions.

If 4-7 is installed incorrectly front or rear any idea of the change in angles? Like how adverse is the rigging?

Gary
The photos in this thread are of my Cub on 2000s. http://www.supercub.org/forum/showt...gon-s-Smith-Cub-(Air-to-Air)&highlight=photos The struts are from a Citabria. The angle between the top of the float to the bottom of the wing is 3.5 degrees. I think that the double sized flaps keeps the tails from dragging. It's never an issue. It will operate easily out of a 900 foot pond and is faster than a -12 on wheels.
 
That's (+3.5*) about what I got by moving the upper ears on the old style rear struts out one hole. You have a nice plane and the angle looks similar to what mine did when adjusted. I left them extended like that for 10 years, was careful in rough water, then had to adjust them for the PA-12. Not sure of the difference but Eddie Peck offered the dimension changes. Hitting the heels only involved landing and taking off at 30-35 nose high. Never pass up short run headwind ops, eh? Landing roll on the water was less than 100'...it just hit and settled into the water with little planing. Sploosh!

Float rigging is an art and as noted by others previously has it's tasks. Today most just bolt them on and live with the result not knowing options exist. Having two PA-12's to compare (like here, or friends that consistently outperform) is enlightening.

GAP
 
I am waiting to see how this turns out. Pete the Skywagon helped me with a lot of suggestions when I was having rigging troubles in the past.

As an example I had a set of rather boxy floats installed by a well known IA. I helped as he measured and measured during installation. The floats worked, but they were doggy out of the water and would roll the ball off center when in cruise flight. Eventually the plane would stat a slight turn if left hands-off.

My buddy and I then loaded the plane evenly and let her float as we re-measured from a further distance. ( Left wing tip rivet to right-side float nose rivet.) There was only 3/8s of an inch difference over that long distance. (between measuring it both ways) But we adjusted the floats as she was floating and tried her again. The adjustment let me get out of the water about 300-400 feet sooner and it then flew with the ball dead center in cruise flight.
In the past I had one Cub's float's stern slightly lower than the other side. It made the plane doggy out of the water and it pulled left while on the step. 10 minutes with two wrenches and some hip boots cured the problem.

There is a local C-206 known for being a water dog. The owner / operator is always trying something new in the way of parts and mods. While everyone else is leaving on glassy water days, that plane is busy running out of lake. I have flown it a couple times and believe it is just wonky... Just one of those things.
 
Alex,

More than any other seaplane I've been around, there are floats that work pretty well on 206s, but a number of floats that don't work all that well. This lack of performance can be amplified by improper rigging, a lame motor, and especially pilot technique.

What floats are on that 206 you note is a dog?

MTV
 
I will have to see what he is using now. He has changed floats a couple times in his quest to avoid hitting the causeway or trees... Again.

On the other hand, since he is usually taking off around the same time as all of the other Beavers and 206s, his morning performance often affords some valuable teaching moments with my SES rating clients as we watch.

For a awhile the best local 206 off of our lake is one with Aerocets , Sportman Stol and VGs. It also helps that the owner/operator weighs 100 pounds less than the other local pilots and she actually knows what she is doing.
 
I've not flown a 206 but have watched them on floats. Do they have adjustments at the wing root for incidence? I flew a 185 that did and had the mechanic set it for maximum lift. It was slower in cruise but the takeoff was improved. That was with a non-Robertson stock Cessna camber cuff for the first engine, then a Sportsman cuff for the next two. The cuff helps as well.

How about prop...is it similar to others locally? Engine as MTV notes? Manifold pressure and rpm at takeoff?

About all I know about a 205/206 except for riding in them since the middle '60's. Heavy people don't run well either.

GAP
 
What floats are on that 206 you note is a dog?

MTV
Good point, I've not flown a lot of 206s but I have flown them on Seamaster amphibs which had a terminal velocity in the water of a speed below minimum flying speed. Also on PK 3500s it would get on the step quickly enough but then would run without wanting to fly. Also EDO had turbo 206 on their 3500 amphibs which did very well. When they replaced it with a newer one, that one was a dog. Got off worse and cruised slower. I don't believe that the reason was ever determined.

The 206 does have the incidence adjustment at the rear spar attach point.

Also I have found that the wing extensions make a tremendous improvement all around.
 
A friend and fellow rural resident has a very nice 206. IO-550, Big Mac prop with special sauce, wing extensions, Sportsman cuff, Robertson kit, and EDO 3500's of the latest variety I believe. Loads it up, straps externals on the floats, and never fails to takeoff as far as I can tell. Quite impressive in fact.

But...it's a built plane that received special care upon reconstruction and I'm sure the floats and engine/prop are well maintained and correct. Sometimes all it takes in care and money to make it work well.

GAP
 
View attachment Aircraft Float Rigging.xls
Based on what was discussed above, I compiled the attached spreadsheet (and pdf) so I can check everything out on my 2+2. Thought it may be useful to others. (Revised version)
 

Attachments

  • Aircraft Float Rigging.xls
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  • Aircraft Float Rigging.pdf
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Wag2+2 I am unable to read the Aircraft Float Rigging PDF attachment as it is too fuzzy. I sent you a PM requesting the excel file. I agree this could be very useful checklist to ensure nothing gets missed. Thanks for your post.
 
Pretty interesting thread. Having flown lots of different combos of float/206s or the years. I agree with Mike that
There is some wild variations in their performance. A lot of times floats can have unusual problems, Fishing Unlimited had a 206 in the late 90's that no one wanted to fly. I got the job of driving it around one summer and found it be be Scarry how weird it acted and how unpredictable it performed. I later flew it on wheels and it
Was actually an honest good performer. They tried everything know to cure it and finally did with a different
Set of 3430's ....... The airplane performed normally on the new floats. About a year or so later one of the pilots that had flown that 206 years before admitted to me that he had landed short at Big River with a full load in gusty wind
And hit the bank and then glanced into the water. When I asked how hard it hit he said. Real hard, hard enough that the rear doors flew open........he then said he noticed a huge change in the performance.....omg
 
Long shot and you have probably checked, possible growth on the bottom of your floats???...I had a fishing boat that got slower and slower over summer, and by end of summer would not plane out. (Equilivant to a seaplane getting up on the step.) Turned out an invasive species had gotten into our lake, and the bottom of the my boat (and everybody else on the lake who left their boat tied to their pier) was covered with growth about 3/4 of an inch, adding a massive amount of drag. Hauled the boat out of water, scraped the crud off, and bingo, boat was back to it's normal self.
 
For ten years, I flew a C-185 on late model PK straight 3500 floats, based at the Fairbanks float pond. That airplane was replaced (against my recommendation) by a U-206F, equipped with an IO-550 and Wipline 4000 straight floats. Both the 185 and the 206 were RSTOL equipped.

It took me a while to get the hang of the Wip 4000 floats (and they are still not my favorites), but once I did, I found that 206 would get out of the water at a MTOW of 3800 pounds at almost exactly the same spot the 185 launched at 3350 MTOW.

There's no doubt the extra oomph of that IO-550 made a big difference, but that's also a substantial weight difference.

We also had a 550 equipped F model 206 on Wipline 3450 amphib floats. Also approved at 3800 MTOW, and that airplane was a really good performer off the water. It had been thoroughly stripped of non essentials to lighten it up. It also had 125 gallons max fuel.

I'd have loved to have put a set of 3450 straight floats on the 206 with the 4000s. Those floats were water lovers, till I figured out that if you stomped hard on the rudder once the airplane was running clean on the step you'd actually turn the airplane somewhat sideways in the water, and it'd pop right out and fly.

A great way to make check airmen crap their pants, by the way.

I learned to love that 206, in any case. A real workhorse, and I took it everyplace I took the 185, with bigger loads.

MTV
 
For ten years, I flew a C-185 on late model PK straight 3500 floats, based at the Fairbanks float pond. That airplane was replaced (against my recommendation) by a U-206F, equipped with an IO-550 and Wipline 4000 straight floats. Both the 185 and the 206 were RSTOL equipped.

It took me a while to get the hang of the Wip 4000 floats (and they are still not my favorites), but once I did, I found that 206 would get out of the water at a MTOW of 3800 pounds at almost exactly the same spot the 185 launched at 3350 MTOW.

There's no doubt the extra oomph of that IO-550 made a big difference, but that's also a substantial weight difference.

We also had a 550 equipped F model 206 on Wipline 3450 amphib floats. Also approved at 3800 MTOW, and that airplane was a really good performer off the water. It had been thoroughly stripped of non essentials to lighten it up. It also had 125 gallons max fuel.

I'd have loved to have put a set of 3450 straight floats on the 206 with the 4000s. Those floats were water lovers, till I figured out that if you stomped hard on the rudder once the airplane was running clean on the step you'd actually turn the airplane somewhat sideways in the water, and it'd pop right out and fly.

A great way to make check airmen crap their pants, by the way.

I learned to love that 206, in any case. A real workhorse, and I took it everyplace I took the 185, with bigger loads.

MTV
Mike, what inspired you to do the rudder stomp? Is that a standard technique or did you have a hunch the plane needed to be thrown sideways for a moment?
 
Mike, what inspired you to do the rudder stomp? Is that a standard technique or did you have a hunch the plane needed to be thrown sideways for a moment?

Well, as much as I'd like to claim a scientific approach to improving takeoff performance, in actuality, I was on step one day and I performed an underwear adjustment.....and in the process, I stomped pretty hard on the right rudder pedal. That 206 leaped out of the water like it was goosed. Further experimentation revealed that it worked reliably.

Whats going on is the rudder application causes a yaw, and those huge floats go just a little sideways in the water. The only explanation I can offer is that the hydrodynamic forces applied against the left side bottom of the float push that float upward. The rest is just sorting it out once airborne.

And this sounds a lot more dramatic than it really is. While any yaw on the step feels huge, it's really not much.

Ive tried this on several other models of float and it didn't work. So, the only advice I can offer is don't try this at home folks.

Sorry, you can't make this stuff up.

MTV
 
The stomp technique was noted in my yearly float training in Anchorage by Ray Tremblay. He demo'ed it as an alternative method when other stuff hasn't worked (hey watch this!). Never have used it much since but Mike's right when it works it's a magic elevator.

Gary
 
I was out at the PK float factory a while back visiting with Keith Strange about a viscosity valve problem ( anyone remember how those work?) And noticed all their new bottoms had double " boosters" on the bottoms? I had not
kept up on their newest stuff. I asked Keith about it and he said that having the second one (spaced ever 1/3 rd)
Instead of one right in the middle is actually about 50% more effective, and helps the most when you really need it
"Hot n Flat Calm" . Apparently the first one closest to the keel, is more effective in breaking the water than if it is in the middle of the bottom. They are building some very nice stuff there. The PK 3000 is still one of my favorites on a 185.
 
Those floats were water lovers, till I figured out that if you stomped hard on the rudder once the airplane was running clean on the step you'd actually turn the airplane somewhat sideways in the water, and it'd pop right out and fly.

Whats going on is the rudder application causes a yaw, and those huge floats go just a little sideways in the water. The only explanation I can offer is that the hydrodynamic forces applied against the left side bottom of the float push that float upward. The rest is just sorting it out once airborne.

And this sounds a lot more dramatic than it really is. While any yaw on the step feels huge, it's really not much.

I've tried this on several other models of float and it didn't work. So, the only advice I can offer is don't try this at home folks.
I attribute this procedure to a reduction of water drag due to the slight change in the angle between the float and the water. When you kick the rudder, the plane yaws and banks slightly. This is similar to the technique of lifting one float out of the water to reduce the drag. A deep V float slices through the rough water better than a flatter float. A flatter float gets on the step quicker than a deep V bottomed float but has more difficulty slicing through big waves. Kicking it sideways momentarily flattens the angle to the water and lengthens the "leading" edge to the water (similar to increasing the aspect ratio) providing momentarily less drag and more lift.

I discovered this procedure with a 150 hp Colonial Skimmer. When getting on the step if you push full left rudder and down elevator the nose gets pushed down with the high thrust line and the hull is turned sideways presenting a wider hull lifting surface to the water. It will quickly be on the step without plowing for a long distance. What Mike discovered is a version of this procedure. It will not necessarily work on all combinations of airplanes, floats, loads, and water conditions.

Along the line of "abnormal" procedures, I'll throw this one out to you. When taking off in a crosswind do you lift the upwind or the down wind wing out of the water first and why? Have at it, I know what all the books say.
 
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I attribute this procedure to a reduction of water drag due to the slight change in the angle between the float and the water. When you kick the rudder, the plane yaws and banks slightly. This is similar to the technique of lifting one float out of the water to reduce the drag. A deep V float slices through the rough water better than a flatter float. A flatter float gets on the step quicker than a deep V bottomed float but has more difficulty slicing through big waves. Kicking it sideways momentarily flattens the angle to the water and lengthens the "leading" edge to the water (similar to increasing the aspect ratio) providing momentarily less drag and more lift.

I discovered this procedure with a 150 hp Colonial Skimmer. When getting on the step if you push full left rudder and down elevator the nose gets pushed down with the high thrust line and the hull is turned sideways presenting a wider hull lifting surface to the water. It will quickly be on the step without plowing for a long distance. What Mike discovered is a version of this procedure. It will not necessarily work on all combinations of airplanes, floats, loads, and water conditions.

Along the line of "abnormal" procedures, I'll throw this one out to you. When taking off in a crosswind do you lift the upwind or the down wind wing out of the water first and why? Have at it, I know what all the books say.
With a strong wind, and lots of room, it will be downwind wing for me. That lessens the chance of an upset and allows me to keep a straight track. In a really small pond, and light winds I often will let the wind under the upwind side and get out a little shorter.
 
Given a choice, I prefer to be straight into it; not always possible.
Would you believe that the FAA test pilot insisted that I demonstrate the maximum cross wind take off and landings while we were certifying the EDO 3500s on my 185? We did it in a large lake, the abuse on the plane was uncalled for. He wouldn't accept the fact that float planes usually go into the wind under those circumstances. When we finished the test, he declared that he wouldn't accept the demonstration speed because he considered me a better than average pilot. :9mmA lower speed was certified. We disagreed on the spin tests too.
 
Guess you were just too good, Pete!

Maybe he wanted a 50th percentile pilot. Plenty of them around.
 
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