# Is it a question of proportions? Water hull shape and water handling?

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#### Riggerrob

##### Well-Known Member
Dear Pilot-34,
Yes, modern composite materials can help reduce both empty weight and corrosion.
Consider that to operate along side Cessna float-planes, you need a high-wing flying-boat ... with the wings almost as high as a Cessna to avoid knocking dock-hands off the dock.
Some Grumman Geese were modified with retractable tip floats. Retracting trip floats were retracted when approaching a dock and the airplane "leaned" on its outboard tip float.
Republic
Seabee has a reputation for being one of the best small flying boats, so I would look at its Spencer Air Car and Trident Tri-Gull successors. TriGull never made it into production, but one of them sat on the Victoria International Airport ramp for many years.
I suspect that Spencer extended the aft hull to reduce porpoising, but would like to hear from more experienced seaplane pilots about which factors most reduce porpoising.

I suspect that many flying boats have short hulls (Coot, Seabee, Martin Mariner, etc.) to reduce weight. OTOH later flying boats (Martin Marlin, Volmer Sportsman, Anderson Kingfisher and Lake) have long rear hulls to reduce proposing.

#### blane.c

##### Well-Known Member
HBA Supporter
Really slick hulls like fiberglass accelerate quickly but take forever to slow down in the water.

HBA Supporter

#### malte

##### Well-Known Member
Hey,

there are several items to discuss here.

First my background on the topic: I have some hours on an amphib 172, more on my Lake that we use for Earth Observation Projects (Flight Ops – AUFWIND). I have written my Bachelors Thesis on seaplane configuration design and my Masters Thesis on flying boat hull optimisation for loads and handling characteristics.

The Buccaneer is good for operating in around one foot waves. That is surely enough for most lakes or some of the bays or fjords around here and probably would be fine, too, in many Alaska situations.

The main driver for classic hulls are step loading, (the mass of the aircraft divided by the cube of the width of the step multiplied by the density of the water) and the slenderness ratio (length of the hull divided by step width). The Buccaneer isn't very good at it, in contrast to the heavier flying boats. It's $$c_\Delta$$ is around 0.91 and the slenderness ratio of the hull at around 7. The Grumman Wigeon has similar values and both are certified for around 1ft waved (crest to trough). My guess is that Gewduck will be capable of similar sea states.

For comparison, the Shin Meiva SS-2A has a slenderness ratio of 11,6 and a step loading of 3,1.
Floats are a bit better than our small flying boats, the Wipline floats have a slenderness ratio around 8 and an almost doubled step loading.

Having said that, the Buccaneer has been flown out of 2 feet waved (lightly loaded) and can survive 10ft waves easily once in the water (although reportedly you are in for quite a ride then.) I would not want to try this in a float plane.

The Lake LA-4-200 is considerable more manoeuvrable in the water, compared to a typical float plane. One of the problems of the latter is the huge exposed area. The weather-vane effect on floatplanes is considerable larger than on the Lake and the water rudders are less effective (partly because on most float riggs one of the water rudders stall in displacement turns). I have been in a C172 on Wipline amphibs on the fjord in 14kt wind without any possiblilty to turn the aircraft out of the wind due to the strong weather-vane effect and low water rudder effectiveness. The Lake has no such problems.

The high center of gravity makes it a bit more difficult to step-taxi a floatplane compared to the Lake. You can demonstrably even takeoff in a tight turn on the water with the Lake and stop after a landing in a J-Hook turn. Just look at what Thomas does with his Lake to get the idea:

Having said that, mooring, docking and handling is considerable easier with a floatplane than with the low winged Lakes. I reckon this is the main reason they are used more in the wilderness. Boarding/loading is more comfortable and they are not so sensitive to mass and balance than the Buccaneer or Renegade. And spare parts are more widely available because of the landplane-cousins. (Although I have no trouble locating Lake-parts).

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#### blane.c

##### Well-Known Member
HBA Supporter
The O'Neill intrigued me, Magnum Pickup it would be interesting to see if a 985 would fit, it would likely perform nicely with a real engine.

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#### blane.c

##### Well-Known Member
HBA Supporter
Rutan's Ski-Gull is to small for your needs but may provide inspiration for a larger version maybe with two engines like the Dornier Seastar or the modified Cub Double Ender.

#### BBerson

##### Light Plane Philosopher
HBA Supporter
Lakes are ice free about 5- 6 months in Alaska. The planes make money on skiis in the winter months. Have not seen any Lake Amphibs on skiis.

#### blane.c

##### Well-Known Member
HBA Supporter
Make your way out the lake ahead of time, clear snow off airstrip area, auger hole in ice and using water pump, pump water on top of ice (increases ice thickness) now you have nice runway on lake.

#### Pilot-34

##### Well-Known Member
Lakes are ice free about 5- 6 months in Alaska. The planes make money on skiis in the winter months. Have not seen any Lake Amphibs on skiis.
I have been told but I have never seen that if the snow is too deep for the wheels it’s just fine for the hull.
Anyone have any experience with that?
It seems like I have seen a buccaneer on skis.

#### Pilot-34

##### Well-Known Member
Russ Williams was over 80 years old so his wife made him take somebody flying when he went, I was lucky to fly with Russ numerous times. I liked to fish with Russ, his idea of fishing was to fly out between Rampart and Tanana and look for a fish wheel operating on the Yukon, He would land the 1960 180 on straight floats on the river taxi up to the fishwheel operator and politely ask if they wanted to sell some fish. Sure was a good fishing machine the 180. The stretch of river mentioned is some of the fastest flowing water on the Yukon river in the USA portion. 236 feet elevation in Tanana, 306 feet elevation in Rampart and 60 miles apart.

It would be better the 185 on amphibs.
The man was obviously a genius I love the way he fishes!

#### BBerson

##### Light Plane Philosopher
HBA Supporter
I have been told but I have never seen that if the snow is too deep for the wheels it’s just fine for the hull.
Anyone have any experience with that?
It seems like I have seen a buccaneer on skis.
It can be done, I've flown a C-150 on skiis with the nose ski.
But the hull weight is still there, unlike a C206 with the floats removed and filled with cargo through the huge door.

#### Marc W

##### Well-Known Member
The man was obviously a genius I love the way he fishes!
I was waiting for the half stick of dynamite out the window, then land and drag a net as you taxi back for takeoff!

#### blane.c

##### Well-Known Member
HBA Supporter
I was waiting for the half stick of dynamite out the window, then land and drag a net as you taxi back for takeoff!
That is called DuPont fishing.

##### New Member
Anyway back to the original question what seaplane or float hull is generally considered to be the best handling among the what are pilots here?
For 4-seaters the best amphib is the Seabear series: L42 - Rotax 912's, L44 - 914's, L45 - 915's, L65 - 915's with a larger cabin (4-6 seats) and hull, L72 - Lycomings.

Not many rotax-powered amphibians can climb on one engine at gross weight. These can. At full power on one engine no more than 1/3 rudder deflection is needed due to the twin vertical fins, one in the slipstream of the working engine. The thrust lines are also close to the centerline since the engines are mounted well forward and the props can overlap part of the fuselage width. Combined with the long aspect ratio wings ( the offset of the thrust line is a relatively small fraction of the wing span) this leads to very benign single engine handling.

I would also include the CHE-29. Not by coincidence all of these twins have beautiful hull forms. They are products of graduates of the aviation university in Samara.

For 2-seaters I would say the Super Petrel.

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#### Riggerrob

##### Well-Known Member
How much of a difference do step vents make?

#### blane.c

##### Well-Known Member
HBA Supporter
I am guessing if you have a surplus of power not much, if you are marginally powered they could be more of a deal. In flat water taxiing downwind broad "S" turns will leave a light chop on the water to help break suction during taking off.

#### malte

##### Well-Known Member
I have been told but I have never seen that if the snow is too deep for the wheels it’s just fine for the hull.
Anyone have any experience with that?
It seems like I have seen a buccaneer on skis.
There was a picture in the Lake owners group quite recently. It's reported to be easier than on ski, due to the higher contact area (you don't sink in that much). Landing and takeoff is said to be very similar to fluid water.

How much of a difference do step vents make?
If positioned correctly, quite a lot actually. Dawson did some tests in Langley without finding a measurable differene in resistane, but tests with the Dornier 18 and Dornier 4 showed an appreiable effet. The most important funtion of a proper step ventilation for rough water operation is the reduction of skipping with shallower steps and thus an increased seaworthiness with lower air drag.

If you really waant to improve the seaworthiness of the Lake, you need to add hydrofoils. This is the easiest option for this hull as an "aftermarket"-mod

#### Pilot-34

##### Well-Known Member
Hey,

there are several items to discuss here.

First my background on the topic: I have some hours on an amphib 172, more on my Lake that we use for Earth Observation Projects (Flight Ops – AUFWIND). I have written my Bachelors Thesis on seaplane configuration design and my Masters Thesis on flying boat hull optimisation for loads and handling characteristics.

The Buccaneer is good for operating in around one foot waves. That is surely enough for most lakes or some of the bays or fjords around here and probably would be fine, too, in many Alaska situations.

The main driver for classic hulls are step loading, (the mass of the aircraft divided by the cube of the width of the step multiplied by the density of the water) and the slenderness ratio (length of the hull divided by step width). The Buccaneer isn't very good at it, in contrast to the heavier flying boats. It's $$c_\Delta$$ is around 0.91 and the slenderness ratio of the hull at around 7. The Grumman Wigeon has similar values and both are certified for around 1ft waved (crest to trough). My guess is that Gewduck will be capable of similar sea states.

For comparison, the Shin Meiva SS-2A has a slenderness ratio of 11,6 and a step loading of 3,1.
Floats are a bit better than our small flying boats, the Wipline floats have a slenderness ratio around 8 and an almost doubled step loading.

Having said that, the Buccaneer has been flown out of 2 feet waved (lightly loaded) and can survive 10ft waves easily once in the water (although reportedly you are in for quite a ride then.) I would not want to try this in a float plane.

The Lake LA-4-200 is considerable more manoeuvrable in the water, compared to a typical float plane. One of the problems of the latter is the huge exposed area. The weather-vane effect on floatplanes is considerable larger than on the Lake and the water rudders are less effective (partly because on most float riggs one of the water rudders stall in displacement turns). I have been in a C172 on Wipline amphibs on the fjord in 14kt wind without any possiblilty to turn the aircraft out of the wind due to the strong weather-vane effect and low water rudder effectiveness. The Lake has no such problems.

The high center of gravity makes it a bit more difficult to step-taxi a floatplane compared to the Lake. You can demonstrably even takeoff in a tight turn on the water with the Lake and stop after a landing in a J-Hook turn. Just look at what Thomas does with his Lake to get the idea:

Having said that, mooring, docking and handling is considerable easier with a floatplane than with the low winged Lakes. I reckon this is the main reason they are used more in the wilderness. Boarding/loading is more comfortable and they are not so sensitive to mass and balance than the Buccaneer or Renegade. And spare parts are more widely available because of the landplane-cousins. (Although I have no trouble locating Lake-parts).
Ive heard the key to morring docking Handel ig and loading is to get your wheels down in the water then taxi out of the water?

#### malte

##### Well-Known Member
Ive heard the key to morring docking Handel ig and loading is to get your wheels down in the water then taxi out of the water?
Yes, but you need a place where you actually can taxi out, so either a solid beach or a ramp. You find these possibilities seldom in harbours and even on some lakes it won't work. In Sedlitz, the only official open water-landing site in Germany, there is no possibility to taxi out of the water. There is a berth and a beach too loose and too steep to taxi out on. The rest is covered in reed or gravel:

The Lake has a very low clearance at the step, not suitable for big gravel bars, even if the gear itself would have no trouble:

#### Pilot-34

##### Well-Known Member
I like the engine mounting location on the sea bear.
I think placing the propeller significantly forward and mostly above the leading edge of the wing gives it a large portion of the Custer channel wing effect..
It would appear to be two significant downsides to the Seabear.
As a twin you’ve got two engines to operate such a beautiful classic Image reaching up to operate twin overhead throttle but also pricey.
And as a new plane let me repeat oh so pricey!