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Thread: Questions of seaplane hull choices

  1. #1

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    Questions of seaplane hull choices

    A few questions for anyone and all. Seaplanes and airplanes. The aircraft deals with the one environment while the seaplane deals with both. From the unknowing point of view.(mine).
    It seems to me that hull designs aren't what they should be. While heavy general aircraft can enjoy a power upgrade to get a stable hull airborne. For an U/L. Efficiency is the correct choice .Sometime sacrificing stability for weight . But what is the correct choice?
    The dynamics of the water would say streamline cutting hull low drag.
    Or Should we be using a flying hull .like a hydroplane? I looked at many attempts to turn U/L into seaplanes before I made my choices. Frankly I didn't succeed there. My plane sucks in the water literally.It works but only barely. My plane[Norms flying boat] for those that may read this only.
    I am redesigning the hull and looking for a better way to get it done.
    Question why do you think the weight shift Zodiac float plane gets airborne at all???
    Is it by Power alone or is there something else at work here? A tunnel hull effect maybe?
    If a person can ski on there bare feet at X miles per hour behind a boat.
    Then there must be a factor out there that says exactly what amount of square ft of surface. For a given speed, for a given weight.
    Is there a chart or calculation table out there some where?
    I studied A boat called the Talon a pickle fork tunnel hull.This boat fly's over the water not in it. it lifts on the air trap between the hulls and rides on very small surface .70 mph with a 1/8th inch of ice was a cold but short ride to the oyster beds. 1 and only ride in it.
    I plan something to transfer this effect to my plane with a like configuration skiing on narrow outboard hull with a proper concave tunnel rather than a boat hull.
    Your comments and contributions to the problem will be well appreciated .confirming or descending views.
    Regards Norm

  2. #2
    Dana's Avatar
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    Once a boat (or seaplane hull) is up and planing, the drag is very low. The maximum power is needed just before it gets up to planing speed. Until a hull is planing its speed is limited by its "hull speed", which is proportional to the waterline length (google it). Seaplanes have the added requirement for the aircraft to be able to change its pitch while planing, thus the step in all seaplane hulls.

    If you've been test flying your plane in calm conditions, that could be an issue. It can be difficult to get a plane "unstuck" from glassy smooth water; under such conditions pilots sometimes have to circle the lake a few times to make enough waves to bounce the plane loose.

  3. #3

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    Thank you Dana
    I think I am trying to break the glass .To say I mean to break traditional conceptual belief that the boat has to fly without being a flying hull like this Talon tunnel hull. there are hulls that fly they are also boats, but no aircraft I have seen use them. http://www.youtube.com/watch?v=yWx3CCLnbtU Rotation is not absolutely necessary. I can assure you a U/L is light enough to just lift off as soon as flying speed is reached and rotation to altitude after. That is in fact is how I get my plane up because I can not rotate enough the rearward sponsons a very limiting. And the flare on return is so slight it takes practice .But when done correct you can not believe you are back on the water. I am looking for insight if anyone has evidence to this. If I were to place 1 more degree of incidence wing to hull It would just lift off. Why then could not the hull also just fly off . with all this what a fine machine it would be to fly.

    I contend that what you refer to is needed to get large heavy aircraft out of the water .But may and I say may not be so for the U/L we just all assume that to be so.
    What I have so far experienced with my plane leads me to this conclusion. I guess I have to prove it if none can shed light this way.
    Last edited by Norman Langlois; 03-17-2013 at 07:07 PM.

  4. #4
    Dana's Avatar
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    If your plane is at an AOA sufficient to lift off before you actually rotate, that means there's more drag before that point, so your takeoff run will be longer. The step [I think] also reduces drag because once it's planing, the aft end of the hull isn't in the water any more. On a boat this would be problematic due to the lack of pitch stability, but in a plane you have pitch control.

    On the pickle fork hydros, it's like the front half of a stepped pontoon, and the propeller supports the aft end of the boat.

  5. #5
    hogheadv2's Avatar
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    The Talon also has the forward acting force below c/g giving a strong tendency to have nose lift. This captures a cushion of air under the deck to maintain minimum water contact and still have some control. Here is a hi speed cat that is longer, less nose lift with several times more power. http://youtu.be/a4dy_yEBIU4 The idea is not to lift off, that's always bad with boats, just skirt the edge of bad Now if I read and understand your start to the thread you wish to use a tunnel hull type fuselage. [A significant part of the fuselage / part of flight surface.] Please correct me if I am off the mark here. Prove me wrong with an Ultra-light but that seems to be asking a lot of lift for the diet it will be on. I would love to see it as a ELSA. The center foil could easily house the flap necessary with a seat over the vakas for less disturbed air of the lift and control surfaces. Just toughing a size out here.... 28' x 5' cord at about 5 to 6 feet above the catamaran platform. Floats, fuel. people. engine would all be at ir below c/g for docile turns and banking. http://www.youtube.com/watch?v=qTIoezhRS3g http://www.youtube.com/watch?v=eUlwAfFdAAo http://www.youtube.com/watch?v=ELp7NaefGUc I hope this has give you something to feed your brail on ..... Tom

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    thanks again. I was hoping some confirming information would come but it seems its not yet been tried to combine the two .if both can fly then proportional matching the two should be possible so that they both compliment the other .
    Tom, I am not looking to create a flying hull airplane only to compliment the wing with a flying hull. Like the Sea era but not the same way it uses a flying hull to compliment lift in flight. I intend only to create separation. with only slight rotation. 1 degree.

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    =Norman Langlois;28607]thanks again. I was hoping some confirming information would come but it seems its not yet been tried to combine the two .if both can fly then proportional matching the two should be possible so that they both compliment the other .
    Tom, I am not looking to create a flying hull airplane only to compliment the wing with a flying hull. Like the Sea era but not the same way it uses a flying hull to compliment lift in flight. I intend only to create separation. with only slight rotation. 1 degree.
    I think you are choosing to ignore history...

    Seaplanes have been around since Glen Curtis in 1911 - LINK

    Their designs have matured and all these things that have proven impractical have settled on the bottom of a lake somewhere...

    If you look through history you see skids, hydrofoils, various step configurations, etc. Many, many things have been tried but in the end only the practical survive...

    This is not to say one should ever stop looking or revisit past experiments. Just be prepared for failure

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    I should retract my comments about the step and rotation. So consider it retracted it was wrong for me to make such conclusions. Even about my craft.

    Jim as for ignoring history Not exactly I may not be thorough in my research for drawing a conclusion. As you state the evolution weeds out the poor designs .

    The U/L is liken to an early aircraft. The biggest difference is those could be improved through power and weight. The U/L is limited it can not enjoy the practical.
    So it must search for overlooked methods that are not practical for the GA aircraft but would be for an U/L Since only the pilot or builder needs to be appeased through the purpose and short comings.
    Also the aircraft evolved through purpose of a very different kind mostly WAR.

  9. #9
    hogheadv2's Avatar
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    Sadly WAR is where the research dollars and unlimited leaps of imagination are funded.

  10. #10
    Flyfalcons's Avatar
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    Quote Originally Posted by Norman Langlois View Post
    I should retract my comments about the step and rotation. So consider it retracted it was wrong for me to make such conclusions. Even about my craft.

    Jim as for ignoring history Not exactly I may not be thorough in my research for drawing a conclusion. As you state the evolution weeds out the poor designs .

    The U/L is liken to an early aircraft. The biggest difference is those could be improved through power and weight. The U/L is limited it can not enjoy the practical.
    So it must search for overlooked methods that are not practical for the GA aircraft but would be for an U/L Since only the pilot or builder needs to be appeased through the purpose and short comings.
    Also the aircraft evolved through purpose of a very different kind mostly WAR.
    Actually some of the biggest leaps in piston powered aviation came in the pre-war air racing days.
    Ryan Winslow
    EAA 525529
    Stinson 108-1 "Big Red", RV-7 under construction

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