HERE WE GO AGAIN !

[Tiger Tim]

Conventional seaplane hulls are kind of interesting in their step design and placement effectively making them two hulls (for a high speed and low speed regime). I wonder how this requirement would shape a tunnel hull designed for aviation.

 

[Starman]

Like this, only as a hull split in half by a tunnel. This is similar to a wide aircraft pontoon.

 

[Starman]

Thread drift

http://cdn.hiconsumption.com/wp-content/uploads/2014/09/Kormaran-Concept-Luxury-Convertible-Boat-1.jpg

 

[Starman]

 

[tunnels]

View attachment 43499

Please take careful note that is a catamaran design NOT A TUNNEL !! AND THE CENTRE FOIL is the only thing needed for what I want to do the two small rear side foils are not required !
Remember what I said cats are not tunnels and even really bad tunnels are a 100% better than what people call a good cat !!

 

[Starman]

I'm aware of the difference between a tunnel hull and a catamaran, I only thought that photo was of a cool cat.

Reference the last link I posted, it shows the foil, which could be at the very bottom of the hull, has already been invented and patented. You don't need foils at the back because the back hull planing surface serves that purpose well enough at higher speeds. The hulls would still benefit from a step like I showed because it will help the hulls get unstuck from the water quicker.

 

[tunnels]

I'm aware of the difference between a tunnel hull and a catamaran, I only thought that photo was of a cool cat, just checking to see if you are paying attention, as so few do.

Reference the last link I posted, it shows the foil, which could be at the very bottom of the hull, has already been invented and patented. You don't need foils at the back because the back hull planing surface serves that purpose well enough at higher speeds. The hulls would still benefit from a step like I showed because it will help the hulls get unstuck from the water quicker.

Instead of using "THE STEP" that everyone can relate to "it is not required" !! it would be replaced by the introduction of rocker shape in the hulls bottom !!The placement of the rocker is the key to the steps replacement !! The rocker would have another advantage also of a bad slightly nose down landing it would have the benefit of sucking the aft end of the hull down and self levelling the plane .
Like I mentioned and spoke of long time back hands free take offs and hands free landing are my aim !
safety is top of my priority list always .

 

[tunnels]

Tell me what does the step really do ??
why is it used ??
and what would happen if it wasn't used??
In the boating industry steps cause way more problems than they ever solve !!

 

[BJC]

Tell me what does the step really do ??
why is it used ??
and what would happen if it wasn't used??
In the boating industry steps cause way more problems than they ever solve !!

Yup, that is why flying boats and aircraft pontoons use them; they cause more problems than they solve.

The step evolved through much experimentation to find a way to reduce hydrodynamic drag and to enable the airplane to rotate and break hydrodynamic suction.

Still waiting to see your "out of the box" improved design.

You might want to do a little research, and then think a little, before posting more comments.


BJC

 

[Starman]

.. it would have the benefit of sucking the aft end of the hull down ...

Do you suppose all this sucking might make it difficult to take off? Yaaahahahaha

 

[tunnels]

Yup, that is why flying boats and aircraft pontoons use them; they cause more problems than they solve.

The step evolved through much experimentation to find a way to reduce hydrodynamic drag and to enable the airplane to rotate and break hydrodynamic suction.

Still waiting to see your "out of the box" improved design.

You might want to do a little research, and then think a little, before posting more comments.


BJC

very good !!
So in actual fact the end or transom of the boat hull could have been finished at that point and so a step would not have been required but its aerodynamics and smooth flowing lines that are needed and a blunt cut off would have caused masses of amount of turbulence from that point plus they needed a little more buoyancy aft as well .
Steps are not needed on tunnel boats!! do you know why they serve very little purpose ??

 

[tunnels]

Do you suppose all this sucking might make it difficult to take off? Yaaahahahaha

no not at all!! the rocker is used to rotate the plane into the right position for take off !!
Its the placement and the shape of the rocker that's the key that you are missing seeing !!
Rocker is something that's very useful and if used to its best advantage can make a hull spin and go round corners very quickly and not drop any speed !! !In this case its going to be used for soft landings !! and smooth quick take offs and not have to lay a hand on the controls ! Just the throttle that's all !!

 

[bmcj]

Regarding tunnel-hull vs stepped floats, I suspect the tunnel-hull could be considered a stepped platform... once the center hull breaks from the water, the pontoons (or whatever you choose to call them) represent a smaller contact surface, similar to the reduction of contact surface when a float gets up on the step.

Still I suspect that the step on a conventional float allows an easy breakaway point for the water. Otherwise, the water would just try to stay attached and follow the float tail, causing added drag and contact suction. In that respect, the tunnel-hull pontoons would probably benefit from a step, even if the step is in the form of a flat transom at the aft end (trim the pontoon length as needed for proper balance on the step).

 

[Dan Thomas]

Without a step, the water just tries to climb any rocker in the hull, pulling it down. Just try to tow a canoe behind your boat at any speed; it will tuck its tail deep into the water and stick its nose up. Terrific drag. too, limiting acceleration.

An airplane's floats are designed to leave the water. A boat's hull is not. This is a crucial difference that a builder ignores at his own peril.

 

[BJC]

Haven't we already had this thread three or four times?


BJC

 

[Starman]

I think someone has tunnel vision.

 

[Himat]

Its the tunnel between the hulls that's the key !! You are missing the point !! the hulls lift the boat at low speeds and when the speed gets to 50 mph plus then the air starts to take over and lift even more and so speed increases very quickly ! 70 to 80 mph and significantly the air had a lot of lift not only under the boat but also the vast existent of deck area produces quite a bit of lift as well !! To design a stable fast boat first you have to choose a foil to work with then superimpose the boat over the top retaining as much of the actual foil shape for the underside (tunnel roof ) and the upper parts as well !! simply it has to fly !!
No the boat in the picture was after time working with Scott but its the copy of a boat I wanted to make myself !!
If the boats wont reach 70mph plus I wasn't interested !!speed on water is something else !!

As have been pointed out, 70mph is above take of speed for many light airplanes. The stall speed requirement of an Light Sport Airplane is 52mph, typical takeoff speed is somewhat higher, but still less than your 70mph boat hull. At 70mhp the airplane is wing borne and flying, and the hull is out of the water.

At 50mhp the wing carries about half the aircraft weight depending on the actual take of speed, if your tunnel hull first start providing substantial lift at 50mph it is maybe at a to high speed. The hull lift is maybe more need at lower speed.

 

[Starjumper7]

OK, beat this. The pontoons are minimized and cut away, and the arrow is pointing to a skirt which traps air under the tunnel, filling in the cutaway parts of the hulls. Flotation is mainly from the tunnel itself when at rest.

 

[bmcj]

Two members from Ecuador with similar names? Starjumper 7 and Starman (whom I think lives in Ecuador too).

 

[Starman]

Name change operation