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tunnels

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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.
In this type of hull 25 to 30 mph it would be wanting to be on top of the water planning as speed increases then the tunnel is compressing the air and the faster its goes the higher its will climb out and on top and at 70mph its would be literally flying !! the optimum angle of attach would be built as to the same as the planes some where in 3 to 5 degrees so everything all works together at the same time !
With this type of hull form all of the hulls bottom surfaces contribute to lifting water doesn't climb any where even inside the tunnel !! the pressure of the air is slowing gaining pressure and being compressed till it finally reaches the transom ! Yes all this has been describes more than once and still no one has spent enough time looking !

Its not a catamaran !! because cats by nature have narrow hulls they provide little in the way of lift ! because the tunnel between there hulls is much bigger and higher it also contributes almost nothing to lifting the cat so they plough through the water and ride much deeper .
Think how many racing cats are seen out on the water?? non at all ,because they are not the same as a tunnel , they are slower and DO NOT PERFORM WELL!!!
 

bmcj

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Perhaps the way to make a tunnel truly effective is to have a drooped trailing edge (to act as an apron) and to blow air underneath. I have seen a few designs that make use of this idea, including hovercrafts and one of the giant Russian Ekranoplanes which had a small beam of jet engines on the nose that could rotate to direct the blast beneath the primary wing.
 
M

Manticore

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... and at 70mph its would be literally flying !!
So now you are claiming that it actually *is* an Ekranoplan. Well there are better ways to do that too.
images.duckduckgo.com.jpeg
Role Ekranoplan
Manufacturer Central Hydrofoil Design Bureau
Designer Rostislav Evgenievich Alexeev
First flight October 16, 1966
Status sunk in 1980
Number built 1
540 tonnes, 400km/h.
 

tunnels

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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).
man alive are you confused !!
 

tunnels

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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.
The cut always on each side are a bad choice as that part of the two hull halves is totally necessary!
you completely missed the point of how a tunnel works and putting a foil in between the two hull halves makes it even more efficient!
 

BJC

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Mr. tunnels:

If you are correct, and all existing, proven float designs are poor performers, and you know how to "get out of the box" and design and build much better floats, then why aren't you?

It could make you wealthy.


BJC
 

Starjumper7

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The thing about that foil wing between the hulls is that those were created for big old things like tugboats and speedboats with no power and no speed !! That kind of foil has to stay underwater because if it comes to the surface the drag is huge !! Like I said before !! That in combination with the suckyrocker bottom will prevent takeoff !! You need surface piercing foils, which are shaped like the bow of a boat, and look like a shortened pontoon back to the step !! Like I said before !! ... unless you are planning on having 800 hp or so !!

... and here I assumed this was all about making it easier to take off !! Yaaahahahaha !!

Tunnels, do you ever draw sketches or drawings or make models !!

With three or four surface piercing hydrofoils you can establish your takeoff attitude if you are afraid of rotating by yourself !! If you (not Tunnels) are OK with taking off all by yourself then only two or one surface piercing hydrofoils (read steps) are needed !!


edit: just kidding, the tunnel will help lift your thing, whatever that is, out of the water. a little, at great cost, if you have lots of extra power ...

!!!
 
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tunnels

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The thing about that foil wing between the hulls is that those were created for big old things like tugboats and speedboats with no power and no speed !! That kind of foil has to stay underwater because if it comes to the surface the drag is huge !! Like I said before !! That in combination with the suckyrocker bottom will prevent takeoff !! You need surface piercing foils, which are shaped like the bow of a boat, and look like a shortened pontoon back to the step !! Like I said before !! ... unless you are planning on having 800 hp or so !!

... and here I assumed this was all about making it easier to take off !! Yaaahahahaha !!

Tunnels, do you ever draw sketches or drawings or make models !!

With three or four surface piercing hydrofoils you can establish your takeoff attitude if you are afraid of rotating by yourself !! If you (not Tunnels) are OK with taking off all by yourself then only two or one surface piercing hydrofoils (read steps) are needed !!


edit: just kidding, the tunnel will help lift your thing, whatever that is, out of the water. a little, at great cost, if you have lots of extra power ...

!!!
wow !! do we live on the same planet ??
 

tunnels

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Mr. tunnels:

If you are correct, and all existing, proven float designs are poor performers, and you know how to "get out of the box" and design and build much better floats, then why aren't you?

It could make you wealthy.


BJC
Its the main body of a amphibious plane as in the boat hull , not floats that are attached on legs as I envisage you are referring to
 

TinBender

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Tunnels,

Since we have not seen any drawings, please forgive our lack of understanding. Are you proposing an aircraft similar to a Top Fuel Drag-boat with wings?

Dragboats_SLDBA_Litchfield_IMGP7465f.jpg
 

Dan Thomas

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Tunnels,

Since we have not seen any drawings, please forgive our lack of understanding. Are you proposing an aircraft similar to a Top Fuel Drag-boat with wings?

View attachment 43589
More likely something like the Flightsail homebuilt of 50 years ago. Basically a tunnel hull, with a proper step, but still a poor performer which is why we never did see more than a handful of them.

335-2.jpg

There is very little new under the sun.
 
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Tiger Tim

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That Flightsail is quite the interesting machine. I picture it sitting three or four across on some big cushy couch with seatbelts...
 

Starjumper7

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This plane could have pontoons on the lower wing in order to make it into a tunnel hull. Using pontoons shaped like those on a hydroplane would make it a nice wide tunnel hull, the best kind.

The DO - 24 TT

c0c17a86d0b6727ccc62781d9561a1c4.jpg 43589d1443567786-here-we-go-again-dragboats_sldba_litchfield_imgp7465f.jpg
 

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Topaz

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Moderator Note: Just deleted a seriously off-color post. Remember, folks, we have minors regularly visiting this site. This isn't the bar or locker room. Please post with that in mind.
 
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