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Pattern Plane With Dorsal And Ventral Fins

Old 12-12-2010, 11:06 AM
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DT56
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Default Pattern Plane With Dorsal And Ventral Fins

I've been searching for more information on a pattern plane of unusual configuration that I read of approximately 15 years ago. The model had low aspect ratio dorsal and ventral "fins" located about the aerodynamic center. The vertical stabilizer area was divided equally above and below the fuselage centerline. I believe the designer / builder may have been from Louisiana.

Anyone have a lead on the identification of this model?

Thanks!!!

This slope model is of approximately the same configuration.
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Old 12-12-2010, 11:26 AM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

DT56

Nat Penton was the designer builder

Had a number of designs from Voodo to Voodo Express.

Dick
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Old 12-12-2010, 12:03 PM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

Here's a Voodoo Express I built this year from plans I got from Mark Hunt.
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Old 12-12-2010, 03:22 PM
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DT56
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Default RE: Pattern Plane With Dorsal And Ventral Fins

Thanks guys, I really appreciate it!!!
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Old 12-13-2010, 12:58 AM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

Very interesting concept.

How does it fly (i.e. knife edge, roll, cross wind handling)compared to a "normal" plane of that size without the fins?

Just wondering - The power version makes sense but the slope soarer in 1st postmay side slip in cross wind on a slope.If this powered concept makes a big difference, why don't we see more ofthese type planes around?

Except for "foamies" etc, I've seen some planes with "canard " wings and "stall strakes" but not with these extended vertical fins.

Bundu
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Old 12-13-2010, 08:34 AM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

ORIGINAL: Bundubasher
...
Just wondering - The power version makes sense but the slope soarer in 1st post may side slip in cross wind on a slope. If this powered concept makes a big difference, why don't we see more of these type planes around?
...
There is a segment in the slope scene associated with a Europen term "VTPR" which involves low and slow aerobatics on a hill which provides the right kind of lift where penetration isn't a big issue. For that concept, broad "fish like" fuselages work well, and allow a flyer to spend more time off the (main) wing.

Here's a good explanatory thread:

http://www.rcgroups.com/forums/showt...130761&page=30

As a power flyer (who's used to much better and crisper yaw control), VTPR isn't really my cup of tea, but it does offer another slant on waking up your left thumb on the slope.

Joe
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Old 12-13-2010, 09:43 AM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

Hello,

Here is mine:



The construction:

http://www.rcuniverse.com/forum/m_9749764/tm.htm

It's realy a nice pattern plane! In particular with the electric propulsion.
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Old 12-13-2010, 09:52 AM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

We don't see more of this type of planes around because, according to the general opinion, this plane is not fashionable. It's not my point of view, but I can tell that the first reaction when you arrive at the flying field with this plane is: "Beurk, it's horrible". After this first reaction, people are amazed by the flying qualities. But it's only the second reaction...
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Old 12-13-2010, 10:00 AM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

Thanks guys, this is most interesting. I'm keen on giving this a try.
I've got a modified Mirage (Cheetah) with canards etc, but all these mods are only horizotally orientated. Just shows one can learn always something new... even after 40 years.

Just a question - would you place these dorsal fins at the same cg point as the main wing or does it not matter too much?

Thanks

Bundu
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Old 12-13-2010, 10:09 AM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

Yes the cg of the dorsal fins and the cg of the main wing are the same.
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Old 12-13-2010, 11:25 PM
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Default RE: Pattern Plane With Dorsal And Ventral Fins


ORIGINAL: Bundubasher

Very interesting concept.

How does it fly (i.e. knife edge, roll, cross wind handling) compared to a ''normal'' plane of that size without the fins?

Just wondering - The power version makes sense but the slope soarer in 1st post may side slip in cross wind on a slope. If this powered concept makes a big difference, why don't we see more of these type planes around?

Except for ''foamies'' etc, I've seen some planes with ''canard '' wings and ''stall strakes'' but not with these extended vertical fins.

Bundu
Here's a video of the sloper in action.

http://www.vimeo.com/17705369
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Old 12-14-2010, 04:09 AM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

wow, if there ever was a soarer to keep me interested, that'd probably be it.

Even though I live in one of the windiest cities in the world, we just don't have good enough sloping hills!
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Old 12-14-2010, 10:28 AM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

Pattern slope soaring... Now that would be interesting and pretty cool too.

ORIGINAL: Rendegade

wow, if there ever was a soarer to keep me interested, that'd probably be it.

Even though I live in one of the windiest cities in the world, we just don't have good enough sloping hills!
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Old 12-14-2010, 03:36 PM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

Something tells me we'd get pretty tired of the weak verticals very quick.
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Old 12-14-2010, 03:50 PM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

ORIGINAL: Rendegade

Something tells me we'd get pretty tired of the weak verticals very quick.
Not on a good hill on a good day. The really amazing thing about flying slope pattern on a good hill is the "terminal velocity" on a really clean and capable slope plane is MUCH faster than what you'd dare to do with most powered pattern birds. The name of the game in modern pattern is "constant speed". Slope pattern is much more reminiscent of old time "ballistic pattern" except you really can use your energy much more efficiently than the old thick winged chariots we know and love. Combine that with being ON TOP of a really big cliff, and you can dive repeatedly at yourself at very high speed so you can hear everything as you streak by, and then carve super big and fast valley filling loops== flying below your feet for a long time until you use up your energy and come back for more. On the really big hills, it feels like the entire sky is rising, so you can really just put your plane anywhere you desire, a true "cursor in the sky" == just like a pattern flyer would want.

When you fly a really fast heavy bird like that, there is a rule which you learn pretty fast == What comes down, must go UP! That means you've got a lot of energy to play with after each dive, and it's up to you to decide where to spend it all. Like I said, on a really good hill on a good day, you really won't miss having a motor if you just want to fly patterns.

It's when you want to do multiple snaps, successive spin recoveries, extended KE maneuvers (any type of energy killing move), or any real 3D stuff that the slope falls short. But for max speed and adrenaline, the sheer size of the maneuvers, and breathtaking places to fly, it's still among my favorite ways to spend a few hours (or weeks!)
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Old 12-15-2010, 02:41 AM
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Default RE: Pattern Plane With Dorsal And Ventral Fins


ORIGINAL: Bundubasher

Just a question - would you place these dorsal fins at the same cg point as the main wing or does it not matter too much?

Thanks

Bundu
You have to place the fins matching the Aerodinamic center of the fin with the CoG of the plane; otherwise you'll get an extra moment around the yaw axis...
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Old 12-16-2010, 04:47 AM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

You have to place the fins matching the Aerodinamic center of the fin with the CoG of the plane; otherwise you'll get an extra moment around the yaw axis...
But then again, all the T-canalisers I have seen have been mounted behind the C of G, and their purpose is to an extent the same as these Dorsal and Ventral Fins.
The aerodynamic centre of pressure is normally not the same whether the model is flying the right way up or in knife edge. Is it not the location of the TOTAL aerodynamic centre of pressure that matters, including all the stick-on bits?
Magne
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Old 12-16-2010, 05:40 AM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

ORIGINAL: Magne

You have to place the fins matching the Aerodinamic center of the fin with the CoG of the plane; otherwise you'll get an extra moment around the yaw axis...
But then again, all the T-canalisers I have seen have been mounted behind the C of G, and their purpose is to an extent the same as these Dorsal and Ventral Fins.
The aerodynamic centre of pressure is normally not the same whether the model is flying the right way up or in knife edge. Is it not the location of the TOTAL aerodynamic centre of pressure that matters, including all the stick-on bits?
Magne
I think I see what you're saying. Having the fins away from the aerodynamic centre isn't necessarilly a bad thing. Just think of the stab or fin, the moment they produce is used to counter other moments and add stability. But these fins are designed to add lift in knife-edge, not for stability. By having them on the CoG they won't change the attitude (yaw) of the aircraft at different fin angles of attack (sideslip angles). All they do is add lift.

By having them say behind the CoG, you're actually adding in a sense to the size of the fin at the rear of the aircraft as it's adding stability as well as side area. In fact, if you were to put these fins far behind the CoG, so that the moment they produce during a side slip is large, you would have to increase the size of the rudder or it's throw. This is because the rudder will have to 'fight' the extra stability provided by the fins, which may be counter-productive for pattern.
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Old 12-16-2010, 05:50 AM
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Default RE: Pattern Plane With Dorsal And Ventral Fins


ORIGINAL: robert

I think I see what you're saying. Having the fins away from the aerodynamic centre isn't necessarilly a bad thing. Just think of the stab or fin, the moment they produce is used to counter other moments and add stability. But these fins are designed to add lift in knife-edge, not for stability. By having them on the CoG they won't change the attitude (yaw) of the aircraft at different fin angles of attack (sideslip angles). All they do is add lift.
Yes!!!!!

ORIGINAL: robert
By having them say behind the CoG, you're actually adding in a sense to the size of the fin at the rear of the aircraft as it's adding stability as well as side area. In fact, if you were to put these fins far behind the CoG, so that the moment they produce during a side slip is large, you would have to increase the size of the rudder or it's throw. This is because the rudder will have to 'fight' the extra stability provided by the fins, which may be counter-productive for pattern.
By having them say behind the CoG, you're actually adding in a sense to the size of the fin at the rear of the aircraft as it's adding stability.
But it's not necessarily an advantege... may be for one flight condition; but could be even dangerous for others...
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Old 12-16-2010, 07:59 PM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

Here's mine:
Slightly different fuselage but same concept with the vertical fins. Also inspired by Nat Penton and Mark Hunt and with the help of many others (Rusty Dose, Jim Sheffield, Richard Lewis, to name a few.)


-Chris
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Old 12-25-2010, 10:21 AM
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Default RE: Pattern Plane With Dorsal And Ventral Fins

Chris,

Your GT Express is realy nice!
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