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Berkut v. Cozy


johnpalex
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I was told by someone that the Berkut has a higher airspeed than the Cozy. Does anyone know for sure?

Lots of people know for sure.

 

Yes, the Berkut is faster than the COZY.

 

Has anyone applied Berkut type wings on a Cozy to get greater airspeed?

The Berkut type wings are essentially identical aerodynamically to the COZY type wings. The Berkut is faster because it's a smaller aircraft with retractable gear with a larger engine. There's no magic.
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Lots of people know for sure.

 

Yes, the Berkut is faster than the COZY.

 

The Berkut type wings are essentially identical aerodynamically to the COZY type wings. The Berkut is faster because it's a smaller aircraft with retractable gear with a larger engine. There's no magic.

It's essentially identical to the wing on the original Cozy and the Long EZ. The Cozy 4 wing is larger.

 

The differences between the Berkut wing and the Cozy wing are tiny. Bigger ailerons, a straight trailing edge (got rid of the kink at BL 55.5) and winglets tipped out just a touch - just for looks.

 

Mark's right. Bigger engine, smaller fuselage, retractable gear, slicker cowl, lighter empty weight. No magic.

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  • 2 months later...

It's essentially identical to the wing on the original Cozy and the Long EZ. The Cozy 4 wing is larger.

 

The differences between the Berkut wing and the Cozy wing are tiny. Bigger ailerons, a straight trailing edge (got rid of the kink at BL 55.5) and winglets tipped out just a touch - just for looks.

 

Mark's right. Bigger engine, smaller fuselage, retractable gear, slicker cowl, lighter empty weight. No magic.

Ronnenberg's Berkut was parked next to my Long-EZ at Columbia CA. In addition to no lower winglets, it appeared that the upper winglets were a few inches shorter as well (maybe 3"?).

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Ronnenberg's Berkut was parked next to my Long-EZ at Columbia CA. In addition to no lower winglets, it appeared that the upper winglets were a few inches shorter as well (maybe 3"?).

Yep. Error when making the molds. The foam wing versions have winglets the same size as the EZ.

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  • 4 months later...

Further to this thread, I understand that the Berkut strake uses a convex upper surface. What affect, if any, does this have on comparative performance (Longeze, Cozy, and Berkut), eg. greater lift at low airspeed?

 

Don't know. The decision to curve the upper strake was part aesthetic, part rule of thumb, part wild guess.

 

Basically Dave figured that since it was out in the wind it should be lifting, so he cambered it. Of course, a flat surface with a round nose and a pointy tail will generate lift too, but the camber looked good, and it might have the effect of moving the CL aft. Since he'd just lost his Long EZ in an aft CG deep stall, moving CL aft seemed like a good thing.

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The Berkut is faster because it's a smaller aircraft with retractable gear with a larger engine. There's no magic.

Was there anything done on the Berkut to give it greater strength to handle the larger weight and thrust of a larger engine? :confused: What is to stop one from putting the larger engine on the Cozy? I know there is a group of people that don't like messing with the plans but I am just asking and I don't even have plans yet. :sad:

Barry Walker

 

Saving for a set of Cozy MKIV plans/kit and large "shed" (in that order). If I don't have the plans and start building when the "shed" is done, my wife will find another use for the "empty" space!

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Was there anything done on the Berkut to give it greater strength to handle the larger weight and thrust of a larger engine? :confused: What is to stop one from putting the larger engine on the Cozy? I know there is a group of people that don't like messing with the plans but I am just asking and I don't even have plans yet. :sad:

You mean, other than changing all the flying surfaces and sparcaps to carbon, vacuum bagging everything, using higher density core and a completely different engine mount and mounting system?

 

Nothing.

 

There's a 540 retract Cozy flying, and a supercharged 540 E racer. The identified weak points right now are 1) Rudder flutter (add a Gurney flap to get some more in force at high speed and it's fine) 2) Canopy thickness (I wouldn't want to hit a duck at 240 kts) and 3) running out of nose down trim at high speed.

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You mean, other than changing all the flying surfaces and sparcaps to carbon, vacuum bagging everything, using higher density core and a completely different engine mount and mounting system?

 

Nothing.

Doesn't sound like nothing to me! :( It does sound like fun though! ;)

Barry Walker

 

Saving for a set of Cozy MKIV plans/kit and large "shed" (in that order). If I don't have the plans and start building when the "shed" is done, my wife will find another use for the "empty" space!

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  • 1 month later...

Nathan, Richard,

 

any leads on where I could find more information on the 540 EZ, and what mod's were done to it to carry the extra weight? I know that lengthening the nose achieves some compensation, but as for how to estimate that, Im not too sure (is it just the W&B calc's? Marc, any advice would be appreciated).

I've also heard of a direct drive V8 in a LongEz some years back, much the same mod's would have been required I assume.

Does anyone know whether there were corresponding changes to the size of the longeron material or any of the lay-ups to provide the required support for the larger (vibtating) 540?

 

Richard, I know the early Berkuts had foam core wings, wasn't that the same 2lb foam, just with more dense foam skins on the strakes?

 

My thanks in advance,

 

Bruce.

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Berkut wings were 2 lb foam, but carbon skins (4.7 oz/yd uni) and three plies on both top and bottom - +30, -30 and spanwise. Also carbon fiber sparcaps and the shear web was increased from 6 plies to 8. And the solid core foam wings were vacuum bagged at about 12-15" of mercury.

 

The 1' fuselage stretch, a long nose (battery in front of the nose bulkhead) electric nose gear, and a short as possible engine mount made the CG come out about right.

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  • 4 weeks later...

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