Re: COZY: Is anyone currently operating off a grass strip with a cozy MK IV

tfdarden
 

Michael, thats’s awesome, what a wonderful analysis of a different type of hybrid power!  Thanks for posting it. 

Thomas F Darden

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On Jul 25, 2020, at 10:18 PM, Michael Arndt <mike.arndt.ie@...> wrote:


With regards to grass strips I've had similar thoughts - how great would it be to base your plane closer to home?

What follows is the results of my discussions with Dr. John Loth of WVU, and some of my own thoughts on how to solve this problem.

I've been a big fan of Circulation Control (CC) for years because of its ability to take a clean, fast aircraft and land it slowly like a bush plane with balloon tires. Unfortunately when I started working this problem working this problem back in 2003 the only way to drive air over the wing was to tow the whole air frame through the air, or install a complicated/heavy system with an alternative power source to do the job for you. Dr. Loth used that approach for his Navy work in the 1970s, and he was kind enough to upload this old video of the results. Loth put a small jet engine in the back two seats of a four seater and used it to blow air through a retractable tube in the trailing edge of the wing, and it worked. His approach speeds got into the low 30s during testing without affecting the curse and top speeds of the aircraft.

Unfortunately my dream aircraft has always been a canard (as Rutan never published the plans for the Catbird - 5 seats,30 knots faster using the same engine), and the prospect of giving up half the seats was already unappealing even before you get to the issue of using CC on a canard.

But then lithium battery technology came along. And it got more widespread and cheaper. Lilium in the UK designed what is basically and electric Cozy that takes off and lands vertically by using CC propulsion on the flaps. Nasa began work on the X-57, a design that uses a tiny curse optimized wing with span wise propellers to handle takeoff and landings. All this got me thinking about whether this approach could be adapted to our aircraft, not for full electric flight, but for two minutes of run time at takeoff and landing...

The Cozy requires about 50 HP to maintain altitude and not sink, all other things being equal. That's about 38 K watts. If we use that as our target it would take twenty 2000 watt RC aircraft motors to produce enough thrust to hold altitude, but I'm thinking about STOL uses here. If you purchased 20 RC motors, each with a battery pack to drive them, they could be mounted in small two inch tubes on the leading edge of the wing and fitted with fold back RC glider propellers. Because the power packs are independent there is no need for thick heavy wiring, just a thin charging cable for in flight recharging and an on/off switch. 

It would be necessary to test it at a safe altitude first and to match the correct proportion of thrust to the canard to maintain its 'stall first' property, but fundamentally this is a much easier job than what Lilium or the X-57 are doing. Once operational, grass strips would suddenly be an option because takeoff speed with the system on would be under 30 mph. Having a two minute run time would allow plenty of safety factor, and allow use of small, light, off the shelf RC batteries. After all, most remote control aircraft run for a lot longer than two minutes.        

Sure it's wild, but for the first time lithium ion batteries have made it possible. : )



On Sat, Jul 25, 2020 at 5:19 PM Craig Westwood <craig.westwood@...> wrote:
There is only one grass strip I would consider, and that is Triple Tree Aerodrome in South Carolina (SC00).  It's 7000' x 400' and like a golf fairway.  That said, I know a Long-Ez (O-235) pilot that went over there and vowed never again as he thought he wasn't gonna get off the ground.  He did, and with plenty of room as beyond the hump in the runway there's another ~2000'.  A Cozy at higher weight and a forward CG is gonna need a lot of runway on grass.

Craig

On Sat, Jul 25, 2020 at 5:08 PM Bill Allen <billallensworld@...> wrote:
In ‘Yurp, where we have smaller and costlier everything, people are forced to use grass where there isn’t a blacktop airfield nearby courtesy WW2.
I don't know of anyone using grass with a Cozy Mk4, but I do know of one Cozy Classic which used to operate off grass, and the owner installed a larger nosewheel for this.
I have flown my LongEz off grass once, but it was a billiard smoooth grass runway.
 
Here’s a youtube video of Stefano Ferretti landing his VariEze on his Homebase grass runway in Italy.

Graham Singleton modified his LongEz to operate off grass by installing the nosegear 1” forward of plans location to encourage earlier rotation.

If you’re going to operate off grass, you have to know your own grass airfield intimately, and as others have said, watch out for rabbit holes, ruts, boggy patches etc. You have to have driven or walked it, talked to locals who know where the bumps are etc etc.

The other big disadvantage our aircraft have is the “pogo-stick” nose spring. That can get in phase with bumps and pitch you over. Stefano (in the above video) fitted a modified MTB damper to cope with this. I have made a few of my own versions and Ken McConnell (VariEze) has been testing it, and is very pleased with it. However, It only works with the manual retract mechanism.

So, grass might work if you set your aircraft up for it, if the grass was smooth, short, dry and well maintained (ie; like blacktop) but otherwise, keep to the black stuff.

Bill Allen

On Sat, 25 Jul 2020 at 22:09, Buly <bulent.enginegear@...> wrote:
As Vance said,
I did hear from the buyer, complaining that by the time he gets to take off line, the engine overheats. He wandered why? 🙄 I explained to him that taxiing at high power in the grass, with minimal forward motion, the engine has no way to shed the extra heat.
Than he asked how come the nose dives down too much on takeoff roll?
Again, the small nose wheel boggs down in the grass and  the thrust of the engine pushes the nose down I told him. Than he altered the NG strut.
I was very much against him flying from the grass strip, but the doctor was persistent. What do I know?


On Sat, Jul 25, 2020 at 11:16 AM vance atkinson <nostromo56@...> wrote:
About a year or so ago a doctor bought Bulent Aliev's very nice Cozy 4 that was based in Florida.  I ferried it to Houston TX for Buly and checked out the owner, who had no experience in EZ types but was very current in Cherokee he owned.

 He had a house on a grass field and wanted to base it there.  I checked him out on hard surfaces and told him about the perils of grass field Ops.  He went ahead anyway. 

Haven't heard how he fared but months later, did see a picture that Buly sent me of the plane sporting a brand new aluminum nose gear strut.  Looked like it was milled out of a solid billet and it looked really nice... and probably cost a small fortune.

You can reach Buly at  <bulent.enginegear@...> He may have more info relative to how the Doctors machine is doing.
Vance Atkinson








On 7/25/2020 10:13 AM, 'Phil Kriley' via COZY Builders Mailing List wrote:
I avoid grass even for taxiing if at all possible and would never consider landing/taking off from grass.  Beats the hell out of landing gear and wheel pants.  Damaged my wheel pants at OSH and at Rough River.

Phil Kriley

On Jul 25, 2020, at 8:44 AM, hnf.flyboy via COZY Builders Mailing List <cozy_builders@...> wrote:

I have 30 years of grass experience.  None of it in a canard.  I would love to use grass for my plane when finished.  I won't - unless I know it's a long and expertly maintained daily.  Armadillos leave terrible holes, can't imagine what happens to our nose gear when you hit one.  There are also moles which leave their mole hills as mountains if you don't see them in time.  I know of a grass strip at Leeward air ranch in Ocala,  It's the only one I'd use - but haven't seen it in years.  Used to have a few canards there.  

Everyone I talk to recommends against it, including Marc a couple weeks ago. 


-----Original Message-----
From: Steven Scott <chiefpilot.qp@...>
To: COZY Builders Mailing List <cozy_builders@...>
Sent: Fri, Jul 24, 2020 9:49 pm
Subject: COZY: Is anyone currently operating off a grass strip with a cozy MK IV

I am looking to buy land at an Airpark in Florida. I need some first hand knowledge and experience of what I need from a grass runway. Length, condition etc.....

I am inspired by Del Shier who has shared his Airpark experience with me. His runway is paved. I need someone with grass experience.

Steven Scott
N541EX
San Diego but getting the hell outta California........

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Bulent Aliev
Enginegear
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fax +1 386.957.4473
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