Some CAD renderings

[Justin]

I think I will not build an EZ anytime soon, except for X-Plane. I will make a bog standard one first, just to benchmark it with known performance. Then I will make an adaption with the UL 390i engine and retractable main gear. Anyway, all these kind of projects start with CAD models.

[Kent Ashton]

1 hour ago, Justin said:

I will make a bog standard one first, just to benchmark it with known performance. Then I will make an adaption with the UL 390i engine and retractable main gear.

After you eat that first Ribbestek I hope you will still have the appetite for a second.  🙂    I built a Cozy IV, then a Long-EZ.   I don't think I would have had the drive to build two Cozys or two EZs although there are guys who do multiple projects.  As a result of my experience with the Cozy, I made some changes to the EZ regarding main-gear mounts and firewall engine mounts.  I wish I had also widened the back seat about 2" but the tub I bought was already done.  I also I would have made the NG-30 nose gear box sides taller to accomodate a cover over the electric nosegear retract (to eliminate air drafts).  You can see some of those changes here  https://www.canardzone.com/forums/topic/18661-kents-long-ez-project/   

You should certainly lengthen the nose and beef up the engine mounts.  All EZs need that with the bigger engines used these days.   I used a bigger canopy similar to your pictures but I concluded later it was probably draggy and unnecessary.  Looking at your pictures, I might try to flow the turtleback shape behind the canopy into the cowls without the "pinched-in" area.

I predict that if you build a nice EZ you will be satisfied with #1.

 

[Justin]

12 hours ago, Kent Ashton said:

You should certainly lengthen the nose and beef up the engine mounts.  All EZs need that with the bigger engines used these days.   I used a bigger canopy similar to your pictures but I concluded later it was probably draggy and unnecessary.  Looking at your pictures, I might try to flow the turtleback shape behind the canopy into the cowls without the "pinched-in" area.

Hello Kent,

The UL390i is not bigger than an O-235, but is a little more powerful at 140hp. It is 4kg lighter, has a slightly smaller frontal area, and the starter ring is at the opposite end to the prop drive, so the engine cowl can fair better to a prop spinner. In my model the firewall is bog standard EZ, and I have now extended the upper engine blisters to make them fairer. I think this reduces the pinched in zone. I prefer not to affect the standard firewall. This might preserve a faster airflow over the cooling outlets (not modeled yet). I will model armpit intakes. I read about them in one of the CP leaflets. I prefer not to affect the standard firewall.

The canopy is sleeker than the standard one. It has the same height and width at the canopy frame. It fairs to the standard firewall, and at the front I took some volume out with a more sloping profile. It does have a circular section at the pilot's head, and would be a little wider there then most, but not much.

If I ever really build one I would mock up the cockpit first, to see if I would like it wider, but I used to enjoy the secure feeling of being strapped in tight fitting seats in my glider flying days.

This is a 'paper plane' that will most likely only exist in the X-Plane simulator world.

Cheers,

Justin

Edited May 30, 2020 by Justin
added one more picture

[Pez]

The UL-390 is 160hp vs the 235's 108hp (some are rated at 115hp@2800, but with a static RPM of 2400 or so, it doesn't do you much good) and you need the engine mounts beefed up not for the extra engine weight, but for the extra engine torque. A modern 390ci vs a 1940s designed 235ci torque would be pretty dramatic.

It would be wise to listen to those who have built and flown these.

Edited May 30, 2020 by Pez

[Justin]

The engine mounts always need to be engineered for the job. It is likely that the torque reaction of the UL390i is similar to the O-235, because it revs slightly higher. Other higher torque engines are already used in EZs. You just design the mount for the job. In any case the Lycoming mounts are not used with UL engines.

BTW, the UL390i is 140hp. The UL390iS makes 160hp.

I think propeller design issues are more of a concern. These are things we can investigate in simulation.

 

[jridge]

Justin-

Did you model the motor or is one available online somewhere?

 

Jeff

Edited June 1, 2020 by jridge
typo

[Justin]

Hi Jeff,

Go to the UL Power website, and on the 'manuals' page for each engine there are STP file downloads. The installation manuals are there too, and well worth reading.

https://ulpower.com/en/engines/ul390/ul390i#downloads

Justin

[jridge]

Nice!  Wish other engine manufacturers were so accommodating!

Jeff

[Pez]

On 5/30/2020 at 4:13 PM, Justin said:

The engine mounts always need to be engineered for the job. It is likely that the torque reaction of the UL390i is similar to the O-235, because it revs slightly higher. Other higher torque engines are already used in EZs. You just design the mount for the job. In any case the Lycoming mounts are not used with UL engines.

BTW, the UL390i is 140hp. The UL390iS makes 160hp.

I think propeller design issues are more of a concern. These are things we can investigate in simulation.

 

UL390i is 330NM, 0-235 is 210NM. Not exactly similar.

[Justin]

Just a few more renderings. The nose is now only 6" longer than the standard one.

I need to uprate the SSD in my computer, get back into X-Plane 11 and start on the flight model.

I might do some more CAD modeling of the real structure and cockpit components, but is has low priority right now.

 

[Royal]

That's pretty cool. Id like to get my rendering finished. We should work together.

 

[Justin]

Thanks.

Actually, I am not too bothered about renderings. I may model more for the Open EZ project, but the design data is a pretty dismal mess. I think people who have built EZs are heroes ! I am more likely to build a Sonex or Midget Mustang. Meanwhile, my EZ project may fly in X-Plane.

[Royal]

How do you get the model in X-plane?

[Justin]

X-Plane has an add-on (included) called 'Plane Maker'. You can build flight models in there, but you need to be aware of its limitations.

If you simulate your idea in X-Plane it will  not accurately represent reality. X-Plane cannot simulate the effects of the heavily swept leading edges near the roots. It simulates only chordwise airflow. All kinds of vortices above highly swept leading edges will be created with high angles of attack, and you will risk loss of pitch stability. Kent points this out with his reference to the deep stall issue, on your thread. I think the Long EZ gets away with it because the canard is unswept, and the leading edge of the Eppler 1230 inboard wing strakes are fairly blunt, but some EZs have lost control. One of the CP Leaflets has an article on deep stall. I will find it later.