Long-EZ efficiency optimization.

[Grace]

I'm trying to figure out what the best way to increase the fuel economy I can get from a Long-EZ is, and the obvious solutions (that come to mind for me) are 1. lowering weight, 2. using a more efficient engine, 3. variable pitch propellers.

I'm not confident that I could lower the weight without severely compromising the structure of the plane, so engine and prop optimization is the best bet imo.

Has anyone here seen or heard of variable pitch propellers being used in experimental aircraft like the long-ez?

 

As far as engines go, I'm thinking maybe a UL350iS or a UL390i, they are lighter than a O-235, and get similar HP, but I'm unsure about whether they're suitable for this application.

 

What are y'all's thoughts on this idea?

Is optimization a realistic goal for a Long-EZ considering it's already quite optimized?

 

Are there any other things that might be optimised that I'm overlooking?

[Kent Ashton]

21 hours ago, Grace said:

Is optimization a realistic goal for a Long-EZ considering it's already quite optimized?

An EZ will already fly more hours than you might want to sit.  As a wag, 40 gallons at 4.5 GPH is 10 hours in the cockpit.  I recall getting about 4.5 GPH in an O-320 Cozy III when I had a strong tailwind, flying lean at some reduced RPM.  My wife was not happy about nearly 5+ hours in the air.  😞  Since drag goes up with the square of the velocity, flying slow will increase range more than airframe tweaks.  Getting up high works too so with O2 at 17500', drag is reduced but it gets cold up there.  You might look into a turbocharger but I don't think many EZs have used one because who wants to fly for 10-12 hours with toes starting to freeze?  Unless you plan to cross oceans, it is nice to just stop for gas in 3-4 hours and stretch.    I've read that EZs can make it from the west coast to the east coast in two hops with the right tailwind.

However, normally I'd say you'd see 6-7 gph in most EZs which is still 5-6 hours in the air.

[zolotiyeruki]

I have no personal experience, but I can pass on a few things I've heard:

1) Lean the engine in cruise
2) There are a few things you can do to decrease drag. I seem to recall Mike Melville built a custom oil pan so that he could make a more streamlined lower cowl.  Nose gear door, main gear hoop fairings, and good wheel pants will help.  Optimizing cooling can help as well.  The design is pretty clean in the base case, though.
3) Make sure the airplane is built clean, light, simple, and is rigged as perfectly as you can.
4) Fly at a more rearward CG
5) Fly high

[Marc Zeitlin]

23 hours ago, Grace said:

I'm trying to figure out what the best way to increase the fuel economy I can get from a Long-EZ is, and the obvious solutions (that come to mind for me) are 1. lowering weight, 2. using a more efficient engine, 3. variable pitch propellers.

The way to lower the weight of a Long-EZ is to build it light per the plans. But weight (in the range we're talking about - saving 50 lb. or so) is going to have an immeasurably small effect on the fuel economy - flying at aft CG is far more effective (but light is always good, in every way).

UL engines are NOT more efficient (lower BSFC) than Lycoming engines with EFII systems - not by a long shot, and there is no more efficient SI engine than a Lycoming with an SDS EFII system.

While there are folks who've used C/S props on canard pushers, the ONLY reason to do so is to reduce takeoff rolls at short airports. They do not increase efficiency in cruise - no one who's used one has ever reported that, and in fact, they've reported the opposite - lower speeds in cruise at the same fuel burn.

 

If you want to increase efficiency, you:

• Read everything that Gary Hertzler and Klaus Savier have ever written about the drag reduction efforts on their Variezes and Long-EZ and copy them to the extent possible - Gary gets ~60 SM/gal. in his VE, at about 120 KIAS (a bit to a fair amount above the Carson speed). Klaus is not dissimilar in his VE, and maybe 40 NM/gal in his Long-EZ. These drag reduction efforts are a CRAPLOAD of work and changes to the plane, and even if incorporated in the original build, will add a lot of time to it.
• Install an SDS EFII system on your Lycoming engine (and design the fuel system to support it). You then tune the crap of it to maximally reduce fuel flow in cruise.
• You fly at 40% - 50% power, somewhere between best L/D speed (75 KIAS - 85 KIAS, depending) and Carson speed (100 KIAS - 110 KIAS), at the highest altitude at which you can develop 40% - 50% power.

After you do all this, you'll save some fuel on long trips and have bragging rights to efficiency, but not much else. These are already pretty freaking efficient planes.

[zolotiyeruki]

Marc, do you have links to the writings of Gary Hertzler and Klaus Savier?  I'd love to read up on what they did.

[Marc Zeitlin]

3 hours ago, zolotiyeruki said:

Marc, do you have links to the writings of Gary Hertzler and Klaus Savier?  I'd love to read up on what they did.

Not really, no - you just have to search the archives of all the mailing lists. Neither of them are very vocal, although Klaus is becoming moreso. Check the archives of the COBA/CSA newsletters - that might be the best place for both of them.

[Voidhawk9]

Both Gary and Klaus each gave a Zoom presentation awhile back. Should be a good intro into what they did and their thinking.

Not sure if anyone has a link to the recordings from the archives. If you can't find them, I can upload them, I have a local copy of each.

[zolotiyeruki]

Someone in the Friday Cozy call posted an hour-long video of Klaus (and others) discussing optimizations at Airventure 2023.  I've watched most of it, and there's a lot to chew on there.