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.

[aerialsasquatch]

@zolotiyerukiand @Voidhawk9 can you share those videos? I'm not having much luck finding them. I'm happy to host them in my Gdrive for others to easily access as well - I have a lot of storage and this seems like a great use, especially so they don't disappear into the ether like so many old builder websites, etc. that I keep trying to click on

[Voidhawk9]

Here's the 4 talks I have (big files to download):
Gary Hertzler
Klaus Savier

Nick Ugolini 1

Nick Ugolini 2

[jridge]

Here's several videos that are posted on YouTube from a couple of Airventures and incude Klaus, Burt, Gary Hertzler and Terry Schubert.

https://www.youtube.com/@SBAviator1/videos

[aerialsasquatch]

Thanks for these! They've all be added to the list.

For posterity, I also found:

 Mr. Savier talking (high level, at least) about several of his anti-drag efforts on his Long-EZ. The "anti drag is way more efficient than adding hp" is super compelling, and really antithetical to my motorcycle brain. I've been reading Marc shout from the rooftops about building better to go faster, but for some reason it didn't really fall into place until Klaus mentioned the little horizontal filet on his canards, and suddenly all of Marc's writings, the other stuff I've been seeing on the subject, and my new fangled physics learnin' dropped into place.

Thanks again for the shares! I've got them saved to my GDrive, if you think it would be useful to share for redundancy and preservation, just let me know and I'm happy to drop a folder with all of the things I've found.

I'm really worried that as the builder websites expire, get taken down, and forums come and go, there is so much valuable information to be lost for people like me and afterward coming into it, so I'm hoping to at least preserve what I find useful to propagate to the next bozo like me who starts thinking about it.

[Voidhawk9]

Yes, absolutely share what you've found. I may find something new to me there!

If you want to dig deeper, there's some good stuff from the late Mike Arnold:

 

[Mike S]

Hello everyone.  This is a topic I've spent way to much time thinking about. My first VE easily got 40mpg with a c85. But not at high cruise. I've always thought you could have both. I'm surprised Mr Marc didn't link this to the discussion; http://www.cozybuilders.org/Oshkosh_Presentations/2007_Blended_Winglet_Eracer.pdf . To summarize there was a 10% speed increase at the same power setting. Marc can comment from a first hand perspective. The topic by HDMX seems to be addressing this as well.

One name not mentioned is Bill James. His cooling system is as good as it gets; https://ez.canardaircraft.com/www.ez.org/feature/F0502-1/F0502-1.html. He also addresses props.

My personal list for areas to work on- blended winglets, over the top engine cooling, a 3 liter corvair w/EFII optimized to run in the 32-3800 rpm range, an unducted fan style multi blade prop, aft retracting mains into inboard booms with double acting rudders.

( I sent this to Marc last year but ended up out of the country and couldn't pursue it then);

I can write a book on my reasons for corvair power- much lower weight, designed for higher rpm, zero primary vibration, half a foot less in L/W/H. A 180 cu engine turning 25% faster than a aero engine at the same power setting could use 25% less fuel at a 15/1 F/R ratio. We'll see. (BTW-my engine was turbocharged from the factory).

The retracts address the flat plate area of fixed mains and wheel plants and intersection drag between the gear leg and hull. I realize I'm adding parasite drag but I hope it's cost to total drag is less than FP drag. I previously watched all the Mike Arnold videos. There are a few gems but really apply to conventional wing/fuselage intersection drag more so than an EZ. The slab sides and wing strakes with almost no hull taper negate that drag component.. (imho):)..

Looking forward to any comments..

Rgds, Mike

[Marc Zeitlin]

4 hours ago, Mike S said:

I'm surprised Mr Marc didn't link this to the discussion; http://www.cozybuilders.org/Oshkosh_Presentations/2007_Blended_Winglet_Eracer.pdf . To summarize there was a 10% speed increase at the same power setting...

Slide 16 has the salient information - the majority, if not all of the drag decrease with the blend was accomplished due to the crappy location of the winglets on the E-Racer, caused by Shirl Dickey's desire for aesthetics over aerodynamics. If you take a look at THIS presentation:

http://cozybuilders.org/Oshkosh_Presentations/2009_Esselstyn_Blended_Winglet.pdf

you can see that blending the winglets on a more optimized design (COZY MKIV, which is identical to the Long-EZ in this respect) did exactly nothing for drag reduction - see slides 14 - 16 for a discussion. It is not at all clear that blends will create large drag decreases - we have zero instances of an A - B comparison of optimized blends on a Long-EZ or COZY aircraft.

The closest we have are the winglet / wing intersection fairings that James Redmon implemented on his Berkut 360, which, after optimization, got him 2 - 3 KTAS at the top end (210 - 220 KTAS, IIRC). So the implication is that there is a small amount of drag reduction that is possible with optimal blending, but no one has achieved that yet.

4 hours ago, Mike S said:

One name not mentioned is Bill James. His cooling system is as good as it gets

Bill James has done some very cool, innovative stuff. But again, there is no A - B comparison of updraft vs. downdraft cooling, and I see no reason to go through the complexity of downdraft cooling on these planes, although a few people have made it work. The two most efficient VEs on the planet (Gary Hertzler and Klaus Savier) both use updraft cooling, with minimal cooling drag. Unless someone can show a drag decrease when implementing downdraft cooling (and no one has done so yet), I would recommend against it from a complexity and risk standpoint - it's a LOT harder to get it to work well.

4 hours ago, Mike S said:

My personal list for areas to work on- blended winglets, over the top engine cooling, a 3 liter corvair w/EFII optimized to run in the 32-3800 rpm range, an unducted fan style multi blade prop, aft retracting mains into inboard booms with double acting rudders.

Blended winglets - discussed above. Downdraft cooling, discussed above.

Corvair engine - I've only ever seen one, although there are many in non-canard aircraft. Realize that a prop optimized for 32 - 3800 RPM will be a lot smaller in diameter, so a lot less efficient. Multi-blades is less efficient than fewer blades as well (although not a lot), so you're moving in the wrong direction on two fronts.

Adding booms to the wings just adds a lot more profile drag, while retractable gear adds a lot of weight (which also increases drag). Well faired gear, at the speeds we fly (witness Hertzler and Savier) is just about as good as retracts, at far lower cost, weight, complexity, and maintenance needs. Unless you're cruising > 200 KTAS, retracts make very little sense.

Inboard rudders at the end of booms can work fine, but the system complexity will be a LOT higher. You now need a cable circuit and need to decouple the rudder and brake actuation. Weight, complexity, maintenance.

5 hours ago, Mike S said:

I can write a book on my reasons for corvair power- much lower weight, designed for higher rpm, zero primary vibration, half a foot less in L/W/H. A 180 cu engine turning 25% faster than a aero engine at the same power setting could use 25% less fuel at a 15/1 F/R ratio. We'll see. (BTW-my engine was turbocharged from the factory).

So there are a couple of COZY MKIVs which have ULPower engines on them, which weigh 75 lb. or so less than the specified O-360. All that did was reduce the possible front seat loading from ~400 lb to ~320 lb., and require substantial REAR ballast in the case of wanting to carry two heavy folks in the front seat. Reducing the weight of the engine on a Long-EZ MIGHT be OK, but the change in empty (and loaded) CG will affect carrying capacity and CG location - moving the flight CG forward will increase drag substantially - my plane is 7 KTAS faster at the aft limit than at the forward limit, at the same GW. So weight reduction MIGHT be a good idea, IF you know what affect it'll have on CG.

You can wave your hands around about fuel consumption magically being better at higher RPM, but there's zero evidence for that. A good estimate for BSFC for most car engines is about 0.5 lb/hp/hr. If you're really good, and you can lean the crap out of it with a good FI system, you might get down to the 0.42 - 0.45 range - you won't get lower than that, and anyone that tells you you will is lying. A Lycoming engine with an SDS EFII system can do about 0.42 lb/hp/hr, and my engine will run down to an AFR of 17.5:1 - 18:1. If you put a turbocharger on your engine with lower compression pistons, you'll be lucky to get to 0.5 lb/hp/hr. So that engine/prop/RPM combination will be almost guaranteed to get lower mpg than a lycoming with an EFII system would.

There are your comments. People may think that I like raining on parades, or throwing wet towels on folks (and I have to admit, there is a bit of satisfaction from it), but we have to realize that airplanes are an extremely mature technology - they've been around for 120 years and have been fairly well optimized. Rutan derivative canards have been around for more than 45 years now, and pretty much anything you can think of to make them "better" has been tried. Some stuff works - again, see Hertzler/Savier/James/Redmon and others - but the vast majority of random crap that people try does NOT make the planes "better", with whatever definition of "better" the modifier was attempting to achieve. I've examined over 130 unique "N" number canards and have seen about everything that folks have tried - the largest part of them have been negative to neutral at best, and unsafe at worst.

So whatever modifications one chooses to make, one should be extremely cognizant of what has come before and assume that if you thought of it, someone else has thought of it before you. Does that mean you WON'T come up with some magic improvement that no one's thought of before? Nope - you might. It's just that the chance of it is extremely small, and it's not the way I bet.