Is Sonex the Best Choice

[bullwinkle]

Eric, thanks for helping me find a local Sonex owner. I swear someday we will be at the airport at the same time so I can check out your plane. I check your hangar every time I am there.

Andy - The Jabiru 3300 would be a lot of fun, but that puts the cost of acquisition and operation near an RV-4. I think I'd be stuck with a Aerovee Sonex for the time being. When you say a long runway, are you talking 2000, 2500, 3000? 130MPH indicated or TAS at altitude? I would be plenty happy with 130MPH indicated, as long as it isn't working the engine at max RPM, temp, etc. I've flown a Cessna 120 with 85HP and about 400 lbs heavier than a Sonex at gross. I can only imagine the Aerovee outperforms the 120 by a bit.

Here in Georgia on a humid 95 degree day, I would not want to take off on less than 3000, and be prepared to abort the takeoff if you are not off the ground in a reasonable distance. The Sonex is lighter, but also has less wing than the Cessna 120. IIRC the airfoil on a Sonex is the same as a Grumman Yankee wing, and that airplane is a known dog in climb under high DA conditions.

At altitude I'd flight plan 130mph true. You might do better than that, but I know a lot of Aerovee Sonex guys plan around that number. Also be aware an Aerovee is a kit-built motor, with all that that implies. The guys I have seen with them tend to spend a lot of time tweaking them; how much of that is necessary and how much is just optimization fiddling, I can't really say.

You are right, a 3300 Sonex starts to get pricey. A friend of mine recently decided against a Sonex and is instead building an RV-4 for exactly that reason. But the Sonex will probably perform close to an RV-4 and burn less fuel and maybe be a tad simpler to maintain. It just depends on what you are looking for.

 

[docmirror]

Hmmm. How are the harmonics? Any red arc? What RPM range? What RPM limit? How does the gyroscopic stress of the metal prop blades work out on that Aerovee hub? Why would it be that you will not currently find metal props on these setups?

Depends on clocking, and counterweights, cowl, etc. No red arc. Red line est 3600. If one doesn't like metal, one could use my other suggestion on composite. Or, back to wood of similar size. Metal props aren't found on them because there aren't any that are commonly avail in the pitch range, weight, and potential for gyroscopic stress(as you noted).

Anything else?

 

[bullwinkle]

The limiting factor in a VW conversion is keeping the cylinder heads cool. You can squeeze more power out of a VW, at the expense of engine life. If someone wanted to cast up some watercooled heads, I think you could get that extra power, but if you're going to that much trouble, might as well just buy a nice, proven engine like a Jabiru or a Rotax.

This is true. The problem is higher power comes at higher RPM. The Sonex is already slinging a very short prop with the Aerovee because the engine redline is 3300rpm. If you spin much faster, you need a gear reduction, which adds weight and complexity.

That is why the Aerovee is 80hp; it's kind of the limit of a VW engine without a gearbox, and a gearbox would go against the Sonex factory "keep it simple" philosophy.

Sonex has been working up a turbo unit for the Aerovee for a few years now, and it's in flight testing. It's allegedly 100-ish horsepower, but it adds weight and heat. I honestly don't know how they are going to keep than thing cool without an air-to-air intercooler, which the unit currently doesn't have. Adding the intercooler will add even more weight, and may push it past the factory 200lb FWF limit.

 

[bullwinkle]

I'm willing to sacrifice takeoff distance for cruise speed, fuel efficiency, and cost. Is the Aerovee powered Sonex really much more underpowered than a 1450lb+ Cessna 120/140 with a C85?

In climb, yes. Because of wing area and airfoil.

 

[RoscoeT]

Anything else?

Nope, you've basically listed all the unknown issues (problems) associated a truly experimental prop installation. So we can now ignore your recommendation for rigging up some metal prop on an Aerovee, simply based on the advice of some guy with an internet account. Real engineering and testing would need to be done by those actually qualified.

And how do you know there would be no red arc (harmonic zone)? Have you tested or calculated this with your hacksawed, repitched Cub prop? How do you know 3600 RPM would be a tolerable RPM limit? A big factor in Lycoming and Continental RPM limits is fatigue and vibration issues with metal props...which I'm sure you're aware is way below 3600 RPM.

 

[bullwinkle]

Sonex says; 'trust us, use this prop'. But, I don't think they've done their diligence by only testing props around 53-57". The issue also may be that a 65" prop would approach mach @ 3600RPM, and 120kts, but I think it'll be close.

They have tested literally dozens of props in different lengths and designs. They really have done the diligence on this, and the Prince and Sensenich props they recommends are about the best options.

Longer props do become less efficient on that engine because they lose efficiency due to tip speed. A gear reduction would fix this, but Sonex doesn't like them because they add complexity. If that is your cup of tea you can get a VW engine with PSRU from another company with a longer prop, it will bolt right up to the Aerovee engine mount. Some cowling mods probably required.

 

[bullwinkle]

I'd be interested to see how one performs as well and maybe compare it to a Rotax powered one.

There are only a couple of Rotax powered Sonex around, I think there is one in the Netherlands (?) and one in the US. Sonex doesn't like the engine because of its gearbox and liquid cooling.

But I think think they are missing the boat bigtime on that -- 100hp engine that runs very cool and weighs 25lb less than their 80hp engine would be a BIG winner. And it's 53lb less than a Jabiru 3300, so they might perform similarly in that airframe.

 

[docmirror]

Nope, you've basically listed all the unknown issues (problems) associated a truly experimental prop installation. So we can now ignore your recommendation for rigging up some metal prop on an Aerovee, simply based on the advice of a guy with an internet account. Real engineering and testing would need to be done by those actually qualified.

And how do you know there would be no red arc (harmonic zone)? Have you tested or calculated this with your hacksawed, repitched Cub prop? How do you know 3600 RPM would be a tolerable RPM limit on a metal prop? A big factor in Lycoming and Continental RPM limits is fatigue and vibrations issues with metal props.

Wow, you really have a giant red bug up your a$$ chewing on your intestines. I agree, you really should put me on ignore. I've given you the calcs to start with, I stated up front that I didn't do any air testing, I advised that this would be a starting point, and gave my reasons which are well grounded in math, but you still gotta put your no-nothing, calculate nothing, guesswork questions out there which anyone with half a brain(like you) would know need to be tested.

Really, if you want to dispute my findings, come up with some primary engineering work of your own, rather than SWAG you read off last months AOPA online newsletter. You're boring, and one of the crowd that will never test or build anything. Go back to your Cessna and leave pros to discuss engineering principles. Cya.

 

[Henning]

Well, the VW design is going to start having trouble much over 80HP @ ~3600RPM. Sure, you can up it by higher C/R, and some tweaking to the cam, and some big valves, down draft dual carbs, etc. The problem is that things start to wear quickly when you get up much higher in HP. We want a reliability reserve in aviation which is why 200CI Conti engines only put out 100HP. The VW is 133CI, so by the same ratio, we would be putting out 66HP, so the VW is now putting out more than 25% more than the Conti by ratio.

The VW engine has to be relieved inside to swing the 82mm crank and rods. The cylinder studs have to be set in case savers, and the heads are bored so close that there's hardly any material left in the cylinder seat area.

I've built a few air cooled VWs back in the dune buggy days, including one with a Paxton SC driving it. I got around 110HP, and more was available but I wanted it to last for 2 seasons.

If I were to start modifying a VW like the Aerovee or Great Plains engines, I'd first work on the intake which has a bunch of turns, and stuff to get the intake charge routed up to the top of the engine. Buggy engines have dual down draft twin choke carbs on them for good breathing. Sadly, that will require a change in the cowl, and then things get more complicated. Frankly, I'd stay at 80HP, and deal with the limitations.

<edited for clarity and to fix some spelling. >

For the RPM an Aerovee turns, I'd just put on a twin throat Weber side draft and mount it intake forward in the high pressure zone in the front top of the cowl behind the prop, then manifold it back and down to the heads. Long swept runners will be a positive in an aircraft application. A good Tri-Y pipe is just as important.

 

[docmirror]

They have tested literally dozens of props in different lengths and designs. They really have done the diligence on this, and the Prince and Sensenich props they recommends are about the best options.

Longer props do become less efficient on that engine because they lose efficiency due to tip speed. A gear reduction would fix this, but Sonex doesn't like them because they add complexity. If that is your cup of tea you can get a VW engine with PSRU from another company with a longer prop, it will bolt right up to the Aerovee engine mount. Some cowling mods probably required.

Sorry, not buying. The calcs show a tip speed around 1050 ft/sec at moderate alt and temps to be optimal. 54" prop comes no where close. And I was wrong about the RPM limit. I was using 3600 and aerovee uses 3300 so that would be an even slower tip speed. They aren't anywhere near mach, so like I said way back, I think they are leaving thrust on the table for other reasons not associated with maximizing thrust.

This discussion started because we all think the 80HP Aerovee is underpowered. I'm looking for a way to improve the thrust, without going off and messing up the reliability of the engine. So far, no one else is making suggestions, and the backbiting is frankly rather annoying so I guess I'll take my ball and go home. Some time, should I get a Sonex, I guess I'll find out myself. Until then, my mental masturbation is as good as anyone elses(who has done the prop calcs, and come up with limits, which is -- well, no one else).

Buh-bye.

 

[RoscoeT]

Go back to your Cessna and leave pros to discuss engineering principles. Cya.

LOL. I'm not a pro and without a doubt, neither are you. If I'm wrong, tell us your work experience in the field of aircraft design and development. The difference is that I would not pull out some shoot-from-the hip advice on how to configure an airplane, which is contrary to the design and testing done by the actual experts. You're just babbling on the internet. All my responses are a waste I'm sure, since I would surely imagine the OP has enough sense to ignore you and your advice.

But I guess my RV-4 is basically a tin can Cessna.

 

[docmirror]

For the RPM an Aerovee turns, I'd just put on a twin throat Weber side draft and mount it intake forward in the high pressure zone in the front top of the cowl behind the prop, then manifold it back and down to the heads. Long swept runners will be a positive in an aircraft application. A good Tri-Y pipe is just as important.

We used twin throat 44mm side draft Webers on the buggies in a draw through turbo with some good results. The Weber do like long runners to minimize reversion. But again, you're making HP that is going to be hard to dissipate with the stock VW heads that have already had material removed, and fins removed for dual plug. Even the best cowling will have trouble with CHT on a TX day at full power. Aerovee recommends a full span oil cooler on the bottom of the engine for better oil cooling, but the point source at the heads is where the limits are.

 

[docmirror]

LOL. I'm not a pro and without a doubt, neither are you. If I'm wrong, tell us your work experience in the field of aircraft design and development. The difference is that I would not pull out some shoot-from-the hip advice on how to configure an airplane, which is contrary to the design and testing done by the actual experts. You're just babbling on the internet. All my responses are a waste I'm sure, since I would surely imagine the OP has enough sense to ignore you and your advice.

But I guess my RV-4 is basically a tin can Cessna.

Words <> math.

Oh, I thought you were gonna ignore me? It's in your user control panel on the upper left. If you want more from me, I charge $375/hour min 3 hours plus travel. So far you've paid - well, lets calculate that, oh yeah - it's ZERO DOLLARS. Which leads back to the ignore function.

 

[Direct C51]

If you are in the North Carolina area I would look up a guy named tony spicer. He was the first customer to build a sonex and has since built an rv-4 and is currently building a panther. He should be able to answer just about any question you have. You can also go to the sonexaircraft website and there is a place to search for builders and completions by state.

Do you have Tony Spicer's contact info? I have searched the Sonex website Builders Database but only found one guy around here with an Aerovee that listed any contact info. Most don't have any info listed. Any help finding a Sonex onwer, especially with an Aerovee within a reasonable distance of KTTA would be greatly appreciated. Or if you can point me in the direction of any other database or Sonex forum, I would be happy to keep searching.

 

[JimNtexas]

Why do homebuilt airplanes only fly in mph?

 

[Direct C51]

Why do homebuilt airplanes only fly in mph?

Probably because 130 MPH sounds better than 110 Knots. It sounds a lot better when an RV can claim 200 MPH. 173 Knots doesn't sound like as much of a milestone. Most people can relate better to MPH and makes performance numbers a little easier. Of course this is all considering you live in America.

 

[Henning]

Sorry, not buying. The calcs show a tip speed around 1050 ft/sec at moderate alt and temps to be optimal. 54" prop comes no where close. And I was wrong about the RPM limit. I was using 3600 and aerovee uses 3300 so that would be an even slower tip speed. They aren't anywhere near mach, so like I said way back, I think they are leaving thrust on the table for other reasons not associated with maximizing thrust.

This discussion started because we all think the 80HP Aerovee is underpowered. I'm looking for a way to improve the thrust, without going off and messing up the reliability of the engine. So far, no one else is making suggestions, and the backbiting is frankly rather annoying so I guess I'll take my ball and go home. Some time, should I get a Sonex, I guess I'll find out myself. Until then, my mental masturbation is as good as anyone elses(who has done the prop calcs, and come up with limits, which is -- well, no one else).

Buh-bye.

If you think torque is being left on the table, add some more fuel and air, use a 302° cam and big valves with a big bore carb and long intake runners and a semi tight pipe, or put on a turbo (or all of the above), for a static load engine, it's probably cheapest and most efficient to just use a turbo.

 

[jesse]

Luckily I've never flown in one, because if I did, I'd probably buy one of the damn things. Surely the performance with the Aerovee can't be worse than my FlyBaby with the A75.

 

[FormerHangie]

Luckily I've never flown in one, because if I did, I'd probably buy one of the damn things. Surely the performance with the Aerovee can't be worse than my FlyBaby with the A75.

Depends on what you consider performance. The Fly Baby is lighter and has more span, and at takeoff and climb speeds probably has more thrust. Takeoff and climb should be better, cruise speed undoubtedly will be slower.

 

[jesse]

Depends on what you consider performance. The Fly Baby is lighter and has more span, and at takeoff and climb speeds probably has more thrust. Takeoff and climb should be better, cruise speed undoubtedly will be slower.

300 fpm is about all I can climb at. That said I can jump off a runway and to 50 feet in no time at all.

 

[bullwinkle]

Sorry, not buying. The calcs show a tip speed around 1050 ft/sec at moderate alt and temps to be optimal. 54" prop comes no where close. And I was wrong about the RPM limit. I was using 3600 and aerovee uses 3300 so that would be an even slower tip speed. They aren't anywhere near mach, so like I said way back, I think they are leaving thrust on the table for other reasons not associated with maximizing thrust.

This discussion started because we all think the 80HP Aerovee is underpowered. I'm looking for a way to improve the thrust, without going off and messing up the reliability of the engine. So far, no one else is making suggestions, and the backbiting is frankly rather annoying so I guess I'll take my ball and go home. Some time, should I get a Sonex, I guess I'll find out myself. Until then, my mental masturbation is as good as anyone elses(who has done the prop calcs, and come up with limits, which is -- well, no one else).

Buh-bye.

First, I was not attacking you, just stating what I KNOW from years of working with the Sonex factory. I was just having a discussion, you took offense assuming I was shooting you down.

Second, speed of sound at sea level is 1116 ft/sec, which is pretty close to 1050 ft/sec. Have you heard of a little thing called "transonic drag"? It's not like prop tips instantly get useless at mach...the drag on them increases exponentially as they *approach* mach, which makes the prop efficiency go into the toilet anywhere near those speeds.

Okay, buh-bye. Don't let the chip on your shoulder hit you in the ass on the way out. Just because you are "the only one making suggestions" does not mean the suggestions are good ones.

 

[bullwinkle]

300 fpm is about all I can climb at. That said I can jump off a runway and to 50 feet in no time at all.

Is that even on a cool day, or just in summer heat? 300fpm in the winter is pretty scary, I'd park that thing in summertime!

 

[FormerHangie]

300 fpm is about all I can climb at. That said I can jump off a runway and to 50 feet in no time at all.

Something's not adding up here. With that short takeoff run you should be getting a better climb rate.

 

[jesse]

Something's not adding up here. With that short takeoff run you should be getting a better climb rate.

It was substantially better when I had the canopy on the Flybaby. Open cockpit really tanked the climb performance. I could try and clean things up, but don't really care that much, since I rarely fly above 1,000 ft anyways.

My cruise speed difference going from closed cockpit to open cockpit barely changed. Maybe 3 knots.

Engine seems strong, compression is good, I have no problem getting the RPM(s) I should. Might just be the prop..but there's no way I'm giving up cruise speed for more climb.

I view the Flybaby as an airborne motorcycle that is fun to go fly around and look at things in. If I really need to go somewhere I get a different airplane. Although I did fly it to Airventure last year and will do so again this year.

 

[PW_Plack]

Well, the VW design is going to start having trouble much over 80HP @ ~3600RPM...The VW engine has to be relieved inside to swing the 82mm crank and rods. The cylinder studs have to be set in case savers, and the heads are bored so close that there's hardly any material left in the cylinder seat area.

It's important to note that the AeroVee has few or no actual VW parts. The case has more clearance than stock, and the and heads probably have more meat in critical areas. They are are purpose-built aftermarket units designed for increased bore and stroke.

If these things were routinely shedding props or otherwise falling from the sky, I think it would have made news. I've heard of only one forced landing by a Sonex in the past few years, and there was no indication it was even AeroVee powered.

 

[Art VanDelay]

How could you knuckleheads be this far into the discussion of a Sonex with nobody mentioning the Viking engine ??? This engine makes all the difference for that airplane. Do I have to do everything around here ?

http://www.vikingaircraftengines.com/sonex.htm

 

[Direct C51]

Twice the price of an Aerovee, liquid cooled, HEAVY, and appears to need to be geared. Please elaborate on how this is a game changer? If I wanted to spend the extra pennies I'd get the Jabiru and have 15 more HP and way less hassle. Maybe I don't know what I'm talking about. I welcome your comments.

I know this is comparing apples and oranges, but what about a Long-EZ? They can be had for $25,000 - $30,000 and extremely efficient. Seems infinitely more complicated than a Sonex however.

 

[jhausch]

Beware... Many random thoughts ahead:

Two Aerovees in a breezy or scaled down AirCam would be cool....

Maybe a sleek "derringer" like twin with Aerovees. Seems like the tiny aerovees in tiny nacelles would do ok with those tiny props...

Seems like the Aerovee and Onex are a good match.

Got an email about the latest version of the SubSonex jet taking flight.

How long before we see a slightly larger homebuilt with two of those $40k bad boys?

 

[Art VanDelay]

Twice the price of an Aerovee, liquid cooled, HEAVY, and appears to need to be geared. Please elaborate on how this is a game changer? If I wanted to spend the extra pennies I'd get the Jabiru and have 15 more HP and way less hassle. Maybe I don't know what I'm talking about. I welcome your comments.

I know this is comparing apples and oranges, but what about a Long-EZ? They can be had for $25,000 - $30,000 and extremely efficient. Seems infinitely more complicated than a Sonex however.

Did you bother to read anything from the satisfied customers ? To get an engine at this weight and horsepower you would have previously had to pay BIG money and get a Rotax 9 series. If you see liquid cooling and gearing as being a problem then I guess you fear for the all the untold thousands of Rotax 912 and 914 flying all over the world currently. Jabiru's are pretty notorious for both cooling problems and VERY poor quality control - check around and see.

 

[Velocity173]

Get a Long EZ. You're gonna wish you had the extra performance. Even the 0-235 versions will edge out the 80 hp Sonex and you've got over twice the range to boot! Of course I'd spend the extra 10 grand and get a Glasair at 165 kts and aerobatic but I'm bias.

 

[Concorde]

There are two beautiful sonex aircrafts at Siler city airport very close to you.
Give FBO a call for contact info.

 

[Jimmy cooper]

A friend flew his Sonex down to see me for the day last weekend from near buffalo , ny to maryland. He is a former airforce f 15 mechanic and built the Sonex in his garage over a two year period. We both have owned Taylorcrafts and cubs alot, so we are familiar with underpowered aircraft. He used the aerovee engine and flys it out of 2800 feet of grass in western ny state. No problem. He flys it mainly alone but if wife goes along he picks her up at nearby jamestown airport. He says , like the t craft, once up and in cruise it flys very well but no super cub on climb. He did a very nice job on it, very professional and it looks great. He has approx. 200 hours on it, no problems.

 

[Direct C51]

There are two beautiful sonex aircrafts at Siler city airport very close to you.
Give FBO a call for contact info.

Yeah I tried to contact one of those guys at Siler City but the contact info on the Sonex Builders Website was incorrect, the other not listed. I believe they both have Jabirus too. I'll dig a little deeper to see if I can contact one of them.

 

[Direct C51]

Get a Long EZ. You're gonna wish you had the extra performance. Even the 0-235 versions will edge out the 80 hp Sonex and you've got over twice the range to boot! Of course I'd spend the extra 10 grand and get a Glasair at 165 kts and aerobatic but I'm bias.

It's easy to keep moving up $10,000 at a time and then I'm back in RV range. A Glasair would be sweet but transitioning to the new career is just not conducive to expensive airplanes. I like the Long/Varis but they have their quirks too. Also a little more expensive to buy, the engine is a little pricier if needed replacing or overhauling, and I'm much more familiar with aluminum and rivers than composites. So many airplanes, such little disposable cash.

 

[Henning]

Get a cheap ultralight for now.

 

[FormerHangie]

How could you knuckleheads be this far into the discussion of a Sonex with nobody mentioning the Viking engine ??? This engine makes all the difference for that airplane. Do I have to do everything around here ?

http://www.vikingaircraftengines.com/sonex.htm

Maybe because the OP wants to fly and not build, and there are hardly any flying Sonexes with that engine. From what I can tell, there are hardly any aircraft of any type flying with that engine.

Sonex has two very well debugged engine packages for that aircraft. If someone likes to tinker, he may want to try something else. If you'd rather fly, I'd pick one of those two, or at least something very similar (Revmaster or Great Plains VW).

 

[zaitcev]

How could you knuckleheads be this far into the discussion of a Sonex with nobody mentioning the Viking engine ??? This engine makes all the difference for that airplane.

Do you actually fly a Sonex with Viking or you're just reading Mr. Eggenfelner's propaganda? That little detail makes all the difference.

I, for one, would love to get the skinny on Viking. I heard some rumours about the past adventures of the principal of Viking, but I hope that the switch to Honda created a fresh start.

 

[zaitcev]

It's easy to keep moving up $10,000 at a time and then I'm back in RV range.

In that case, you simple cannot close the case to include the performance and budget, and need to either give up, downsize as Henning suggested, or find the money. The money option may be tough. I remember how Dick Carl wanted to buy Cessna Mustang and wrote "I just need to do a few more operations per year". A few short years down the road, and he's given up on his whole neurosurgeon career and drives a Lear for a living. Oops.

I took the Henning option after all the nibbing on the Sonex hook, although not an ultralight. I am at 5000 ft after all.