Fly Baby power plant options

[valittu]

I'm about to embark on building a Bowers Flybaby and I'm currently in the planning stage. What would you classify as the most efficient options for a power plant in terms of weight and maintenance? What's the highest horsepower I could install and keep within Light Sport Aircraft parameters?

 

[jesse]

Mine has an A75. That said, if I were to build, or had to swap engines I would be going with either a C85 or an O-200. Nobody makes cylinders for the A65/A75 anymore (which is amazing).

The O-200 would obviously do better in climb performance but there are some things you'll want to do if you go that route. I think the plans might call for using larger bolts than AN3 on the flying wire brackets and possibly using thicker flying wires. The downside of the O-200 is going to be the lack of fuel. But if you throttle it back to C85 like performance it's probably a total wash.

 

[Henning]

You should get some good answers to that here! I'd say the most economical way is an O-200 if you want the 100hp, there are also smaller C series. Rotax 912 or 914? Probably cost more up front, not sure if there would be a long term advantage. Corvair, Subaru, and Volkswagon based engines exist as well.

 

[jesse]

If you haven't looked at this page, this has a lot of info:

http://www.bowersflybaby.com/tech/engines.htm#On_engines

 

[bnt83]

Any of them have an electric starter? O-200 could take a lightweight starter and lightweight prop of some sort.

 

[jesse]

Any of them have an electric starter? O-200 could take a lightweight starter and lightweight prop of some sort.

C85 and O200 versions generally have electric start.

 

[bnt83]

C85 and O200 versions generally have electric start.

Installed in a flybaby with it?

 

[jesse]

Installed in a flybaby with it?

Yes, all the ones I've seen/heard of with those engines have electric start. I met a guy at Airventure from FL that built a Flybaby and he put a O235 in and left the original giant starter. I asked what his empty weight was and he gave me a number lower than mine, doubt that's correct.

 

[wanttaja]

Installed in a flybaby with it [Electric Start]?

Yes, mine has a C-85-12, same engine as on an Ercoupe and has the small generator and an electric starter. A65s can be a good deal, but you won't find them with starters.

Ron Wanttaja

 

[wanttaja]

Mine has an A75. That said, if I were to build, or had to swap engines I would be going with either a C85 or an O-200. Nobody makes cylinders for the A65/A75 anymore (which is amazing).

The O-200 would obviously do better in climb performance but there are some things you'll want to do if you go that route. I think the plans might call for using larger bolts than AN3 on the flying wire brackets and possibly using thicker flying wires. The downside of the O-200 is going to be the lack of fuel. But if you throttle it back to C85 like performance it's probably a total wash.

Jesse nailed it. I've been recommending O-200s to folks, just because the engine is still made and parts are readily available.

The Fly Baby makes an excellent platform for a non-standard engine (auto, home-built radials, etc.) but the little Continentals are far simpler to install.

If you put on a Subaru, you'll need to develop your own mount, figure out how to install a radiator and how to route the hoses to it, build a cowling, figure out the right prop, etc.

In contrast, a Continental-powered Fly Baby is a total clone of a Piper Cub forward of the firewall. Same mount, same exhaust, same intake, same cowling, same engine. Upgrade to C85 or O-200 is minor.

I'm all for people experimenting with alternate engines, but if someone is building an Fly Baby as a personal airplane and DOESN'T have prior engine experience, a Continental is a far better choice.

Ron Wanttaja

 

[Henning]

Ron, what do you think about hanging a 912 or 914 Rotax on one?

 

[valittu]

Jesse nailed it. I've been recommending O-200s to folks, just because the engine is still made and parts are readily available.

The Fly Baby makes an excellent platform for a non-standard engine (auto, home-built radials, etc.) but the little Continentals are far simpler to install.

If you put on a Subaru, you'll need to develop your own mount, figure out how to install a radiator and how to route the hoses to it, build a cowling, figure out the right prop, etc.

In contrast, a Continental-powered Fly Baby is a total clone of a Piper Cub forward of the firewall. Same mount, same exhaust, same intake, same cowling, same engine. Upgrade to C85 or O-200 is minor.

I'm all for people experimenting with alternate engines, but if someone is building an Fly Baby as a personal airplane and DOESN'T have prior engine experience, a Continental is a far better choice.

Ron Wanttaja

So the 0-200 seems like the way to go. My plan is to just keep an eye out for one with low smoh. I'm in no hurry.

 

[PAustin]

Henning - cough, cough a what on a Flybaby?? That's sacrilege.

 

[tinerj]

Any of them have an electric starter? O-200 could take a lightweight starter and lightweight prop of some sort.

My Flybaby with 75 hp continental has electric start, but no electric system. I have a battery that will give about 30 starts (if the engine cooperates) before it needs charging. I charge it more often than that at the home hangar.

 

[wanttaja]

Ron, what do you think about hanging a 912 or 914 Rotax on one?

It's a bit ironic... on my last post, I'd actually wrote, "The Rotax 912 is a interesting possibility..." then wimped out.

I have no experience with the engine, but I figure it's common enough now to not be much of a risk. I attended a 3-hour Rotax-engine familiarization class a few months back, and liked what I heard.

THAT said, we get to the reason I wimped out: Installing a Rotax 912 on a Fly Baby has basically the same installation challenges as a car engine. New mount, having to figure out the radiator location and coolant tank locations, plumbing, etc.

It's doable...and considering the Rotax's inroads in aviation, probably the best alternative to the Continental.

But it still puts a big load on the builder to solve a bunch of non-airframe challenges.

Lemme put it this way: The Fly Baby plans are 256 pages (standard 8.5x11 paper). Only about ~15 pages deal with the engine installation, mostly about how to route the controls and gauges. It doesn't have a ton of details, because Pete Bowers figured that builders would just go down to the local junkyard and pick up a Cub FWF for $800.

For someone to install an alternate engine, they'd have to re-create all the step-by-step details of this legacy.

Again, if someone is technically competent and/or is looking forward to the challenge of adapting a non-standard engine, more power to them! But most people who talk to me about alternate engines want them because they're cheaper or "easier."

I've been flying Fly Babies for about 25 years, both airplanes with C-85 engines. In that time, the "engine" problems I've had to deal with are:

1. Leaking exhaust valve (IIRC, about $400 ~20 years ago...First annual).
2. Shattered center conductor on magneto (replaced with "button" from VW bug distributor)
3. Leaking/cracked exhaust systems
4. Cracked cooling "eyebrow"
5. Starter clutch needed replacement (~$500).
6. Generator failure ($80 and "don't tell me what it's from" at the auto electric rebuilder)
7. Bad regulator ($25 at Arlington Fly-Market)

I do not consider this THAT onerous for 25 years/800 hours of fun (there are a ton of electrical system issues in here, but that's not related to the engine).

And... my current engine (bought with 25 SMOH) has about 600 hours and 20 YEARS since major overhaul. The hours ain't bad, but being 4x past the Continental time limit does tend to prey on my mind. I'm springing for a new exhaust system in the fall, and have started to think about an overhaul (Don't live that far from Tom Downey, and I've got an A&P buddy who rebuilds engines for folks and also owns a Fly Baby).

So... I may be springing $5Gs or more for a rebuild, and the alternate-engine folks will nod sagely and say, "That's the problem with those Contintentals." But if the $5Gs buy me another twenty-five years of reliable flight, I figure it's worth it....

Ron Wanttaja

 

[wanttaja]

My Flybaby with 75 hp continental has electric start, but no electric system. I have a battery that will give about 30 starts (if the engine cooperates) before it needs charging.

In my opinion, that is the *perfect* configuration. Leave off the generator when you build the airplane, but install an electrical system with an external charging port for the battery. You've got the starter and can run a comm radio, but you're not required to have a transponder unless you actually intend to enter Class B or C airspace. The "Veil" under Class B doesn't affect you.

Install the engine with a plate over the generator drive, and if you ever need to, you can just install the generator and regulator.

If the ADS-B rules have the same exemption, I may just build me another Fly Baby.

Ron Wanttaja

 

[Henning]

When we hung the 914 on the Cobra it came all set up on the mount. Just had to make the mount go on the firewall and make a cowling to fit. Wasn't too bad of a deal.

 

[N3368K]

Regarding fuel burn, an O-200 can be operated at lower power and burn under 5gph. We flew three Cubs to OSH a couple years ago. One with A-65, another with C-85 and the last with O-200. We all flew turning 2150-2200. At each fuel stop (about every 1.5 hrs), we all took within two gallons of one another. Typically, it was well under a gallon per hour difference between them all.

 

[Jimmy cooper]

0200 or an 85-12 with a don swords conversion. Much easier to deal with than a 912 which does not like av gas and is expensive.

 

[valittu]

0200 or an 85-12 with a don swords conversion. Much easier to deal with than a 912 which does not like av gas and is expensive.

So the "Don Swords" conversion changes the HP to that of an 0-200? What's the advantage versus cost?

 

[Jimmy cooper]

The obvious advantage is having an 85-12 already and wanting 100 hp. The conversion provides 100 hp for less money, especially if you do the work yourself. It's a very popular route plus he knows these little engines inside out. The 912 does not like av gas either and many mechanics are not familiar with them, tuning the carbs, etc. etc.

 

[valittu]

The obvious advantage is having an 85-12 already and wanting 100 hp. The conversion provides 100 hp for less money, especially if you do the work yourself. It's a very popular route plus he knows these little engines inside out. The 912 does not like av gas either and many mechanics are not familiar with them, tuning the carbs, etc. etc.

So would you recommend purchasing and converting a C-85 instead of purchasing an 0-200 outright? Is the conversion more efficient or cost effective? I don't know anything about engines so forgive my naive questions.

 

[Jimmy cooper]

So would you recommend purchasing and converting a C-85 instead of purchasing an 0-200 outright? Is the conversion more efficient or cost effective? I don't know anything about engines so forgive my naive questions.

Congratulations. You and I apparently are the only ones that don't know everything! I had a long conversation by phone with don swords sometime ago when I wanted to convert my 85-12 champ to an 0200. He explained it very carefully and is very hep. I eventually sold the airplane as I got an excellent offer. I'm told the 85 conversion supply's a little more hp than the standard 0200. 85 hp cont. That will take a light weight starter , etc. are getting hard to find. The 75 is no more than a 65 with a carb . Change. Not worth the trouble. 65 hp is a boring ride and will not accept an electric starter. To me, the starter is a must. Trying to start a very cold or recently flown engine by propping it gets old real quick. ( not to mention lives lost, airplanes running away, etc. )

 

[valittu]

Congratulations. You and I apparently are the only ones that don't know everything! I had a long conversation by phone with don swords sometime ago when I wanted to convert my 85-12 champ to an 0200. He explained it very carefully and is very hep. I eventually sold the airplane as I got an excellent offer. I'm told the 85 conversion supply's a little more hp than the standard 0200. 85 hp cont. That will take a light weight starter , etc. are getting hard to find. The 75 is no more than a 65 with a carb . Change. Not worth the trouble. 65 hp is a boring ride and will not accept an electric starter. To me, the starter is a must. Trying to start a very cold or recently flown engine by propping it gets old real quick. ( not to mention lives lost, airplanes running away, etc. )

Yeah, that hand propping thing is great for nostalgia and all, but I'm sure it will bum me out after say a month or so.

 

[James331]

Ron, what do you think about hanging a 912 or 914 Rotax on one?

I flew behind a rotax once and that was enough for me

Don't get me wrong, I like BRP, but I'll just stick to their jet skis and snow machines.

 

[jesse]

Yeah, that hand propping thing is great for nostalgia and all, but I'm sure it will bum me out after say a month or so.

It's not too bad for general flying but is a major pain in the ass on cross countries. I often times have to push it hundreds of feet to find a place to tie it down.

 

[valittu]

I often times have to push it hundreds of feet to find a place to tie it down.

That reason is even worse than the actual hand propping. How exactly do you release it after it's started? Dennis Harbin in the EAA webinar talks about using a glider release installed on the tail. Still, that seems like too much of an opportunity to screw up.

 

[JHW]

buy the william wynn book and read it, to at least understand the corvair option before going continental. I like the corvairs, they are smooth-running 6-cylinders.

 

[valittu]

buy the william wynn book and read it, to at least understand the corvair option before going continental. I like the corvairs, they are smooth-running 6-cylinders.

I thought about the Corvair. They're beautiful conversions as far as I can tell. I'm just not sure how complicated it gets to install it and maintain it. The Fly Baby was born with a Continental on it's nose, which means fewer complications for this first time builder.

 

[wanttaja]

I often times have to push it hundreds of feet to find a place to tie it down.

That reason is even worse than the actual hand propping. How exactly do you release it after it's started? Dennis Harbin in the EAA webinar talks about using a glider release installed on the tail. Still, that seems like too much of an opportunity to screw up.

I flew the prototype Fly Baby for ~7 years, no starter. It had a glider hook, and whenever I flew anywhere, I kept my eyes out for an empty tiedown spot. I also carried a hank of rope and a knife, and would cut off my own rope to tie to something if necessary.

...Only became necessary once, when the tiedown ropes at an airport had been left in the sun and broke into powder at a slight tug.

In that seven years of flying, I only had prop it untied-down twice...once when the engine went asleep on approach on a 15-degree day, the other when I stopped at a remote field and didn't have anything convenient to tie it to.

The tail hook was kind of fun really. I'd start the airplane, climb in, bolt myself down, and there'd be someone there waving frantically to tell me the tail was still tied down. Wave back, reach down, and Ka-Chung....release the hook.

Here's a write-up on tail hooks:

http://www.bowersflybaby.com/tech/tailhook.html

Now, with THAT said...I'm quite a bit older than the days when I flew N500F. I've gotten spoiled by the starter on my current Fly Baby. I'd probably not go that route again.

Ron Wanttaja

 

[wanttaja]

Yeah, that hand propping thing is great for nostalgia and all, but I'm sure it will bum me out after say a month or so.

Well...got to say that I did enjoy it, for those seven years with N500F. It did seem to freak out a lot of people. N500F's C-85 was really set up nice, started on the first or second flip most of the time.

Wasn't quite so fun when the ground was slippery, or when the engine was hot on a hot day. Me and a fellow chapter member once spent about 15 minutes trying to get it going....

Ron Wanttaja

 

[yakdriver]

It's a bit ironic... on my last post, I'd actually wrote, "The Rotax 912 is a interesting possibility..." then wimped out.

I have no experience with the engine, but I figure it's common enough now to not be much of a risk. I attended a 3-hour Rotax-engine familiarization class a few months back, and liked what I heard.

THAT said, we get to the reason I wimped out: Installing a Rotax 912 on a Fly Baby has basically the same installation challenges as a car engine. New mount, having to figure out the radiator location and coolant tank locations, plumbing, etc.

It's doable...and considering the Rotax's inroads in aviation, probably the best alternative to the Continental.

But it still puts a big load on the builder to solve a bunch of non-airframe challenges.

Lemme put it this way: The Fly Baby plans are 256 pages (standard 8.5x11 paper). Only about ~15 pages deal with the engine installation, mostly about how to route the controls and gauges. It doesn't have a ton of details, because Pete Bowers figured that builders would just go down to the local junkyard and pick up a Cub FWF for $800.

For someone to install an alternate engine, they'd have to re-create all the step-by-step details of this legacy.

Again, if someone is technically competent and/or is looking forward to the challenge of adapting a non-standard engine, more power to them! But most people who talk to me about alternate engines want them because they're cheaper or "easier."

I've been flying Fly Babies for about 25 years, both airplanes with C-85 engines. In that time, the "engine" problems I've had to deal with are:

1. Leaking exhaust valve (IIRC, about $400 ~20 years ago...First annual).
2. Shattered center conductor on magneto (replaced with "button" from VW bug distributor)
3. Leaking/cracked exhaust systems
4. Cracked cooling "eyebrow"
5. Starter clutch needed replacement (~$500).
6. Generator failure ($80 and "don't tell me what it's from" at the auto electric rebuilder)
7. Bad regulator ($25 at Arlington Fly-Market)

I do not consider this THAT onerous for 25 years/800 hours of fun (there are a ton of electrical system issues in here, but that's not related to the engine).

And... my current engine (bought with 25 SMOH) has about 600 hours and 20 YEARS since major overhaul. The hours ain't bad, but being 4x past the Continental time limit does tend to prey on my mind. I'm springing for a new exhaust system in the fall, and have started to think about an overhaul (Don't live that far from Tom Downey, and I've got an A&P buddy who rebuilds engines for folks and also owns a Fly Baby).

So... I may be springing $5Gs or more for a rebuild, and the alternate-engine folks will nod sagely and say, "That's the problem with those Contintentals." But if the $5Gs buy me another twenty-five years of reliable flight, I figure it's worth it....

Ron Wanttaja

If your engine is running fine and not making any metal I would just fly it. I just went through "freshening up" a C-85 on a friend's C-140. He bought the 140 with a mid time engine that was running great. It had brand new cylinders with 30 hrs on them and he decided he would do the O-200 crank conversion as he flies out of Nampa Idaho and likes to go into some of the backcountry strips. Aircraft Specialties has the conversion kit with new crank, reconditioned rods, pistons and rings. The simple conversion turned into the nightmare as after the engine was apart the cases had to be replaced, cam could not be ground, corrosion on several of the gears and several other things. Now these things were not a sign of an impending failure they were all below limits for an overhaul. Even knowing all that the engine builder said it probably would have run fine to TBO or beyond. Also yours being a homebuilt you can get away with perfectly good parts that are not serviceable for a certified airplane. Also a lot of stuff like a cam is really hard to find. Haven't run it yet but should be a great engine now with about everything brand new. So be ready to triple your $5000 estimate for a rebuild. Don

Here is the 140 with the new engine.

 

[wanttaja]

If your engine is running fine and not making any metal I would just fly it.

Yeah, you're probably right. No metal, runs strong, uses a quart every ~3 hours.

The trouble is, I've got some oil leaks. The actual rate of loss is low but oil is like blood, a little bit oozing here and there looks awful. And the cowling is painted light cream, so it really shows. My Dad hated oil leaks with a passion (my parking a '46 Willys Jeep in the driveway didn't help) and I guess I'm taking after him. Paper towels are cheaper than overhauls, but I hate having to go up front and buff the beast down every time I stop somewhere.

I need a cowling sticker: "Pratt & Whitney in Training!"

Ron Wanttaja

 

[Henning]

That reason is even worse than the actual hand propping. How exactly do you release it after it's started? Dennis Harbin in the EAA webinar talks about using a glider release installed on the tail. Still, that seems like too much of an opportunity to screw up.

There's a couple different slip bight knots you can use so you can tug the tail of the knot from the cockpit and release.

 

[yakdriver]

Yeah, you're probably right. No metal, runs strong, uses a quart every ~3 hours.

The trouble is, I've got some oil leaks. The actual rate of loss is low but oil is like blood, a little bit oozing here and there looks awful. And the cowling is painted light cream, so it really shows. My Dad hated oil leaks with a passion (my parking a '46 Willys Jeep in the driveway didn't help) and I guess I'm taking after him. Paper towels are cheaper than overhauls, but I hate having to go up front and buff the beast down every time I stop somewhere.

I need a cowling sticker: "Pratt & Whitney in Training!"

Ron Wanttaja

The flange on the oil tank is a notorious spot for leaks. Check to make sure the surface is true (probably not) and there are no cracks in the welds (probably are). weld up the cracks and true it up on a mill. Replace all the accessory case gaskets and the mag gaskets. Might also do the front seal while your at it. I like to use Tite Seal on the gaskets. Really gooey stuff but works great and doesn't harden up. Don

 

[Henning]

Yeah, you're probably right. No metal, runs strong, uses a quart every ~3 hours.

The trouble is, I've got some oil leaks. The actual rate of loss is low but oil is like blood, a little bit oozing here and there looks awful. And the cowling is painted light cream, so it really shows. My Dad hated oil leaks with a passion (my parking a '46 Willys Jeep in the driveway didn't help) and I guess I'm taking after him. Paper towels are cheaper than overhauls, but I hate having to go up front and buff the beast down every time I stop somewhere.

I need a cowling sticker: "Pratt & Whitney in Training!"

Ron Wanttaja

An ounce of oil spreads a heck a long way doesn't it...

 

[jesse]

Yeah, you're probably right. No metal, runs strong, uses a quart every ~3 hours.

The trouble is, I've got some oil leaks. The actual rate of loss is low but oil is like blood, a little bit oozing here and there looks awful. And the cowling is painted light cream, so it really shows. My Dad hated oil leaks with a passion (my parking a '46 Willys Jeep in the driveway didn't help) and I guess I'm taking after him. Paper towels are cheaper than overhauls, but I hate having to go up front and buff the beast down every time I stop somewhere.

I need a cowling sticker: "Pratt & Whitney in Training!"

Ron Wanttaja

No reason to jump to overhaul because of some oil leaks, do the UV dye test I suggested. You'll likely knock most of them out in a weekend. Trying to fix them without figuring out where it's coming from 100% is a giant waste of time, believe me, I've been down that road...

 

[Henning]

No reason to jump to overhaul because of some oil leaks, do the UV dye test I suggested. You'll likely knock most of them out in a weekend. Trying to fix them without figuring out where it's coming from 100% is a giant waste of time, believe me, I've been down that road...

The fluorescent dye test is a good one. If you haven't changed the oil cap gasket, may as well start there when you pull the cap to add the dye lol.

Many times persistent leaks come from the case seam, those are really tricky-impossible to get sealed without splitting the case, and usually require machine work. Most any other leak is fixable in a half a day (plus whatever time for welding/getting replacement part).

 

[wanttaja]

The fluorescent dye test is a good one. If you haven't changed the oil cap gasket, may as well start there when you pull the cap to add the dye lol.

Yep, got a spare gasket. Also picked up a dye kit last weekend.

Many times persistent leaks come from the case seam, those are really tricky-impossible to get sealed without splitting the case, and usually require machine work. Most any other leak is fixable in a half a day (plus whatever time for welding/getting replacement part).

I know I've got minor leaks on two pushrod tubes. They're on the case side, though, which means the cylinder has to be unbolted. With the engine running so smooth, I'm kind of loath to do that.

The thing that bugs me the post is that oil oozes out the FRONT of the cowling after shutdown...14 inches or so forward from the leaky pushrod tubes. Oil drools down the interface between the top and bottom of the nose bowl. That's what was originally had me thinking the problem was the front seal.

Ron Wanttaja

 

[jesse]

Yep, got a spare gasket. Also picked up a dye kit last weekend.


I know I've got minor leaks on two pushrod tubes. They're on the case side, though, which means the cylinder has to be unbolted. With the engine running so smooth, I'm kind of loath to do that.

The thing that bugs me the post is that oil oozes out the FRONT of the cowling after shutdown...14 inches or so forward from the leaky pushrod tubes. Oil drools down the interface between the top and bottom of the nose bowl. That's what was originally had me thinking the problem was the front seal.

Ron Wanttaja

If I do a few hours of flying in a day there is no doubt I'm going to have some oil to clean up. Not nearly as bad as it used to be after I went on the last leak fixing mission. Also not bad enough for me to care right now.

Really it's amazing these damn things don't leak more than they do.