Continental 65 HP or more, Ok on Model 4 ????

[rogerh12]

Howdy Gang;

Does anyone know of someone that has installed a Continental 65 HP on a KItfox-4-1200, or perhaps something bigger, like the C-85?

I think the 65 HP version would provide enough power for a 1050 Gross plane, but a 1200?? Would the engine just be too heavy for the noise, or to big to fit???

I think the A65 was much lighter than the C85 or 0-200, and they are fairly cheap, but I would want it with electric start, if it's possible to get one that way.

I am considering this, or the new 2300 cc VW conversion.

Let me know what you think !!!!

Roger

[jtpitkin06]

Roger,
We get this question every four weeks or so. “What do you think about using an XYZ engine in the Kitfox?”

First, you need to know the answer to, “What is your motivation for using an alternative engine?” The term “alternative” here applies to any engine not directly supported by the factory.

Most of the time, it is cost. Many times the builder already owns an alternative engine and thinks it might be a good match for the Kitfox airframe. Sometimes it may be someone on a budget who is trying to build a Kitfox cheaper than when using a Rotax.

Sometimes, the reason is brand loyalty. You may just prefer Continental or VW over Rotax. In that case there is no amount of logic that will sway you.

When installing alternative engines there is more than the cost of engine acquisition. There is the firewall forward issue.

Be aware, there is little factory support for most of the engines you mention. You will need to find a suitable cowling to modify as the length will not be the same to the spinner plate. You are on your own for the engine mount, the firewall, all of the firewall forward accessories, baffling, and fitting the cowling. If your starter bumps the fiberglass, don’t call the factory and ask how to solve the problem. It’s not part of a package they sell and you can’t expect them to do the work for you. You will need to fabricate an exhaust system, intake system, carb heat box, and more.

If you decide to use an alternative engine, you need to be quite focused on your choice and have solid reasons for not using the Rotax. If cost is the motivating factor and you don’t already own an engine, you may be surprised at the final expenses. You indicate you can get a used Continental for cheap. Be sure to include the cost of overhaul or compare your used engine to the price of a used Rotax, then plug in the above firewall forward expenses.

Are you considering this engine for a new airframe or swapping a Rotax two stroke out of an older airframe? The current Model IV is designed for 80 to 100 hp. It is a completely different fuselage from the early Kitfoxes that flew with lower hp motors. Read the Kitfox history to understand the evolution.
If you are considering this installation in a new Classic IV, you should look seriously at something with an appropriate power rating. The 65, 85, and 90 Continentals do not have the power to weight performance to warrant their installation and you seriously degrade the resale value of the aircraft.

Know the answer to, “What is your attraction to the Continental over the Rotax?”

Next, you bounce over to the VW campsite. What is your attraction to VW over the Rotax?

Yes, almost any engine in the 100 hp range will fit inside one of the larger smooth cowlings. Very few will fit inside the round cowling because of width at the front.

Are alternative engines too heavy on the nose? If you do some homework you will discover Kitfoxes flying with O-200s, Lyc O-235s, Subaru EA81s and others. A Rotax equipped Kitfox has the engine mounted pretty far forward. There is a lot of room for a shorter engine like the Continental to shift aft.

All the weight and balance information is freely available. If you know your engine weight and dimensions you can accurately predict the CG. If this is beyond your capability I would not recommend your pursuing the project.

All of the above is not just an opinion; it is actual experience. I am installing a Corvair engine in my Model 7SS. As one who has done this I can tell you it is not an easy task fitting a cowling and engine mount for an alternative engine. The windshield, glare shield and cowling all must join together and fit flush at the base of the windshield. The cowling front end spinner height and depth must match the engine. Any clearance issues are problems you must deal with alone. Your custom mount must hold the engine at the proper height, depth, angle, and not interfere with intakes or exhaust. Everything under the cowling is custom fitted.

This is not to say it can’t be done. It can be done and can be very rewarding at the same time. Engineering the components is part of the challenge. However, if you are even the least bit weak in being able to design components, systems and solve mechanical problems using aircraft quality standards and techniques, I recommend you stick with one of the supported engines.



John Pitkin
Greenville, Texas

[rogerh12]

John;



I guess the VW is now an offically supported engine, at least on the Kitfox model 3 & 4. I say this as Great Plains VW has a firewall forward kit for the kitfox, which includes Engine, Engine mount, Intake, Exhaust and aftermaket cowling (made by a guy in WI), all predesigned to work together. There are also several flying examples I have seen on the internet anyway.

I have used the VW in a few planes before, and am familar with it's strenths and weaknesses, and issues in installation and cooling. It's probably the way I am going right now with my model 4, however, I guess I am really asking more about A65 or C-85 installs, and how well that worked out.

Thanks again

Roger

[rogerh12]

Avid Flyer;

I am not knocking the 582 as an option for people, I had one on my kitfox model 2 and yes, it had good power, light weight and I really didn't have to do anything two it, mechanically. It was also the heaviest engine the airframe could take, and still have a decent payload. Having said that, I have other two stroke engines on motorcycles, boats and others things and have learned some things about two strokes.

1) They fowl the plugs and can be very had to start.
2) They typically have only one or two cylinders, and if one goes out, you’re not going anywhere (or worse)
3) They drink fuel like mad.
4) They need Oil and Gas, and without oil in the fuel (such as when my oil injector pump failed on my Yamaha RD 350 at 60mph) the engine will suddenly seize.
5) Water cooled two strokes can seize if cooled too quickly (that’s how I acquired my kitfox, the owner had a hard landing after he shock cooled the engine in a power off decent, it seized on him.)
6) They rev high and wear out fast, loose compression or shell out the roller bearings and maybe send the rod through the case
7) The sound funny, make lots of smoke, get oil on everything and smell bad (and are just messy)
8) Are expensive to fix (compared to a auto 4-stroke)
9 ) Require special mail order parts (can’t just go to NAPA).
10) And Finally, they quit running too easy (I.E. part of the tuned exhaust falls off and the engine dies).

Though any one of these reasons is not enough to make me go 4-stroke, combined into a group of 10, and installed in an airplane I will be flying, they are enough to make me go 4-stroke. I understand 4-strokes are not an option for ultra light aircraft, but the kitfox-4-1200 has the capacity for something heavier, with better fuel economy, lower cost, over all reliability and perhaps more power.

Of course, all comments are welcome.

Roger

[HighWing]

All good comments. I especially liked John's thorough review. One thing possibly was not mentioned - performance. I doubt there is an optional engined IV out there that will even be close to one with a 100 hp ULS or even the 80 hp 912 UL. John has gone through the engineering and his advice is definitely worth a listen. The factory supported a Subaru conversions when I was first building. I considered it - this was back in 1995 or so. There is a long histrory in auto conversions in the Kitfox and a few are still flying with their original builders. I am in the relatively final stages of a IV project and it will have a "previously owned" 912 UL - 80 hp. It was a 150 hour engine in a pusher style home built that fell out of the ceiling - literally - in a shared hangar. Being high mounted there was no prop strike. No S for me as I can't justify the cost. The old money thing. And the S model is not entirely without issues. My guess is that I will have right at $12 or $13,000 in front of the firewall. And based on almost a thousand hours in a previously owned 912 powered IV, I expect it to perform quite well.

As an aside, I put in a year and a half helping a friend who was building a Lancair IV. When he had it signed off, the inspector was a close to retirement FAA guy that had spent a career in Alaska as an accident investigator. His favorite subject was the otherwise survivable crashes that turned into fatalities due to the missiles (baggage) stowed in back. The most striking - no pun intended was the fishing pole that impaled a passenger in an otherwise survivable crash. How does this relate to the current discussion? It was common practice in the old days to put a heavy battery in the tail secured with adel clamps to bring the alternative guys into W/B compliance. Be careful

Lowell

[rogerh12]

Lowell;

I myself am not a fan at all of batteries in the tail cone. I think they should, if at all possible, simply go on the firewall. After you add up all the additional weight for extra length cables, thicker cables and a larger capacity battery required to install a battery in the tail cone, you lose most if not all advantages of having the batteries back there.

I think a better idea, and the one I have gone with, is to install a small battery on the firewall, with short cables. This creates a simple and light weight install, that can still efficiently deliver the Amps to the Starter on cold days. Doing this way, I am probably looking at half the installed weight as compared to a remotely installed battery. Then, I take the weight I saved, and place it as far aft in the tail as possible, to be used a counter weight to the engine. Handling the battery this way should give me the same installed weight as doing it by placing the battery in the tail cone. But the really beauty of doing it this way is that I can easily add just the right amount of counter weight to shift the CG back into spec, and not an ounce more (I have a plate welded just forward of the tail spring mounting bolts, I install lead “rounds” on it to act as counter weights).

CG way out of spec? Fine, just add more counter weights, a simple and quick fix. Yes, the plane might weight a few more pounds more when I am done, but then again, probably only a few. For me, that ease of control over the CG is worth a couple extra pounds, and the peace of mind knowing I can fix a noise heavy engine install in a matter of minutes, if needed . This is of course a lot different than trying to fix a recently completed kitfox with a CG problem by trying to move the battery all around the fuse, just to find out it’s still not enough.

Would you agree?

Roger

[t j]

"Big Engine Builder's Beware"
An article with this title was published in the old "The Kitfox Builder" news letter in September 1995. It caught my attention and I think of it every time I hear someone talk about putting weight far back in the tail of a Model 4 to balance a heavy engine.

If you are considering putting weight in the tail, do the math on the moment of enertia. The formula is Moment arm SQUARED times weight.

Here's the article by Tony McWhorter.


I am enclosing this article from IAC magazine (Sport Aerobatics) 1/94. I think it needs to be read because of the amount of modifying now being done on the S5 aircraft with the larger and heavier engines. I do not want to become the bearer of bad news, but I feel this could be a life or death concern. I have taken excerpts from the article because of time restraints.The article is titled " It's Where You Sit..." by Fred G. Delacerda "The airplane was observed to enter a spin during the half roll at the top of a Immelman. There was no recovery from the multi turn spin. Accident investigation and analysis failed to find a problem with the pilot or the airplane that would prevent spin recovery. The NTSB computer print out of the accident causal factors read as follows: Aerobatics<>Performed<>PIC Stall/Spin<>Inadvertent<>PIC Emergency Procedure<>Not Correct<>PIC The certified aerobatic airplane was a tried and proven airplane. Like most airplanes the cockpit layout had been designed for the 50th percentile adult. Therefore, a pilots position in the seat ( also weight and position of engine) can put the airplane on the front or the aft end of the CG range. With the 95th percentile pilot the CG is in the extreme aft position and the airplane is sensitive in the pitch whereas the 5th percentile pilot has a forward CG position with an airplane very stable in pitch. Consequently, the pilot wanted to move the CG aft. Adding weight behind the seat would work but the amount needed significantly added to the weight of the airplane. So it was decided to add the weight as far aft as possible so as to have a large moment arm with a small weight. Through trial and error a weight of 7.5 pounds was attached to the tail post. A check of the weight and balance found the CG to be within limits. What was not readily apparent was the alteration of inertia. All pilots are familiar with moments, but few are knowledgeable about the moment of inertia. Moment of inertia depends on the shape and distribution of mass about the axis of rotation. A moment is calculated by multipling the moment arm times the weight, but for moment of inertia it is moment arm SQUARED times the weight. A small weight with a long moment arm signficantly alters the moment of inertia. Now more aerodynamic force from control deflection is needed to overcome the increase in moment of inertia. It is possile to have a moment of inertia so large there is not enough aerodynamic force from the control surface at full deflection to overcome the inertia. In this particular case the pilot had stayed within the envelope but a created a significant change in moment of inertia due to the long moment arm from the CG to the weight on the tailpost. In the spin, a airplane goes from a transitory to a rotatory motion. During the transitional stage, the incipient stage, the aerodymanic forces and the inertia forces are developing. When in the developed stage of the spin these forces are in equlibrium. During recovery, control changes provided the aerodymanic forces needed to offset the inertia forces. In this accident the inertia had been changed to the point that aerodymanic forces from control imput were not sufficient to overcome inertia. This had not been noted by the pilot as he had always kept within the incipient phases of the spin where inertia forces were not fully developed. In this stage, control deflection produced aerodymanic forces sufficient to stop spin rotation. With an inadvertent entry into the spin from the Immelman, the pilot allowed the airplanes to progress to the developed stage of the spin where spin recovery was not possible. The human factor chain of events were as follows. The CG was adjusted by addition of a small weight at the extreme aft end of the airplane that significantly altered the moment inertia due to th long distance from the CG to the attachment point. Because of the alteration, recovery from a developed spin was not possible since there was not a sufficient control surface for aerodynamic forces to overcome the inertia. An inadvertent spin was allowed to reach the developed phase. With no recovery possible, there was a fatal crash. Training in spin recovery would not have prevented this accident" I hope everyone understands my concern on this subject. Thanks Tony

[HighWing]

I think I do tend to agree on the battery back there issue, but the real intent of my note is a reminder that there can be many consequences to the decisions we make as builders. An engine choice requires inquiry into more than HP and $$. The post from Tony illustrates that. I know of one Model IV that was completed about the same time my first one was in 1998 or so and it sits in its hangar with about 20 hours on the Hobbs. It had the then available NSI EA 81 Subaru. It simply is not fun to fly. The one thing that stands out to me from the Ed Downs book - How TO Fly a Kitfox was his note that the Kitfox is a high performance airplane. That statement might sound a bit goofy to a RV or Lancair pilot, but these little puppies configured right with a focus on empty weight can become real screamers in their class.

It all depends on what your ultimate goal is. If you want an agile fun to fly, back country capable airplane, go traditional and go light. If you want a fun project with lots of challenges and the satisfaction that goes along with overcoming them, then go for that. Personally, I see no harm in that, as that is my basic nature as well, but go into it with eyes wide open.

http://www.youtube.com/watch?v=l5X-aJoCbC8&NR=1 Follow this link to a RV taking off from Johnson Creek, Idaho. On the far departure end check the notch on the mountain bordering Johnson Creek. Most airplanes departing after leaving the runway snug up to the right hand side of the ridge bordering the river to take advantage of the ridge lifts. A Friend's Model IV with 80 hp 912 made a straight out flying over the notch.

Lowell

[rogerh12]

Tom and Lowell;

Thanks for all the comments, lots of factors to consider when firewall forwarding a plane, and not just the firewall forward considerations either.

Regarding the increase in rotation inertia; Good point, and I think it is understood at this time, if it’s not common knowledge anyway, that the Kitfox-4 has an elevator that is somewhat undersized, especially when operating the plane with a forward CG and with full flaps. So increasing the rotational inertial with respect to the pitch axis would seem to be a big mistake. The fix, well certainly, Kifox will sell me a bigger elevator (for about $500+ delivered), but being somewhat cheap, I have looked into other options.

With respect to the elevators lack of control authority, I have looked into ways to increase the stock elevators effectiveness. Certainly, the first thing is adding gap seals, it’s seems to be the easiest and most common mod, plus seems to give the biggest gain for the buck. The second is limiting the travel of the flaps to 50% max range, and making up for the reduced stall speed with vortex generators. Also, vortex generators can be added to the bottom of the tail feathers to increase elevator effectiveness, or so some people say (this is not common). Of course, setting the horizontal stabilizer to a slight negative angle reduces the down force required by the elevator at any particular mode of flight, thus making the elevator more effective at maximum up defection. Finally, by adding weight to the tail and shifting the CG back, the elevator now requires less upward defection to hold any particular positive angle of attack, and produces more net down force at full defection.

Certainly, just adding weight to the tail does change the pitching characteristics of the aircraft, but tried and true methods of compensation are available and could be utilized with the Kitfox.

Final note: With my counter weight design, the amount of weight is adjustable, so the pilot, upon flight testing the aircraft, could decide to remove the weight and continue to fly the plane with a somewhat forward GC, as long as good elevator control is available, even with flaps at max. The point is, that this particular option is available, at least with my design modification.

But really, why all the trouble? Why not install a Rotax 912 and be done with it. Well for one, I installed a complete Revmaster firewall forward on my Sonerai for about $3000, and that included a new wood propeller. Yes, it was a used engine, and I had to do a rebuild on it, but it had dual ignition and the engine rebuild cost on it (for parts) was only about $500. Enough said?

[jtpitkin06]

And just for a “what if” question:

What if the original Kitfox was designed as a Model 7SS with a Lycoming O-235 as the standard package? Would there be so much chatter if some owners were installing a lighter Rotax?Would we be getting posts warning the Rotax is too light and we might have to put weight in the nose?


John Pitkin
Greenville, TX

[szicree]

Final note: With my counter weight design, the amount of weight is adjustable.

I think the point of the post about moment of inertia was that the aircraft might find its way into a a spin and be unable to recover. I suspect an aero engineer could tell you roughly what the impact of the extra pounds in the tail would be without having to try it out first. Any such folks on this forum?

[MotReklaw]

Question.

What engine was the models 5-7 designed for?

Thanks,

[rogerh12]

Oh gosh, maybe I should have mentioned something important.

My Kitfox-4 does not have a tail wheel or the speed tail kit. That's right, I have converted it to a noise wheel plane using the factory noise gear kit and yes, I know this does not make it a REAL kitfox to some, but it sure looks sweet !!!!

The point being, my tail is light. Maybe, I don't know 5-10-15 lbs? So really, I guess I have room to add weight to the tail. Plus, the main wheels get moved back with the tri-gear, and I am going to a spring gear and WT600 wheels which weight more than stock. How all of this will affect the CG, I am not sure. Also, the Kitfox VW engine mount is supposed to place the engine in the right location, but the weight of VW engines varies, as does the disbursement of the weight (I.E. do I have magnetos at the back of the engine, or a distributer and secondary ignition at the front of the engine.)

Having the option to easily add weight to the tail adds peace of mind to me, but in the end, my tail, even with extra weight added, still might be lighter than a fellow with a honking aftermarket tail spring, tail wheel and speed tail kit installed.

Or not.

Roger

[HighWing]

John,
I think you got this spot on. I have a model IV and a Series V in my hangar and the V, as I understand it, was designed exactly as you suggest as a possible platform for the O-235. The fix is relatively simple going from heavy engine to light by simply changing the location of the engine. My hangar examples - the IV with 912 with the engine four inches forward of the firewall measured from the right air filter flange and the V with the engine (912S) 13.5” forward of the firewall. Actually, my IV has the engine 6.5 inches forward for similar reasons that you suggest. I installed full gap seal cuffs on both horizontal and vertical tail surfaces and even though I vacuum bagged everything for weight considerations, I still calculate that with trim servo motors for both elevator and rudder – elevator with trim tab and rudder by warping the two bottom ribs, I added about six pounds at about a 14 ft. arm which suggested moving the engine about 2.5 inches forward. That helped accommodate a better located oil tank as Model IV pilots will understand. I did the empennage thing on my first Model IV and had to placard the baggage sack at 25 lbs. rather than the 40 lbs. in the design because of my new tail weight.
There was a recent thread on extending the length of the airframe. That would help with a heavy engine as it would fit into the same thinking as extending the length of the engine mount.
With your SS and the Corvair,there is probably not nearly the issue, as you have room to reposition your engine aft. With the Model IV, unfortunately there is no room for a more rearward positioning of the engine - ballast is the only option, and this is the issue at hand.
As another aside, I made some U shaped pieces of 1/8” rod, threaded on each end and glued into the channel on the forward side of the door post. These were to secure a thin piece of aluminum to cover the wires that run from the panel to the bottom of the door then aft. I showed them to a friend (Model I and three Model IVs and a Rans S-7) and asked his thoughts. His response was, “heavy”. It seems we all have a mission in mind for our projects.
Lowell

[jtpitkin06]

Question.

What engine was the models 5-7 designed for?

Thanks,

From the Kitfox LLC site under History

"In 1994, SkyStar aircraft was faced with an increasing demand to produce a significantly larger version of the Kitfox that would be able to utilize contemporary certified engines (Continental and Lycoming) in addition to the Rotax 912 engines. The answerer to this demand was the entirely new Kitfox Series 5. While appearing very similar to the Kitfox Classic 4, it is, in fact, a completely new design."

[jtpitkin06]

Lowell,

I'm working on the engine mounting and cowling for my Corvair at this time. It's a matter of all the components coming together. Windshield, glareshield, cowling and engine. I made a wood mockup of the engine and prop hub. It helps determine the placement of the other items and getting the cowling right. The mockup is a lot easier to wrestle on and off several times than the engine.

The engine is mounted just 4 inches from the firewall. I can't go further aft due to the foot wells that protrude into the engine compartment interfering with the intake manifold. I see on the Rotec radial Kitfox they left off the foot wells.

The Corvair engine is just 26 inches long. The prop spinner backing plate is 30 inches from the firewall. That is aft of where the Continental prop hub is located so i have to cut 4 inches out of the Continental cowling to match the Corvair spinner.

I'm putting in some extra effort to get a straight horizontal cut line on the cowl to match the fuselage side stringers. That will eliminate the bent fuselage look.

It's all part of the fun.
John

[desertfox1]

Um.. no John, the Kitfox Radial has foot wells. When Prokes
and I did the molds for the cowlings they sent down a stock
Rotax firewall and the new engine mount. You may have seen
a picture of a builders plane before John did the factory
firewall forward.

By the way, are you using a boot cowl? I have found it quite
helpful when adapting cowls to the Kitfox. I'm very interested
in your build, spent some time with William at Osh.

Phil, DesertFox1

[jtpitkin06]

Hmmm... must have been another Radial.


Yes, I'm doing a boot cowl. I'm slicing the Continental cowling in parts. The upper half gets split at the firewall to make a bonnet and the lower half get sliced at the side panels. The side panels will be glassed to the bonnet. Then the forward sections get shortened to match the spinner flange to the engine.

This should make it easy to pop the forward cowling off while keeping the cockpit sealed.

JP

[rogerh12]

Ok, I just checked with an Aerospace engineer on the question about effects of increasing the rotation inertial on the Kitfox-4 by adding weight. I even showed him my plane with the weight bolted in to the tail, as I have been fitting them to the bare fuse in my garage. Bet you didn’t know Aerospace engineers make house calls !

Actually, he stopped over to pick up a rental application on my duplex (where I live next door), and happened to mention he just got a job at the University as an Aerospace engineer. What Luck !
As it turn out, part of my rental application includes the need for tenants to mow the lawn and to analyze my Kitfox design modifications (it’s in the fine print).

Ok, so in short, this is what he said. Though until he does a calculative analyses on it, he can’t be sure, but basically the mode of flight where someone could get into trouble by having increased the rotational inertia of the plane (by adding weight to the tail) is very much aerobatic. And the main issue would be controlling an established rotation in the pitch access, at reducing airspeeds, such as when someone does a sudden pitch up maneuver (such as the Lomcovák). Obviously, this is a mode of flight that the Sunday kitfox flyer is not even going to approach, thus it should not be a concern with the kitfox.

He did however point out one thing I had not thought about, because my Kitfox would be switching from a geared down rotax engine to a high rev’ing direct drive VW engine, the prop blast velocity will be higher on the tail and thus likely providing greater pitch control at slower speeds, if full throttle is applies.

I hope he does move in, I have more questions for him already !
(oh ya, maybe you guys could slip in a few too !)

[kitfoxnick]

Pardon me if this sounds stupid, but doesn't the gearing down of a rotax make the prop rpm close to that of a direct drive. What rpm range does a vw direct drive run at?

[DBVZ]

3400 or 3600 depending on which one. Or so the web site says. It is interesting that the reduction gear results in an increase in thrust. 3600 RPM means the prop length is limited to keep the tip speed under limits (fixed pitch, wood). Interesting stuff. Lots to consider in picking an engine and prop combination. The engine MFG says the VW direct drive requires a wood fixed pitch, so if you really want a ground or air adjustable you need to consider other combinations.

Front Drive - Air-Cooled.
Direct drive, driven off the pulley end (Type 1 only) for standard aircraft configuration. The Front Drive engine turns counter clockwise from the cockpit in a tractor configuration. Wooden props ONLY must be used. This is the most popular configuration.

And here: http://www.greatplainsas.com/gpasproducts.html

[HighWing]

John,

Please make the boot cowl removable. With the windsheild in place and the boot cowl riveted in place, the only way you can get behind the panel is to either remove it or slither in on your back. Shades of the Lancair IV. When I was helping with that I excused myself from that chore - no real choice. And with the V my buddy is building in my hangar - he insisted on a removable boot cowl - genius. I think I would use nutserts and easy Loctite though, rather than screws and nuts.

Lowell

[jdmcbean]

Hmmm... must have been another Radial.


Yes, I'm doing a boot cowl. I'm slicing the Continental cowling in parts.

JP

John,
Give me a call.. we now hove a boot cowl that should work fine on the Continental and Lycoming installs:)

While the older instructions call for riveting the boot cowling to the firewall.. we currently use a sealant and c'sink screws for mounting the boot. It works out well.... Accessing behind the panel is much easier without the boot installed so waiting until the last minute to install it can be helpful. Once installed access ins't too bad from under and over the glare shield... and if absolutley needed the boot can still be removed.

[rogerh12]

It's offical, I got my Aerospace engineer next door !
Now that he is my renter, look for a few changes to the Kitfox-4,
such as turbine power !

[DBVZ]

I seem to remember an STC for the Continental, that involved a cordless drill motor, a gear mounted on the prop flange, and a control rod to the panel. Something like $1800 for the STC, for about $300 in parts, and good for about 4-6 starts on a charge.

[rogerh12]

Ya, I too have seen mods to add starters. The guy in the hanger across from me hand props his O-200, and thinks it's no big deal, but for me ..... Well ?????

I guess I am still exploring options. The C-85-12 might be a better choice, and weight about the same after putting a starter on a A65, but then it really would be too much weight I think (or not?). Perhaps I should try hand propping another plane, and see if it's something I could live with, or not. So I guess right now I am still looking at VW'ing it, at least I know that devel, and the install weight with starter is still only about 165 lbs (+ accessories). !!!!

Thanks for the insight guys

Roger

[Av8r3400]

I've been watching this thread to see where it goes. Just a couple of thoughts:

Hand-Propping: I have a good friend with a Champ. C-85 with no electrics. It props nicely and works fine in that plane. Keep in mind, that plane was designed for the (220# +) weight of the Continental.

VW motor: With the rpm range they need, they will not have a large enough propeller (low speed, high thrust) to make this airframe perform anywhere near acceptable. VWs work in a Thatcher or Sonex, but I have never heard of anyone even remotely satisfied with one in a Avid or Kitfox. Not to mention their actual reliability record is at best, spotty.

Continental (C-65 through O-200) in a model IV: IMO generally a bad idea. This motor even without electrics is too heavy. This airframe was designed around the 582 Rotax (~90#). The 912 is a good substitute (~140#). Anything more is too heavy, period. A friend of mine had a Subaru in his IV and once all the ballast that was needed was added to the tail, he had a poorly performing single seat airplane. His install was at about 230 pounds.

Finding a used, reasonably priced 912 is not impossible. Another friend of mine just bought one (80 hp 912UL, 120 hours TT) for $6500.


Innovation is a good thing. But in this case, IMO, you will be very disappointed in what would otherwise be a great little plane.

[DBVZ]

VW motor: With the rpm range they need, they will not have a large enough propeller (low speed, high thrust) to make this airframe perform anywhere near acceptable. . More discussion on this point, please. Someone with a VW powered Kitfox or Avid want to rebutt? I saw one with a 76HP Great Planes, that reported climb rate of 1000 (solo) and high cruise of 115MPH (just about 100kts) TAS at 4500 - 5500. Is that not "acceptable" performance for a Kitfox IV?

[HighWing]

I bought my first Kitfox Model IV kit in 1993. I have no personal experience with VWs in IVs, but have been involved with foruns such as this one since 1994. (Early forums were email lists where we recieved every post and most of us read every one - 582, Subaru, Rotax, VW, Model I,II,III,IV,V 6,7, and learned a lot, even about stuff we were not particularty interested in.) Kitfox has been around a long time as have VW conversions. If it was a mix made in heaven, I doubt you would have to ask for a rebuttal, as the forums would be full of talk and Model IVs would be full of VWs as an option to the much more pricey Rotax. Av8r3400 is spot on in his comments from a historical perspective. The issue with the Model IV vs. the Sonex has to be with weight and prop length limits if direct drive and the round cowl blanking most of the prop, where the Sonex has a smooth cowl and lets the wind fly. This phonemenon is an issue also with certain prop designs - Powerfin on the Model IV.

I know there are guys that believe that they will be able to manage the issues, but, I am unaware that anyone has. You can be sure that if the combination works and works well, there would be tons of the good news on the internet. I must say here, though, that if there is someone out there who has a VW powered IV and it is a screamer, Don't keep it a secret. Let us all know and we skeptics will stand corrected.

Lowell

[rogerh12]

Howdy all;

There is a fellow on youtube with, like a dozen VW powered kitfox-4 videos. He is most well known, but other are out there too. Watching his videos, the planes sounds wicked (love that 4-stroke sound). I think the only issue is the rate of climb is not excellent, it's not bad either, just not that great.


I had a 76 HP Great Plains VW in my Zenith 601 HDS. The HDS has the taper wing, and the span is only something like 23 feet, so it has never been known as a great climber. I would take off at 1260 lbs gross in the summer, when it was HOT in Kansas, and still climb out at about 400 fpm. That might sound bad to you, but the Ercoupe I learned in would only manage 250 fpm !!!!!! I would expect the Kitfox-4, with it’s larger wing to climb at 600+ FPM under the same conditions myself, which is fine with me (didn’t the cub start out with a 65 HP engine ????)

VW aero engines are not the same, that’s for sure. I have seen some pretty crappy ones, but Revmaster, Great Plains and Aerovee are really first rate too. This zenith was a Great Plains VW with a good propeller. Your millage may vary, as they say, but a VW with 70-80 HP has plenty of power for something like a Kitfox-4-1200, the key factor is choosing the right prop. Something most people can’t do, or do wrong.

The VW propeller should have a largish diameter, and a somewhat shallow pitch in order to give a good static thrust and high efficiency. But it must have enough pitch to get you up to your projected cruise speed (don’t’ forget the prop slip !!!!), without over pitching the engine. Personally, I have a propeller calculator program that helps me, but most folks call propeller sizing a black art. Over propping he plane is the easiest thing to do (too much pitch or too much diameter). Usually, I order a propeller with the proper pitch (as calculated), but with a bit too much diameter. Then I install and test run it and check the static rpm at full power. Then I run the numbers through the calculator, and it tells me about how much to cut off each tip in order to bring the rpm up to what is needed. (oh ya, I sure wish I had adjustable pitch !!!!) This process typically takes a 2 or 3 attempts , but in the end the prop is dialed in and wholla !!!!! A perfectly sized VW prop !!!!!

As for VW reliability, once again, it depends on the VW. A factory built or a slopped together former airboat engine ???. I mean really, we have to compare apples to apples here, and I don’t’ think it’s been done. The VW engine has been used on airplanes for something like 70 + years now. It’s an extremely well understood engine, both it’s strengths AND weakness, and it’s weakness can be managed safely (it’s just a question of “are they being managed”).

Roger

[Av8r3400]

Roger - To be the voice of reason, again, I would call for someone out there with a Kitfox-VW to please step forward and tell us of their success. I would gladly offer a retraction of my skepticism. But, the silence of this group is deafening, due to, in my opinion, the fact they do not exist.

If in the 70 years of VW history and near 30 years of Kitfox history these two have not matched, I don't believe they ever will. Lowell makes some valid points as to why.

I can comment on the reliability issue from seeing several local VW powered aircraft that do not fly due to their owners being afraid of their engine's reliability. This includes an Aerovee powered Sonex suffering ignition, carburetion and general power related performance problems.

Also as point of evidence, a few months ago, there was an article in Kitplanes Magazine (I think) on a VW powered 701 that was built extremely inexpensively. The owner commented that he was not flying it much until he is able to repower it with a Rotax. Siting performance and reliability as his reasons for the repower.

[DBVZ]

All I know about this is what I read here and elsewhere online. The guy with the VW Kitfox I reported on (quote above) seems to have been satisfied with the performance and reliability he got from the Great Planes engine with a 62" X 32 pitch wood prop. The plane has been flying for over 10 years. But I have to go by what he reports, for performance. I have not flown in the plane to see for myself. Knock off some for the Classic, since his is a Speedster. It really would help if others with a VW engine would speak up here, to give honest performance numbers and comment on any reliability issues they have seen. And if they attribute any reliability issues to the engine or to maintenance.

[rogerh12]

Howdy Guys;
I have contacted the fellow with the VW powered kitfox in St. Louis (it's on barnstormers), he will be sending me pictures and performace data. When I get it, I will post it for the group for review.

Regarding the comment: "If in the 70 years of VW history and near 30 years of Kitfox history these two have not matched" Well, I say, yes they do match, and here is the link: http://www.greatplainsas.com/chooseaircrft.html

More matching in action: This is a good flying example:

Watch it climb: http://www.youtube.com/watch?v=nRWzKMYz9eA

Oh baby, it sounds so sweet -> http://www.youtube.com/watch?v=v5x-ifHEi0g

"Sort of an explination about the VW Kitfox": http://www.youtube.com/watch?v=ficAq...eature=related (http://www.youtube.com/watch?v=ficAqG07liA&feature=related)

It's been pointed out that because the VW engine requires the larger cowling, and has a limited diameter, so it can't be all that fast. I agree with this myself, and am trying to verify the typical cruise speed of a Kitfox-4-1200 with the 2180 engine (note; a 2300 cc engine with aluminum cylinders is now available too).

In the mean time, I believe it to be about 100 mph at 3000 ft msl, based mostly on hearsay, guess work what the guy at the psychic hotline told me (Also Great Plains VW). Is that fast enough ???? Shoot; my Kitfox 2 with a 582 would only cruise at an honest 75 mph, so 100 sounds awful fast to me !!!!! (Note: The guy in the video is running a super climb prop, with a very flat pitch for quick off-the-field performace).

Really, my concern is the rate of climb, and obstacles 50 feet in elevation at the end of a short runway, cruise speed is secondary to me.

I am looking at installing a 2300 cc VW engine with low compression (7.5:1) so that I can run car gas. It should produce about 75 HP at 3500 rpm, which I think might drive a somewhat fair'ed Kitfox-4 at 100 mph, but like I said, I am trying to verify this with some other flying planes (I see a VW powered Kitfox 4 on barnstormers).

Agree?

Roger

[Av8r3400]

Also as point of evidence, a few months ago, there was an article in Kitplanes Magazine (I think) on a VW powered 701 that was built extremely inexpensively. The owner commented that he was not flying it much until he is able to repower it with a Rotax. Siting performance and reliability as his reasons for the repower.


Kitplanes magazine, April 2011 issue. (http://www.kitplanes.com/issues/28_4/builder_spotlight/Wayne_Clagg_Zenith_CH701_9498-1.phtml)

[mr bill]

At 02C we have a KF4 with an A65 modified to use C85 pistons and cylinders that has been flying for the last year. It flies very well, cruising at 115 mph, both single and two place. They made their own sheet metal cowl. I am attempting to attach two pictures.

[rogerh12]

Mr. Bill;

Thanks for posting the pics of the Continental. I see there is some real space between the firewall and the back of the engine, so I guess the engine weight was not really and issue CG wise, otherwise the engine would be mounted closer to the firewall if it was too heavy.

However, I am not too clear on the engine modification. Are you saying this A-65 now has the displacement and power of the larger A-85? It is still a hand prop'ed engine, correct?

[mr bill]

The engine retained the A65 crank and has no starter, alternator or vacuum. There is an external throttle on the passenger side that allows hand propping from behind the prop while maintaining engine control during startup. They designed their own sheet metal cowling that is 5 inches lower than normal, giving better visibility while on the ground and in the air. They use a handheld radio for comm and vor.

[rogerh12]

Mr Bill'

Is it possible for you to find out what the empty weight of the kitfox is with the Continental engine and also if they had to do anything to adjust the CG (such as add tail weight)?

[mr bill]

The engine weighs 179 pounds (exhaust, prop and oil brings total to 209). Aircraft empty weight is 690 pounds, the only ballast is a motor cycle battery in the normal battery location behind the baggage compartment. It has an RV4 tailwheel assembly, which lowers the tail on the ground, which lowers landing speed. This plane has the short wing.

[Av8r3400]

That sure is a nice looking install and custom cowling.

You should run that beauty up north here this year. I'd like to get some Avid/Kitfox events started in this neighborhood. There's a lot more of us around than you would think...

Do you have skis? There's a nice fly-in at Airdale, on the lake next to Brett's house - just south of Rhinelander, in late January.

Send me a message and I will get you my phone number for more details.