Kitfox Aircraft Stick and Rudder Stein Air Grove Aircraft TCW Technologies Dynon Avionics AeroLED MGL Avionics Leading Edge Airfoils Desser EarthX Batteries Garmin G3X Touch
Page 1 of 4 1234 LastLast
Results 1 to 10 of 40

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

  1. #1
    Senior Member
    Join Date
    Jan 2011
    Location
    LAWRENCE, KS
    Posts
    479

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

    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

  2. #2
    Senior Member jtpitkin06's Avatar
    Join Date
    Jan 2010
    Location
    Greenville, TX
    Posts
    640

    Default Re: Continental 65 HP or more, Ok on Model 4 ????

    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

  3. #3
    Senior Member
    Join Date
    Jan 2011
    Location
    LAWRENCE, KS
    Posts
    479

    Default Re: Continental 65 HP or more, Ok on Model 4 ????

    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

  4. #4
    Senior Member
    Join Date
    Jan 2011
    Location
    LAWRENCE, KS
    Posts
    479

    Default Re: Continental 65 HP or more, Ok on Model 4 ????

    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



  5. #5
    Senior Member HighWing's Avatar
    Join Date
    May 2009
    Location
    Goodyear, AZ
    Posts
    1,743

    Default Re: Continental 65 HP or more, Ok on Model 4 ????

    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

  6. #6
    Senior Member
    Join Date
    Jan 2011
    Location
    LAWRENCE, KS
    Posts
    479

    Default Re: Continental 65 HP or more, Ok on Model 4 ????

    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

  7. #7
    Senior Member t j's Avatar
    Join Date
    Oct 2009
    Location
    Ellensburg, WA
    Posts
    861

    Default Re: Continental 65 HP or more, Ok on Model 4 ????

    "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
    Tom Jones
    Classic 4 builder

  8. #8
    Senior Member HighWing's Avatar
    Join Date
    May 2009
    Location
    Goodyear, AZ
    Posts
    1,743

    Default Re: Continental 65 HP or more, Ok on Model 4 ????

    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
    Last edited by HighWing; 06-05-2011 at 08:58 PM.

  9. #9
    Senior Member
    Join Date
    Jan 2011
    Location
    LAWRENCE, KS
    Posts
    479

    Default Re: Continental 65 HP or more, Ok on Model 4 ????

    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?

  10. #10
    Senior Member jtpitkin06's Avatar
    Join Date
    Jan 2010
    Location
    Greenville, TX
    Posts
    640

    Default Re: Continental 65 HP or more, Ok on Model 4 ????

    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

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •