Kitfox-4-1200 : 2180 VW power Performance Data Available !!!!!

[rogerh12]

Howdy all;

Ok, I finally was able to get the performance numbers off a flying Kitfox-4-1200 with a 2180 Great Plains VW motor installed, it‘s the one in St. Louis, currently listed on Barnstormers.

The great thing about this plane is it’s a known quantity. As VW aero engines can be anything from a 1600 cc 45HP engines to a 2300cc 100+ HP monsters (with water cooled heads), this engine has been identified as a 76 HP Great Plains 2180 cc engine turning a Sterba 62x32 prop at 3000 rpm in cruise. This engine requires Avgas at this HP rating and develops peak power at about 3500-3600 rpm, but typically cruises at 3200 rpm, which is close to where the peak torque is created.

Here are the specs, I would be interested in any comments:

N53RJ KitFox IV Speedster

Weights:
Basic Empty Weight = 700lbs
Max Weight = 1200lbs
Usefull Load = 500lbs
Fuel Capacity = 27 Gallons
Wing span = 28.8 ft.
Fuel Burn = 4 - 4.5 Gallons an hour
Cruise speed (economy setting) = 90 to 95 mph at 1500 feet (3000 rpm).
Cruise speed (high setting ) = 110 mph at 7500 msl.
Max speed (At full power) = 115 mph at 7500 msl.
Rate of Climb (two people) = 700 fpm
Rate of Climb (One ) = 1000 fpm
Take off roll at Gross Wt = 300 feet
Landing roll at Gross Wt = 300 feet
Stall speed (with vortex) = 37 mph
Approach speed = 60 mph

Ok, well let me know what you think.

Roger

[szicree]

This is only my opinion, but I feel some skepticism when I see an empty weight of exactly 700 lbs. Too many round numbers for me to trust their accuracy, especially when it's a plane for sale.

[jtpitkin06]

Roger,
I applaud you for exploring alternative engines for the Kitfox in the spirit of experimental aviation.
The Kitfox has undergone a metamorphosis with engine changes over the years. From the diminutive two-cylinder two-stroke to the Rotec radial. If no one had the courage to try a different engine, all Kitfox aircraft would have that wonderful ring-ding-ding two stroke exhaust note.

Many engine combinations are flying… some good, some not.

Your inquiry into the VW engine is not without merit. On the positive side it is significantly lower in cost than a Rotax. It can be purchased completely assembled. You can get an off-the-shelf motor mount to fit the Kitfox. Parts are cheap and many are available at your local auto parts store.

On the negative side is additional weight and a slight reduction in available power for a reduced level of performance. However, the performance of a Kitfox is so sprightly; you might give up a little without putting the aircraft into the flying dog category.

If the cost difference between the Rotax and the VW is the make or break point on being able to afford the airplane, I’d say go for the VW. That’s better than no airplane at all.

For example, there are Champs and Cubs flying with 65 hp engines and some versions flying with 180 HP. To be sure, the higher HP versions have great performance; but, that doesn’t make the lower performers any less fun.

So it is with the Kitfox. I don’t think any Model 1 or 2 owner will say his aircraft is worthless because it doesn’t perform as well as a Model IV with a Rotax 100 hp. To the contrary… I only hear of how much fun they are having flying. If you decide to put in a VW it should be a great flying airplane and who cares if it isn’t the superstar of performance. You can buy a lot of gas for the $10,000 saving in engine acquisition.

I don’t think reliability is an issue. The VW runs and lasts just fine. It’s been flying in airplanes for over 50 years. When you look at most engine failures, you’ll find they are usually fuel system related with few mechanical failures. I wouldn’t hesitate to fly behind a VW from Great Planes.

I first looked at the Kitfox in the early 80’s then 90’s and 00’s. When the Rotax 912 80hp first hit the scene, lots of naysayers touted it was too big and too heavy. How things have changed.

One factor has popped up of which you may not be aware. The Kitfox factory is phasing out the Model IV. It is currently special order only and it is not public how much longer they will produce the airframe. Unless you buy a used Model IV to do an engine swap, you are probably looking at a Super Sport for a new Kitfox.

That may change your engine specification window due to the heavier airframe. Certainly the days of 65 hp engines in a new Kitfox are over. And perhaps the days of 76 hp engines are over, too.

This should give you a lot to chew on.
Enjoy your quest.

John Pitkin
Greenville, TX

[rogerh12]

John;

Thank you for your well thought out remarks, it's nice to see others understand that without lower cost engine options for the Kitfox in these tough times, fewer Kitfoxs airframes will be sold and fewer people will get to enjoy this wonderful airframe.

I am painfully aware that the Kitfox model 4 is being phased out, and I have told the Kitfox owners that I think it is a big mistake !!! They risk locking the company into producing an airframe that can only be powered by a an expensive European engine. What will happen to their airframe sales when that Rotax 912 engine starts selling for $39,000 ??? Don’t laugh, it will a happen !!! It used to be a $9000 engine, then a $19,000 engine and I think we all know it’s going to be a $29,000 engine soon enough, with the state of the US dollar / Euro exchange.

$39,000 Rotax 912 engines will become a reality; it’s just a matter of when !!!!

The Kitfox-4 is different; it CAN use cheaper American made alternate Engines like the VW. Yes, some of the new parts come from Brazil, but we aren’t loosing that $$ exchange race. Most of the Aircraft VW parts are made in the good old USA, the crank, the Cam and other major parts.

If Kitfox wants to keep selling airframes, even in tougher times, they need to offer the Model -4 as it will remain the aircraft that can STILL be powered economically, with smaller engines like the VW and others.

My three cents worth.

Roger

[GDN]

Do you think it's possible to install an engine as so heavy then a Rotax 100 HP on a kitfox 2 or not ?

[Av8r3400]

Actually, Roger, the model 5 and up can use "regular" aircraft engines - Continental and Lycoming. They were designed for the additional weight. The model IV was designed for a 80# Rotax 582 two-stroke.

These motors can be had for much less than your VW conversion kit (as can a 912) if you know how to look for them.

[rogerh12]

Howdy all;

The question was "Do you think it's possible to install an engine as so heavy, then a Rotax 100 HP on a kitfox 2 or not ?"

I had the Kitfox 2 with a 582, and I think that that is really the limit on weight and HP on his model (though some have used heavier engines) It just didn't have a lot of structure to support anything more than that in my opinion, and was very limed on the tail feathers Also, even with the lighter 582 it flew terrible. Slow with the old wing design, and the worse adverse yaw imaginable, in my opinion. Also, on the ground it was very tippy due to the narrow gear, but climbed good.

I would not consider any Kitfox before the Model 3 anymore, and even the model 3 should have model 4 upgrades installed. But that is only my opinion, and is directed at the "average" pilot.
The model 3 can handle the VW, but upgrading the lift struts is recommended, (both main wing and tail struts) as well as the rudder peddles, landing gear and perhaps also raising the tail and increasing the elevator size.

Final note, a "light weight" VW engine variant is available, it uses aluminum cylinders and single magneto ignition with a Posa or Aerovee carb. Total install weight is something like 15 lbs less than typical VW installed weight.

Hope this helps

Roger

[Newkid]

I was just going to say that if you don't mind going used you can have a very cheap airplane. For the last few years I helped my dad build a Model IV that we had a little more than $20,000 in. We found a kit in California, that hadn't been started, for $6,000. Bought a 912S with 300 hrs. on it for $9,000. Bought extended landing gear for a grand. Got a prop on a trade, painted it ourselves, and bought a firewall forward from Kitfox. It had a new Garmin SL40 and a P.S. Engineering intercom. I know you can't always find a 912S for $9,000, but there are 80hp 912s out there for even less that you can hop up to 95hp or so. I know a guy that is converting a 912UL to a 914 for less than $10,000 motor and all.
So for twenty grand we had a Model IV that would take off in 90ft. solo, climb at 1500 fpm. and cruise at 108 mph. Not bad

[DBVZ]

The actual W/B spreadsheet for this aircraft says 695. Perhaps 5 pounds allowance for loose stuff.

[rogerh12]

Dweight;

Ya my Zenith 601 HDS with the same engine weighed in at about 650 lbs. It was built to a 9 G spec, and is made of all aluminum with lots of structure in the wings, and had steel landing gear to boot. I find it hard to believe a kitfox -4-1200 could weight much more with the same engine myself....

Roger