Kitfox 4 with greatplanes - VW 2180

[lakeflyer]

Does any one know if this is a good combo to put on floats? and is this engine reliable, still looking for plane. lakeflyer

[Geowitz]

As far as floats are concerned - The consensus is no. Relatively, the power is lacking. It's heavier than a standard model IV with a rotax. Also, the shorter wing will hurt in the lift department. Finally, the direct drive only allows shorter props which kills the static thrust necessary for safe and reliable water operations.

[DBVZ]

There was an ad for a Speedster with the Greatplanes 2180, that was on Barnstormers some time ago. (removed the attachment) I went to see and fly it when I was looking. The performance was good in the short wing speedster. I think with floats and long wing, it would be slow and cruise about 80mph. Some things to think about:

1. For a VW conversion, the Greatplanes has some good features. They make some changes to the prop end of the crank that improve the oiling and longevity of the engine. It is heavier than the Rotax 912, and some people had some bad experiences with VW conversions in the early iterations of the idea.

2. Greatplanes now makes a gear reduction drive for the VW, that will reduce the prop RPM so you can use a longer prop. The direct drive VW turns fast enough the prop length is limited - the one in the ad is about as long as you can use with an engine that can turn 3300 at red line. The gear reduction version is a little heavier but is increased to 115HP I think. Check the web site for current information.

3. Most Kitfox people seem to think the Rotax 912 is the best engine match with the KF 4. Some use a Lycoming on the KF 5, 6, 7 with success because they have a higher max gross and more ways to adjust the W/B. What I am saying is, selection of something other than a Rotax 912 may be cheaper to buy and install, but will also reduce your resale price and reduce the marketability since many will reject it without even looking beyond the engine. If you intend to keep it until it is used up, or at least to TBO, it may not matter much to you. I bought an Avid with a Jabiru 2200, and so far am happy with the choice. But I know resale will be a problem when that time comes. Another new option is the Viking engine modified from a Honda FIT, that is now available for $13,000 with some modern features. See another thread on that. But until it is proven in use, you would be in a true experimental situation with that one. It looks pretty good to me, though. If I were building one, I would probably use that.

4. You may get some very negative, even dismissive, comments about the idea of a VW on a Kitfox with floats. I would just suggest you do your own analysis. Some of those with the strongest opinions may have not flown behind a VW powered Kitfox, and are working from hearsay about problems with early versions of the VW.

[DBVZ]

It is the same plane I posted the earlier ad about. I was close to a purchase, and made the trip to inspect it.

[Geowitz]

4. You may get some very negative, even dismissive, comments about the idea of a VW on a Kitfox with floats. I would just suggest you do your own analysis. Some of those with the strongest opinions may have not flown behind a VW powered Kitfox, and are working from hearsay about problems with early versions of the VW.

EVERYONE should do their own analysis. That's not what this thread is about. It's about him asking what the group thought. Some opinion, some fact. There's always a VW apologist, but where are all the kitfoxes with VW's if it's such a feasible option? Even I thought about the VW for a bit, but soon came around to everyone else's conclusion. Kitfox IV's have been around for more than 20 years. It would have taken hold by now.

Facts are facts, not hearsay - Direct drive, short prop, more weight, short wing, very specific and unforgiving cooling needs... Thermodynamics don't lie about the limited cooling factors of even the aftermarket VW heads and you ain't getting 115 hp out of any VW used in aircraft... atleast for long.

[Geowitz]

And no one can say that I'm planted in the Rotax camp. Heck, I've got the first HKS-700T in a Kitox stateside.

Lake Flyer - There have been a lot of more suitable Kitfoxes showing up on classifieds lately. I'd go for a 912, or even a 582 before I went with a VW floatplane.

The plane in the ad looks Beautiful, no doubt great workmanship!

[DBVZ]

I did not buy the plane after an inspection and flight. It is great workmanship. What caused me to walk, were just a couple things that bothered me. First, I think the pictures on the ad are from soon after the build. The plane has had some hours on it since then and is not as perfect as the pictures had me expecting. Kind of a let down after spending the time and money to fly to St. Louis. And then I am a tri-gear guy. I have flown in some TW planes, but this one has less forward visibility than most. The flange of the top cowl runs up the front window about 3-4 inches higher than necessary. Taxi is peek around the corner and S turn, and even in cruise I felt it was obstructed enough to keep me uncomfortable. That cowl obstruction is something that could be fixed fairly easily, and perhaps many TW pilots would be fine with it like it is.

Note that the engine was not the reason I walked. The engine ran very well, and the aircraft performance was adequate for me with the 76 HP and the short wings. Perhaps I would have felt differently if it had the long wings, which would make it slower. I had factored the engine and the expected resale issues into the price I as willing to offer for it, had everything else been good.

Again, if this is out-of-line I will delete it. I thought anyone thinking of making the trip may like to know.

[rogerh12]

Regarding a geared-down high Horse Power VW in the Kitfox.

I don’t think anyone has got it to work without water cooled heads as the Kitfox climb and cruise speeds are too slow for good cooling of the standard air cooled heads. It was also tried in a couple Zenith 701s and it would always overhead the heads in just a couple of minutes.

A much better (Non-Rotax option) choice would be the EA-81 (it is also geared down), which is installed in several flying Avid’s and I have "heard" good reviews about the engine and Avids flying it. Note: the EA-81 does produce less power than the geared VW, but all that extra power is not much use if you overheat the engine!

[DBVZ]

Interesting, Roger. The kitfox clearly will fly faster than a VW auto will drive on the roads, and the "fan" is a lot bigger. Could it be a matter of air ducting instead of climb and cruise speeds? I know some Jabiru 3300 folks have had trouble with heating, that was improved by better ducting of the air flow. Of course a highway car running at 70 mph may be turning less RPM in 6th gear, than a plane in a 70 mph climb.

[Geowitz]

Can anyone find me one Kitfox on floats with a VW that isn't for sale or isn't flown because it's too scary? I doubt anyone could find one that even exists in the first place.

Our situation is not really comparable to a car driving situation. The overheating is from load on the engine at 100% rpm/power. That produces a certain amount of energy(which can be mathematically calculated) which must be dissipated through heat. Speed and airflow are not really the limiting factor in our case. The real limiting factor is the lack of heat dissipation from the cylinders and heads at the power we are trying to get out of the engine. Sure, you can band aid it and get a reasonable climb... for a little while, but eventually the energy surpasses the ability of the engine cooling fins to keep up.

[rogerh12]

Nope, wish it was true that air ducting alone would solve the VW high power setting overheating problem at low air speeds. But, as Geowizt pointed out, the real issue is that there is simply not enough fin area on the VW stock heads to dissipate the waste heat at high engine power settings with a low air speeds (on 2100CC engines and larger, geared down motors are even worse). That’s why planes that work best with the VW are fast, like the Sonerai, Sonex and KR-2.

However, with careful ducting, a large oil cooler (VWs are also oiled cool to a large part), and the right prop, you can still run full power in a slow’ish climb with 2100 cc and larger engines, but not with Geared down engines producing 100+ HP. And, if it’s a hot day it won’t be for long if your climb speed is much below 90 mph. On my VW powered Zenith 601 HDS, even a 5 mph increase in climb speed made a noticeable difference with the oil temperature on a hot Kansas summer day.

Still, there are ways to cool the VW better: Thicker and larger heads are now available with better fin’ing and Aluminum cylinders to replace the standard cast iron, which help cool the heads as well. But the real fix to running high power settings on a VW at low air speeds is to install Water-Cooling heads (I had these on my Zenith for a while). Unfortunately, the special aftermarket aircraft water cooled heads I used are no longer available, as the designer made only a single run of castings, 80 sets total. And, despite out right begging by Steve Bennett at Great Plains VW (and offering to buy the rights and making them himself), the designer just won’t make more or sell the design (he is a Ford cylinder head engineer).

Anyway, all this is what I have learned over the last 10 years playing with VW’s and talking to other builders. My Model Kitfox 4-1200 is getting one installed this year. It’s a large 2300 cc engine with the new heads and aluminum cylinders, but will only produce 75 HP as the compression ratio will be reduced to allow car gas to be burned.

I just need it to outfly a Cessna 150 and I will be happy!

[lakeflyer]

WOW, Just want to thank every one for the great input on the VW powered KF-4 I saw on barnstormers, again it looked great and I'm sure it is well built and flys just fine but I don't think it would be a good floatplane based on all the great advice= wrong engine / short wing. I know from experience floatplanes can spend a lot of time trying to get off the water with full tanks, two people, gear, 85 degrees and no wind. the last thing one would want is to have a engine that isn't strong enough or getting all the cooling it needs. THANKS AGAIN p.s. I'll keep looking

[av8rps]

Keep searching for the right airplane and engine combination if you want that floatplane...the combination is critical when it comes to flying off water. Your decision to pass on the VW plane for a floatplane was a good one. The airplane was a beauty, but the combination was wrong for water flying. I have a 912ul powered Kitfox IV on amphibs and love it. It performs very well, burns very little fuel, and all the girls just love it because it is so cute ;).