Kitfox IV classic advice.

[RV6]

Hi All, I would like some advice on the Kitfox IV classic. There is one for sale here in Aus. I am thinking of purchasing. It has a Subaru engine in it that I would like to change with a Rotax 914. Will the airframe handle this engine ? What is the wing like on the classic ? I would like to end up with a respectable STOL plane. How much different is the stol wing for Kitfox compared to this ? Are they interchangeable ? Go easy Im new to kitfox planes and trying to understand the differences . Cheers

[Jono]

Hi Mate,

The Kitfox IV is a very capable STOL machine with a Rotax 912 (80HP). Not sure if you can go bigger, I've always felt that the 80HP is plenty.

There is a large difference between the MkIV vs say a Mk5 or Mk7 regarding usable load. If you get a MkIV 1050 you'll find its a little more limiting in the MTOW / usable load. The MkIV 1200 gives you a fair bit more usable load. The MkIV's and earlier are not compatible with wing upgrades etc. I'm certainly not trying to steer you away from a MkIV - I have one and love it.

If you're planning on flying solo either model would most likely be suitable for you. Keep in mind, big tires, bells and whistles all add weight. Weight it a little more critical on these lighter birds.

What part of Aus you in?

Jono

[RV6]

Hi Jono, I live in Brisbane. Not sure which model this one is. Currently states it has 100HP subaru which I am not keen on. Year of manufacture is 2003 if that helps. I have a 914 engine I am building up at the moment. Thought this may be a good airframe for the engine just not sure if it can safely handle this power.

[herman pahls]

i fly a model 4 with the 100 hp 912S on 29" Bush wheels and it is a great poor mans super cub.
If both airplanes are flown well in no wind, say landing the Cub takes 175' and 250' for the Fox, but the Fox will get you there faster.

i am sure the 914 will nor weigh any more than the subaru you want to replace, most likely less.
The 914 may have more HP and better density altitude performance with the turbo.

[Dusty]

The 914 would be a real tight fit in a 4. You may also have cg issues. It would however, go like a rocket.

[RV6]

Thats what worries me. VNE / Flutter issues.

[jrthomas]

I'm sure the 914 is much lighter than the Subaru so the c/g issue should be improved. I'd bet there are several pounds of lead in the tail now. Depending on which Model 4 it is, exceeding vne may not be a problem. My long wing Speedster (airfoil tail) has a vne of 140. The biggest problem I see is installation. The cowling is pretty full with a regular 912. I doubt a 914 would work with the standard cowling and engine mount. Have you considered trading your 914 for a 912S? The 912 would be a much simpler installation and would have all the power you'd ever need unless you really need to go high. If you're really set on using the 914 a Model 5 thru 7 would be better suited.

[Av8r3400]

Fitting the 914 on the "standard" Model IV engine mount will be impossible without extensive modifications.

Since you are "building" the 914, maybe consider changing the build to a non-turbo big bore engine which will fit into the standard mount and be lighter. (Selling the turbo could finance the big-bore kit.)

[hairy_kiwi]

FWIW:
I was in a similar position as you, 12 months ago here in the UK. I inspected a very tidy Model 4-1050 with a Rotax 582 going for what I was told by a mate with a Model 3 was way too much, priced at GBP16k. I slept too long on it and lost out. Now the 1050 may not be ideal - but I’m still looking instead of doing any low cost taildragger flying. My recommendation, especially if local availability is not that great and the airframe is in a halfway-tidy condition, buy it and decide what to do about the fitted Subaru and your 914 later. My impression is that there’s very strong demand globally for Kitfox 4 and later models in tidy condition and you can easily expect to pay 20–30k USD/GBP for a Model 4 ( with 912) and 35–45k+ for a Model 5 or later. I definitely #BlameTrentPalmer :) - but it is genuinely great to see the type retaining and even clawing back some value after all the effort the original builders went to. Also check out one of Scott Palmer’s vlogs:
Bush Flying the Owyhee's with KitFox Model 4's - https://youtu.be/OcT8xe1z61c At the 3 minute mark he chats with Ty Ferkin about swapping his Highlander for a Model 4 with 80hp. I think you’ll agree after watching that video you can have a shed load of fun on 80, never mind 100 hp in a 4.

In the UK, I believe 100 hp may be the maximum our regulator (the LAA) currently approves to be fitted to an original Denny model 4, likely based on the original Denny stress calcs: Search “LAA TADS Kitfox”, if you’re want some interesting/useful reading - especially as the TADs also list manufacturer SBs and SLs and LAA’s mandatory mods: they may not be applicable outside the UK, but mostly they’re well thought through requirements. Here’s the link to the TAD for the early model Kitfoxes for convenience: http://www.lightaircraftassociation.co.uk/engineering/TADs/172%20DENNEY%20KITFOX%20MK1,%202,3,%204,%204-1200.pdf

Lastly: The used Kitfox market in UK and EU is so dry I’ve taken to looking at Barnstormers.com and am seriously considering importing one from the US. (Anyone want to do similar and care to share a container? DO GET IN TOUCH :) I’m also considered building a Classic IV which I emailed John McBean about last month. He replied, “I might suggest getting a Series 7 instead of a IV.” I read into that the factory is running at full tilt producing 7s (it’s a 13 month wait currently) and they can really do without the distraction of building Classic IVs, which I fully understand. Now I’m not ruling out building a 7, but it does make me kick myself again for not grabbing that 4-1050 at GBP16k and enjoying it in the meantime.

All the best! Let us know what you decide.

Hamish
Ledbury, UK

[RV6]

Thanks fo your input guys, much appreciated. This has given me some extra leads on reading material that I can follow up. I have to finish some restoration work on an aircraft and sell it to finance this one but might have to find space and take the leap on the kitfox as they are in fashion at the moment. Cheers