Classic Model 4 1200 vs Model 5

[NewFlyer18]

Hello,
I’m new to flying and in the market for a kitfox but would like to know the difference between the model 4 and the model 5? I’ve seen a lot of model 4’s for sale and not so many 5’s. What research I’ve done looks like they are really close?
Thanks

[PapuaPilot]

The short reply is that the model 5, 6 and 7 are all very similar, and different than the model 4. The later models have a larger fuselage, higher gross weight and was made to use larger engines than the model 1-4.

The link for history is no longer working at the Kitfox website.

[NewFlyer18]

Thank you for the information

[hiline]

You need to go sit in a 4, and then a 5,6,or 7.
There is quite a bit of difference in cabin size and other things as well.
Best to see it for yourself.
Good luck.

[Slyfox]

The short reply is that the model 5, 6 and 7 are all very similar, and different than the model 4. The later models have a larger fuselage, higher gross weight and was made to use larger engines than the model 1-4.

The link for history is no longer working at the Kitfox website.

wow! I think I'm offended. I have a 4. I love it. It feels very personal to me. meaning it fits me. I have one of those big engines. yup the 912uls the same one that is standard for the model 7. Now I play big time with my plane, I have big tires. I feel the advantage of the 5 thru 7 is it's for the big person. yup, I'm a small guy 5'6 or there abouts and 175. so I fit perfect in the 4. It's like the 2000 Silverado, my truck, fits me real nice. I get in the newer chevy's and they seem so big. they are made for the BIG guy. sure I can drive them, but I love the feel of mine. same with the kitfox's the higher number fox's are bigger. more robust. have a higher payload. I guess you can go for whatever you want, but if you fit in a 4, that's a plane to have. it can give you some fun factor. just my 2 cents worth. :)

[rogerh12]

This is a link to a page with pretty detailed...well details...about the various models (see below). I have the model 4-1200, and you can get them cheaper because they made so many kits, and some folks sell them off to upgrade to the more utility capable models 5,6 and 7. However, the model 4 is by far the most bang for the buck, best combination of useful features, ability to use a smaller cheaper engine and still go fairly fast, and of course lower overall cost to buy, and often maintain too..But watch out, some model 4s had a 1050 gross, and those should not sell for much more than a model 2 or 3.

http://kitfox.lazair.com/skystar/Aircraft_History.htm

Hope this helps
Roger

[jrthomas]

My personal opinion is that the Model 4/1200 in in a class by itself. Outward appearance is similar to the Models 1 thru 3 but otherwise it's a totally different airplane. The controls are different, they fly different and they perform better. The 4 has a totally different airfoil than the earlier models. The vertical is much larger and the control rigging is much improved. The Model 4 with an equal Rotax 912 will outperform the 5 thru 7's in about every area. The Models 5 thru 7 moves the engine forward so heavier engines work better on these than the model 4. They also can carry much more weight in the baggage area without getting into an aft CG problem. Kitfox made a giant leap forward with the Model 4/1200. The 5 thru 7 are more refined. All are good. I love my 4 with 912, Grove gear and fat tires. I'm sure I'd be equally happy with a later model. You can't go wrong with either.

[NewFlyer18]

I really appreciate all the feedback. I’ve found a model 4 that I really like and plan to take a better look at it. Thanks again it was very helpful.

[av8rps]

The Model 5 though 7 are really great airplanes, and because of their slightly increased cabin size, baggage area, and strengthening allowing for a 29% gross weight increase, that all makes for a pretty versatile airplane for the average guy.

But those nice improvements increase the average empty weight about 25%. And considering that the newer Kitfoxes and the model 4 use the same wing and tail, performance is going to be less on the newer models with the same power as the wing and engine has to haul more weight. Unless you are willing to go all out and spend the big $$ on a 915is and a STI wing, the Model 4 with a 100 hp Rotax is going to outperform the newer models pretty significantly. I would speculate that a 912ULS powered 4 with a standard wing will perform on par with that 915 powered Model 7 STI, but that is speculation because I have never flown a 915is STI. The 4 for sure would be faster in cruise.

Now I'm not knocking the new Kitfoxes, as I personally really like them and have many times contemplated upgrading. But I fit in my Model 4 really well (at 6 ft 1" and 190 lbs), and even with only a 80 hp 912ul and a 250 lb set of amphibs hanging underneath it, it still performs great. And of course, I have significantly less money in it than I would have to pay for a newer model.

And yes, you can typically buy a Model 4 for much less than a Model 5, 6, or 7. That doesn't mean the 4 is that much less of an airplane. The price difference is more reflected in what the original builder spent building it back in the early 90's as opposed to what it costs today (eg, a new 912 was under 10 grand back in the early 90's and the kit was 12 grand). So back in the 90's you could put together a nice Model 4 for 25 to 30 grand. Today, a Model 7 SS will cost 65 to 75 grand. That really is the primary reason why there is such a price difference. It isn't that the 4 is half the airplane. In fact, I would say the 4 is 90 percent of what the new ones are in overall usefulness, and 125% in performance.

But again, they are all great airplanes. The cool thing with the Kitfox design is whatever your taste and budget, you can have it your way.

You can't go wrong with any Kitfox in my opinion...

[HighWing]

Now I'm not knocking the new Kitfoxes, as I personally really like them and have many times contemplated upgrading. But I fit in my Model 4 really well (at 6 ft 1" and 190 lbs), and even with only a 80 hp 912ul .... it still performs great. And of course, I have significantly less money in it than I would have to pay for a newer model.

..

I couldn't agree more. Early on when home building was a bit more of a novelty, I used to say my Kitfox is more like a dirt bike than a Honda Goldwing. I fit in everything "medium" and the IV fits "me" perfectly. As far as "luggage" I was often curious when on our group fly-outs seeing what some guys brought to camp in. My tent weighed 7 lbs. Sleeping bag - 1.5 lbs and packed into a compression sack the size of a football. Personal items were in a modestly sized backpack and strapped in the passenger seat. Due to some mods, my baggage sack was placarded at 25 lbs. and never maxed out. Paul was spot on when he mentioned cost. 1993 $9000 including speedster elevator - trim tab - option. 912 UL - $11,000. Panel and paint close to another "10", Then I did it again ten years later for about the same $$.

Other's thoughts may vary!

[rogerh12]

My model 4 is my ninth plane, and all of the other 8 had the same thing in common, I didn't pay much for them. And my model 4 is no exception, paid $5,000 for a new un-started kit, with rotax firewall forward (no engine) from a widow I tracked down and held a pile of $100 bills in front of her, with a trailer attached to my truck. She took it. I sold the firewall forward kit for $2700. Yes, you do the the math on that one, total cost $2,300, and it came with the factor jigged wings. Older planes, forgotten planes, superseded models can all be had for cheap, if you do some digging, and more digging. Place a wanted ad, join a club and get the word out, you need a good cheap plane project. The less money in your plane, the more likely you are to keep it in the air, having not gone broke buying factory new. The newer plane kits?....probably going to pay way way more than older. But are they way WAY better? Probably not.
Hope this helps
Roger

[GMKman]

wow! I think I'm offended. I have a 4. I love it. It feels very personal to me. meaning it fits me. I have one of those big engines. yup the 912uls the same one that is standard for the model 7. Now I play big time with my plane, I have big tires. I feel the advantage of the 5 thru 7 is it's for the big person. yup, I'm a small guy 5'6 or there abouts and 175. so I fit perfect in the 4. It's like the 2000 Silverado, my truck, fits me real nice. I get in the newer chevy's and they seem so big. they are made for the BIG guy. sure I can drive them, but I love the feel of mine. same with the kitfox's the higher number fox's are bigger. more robust. have a higher payload. I guess you can go for whatever you want, but if you fit in a 4, that's a plane to have. it can give you some fun factor. just my 2 cents worth. :)

I think the big engines Phil is referring to are the Lycoming, Continental, and 914 turbo engines that are an option in the 5,6,7 not trying to offend anyone.
I have the Continental and I can cruise at the 140 mph vne of the higher Kitfoxes (not that I would). I think the model 4 has a vne of only 125mph. I could be wrong on that.

[jrthomas]

The Model 4 Speedster has a VNE of 140 according to my build manual.

[GMKman]

Nice!! I like that.

[PapuaPilot]

I think the big engines Phil is referring to are the Lycoming, Continental, and 914 turbo engines that are an option in the 5,6,7 not trying to offend anyone.

That's exactly what I meant. When I was looking to buy a KF the 4-1200 was on the table for consideration.

I think the model 5 was introduced about the time Home Improvement was airing and everybody wanted MORE POWER . . . :rolleyes:

[Slyfox]

and more power isn't wanted now. holy crum, that's all people are talking about now. I want ... to go to the moon. lol

[Hockeystud87]

I'm 6'2" 185. The model 4 -1200 speedster I fly is a great fit for me. The controls can be a little tight on the extremes but the 4 is so dang responsive I don't think I've used more than about 3" in any direction when flying other than full back on landing.

It's stinking cheap I burn under $20 an hour in gas. I do all my own work and just pay parts. I get a consistent 1000 FPM climb and cruise about 85 knots. ( I'm under pitched right now). I get up in under 200'. All this on a 912ul 80 HP. I've thought about going with a zipper kit to make it a 100 HP but IDK if I need it.

One thing to keep in mind is that the model 4 really isn't a 2 person camping plane. (At least that's my opinion). By the time you get 2 people in there plus gas there isn't much room/weight for camping gear. Also there just ain't places to put it unless you're gonna throw it on someones lap. As a single person excursion plane almost unbeatable I think.

I'd personally get a 4 if you're going mostly solo and a 5-7 if you're going for a true 2 placer.

[HighWing]

My thinking exactly, but better said.

[PapuaPilot]

Yes, well said.

I have been glad to have the ability to carry 100+ lbs. in the baggage area. Even with the heavy engine I still have a UL of 660 pounds and 500+ lbs. with full tanks.

[av8rps]

I remember years ago asking a Rotax rep about the results they obtained after flying their testbed Model IV Kitfox Speedster that they had put a 914 on. He said the Speedster with the new engine would hit 140 in a mild climb. Unfortunately they felt the Speedster was so overpowered that they weren't going to promote that engine in that airframe. Funny, I didn't know you could overpower a plane until talking with him ;)

Questionable info? Hard to believe?

To prove it to myself, I just did quick math on a 650 lb EW Model 4 with a 115 hp 914 to determine a empty weight power loading. That quick math says there is only 5.65 lbs of airplane to lift per engine horsepower. That is a very good number. How do I know?

Well, lets compare the Speedster against Trent's superb performing 915is powered Kitfox 7 STI:

From my memory (which is not always great, so go easy on me...) Trent's STI weighs 930 lbs empty and has 146 horsepower. Now we know that thing really cranks :cool:, and that makes sense as the power loading (empty again) is only 6.37 lbs per hp. That too is an awesome number as typical GA aircraft run 10 pounds plus.

But the Speedster at only 5.65 pounds per hp is more than 10% better than Trent's plane. So the Model 4 should perform on par with Trent's hotrod, or better.

I know, I know... this is a crude comparison. But it is logical to me ;)

So is there anyone out there in Kitfox Land that has a 914 powered Model 4 that could back up my theory?

Just in case I'm now slipping into my custom made flame proof jump suit now...

[Av8r3400]

Not yet... :eek:

[ClickClickBoom]

$.02
I have a Model 4 1050, 80hp 912 with 13 gallons onboard. I am sized at 5'11" 235lbs, the fit is fine, fine enough to fly from near KMSP to KWVI in 2 days of flying about 19hrs and 59 gallons of avgas. I flew The Rockies, Wasatch and The Sierras in one day and Came over Yosemite at 16500msl and decided to quit climbing because it was so cold. My climb at 16500msl was 500fpm, on a 80HP 912.
The limiting time for me is a sore butt, after 3 hours in any plane I am ready for a leg stretch. The real question is, what is YOUR mission profile? For me an airplane that will go 3 hours before needing fuel is plenty, 95% of my use is 3 laps around the patch. Figure out your mission, and buy the appropriate plane, wanna travel fast and high, Questair Venture.

[Hockeystud87]

Hey my grandpa kept his model 4 at Wattsonville as well! Did all his test flying out there.


I remember years ago asking a Rotax rep about the results they obtained after flying their testbed Model IV Kitfox Speedster that they had put a 914 on. He said the Speedster with the new engine would hit 140 in a mild climb. Unfortunately they felt the Speedster was so overpowered that they weren't going to promote that engine in that airframe. Funny, I didn't know you could overpower a plane until talking with him...

Alright I'm gonna bite. So I was under the impression the 4 wasn't able to fit the larger motors on them. I assume this would require a custom firewall/mount and aft balance adjustments?

Also if you're pulling 140 in a climb that would make me think you'd have to lug it just to stay under VNE in cruise. IDK how good of a setup that would be. Maybe if you had a adjustable prop you could play with pitch to not have to lug the motor in cruise. The pitch it more for fast climb?! IDK how that would work. I had a RC plane that I did a similar thing like this to. So big a motor up front I literally put lead in the back for balance. I could hover it at about 1/2 throttle and climb away fast at full throttle. I only cruised around 1/4 throttle. I think at some point your engine is so much power you're just not able to run it appropriately or how it was designed.

Just spit-balling cause you peaked my interest. Now someone needs to try it! Little off topic. :rolleyes:

[av8rps]

A 914 on a Model IV is probably a bit tight to fit under the cowl, but the weight is a minimal increase compared to the regular 912. So weight and balance would be no issue at all.

Lugging the engine to keep it from over speeding is also not an issue. I have flown 912 engines for hours at lower rpms, 1/3 to 1/2 throttle with no issues at all. A 914 would be no different. You can always throttle back if you are concerned about over speeding the airframe or you just want to fly slower and enjoy the scenery.

A 914 in a Model 4 on paper will have some astonishing numbers, and the performance might even be intimidating to some. But for many of us, that will just make it more fun! I still don't know if there ever has been an overpowered airplane (smile)

I grew up flying model airplanes, including RC. The scaling factor of model verses a real airplane simply doesn't compare. If one could build a real airplane like a model, assuming a 1/4 scale model Kitfox would weigh 15 pounds, then a full scale Kitfox would only weigh 60 pounds, which we know isn't possible. That is scale factor. So models end up with impossibly good power to weight ratios. Probably not telling you anything you didn't already know, but I explained all that for others that didn't.

Hmm? I wonder what would it take to get my Model 4 to hover???

[Esser]

I am at the forward limit of my C of G when solo on my Model 7 with a 914 and a constant speed prop. I also have an intercooler which the 914 pretty much NEEDS I don't think on a model IV there is much room to have a straight forward intercooler install.

[Av8r3400]

Josh - I'll show you the weight and balance on the Mangy some time...

[av8rps]

The Model 4 is easier to balance with extra forward engine weight because the nose is so much shorter than later models that have the longer nose. In fact, a little more weight forward on a typical Model 4 would be a good thing.

[HighWing]

When building my second Model IV, I moved the 912 a bit forward with a new engine mount to help recover some of the baggage sack capacity I lost in the first one when I put all the fairings and gap seals in the empennage. When weighing for CG, I discovered I was very close to the forward limit. Thinking about it, I remembered when I was working at United Airlines on the ramp. This was shortly after the Arab Oil Embargo. It was determined then that Max fuel efficiency was flying with CG at close to the aft limit. Very often all luggage was loaded in the aft pit. And if not full, passengers were spaced to achieve an aft CG. I decided to put 5 lbs of lead in the tail pending a tailwheel upgrade. CG still a bit forward, but hopefully a flatter elevator and a bit more speed and efficiency - assuming a Kitfox is at least a tiny bit similar to a 747.

[PapuaPilot]

I grew up flying model airplanes, including RC. The scaling factor of model verses a real airplane simply doesn't compare. If one could build a real airplane like a model, assuming a 1/4 scale model Kitfox would weigh 15 pounds, then a full scale Kitfox would only weigh 60 pounds, which we know isn't possible. That is scale factor. So models end up with impossibly good power to weight ratios. Probably not telling you anything you didn't already know, but I explained all that for others that didn't.

Hmm? I wonder what would it take to get my Model 4 to hover???

Sorry, but the numbers you used for scale factor are incorrect. If you scaled up a 15 lb. 1/4 scale plane to full size it would weigh 3375 lb. You have to cube the numbers to scale the weight factor.

If we scale down a 1550 lb. Kitfox to 1/4 scale you would do the cube root of 1550, which equals 11.6 lb. A 1200 lb. KF4 would be 10.6 lb.

The same thing is true with power. If you want to power a 1/4 scale version of a 100 HP engine you would need a 4.6 HP engine (that weighs 5-6 lb. too).

Lastly, if you want to hover your KF4 you will need about 1200 lbs. of static thrust. That might take a slightly bigger engine up front. The engine on Draco might be enough. We are all waiting for your video. ;)

[av8rps]

Phil that was my point... scale factor is not so simple as just increasing the weight by 4.

As an aside, my 680 lb 912uls Highlander when flown light and in cool temps will "Hover. Seriously. I was practicing full power departure stalls one no wind fall evening when I discovered that with full elevator and the nose essentially straight up it just hung there and as long as I kept the power on full it would just hang there with no forward speed, and never did stall. I asked other Highlander owners if their planes would do the same and learned that some other lightweight and 912 powered Highlanders did the same thing.

But we don't really believe we are hovering. While it feels like you are straight up you aren't quite, so the undercambered wing is still producing lift, and that lift is just enough combined with the thrust the prop is making to make the plane feel like it is hovering. One day I'm gonna get a drone to film that as I'm guessing it will look pretty weird. Even my early super lightweight Avid Flyers wouldn't do that. I'm guessing only because they had much smaller elevators. All I know is that it sure feels strange...


Sorry, but the numbers you used for scale factor are incorrect...