Model IV vs Speedster guidance

[teamkitfox7788]

Folks,
I have a model IV 1050 with 80 hp Rotax 912 that is very draggy and slow but thinking about a model IV 1200 with interchangeable speedster/regular wing tips with claims of 115 mph cruise with speedster short wing configuration.

Any comments on real world performance differences, flight characteristics of significance and STOL differences would be appreciated.

BJ
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[Norm]

I am wondering what you think is very slow. Also what kind of prop are you using.

[Av8r3400]

Yes. Please provide some data and specs on your current plane.

Neither of my planes are speedsters and they both will cruise 110+ without a problem.

[Norm]

Larry
That is great speed out of Mangy Fox with the Big Wheels and the Climb prop. I am sure the Zipper kit helps a lot.
Norm

Yes. Please provide some data and specs on your current plane.

Neither of my planes are speedsters and they both will cruise 110+ without a problem.

[Av8r3400]

Yes that one cheats a little being 105 hp...

But, my 'Ol Yeller still scoots along with 80 hp and a warp drive prop. Easily getting 120 on a smooth day.

My wonder is what is the weight on his plane and the state of rigging. Not to mention some amplification on "draggy and slow". What is meant by that specifically?

[teamkitfox7788]

My questions revolves around the difference in cruise performance, handling, STOL capability between speedster model IVs and a regular (longer wing) model IV. So comments on that are sought.

In addition, how does changing from speedster wing, by swapping to the longer wing tip/extensions (28 to 32 feet?) effect the above questions? There are surely folks who know a lot about this from owning/flying both and talking within the family of Kitfox owners.

Please note that I do not plan to to get rid of my current model IV just maybe add another plane that will be used in other parts of the good old USA with quite different mission profiles. So the question is about the general differences between variants mentioned.

But to be courteous and respond to some of the questions:

I usually fly almost exclusively with the doors off, low and slow at sea level power back (4,100 rpm), spotting sting rays, sharks, dolphin, lobster ledges, reefs and bikinis and probably showing around 55 mph on gps. Years ago when Flying between Maryland and the Florida Keys (old three blade wood prop) I was showing about 90 mph on gps but can't recall winds, probably some degree of tail wind and as I recall prop pitched to cruise, maybe somewhat aggressively in that regard. Currently at about 5,000 rpm i probably show around 75 on the gps.

My model IV 1050 has an empty weight of 610 lbs.

Warp drive three blade with metal (nickle) leading edge. Currently Moderately pitched to a compromise between climb and cruise performance.

The original equipment size 8 inch Douglas wheels with 20 inch diameter tires, newer version Matco brakes (gold color, originals silver color calipers were crack prone),

Tube steel main gear legs with no fairings, Alaska Bush tail wheel.

Of course my vertical stabilizer is quite a bit shorter than a model IV 1200/Classic.

Fairings on wing struts, lots of gaps between door edges in places and fuselage. Lexan cabin roof is not attached along upper cabin surface so it bows up a bit in flight. No cowl around engine radiator under cabin. I weight 170 lbs although I hate to consider myself a standard FAA person, whatever that is. Oh, a surprisingly small overall opening and no down lip at bottom of engine cowl trailing edge so cooling drag may be impressive.

Regarding rigging, it Does not track straight hands off. Wings are being recovered at this time and rigging is to be re-examined/adjusted thereafter.

Now, Back to the original question if you will.

Thanks for the help in advance.

BJ

[av8rps]

If you really want a Kitfox to cruise fast, most important thing to do is to make sure you have as many lower false ribs in your wings as the Speedster / 1200 has per bay. The 1050 used one fewer per bay (as I recall), and consequently at higher speeds the pressure pushes the fabric upwards making the airfoil more like the original undercambered airfoil used on all earlier (and slower) Kitfoxes. That's why most 1200's fly faster than previous models whether a 32 or a 29 ft wing. At least that's my take on it.

Besides that, streamline everything you can and set the prop for a WOT max rpm straight and level of 5650 to 5800, make sure your flaperons and tail incidence allow the airplane to cruise flat, and you will be getting max performance out of a 912 powered Kitfox 4.

At least that's my take on things. I fly my 80 hp 912 Model 4-1200 on amphib floats with an IVO IFA, and I can easilly fly 115 mph even on floats. And there are still a lot of things I could do to "Clean it up".

I can appreciate your desire to have more than one Kitfox. And frankly, if I were only flying a Model 4 on wheels I would prefer a Speedster as it not only is faster and sportier, if done right they are really a beautiful airplane. Ramp appeal is off the charts...

[teamkitfox7788]

Guys,

Two great responses that are both very much appreciated. Thank you!

Don't let me cut off any other comments by thanking you guys.

One of the huge advantages of owning a Kitfox is the abundance of knowledge/experience in the heads of so many owners and builders in the Kitfox community.

I LOVE MY KITFOX.

BJ

[av8rps]

I'm glad to know you found some value in what we shared.

And I too love my Kitfox. They are just the coolest little planes a guy could ever want. They do everything so well, and I always tell people it is probably the closest thing to a human being strapping on two wings and going flying. Above all things, they are just a blast to fly....

I've flown a lot of fun airplanes in my life, but I'm not sure if there is anything more fun from the fun flying perspective. And being able to do just about anything with them is just a big bonus.

Typically when people see mine at seaplane gatherings I will usually get a comment before the event is over "If you ever decide to sell your Kitfox, call me first." Of course, I can't imagine letting mine go. I just have too much fun with it.