Model IV flap setting markings and ops

[jonstark]

The build manual has you set the flapperons at faired or zero degrees then with them moved 5 degrees to 20 degrees the handle is marked as "SPOILER" range. Greater than 20 degrees is then marked as "FLAPS".

I'm getting ready for my first flight and wonder what effect these settings have on ops. The manual says "never attempt to take-off with flaps in SPOILER range".

What has been your experience with flap settings?

thx,
jon

[HighWing]

on,
This is one opinion. I have 1000 hours in Model IVs. I guess the story begins when I once flew to visit a friend inland from Monterey Bay. I tied down facing east with the strong offshore winds from the west. On departure, I discovered some issues - primarily not being able to achieve normal cruise speeds. What I finally discovered was that I was flying with full flaps - at least the maximum as determined by the limits in the system. While parked there, the strong winds had overcome the friction lock and fully deployed the flaps. Arriving home, I immediately tied the flap handle to off with a Nylon Tie Wrap. I flew with that configuration for the next several years and can honestly say that in my thousand hours I have never used flaps - take off or landing - ever. And that included significant hours spent exploring the back country strips of Idaho (YouTube channel link in my signature).

In contrast, a friend recently told me of his experience flying with flaps. He, on the other hand, uses them regularly. I don't know the limits he uses, but with flaps on landing, it requires some extra up elevator to maintain attitude. Then as he loses speed near touch, he experiences a nose drop as the elevator loses some efficiency with lower speeds. He discovered that he could regain elevator authority by adding a quarter turn of throttle increasing RPM a bit. He was very pleased and recommends that procedure.

In short, in my mind - not using flaps equals simple, using flaps equals complex. I guess I should say, that unlike the typical Model IV, I do have elevator trim that eliminates the need to use the flaperons for attitude trim in flight.

[jonstark]

Thank you Lowell. That eases my mind somewhat. Of course I’ll still need to curb the palpitations for that first takeoff and landing!

Jon

[Kitfox Guy]

I concur with Lowell, I've got about 800 hours in my KF and never use the flaps either. I use a tie wire to hold them in the neutral position. Even without flaps the KF can be slowed to land just about anywhere.

[av8rps]

For a first flight I would consider it critical to know your flaps are in a neutral position so as to not be in the spoiler position as that will cause a loss of lift, which could make for an extremely dangerous first flight.

For initial test flights I would recommend not using flaps, as they are not necessary for flight.

But I disagree with not using them once past initial test flying stage. Using flaps increases performance on takeoff and shortens landing. Flaps reduce the stall speed, plain and simple.

The earlier Kitfox flaperon (Model 1-3) did not work as well as the Riblett wing used on the Model 4 and newer, as the newer wing has a much larger flaperon. Over the years I've heard a lot of people say the flaps do almost nothing on a Kitfox, but I disagree. They are not draggy enough to give you a lot of increased descent, but they do help. Combined with a slip the Kitfox comes down like a freight train.

But what the Kitfox flaps are really good for is increasing wing lift. I fly floats mostly, and using flaps verses not using flaps makes a huge difference in takeoff. I would estimate a no flap water takeoff will require 500 ft more water distance when flying with even a light passenger. My plane has 3 notches of flaps and I typically use 2 notches for all take offs and landings. If I need to get in or out shorter I will use the 3rd notch.

I dont have my Model 4 manual in front of me right now, but I believe the only Kitfox they talked about setting up a spoiler function on was the Model 4 Light Squared. I don't think that is any longer suggested. And while it sounds good (and have tried it on my 4), I think benefit verses risk of someone using them improperly makes more sense to not reflex the flaps. Or at least thats my take on it...

Btw, I've been flying Avid Flyers and Kitfoxes since the mid 80's in pretty much every configuration possible. I also have a Highlander, which has conventional flaps. My comments are based on my experience.

[Guy Buchanan]

On my IV flaps makes about 5mph difference in stall speed. I can therefore touch down at 30mph instead of 35mph. This reduces rollout distance by about 25%, which is not insignificant. It also gets you off sooner, but not nearly so much. Use them when you need to.

[PapuaPilot]

On my IV flaps makes about 5mph difference in stall speed. I can therefore touch down at 30mph instead of 35mph. This reduces rollout distance by about 25%, which is not insignificant. It also gets you off sooner, but not nearly so much. Use them when you need to.

Actually landing (stopping distance) is a function of the square of the speed. With your numbers the rollout would be 36% longer without flaps.

My plane stalls 6 mph slower with flaps. I believe my numbers at 1550 gross weight are 43 mph (full flaps) / 49 mph (clean).