performance numbers

[wannafly]

Now that I can get to the numbers in the Kitfox manual I have a question with the cruise speeds. In the airspeed limits section of the manual it states a VNo of 108 mph and VNe of 140 mph. Then you go to the performance section and the VNo is at 115 mph for the speedster. Which one is right?:confused:

[DesertFox4]

Vno- def, maximum structural cruising speed (the maximum speed to be used in turbulent conditions) or can refer to the velocity of normal operation. VNO is specified as the high end of a green arc on many airspeed indicators.



this is all I could find on it.
Skystar, 7/19/94 Speedster model 4

Vne 140 mph
Vfe 70 mph
Vno 108 mph

115 mph just sounds high for VNO.


Maybe John can confirm these.

[Av8r3400]

My IV-1050 has a VNE of 125 mph, VNO of 108 mph, VFO of 70 mph.

My IV-1200 has a VNE of 140 mph, VNO of 115 mph, VFO of 80 mph.

(Both are long wing planes, not the clipped wing speedsters.)

I was told one of the main reasons for this is the fact that the 1200s have two anti-flutter weights per flapperon, where the 1050 has only one on each side.

[SkySteve]

Does this mean the VNO and VNE can be increased on any Kitfox wing that only has one anti-flutter weight just by adding a second anti-flutter weight?

[DesertFox4]

Steve, as we are learning the V-speeds can be model specific.
Remember that the Model 4 has a totally different wing, flapperon and even control mixer than the earlier models. Not sure I'd want to assume that one applies to the other. If you've ever experienced flutter during flight and survived it, you will have great respect for tested airspeed limits.:eek:
Something to think about as we celebrate 25 years of Kitfox flying , our "fleet" is aging now and wear on critical parts like control mixer parts , especially the 1-3 Models that used the "blocks and bolts" should be monitored and addressed if excess play is found. Kitfox has a stellar safety record and it'll be up to all of us to keep that intact.

[SkySteve]

Makes sense. Another angle of the same issue: Would adding a second anti-flutter weight to a single weight wing (model 1-3) make that wing a more stable and safer wing, or is the single anti-flutter weight wing what it is and can not be improved without a change in design?

[DesertFox4]

Steve, someone else is going to have to cover that question. It's a little above my pay grade.

[rwaltman]

... Would adding a second anti-flutter weight to a single weight wing (model 1-3) make that wing a more stable and safer wing ...

The first thing that comes to mind is not, of course. The single balance weight in older models has the necessary mass to balance the whole flaperon.

Spreading the mass into two weights to reduce the torque along the system means that the existing weight should be replaced by a smaller one, and the optimal size of each will depend on their location.

Any volunteer to do some flutter testing from scratch?

Roberto Waltman (*not* an aeronautical engineer)

[Jerrytex]

I saw a few pictures of KF 4s and I noticed that some have two mass balance weights on the flaperons. I found this post and there is talk about a KF 4 having two per side also. The original flaperons that I have only have one on each side. I was wondering if this is something I need to address? I bought new flaperons and they are still in the box so if I need to add or change something on them, now is the time.

[Newkid]

The two flapperon weights have the same mass of one flapperon weight. When the Speedster came out they went to the two weight system. The reason for this was that when doing high G maneuvers the flapperons would flex and bind until the G load was lessened. So to fix this they basically cut the flapperon in the center leaving the spar untouched and put a tab on the trailing edge at the cut. So each half of the flapperon got it own counterweight. This would allow the flapperon to flex more without binding. So unless you are Jimmy Franklin the single counter weights are fine. Also Speedsters had a 140 mph VNE because they came with an .090 windshield compared to the stock .060.

[Jerrytex]

Thank you Newkid. One less thing to deal with. Now if the SNOW would quit, I could finish the paint on the wings and get flaperons installed. Snow in south central Texas... What is this world coming to?

[Paul Z]

Jerry texas I posted some snow pictures on the Skis thread. What is yours like?

[Jerrytex]

Hello Paul

I posted a pic under yours. Not as much snow but it rained about 1/8" right before the snow started so the roads are real bad.

[Paul Z]

JerryTex,

I can remember back in 1973, snow in Bryan/College Station aqbout 6 to 8 inches. It doesn't occur there often! I'll have to fly down to visit once I get my Carbs Balanced!

Paul Z
Gig'em Class of '73

[akflyer]

Must be that global warming thing.

[Jerrytex]

Paul that would be great if you fly down. Would give you an excuse to go flying. Holler at me when you do and I'll take you to lunch.

[Paul Z]

As soon as I get the carbs taken care of and about 5 hours of testing. I'll make plans. A good reason to visit College Station!