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Old 11-07-2008, 01:53 PM   #1
JRR
 
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Smile kitfox 3 vs 4

What are the differences between a 3 and 4?

I'm interested in getting a Kitfox, used. I was told the one I'm looking at is a 4. Now it's a 3. So I'd like to know the difference. Thanks much.
Jim
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Old 11-07-2008, 03:55 PM   #2
DesertFox4
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Default Re: kitfox 3 vs 4

Jim, The model 3 had a different wing and flapperons than the 4. The 3 wing has undercamber to the bottom side of the wing for more lift but is a slower speed wing. The 3 has a shorter rudder than most 4's although the earliest model 4 has a shorter rudder too. The gross weight on a 3 is 1050 lbs. The shorter ruddered model 4 also carries the 1050 lbs gross weight. If it has a 1200 lbs gross weight and tall rudder , and no undercamber to the wing it's a 4. Also the control mixers are different for the 3 . If it's a model 3 (more complicated) you won't have to disconnect the flapperon control rods to fold the wings. There are other small diffs. but these are the most apparent. Both the 3 and 4 used Rotax 912 four stroke and 582 two stroke engines so the engine it has or is set up for will not help much.

Model 3
1. Under-cambered wing. (Slower cruise speeds but high lift wing)
2. Shorter vertical stabilizer/rudder
3. Gross weight of 1050 lbs.
4. More complicated control mixer/ no disconnecting flapperon control rods to fold wings.
5. VNE of 100 mph or less (mine was 98 mph)
6. Airfoil shaped flapperons(models 1,2 & 3)

Model 4
1. Flat bottomed wing. (faster cruise speeds with this wing)
2. Early 4's have shorter rudder. Later 4's have taller rudder.
3. Early 4's 1050 lbs. gross weight later 4's with tall rudders 1200 lbs.
4. Simpler control mixer. Must disconnect flapperon control rods to fold wings.
5. VNE of 120 mph or faster depending on Speedster mods and windshield thickness.
6. Symmetrical flapperons.

Jim, if I've forgotten any major easily spotted differences someone will respond.
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Old 11-07-2008, 08:17 PM   #3
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Default Re: kitfox 3 vs 4

Not bad Desertsfox I give you an 8/10 for Kitfox Model knowledge.

The Model three also had wooden Aileron hinge attachment points these were a continuation of the actual wing rib. The Model 4 and onwards departed from this method and employed separate metal fittings which attached to the ends of wood ribs to serve the same function.

I also understand that the later model 4 had thicker carry through tubes for the wings attachment and thus the heavy load capability. The struts on the Model 3 and 4 are the same and attached at the same point along the wings spars. The 3 and 4 are very similar in structure almost the same.
Aerodynamics and the flaperon mixer were the main differences.

I'll be happy with a 5/10
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Old 11-07-2008, 09:48 PM   #4
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Default Re: kitfox 3 vs 4

some of the 3's were retrofitted with metal reinforcements on the wing rib/flapperon attach points so that may not be a definitive item for qualification of a 4 over a 3 unless the buyer knows what a 4 bracket looks like and a repaired 3. That was a recommended repair procedure for any flapperon attach point that was broken in an accident. The carry throughs may not be apparently bigger to a novice so I was keying in on very apparent differences but your points are spot on if the buyer is really up on his Kitfox models.
I do think though that the struts were beefed up also on the later 4's. 3/4" to 1" struts maybe. I could be remembering wrong. I am getting old.

Jim - other things to consider if deciding between a 3 or a 4 are what kind of flying you intend to do. If you want to fly with other Kitfox's and they are 4's , 5's - 7 SuperSport then the 3 will have a tougher time keeping up with them even with the 912 Rotax and a controllable prop. The model 4 will do pretty much everything the 3 can do and fly quite a bit faster in cruise. The 3 will cruise at 80 to 90 mph real well and the 4 will do 110mph pretty easily. I'm comparing with a 912 installed. The 582 will be slower on both models. The 3 gets off extremely quick with the 912 but the 4 will probably climb as quickly. I loved my model 3 but the the 4 was quite an improvement in speed with little or no sacrifice in climb and can carry more load.
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Last edited by DesertFox4; 11-07-2008 at 11:16 PM.
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Old 11-08-2008, 09:48 PM   #5
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Default Re: kitfox 3 vs 4

Hi, my model III Had the metal aileron brackets attached at the time of construction, I thought it was a factory upgrade. I wouldn't have an aircraft with out them.
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