Nice Kitfox Model 3 gross weight question

[skyguy04]

Hi all,
I have a buddy that is looking at a very nice Kitfox model 3 that has been upgraded with 4 wings, 4 flaperons, and 4 flaperon mixture and baggage compartment. To do the modification to model 4 flaperon mix and baggage, it looks like 3 tubes have been cut out. I emailed Debra and she sent me a PDF of a "Denny retrofit" that I guess Dan Denny put together himself. It involves cutting out some tubes in the baggage compartment area but we can't tell specifically if the correct tubes were cut (probably so). The owner is not the one that made the modifications.

First, is anyone familiar with this Denny retrofit and could tell us if it was done correctly. Also, what impact does this have on the airframe integrity? See attached photos.

Second, the owner said the previous owner told him that, because of the modifications, it should be a 1200 max gross aircraft now. Does anyone have any thoughts on this? It seems to me like there is a still a lot of the 3 fuselage left such as carry thru spars, smaller diameter tubing, smaller empennage, etc. We don't think the gross weight change was done officially. If it should be 1200, what's the correct method of changing the gross weight to 1200? Put it back into Phase 1? Can a non-builder do this?

Thanks!

Brian
Model 4 Speedster

[109JB]

Definitely NOT a 1200 lb gross weight. In addition to the wings, changes were made by the factory to the fuselage to get the 1200 lb gross weight.

[Av8r3400]

This mod will basically make it a 1050 model 4.

[skyguy04]

Thanks Larry and John. The only problem I see with the gross weight is that the plane is 756lbs empty now on a 1050 max gross. With full tanks, that leaves enough payload for a single passenger weighing 132lbs or less. Pretty crappy. Not sure why someone would do that mod unless they plan to fly over gross a lot.

Oh well, think I’m going to recommend my buddy pass on this one.


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[109JB]

It isn't the wing mod that made it heavy. It is something else. I had a Kitfox 3 with the kitfox 4 wing conversion and it weighed 560 pounds. I also had a kitfox 4 1050 and it also weighed 560 pounds empty. Both built light with Rotax 582 power and both weighed by me.

[skyguy04]

This one has a Rotax 912UL on the front of it. I’m sure that contributes a lot


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[Av8r3400]

This one has a Rotax 912UL on the front of it. I’m sure that contributes a lot

My old 4-1050 had and empty weight of 650 with a 912UL. The Mangy Fox (4-1200) with all of its extensive mods, reinforcements and a big bore 912UL is only 700 empty.

The first thing to address is *why* the plane has a 750# empty weight and what can be done to put it on a diet...

[109JB]

This one has a Rotax 912UL on the front of it. I’m sure that contributes a lot


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There isn't 200 pounds difference between a 582 and a 912. More like the 912 should add 50 pounds. You should still be somewhere in the 610-620 pound range. There is 150 pounds of extra weight there somewhere. On the model 1-4 but especially the 1-4/1050 the key is a light build.