KF3 wing convert to KF4?

[Dave F]

582 readsy to roll is 110 lbs

912 is about 165 lbs

Honda -- not sure but 180 to 200 lbs ready t o go.
Impressive static test showing about 40 to 60 pounds more thrust from the honda so let's say 10% more
So take in account another 40 lbs or so that iwll cost you about 200 fpm climb rate loss so the 10% more Thrust might not make up what is lost in adding wieght.

SO many just continue to build tanks --adding weight that is just plain dumb.

My opinion but I do like the honda engines.

[Geowitz]

Not to spitefully answer questions you weren't asking, but I agree with the previous 2 posts. You may have a bigger concern with the weight and balance. On models 3's and earlier you need to pay extra close attention to not being nose heavy.

[NotSoAmish]

Vikingaircraft specifications are that it is 13 lbs. heavier than the 912ULS and the same weight as the Jabiru 3300. Are there no 912ULS in any KF3? The Viking is 178 lbs.

[DesertFox4]

No model 3's with a Rotax 912ULS (100 hp) that I know of. Several with a Rotax 912UL (80 hp) engine. I flew one for 3 years with the 80 hp Rotax on it and it was a great performer. Not sure I'd want any more horsepower on that airframe though or more weight on the front. The 80 hp. Rotax with the right prop. could easily accelerate past VNE in level flight using 80 to 85% power.

[rogerh12]

This year at Oshkosh I saw a "JUST" aircraft with a Honda Viking motor mounted. I was surprised at how compact it was. It looked good too, and the owner liked it quite a bit too. Here is a pic


I figure it weighs in around 185 lbs, but that's just a guess, might be closer to 200 lbs.
email me if you want the whole set in high deffinition.
Roger

[Av8r3400]

I spent quite a bit of time talking to these guys, too. Remember a Just Escapade is not a Model III Kitfox. It's a much larger and heavier aircraft that can handle the weight and thrust of these motors.

[desertfox1]

A Just Escapade is not a model 3, more like a model 4 with a model 3
airfoil and a longer fuselage. A 1232 airframe that became 1320.
I try to build the lightest airplanes i can each time, but I have flown
"heavy" planes that are very nice to fly, just giving up some performance.
Looking forward to see more real world experience with the Viking and
it will take experimenters to provide that for us. My planes are model 5
and 7 SS but I sometimes fly a friends heavy model 4 with 1 degree
forward swept wings to offset the heavy engine. What a blast, not as
fast but 1500 feet per minute and solid as can be. My point is that if
someone builds an airplane that is not what we fly, he is not dumb, he
is an experimenter, and we can give what guidance he asks for.

Just my opinion

Phil

[NotSoAmish]

Herea are the engine weight comparisons from vikingaircraftengines.com?
Viking 178 lbs.
Rotax 912 ULS 165 lbs.
Jabiru 3300 178 lbs.

and from Great Plains documents

VW 2180 164.5 lbs.
VW 2276 165 lbs.
VW 2180 red drive 180 lbs.
VW 2276 red drive 180.5 lbs.

Can someone explain what it is about the KF3 frame that concerns them with trying this 178 lb. Viking engine? is it torque? So no one has a VW with a reduction drive in a KF3? And what about all the KF 3s with lotus floats?

[rogerh12]

I can't comment on the other engines, but the redrive VW is very heavy (total install weight with prop) and does not get anywhere enough cooling at Kifox airspeeds to be usable ( others have found).
The direct drive VW is installed in a few Kitfox's and has a total installed weight (with wood prop) of about 185 lbs, which is on the high side, but workable (75-85 HP). A large oil cooler must be used to cool this engine in the Kitfox, but air cooling of the fins is not an issue with proper baffling. A required 60-62" diameter prop limits cruise speeds as not much pitch can be used (though 100 mph+ cruise speeds have been reported in at least one install & and a decient rate of climb).
Also, the Subaru EA-81 is used on some versions of the Avid, and despite the extra weight they still fly good because of the extra power to offset the extra weight of the engine, and also water cooling that works even at kitfox speeds. Power off the redrive at the prop is about 85 HP (though this is all info off the grape vine, I have not seen anything in print)

[Av8r3400]

I would suggest taking these numbers with a large grain of salt.

I have a 912 UL (80 hp) on my engine stand, with oil and Kitfox IV mount still attached, no coolant or prop. Per my scale it weighs 158 pounds.

Are they comparing a fully assembled weight on the Rotax/Jab versus a striped down Honda with no PSRU, oil, coolant, electrical system, etc, etc?

Remember these are sales brochure numbers.


Like the debates about VW motors, I (personally) wouldn't say don't do it. I honestly hope it works out for you and exceeds your expectations on performance. We sure could use more engine alternatives. I'm just trying to offer a devil's advocate point of view to show possible pitfalls or problems.