What is the “highest” HP someone has put into a Kitfox?

[kitfoxjim]

It's fun to think about what it might take to beat Draco in the STOL Drag races.
Rik's turbine with that weight has a superior power to weight ratio.
Standard wing KF is faster than Trent's. With the available power, acceleration to Vne will be quick. Beta prop deceleration at the line could be the deal breaker. Again there is plenty of power with timing being everything.

The overall power to weight ratio compared to Draco should be a distinct advantage.
Big tires would enable a larger diameter prop, but might require some positive thrust angle to counteract drag, but this would also help during heavy deceleration!
The airplane would be pretty much a purpose built machine, maybe not practical for everyday use, but I think a capable competitor!

[Rik]

Thanks.. a purpose built plane is just that, purpose built.

I’m thinking outside what some would think is normal and an even further outside would be having the ability to reconfigure the plane for certain missions.

Small wheels and fairings for travel, large wheels for other missions, smaller motor when power is not needed and of course the big one when power is needed. These are all bolt on and take off things. Some work involved yes but the attraction to the “Experimental” is this ability to make changes. Some ideas I don’t want to even mention as I don’t need to have people stand upon their soap box and preach just because they do not have the knowledge/experience/desire to achieve certain things.

Seriously, my only reservations about a Rotax are that the new turbo one is going to be a $50k item in the plane if not more. I think it’s an absurd amount of money plain and simple for what your getting. If I’m going to spend that then I can spend x instead and have something for the cost.

[aviator79]

I don't think any comments you have gotten here come from a lack of knowledge, experience, or desire. All I see is frank discussion of the topics you asked about.

Get on it. I'm sure we'll all be interested to see how it turns out.

[Rik]

Thanks, but I still haven’t decided on a plane yet..

I need to do a lot more research first.

[Clark in AZ]

Maybe take a look at the Bearhawk Patrol? VNE 165, cruises at 150+, lands at ~35, holds 55gals of fuel. Might be a good fit for your engine?



https://bearhawkaircraft.com/patrol-specifications/


Clark

[Esser]

I think a regular bearhawk is the ticket. I would only do what you want to do on a Kitfox if you stretched the fuselage an extra two feet. You’d need a large fuel tank behind the pilot seat for an extra 30 gallons.

I don’t think the Kitfox is the plane for a turbine. Sorry to be a kill joy.

Anytime you do something like change an engine, you are supposed to put it back in he flight test phase.

[Flyboy66]

I am not sure if you were referring to me with the soapbox comment, but I don’t think I ever told you it wouldn’t work. I was only stating the problems that I thought you might encounter with your project if you decided to move forward with it. We obviously disagree on your power, speed and fuel flow statements, but I haven’t operated your type of engine, and you haven’t built the plane, so we don’t know if either of us is right or wrong.


I am not the most experienced guy on this forum, but my comments weren’t made without some life experience. I am familiar with turbine engines. I have over 4000 hours behind TPE331’s, 1200 with PT6’s, 500 with PW119’s, 975 with JT8-D’s, 11000 with CFM56’s and similar with IAE V2527’s.

If you want to refute or explain why the things I said were invalid or that you have a “work around” for them, then I am sure it would be interesting reading for everyone. Draco is a prime example of what creative problem solving can accomplish. The beauty of experimental aircraft is that you can make them what you want them to be.

I believe that the recommendation from the others regarding the Bearhawk is spot on for what you are trying to do, and that it would have far fewer snags than the Kitfox would have.

Whatever you decide, I would love to follow your progress, so keep us posted.


Steve

[Slyfox]

since it appears you have unlimited money. maybe. Why not build two airplanes, one just for the turbine and for competition. the other for fun flying into the back country. I have two. one for cross country and one for back country.

[redbowen]

Rik, your original question is about how much HP can a Kitfox handle, assuming a model 5-7. It has options from the factory, tested up to 180hp with the Titan 340 install. As others have stated, hp above the standard 100-110hp is not going to help much with cruise speed because of the drag characteristics of the airframe, but the HP will help you accelerate and climb. Adding weight to gain HP is definently a trade off. I run a Lycoming O290 130hp, but weigh about 80lbs more than a Rotax install. I love it, especially at sea level, but at high DA I cn feel the weight as the power drops off. This is the main reason that I am doing a Yamaha conversion in the future. At 150hp, without a turbo, and only 5-10lbs more than a Rotax 912, it is a great solution that has been proven to be reliable in other airframes. The new Yamaha Sidewinder with a factory Turbo that is cable of 220hp in its stock configuration would be more HP than the Kitfox can really utilize other than in a STOL Drag or STOL T/O application. So, 400+hp I don't see how you can utilize the power.

The STI wing vs standard wing: First off, you know nothing about Nikk's situation and drawing a conclusion on the cause and making a ridiculous statement about the standard wing being scary just shows how much you don't know about the Kitfox. I actually take offense to you referring to this accident to support your statement, considering Nikk is a friend of mine. The standard wing, which has a fantastic safety record and is very predictable, is on the vast majority of all Kitfox 5-7, has a stall speed around 40mph. This will vary based on weight, installation/rigging and VG's. The standard wing will cruise nicely at 110-120 and is capable of 140mph. With the STI wing you can expect a slower stall speed by around 10mph and you can expect a loss of 10-20mph in cruise speed. You will also loose some of the snappy response that the standard wing has, the STI is slower in roll response. I fly often with an STI equipped Kitfox and can definitely see the difference in STOL performance compared to my standard wing, making it the better choice for off airport short operations.

STOL Drag: Before you build a purpose built STOL drag aircraft to compete with Draco, you may want to come out and compete to see how you do. Bring whatever you fly now, assuming you do. It is a lot more about the pilot than the aircraft than you think. Especially getting into the top 16 for the finals. In the finals HP and aircraft becomes a bigger factor. If you look at the times in the finals you will see that the top two times were the best power to weight ratio aircraft, Draco and Steve's Yamaha Highlander. Trent out performed the carbon cubs and again he had a better power to weight ratio with the Turbo powered 915. The key to do well is Pilot skill, light weight, and high horse power, in that order. The turbo powered piston engines will be the future of this race at least until purpose built electric airplanes are built. That is because of the elevation that the race is conducted at. You loose 2-3% hp per 1000' of altitude, so the NA guys are loosing HP but still weigh the same. The Rotax 915 still retains its sea level horse power and that's why it does so well against the Carbon Cubs. I think a Turbo Yamaha powered light weight set up can compete with Draco. The big advantage Mike has is the beta prop. Steve Henry is going to show up next year with a 300hp Yamaha Highlander and it will make for a good race.

A turbine in a Kitfox is something a lot of us have talked about and unfortunately the fuel burn and fuel storage is going to be your limiting factor. I am unhappy with my range at 3.5 hours running the Lycoming O290, so a 1.3 hour range would be impractical for an airplane you actually plan on going out and flying anywhere. There was a guy that put turbine in a Zenith https://www.youtube.com/watch?v=w5zpjQ1lmo4 and the limited flight time made it a huge disappointment. Now you could increase the fuel storage, but now you are changing the airframe design and load distribution. It can be done right, but like others have suggested, with the type of HP you are talking about, a larger airframe would better utilize that power. Bearhawk, Backcountry Cub, Sherpa, Murphy.

If you can be mindful that you are on a forum of people that have vast experience and love for the Kitfox. They are providing you helpful information based on that experience. Some of your responses seem not to acknowledge this and can rub people the wrong way. We don't know your background, so when you draw conclusions about the design without ever owning or flying one, it lowers your credibility. That being said if there is information that we can contribute to what you are trying to accomplish than I for one am happy to do so as long as you are respectful. Experimental Aircraft are just that, experimental, I am all for trying something other than a standard Rotax 912 install.

[GMKman]

Well put Bryan!!
I love and trust the standard wing a lot especially after putting vg’s the same place you did in your video. Very docile and predictable. I personally like the faster cruise speeds of the standard wing and it lands plenty short enough for my flying taste aka dirt roads, playas, and ultralight strips.
I’ll definitely be following your Apex build intently as I’m very interested in a lighter/ economical/ more powerful engine. Win/win/win. In my book.