Maximum engine size

[n85ae]

I spoke to a guy a long time ago that was doing builder assist with floats,
and he had built at least a couple with O-320's. I have an IO-240B, and if the weight
is close to the same I'd be more than willing to do it if I built another one ...

Adding an extra 30-40 hp would be great Not sure you could categorize it
as an entry level Kitfox anymore, it would be more like the advanced model,
but I bet it would be fun to fly ...

Jeff

[jmodguy]

Jeff
The published dry weight for the IO-240 is 240 lbs. I weighed mine and its pretty close at 254.
My question(s) for you is this -
What kind of performance are you seeing in your KF (climb rate, fuel burn, speeds?
Did you put your battery on the firewall or elsewhere? Any CG issues?
Is is it a one person plane?
What is your aircraft weight?

Thanks
Jeff

[PapuaPilot]

I don't see anywhere that you mention if you KF 5 has the wings swept forward 1 degree or not. This is done with the planes using the heavier engines to help with the CG envelope.

I have the IO-240B in my KF 5 and did everything I could to lighten the engine/front end of the plane including the B&C alternator and Catto prop. My battery and ELT are way back in the tail and I put the AHRS, transponder and ADSB Rx in the tail behind the baggage area. Bottom line is my EWCG was OK by .01" at the extreme forward CG calculation.

[n85ae]

My plane with IO-240B:

I have my battery in the tail, and 15 lbs of ballast by the battery also.
My empty weight is 962

Performance firewalled in level flight exceeds Vne (140), power reduced
to about 2300-2400 gives me a 120 mph cruise, I typically throttle back
to below 2000 and mush along at around 80 since I burn a lot less gas
that way.

Solo right now, with Chiberia (Chicago area) early winter temps, I get
off the ground in around 150 feet (not measured) and I get 1000 fpm+
at 100 mph all the way up past 8000 ft. If I pull the nose up to a 60 mph
climb, I get a ridiculously steep climb, but can't see anything ahead
and an indicated 1500 fpm. (this would be the "lots of Cessna's in the
pattern" show-off climb).

My plane has not much difference in either climb or glide between 80-100
and glide ratio or climb rate is pretty constant in that range, consequently
I tend to use the faster nose low climb.

I have a 74" wood Sensenich on mine.

I pretty much only fly my own plane, but occasionally I fly a Piper Archer,
Warrior, and once and a while a Decathalon, or Super Decathalon. All of
these feel heavy and underpowered.

Let's see what else? The airfoil likes lighter weights, and when it's heavy
and hot out it's not a great design. The plane gets doggy. So when's its
cold out, it's great for Valdez STOL contests, when it's hot out it feels
like a C-152 at Leadville Colorado with two fat guys on board...

The plane is a floater if airspeed is not slow, and coming over the numbers
with 10mph too much speed, will make you consider joining the Soaring
Society of America, and entering glider competitions ...

The plane sucks as a potential IFR platform, it bobs and weaves in chop.
I would put an autopilot in if I was building it all over (pre-wife), currently
since I'm budget constrained (post-wife) it's hard to justify adding it.

Regards,
Jeff

[jmodguy]

Thanks for the replies.
Papau,
I haven't set the sweep on the wings yet. The aircraft is still in assembly mode...

Jeff
Thanks for the candid info. I don't mind the batt being aft. I am building a GP-4 also and the batt is halfway down the fuse between seats and tail section. I am building it as a fixed gear taildragger (another story in itself) and the purpose of the kitfox is to provide me a means as a tailwheel "trainer". I'm also looking at electronic ignition and fuel injection (flyefii.com) and the extra ballast can be a second battery. The KF is not a cargo bird or a heavy hauler by any means so I'm gonna have a bit o' fun with it.
Will it be a screamer?? Can't go faster than 140 or it may spontaneously combust...
Will it climb somewhat spritely? I believe so...! Even with 2 souls on board.
Either way, it will be something a bit different and a bucket full of awesomesause.

My current ride is a 68 E33A with an IO520 and it is a pretty heavy aircraft but has some pretty sweet capabilities. She's fast and true and can carry a butt ton of extra stuff... Easier to land than a 172.
Hmmmm.... Maybe a retract Kitfox.....

Regards
jeff

[av8rps]

I have a set of amphib floats that weigh 230 lbs hanging under my 80 hp Kitfox 4 and it flies really nice with two guys and full fuel. And then theres my friend that flies his Model 4 with a Lycoming 0-235 on big, straight floats, so it is pretty heavy for a Model 4, but it still flies good. So with that knowledge, I personally don't believe the extra engine weight of the 0320 on a Model 5 will be that big of a deal.

Unlike so many other heavy engine options that only produce the equivalent power of a 912, but weigh significantly more, the 0-320 will make a lot more thrust with a long prop on it. Yes, it's going to be heavy compared to 912 versions, but I personally think it will be just fine. And yes, you probably will lose a bit of the light fun feel that the Kitfox is known for, but it will still fly like a Kitfox. Albeit, a thousand lb Kitfox, but it will still be a Kitfox. How can I be so sure? Simple, Avid Aircraft proved this in the early 90's when they built their Lycoming 320 powered Magnum. It used a lengthened Mk 4 wing with a bigger fuselage (only slightly larger than a new Kitfox) and the Magnum flew marvelous. 130 mph cruise and went upstairs like crazy. Oh, and typical empty weights were around a thousand pounds, with gross ultimately settling in at 1850. It was advertised as a fast 3 seat SuperCub with folding wings, a big baggage area, and a climb a standard SuperCub could never keep up with. The Magnum was a hell of an airplane...but it still flew like an Avid, just a heavier one.

Probably the only thing you won't be able to do with an 0-320 powered Model 5 Kitfox is to add another 250+ lbs to it by hanging a set of amphib floats under it, or at least not without adding some additional wing area. And you would also be tempting fate by pushing the design gross weight beyond reasonable common sense. (The McBean Kitfox sales force is good, but they really don't need a structural failure to further challenge them...)

And yes, it's gonna be nose heavy, but to cure that move your battery back and then build a larger fuel header tank (and maybe even a tool kit and a heavier tailwheel spring) that installs at the back of the baggage area. Then the only way you will get out of cg is when your engine quits because the header tank has been exhausted of fuel

Of course, your thousand pound Kitfox will make a lousy LSA, with even less legal useful load than the 180 hp Carbon Cub. But hey, the carbon Cub LSA sells well at three or four times the cost of the Kitfox, so who am I to judge? (And frankly, I think it is just a matter of time before John McBean comes out with a really slick 180 hp "Carbon Kitfox". There would probably be a line forming to get one of those...just say'in).

You know, someone has to do it. How many years have all of us wondered how an 0-320 would work on a Kitfox? I know I have. And even though it goes against the "purist" beliefs, I can hardly wait to hear how it works out!

So I say go for it!

Paul Seehafer
Central Wisconsin

[PapuaPilot]

It will be interesting to see how an o-320 works on a Kitfox. You mentioned putting a long prop on, just be careful that ground clearance is maintained. You could always get a custom made landing gear or put height extensions on the gear you have.

[jmodguy]

Paul,
Gee if that didn't sound like a "triple dog dare".... We're on!

Phil
Whirlwind makes a prop for the 320 that is available in 68, 70, and 72 in. The Whirlwind 3 blade STOL prop for the 912 is 70 in. Should be ok there.

Anyone need a FWF kit for a 912??

Regards,
Jeff

[jmodguy]

To make it interesting... I have a 340 stroker kit that is slated for the GP-4!

[WWhunter]

[QUOTE=
The Whirlwind 3 blade STOL prop for the 912 is 70 in. Should be ok there.
Regards,
Jeff[/QUOTE]

The Whirlwind STOL prop on my 912 is a 75" 3-blade.