Maximum engine size

[Russway]

I'm still in the dream stage, and I've purchased nothing. Realizing the engine is just as important as the airframe, I've found an interesting option. Superior Air Parts in Coppell, Texas has a build school. You can build a new engine under their supervision, or you can watch while they build it for you. I haven't called about availability or pricing because I have concern about the size. Their smallest is the XP-320 (cubic inches), 160 horse power, at 290 pounds overall weight. I haven't found a definitive limit, but the Kitfox website mentions projects built with all types of engines 150 hp or less. So......., is this engine even feasible? Thanks for your input.

[Danzer1]

Russ,

I have explored just about every engine out there up to 225lb dry. With that weight there are c.g. envelope issues if not careful. Potentially adding weight to the tail and further limiting as the wing tanks empty or flying solo. Neither looked like options/conditions I liked. I would call 290 a no go in my book.

Currently leaning towards the UL 350is, other than high price with the current Euro exchange rate, it is seeming more appealing to me everytime I compare it to anything else.

Greg

[n85ae]

I believe there have been a few O-320 powered Kitfoxes built, wish I could
remember who was doing the installs. If memory serves correctly the
primary reason was for use with floats.

Regards,
Jeff Hays

[airlina]

Russ, I have an I0-240 on my Series 5 that is around 250 lbs and I would say that is about as much as the airframe can stand C.G. wise. With forward swept wings, and my battery in the empennage I keep the C.G. in limits, but with 290 up front, you would be adding lead in the tail to keep her balanced. Bruce N199CL

[Gravity_Knight]

Also curious about this. I have a sport license now, but have been considering "upgrading" to a private. Operating at the 1550 instead of 1320 MTOW so I could legally run a larger engine, and still fill up on fuel etc. I live at 6700ft elevation in colorado and fly to 14,500 in the mountains quite often. I don't have a Kitfox yet either, but plan to buy one with a 912, so I'm just looking at options for down the road...

[Russway]

Thanks all. I figured as much. I knew that the mere idea of a build your own option so close to home was just too good to be true.

Russ

[Gravity_Knight]

The Lycoming IO-233 doesn't look too bad... 115hp, 2400 TBO, and 213 pounds dry.... new it's $25,000 which is not in my budget, but one can dream

[War Eagle]

Also curious about this. I have a sport license now, but have been considering "upgrading" to a private. Operating at the 1550 instead of 1320 MTOW so I could legally run a larger engine, and still fill up on fuel etc. I live at 6700ft elevation in colorado and fly to 14,500 in the mountains quite often. I don't have a Kitfox yet either, but plan to buy one with a 912, so I'm just looking at options for down the road...


Another option you could go with is the turbo charged Rotax 914. No density altitude problems and less weight and full 100 HP to somewhere about 16k feet. You'll likely save at least 70 to 80 pounds dry weight and climb rate will be pretty nice too.

[GuppyWN]

Another option you could go with is the turbo charged Rotax 914.

MSRP is $32 tttttthousand!

[Av8r3400]

I can think of no reason what so ever that a person would want to put a 300# 320 Lycoming on a Kitfox.

Any power gain would be more than negated by the weight of the motor, not to mention the ballast needed in the tail to balance that giant anchor hanging on the nose. Plus you need to factor in a 10 GPH fuel burn (yes, that is realistic) so you will need to haul around a ton of fuel all the time, too.

An O200, IO240 or 233 Lycoming are probably near the weight limit for a Kitfox to still have a reasonable useful load.

Even at your altitudes, I think you will find the performance of the 100 hp 912 to be just fine in what should be a very light weight plane, Sir Gravity_Knight.

[Danzer1]

Even at your altitudes, I think you will find the performance of the 100 hp 912 to be just fine in what should be a very light weight plane,

That might depend on the mission and the density altitude at the time. We very often have 8000'+ density altitude which would give that engine max at takeoff 76hp (for 5 minutes). Drop that to max sustained at 5500rpm and it's closer to 70. The 912hp curve drops off even quicker from there. Cruise at 4000 and it's down to 67hp (s.l.) and closer to 51hp at 8000 d.a.

That might work for some.

[Dorsal]

Cruise @ 4000?? My typical cruise is 5200 RPM.

[Danzer1]

Dorsal, That's kind of my point - you can't. The idea when flying from altitude airports, with high d.a.'s and potentially in or above mountainous terrain, is to have as much "get out of trouble" power available as you can on the right side of the curve. To illustrate:

I picked 4000rpm, as in a direct drive you often would cruise at 70 to 75% and in a 912 you really can't.

Using your number of 5200, about 95% or about 2100 prop rpm and approx. 90hp (s.l. ratings). You only have about 5% of the curve left for "get out of trouble" hp.

Compare that to say the UL 350is at 2100, about 63% and about 94hp (again s.l. ratings for comparison). You would still have 1/3 of the power band left - 36hp and 1200rpm of "get out of trouble" power available on the right side of the curve.

More safety margin before running out of engine. And, installed weights compare almost equally for lbs/hp fwf.

[Dorsal]

I think you will find that 5000 rpm is 75% power.

[Danzer1]

Not sure how you figure that - 5800 is max for 5 min and 5500 max continuous. Even if using hp ratings or prop speed at those figures, nothing comes out to 75%. Can you expound on your thinking as to how 5000 rpm can equal 75% power? I'm not following.

[Av8r3400]

Why would you? 5000 rpm is a common cruise rpm that yields 3 - 3-1/2 GPH. Why turn slower?

Danzer1, you need to speak with some folks, like Stick and Rudder, who run these motors in a Kitfox at altitudes like you want, to understand.

[AirFox]

I agree with Larry(Av8r3400) above. I was considering other engine options until I went to Stick & Rudder and experienced what they have. "Been there and done that" advice goes along way when deciding what engine to go with. You will be amazed at what Stick and Rudder planes will do!

Scott

[Dorsal]

Danzer,
Page 5-6 Rotax owners manual, 75% power @ 5000RPM = 68HP (that is 75% of 90hp which is Max continuous).
Given I don't have a IFA prop I take off and climb @ 5200 rpm which is ~75HP, same as I could get at 8000 ft DA at around 5600 rpm.

[Danzer1]

I understand what the plane and the engine can do. I have a choice and an opinion. It is my choice to prefer 30% of overhead to 5% of overhead (from cruise).

Why don't you guys ask them? Their runway is at 1/2 the height, their summer temps don't very often get to 100 deg. They don't have any 14,000 foot peaks, we have many and many passes over 10,000. Matter of fact, most of Idaho including the peaks is under 8,000 feet and the vast majority under 3000 ft!

So starting at 5,500 ft. adding 95 to 100 deg (8000+ d.a.) and having passes and peaks of 10,000 and above - my choice and opinion is go for as much margin as I can.

The thread was asking about an SS7 and Larry you threw in the 100hp 912. That would presumably be a 912ULS. How are you calculating/getting 3-3.5 fuel burn at 5000rpm? When the factory says 5.3?

[Danzer1]

Dorsal,

I think we are talking about a 912ULS (100hp was given), 95hp continuous at 5500. 75% is 71.25 which occurs at 4,125 rpm. In any case, maybe you are reading kw not hp, it still does not compute.

Greg

[Danzer1]

Dorsal - I see where our confusion is coming from. I'm reading the 912ULS info from these charts: http://www.rotaxservice.com/documents/912Sperf.pdf

Which is vastly different info than shown from your reference (both from Rotax). So if the info in the Operators Manual is correct - it has much less power and "reserve" than I had been calculating!

Hmm

[Gravity_Knight]

Even at your altitudes, I think you will find the performance of the 100 hp 912 to be just fine in what should be a very light weight plane, Sir Gravity_Knight.

You are correct.. I fly a CTSW now with a 912. Empty it weighs 710 pounds and does pretty well. Although, on a hot day with the DA at 10,700 (highest I've flown in) here with two people and fuel it gets pretty anemic. I like taking friends around Pikes Peak and at 14,500ish it can be a challenge (obviously only going in the morning when DA's / wind are lower) I've flown to Leadville as well with a passenger and climb performance isn't anything real exciting.

To me, lots of power makes a plane safer. My homebuilt runway is about 2200ft, but obstacles on both ends so around 1800 usable. This is plenty for a 912 powered kitfox even up here but I think 115hp or something that is turbocharged up at this altitude would make me feel better. I also come from the drag racing world so a little more go puts a smile on my face :)

But at the end of the day.. when I can afford my own plane (Kitfox) w/ a 912 it will still perform well enough to have a blast I'm sure!

[Dorsal]

Danzer,
I think your numbers are more correct, the table I was referring to is recommended setting for a variable pitch prop.

[n85ae]

The dry weight of an O-320 is within about 5 pounds of an IO-240B, and even
if you add ballast in the tail you aren't adding a gazillion pounds back there
to get the balance worked out. So yes there are reasons to use an O-320

Regards,
Jeff Hays
N85AE, Series 5, IO-240B



I can think of no reason what so ever that a person would want to put a 300# 320 Lycoming on a Kitfox.

Any power gain would be more than negated by the weight of the motor, not to mention the ballast needed in the tail to balance that giant anchor hanging on the nose. Plus you need to factor in a 10 GPH fuel burn (yes, that is realistic) so you will need to haul around a ton of fuel all the time, too.

An O200, IO240 or 233 Lycoming are probably near the weight limit for a Kitfox to still have a reasonable useful load.

Even at your altitudes, I think you will find the performance of the 100 hp 912 to be just fine in what should be a very light weight plane, Sir Gravity_Knight.

[jtpitkin06]

The development of the Kitfox is not unlike the Piper Cub evolving into the Super Cub.

The Super Cub started with an empty weight of about 800 pounds, 95 hp and a gross weight close to 1500. Sound familiar? Various engines have hung on it from 105 hp up to the “standard” 150 hp. Piper built one with 180 hp and several have been re-engined to 180 hp with an STC.

I suppose one could ask, “why would you want to put a bigger and heavier engine on the Kitfox?”

Let’s say you have a light Kitfox loaded to 1100 pounds and the power is 100 hp Rotax. That’s 11# per hp.

So let’s hang a heavy but more powerful engine on the front and balance the aircraft with a few pounds in the tail (if necessary). We’ll add 160 pounds and we are now at 1260. (Another familiar number) with 150 hp on tap. That’s just 8.4 pounds per horse power with spritelyclimb performance.

“But what about the wing loading?” you say. OK, in the light weight Kitfox you have 1100 pounds / 132 sq ft = 8.33 pounds per sq. ft. The heavier engined Kitfox example is 1260 pounds/ 132 sq ft = 9.54 pounds per sq ft. That’s about the same as the clipped wing speedster version. The only problem I see is that it would be bumping the redline in cruise.

I don’t see the CG as a show stopper. I have my Corvair engine mounted 4 inches further aft than the O-200. The CG is not a problem. No ballast required.

I see no reason why an experimental aircraft builder might want to push the envelope and install a different engine in the Kitfox airframe even though it does not meet the “norm”. Kitfox LLC has done this when they installed the Rotec Radial and then the Lycoming 233 . That’s what experimental aviation is all about. We try different things, different engines and different panels.

I would go so far as to say if someone puts a 160 hp engine in the Kitfox and shows up at Oshkosh they would have an instant crowd around the airplane. I’ll be standing in line to get a ride in what will likely be a screamer.

John Pitkin

[n85ae]

I know that there are a couple of O-320's out there, the problem is I just can't
remember who the guys were that were doing it. But they built a few of them.
It was at least ten years ago, and I recall talking to one of the guys on the
old Sportflight list.

I personally would consider it myself if I were building my plane all over, I have
been flying the IO-240B for a long time, and I think an extra 30-40 would
be a blast. So yeah, why not? I would do it.

Regards,
Jeff Hays

[jiott]

I agree with John. The only other thing would of course be a careful look at the engine mounts and firewall attachment for all that extra weight and power. I personally think an engineering calculation by a knowledgeable person would be in order. Torque reaction on sudden engine accel, as on a go-around, might also be quite exciting!

Jim

[n85ae]

There would not be a weight issue, the dry weight of an O-320 is about
250 pounds, the IO-240B dry weight is 246 pounds. It would balance fine.
You would need to build a new engine mount and probably upgrade the
forward fueslage tubing. There might be "some" torque reaction but I
bet not that much. The more I think about it the more I want to build one :)

Jeff Hays

[airlina]

Jeff, you better finish the one in the garage first!

[Esser]

I'm sure lot of you know that I am planning on putting a UL520i in my plane. My question is do you think that I should enlarge the rudder create a control horn at the top for it? Having never owned a Kitfox before I'm not sure if the larger rudder is needed or not.

[SkyPirate]

I would think you might need to do something concerning P factor and allot of horse power,..an equalized rudder maybe

[n85ae]

That one doesn't count, that's the secret airplane ... However after that I'll
build an O-320 Fox, and sell N85AE! You got your ski's on up there Bruce?


Jeff, you better finish the one in the garage first!

[jtpitkin06]

I'm sure lot of you know that I am planning on putting a UL520i in my plane. My question is do you think that I should enlarge the rudder create a control horn at the top for it? Having never owned a Kitfox before I'm not sure if the larger rudder is needed or not.

The present size rudder on the model 7 is adequate for a more powerful engine. Probably up to 180 hp.

Look at the present rudder/vertical stab and ask if is big enough now with 100 or 115 hp on tap. The answer seems to be yes. No one claims a need for continuous full rudder on takeoff or in climb to hold things straight.

Let’s suppose you mount an engine with double the power. It doesn’t take twice the rudder deflection to maintain direction. Angular deflection of the rudder to counteract yawing from p-factor is not linear. Where it might take 5 degrees deflection for 100 hp it might take just 7 degrees with 200 hp. But that is only at the first application of power where you only have the prop blast flowing over the vertical and rudder. As soon as the airspeed picks up the flight controls become more effective.

I think the limiting issue on putting a larger, more powerful, engine on the Kitfox is propeller size. In order to absorb 150 or more hp the prop will need to be proportionately larger. Because the diameter is limited by ground clearance the prop must have a wider chord and ideally controllable pitch.

More power to you.

John

[airlina]

That one doesn't count, that's the secret airplane ... However after that I'll
build an O-320 Fox, and sell N85AE! You got your ski's on up there Bruce?

Jeff, skis are on and I have a couple of ski flights under my belt. It had been a few years since I have been on skis due to our mild winters. This winter is making it up with a vengeance as you know as well and lack of snow is not a concern. I forgot how much fun it is-like landing on a featherbed-half the time with new powder , you can't tell if you've touched down . Just remember no brakes! this is usually not a concern unless you are on ice or hard packed snow. Under normal conditions, it takes 1500 RPM to taxi so as soon as you throttle to idle, you stop. Up to 50 deg tomorrow- bummer sticky snow

[jmodguy]

okaaaaaayyyy...
I bought a KF V project recently and have been gnashing about an engine to put on this project. I have researched the various 912 options and the O-200/O-235 options and have read through numerous posts on TeamKitfox. I was seriously considering a Corvair as well. Even bought the Corvair manifesto... er manual. :D
I have an O-320 D1A sitting in my garage collecting dust. Guess where its going.... :eek: I will be adding taper fin cylinders, lightweight starter and a lightweight sump. That should shave about 10-12 lbs I am guesstimating. I'll be trimming weight wherever I can. I will be using a plenum from James aircraft to optimize cooling vice building baffles.
I realize this will impact the useful load. Thats fine by me. Don't care about sitting in the aircraft for a 4 hour stretch. Mans gotta pee.
The IO-240 is similar in weight and I have heard of some flying with the O-290 which is also similar in weight. I don't think the fuse needs any reinforcement or these "heavy" engines would be falling off the airframes and we would know about it.
Leaning towards a Catto prop too...

[Av8r3400]

It's not going to be the total weight that will cause you heartburn, but the location of that weight.

You are considering an engine that will go 275 pounds, at least, installed with baffling and exhaust, plus mods to the cowling to make it fit and cool.

All that weight will be at the extreme forward end of the envelope. This will require a massive amount of more dead balast weight in the tail to balance. Or a stretch modification to the tail.

There's an excel spreadsheet floating around the forum here to download which you can use to crunch some weight an balance figures.

Weather the airframe can handle that kind of torque and power is another, separate discussion.

[jmodguy]

AV8R,
I figured you would chime in! :D
Out of curiosity I went out to the garage and weighed the engine. It is disassembled so that made it easier!
I used a "highly accurate" wal-mart mega pound bathroom scale :rolleyes: and came up with 254 lbs total. This number was calculated using B&C lightweight alternator and starter, ECI tapered fin cylinders, and a Superior cold air sump and allows 2 lb for an oil cooler. Also accounted 10 lbs for coil packs and wires (for EI), 6 lbs for flywheel, 4 lbs for carb. That puts the O-320 pretty darn close to an IO-240. Conti claims a dry weight of 240 lbs per their website.
Yup I'll have to add exhaust and will have to account for the Sam James plenum but I don't think those will be that much off of a Conti IO-240 setup - probably less.
I am more convinced this will work.... Thanks for making me look!

Regards
Jeff

[Esser]

This may have some useful info in it for you: http://www.teamkitfox.com/Forums/showthread.php?t=6556&

[jmodguy]

Thanks Esser. Been watching you... Your build thread that is! When it comes time dont be afraid to build your own mount. Its not that hard!
I built an engine mount for my GP-4 and saved a TON of $$$. In Canada that would be $$$$ eh? :D
I used the site below and it made coping the tubing ends pretty easy. I was cutting out a tube every 30 minutes. You will have to build a jig but that is also not difficult.

http://metalgeek.com/static/cope.pcgi

[jrevens]

When it's all said & done you will be carrying the weight of an extra adult passenger in the airplane all the time. A hunk of it will have to be in the tail. Not to be too much of a naysayer, but it will probably change the wonderful light feel of the airplane, and make it basically a one person machine. More power is nice, you've got the engine, and you are a true experimenter... I admire that. I've got an O-320-D2A in my Thorp, and it's a great engine.

[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...:eek:
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. :D

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 :eek:

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! :cool:

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! :D

[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.

[n85ae]

I have a 74" prop on mine, I haven't had any problems ... Yes I do
occasionally wheel land it :)

[WWhunter]

I should add...this 75" WW STOL prop is not on my Kitfox (yet) but rather it is on my RANS S7. The plane has the stock landing gear but is on 29" AkBushwheels so prop clearance is not an issue.

[av8rps]

In my mention about running a long prop on an 0-320, I was thinking about the ultimate STOL prop for a Super Cub, and that is typically a Borer prop with an 82 inch diameter with 43 inches of pitch. That would make for one big bite of air on a Kitfox.

The general all purpose prop for a 150 hp Super Cub is a 74 inch diameter with 54 inches of pitch. Either the Borer or the standard prop will work well I'm sure, all depending on what you want your plane to do. You can find loads of info on the SuperCub.org forum if you want to know more about the best STOL prop for a 0-320 vs the more conventional props.

I'm guessing the 0-320 Kitfox will do just fine with the 74 inch pfop, but the Borer prop would really be a hoot in the back country with some big tires and an extended gear...hmmm? Maybe like the new Kitfox STI but with a big engine :)

[jmodguy]

Thanks for the input Av8r!

[jmodguy]

I was going through my paperwork couple days ago and I thought I would have to abandon the O-320 for this project. Some of the information that came with the aircraft indicated 1400lb GW spars (.058). I stopped at the airport on the way home and measured the wall thickness with my calipers and to my relief they are the 1550lb GW spars at .065!
So far so good...

[jheit39]

take a good look at the O340 from Titan..

[jmodguy]

Don't tell anyone but I am building an IO-340 with a FlyEFII kit... I have an EFII kit, a new ECI case and 340 stroker kit. :eek:
Pulling together the rest of the parts.
Reserved the N number 340KF last night
Remember - Don't tell a soul...

[redbowen]

Since I'm running a O-290D I thought I should chime in. I know all the Rotax guys love there set up, but there are others ways to go and they are great also. If you look at the engines that Kitfox supports it includes the O-235 that has a dry weight (246lbs) 1lb less than a O-290D while the O-290 adds 15hp. Thats basically a free 15hp.
As far as CG goes, its a non-issue. You go 1 degree wing sweep and the 3 leaf tail spring with a bigger tailwheel like a Matco 10" and no ballast is needed. This is how mine is set up and my empty weight is 930lbs CG @ 9.85 and with the wing sweep max forward allowed is 9.5. It is balanced nicely, plus I can lift the tail for take off from a stop. Climb out is 1000' plus, I can bump up against 140 mph wide open. I like to cruise at 2200RPM for a 118mph cruise and a 5.1gph fuel burn. It has the same LSA useful load as a carbon cub and has been the perfect airplane for my mission. I backcountry camp often with a group of guys and we almost always go 1 to an airplane with gear. Most of them fly Maules. They can carry tables and firewood, but they burn way more fuel and can't enjoy building and flying there creation.
I have looked at future overhaul options for the O-290 and the biggest downside to this set up is parts. One option I am considering in the future is to put O-320 cylinders on the O-290, and yes this can be done. Minimal weight increase and yet another 20hp. I think a O-320 or O-290 is a great option for the Kitfox and I can tell you they are still very sporty and a kickass airplane.:cool:

[airlina]

Bryan , What prop do use with your o-290? Thanks Bruce N199CL

[jmodguy]

Thanks Bryan that is very useful data.
Regards
Jeff

[redbowen]

Bruce,
I am currently using a Props Inc. Maple 72"x46. I have been talking with Catto about building a prop for the O-290 to improve STHOL even more, but I don't want to give up cruise performance. The Props Inc prop is a nice compromise giving me descent take off performance around 150-200 with just me on board and full fuel, and a cruise between 115-120mph.

[airlina]

Thanks Bryan, I have a Series 5 with an IO-240 swinging a fixed pitch wood Sensenich. I too have had a hankering to try a Catto , but don't want to spend the big bucks until I get some data from Phil (he is about ready to fly his airplane , also with an IO-240) Actually I have 2 fixed pitch wood Sensenich props, I use a climb prop when I ski fly and a cruise prop the rest of the time. I have heard great things about the Catto props- we will see what Phil can tell us. Bruce N199CL

[Av8r3400]

Bruce, what are the size and pitch of those props?

I'm about to embark with my 78x48" Prince...

[PapuaPilot]

Bruce, you are right I am about ready to fire up my engine. I just got the E-Mag installed yesterday and going to do the first runs this weekend. If everything checks out then I just need good weather for my first flight.

FYI the Catto prop I have is a 74 x 47.

[airlina]

Bruce, what are the size and pitch of those props?

I'm about to embark with my 78x48" Prince...

Hi Larry, First like to start off by saying what a fine job, you did on Mangy Fox- can't wait to hear about how she performs. My IO-240 powered Series 5 started out with a Sensenich W74ek-2-58. The -2 means from the factory, 2 inches were cut off of a 74 inch prop. So I started my flights with a 72" x 58 pitch wood prop. Max static RPM was low at 2200RPM and takeoff perf suffered , so after a talk with tech support at Sensenich, they suggested I take out my saw and cut more off the props. I had to sleep on that one, but I did cut 3/4" from each tip and now had a 70 1/2" dia prop left. This helped to jump the static RPM to around 2350 rpm and t.o. perf improved without hurting cruise perf by much. This is my all around prop now.
When I started ski flying, I wanted better get up and go out of the hole, as we get a bit of snow here in BUF. I purchased a Sensenich W74EK-54 wood prop, that I left totally stock at 74" dia. 54 pitch and it does the job. Static RPM on this one is 2400 and T.O. and climb perf is noticeably better than my cruise prop. Couple of reasons I am looking to switch to the Catto prop-1) want to be able to fly in rain and not worry about the prop leading edge eroding. 2) won't have to retorque prop every season change and 3) who knows maybe more all around performance can be had with one prop. Thats were Phil comes in, he is just finishing the same airplane/engine combo that I have except he went with the catto prop. Sounds like he is really close to a first flight-come on Phil we are rooting for you! Bruce N199CL

[n85ae]

I'm rooting for the Catto to work also, then Bruce will give me all his old
props when he switches, and I too can fly in the rain, but with dispo-a-prop
leftovers from Bruce.

Jeff

[jmodguy]

Looks like the 320/340 question has been answered by Kitfox. :D
Check out the "little more power thread" from Dave S

[grdev]

My project came with a FWF 582 minus the prop with a B gear box. I have been reading with interest the 670 package that is being offered by a gentleman in Florida. I do have a few questions though before I would seriously go to the additional expense. Will all of my parts, starter, carbs, exh system bolt right on, and will it all fit in my cowling with out modifications. Some have told me I would need to change my gearbox, and those are not exactly cheap. Any advise or experience doing this? Will it help my Model 4 1200 all that much?

[Av8r_Sed]

You'd probably get in the air quicker if you run what you've got. I have no direct experience but I'm sure the 582 exhaust from won't work on a 670. It also seems to be a challenge to fit the 670 exhaust in the cowling without some tweaks and trimming. If you get the 670, make sure it includes the exhaust.

[jmodguy]

This is why I am installing an IO-340 on my "5"... :D :eek:

https://www.youtube.com/watch?v=EauOoR4vFeQ

[redbowen]

Phil any updates on that Catto prop set up?

[PapuaPilot]

I still need to get my lift strut covers installed, so I don't have the data you are looking for yet.