Operation Cannibal Fox

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Posted (edited)

I'm guessing most of you are familiar with Trent Palmer and his kitfox, which he just installed a turbocharged 141 hp Rotax 915 in. He's dubbed it " cubkiller" since the goal was to outperform the carbon cubs at the Stol Drags at the High Sierra Flyin. Here's his video from the flyin: 

So "Operation Cannibal Fox" is to beat Trent Palmer and his "Cub Killer" in a Kitfox 1 at the Stol drags.

Right now it's mostly a mental exercise because i lack the funds to do it but i want your input on what it would take. Reason for this is even though "cubkiller" is supposed to be the poor man's way to compete with a 300k carbon cub 40k for a 915 doesn't feel very poor to me. 

 

Here are my thoughts and the mods i would make to do it. 

1. Cover in Oratex 600UL for the lightest weight covering possible. 

2. Carbon fiber vacuum infused cowl and anything else to shave weight 

3. Install BMW R100 turbocharged engine. 

4. As many streamlined struts and fairings as possible. 

 

The biggest one on the list is the BMW R100 turbocharged engine for obvious reasons. It seems to be a proven fact you can get 80 reliable NA horses out of a R100 and i was reading last night about how 100 turboed horses is pretty doable without major mods to the engine and if you want to go for 120 then you have to go with lighter pistons etc and you still might have a hand grenade. But let's just run the numbers on the 100 hp turbo since its the cheapest simplest alternative. 

My bird weighs in at 468 empty. Let's just say i shed the fat on the airframe and the engine and turbo bring it in at the same weight.  With just me and fuel for the race that's 732 lbs with 100 hp that's a power to weight ratio of 7.3. If I can shed the 35 lbs extra I'm packing even better but we'll plan like that's not going to happen.   

 

Freedom fox weighs in empty around 930lbs and I'm guessing Trent weighs in about 160 plus 40 lbs of fuel with 141 hp on tap yields a power to weight ratio of about 8.0 lbs/hp. So we've got him on power to weight barely, but he's got a Fadec controlled constant speed prop and mixture control which is probably a huge maybe insurmountable advantage. 

 

So what do you guys think? Is it doable? What would it take to beat him doing it as  cheap at possible?

Edited by Willja67

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Posted

You might want to get the Kitfox 4 wings also, they are a fair amount faster:)

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Posted

You might want to get the Kitfox 4 wings also, they are a fair amount faster:)

Yeah I was wondering about that undercambered airfoil.

So let's break it down so far:

Say 7-8k for the engine and prop (just guessing), $4500 for the covering materials (just got a quote last week) say 2k for all the carbon and vacuum bagging materials ( my labor is not counted). I'm putting aftermarket gear on so another grand there, and say another 4k just to round it off  for the mod 4 wings and other goodies with a base price $16,000 plane. So all told about 37k. So we come in less than what he spent on the engine. And it's still iffy. But fun to think about. 

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Posted

You might want to get the Kitfox 4 wings also, they are a fair amount faster:)

ya know just thinking the drag of the wings might not be a liability. Drag increases as speed increases but the distance between the 2 lines is only 3/4 of a mile so for maybe the first 1/3 of that you're not going fast enough for the drag difference to matter and the last 3rd of it you're trying to slow down to land in the shortest distance possible so now those draggy wings actually benefit you? Yeah sure Draco runs away from everyone at the start and can even slow down and stop pretty good with the reverse thrust but you'll notice the distance is greater and most guys made up some time on him by landing shorter and getting turned around in less space. 

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Posted (edited)

Okay, I’ll bite. I’ve seen the video, and imagined myself winning the competition, unlikely though it may be. My take on it is that you’re going to have to beat them with horsepower. Even with a better weight to power ratio, I don’t think 100 hp in a draggy plane will beat 140 in a sleeker one. Giving credit where it’s due, a sleeker plane with a capable and confident defending champion. So, is it even possible to beat Trent’s sweet Model 5, or whatever it is now, with a Model 1? And Draco, the Carbon Cubs, and everyone else? Maybe. I should be more positive. I mean, yes, I could do it for sure. Some VGs, better wheels, tires, and brakes, then replace the snowmachine engine with..... a better snowmachine engine! A couple years ago, Ski-Doo decided they had to make a mountain sled with a 2:1 weight to power ratio. They came up with a Summit 800 that weighed 400 pounds and had 200 horsepower. A good gear reduction, maybe some duct tape, to keep from ripping the wings off. There are plenty of those 800’s around. A little machine work to face up the redrive. I think I could do it for about double what I have into my plane, or half what Trent spent on his engine, however you want to look at it. And after I won, we’d all hang out, have some beers, and they’d let me fly their planes. Not necesarily in that order.

I do like the turbo Beemer idea. You should definitely do that.

Another thought, along the same lines. Instead of beating them at their own game, we should invite them to compete in the Talkeetna Stol competition. It’s different than the others, like Valdez, because you compete at full gross weight, instead of seeing how light you can be. That way, Trent could show up last minute, with his bags still in the plane, like at the stol drag, and it would just be like he was ready already. That would be good fun. Our low gross weight wouldn’t be a disadvantage, either. I’d like to see that. The straight 52 hp 503 Model 1 at 850 vs. Trent’s 141 horse 915 at 1,550 pounds. He’s still at an advantage there. Not sure where Draco weighs in. 1,000 horse and 10,000 gross? I better find one of those 200 horse Rotax 800’s. Now, if Trent or Mike throws down the gauntlet, you realize that we’re on the hook, right? See you there. 

Edited by Good old number 29

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Posted

I had one of those 800 Summits for just a short while, and it really was scary fast.  Maybe wouldn't have been in my younger days, but as you get older you start to realize that "Yes, you can kill yourself"  I will never race in the STOL Drags, but I think the key is rapid acceleration, and then just as rapid deceleration.  (stating the obvious I know)  A super light plane with tons of HP will give the first part.  Light plane with plenty of drag that has great brakes will give the second half.  The lighter the plane, the less float it will have when you want it to slow down.  Light plane will also stop sooner once you are on the ground and using the brakes.  I say figure a way to get that 800 hung on the front, and let her rip!  :-)  A 400 lb Kitfox 1 may be the ticket.  Probably not with Draco in the mix and his trick propeller though.   JImChuk

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Posted

Well you got me looking at the etec engines and wondering what it would take to hang one on the front of a kitfox. Given Rotax's exit from the 2 stroke aircraft engine market it would surprise me if they didn't make bolting a redrive onto the pto side of their current engines a difficult chore, just to keep us guys from committing aviation with their engines. Obviously there's the issue of fitting all the tuned parts ie intake manifold,  exhaust etc under the cowl and dealing with the computer issues ie limp modes etc. I haven't heard of anyone even trying to do this so I'm guessing the above is a pretty daunting task?

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One thing to really think about is the kitfox 1 mixer system? I for one would never exceed 100mph with that setup.  I cruise mine at 85 to 90 all the time but when you reach your arm back there and hold on to the mixer system you can always feel a continuous vibration through the system and the faster you go the more you think about it.

Jim and Paul have the best ideas with the light weight engine and better wings. But that's a lot of work and money to modify somebody else's design you would be cheaper to design your own airplane and build it. 

For my next airplane that's my plan at least. :BC:

 

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I think a cheaper way to get 200+ HP is to look at those turbocharged Yamahas, I saw a fuel injected, turbocharged low mileage sled for sale on craig's list for 3500, plus one of those boxes that are now being tested, (see the thread and FB page by Teal Jenkins) and you could get big horses (200+) for much less that $10K. Here is the FB page: https://www.facebook.com/groups/164864990778457/,  and here is the AFF thread: http://www.avidfoxflyers.com/index.php?/topic/5824-yamaha-apex-skytrax-adapters/&page=3#comment-58241

As far as reliability, these 4 strokes are built by the 200,000's per year. And their part pricing is 10% of the Rotax gouge.

 

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Posted

A kitfox model 1 with 150-200 horsepower!!!! Good grief, Charlie Brown. I think they call that an engine with wings and a seat.

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Posted

This thread is about beating a 915 equipped kitfox with a model 1 which is I think in the realm of possibility though maybe not probability. 

If you want to talk about beating Draco then perhaps start another thread called "Dragon Slayer". 

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I was doing some digging on utube of the STOL drags to try to see what is the top speed these guys get up to before they start to slow down.  Anybody know?  JImChuk

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A model 1 beating a 5 with a 912 is possible and very likely with just a 582, at least as far as takeoff and landing. Top speed, well a model 1 is the wrong airframe. And for the STOL competition aircraft, top speed isn't great.  Very few STOL aircraft, if any, will make much over 100, maybe 115. But I find it ironic just what some call STOL aircraft or STOL fields. To this hillbilly, a 1000' strip is NOT a STOL strip. 500' or less is what I call short.  If it has a big "H" in the middle then its a short field.

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Posted (edited)

Agreed. I think the term stol should only apply to double digit deeds. 

I’ve been wondering what their top speed is, too, in the stol drags. I’ll probably waste some time trying to figure it out. We know it’s 3/4 mile, so it wouldn’t be impossible to figure out by timing them. The newer foxes, including the 5 and the STi, have a 140 mph vne, so there’s that. I might have enough duct tape to raise mine above its current lower limit, but not that high, without some real mods. I think that winning with it would hinge on short stops, a quick turnaround, and acceleration that hurts. Reverse thrust would be awesome, but doesn’t seem to be in the realm of an average Kitfox budget. You’d need some real engineering and machine skills to put that together. 

Say you only do 100, but you accelerate to top speed in two seconds. Maybe that’s optimistic, but you get the idea. Then, turn it around like a rubber band, and stop like a hockey player at the finish line. A new Porshe 911 turbo does 0-100-0 in 13.5 seconds, and 1,150 feet. That’s just touching 100, and slowing back down. Say, for instance, the plane accelerates and brakes exactly as fast as the Porshe. Once you reached 100, you’d need another 19.2 seconds to cover the extra 2,810 feet, so a total of 32.7 seconds, each way, plus turnaround. Yes, I know the plane won’t decelerate in the air as fast as the Porshe does on hot asphault. Maybe a dragster style parachute, or aircaft carrier-like hooks? Huge brakes, for sure. 

Edited by Good old number 29

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As far as high speeds in a Kifox 1, I think one of the limiting factors is the thin windshield starts to buckle in at 100 MPH.  They use the same mixer controls as the Kitfox 2 and 3 which have higher VNEs, so I wonder what other limiting factors they really have. Diagonal bracing in the wings got stronger as later models came along, and maybe that is the determining factor but I don't know if the 2 or 3 are stronger in that area then the Kifox 1.  TJay, I wonder about the vibration in your mixer controls, I've never grabbed onto mine to see if there is a vibration in them, but don't think there should be much if any in the controls.  First thing I wondered about is flaperon counterweights, but I remember you made yours.  JImChuk

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I found just one race online, that showed the whole thing with their finish time. It was 1:33: That was the 2017 competition. I don’t know how they placed, but there can’t be too much spread. I think it’s doable at 100 on the top end. 

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To get the most horsepower per pound I'm thinking electric is the way to go if all you want to do is win this style of race. You won't have the range of an internal combustion engine but it's hard to argue against electric in this application. It would have the ability to instantly reverse thrust giving you the same advantage as Draco in that department.

 

Have you seen this aviation speed record attempt: https://newatlas.com/rolls-royce-electric-airplane-fastest/57849/

The motorcycle world has already been turned upside down with the advances in electrics such as this: http://lightningmotorcycle.com/

And how about this electric China has in the works for cars: https://www.forbes.com/sites/neilwinton/2016/11/21/chinas-nextev-launches-nio-brand-and-worlds-fastest-electric-car/#5bc859042969

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Here ya go.

348 hp and 110 lb, batteries not included.

https://newatlas.com/siemens-world-record-electric-motor-aircraft/37048/

That's a little over kill don't you think? It would be fun though. I was thinking a slightly smaller engine and just enough battery to win the race. Maybe one of the motorcycle engines is more adaptable to our sized airplanes. Anyone else follow the races on The Isle of Man? We started out strong the first couple of years with U.S. entries making it to the top of the field but we have since failed to make the leader  board. Link here: http://lightningmotorcycle.com/

That's a much longer motorcycle race than the one were talking about for this airplane event so less batteries would be required.

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Posted

Well that electric motorcycle looks pretty cool. If you can find a 4:1 psru and if the fuselage of the model 1 is strong enough that all that power doesn't twist the front end right off the plane that might be a pretty fun ride.

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Posted (edited)

How about 240 hp?

Edited by Willja67

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That could be fun. There's a part of me that likes the turbo better in the air than on the snow. I think it's a better application, because of the constant rpms. Those e-tecs are heavy, though. Comparing outboards, they're closer to the weight of a four stroke than to a regular two stroke. Factor in the 200-300 horsepower with the turbo, and it's worth it, though. I'd want that in a Model 4. I didn't pay attention to how the bearing is lubricated. Kind of wonder about that. A direct injected turbo two stroke. We better put that to good use before someone outlaws it. 

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Well that electric motorcycle looks pretty cool. If you can find a 4:1 psru and if the fuselage of the model 1 is strong enough that all that power doesn't twist the front end right off the plane that might be a pretty fun ride.

Here's a link to a home brew electric in a R1 Yamaha cycle. I still like the idea of almost instant thrust reversal without the complicated propeller. I have a race nut friend who loves horsepower but hates the idea of an engine with no noise. A quiet motor sounds like an advantage to me.

Link: https://www.youtube.com/watch?v=vdKDOfXBRMM

 

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That would take a little bit to get use to it but I would imagine the propeller would make enough noise to make it feel like your moving forward.

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