109jb

The logo when pointing upward has the letters TRAVEL AIR in it.  The wheel pant is the AIR.

I think he meant used in a movie. I remeber it but can't think of the name.  Comedy cop movie with Will Farrell and Mark Wahlberg I think. Lots of good one-liners in that movie. If only I could remember the name.

Thought the OP might like to read an old Sport Aviation article about Jim Younkin's Piper Pacer. He took a 160 hp Pacer, which from Piper is about a 130 mph airplane and with aerodynamic cleanup got 155 mph out of it using the same engine.  The stock pacer was probably cleaner than the average Kitfox in terms of what could be improved since it would have already had some fairings on things that aren't normally faired on Kitfoxes. I'm hoping the article might give some ideas. I have always admired this airplane and saw it a few times at Airventure. Anyway, here is the article.

1989_03_02.pdf

Yeah, I was just looking at "powersports" batteries and the Odyssey batteries are only a few dollars more than the other name brand batteries. The no-name batteries are cheaper but I tend to stay away from them anyway. A recommendation from someone like you who operates where it is REALLY cold is more than enough to justify a few extra dollars for the Odyssey. Now I just have to measure the current battery to make sure I get the right size.  Thanks for the insight.

After doing some more research it seems that LiFePO4 batteries aren't that great in cold weather anyway so I'm going to stick with a SLA or AGM battery for my main battery. I think I will buy a LiFePO4 jump start battery pack though.

The cold weather only factors in because the current battery is an unknown age (came with the plane when i bought it), and it is showing that it is weak. If I want to fly this winter I'm going to have to replace it with something. Could be a new SLA or AGM, but I figured if I need a new battery now I may as well think about the LiFePO4 batteries.

With the cold weather coming in fast I'm thinking about switching from the SLA battery my Kitfox came with to a LiFePO4 battery. I have never used a LiFePO4 battery, but reading up on them it appears that ideally they should have 14.0 to 15.0v charging input. My Kitfox has a 582 paired with a Key West voltage regulator/rectifier. The specs on the regulator/rectifier say that it regulates to 13.8v. So this I guess means that the LiFePO4 would not get fully charged. I am interested if anyone running a 582 has tried a LiFePO4 battery and what your experience is.  Namely will it work with a 13.8v regulator?

Thanks

Mine vents to a fitting on the right wing tank. 

I just wonder if the price increases on Avids and Kitfoxes will be a short lived phenomena. I seems that the recent increases must have been spurred on by the Trent Palmer and similar video popularity. I just wonder if it will continue to drive prices or if the fad will die off.  I certainly think that all of those brand new Kitfox kits being sold, a large number of them will probably show up as unfinished kits in a few years.

Simply said, you said that Drag is not proportional to Vsquared

And that is a true statement, total drag is not proportional to V². One more time. Parasite drag, which is only a portion of the total drag is proportional to V². Induced drag is proportional to 1/V². The sum IS NOT PROPORTIONAL TO V²

  and implied that it is not that big.

And where did I imply this?   I said "So at lower speeds induced drag dominates and at higher speeds parasite drag dominates.", which is an absolutely true statement. If you chose to interpret this otherwise then it isn't a matter of me implying it, it is a matter of you assuming it..

It is, in fact it is bigger than Vsquared. Can you at least admit that? Like thi 

Oh for Pete's sake!!!!  I NEVER SAID THAT TOTAL DRAG WASN'T LARGER THAN PARASITIC.

Fine, I will go ahead and state what is blatantly clear in all of my posts, graphs, and equations but for some reason you chose to totally ignore.

Total drag is greater than parasitic drag alone.

Now will you either provide a quote where I said otherwise, or admit that I never said that?

Your discussion is helpful, your math, not so much.

Huh?  Bold statement for not showing one bit of evidence that my math is wrong, which it is not. 

Total drag = Parasite + Induced drag. That means the Vsquared Parasite drag is ADDED to the Incuded drag to make total drag, so Total drag goes up by MORE that Vsquared.

Yeah.  Show me where anything I said is contrary to Total drag = parasite + induced. 

Also, let me correct your statement as it is slightly incorrect. here is what it should say 

Total drag = Parasite + Induced drag. That means the Vsquared Parasite drag is ADDED to the (1/Vsquared) Incuded drag to make total drag which makes TOTAL DRAG NOT PROPORTIONAL TO V²  

Somehow you think Induced drag is subtracted from parasite drag in the process, where this came from, I don't know. The fact that Total Drag line on the plots you provide is ABOVE Parasite drag is lost you you

So show me where I said that induced drag is subtracted from parasite drag.  I'll give you a little hint....I didn't and claiming that I did is just poppycock.

You are flatly wrong in your understanding and clearly don't understand that once you perform a drag cleanup on an airplane you aren't just moving up the original drag curve.  You have created a whole new drag curve and have to  first move to that new drag curve to find the new equilibrium where Thrust=drag.  At the new equilibrium the drag makeup is such that the induced drag is lower than before. The parasitic drag coefficient is also lower which is why the parasitic drag curve, and consequently the total drag curve have shifted downward, but the total parasitic drag at the new equilibrium is higher because the airplane is operating at a higher velocity.

If you start out closer to the "bucket" of the total drag curve the resultant Induced drag decrease can be larger because the induced drag has a stronger presence the farther left you go.  

The Minimum total drag at the bottom of the "bucket" is the point of best efficiency and longest range, but is a little problematic because if you slow from here, drag increases and you slow more and more, so most airplanes use a speed slightly right of this point for the best efficiency cruise because it is stable. If you slow, the drag decreases and you sped up, likewise if you speed up drag increases and it slows. This yields a stable equilibrium.  So if we start just right of the minimum, we see that a reduction in parasite drag can result in a larger decrease in induced drag.

Oh for Pete's sake, save us the internet version of anti-vaccination, ok, 109jb. Or else write NASA and tell them your crackpot theory. Until then, drag goes up by V squared, and in fact power required goes up by V cubed. 

Hurl all of the insults you want. Call me a crackpot or whatever makes you feel good about yourself. 

I will say it again, Total drag is not directly proportional to V². No ifs ands or butts.

It is true that Drag = 0.5*rho*V²*S*C_D, but that ain't the end of the story.

C_D = C_Dparasite + C_Dinduced.  The C_Dinduced term has a C_L in it. Namely, C_Dinduced = C_L²/(pi*AR*e). So substituting C_L = 2*L/(rho*V²*S) into the drag equation creates 2 terms 

Drag = 0.5*rho*V²*C_Dparasite + 0.5*rho*V²*S*(4*L²)/((pi*AR*e)*(rho*V²*S)²)

reducing, Drag = 0.5*rho*V²*C_Dparasite + 4*L² /((pi*AR*e)*(rho*V²*S))

which give a parasite drag term that is proportional to V², and an induced drag term that is inversely proportional to V²

From the equation above, if lift remains constant, which it has to for level flight, then an increase in V results in a decrease in the induced drag term.

Logically, a reduction in parasite drag would result in an increase in speed. If nothing is done the airplane would climb since L=0.5*rho*V²*S*C_L and V has increased. So in order not to climb, a reduction in AOA with a corresponding change in C_L happens. Reducing C_L reduces C_Dinduced which is the same as reducing the induced drag.

Graphically, This reduction in parasite drag looks like the attached graph and a parasite drag reduction WILL result in a decrease in induced drag. 

This is wrong. Total drag is not proportional to V^2.  The portion of drag proportional to V^2 is the parasite drag. Induced drag is inversely proportional to V^2. So at lower speeds induced drag dominates and at higher speeds parasite drag dominates. Think of it this way, reducing parasite drag gets a bump in speed, and the bump in speed gets a reduction in induced drag. So, when you reduce parasite drag you also get an induced drag reduction as a bonus. If you are in a region where induced drag is dominant then the induced drag reduction could be very large for a modest parasite drag reduction.

Those snowmobile primers use a rubber check valve and they can and do fail. It is basically a flexible flapper valve. Older ones are susceptible to ethanol and other additives in modern car gas. I had one on an old Ski-doo 2-up that had turned to a ball of goo and would not prime anything and I suspect that before I got it the previous  owner used ethanol containing gas. I would think newer versions may have different rubber compounds formulated to stand up to the ethanol.  

An aircraft primer has spring and ball check valves and are designed with enough spring tension to not be able to siphon through or to gravity feed through. It also has a pin that locks the check valves in the closed position. If they did leak every Cessna or other high wing airplane out there would be flooded every time you tried to start.

Also from your description, the primer supply is not filtered at all except maybe by the coarse finger strainer in the tank. The primer should come off of the outlet side of the gascolator if there is not a port on top for the primer. This would be downstream of the shutoff valve. If there is a top port on the gascolator this is also filtered  fuel, at least filtered by the gascolator screen.

I know that lots of people use the snowmobile type primers pictured, but personally I would not. An aircraft  primer is about $190 brand new and that I'm willing to pay for peace of mind. Fortunately I don't have to because the builder of my airplane already put an aircraft style primer on it.

No. That is excellent information. I just found out I might have an opportunity to get a 912 for a really good deal so I'm going to see if that pans out, but if not I think I will get the clutch for the 582.

That all sounds good. For those that run them how is the reliability of the RK400 on a stock 582? Sounds like on more powerful engines they may be iffy. 

So I have been thinking about getting a RK400 clutch for my 582 for a while now and have been on the fence. I'm wanting to hear from those that have flown both with and without a clutch. I've read all I can find and see the following pros and cons to using a clutch

Pros

• Easier starting
• Smoother idling
• Probably less stress on the gears, crank, rods, etc.
• Warm up without prop spinning
• Less float on landing
• Steeper approach (could be a con too depending)
• Great for float flying (I'd guess for ski flying too)

Cons

• Reduced glide performance
• Extra maintenance item
• Can't rotate engine with the prop (ie: for maintenance)
• About 4 extra pounds weight up front from what I have read

Questions:

• How often do the clutch linings need to be replaced.
• Would you describe the glide penalty as "worth it" for the other benefits?
• If you have experience with the clutch would you go back to operating without one?

Right now my engine idles rough below about 2500 rpm when warm and even a bit higher when cold. I am a snowmobiler and am used to starting the sleds and letting them warm up good and listening to sewing machine smooth idle as the sit there warming up. I see some benefit to having really smooth idle without the prop turning during warm up especially during the cold months. Now that it is getting colder outside I'm leaning more and more toward getting a clutch for some of these reasons. What do you experienced clutch users say? 

Mongo need pictures

Yep.  I've used zip ties the same way, just prefer the tool because I can use it to push or pull a spring off. Hard to push a shoelace

EDIT:

This is the spring tool I use on my snowmobiles.

https://www.countrycat.com/arctic-cat-6639-904-16-inch-exhaust-spring-hook-tool?utm_source=google&utm_medium=cpc&utm_campaign=google-simple&gclid=Cj0KCQiAq97uBRCwARIsADTziybh7uFn3mMY9ePtmXJ7EAyfcbJy6XqLY5-Wl1h98B_CD9Gvrpx4x7kaApn2EALw_wcB

Its too long for carrying in the under seat storage but I'll buy a similar shorter one for taking in the airplane.

Thought of something else us 2-stroke guys need.

---Exhaust spring tool

So I'm putting together a list of tools and supplies for my 582 powered Kitfox primarily for when I go on short trips and such, but also to keep in the plane. Right now the plane is at a hangar where I can't really leave a set of tools out there to work on it. I want a set that I can do most of whatever I need so I don't have to lug a bunch of tools from my truck. I have an under-seat storage compartment and I think everything except the oil will fit in the compartment.

1.  6-way screwdriver

2.  6" adjustable wrench

3.  Combination wrenches 5/16" - 9/16" &  8 - 14 mm

4.  Spark plug tool (socket and rachet or t-handle, etc)

5. 1/4" drive ratchet and socket set (minimal sockets)

6.  Small safety wire pliers & some safety wire

7.  Cable ties

8. Some allen wrenches

9. tire pressure gauge

10. Electrical tape & Gorilla tape

11. Extra set or 2 of spark plugs

12.  Never-seize 

13. Extra 2-stroke oil

14. Fuel tester

Please let me know if there is something you consider essential that I have not listed.

More thinking on my part.

What are the airfoil differences between the various models?

I'm not sure i would even grind all of the tubing away. I would try cutting either side of the bracket and then put a 0.058 wall tube that fits inside and then splice into the new longerons with some rosette welds and a perimeter weld.

Rotax has a Service Instruction regarding carb icing on 2-stroke engines that includes a couple proposed methods for carb heat

https://rotax-docs.secure.force.com/DocumentsSearch/sfc/servlet.shepherd/version/download/068A00000018rqtIAA?asPdf=false

Also, there are at least a couple vendors that sell "carburetor heaters". One style uses hot water from the cooling system to heat the carb bodies. Obviously this would only work on water cooled engines. The other style uses electric heating elements to do the same and runs off of the electrical system. This method doesn't heat the induction air, so there isn't a large horsepower loss or change in mixture due to heated air.

That said, I agree that the typical rotax 2-strokes are not as prone to carb ice but it isn't because of the engine, it is because of the type of carb used. My 582 powered Kitfox doesn't have any carb heat and I'm not worried enough to add one.