Author Topic: ERATIX .25 3D R/C ELECTRIC STUNT??? (Read 4439 times)

Walter Hicks · « **on:** February 09, 2009, 09:33:29 PM »

Hi Everyone,

I have had an E- Flite Eratix .25 3D for some time now. I will probably convert one to gas and possibly down the

line one for Electric.

It weighs 30 Oz assembled without any motor etc. This is amazing considering it is 795 sq in !

I am going to use a Discovery Retro .61 for the gas.

My question is this : For Electric

1. For 3D it says to use an E Flite 32 with 60 amp ESC and 14.8 V 4200 battery.

Would this possibly be a good starting point for CL ??

I have roughly figured it will weigh in at 56- 60 oz depending on which battery is used.

I already have an E Flite 46 but it is considerably heavier.

I would like to use Turnigy products as they are very reasonable what would be a good starting point for

Electric Motor??? Any comments would be appreciated

Rudy Taube · « **Reply #1 on:** February 10, 2009, 12:30:30 AM »

Hi Walter,

I think you are on the right track! I keep looking at some of my smaller ERC planes and think of a conversion to CLPA. But all the wings are too thin for our CL needs. The plane you have selected has everything we need for CLPA, thick airfoil, big wing, light, and it looks good! The only airplane mod I would make is to epoxy some thin CF rods between the stab/RD/Stab/Fues/Stab to keep the lightweight tail in place during squares.

RE: your motor selection:

1. for this size (weight 50 to 60 oz) E-CLPA Our standard AXI 2826/10 4S 4,200 mAh, 45 ESC setup weighs approx. 23 oz. Your E-Flite 46 only weighs about 3 oz. more, but has plenty of power to carry a few extra oz. and you have plenty of lift for the weight too!

2. This + your 30 oz. plane should be a very good flyer at 56 -58 oz.

3. Your E-Flite 46 should be perfect for this plane. It is a very good motor and has HD bearings (thus the 3 extra oz.). Remember we need more power than ERC due to the drag of the lines, etc. I would stick with the 60 ESC if possible.

You will have a lot of drag with that big wing and thick airfoil, but your motor should have enough power.

4. RE: TURNIGY products. As I have said in other posts, I have many ERC friends that use these products and have very good success with them. They run strong, run cool, are light, and very inexpensive per watt of power. I would go with one that they list as the equivalent of a .50 glow. If you use the correct size motor, you won't stress them too much in our CL use and they should last OK. If you plan to fly 800 to 900 flights per year like the top pilots do, then I might worry about reliability, but for most of us, it may not be an issue?

5. Since you already have the E-Flite 46 you are set! The extra few oz. should not be a problem. With your large airfoil and wing area you may even have to add some lead to keep it from floating around in the wind!

6. If you are just experimenting with ECL and not sure if you want to stay with it, then any charger, battery brand will be fine. If you expect to fly over 400 ECL flights per year then you may want to go with the suggestions I listed in the last issue of SN (E-Stunt column).

7. You should be able to use the motor box that comes with the plane. If the wing is a "plug in" on a CF tube then you can mount the BC just off center and install adjustable LOs and be all set.

Good luck with your project and please keep us updated.

Regards,

Walter Hicks · « **Reply #2 on:** February 10, 2009, 12:27:31 PM »

Thanks for the reply.

I am attempting to do the math as has been suggested in other posts. E Flite 46 shows 670 Kv

670Kvx14.8 volts = 9916 RPM

700 Watts power available .

As Rudy stated this looks to be more than enough power for 60 oz plane.

Dean Pappas · « **Reply #3 on:** February 10, 2009, 04:06:11 PM »

Hello Walter,
The power 32 is certainly large enough for the job. The sweet-spot for 4-cell applications is a Kv of right about 900 RPM/Volt. With the Kv of 770 RPM/Volt, and using the rule of thumb that you would like to run at 70% of battery voltage on the governor, you may find yourself running a 7" pitch prop or that you will be running closer to 80% with a 6" pitch. No problem either way ...
Go for it!
Dean P.

Alan Hahn · « **Reply #4 on:** February 10, 2009, 05:50:46 PM »

I'm guessing one hunk of a prop for this bird!

It's fun to play with this stuff!

bob branch · « **Reply #5 on:** February 10, 2009, 08:13:46 PM »

I have flown the eratix extensively as a 3D rc plane and the power system you list is so way overkill you cannot even believe it. It does everything the plane can do.. which is everything, on half throttle with an axi 2826/10 right out of my electric smoothie and 4 cells 4000 mah 10C polyquest lipos. I have flown it with axi 2826/12 as well. Both ways are nice, just a little different. It is a delightful 3D electric airplane. The airfoil is very fat and the ailerons will flutter right out of the airplane at 50 plus mph we fly at. It is a 30 mph airplane with the stock control surfaces.

As far as a 60 or any glo motor, I would think 15 or 20 times about it. Twice sure isn't enough. The fuse aft of the wing is the achiles heel of this design. It is soft, weak, and just barely acceptable for 3D. It is a less than one season 3D electric when flown even moderately hard. Without ever a crash, it just kept coming apart in the air. Oh it will go 2 seasons of rc if flown infrequently, but not weekly. I considered using it as an electric stunter, but the flutter issue, and I was not using weak servos that could not hold the surfaces but several sizes larger than normal electric fare, and the weak fuse detered me. Also the covering is absolutely unrepairable. Aweful stuff. I do have to say it was one outstanding flier as a 3D electric. So good I'd really like to have another to fly, but I am just not willing to put up with eFlites extremely poor construction. There are very well constructed 3D planes out there that weigh the same as the eratix and are solid strenth wise. Extreme Flight, Sebart, Precision Aerobatics, and others all are in the upper echelons of arf craftsmanship... its beyond workmanship.... and the planes fly exceptionally well as well.

As you can tell, it was a love - hate relationship. But a fat wing does not a good conversion make. I fly RC electric and convert many to glow power. Sorry for the electric purists in the crowd. I happen to like glo better than electric... . When you convert electric to glo you need to use decently built aircraft. Those I have mentioned convert very well. Their construction methods make CL look prehisotric. Hopefully, when CL arf's get thru enough growth to bring in more companies we will get the kind of high quality laser cut intricate fuselage structures we see in 3D electric that makes them so light and rigid. What we have found is that in 3D you no longer have to have really fat wings. Eratix wing is thicker than Strega's as are many .40 size 3D profile wings. But we are now finding thinner wings fly just as well in 3D mode and let us also fly in precision mode with the flick of a switch to lower rates. Its a big mental jump in the middle of a flight, but an interesting diversion.

bob branch

Rudy Taube · « **Reply #6 on:** February 11, 2009, 01:11:39 AM »

Hi Walter,

A few more comments.

1. RE: YOUR PLANE.

I am not familiar with your planes manufacturer, I was only going by your photo and comments. I assumed that you inspected the construction and found it adequate for our CLPA needs? Bob has some good points re: the rear sections of some Slow flight 3D RC planes (thus my nod toward at least stiffening up the tail section). The RC planes I fly the most are from ExtremeFlight. Like Bob says, they are the best. They are strong, light, and perfectly built. They are as well built, and as beautiful as the best CLPA planes I have seen (and yes, I have personally seen the world champs beautiful plane, and several Nat's champs beautiful CL planes, ;-). My big Yak 54 is a true work of art, and my brand new Extra 330LX is almost too pretty to fly, 1st flight tomorrow AM.

Just to clarify Bobs comments on airfoils. We have flown our RC planes in a 3D mode for decades with normal RC size airfoils, more so in our larger 35%+ size, but also in our smaller ERC planes too. It is the "Fun Fly" 3D mode that went to the very thick (CLPA like) airfoils. This allows almost anyone to be able to fly very slowly (as inside a small park, etc.) and almost not worry about stalling. I still love flying my perfectly built (ARF) Electric Shock THICK wing park flyer at our local park. But like Bob pointed out, these are meant to be flown SLOOWLY, usually well <40.

As beautiful as our ERC planes are, we need to be careful when we try to convert them. As I stated before, I think you should go for it if you just want a good looking sport flying CL plane. I don't think any direct conversions will make it as a compition CLPA plane.

With that said, there are some excellent ERC fuselages that would make a PERFECT CLPA plane when used with a real CLPA wing.

http://www.hobby-lobby.com/g2e-extra300.htm

http://www.electrifly.com/parkflyers/gpma1572.html

http://www.electrifly.com/parkflyers/gpma1572.html

http://www.electrifly.com/parkflyers/gpma1573.html

As you can see, I have looked into this! ;-) All of the above fuselages are our length (46" to 47"). Most have full top hatches for easy battery access, beautiful cowls, strong LG, great looking scale canopies, good RD. All they need is a CLPA wing, and larger Horizontal. Tail volume.

The price for the needed parts comes close to the full plane price. After adding the wing, etc to make it a E-CLPA plane it is a lot of work, but it sure would be nice! :-)

The RC airfoils are almost all too thin (except the Slow FunFly models like yours) to work at our slow speeds and sq. corners, so I would not try to go there.

2. POWER

First, I like lots of power. I watched CLPA for a year as a judge before I started flying CL again, so I could find out what works best. IMHO: After all is said in done, POWER LOADING is by far the most important thing in CLPA flying (maybe tied with reliability?;-). The one thing that ALL the winers had in common was POWER. The best were the perfectly set up tuned pipe systems by those experts that slept with their engines under their pillows and kissed them good night, "every night" and the four strokes that ran like a swiss watch and pulled like a freight train (watch Egor P sometime!!!). These pilots did not have to "dance" around in the center of the circle to keep line tension overhead in the wind and turbulence, they just stood in the center and FLEW very nice patterns, with POWER to spare! This is NOT flying with an old Fox .35 in a 52 oz (TOW) plane that could barely keep it up like in days of old. Allthough I do admire the guys that can "do the dance" and still fly these grossly underpowered, thin airfoil, planes. :-)

WATTS PER POUND?

I think my E-CLPA idol, "The Dean", gave us some watts/lb. rules of thumb on a past post. I think they are similar to mine? In ERC we use 150 as a min. for 3D work. At about 190 you can comfortably hold your plane vertically and let it go out of your grip and have it fly away safely. I have planes at around 250 that will leap out of your hand vertically and do vertical rolls until they are a dot in the sky. :-)

This tells me that with our thicker airfoils and very high induced drag in our angle maneovers, and with our line drag, that we would want to have around 150+. The "standard" AXI 2826-10 4S setup is around 160 watts/lb (on my 58 oz TOW plane). This flys great, but a little more power would not hurt (after all, we are red blooded American males, right!

)

Your E-flite 46 is around 900 watts (per spec sheet). For your 58 oz plane this is around 250 Watts/lb. Like dean said, the E-Flite 32, or the AXI 2826 (600 watts = 166 Watts/lb.) is more than enough power. Or one of the Turnigy 600 to 700 Watt motors. Your 46 is still OK, but it does have extra power to burn.

Again, for sport use you will have fun. For serious CLPA, you may have to look elsewhere.

Good luck, and please keep us posted with your results. :-)

Regards,

Walter Hicks · « **Reply #7 on:** February 11, 2009, 03:03:52 PM »

Rudy,

I also Have a Hyperion Yak 54 that I have had for some time. Much thinner airfoil , well built only 600 sq in though.

.Not as light but well constructed.

Walter Hicks · « **Reply #8 on:** February 11, 2009, 03:11:16 PM »

Another picture of the Yak 54 thin wing??

Crist Rigotti · « **Reply #9 on:** February 11, 2009, 08:24:23 PM »

I would think that anything over 16% would be good enough, and that includes the flaps. Anybody know what a Nobler is? What 14% including the flaps?

Darkstar1 · « **Reply #10 on:** September 14, 2009, 06:21:24 PM »

Hi All,
Walter has sent me the Eratix & I have already done the conversion to C\L
as far as a e-stunt setup goes I've decided 2 use the following
Motor: Turingy SK 35-48-900
Esc:Phx-45
Batt:Rhino 4000mah 4S2P 25c
Timer:JMP-2
Now when I have enough pennies saved up I can start buying stuff

just one big detail. If any one does this conversion one must put a wedge
on the nose (about 3/16in) to offset the outboard thrust built in th same 4
the nose cowl. I can xsplain in detail if any one wants. Thanks Walter!

Later,
Darrell Harvin
Pasadena (The one in Texas!)

bob branch · « **Reply #11 on:** September 14, 2009, 06:55:46 PM »

Earlier in the summer I did a thin wing 3D rc conversion experiment just to see how it worked out. A nobler is an 18% airfoil including flaps. I converted a Hyperion 40 size Extra 3D electric RC plane to control line stunter. Power was an axi 2826/12 with Hublin timer and Castle Creations phoenix 45 esc. Battery was Turnigy Flightmax 3000 mah 4 cell. Prop apc 12X6P electric. Wing area was 575 squares. The purpose of the experiment was two fold. First to see if a modern thin wing 3D plane could be flown at CL speeds without flutter and stall issues and second if the power system was up to the task of pulling around one of these big wide fuselage planes.

Power system wise it was a no brainer. Tons of power. 8400 rpm on regular apc 12X6E and 8700 rpm on the pusher yielded 5.3 sec laps on 63 ft eye to eye lines. The wing was another issue. The plane is a wonderful 3D rc flier. Stalls are not a problem at all. Does everything you would want a modern 3D plane to do with the 2826/12 and 4S configuration. The wing was 11.3 % airfoil. So pretty thin but that was the point. And it did not work. We encountered stalls in corners with it. Oh, it did have a corner, no question there. And it did fly nice maneuvers, but as Frank Carlisle, Rick Sawicki, and myself evaluated it carefully it did not merit further development due to the wing stall issue. Esthetically it was beautiful to watch fly. The big fuse was quite nice to see. Landings were breathtaking on its tall 3D gear designed to handle 15 inch props in electric 3D. But the wing was going to be the limiting factor. The flaps btw, were built up to match the airfoil, not flat stick shapes like the Eratix. They were quite rigid and not suprisingly we encounted no flutter issues at cl stunt speeds. The plane will be converted to RC 3D electic configuration during the winter.

Hope this helps some.

bob branch

Igor Burger · « **Reply #12 on:** September 15, 2009, 01:19:10 AM »

That wing is just wrong:

1/ too sharp LE and too thinn airfoil will need low wingload for usefull flying and it will make troubles in turbulence. We need wing loading as high as the good arfoil allows it. Means we need blunt and thick airfoils.

2/ that wing has 3D ailerons. not flaps. Flaps shoul be concentrated at root, not at tips of wings. It is because flaps on tips can cause stalls at tips and thus troubles. Ratio flap chord to wing chord shold be bigger at root and smaller at tip. - thisis just opposite

3/ our flaps should be flat, not intedgrated to the airfoil, because they shoul have the best efficiency (good L/D ratio) deflected, while L/D in level flight is irrelevant, or better is if it is little bit higher compared to "proper airfoils"

RandySmith · « **Reply #13 on:** September 16, 2009, 02:52:32 PM »

Quote from: Igor Burger on September 15, 2009, 01:19:10 AM

That wing is just wrong:

1/ too sharp LE and too thinn airfoil will need low wingload for usefull flying and it will make troubles in turbulence. We need wing loading as high as the good arfoil allows it. Means we need blunt and thick airfoils.

2/ that wing has 3D ailerons. not flaps. Flaps shoul be concentrated at root, not at tips of wings. It is because flaps on tips can cause stalls at tips and thus troubles. Ratio flap chord to wing chord shold be bigger at root and smaller at tip. - thisis just opposite

3/ our flaps should be flat, not intedgrated to the airfoil, because they shoul have the best efficiency (good L/D ratio) deflected, while L/D in level flight is irrelevant, or better is if it is little bit higher compared to "proper airfoils"

Hi Igor

I agree completely with the "wrong wing" assessment. I also found the same about flaps in my early test, it seem to me to be much better to have more of the flap area at the root, and less at the tip
You also get the added benefit of having the flaps stiffer the closer to the horn the most part of the area is.
I also found out the same about flaps being more effective as a separate cut and not as part of the airfoil. I built 2 of the exact same planes with this, one had the flaps cut into a foam wing as part of the airfoil, and the other had sheet flaps, same area, the sheet flap plane flew better cleaner squares, and lock on 90 degrees better. The plane that had the flaps cut into the same airfoil as the wing , had the mishap of the wood sheeting popping loose from the foam , so I replaced them with solid sheet wood flaps later in it's life ,and showed the same improvement after.

We have also seen with some of the AFR and ARC CL stunt planes here that being too sharp on the LE is a deal breaker as far as stunt goes, that type of LE will make the plane stall much faster, and doesn't track well in the maneuvers.
I also do not like a large amount of sweep forward on the flap hinge line, many of these ship have a lot of sweep in the flaps

Regards
Randy

Dennis Adamisin · « **Reply #14 on:** September 16, 2009, 05:21:11 PM »

As a former believer in the blunter is better and thickest is best paradigms, all I will say is - it ain't so. I remember seeing a plot in an aero book show that CL Max occured with roughly 15% thickness, no further improvement to 18% then deteriorated after that. the excellent model airfoil tests (mostly for sailplanes) by Dr Selig pretty well proves it too.

Bluntness has been oversold too. Anything beyond a roughly 1/4" RADIUS is diminishing returns. I recall that Al Rabe's stunt airfoil work also concluded that too blunt was too bad. The very blunt foils are simply too "dead" around neutral and will not fly at all unless they are tricked by aft CG's and huge tails - even then they simply have to have too much angle of attack to fly a precise line.

Randy's comment about structural rigidity of the flaps is spot on, and thicker flaps have more chance of being built stiff than do thin flaps.

I'm not running out to buy a 3D ARF but I am looking at better ways, beginning with abandoning fashionable but too thick & too blunt 'foils.

RandySmith · « **Reply #15 on:** September 16, 2009, 08:32:20 PM »

Quote from: Dennis Adamisin on September 16, 2009, 05:21:11 PM

As a former believer in the blunter is better and thickest is best paradigms, all I will say is - it ain't so. I remember seeing a plot in an aero book show that CL Max occured with roughly 15% thickness, no further improvement to 18% then deteriorated after that. the excellent model airfoil tests (mostly for sailplanes) by Dr Selig pretty well proves it too.

Bluntness has been oversold too. Anything beyond a roughly 1/4" RADIUS is diminishing returns. I recall that Al Rabe's stunt airfoil work also concluded that too blunt was too bad. The very blunt foils are simply too "dead" around neutral and will not fly at all unless they are tricked by aft CG's and huge tails - even then they simply have to have too much angle of attack to fly a precise line.

Hi Denny

I don't use super thick blunt airfoils, mine are 18 to 19%, and I found they work better than thinner or thicker ones for me. I also don't have overly blunt LEs , about the radius of a dime..maybe a little sharper is where mine resides.
I find the same as you , over blunt LEs don't track, or handle winds well. Maybe though unlike some people..I have found that 5.5 to 1 aspect ratios are almost as high as I go, higher ones seem to give too much acceleration in winds

But I will say this, not everything can be lumped into one category,and blanket statements are not always correct.
I have flown some very very thick airfoiled planes (and built a few) that had blunt LEs that worked extremely well, were not tail heavy, did not have extra large Elevators and stabs, and turned sharp and tracked, Scott Bair's Stuntfires are a perfect example. Scott was a big believer in his ultralight program that included parasitic drag as part of his equations....The wing was one of the ways he did that...by the way, a near perfect ship for a high power electric setup

Regards
Randy

Dennis Adamisin · « **Reply #16 on:** September 17, 2009, 07:21:29 AM »

AMEN brother Randy!

You can never be too rich, too thin or have too much AR!

All seriousness aside, I actually agree that 5.5 is a pretty good set-up. Again one of those blanket statements quoting an old Aerodynamicist about Aspect Ratios: going from a AR of 3 to AR of 6 gains as much as you do going from a 6 to a 12. IMO, low AR can hurt you more than high AR can help you. I personally think that 5 is about as low as I want to go, 5.5 is just fine with me. As I recall you have had a fair amount of success with that formula..!!!

A factor not often discussed is Span Loading. Basically this means that long wing spans affect more air. To generate the required lift, a longer span deflect more air thorugh a smaller angluler change. That means long wings develop lift effieciently - without much drag - which has been the knock on high AR.

My take on AR has actually been to design for span, then add in chord until I got the area (and wing loading) I want. The resulting wing planform also happens to exhibit higher than normal AR.

One really nice thing about thicker airfoils - the are easy to build strong, which means they are also easy to build light by minimizing the structure. I think as we go below about 15% we are going to have to start worrying about wing FLEX and adding some structure for stiffness.

The trouble with LE radius is that we think of it as a radius. More accurately we should be treating the LE as a spiral of ever increasing radius until it peaks at the high point of the airfoil. Frankly I can see that in my head better than I can describe it...

...and I AGREE a StuntFire would make a killer electric. Scott's fuselage structure would be even friendlier to an electric than it was to the Tigre. The forward fusealge is also tall enough to stand the battery vertically - making it EASY to move it around for CG adjustment. I'd probably try thinning the wing some tho...!

Dean Pappas · « **Reply #17 on:** September 17, 2009, 08:39:01 AM »

Just how thin is a USA1 wing? I don't know the number but it ain't more than 15%!
Dean P.

Igor Burger · « **Reply #18 on:** September 17, 2009, 09:03:24 AM »

Dennis, round circular airfoil will never fly, that is for sure. I spoke about something what can be called "airfoil"

I am speaking about ~18% thick airfoil with LE at 3 or 4%.

It is not only how much it can make lift, but also how well it reponds to AoA. We know airfoils making lot of lift, but having bumps on polar. I wrote some years ago about it. I note that many "usual" flapped airfoils designed for wings with ailerons or tail surfaces are designed for negative AoA (moving where they are pusehed byde flected part) and thus far from our use with high AoA. Good example is Wotmann FX 71 (on pictures) ... sharper LE will make the thing even worse.

It is very often overlooked property of wing airfoil making trimming troubles. Such a model is necessary to be pushed to conditions outside of the bump, and it is very difficult to find sometimes, because it is not "visisble" like rolling, hinging etc. So it is sometimes better to have excessive LE radius and not to have such troubles.

However good airfoil is good airfoil, I agree that extremely blunt LE is not necessary.

RandySmith · « **Reply #19 on:** September 17, 2009, 01:23:49 PM »

"All seriousness aside, I actually agree that 5.5 is a pretty good set-up. Again one of those blanket statements quoting an old Aerodynamicist about Aspect Ratios: going from a AR of 3 to AR of 6 gains as much as you do going from a 6 to a 12. IMO, low AR can hurt you more than high AR can help you. I personally think that 5 is about as low as I want to go, 5.5 is just fine with me. As I recall you have had a fair amount of success with that formula..!!!

A factor not often discussed is Span Loading. Basically this means that long wing spans affect more air. To generate the required lift, a longer span deflect more air thorugh a smaller angluler change. That means long wings develop lift effieciently - without much drag - which has been the knock on high AR."

Hi Denny

I have used higher and lower, and your correct higher A|R wings have less drag and generate more usable lift per drag than Lower A|R wings. I would just point to about any sail plane.
I don't really care that much for very hig A|R wings unless I fly in stunt heaven air all the time...then I love them...
They are wonderful in really nice air.
But The lower drag is the reason I did like them for Stab and elevators with older motors.

I have also visited the 15% and under a few times, I don't care for thin wings as they sink..not really stall.. just sink. I had to use much wider flaps when using thin wings, another thing I don't like is using larger flap than I should have to. Dean mentioned Bill's USA-1 wing, Great plane, great wing but must be built light, better if it is really really light. I have seen a few heavy ones and they were not anything that I would be looking for.

Regards
Randy

Dennis Adamisin · « **Reply #20 on:** September 17, 2009, 08:02:31 PM »

Quote from: RandySmith on September 17, 2009, 01:23:49 PM

I have used higher and lower, and your correct higher A|R wings have less drag and generate more usable lift per drag than Lower A|R wings. I would just point to about any sail plane.
I don't really care that much for very hig A|R wings unless I fly in stunt heaven air all the time...then I love them...
They are wonderful in really nice air.
But The lower drag is the reason I did like them for Stab and elevators with older motors.

I have also visited the 15% and under a few times, I don't care for thin wings as they sink..not really stall.. just sink. I had to use much wider flaps when using thin wings, another thing I don't like is using larger flap than I should have to. Dean mentioned Bill's USA-1 wing, Great plane, great wing but must be built light, better if it is really really light. I have seen a few heavy ones and they were not anything that I would be looking for.

Regards
Randy

I LIKE the high AR when the wind is blowing and especially in turbulence - because the wing never stops flying. I know I will always have that turning ability to escape impending disaster...

There is a lot of great work being done with model sailplane airfoil design - though not much I have seen that looks directly applicable to our situation. The good old NACA profiles work well, but you'd think something clearly better is out there. The Wortman that Igor posted is one of those very interesting foils. I do not think I would use one as shown but with some changes in the reflexed zone it could be a real keeper.

Just a quick aside, some day I hope you get a chance to see William DeMauro's excellent SV-11 fly. Electrics are compatible with current designs, they do not really NEED thin wings, but they will help enable them, with the payoff of somewhat less battery usage.

Igor Burger · « **Reply #21 on:** September 18, 2009, 02:21:10 AM »

Dennis I do not know if you can really save some mAh. Yes you can save it in level flight. I will take two expmples NACA 0016 and 0018.

The drag coefficient in level flight at lift = 0.125 is 0.015 for 0016 and 0.016 for 0018 so it is really 7% less.

But if you look what happens in corner, you will see that 20% flap deflected to 30 degrees and AoA making lift 2.2 pushes drag to 0.049 on 0016 and 0.046 on 0018. Means what you save in level, you must pay back in figures. Because thicker airfoil performs better in maneuvers. And I can tell you that NACA 0018 can be optimized for better performance in maneuvers and it can have drag 0.040 at lift 2.40 you will never have such result with thinner or sharper airfoil. If you do not slow down model in maneuvers, you will save much more power.

But it is not all, drag in figures will need more power to keed the same quality of flight (speed stability) without active regulation, so after all you will probably need more mAh on that thinner airfoil. And if you count also another advantages of thicker airfoil (better AoA response, rigidity, smaller thus less draggy wing ...) then those 18% is good number :-)

RandySmith · « **Reply #22 on:** September 18, 2009, 09:29:01 AM »

"I LIKE the high AR when the wind is blowing and especially in turbulence - because the wing never stops flying. I know I will always have that turning ability to escape impending disaster..."

Hi Denny

Ditto.. that is what I like about my airfoils I am using in the SVs, they will turn in about any winds I have ever had to fly in, even ones approaching 30MPH. as long as the planes are not loaded up with nose weight, they turn remarkably well with near the same corner in calm or higher winds. All I ever do is make an adjustment and pull the handle overhang back 1/16 to 1/8 inch and the ships turn very quick and flat in high winds. I have flown several NATs and TTs with winds over 20MPH. That was not alawys the case with many of the planes I have flown in the past.
But the bottom line is" as long as your happy with your airfoils and setups that is all that matters. and there are several ways to skin a cat!

I have spoke with Will a lot ,especially when he was building the ship, I would enjoy seeing it fly in person, maybe soon

Regards
Randy

Dean Pappas · « **Reply #23 on:** September 18, 2009, 10:53:55 AM »

Quote from: Dennis Adamisin on September 17, 2009, 07:21:29 AM

AMEN brother Randy!

You can never be too rich, too thin or have too much AR! ...

The trouble with LE radius is that we think of it as a radius. More accurately we should be treating the LE as a spiral of ever increasing radius until it peaks at the high point of the airfoil. Frankly I can see that in my head better than I can describe it...

Hi Dennis,
You mean like a plain old NACA 64XX series airfoil? Eeegads!

Dean P.

Author Topic: ERATIX .25 3D R/C ELECTRIC STUNT??? (Read 4439 times)

Walter Hicks

Walter Hicks

Alan Hahn

Walter Hicks

Walter Hicks