wjcalhoun

Al
Absolutely right; I should have mentioned CG as an essential part of that statement. Every trimming guide that I have ever read STARTS with CG. Change the CG, and all other trimming must be redone, or at least re-checked.

Forward CG-> higher stall speed -> faster landing speed

Obviously, the CG cannot be TOO far aft, as the aircraft is unstable, and our brains, at least my brain, is not as fast as the FCS for an F16 It would be cool to equip an aerobatic plane with a gyro (and VERY quick digital servos) to experiment with the flight envelope that might be possible with a 'too far aft' CG, or an inherently unstable airframe - the way an F16 is inherently unstable.

Best regards
Bill

ahicks

My Feedback: (2)

You can tell that you're getting too far back when the plane slows down. The tail will no longer be able to support the weight it was when you were going faster. So the tail settles, the nose comes up, and you need to do something about that in varying degrees according to how far back you are. As you go back it eventually gets to the point where it gets to be a pain maintaining airspeed at lower throttle settings. You know you're there or maybe you've gone a little too far.

Guys that are used to flying with CG's way back think nothing of having to give the plane some down elevator to keep it from slowing too much. The plane flies pretty similarly otherwise. You just need to assume responsibility for maintaining it's air speed. With a way back CG, it can't do that by itself any more? Playing around with a rear CG can give you a degree of control you've never experienced before. It's kinda like the plane has brakes on it when you need them? To illustrate maybe, my Revolver can come straight down out of a stall turn on the downwind end of the runway, and land without running out of runway (300 ft') even with no breeze to help slow it (or flaps/spoilers)? -Al

8.point.roll

Hi guys,

ahicks

My Feedback: (2)

You're talking about what is known as a forward slip in full scale flying, and it's much easier to do it when you're looking out the window rather than when on the ground looking up at a model!

You kick the plane sideways with the rudder, so the side of the plane is acting like a big air brake. You correct the flight path/counteract the rudder input with opposite aileron, using the degree of opposite aileron to steer the plane - which is dropping like a rock because of all the drag. The beauty of this maneuver is that you're dropping like a rock, but you are not building up any airspeed....

Exciting maneuver in full scale. It's used a lot when coming in to a short grass strip with a stand of tall trees you need to clear on the end of the strip? You clear the trees as low as possible using a normal approach, then kick the the plane sideways into a slip to drop it about 50 feet, then release the slip and complete the rest of your landing normally? This will leave you out of breath the first few hundred or so times you fly it.... because you're so busy you forget to breathe?

My RC attempts at this generally look like a misdirected power off knife edge ending when the plane is getting low enough to scare me! I have done it nicely, and I've seen it done nicely, but it's not something that's easily done. Looks awesome when done by a larger (1/3 scale?) Cub or Citabria.... -Al

ahicks

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double post. haven't done that in a while!

lopflyers

My Feedback: (12)

Wow, ive never seen that done, im not planning to try it either. My heart is too weak

8.point.roll

Yes, that is it! Slipping the plane!. I agree with Lopflyers, too scared to try it! It does sound difficult, and I would probably do as you say and start with a high wing trainer-type plane of the Cub variety. You know, I have never owned a Cub and that sounds like a really good plane for my next one! When I tell my wife that is my next purchase, I WILL use you, Al, as the reason I HAVE to buy this plane to do a new manuever!

Seriously, that was a great discription. I am going to see if I can find a video of the slipping manuever. Will also try on my RealFlight sim. although that may not work as effectively as "real life" at the field.?

Thank you for your help in getting me to better understand how using the rudder helps slow a plane down. Actually, we have a very small runway at my club's field and trees lining the edges at both ends, so learning how to "slip" may prove very helpful, esp. w/ the R70.

Thanks again, Al.

-8pr-

ahicks

My Feedback: (2)

Thanks for the memories generated by the question. I learned to fly full scale as a result of my passion for flying RC. I had already been doing that for quite a while going into full scale. Although I never was able to afford any real aerobatic training, I had a few instructors willing to push a plane to it's design limits? Did you know a Cessna 172 was certified to spin?

Anyway, regarding the forward slip, I forgot to mention that while holding full rudder and steering the plane (that's now flying sideways) using the ailerons, you had to monitor your airspeed VERY carefully, and adjust that as necessary using the elevator. Consequences for letting the plane get too slow were no different than if the plane were going straight. It will stall...... and when that happens, adventures in "unusual attitude recovery" generally begin. And yes, we practice MANY mistakes high prior to shooting actual landings.

Sorry for wandering off topic, but for those with any aspirations of learning to fly full scale, go for it. It's a total sensory overload, and you'll change your approach to flying RC forever. -Al

wjcalhoun

Hi Guys

Had my R70 out today and wrung her out a bit. I bought a new Futaba 14SG radio, had the new Bowman ring in her, and just had to get out.

Top GPS speed about 118 mph, airspeed about 104 mph (15mph wind from the south). For a reason I'll have to determine, she was more touchy with the new radio; i'll have to tone down the low rates a bit. The DLE20 with the Bowman ring performed flawlessly, to my perception, the vertical pull is even better; she probably now accelerates going vertical (that with a 12 pitch prop). I have not yet gotten the 13.5 pitch prop mounted, but i'll get the speed data within a couple weeks. The DLE20 turned 9300 rpm during flight, so she unloads 600-700 rpm from on the ground.

Usual maneuvers - upright and inverted flat spins, knife edge flight, knife edge spins, hammerheads, avalanches, etc. Brought her down after the second flight and I noticed that the cowl looked odd. The cowl mounting blocks on the starboard side had pulled away from the firewall.

In looking at my Eagle Tree instruments after the flight, I think it probably was the knife edge spin that tore the cowl off; she was rotating about 100-120 rpm (almost 2 revolutions per second) around the wing-tube axis in a KE spin, at 70% throttle. I had several g's measured during that maneuver in the y-axis, along the wing tube, plus the incredible aerodynamic stress on the cowl from that rotation speed. I also had a -5.4g recorded in the z-axis (yaw axis, up and down) which I suppose might have pulled the cowl away also, but I think it was probably the KE spin.

It will be a quick fix.

The R70 really is a fun plane.

Best regards

Bennijiggs

Prop sizes I have tried so far are 16x6 and 16x7. I tried a 15x7 on the ground but rpm was over 10500 so I took it off. I also have a 15x8 and a 17x6 in the bag but haven't tried them. What are some other sizes for good high speed with out putting to much strain on her?

wjcalhoun

Bennijiggs

If you are running a DLE20, you are way underpropped, especially if you are at NM altitude. Ground RPM of 10500 is too fast. If you see that on the ground, you might be seeing 12,000 in the air, unloaded. Your big end bearings have a limited lifespan at 12k. You could look on this forum about what prop sizes work. 16x6 is not one of them. That would be more for a weak 1.20 size engine, or a strong .90.


17x6 is said to be the 'best' prop for the DLE20, but 16x8, 15x10, and 14x12 give progressively better airframe speed at the expense of 'pull'.
It really depends on how heavy your airframe is. If you are pulling a ~10# revolver (a very slippery airframe), you can prop the DLE20 up for speed. If you are pulling a 15# cub, or a draggy biplane, you probably need the 17x6.

Jedijody (formerly from VVRC) has a pretty comprehensive list of props and rpm at the beginning of the DLE20 thread.

The data are out there.

Bennijiggs

Calhoun,

I do have the DLE20. thanks for the prop info. Just put my 17x6 on. Will fly her tommorow. I also ordered the 16x8 and the 15x10 to try it out.

Does any oe have a caliper tool or know what size axle we have? I want to put on some Robart low bounce wheels and need the axel size. My buddy at the field has a few extra sets but told e he needs my axle size.

microdon2

My Feedback: (47)

On TH, under Revolver \ Other Items of Interest, the Dubro Low-bounce 3 1/4" wheels listed have a hub diameter of 4mm.

Bennijiggs

Md,

Thanks!

ahicks

My Feedback: (2)

I've been babying my stock 'glass landing gear lately, knowing one side was cracked and that replacements are on back order (due late July, but still not in stock). It finally let go over the weekend so the plane is grounded until the back order is released. I'm wondering if anyone has a set of the stock gear, or maybe just the left side, that they might be willing to sell reasonably? No interest in converting to something different - yet. Thanks, -Al

wjcalhoun

Hi Al

I'll look in my LG box this evening and let you know. My recollection is that I have at least one side from my R70 #1, but I'm not positive.

8.point.roll

Gas newbie questions (as related to the DLE 20cc & Revolver combo):

JH313

Hello,

microdon2

My Feedback: (47)

JH313 - Sorry to hear about your Rev 59 crash. Last crash I had due to lost elevator the cause turned out to be the elevator lead pulled out of the radio (it was the only lead pulled out). Was on an 80" P51 Mustang (beautiful plane, too), and, in hindsight, I must have tugged on that lead inadvertently while pushing the six servo leads into the fuse just before closing the wing (to screw it in). Now I tie-wrap all my servo leads two inches above the receiver (after someone told me about that trick) - so now no leads are pulling out. Could this have been the cause in your case?

Mike

wjcalhoun

8 point

You can use 3/16" for the DLE20, and actually for 55cc engines; plenty of capacity. I plumb with Viton in the tank, and from tank to carb, but use tygon for fill and vent lines. Your choice.

There is likely to be a great storm of controversy on the oil / gas questions

a. Most people do not like LawnBoy - use Pennzoil air-cooled if you use mineral oil for breakin. Some just go with synthetic from the start. Get a Bowman ring.
b. Pump gas is fine; the carbs have components that withstand E10/E15. The issue will be stability. I always add fuel stabilizer to my 5gal gas cans when I fill them at the gas station, and have not had a problem. Some swear by no-ethanol gas, but many of us have had no problems with regular pump gas in our toy engines.
c. Oil ratio (according to the gas engine gurus) is set by the engine manufacturer, not by the oil refiner! Therefore, it is probably good to run 1:32 in the DLE20. Bigger engines that need proportionately less lubrication can run well on 1:40 or 1:50. The DLE20 might as well, but i'm mixing my DLE20 oil (mineral or synthetic) at 32:1.

Finally, it is always fair to ask a question.

microdon2

My Feedback: (47)

wjc - what do you mean by gas "stability"? What does a stability additive do, and what's a common brand? Thanks.

8.point.roll

Hi Bill, thank you very much for all of your answers. Awesome... thank you on all accounts.

Now to build her all up. I am slow, so bear with me on the build. I have another plane that is my priority at the moment, but am putting in all my questions prior to my build, as well as getting alll of the addon goodies (fuel, tank, filters {using a felt type }, fuel can, hand pump, BEC, etc. etc. etc., etc. the list goes on, and on, and on, ......................... !

I truly do appreciate this forum... the best forum for a plane I have ever come across.

Thanks again Bill...

-8pr-

P.S. I almost forgot... what about the servos in the rear of the fuse... is that going to improve or negatively effect the CG. I read some people have found with the servos in the rear, it has improved (or offset) the heavier weight of the DLE 20. Is that true? Do I need to put everything in and check or can I just believe that the servos in the rear balance her out pretty good and I do not need to worry... just go with it. I know, I know, that's a pretty loaded question, but if I can avaoid doing the trial and error method, I would prefer that, ya know?

lopflyers

My Feedback: (12)

JR, sorry about the loss, u can certainly deal w aileron, rudder or even throttle loss but the elevators...... That's certain death

kcarson

Bill - cannot find my original photo, but another is attached (as long as RCU does not reduce the size). Basically, on the Rev 70, a cut piece of 1/8th inch angle that ties the firewall to the landing gear block will do the trick. Then, install the 2-piece gear set and place another piece of straight alum stock on top. Some people use the Dubro gear, but I did not. And I have had zero (knock on wood) problems with about 35 + landings.

ahicks

My Feedback: (2)

8PR-
I appreciate the offer for the loan of the gear, but I don't dare take you up on it for fear this could be a long drawn out deal, and I would hate to leave you bare handed when you need them!

Servos in rear will help your CG. You need to build the gassers carefully to avoid being too nose heavy without adding ballast. I even ended up changing the spinner for a lighter one?

I use the same 1/8" tubing I used for my glow engines. It worked fine for those, and these gassers use nowhere near the amount of fuel the larger glow engines used (thinking up through 3500 Super Tiger here).

I had the reason the smaller gassers use more oil (32:1 vs. 40-50:1) explained at a level I understood easily not too long ago. It's about how much fuel they use, or more accurately, how much they DON'T use? Because they just sip their fuel, you need to feed them a mixture containing a higher percentage of oil to keep them happy? I just picked up a new 10cc Revolution gasser the other day, and they're at 20:1 for their diet! Knowing/understanding like I do now, I won't be questioning that ratio much.

I buy quality oil wherever I'm at. Walmart, Pep boys, whatever. I look for one thing on the label, and that's the fact it must be approved for air cooled engines. Past that, I don't even look. I'm already on my way to the check out counter.

JH313 - when you start playing with gas, vibration and extra weight/stress become a fairly large factor, or if not, it will. For instance GP uses a lot of solder on clevises in their kits, supplying them even in their largest kits. These do not mix well with gasoline engines, suffering a fairly high failure rate. Likewise CA hinges. It's best to treat the gasser as a new/different breed - requiring hardware way heavier than somebody used to messing with 60 or even 90 size planes is used to? This is another of those believe me now or pay your dues later warnings. FWIW, -Al