RE: Moving 40 years of scale models?
We moved about 15 years ago and had not only a lifetime of modeling stuff but also 3 full sized antique airplane projects, two antique cars, and a rather extensive shop. We moved every last stick ourselves. Fortunately we were only moving about 200 miles, so we made multiple trips. I pointed out your thread to my wife and she reminded me of where she got boxes for the magazines. Go to a Girl Scout cookie sale and volunteer to haul away all their empty shipping boxes. The boxes are a perfect size to hold magazines and when filled they aren't too heavy to lift. The Girl Scouts will love you for hauling away their empty boxes. Maybe you should also buy a few packages for cookies for good will and for something to much on while driving the U-Haul. Dick
Posted on: 10/22/2009 11:16 AM by Author "otrcman" in the forum "RC Scale Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=9193359

RE: Arsitocraft f3f-2 biplane with retracts
2wingsonly, I just discovered your thread here after answering your PM about my F3F-2. Wish I'd found it a long time ago. Could you tell us the final weight of your plane? Mine weighs 99 oz. complete but without fuel. That's 6 lbs 3 oz. I've got a Saito 50 for power, and have not yet flown the plane. Also, I'm curious about a couple other details: 1. How did your wing / stab incidence work out ? Is the elevator pretty much neutral for level flight ? 2. How about the CG ? Is it in the spot shown on the plan or did you change that ? 3. Mention is made of revising the horizontal stabilizer shape. Did you make it larger than the original model showed or simply reshape it ? 4. How about ground handling ? Are you having much trouble with swerving or ground looping ? 5. Have you spun your plane ? From what I have read, the full scale plane must have been pretty marginal for spin recovery. To share more information about my F3F, I'm embarrassed to say that my landing gear does not retract. I just wasn't up to that level of commitment. My CG for the first flight is right about 24% MAC, which was achieved with no ballast other than a Harry Higley brass prop nut. The airplane has not yet been flown, however it is fully completed and has been taxied. As I noted in our PM, my closest suitable flying site is 65 miles distant. But just knowing that you have had success with your F3F gives me a whole lot more confidence. One other thing I did was to install a rate gyro on the rudder. I've found a gyro really tames down the directional control problems of a tailwheel model. I have not successfully posted a picture on RCU something about RCU not being compatible with the Safari browser. If you wish to post the picture that I sent you that is fine by me. Dick
Posted on: 10/19/2009 11:04 PM by Author "otrcman" in the forum "RC Scale Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=9186939

RE: THE HAWK FLIES
Well done, Franklyn. I saw a Goldberg P6-E fly some years ago and it looked fantastic, but it also was flown by a very capable RC pilot. It had a glide like a Phantom with both engines out. And by the way, Thank You For Your Service. Dick Fischer
Posted on: 10/16/2009 7:18 PM by Author "otrcman" in the forum "Golden Age, Vintage & Antique RC"
http://www.rcuniverse.com/forum/fb.asp?m=9178891

RE: Silkspan and dope Questions.
I'm usually a slow thinker. Sometimes REALLY slow. Mulling over your crazing problem I got to wondering whether it's a chemical incompatibility or simple lack of adhesion. If you tried painting dope directly onto metal, it would shrink up and peel because the dope couldn't stick to the metal. Maybe that's what is happening on your cowl. Is the plastic surface wrinkled or showing damage in any way? If the plastic looks pristine, them maybe all you need is a primer coat that bites into the plastic and is compatible with dope. Dick Fischer
Posted on: 10/16/2009 7:10 PM by Author "otrcman" in the forum "Golden Age, Vintage & Antique RC"
http://www.rcuniverse.com/forum/fb.asp?m=9178877

RE: Silkspan and dope Questions.
Dang, I hate it when that happens. One other approach to doping the cowl would be to put some kind of barrier coat between the plastic and the dope. Epoxy comes to mind, as it is a lot less aggressive than the dope. One downside to non-soluble finishes like epoxy is that the dope has a hard time biting in for adhesion. To solve the adhesion problem you can spray on a coat of epoxy and then follow up with a coat of dope just as the epoxy becomes tacky. Let that cure, and then subsequent coats of dope will adhere well to the dope undercoat. How did you like the Jetco kit, Steve ? I have a Navigator kit which sends conflicting messages. One side of me wants to build it, while the other side thinks it's really neat in the box just as it is. Dick
Posted on: 10/16/2009 10:56 AM by Author "otrcman" in the forum "Golden Age, Vintage & Antique RC"
http://www.rcuniverse.com/forum/fb.asp?m=9177829

RE: Silkspan and dope Questions.
[quote]ORIGINAL: Doc.316 Does the dope eat the windshield? Can I lightly sand the edge of the windshield, glue her on, mask and then shoot the edges of the windshield when I am shooting the rest of the color? Thanks for your time, Steve [/quote] Hmmm. There seem to be several different window materials. What exactly you have is hard to know. To be sure of compatibility, it would be safest to test a sample before doing it on the airplane. Some of the window material is referred to as "butyrate plastic", so that should be OK. Sometimes you can get away with minor incompatibility by holding your airbrush way back and just fogging on a few dry coats. That way there is very little paint solvent to attack the window. Backup plan: Make a template of the window before you glue it into place. That way, it's easier to make the replacement if things go wrong. Dick
Posted on: 10/10/2009 10:43 PM by Author "otrcman" in the forum "Golden Age, Vintage & Antique RC"
http://www.rcuniverse.com/forum/fb.asp?m=9162755

RE: Sterling P-63 King Cobra restoration
Thanks for the update, Chris. We're all still out here waiting for a pilot report ! I was admiring the picture of Maxey holding his P-63 (Post #61) just now and noticed that particular model doesn't have an upright engine. Looks like it might be side mounted with the head on the left side. This is one more indication, as we speculated before, that Maxey may have built a whole new airplane at some point. Dick
Posted on: 10/9/2009 7:32 PM by Author "otrcman" in the forum "Classic Pattern Flying"
http://www.rcuniverse.com/forum/fb.asp?m=9160243

RE: Silkspan and dope Questions.
Hi Doc, Sounds like you are pretty much on the right track now. I'm assuming that when you say "supercoat", you're talking Sig products? If you use the Sig line of dope, you can mix or overcoat the butyrate products just fine. Clear over color shouldn't be a problem. But be careful with the nitrate dope, even if it is the same brand. You can use nitrate dope for the undercoats, but once you apply an overcoat of butyrate, then you have to keep using butyrate from then on. The Sig "low shrink" clear butyrate and all of the colors work fine without additional plasticizer. Sig says these dopes are made from a low shrink base, whatever that is. Will this be a glo fueled model or is it rubber band? The reason I ask is because the modern butyrate dopes don't seem to be as highly fuel proof as they were in years gone by. In areas where exhaust or raw fuel will be getting on the model, it helps to apply a final coat of some kind of highly fuel proof clear. Some folks have mentioned spray can polyurethane clear like you buy in a hardware store. But I haven't had much luck with the brands I've tried. My current final coat is a two-part polyurethane used on full scale airplanes, called Stits Aerothane. But you have to buy a quart of that stuff and it's pretty expensive. I understand Klass Kote clear (advertised in the model mags) does just as well for a lot less money. Dick Fischer
Posted on: 10/7/2009 11:44 PM by Author "otrcman" in the forum "Golden Age, Vintage & Antique RC"
http://www.rcuniverse.com/forum/fb.asp?m=9155524

RE: OS Minitron 12 channel reed
Thank you for posting this, MeowJPN. It brings back many memories. I had never seen an OS reed radio, but it appears to be of very advanced design compared to the reed radios with which I was familiar. The transmitter is no doubt capable of "simultaneous" operation of some channels. If you wish, you may apply rudder and elevator control at the same. If I am correct, you will hear two reeds vibrating at the same time. The simultaneous sending of two tones has a very unique sound. Dick
Posted on: 10/6/2009 1:12 PM by Author "otrcman" in the forum "Golden Age, Vintage & Antique RC"
http://www.rcuniverse.com/forum/fb.asp?m=9151304

RE: Babcock Aeronca ready for maiden
You know, Russ, it's just possible that you are the most successful flier of a Babcock Aeronca in the history of the model ! As you say, we'll never know for sure unless some folks with "back then" actual experience can be found. Here are some random thoughts in no particular order: 1. Maybe your model flies as well as any Babcock Aeronca ever did and the guys from 1958 would be truly impressed if they could see your model fly. 2. Or, maybe the successful rudder-only fliers of the old days were very good at trimming and flying such models. 3. Maybe Mr. Hollinger's balsa prototype (I'm assuming that's how he did it) flew fine at a lighter weight and he too was appalled at the way the plastic plane turned out. 4. Maybe nobody ever got under 26 ounces back in the old days either. I was initially surprised that your model came out heavier that the original's claimed weight, given today's much lighter radios. But reading through your posts, it sounds like the model needs quite a bit of weight in the nose to achieve the desired CG. That would have been true in 1958 also. 5. This is just a general observation from my experience with Babcock radios back in the late 1950's. If Babcock put the same amount of field testing and development into the Aeronca that they did into their radios, then you probably have more flight time than Babcock ever did. I was consistently unsuccessful with my Babcock radio equipment, and numerous trips back to the factory didn't help much. My first really successful R/C flights came only after abandoning Babcock as a lost cause and buying an Orbit single channel receiver and transmitter. In fairness, I should say that I made many successful flights with a Babcock compound escapement. Dick Fischer
Posted on: 10/6/2009 11:46 AM by Author "otrcman" in the forum "Golden Age, Vintage & Antique RC"
http://www.rcuniverse.com/forum/fb.asp?m=9151058

RE: Babcock Aeronca ready for maiden
[quote]ORIGINAL: maxpower1954 One thing I forgot to mention is I have slightly more dihedral than called for - 2.25 inches per panel, versus 2.0 on the plans. Could that be part of the problem, do you think? Russ Farris [/quote] Hi Russ, I've been following your Babcock saga but hung back without posting because I wasn't quite sure what your "dutch roll" characteristics were. I'm still not positive whether your airplane is oscillatory or simply way too rudder sensitive. Either way, I couldn't help commenting on the increased dihedral. Let's try to break this dutch roll thing into component parts. First, we have an airplane that rolls quickly when it is sideslipped. As you know, an airplane with a lot of dihedral rolls quickly when you apply rudder input. So half of the equation is how much "roll-due-to-sideslip" the airplane exhibits. When you added dihedral, you made the airplane so it rolled more for any given amount of sideslip. The other half of the equation is how easily the airplane sideslips, either due to rudder input or due to turbulence. Common things that make an airplane sideslip (yaw) easily are: (1) lots of rudder area or travel, (2) very small total vertical tail area, (3) a short tail moment arm, or (4) lots of lateral area forward of the CG. Oh, and (5) could be a large prop and powerful motor, as doc.316 mentioned. If you build in lots of roll-due-to-sideslip and ease-of-sideslip, you have a nightmare scenario. A gentle nudge of rudder and you are off to the races. And every time you make another input to quiet things down, away you go again. How to fix the problem? There are several fixes, and you intuitively picked a good one by increasing the vertical area. You essentially made the airplane more resistant to sideslip by adding vertical stabilizer area. Notice that it didn't take much, either. Here are some other potential fixes: Reduce your wing dihedral. This works on the other half of the equation by reducing the amount of roll that you get from a given amount of sideslip. A good example of this fix is the B-25. Early B-25's had straight dihedral, which caused the airplane to roll too much with an engine out. Later B-25's had the outer wing panels "flattened out" to reduce roll-due-to-yaw. Made it a much more easily controlled airplane with one engine out. The other fix is to move the CG forward a bit (sorry UStik, we disagree on this one). Moving the CG forward has the effect of increasing directional stability more resistance to sideslipping, or yawing. Moving the CG forward effectively lengthens the tail moment arm and reduces the lateral area forward of the CG. As a bonus, if shortens the moment arm from the CG to the prop, thereby reducing the destabilizing effect of the prop. Of course you may have to fiddle a bit with elevator or wing incidence to get the pitch trim back where you want it. Doc316 is right on the money when he says that flight test is an essential ingredient for dealing with this sort of problem The interaction of directional stability and dihedral effect is a very complex subject and doesn't lend itself to pat answers. Dick
Posted on: 10/4/2009 12:27 PM by Author "otrcman" in the forum "Golden Age, Vintage & Antique RC"
http://www.rcuniverse.com/forum/fb.asp?m=9145660

RE: real scale flight
This discussion seems to have sorta died out, but I came into some information today that might be worthwhile. In a prior post I related that I had talked to a former co-worker who had flown the full sized C-47 / DC-3 and I asked him about stall characteristics. In that discussion I was told that the full sized airplane has very strong buffet which warns the pilot against further angle of attack increase. Well, my friend called another of our former co-workers, who was chief pilot. That gentleman said that he had gone a bit farther into the stall regime and the full scale airplane exhibits a strong roll off when sufficiently provoked. So there's the bottom line. The DC-3 models do the same thing as their full scale counterparts they drop a wing quickly. The only difference is that the model pilot doesn't have the benefit of feeling buffet which might warn him not to pull the stick back any further. Dick
Posted on: 9/27/2009 2:01 PM by Author "otrcman" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=9127521

RE: Anti Yaw Device
[quote]ORIGINAL: dick Hanson This is why the std procedure on an old tail dragger is to kick th tail up as soon as possible to reduce wing drag and put the prop at it's best (90) angle for max thrust and least gyro / advancing,retarding blade/etc.,effects angle. [/quote] Dick, I'm always trying to learn something new. In your comment about kicking the tail up as soon as possible, are you talking models or full sized ? Dick Fischer
Posted on: 9/25/2009 10:13 PM by Author "otrcman" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=9124409

RE: Some info on a yard sale spitfire?
Hi Bob Frey, I sure would be interested in having a copy of the articles you wrote on upgrading the Sterling Spitfire. If you could send me a note with the costs involved, I will be happy to pay in advance. dick(dot)fischer(at)mac(dot)com I read and re-read the AM article by George Harris (still have the magazine) and as soon as I got out of college in '64 bought a kit and built it. First powered with a K&B 45 (not enough) and later by a SuperTiger 60, it was an easy and safe flier. First radio was an Ace (Kraft kit) 10 channel reed set and later a Kraft propo. On one occasion I fluttered the elevator and broke the pushrod connection. Flew it down with no elevator control at all and the only damage was a broken prop and a scraped spinner. I've recently acquired a new Spitfire kit off ebay and intend to build it, this time with retracts. The new kit is a later edition, with nylon bellcranks and revised plans showing proportional radio. Unfortunately, the wood in the newer kit feels more like oak than balsa. Probably use most of the kit wood as templates. I did check the link posted above in hopes of finding a fresh canopy (mine is smashed on top). The site came up OK, but I didn't see any reference to a source for the canopy. Am I missing something? Thanks, Dick
Posted on: 9/23/2009 12:01 PM by Author "otrcman" in the forum "Golden Age, Vintage & Antique RC"
http://www.rcuniverse.com/forum/fb.asp?m=9117918

RE: real scale flight
[quote]ORIGINAL: UStik Here's a [link=http://www.youtube.com/watch?v=3pKk9KCVpIA]video[/link] of the maiden flight of a Ziroli 1:8 DC-3 - turned out to be a sad day. I really feel sorry for these guys, but have to say that the too short flight looks exactly like a stalled flight in the simulator, that wavering and uncontrollability and tilting over to one side or the other. [/quote] Yes, a sad end for that Ziroli DC-3. But what great pictures ! Having spent part of my flight test career doing stall/spin research, that is really classic stuff. Notice the nose slice (yawing in the direction of the roll) signaling the onset of each departure. That is some of the best footage that I've ever seen. At wing stall, most people think in terms of loss of lift. But the other and usually more dangerous effect is the huge increase in drag that accompanies flow separation. The drag increase, if it occurs on one wing more than the other, precipitates a yawing motion which exacerbates the flow separation. The greater flow separation causes more drag and more loss of lift, and more yaw, and on and on. Truly an unstable divergence. In retirement, I have been doing (full scale) flight instruction in advanced skills & techniques. Mostly what I do is take Cessna flyers and make them into competent vintage airplane pilots. Vintage airplanes typically have tailwheels, no artificial stall warning, and lots of adverse yaw. One of the things I usually demonstrate is that you can fly straight and level just above stall speed using only a whisper of power. Then a little additional up elevator and the airplane stalls. Rather than recovering immediately in the conventional FAA approved fashion, I hold the stick aft, keeping the airplane fully stalled, and work the rudder briskly to avoid rolling off in either direction. At this point the student is directed to look at the rate of sink. What he sees is that the airplane is coming down like a load of bricks while still using the same amount of power that kept us nicely airborne when just a few knots faster. Then the stick is allowed to go forward slightly so the wing is no longer stalled. With no change in power, the sink rate goes away and you are back to level flight. A truly graphic demonstration of drag increase due to stall, and also a demonstration of the treachery of an unsymmetrical stall. I also warn the students not to try this unsupervised unless there is plenty of space between the airplane and the ground, because one false move precipitates a spin. Dick
Posted on: 9/10/2009 1:08 AM by Author "otrcman" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=9083395

RE: *Airtronics RD8000 2.4 GHz*
[quote]ORIGINAL: BelAirBob Everyone will argue, but certainly some of the best batteries can be purchased from SR Batteries. www.srbatteries.com They can fit most any batteries for any application. The batteries I have from them are always at the rated capacity and maintain that capacity. Check out their website. They are not cheap, but you get what you pay for. If you do get a battery pack from SR, they can tell you what you need to charge it with and how. There is loads of info on RC Universe on all the different brands. bob [/quote] Well Bob, you won't get any argument from me. My experience with SR has been 100% positive. They use the best cells they can get, assemble them in very high quality packs, and then test them thoroughly before shipping to the buyer. They are technically very competent at what they do and work hard to maintain their reputation. With regard to the stock packs supplied with the RD8000 and RDS8000, I am still using the pack that came with my RD three years ago, and also the pack that came with my RDS one year ago. I use the wall wart that came with the radio except when I'm doing a capacity check. While I was a bit dismayed by the rapid initial drops in voltage, I must admit that both packs have given satisfactory service. I do a capacity check about twice a year to check for end-of-life degradation and so far have not seen a need to replace them. But when the time comes, it will no doubt be from SR. Dick
Posted on: 9/7/2009 9:36 PM by Author "otrcman" in the forum "RC Radios, Transmitters, Receivers, Servos, gyros"
http://www.rcuniverse.com/forum/fb.asp?m=9077360

RE: real scale flight
[quote]ORIGINAL: UStik Now, after testing spalex's model in the simulator, I can verify all what otrcman and BMatthews recommended. The simulator model isn't completely realistic but it shows it's characteristics rather clear. [/quote] Gosh, can your simulator tell you all that? Guess I haven't given simulators much thought. I'm working out the control laws for a twin
Posted on: 9/4/2009 7:50 PM by Author "otrcman" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=9070323

RE: real scale flight
[quote]ORIGINAL: UStik DC-3 had NACA 2215 airfoil at root and 2206 at tip. A quick check with [link=http://www.mh-aerotools.de/airfoils/javafoil.htm]JavaFoil[/link] shows the former being very docile (stall-wise) while the latter is nasty, at least at model Re numbers. That might have been a problem even in full scale, considering the wing sweep giving additional pitch up when stalling the tips first. (And the normal down pitching moment of the airfoil is reduced at stall.) Had the original DC-3 wing washout or did they simply fly at high aoa only with flaps down? Both would work but it's still speculation. Someone here who knows the facts? [/quote] We used to have a utility C-47 at a place where I worked. I just now got off the phone with an old co-worker who was one of the company test pilots and flew our C-47 regularly. In answer to my question about stall characteristics, here is what he told me: The airplane buffets very heavily as the stall is approached. In addition to the tail buffet, there is some pitch nodding. He said he did not recall pressing deeper into the stall because of the severe buffet. Also, his recollection was that he had satisfactory roll control at all times. So there is our answer to why the full scale airplane has so many loyal admirers and such a good operating history. Apparently the buffet warns the pilot away from further increasing AOA and he never gets into trouble. As far as operating with the flaps down, the lift coefficient is increased with no further increase in AOA. I rode in our C-47 many, many times and don't the pilot ever doing a 3-point landing. Now I know why. I agree with the other posters that any savvy modeler would look at the DC-3 wing and shudder. It has all the elements necessary to cause a nasty tip stall wing taper, thickness taper and leading edge sweep. Maybe if we could feel stall buffet in our transmitter sticks we could stay out of trouble too! The only option that we have with our models is to carefully limit elevator travel such that we never quite get to the stall point. That's basically what the full scale plot is doing. Dick
Posted on: 9/3/2009 11:13 PM by Author "otrcman" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=9068500

RE: real scale flight
One other thought regarding scale motions that occurred to me after posting. Several years ago my friend Bob Hoey experimented with scale models of ravens (the birds). His models were full sized and had similar weights and inertias to the real birds. Even though they didn't flap, Bob's models looked eerily "alive" on a gusty, turbulent day. I'm sure it was the body motions that made them look so real. Bob even had occasion to soar with a gaggle of ravens, who accepted him without alarm. When Bob eventually ran out of lift and landed, one of the ravens landed along side and walked around the model, evidently wondering what was wrong with his new friend. Dick
Posted on: 9/3/2009 5:10 PM by Author "otrcman" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=9067639

RE: real scale flight
[quote]ORIGINAL: BMatthews The trick is to fly a light model with minimal control inputs so that the model is smooth and slow to respond. This can give the impression of a big heavy model but while it's flying at the more scale like speed that can only come with super light wingloadings. Sailplane pilots are often good at this since they've learned that pushing the controls around just causes drag so they tend to just breath on the sticks and wait patiently for the model to SLOOOOOOOOWLY respond with course changes. [/quote] BMatthews, Yes, I forgot to mention that aspect of scale flight. We can break "scale motions" into three general areas: 1. Linear motion. That is, travel along the longitudinal axis of the airplane. Speed, if you will. That's where fourth power scaling looks good. 2. Turning motion. That would be level turns and loops. Third power scaling works good at that weight. 3. Angular motions. Especially angular accelerations. These are motions around the axes of the airplane. Think rolling, wing rocking, and turbulence response. Full size airplanes have lots of inertia, so they respond slowly to control inputs and turbulence. Smooooth control inputs are definitely in order for scale-like flight. I once experimented with rate gyros in a park flyer (GWS Tiger Moth 400) and was surprised at the beneficial effect of the gyro in the roll axis. The roll gyro made the little Tiger Moth seem much larger, both visually and in pilot feel. Dick
Posted on: 9/3/2009 5:01 PM by Author "otrcman" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=9067626

RE: real scale flight
[quote]ORIGINAL: Jim Thomerson How are people figuring scale speed? I might think of it in terms of airplane lengths traveled per second. Is that reasonable? [/quote] Good question, Jim. This discussion has passed over some of the basics. To make a model visually appear to be travel at a realistic speed, you have to scale the relationship of size and speed. As you suggested, this means that the model would travel the same number of fuselage lengths per second as does the real plane. Then it looks right to the eye as it flies by. To accomplish this requires that the model weight be scaled by a definite ratio to the real plane. Without going into the math, it works out that "fourth power scaling" will get you the appearance of scale speed. As an example: If we want to make a DC-3 model that is 1/12 of full size, the weight needs to be 1/12 X 1/12 X 1/12 X 1/12, or 1/20,736 of the full size airplane's weight. Since the weight of a full size DC-3 is around 35,000 lbs, the model would need to weigh 35,000 / 20,736 = 1.7 lbs to fly at scale speed with a similar stall margin. That's why we don't see many models flying at scale speeds. There is a further complication in this weight scaling business. If a model is "fourth power scaled", it only looks right in straight flight. A model scaled to fly at that speed will make non-scale maneuvers. For instance, a turn at any given bank angle will have an unrealistically small radius. If you were to scale a fighter or aerobatic plane, the loops would look impossibly small compared to the size of the model. In order to make the size of your maneuvers look right, it is necessary to do "third power scaling". That is, the model weight would be 1/12 X 1/12 X 1/12, or 1/1,728 of full scale. That would be 35,000 / 1,728 = 20 lbs. But then the speed looks too fast. The bottom line is that there is only one scale ratio which gives a perfect match of both speed and maneuver size. Unfortunately, that's full size. The best we can do with scale models is somewhat of a compromise between visual speed and maneuver size. That would be about "three point five power scaling". If you have a scientific calculator, you can do that. In the case of the 1/12 scale DC-3, the weight ratio would be 1/5985, or 5.8 lbs. I'm sure there will be folks who will disagree with this analysis, but "the physics don't lie". There has been a lot of pretty good work done in this area over the years. An example of where serious scaling analysis is used would be flight testing of spin models by NACA and NASA. Dick
Posted on: 9/3/2009 1:25 PM by Author "otrcman" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=9067133

RE: two motors with two esc's question
[quote]ORIGINAL: Dangaras The problem is a BEC is a simple DC voltage power supply. They are not designed to share current into a load (the receiver). There is no guarantee that each BEC is going to have the same output voltage as the next one, and that can lead to all sorts of power source & sink issues. One BEC might supply power to the RX & to the other 3 BECs because is is 0.5 V greater than the other 3, then it runs too hot, cuts out (or the other cut out) & you lose it (them) plus the motor(s). Then the others can go into a crazy source- sink oscillation, who knows what happens then..... [/quote] As a person who knows just enough about electronics to be terrified of its mysteries, your explanation makes a lot of sense. On the other hand, I am flying a twin with both BEC's feeding the receiver without a problem. When making my installation, I contacted the manufacturer (Scorpion) and was assured that running both BEC's would be OK, although I couldn't expect to see the full combined current rating of both BEC's. Lucien Miller (Mr. Scorpion) said that he was working from actual experience with multi-motored installations in his own models. I wonder if Castle is just being more conservative or if there is some design difference in ESC's ? Dick Fischer
Posted on: 8/16/2009 12:13 PM by Author "otrcman" in the forum "Brushed/Brushless motors, speed controls, gear drives"
http://www.rcuniverse.com/forum/fb.asp?m=9020285

RE: Babcock R/C history
I had a Babcock single channel receiver in about 1959. It was really small for the time, all transistor, single relay, in an orange plastic case. It was CW type, not tone. Cost was $29.95. The bad news was that I never got it working well enough to fly in a plane. I even took it directly to the Babcock plant in Costa Mesa for tuning and trouble shooting. Some of this lack of performance was probably my fault I was 17 years old and not too savvy in electronics. BTW, the model had a Babcock compound escapement, which worked very well. I still have the escapement. Much later, in the early 1970's, I worked on a drone project for NASA. That drone used a Babcock military receiver, a BCRD-31 as I recall. It was very solidly built and gave us lots of trouble from time to time. The RF link wasn't my area of concern, other than that it needed to work. I never really understood whether it was Babcock trouble or operator trouble. But we sure cussed it a lot. I often think that we may have set drones back many years by our early foibles. But on the other hand if we hadn't butted our heads against the wall so much maybe there wouldn't be Predator drones today. Dick Fischer
Posted on: 8/16/2009 11:48 AM by Author "otrcman" in the forum "Golden Age, Vintage & Antique RC"
http://www.rcuniverse.com/forum/fb.asp?m=9020224

RE: Welcome to Club SAITO !
[quote]ORIGINAL: Hobbsy Yes sir, I make 1/8th turn changes and check the transition and top rpm after every other change. When you get close, one of the changes will make more difference than the previous ones. PS, don't forget to keep lowering the throttle as the idle improves. [/quote] Hobbsy, thanks for the help on the Saito 50. As you suggested, I leaned the HSN to peak and then began to lean the LSN for best idle. I got nearly one full turn more on the LS than I had before, and now I can maintain a safe idle of 2000. The rich running in mid range is significantly reduced. It still sounds a bit rich in mid range, but no visible smoke. Dick
Posted on: 8/3/2009 7:58 PM by Author "otrcman" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=8987380

RE: Welcome to Club SAITO !
[quote]ORIGINAL: Hobbsy Yes sir, I make 1/8th turn changes and check the transition and top rpm after every other change. When you get close, one of the changes will make more difference than the previous ones. PS, don't forget to keep lowering the throttle as the idle improves. [/quote] Hobbsy, when you say that you check the top RPM after every other change, do you actually adjust the high speed needle to be sure that you're at the peak, or are you simply looking at the tach to see that your peak RPM hasn't changed ? Dick
Posted on: 8/3/2009 11:14 AM by Author "otrcman" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=8986038

RE: Welcome to Club SAITO !
[quote]ORIGINAL: Hobbsy Dick, if 2,900 is the slowest idle you can get the LS needle is still way rich, the .50 should idle at 1,800 and smooth as silk. Set the LS needle with the HS needle at absolute peak. The LS needle controls about 85% of the throttles range so if it is too rich at idle it wll be too rich in the midrange. [/quote] Thanks, Hobbsy. I'll give that a try and report back. When setting the LS needle, do you make your adjustments with the engine running and continually test for lower idle, or do you use some other method to detect the optimum spot for the LSN ? On my 80 twin (two carbs) I found the best results by holding a finger about an inch from the exhaust outlet and feeling the temperature and steadiness of the exhaust pulses. When the LSN's were about right, I could detect a distinctly steadier pulsing of the exhaust and also a steep rise in temperature. Sure is messy, though ! Dick
Posted on: 8/2/2009 11:45 PM by Author "otrcman" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=8985161

RE: Welcome to Club SAITO !
OK, I've read all the recent posts regarding setting the hi speed and low speed needle valves, but I've still got a question. The engine in question is a Saito 50 which has an unknown history but seems to be pretty well broken in. I did have to replace the carburetor, which was missing when I received the engine. So the carb is brand new. I've got the HSN and LSN pretty well set. Top end is maybe 200 below peak. Idle isn't great yet, but is steady and reliable at about 2900. Engine may not be fully broken in. The thing that seems strange is that the engine is quite rich in the midrange. Lots of smoke in the 5000-6000 range, both throttling down and throttling up. On throttle burst from idle there is very little hesitation and not much smoke, which makes me think the idle is pretty close. Forgot to mention: Fuel is Cool Power 15% with 2% Sig castor added. Plug is OS Type F. Any ideas? Thanks, Dick (# issued but don't recall it)
Posted on: 8/2/2009 10:30 PM by Author "otrcman" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=8984958

RE: Dale Root's Low Ender
A while back someone on this thread wondered if Dale Root was still alive. The answer is no, he passed away sometime around 1980. This morning I ran into an old friend at the flying field who knew Dale, and remembering this post I asked if he could add to our knowledge. My friend Jim said he met Dale in the early 1940's when Jim was still in high school. Dale mentored Jim through such things as running engines, prop carving, and silk covering. Dale routinely took Jim along with him to the flying field in his Model A Ford. After closing down Root's Hobby Hut, Dale went to work for Lawrence Livermore Labs. Unfortunately, Dale was a lifelong diabetic and Jim speculated the diabetes had brought an early end to a very productive and generous life. Jim is very high in his praise of Mr. Root both as a kind friend and an excellent modeler. Sounds like the kind of person we all wish we had known. Dick Fischer
Posted on: 8/2/2009 1:04 AM by Author "otrcman" in the forum "Golden Age, Vintage & Antique RC"
http://www.rcuniverse.com/forum/fb.asp?m=8982864

RE: Mean aerodynamic chord
[quote]ORIGINAL: HighPlains We discussed tail size and the implications of fixed stick vs free stick three years ago in this thread. http://www.rcuniverse.com/forum/m_4279429/anchors_4279429/mpage_1/key_stability/anchor/tm.htm#4279429 As far as the part about flying cross country by trimming it to fly level and controling direction with just rudder. It must have been more common in the past. My dad got his license back in the 50's and it was quite common back then. I also read an article about Steve Wittman a couple years back and he mentioned the technique as well. When I got my private, my instuctor also showed doing the same, though for shorter periods. Anyway most GA airplanes are flown with a rather light touch so the controls are reversable, and the pilot is not adding too much to the stability. I also remember that Barnaby Wainfan wrote on the subject in his Wind Tunnel series in the Kitplanes magazine sometime in the last couple years. His monthly articles alone make the magazine worth subscribing to. [/quote] HighPlains, I read the thread that you referenced and it was really good. Guess I missed it the first time around. One note regarding flying full scale with your feet only versus my earlier Bonanza example: You are absolutely right in your experience. In smooth air, flying hands off is about the best flying you'll ever do. On my Bonanza example, the pilot was pressing on both rudder pedals simultaneously to create a quasi "stick fixed" condition. The locked rudder control stopped that annoying tail wagging motion that Bonanzas exhibit in rough air. If I could summarize from your referenced thread and the current one, it might go like this: 1. When compared to a full scale prototype, an R/C model gets greater benefit from it's empennage surfaces because the movable controls are held rigidly in position by the servos. Note that this is only true when scaling full scale airplanes with "reversible" (cable or pushrod controlled) surfaces. F-22's with hydraulic controls don't count. But think about something like a Jenny, with its tiny fin and huge rudder. The full scale Jenny is directionally unstable, whereas R/C Jenny's are quite stable. 2. Full scale planes have somewhat of a stability advantage over models because the pilot is more tightly "in the loop". The full scale pilot can see and feel angular motions of the ship he's sitting in, and he can make very timely corrective actions. The R/C pilot depends more on seeing flight path deviations, which occur later than angular deviations. An example of this difference is taking off and landing a tailwheel airplane. The R/C pilot sees lateral excursions from the runway centerline, whereas the full scale pilot sees (and feels) the early excursions from runway heading. 3. Free flight and early R/C models usually had large horizontal stabilizers because they did not have active pilot control in pitch. The larger horizontal helped eliminate porpoising. Modern R/C models have active control in pitch, so they can get away with smaller horizontals. 4. The control loop between pilot and airplane is a bit more tenuous in an R/C model because the R/C pilot has only distant visual reference. Larger tail surfaces make the models easier for us to fly. But a reasonably skilled R/C pilot seems to be able to fly nearly any configuration that a full scale pilot can fly. 5. So, do you need to enlarge your tail surfaces on a scale model ? You can if you want to. The model will probably be easier to fly, particularly if the full scale prototype had smallish surfaces. But you can almost always fly your model with scale sized surfaces if you don't get the CG too far back and you have appropriate flying skills. Dick Fischer
Posted on: 7/30/2009 12:38 PM by Author "otrcman" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=8976400

RE: Mean aerodynamic chord
[quote]ORIGINAL: Shoe There is a subtlety to calculating aircraft stability when you have a ''reversible'' control system. A reversible control system is one where if you push on a control surface, the push force will be transmitted all the way back to the stick or rudder pedals. Pure ''cable and pulley'' systems are typically reversible, whereas control systems using hydraulic or electrical servos are typically irreversible (pushing on the elevator on most RC planes doesn't result in a corresponding force on the stick). For airplanes with reversible control systems, stability is typically different depending on whether the aircraft is ''stick-fixed'' or ''stick-free''. Do you include elevator/rudder area when calculating stabilizer surface areas? For the vast majority of RC models... yes. For some (typically light, manned) airplanes, the answer is ''it depends''. Do you include aileron area when calculating MAC? Absolutely. MAC is used primarily in longitudinal stability calculations. Even in the case of reversible, stick-free ailerons, pure longitudinal motion will not typically result in a left or right force on the stick or yoke (in which direction would the force push the stick?). So full aileron surface area would always be included. For lateral/directional stability calculations with a reversible control system, you would need to consider both stick-fixed and stick-free cases. Your question is a good one. Bottom line: for 99.9% (or more) of RC aircraft, you include all of the aileron/elevator/rudder area for stability calculations such as MAC. [/quote] Interesting and well stated, Shoe. Think of the implications to those WWI planes with all-movable vertical tails. The directional stability of something like a Fokker Triplane is completely different in an RC model as opposed to the full sized plane. This is a subtlety that not many "real" aero engineers understand. I had been out of school and working as a flight test engineer for a couple of years when a friend pointed out that he could stop the "tail wagging" in his Bonanza by placing one foot so it bridged both rudder pedals and then pressing as if it were the brake pedal on his car. He didn't know why, but it worked. After a few minutes of thought, I had a EUREKA! moment. Dick Fischer
Posted on: 7/29/2009 3:16 PM by Author "otrcman" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=8974074