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Oct 28, 2020, 06:13 AM
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From the Cave on the Cove

For many years, I administrated a Forum for my local RC Club. That Forum has now been closed down. There are a number of articles from there which I wanted to preserve, as well as a number of pictures and links to YouTube and Vimeo videos. So, I set up this blog and plan to include future items that I, or others, generate.

Please note: Roughly the first 70 items in here were moved over from that Forum. If you skip past the first part (mostly my semi-instructive ravings), you will get to where there are some pretty good videos and stuff.

I am a retired Systems Engineer (B.A.Sc., Mechanical Engineering, 1970 - i.e., an old guy) who spends a great deal of his time creating, building and flying RC models of various kinds and sizes. I have been doing this for over 40 years, as well as having about 20 years (800 hours) of flying (Canadian and USA licenced) and instructing (Canadian licenced) in full scale gliders in my past history. My aviation interests transferred to my son, who is now a production test pilot for a major aerospace firm. He has been an RC modeller for almost 35 years now, having soloed at age 7 and becoming an RC instructor a couple of years later. Good kid.

I live on Preston Cove, situated on a large island (pop. 600). I can walk out my door, down to the water (or ice) and fly or walk out into the front yard to fly small things and dodge trees. No nearby neighbours in any direction to annoy! However, I get the most out of travelling to one of my two clubs to enjoy good flying and comaraderie, any day of the week throughout the year.

I refer to the messy so-called shop wherein I build and repair models as my Cave. (My wife has another name for it.)

Hence then name: The Cave on the Cove.
Last edited by Deerslayer; Nov 04, 2020 at 11:56 AM.
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Oct 28, 2020, 09:32 AM
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Tie Your Kangaroo (and Aircraft) Down, Sport

Restraining aircraft is not just for starting!

How many times have you seen someone leave a model, particularly a foamie, sitting on a bench or table outside and then get blown off, possibly getting damaged? Or, worse yet, damaging someone else's property!

If you do have to leave a plane on a table, consider lying it upside down. That way, it is less likely to take off or blow off.

Another thing that many are unaware of is the sudden, severe gust caused by a thermal kicking off, usually from the parking lot. A couple of years ago, as I was taking my glider back to the truck, THREE of my aircraft which were on the ground - 2 foamies and a 40-size balsa were suddenly picked up, lifted over our vehicles and flown around the parking lot about 20 feet in the air, then plunked down upside down. Only minor damage to the 2 foamies, none to the bigger plane. The neighbouring Fun Cub was carried around a bit on the ground. It was all I could do to hold onto my glider for a few seconds, on the truck tailgate, until things settled down. No damage was done to any vehicle.

This has happened many times. On another occasion, a large beach umbrella took off, flailed around in the air and broke my windshield. If that thing had hit someone, there would have been blood!

PLEASE, think about this and take some precautions.

Someone remarked that they thought you would only get this kind of thing on a hot summer day. Incorrect! In both of the incidents mentioned above, it was a cool day, light wind, but the low level atmosphere was moderately unstable. When the parking lot warmed the air, reached the trigger temperature and a thermal bubble or column of air suddenly rose. Surrounding air rushed in to take its place, its speed increased by flowing between the vehicles. That's how it happens, folks!   

I have seen full sized sailplanes, weighing upwards of 600 lbs, easily lifted from the ground - usually because they were not properly restrained and without having their dive brakes locked open.
Last edited by Deerslayer; Oct 28, 2020 at 09:59 AM.
Oct 28, 2020, 03:04 PM
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Injury Management and Prevention

• Avoid flying by yourself in remote locations such as most r/c fields, back lakes, etc. Always know where emergency help may be available.

• Let someone else know that you are out flying, including the time you left and an anticipated return time, as well as your cellphone number.

• Keep a fully charged cell phone in your pocket - not at home or in the car!. This is particularly important if you must fly by yourself.

• If you go out into the woods to search for an aircraft, let someone know where you are going and the maximum time you expect to be gone. If there is no one else around, leave a note on your car window with this information. When you return, let the person know that you have returned. This is much like a Flight Plan that the “real” pilots file.

• When preparing a glow or gas plane, tie it down or otherwise secure it. If
someone is helping you, make sure that both parties know what they are doing and do not make any sudden, instinctive moves to correct a perceived engine problem!

• When preparing, carrying or retrieving an electric aircraft, employ a positive “throttle lockout” and/or disconnect the power source in the aircraft. Treat electric-powered aircraft as you would a loaded firearm!

• A full bottle or thermos of fresh water should be part of your field kit at any time. This can prevent dehydration at any time or to cleanse a cut, if necessary.

• Have access to a simple First Aid kit. Keep a kit or basic materials in your car or flight box. Take a few minutes periodically to confirm that it is where you think it is and that it contains some basic materials that you might want.

• Our most likely injury is a laceration due to a prop strike. If you have only one item available in your kit, it should be a roll of gauze bandage.You have to stop any bleeding! Everything else can wait.

• You may have to support the injury. Wrap an injured finger and then wrap it to an adjacent one. For a hand or arm injury, wrap it and then support it in a sling or sleeve.

• If the injury is serious enough to require immediate professional attention, do not bother applying any antiseptic; the professionals will have to wash the injury anyway.

• Remember to replenish any items you used from the First Aid kit.

• Watch for shock! Even a minor cut may induce some degree of shock, whereby you suddenly feel weak, dizzy and/or you may fall. For most injuries, sitting or lying down and keeping warm and calm will overcome the feeling. Make your helper aware of your symptoms.

• If you are seriously injured, do not try to drive yourself. Call for, and wait for, help. There is at least one documented case whereby a modeller sustained a significant hand injury, started to drive to the hospital, then passed out from shock while driving and hit a tree. He died! This is where flying alone, especially in a remote location, magnifies the potential post-injury hazard.

• Make sure someone else knows what has happened. If there is only the injured person or one other, use a cell phone or neighbour's phone and contact someone else. Ask them to come out and remain with your gear and the injured person's vehicle. Update them periodically after you have reached medical assistance.

• When did you have your last tetanus shot? This is a deadly disease. Its cause can be precisely the kind of conditions that you may have encountered at this time. Tetanus shots should be renewed every (10?) years – ask your doctor what is recommended. If this injury requires professional treatment, you should be asked about your tetanus shots and you may be given one at that time.

• In the event of a major injury, you should call 911, rather than trying to transport the person.
Oct 28, 2020, 03:08 PM
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Flaps, Flaperons and Flapless Flaps

Question: Why do I write this stuff? Because I think about it - a lot. Perhaps someone else out there has similar thoughts, or questions, and might be interested in one of these topics. So, here are some thoughts about "flippers".

Today, even many of the beginners' airplanes have Flaps, as well as independent servos for the Ailerons. In that aviation classic, "Stick and Rudder", the author refers to the control surfaces of aircraft as "flippers". I really like that, as it separates physical control(s) from their potential function. Check out
to learn more about him.)

There are some useful ways to make use of the "flippers" on your aircraft apart from how we usually think of them. Here are some of my thoughts.

About 30 years ago, I acquired my first "computer" radio, i.e., a transmitter which allowed what was then the relatively uncommon technique of electronically mixing or coupling of channels on r/c planes. I immediately wanted to emulate what I had seen the "hot dog" flyers do, on my primary sport plane. I explored the idea of using the Ailerons as Flaperons, under certain conditions. This also enabled me to "mix" (I prefer the term "couple") the Flaperons to follow the Elevator input.

When Ailerons simultaneously move down, they are termed Flaperons. If they both move up together, they have become Spoilerons. In either case, they can still behave as normal Ailerons, even while displaced from their normal Neutral position.

The purpose of Flaps, or Flaperons, or a combination, is to alter the Angle of Attack (AoA) of the wing. In doing so, its Lift/Drag is altered. At low settings, say up to 20 degrees, employing Flaps or Flaperons should increase Lift along with a moderate increase in Drag. At higher settings, Lift will not increase very much and will quickly deteriorate at very high settings; meanwhile, Drag increases significantly. So, you can end up with a highly variable Lift to Drag ratio (L/D), tailored to your needs during different portions of your flight. For instance, to shorten a take-off, deploying low to medium (perhaps 10 to 20 degrees) Flaps and/or Flaperons can result in an extremely short pop into the air and an amazing rate of climb. This can be especially useful on a seaplane, that is otherwise difficult to yank off the water - as long as you couple the Flaperons in with the Elevator.

You can judiciously use this feature to improve your L/D, say, during a final approach with a dead engine, in order to save your plane. Landings, especially with a normally pitch sensitive aircraft, the approach and landing can become slow, smooth and precise with very little effort. It may even help solve the tendency of some planes, like WW1 fighters, to nose over upon landing. Overall, you can become a better manager of your flying!
I prefer to employ the Ailerons as Flaperons, even if the aircraft has Flaps. Furthermore, I do not use preset settings for Flaps or Flaperons, i.e. no "Flap switch" use. I prefer to use a Mix to couple their function to the Elevator, and possibly to the Throttle (to serve as Spoilerons). This gives the best of all worlds, i.e., continuously variable L/D of the wing for all conditions. Normally, this is dictated On/Off by a switch, as there may be times when such coupling is undesirable. This whole arrangement is like having an extra set of hands at your command. Try doing really tight touch-a-goes, gradually decreasing the total flight path and time and you will see what I mean! It can get to be very exciting and addictive! A great way to really learn about your aircraft and your own piloting capablities, as well as to improve upon both!

The way to set this up is to, first of all, throw away any Y-connector you may have to control the Ailerons. (Aside: Those things are tools of the Devil, having caused the loss of one of my own prized toys, as well as those of other flyers I have known.)

You must have independent channels, so that means at least a 6-channel Transmitter and Receiver for plane without Flaps. Then create a Mix with Elevator as the Master and the Ailerons as Slave, so that Up Elevator brings in Down Ailerons. Now, these "flippers" have a dual function - Ailerons and Flaps. As a starting point, set this to perhaps 30% and choose one of your Switches to select/deselect this function. The result is that, as you feed in Up Elevator, you will be feeding in a proportionate amount of Down Ailerons, i.e., you now have Flaperons!

Note: If you are not already using Exponential on your controls, this is a good time to start. Your flying will become more relaxed, more precise and you will be able to detect small changes in behavior of the aircraft. Some flyers seem to avoid Expo. By doing so, they are missing out on perhaps the best thing to have come out of the development of radios. Many of us, including the 3D flyers, will use 60% or higher Expo on Ailerons, and/or Elevator and/or Rudder.  Avoid so-called Dual Rates to reduce your control throws - all they do is cut down on your control authority, reduce the precision of what is left and may leave you sorely lacking in that little extra "oomph" just when you need it the most! Major Expo will give you all of the advantages, yet you have 100% control movements available at the extremes. 

First flight:

Deselect this Flaperon Mix, take off, get some reasonable altitude and with the plane trimmed for reasonably slow flight, select your Flaperon Mix. Play around with pulling Up Elevator, see how the plane behaves. Do a few loops at various speeds, with and without the Flaperon Mix engaged. You should see a major difference, with much tighter loops and yet no greater tendency to tip stall while the Mix is operating.

Slow the plane down close to stall, then work the Elevator to see how it behaves. You should notice that the plane can be flown significantly slower with the Flaperon Mix than without it. Play around with it, have fun and learn about your aircraft's flight envelope.

Land as usual, with or without the Flaperons engaged. If you do have them active, plan to keep your landing speed low, then do a really good hold off as you begin to flare. You should be able to do a great, fully controlled landing at low speed and in a shorter than usual distance. 

Next flight: Select the Flaperon Mix for take-off. Take off as usual, don't haul back too aggressively on the Elevator or, if you do, be prepared for a surprisingly quick and steep take-off.

You have now seen the three major advantages of using Flaperon Mixing: Short take-offs; slower landings; and, some tighter aerobatics.

So, what next?

Experiment with the amount of coupling you use. I have upwards of 60% on some of my planes, and you may find that you have a wide range of values to try out. Have fun, learn things, discover you plane's inner soul!

But, wait! What about the other trick with Ailerons, i.e., creating Spoilerons?

If you set up the other half of your Mix to raise the Ailerons in unison as you push Down Elevator, you now have Spoileron capability. A cautionary word: This may, on some planes, result in a rather aggressive drop in altitude and/or pitch change that may concern you, so start with a small amount of coupling, say 20%, until you have tried it out. Assign this to a switch.

Another option for having Spoilerons is to couple them to the Throttle, so that bringing the Throttle down will gradually raise the Spoilerons. Set it up to be switch-selectable and don't use really high amount, at least at first. Perhaps try a 20% or 30% mix. Now you have an option to descend rather rapidly, which could be useful in doing the really hot, really cranked-in  touch-and-goes. It is best to make sure that you have your Elevator-to-Flaperon Mix active at the same time. 

Some may have noticed that I have shown up at our field over many years with some airplanes of my own design which have unusually shaped Ailerons. This is an approach which give one the benefits of having a wing without Flaps becoming as useful as one with separate Flaps, without using more servos/channels. These flippers will gradually taper down from the last, say, 10% of total Aileron length to perhaps 1/2 of their width. The innermost 30% or so of the control surface will become significantly wider than the rest of the surface, blending in via a nice curve. This inner section of our "flipper", being within the high energy region of the propwash, does not need to be very large to have a major effect upon the airflow and to contribute greatly to downwash and Lift. The blending in of the enlarged section to the reduced portion is intended to reduce the disruption to the airstream that an abrupt change would have. My theory!

Here is the effect of this unusual Aileron profile, as used through 20+ years and  many generations of these planes:

These flippers are now Flaperons/Spoilerons. You can get at least as good effect as you would with separate Flaps, but with simplicity and automation. They can be switched On to be coupled to the Elevator as Flaperons for take-off, playing around in the air and landing. At the same time, or  preferably by a separate switch, they can be coupled to the Throttle to serve as Spoilerons. That can make for dramatically steep approaches and spot landings.

The roll rate of this configuration has proven to be much quicker than with straight Ailerons, with all mixing turned off. Additionally, you have full span Flaperons, with at least as significant effect as with separate Flaps, especially when coupled to Elevator.

But, you say, "What about tip stalls using Flaperons?". Well, in my opinion, that should be of no concern. Unlike many years ago, with certain glow planes, a modern well-designed airplane has little tendency to tip stall. Especially a light, electric one. Using Flaperons coupled to the Elevator does not increase the probability of tip stalling. If you do not believe me, set it up and do some testing in flight, at a couple of mistakes high. Convince yourself.

Incidentally, I see flyers who have never deliberately stalled their aircraft. Shocking! These folks are often the same ones who approach a landing at a blazing fast speed, fight the aircraft down onto the ground, possibly bunny-hop a few times and even visit the shrubbery at the far end of the field, complain about their aircraft being overly "pitch sensitive", and so on. They are afraid of stalling the thing, I guess.
From my full scale gliding days, and throughout my R/C flying, on the first flight of any aircraft, as soon as it is trimmed OK, I do power-off stalls. You learn a lot in doing this, including what speed is reasonable to land at, whether the plane has a tendency to roll or spin at close to Stall, how might it recover if you do inadvertently stall it, how good this aircraft is at low speeds, etc. 

This approach can be tried with virtually any aircraft and a reasonably current radio, at no cost and no permanent changes, just a simple Mix or two and the flip of a switch.

Get to know your plane! Try things! Learn stuff! Have more fun!
Oct 28, 2020, 03:09 PM
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Exponential and Dual rates

It is a slow day, no flying, so here are a few thoughts to share. Contrary opinions are most welcome, by the way.

I often run into flyers who have very different opinions on, and therefore the use of, the two most common control system options on modern r/c radios. These are Dual Rates and Exponential.

How would you like to drive a car, especially one that is new to you, where the steering wheel caused the same degree of movement of the wheel direction regardless of your speed?  Although parallel parking would be pretty much as you were used to on an "ordinary" car, it would be quite an exciting ride at highway speeds,. For the greater part of the automobile's history, it has had a mechanical exponential response. The result is, as you know, that you get modest and precise directional changes with a fairly broad range of steering motions around the center angle. Driving can be relaxing and enjoyable, not a battle between you and the car. Yet, when dodging an object or maneuvering into a confined area, you start to get major steering changes as you progress somewhat further in twisting the steering wheel.

We have this same capability with our models. It is an available, built-in option. Yet, many flyers either ignore it entirely or apply it very timidly. Many of these same flyers will have "dual rates" set up on their radio. I would like to encourage you/them to adopt a different  viewpoint.

Once upon a time, a typical transmitter that the average person could readily afford was just a box with two sticks and some trim adjustments. I am old enough to remember when this same class of radios started showing up with servo reversing switches, a major advancement that saved some occasionally awkward adaption of servo positioning in our models - especially for the Throttle. Getting a Throttle hooked up also required some messing around with positioning of the servo arm, finding which holes to use to link the arm and the engine throttle arm, etc. We were introducing exponential movement in doing so, such that at low settings we got more precise Throttle control. Similarly, we may have set up our control surfaces to achieve the same thing.

Later on, transmitters arrived with switches that introduced "dual rates". We all like new things and besides, some of us really needed some help, at least on certain models. When flying a new model, or one that was rather touchy to control, we would set up dual rates to ease the pain. Or, we might prefer to have a high rate during certain common maneuvers and a low rate during others. Aside: I think that"rate" is a poor term, as the rate of response, i.e., servo speed,  does not change; only the end points are affected, imposing an overall limit on servo travel, i.e., distance.

When so-called "computer radios" appeared, along came a new feature and perhaps a couple of new switches to play with. My state of the art Futaba 7UAFS, back around 1990, had a couple of new features, including Exponential. Like many others, I was somewhat slow to do much with Expo. Dual Rates, on some occasions, was useful - just had to remember where the switch is when you need full control in a hurry! I would often fire up a new model and, especially if it was of my own design and therefore an unknown or questionable entity,I would have Low Rates set for the maiden flight, at least until I got it a couple of mistakes high and started to learn how to actually fly it. When I was more comfortable with the model, I would ditch the Dual Rates - one less thing to remember or care about. I started to sometimes set up a bit of Expo, depending on the model. I thought that 30% was a magic number! AS Poe's raven saith, "Never more, never more". I had a lot more to learn.

Back to the car analogy: Why would you want your vehicle to have non-exponential control and instead you would put some kind of blocking device into the steering such that the wheels could only move through, say, 60% of their normal travel? Eek! impending collision, must go for the shoulder NOW! Oops, almost saved us, another foot or so was all I needed ...!

You cannot go wrong with the generous use of Exponential on some or all controls on virtually any model. (Incidentally, most of our radios also have a Throttle Curve function, which is a more customizable and more capable control similar to Exponential. Check it out.)

Talk to someone who is a good 3D pilot and ask what kinds of Exponential settings they may be using. And, do not be surprised if they also use Dual Rates . But, they really do know where each is appropriate, and by how much.

Many Bind aNd Fly (BNF) models have imbedded Exponential as one of their locked in parameters.

I have a number of planes with  60% or 70% Exponential (never Dual Rates, as I get everything I want via Exponential without hobbling the aircraft). Do not be afraid. Unlike Dual Rates, you lose nothing, full stick movements still give you full control movements. I think the Dual Rates function should be renamed the Hobble function .

Sometimes, you have a plane that is very difficult to land, being twitchy or "porpoise like", where setting high Exponential on the Elevator can tame the beast and make you a very satisfied pilot, perhaps even to be  admired by the denizens on Vultures Row !

It is there, you bought it, it works, so use it!
Oct 28, 2020, 03:10 PM
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Throttle Curves

Another more recent option in many of our radios is the Throttle Curve. Either we are unaware of it or we just never think of it as a possible improvement or solution. In the "good old days" of simple radios and glow engines, we actually did have a "throttle curve", in that the linkages were such that we most likely had an exponential response built in, i.e., degree of throttle barrel sensitivity to stick movement is much different down near Idle and at low range than it is at higher stick settings.

Electric motors can be very sensitive to power commands throughout their range. Unlike internal conbustion engines, maximum torque is available from the start. This is great for most or our work but there are times when having a smoother application of the r.p.m. toward the low end can result in easier or more precise handling.

For instance, you may have something like a WW1 replica where ground handling during takeoff is a handful. Giving the engine a shot of power to get her moving may result in a wild swing due to torque and propwash effects before you have proper rudder control. Note how small and down in the dirt many WW1 rudders are - not exactly made for great control until that tail is hoisted well up into a strong airstream. Now, it suddenly wakes up and yanks your plane around, as you are jockeying throttle and rudder, with perhaps even some aileron thrown in. Slow and steady is more likely to be the way to go, lead by smooth and gradual throttle application.

What about those nasty "bunny hops" we sometimes get into while landing. Manhandling a sensitive throttle, especially if you have shied away from using lots of exponential on your elevator, can lead to pilot induced oscillations.
Or, you may like doing knife edges or hovering and need better control of not only the rudder, ailerons and elevator but the throttle has to be carefully coordinated with all of the above to make it look good and be sustainable for a few seconds.

The neat thing about Throttle Curves, as implemented on most systems, is that you get to plot the points and to choose whether they will be straight lines or smooth curves. There really isn't much you can mess up. Your system most likely is already using a throttle curve, actually a straight line between 0,0 and -100,100 and called Curve 0. Leave that one alone. You can set up and number your new curve(s) and associate one to take the place of Curve 0 or use your Flight Modes to enable different curves for different conditions.

Here is another good use of  Throttle Curve: I often have a plane set up to do something a bit different during landing. In this mode, the lower half or so of the Throttle Stick mostly controls the Spoilerons (Ailerons acting together to become Spoilers in addition to their normal Aileron function) or Flaps+Spoilerons (Flaps moving down as Ailerons move upward, to create "Crow"). This Throttle Curve will be entirely or nearly flat-lined from "0" to a very small percentage while the stick is controlling the Crow via other mix(es) to the stick. Then, as you push the stick forward, Crow is gradually reduced and then eliminate. Meanwhile, the Throttle Curve for the upper half or more of the stick movement rapidly increases, eventually reaching 100%. This setup allows for steep approaches, great handling in high turbulence, spot landing and immediate clean-up and ready to handle a missed approach, if required.

Throttle Curves - just another location on the Learning Curve! Think about it.
Oct 28, 2020, 03:11 PM
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Range Checking

Recently, I have had a number of opportunities to help new flyers. The current environment is rich with victims to prey upon when there is a shortage of official Instructors!  

I have observed that these folks have been well conditioned to do Range Checks prior to each daily flight. Our club has good Instructors!

What I have also observed is how they do Range Checks. Just to clarify, here is the best practice, based upon the advice of real experts, such as Andy Kunz, the team leader of Spektrum's development group.

1. If you can, get someone to hold your aircraft, at waist height. Or, set it down on a bench and SECURE IT. Make sure that your Throttle Lock is on, if it is electric. Now, since you are going to be testing your system, think about what could happen if, somehow, your test were to fail and result in the motor starting. That is one of two very good reasons for having a helper hold the model. Proper Range Checks with a glow or electric are normally done with the model restrained and the engine running.

2. Walk out about 30 paces. Face your aircraft and begin the Range Check.

3. Don't just wiggle sticks around! Perform deliberate movements, eg., full Left Rudder, and hold it. Observe that your control surface moves IN THE RIGHT DIRECTION and that there is no shaking of any of the control surfaces. Good, so far! But, we are not through just yet.

4. The second reason for having a helper is to have them change the orientation of the model - both in a flat circle and holding it vertically. After all, we are usually trying to talk to the thing while it is somewhere above us. The worst situation for connectivity is likely to be with the transmitter pointing directly at the model while the model is pointing directly at the transmitter, especially if there is a motor, battery pack, etc. now between the two. One of you should call out which control and direction you are trying.

This may sound like a bit of a hassle but it is not. It takes no more time, really, to do it properly than just doing a "sort of" Range Check.

Not everyone is aware of the following. Radio waves in the 2.4 GHz are severely attenuated by water. The human body is mostly water. So,it is not a good idea to have someone  in the direct line between you and whatever you are maneuvering on the ground, or flying. The next time you do a Range Check, prove this to yourself - turn completely away from your model and see if you lose range. (Make sure that it is restrained, preferably with someone holding it.)

Disclaimer: "Do as I say, not as I do" is an old expression. If asked, I will refuse to answer as to how often I do Range Checks. It is great to see new flyers being taught good procedures and techniques and emerging from our instructional program as competent, safe pilots!

Here is what I think is a good suggestion from the Spektrum Forum (applicable to any system, of course).

Check out that your Throttle Failsafe works !!!! You should do this from time to time anyway, but let's double check it now.

Restrain your plane, either by tying it down or having someone else hold it.

Run your engine or motor at perhaps a fast idle and leave it there.

Put your transmitter into its Range Test mode. Start walking away, having the plane held facing you. This is a worst case scenario for 2.4 GHz radio communication, as for most planes there is likely to be things like the battery, engine or motor, ESC and/or other metallic or electronic objects in the path. As well, your body will be tending to  block the transmission. Did you know, the 2.4 GHz signal is attenuated (weakened) by high water content in things like clouds and human bodies?
At some point, you should hear, or your assistant will tell you, that the Receiver has lost its signal, as evidenced by going into Failsafe mode. Take the Transmitter out of Range Test and ensure that the system again responds as expected to commands.
The common wisdom says that 30 paces should be the minimum range for this to happen. It is not an exact science, and you are presenting the system with what is hopefully a worst case scenario.

You may wish to go through this exercise again, having the plane held at some different orientations, such as nose up and pointed toward the transmitter, the transmitter antenna swung around to different orientations, etc. You may learn something!

By the way, I still notice folks doing a Range Test by walking out and wiggling the sticks around to see if stuff works. While that may sound good, unless you have the plane held by someone and call out the movements you are commanding, you are missing something. The controls may wiggle, but, do they jump around a little bit and do they wiggle in the intended direction? Control check is different from Range check - do both. Stand behind your plane, prior to every flight, and go through the controls to ensure that all is well. Many of us have been caught with reversed Ailerons (most common setup mistake) or something not properly seated in.

Stack the odds in your favour, this hobby has enough challenges already. Do your checks, Fly Safely and Have Fun!
Oct 28, 2020, 03:14 PM
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Thread OP
Power and Props

 Yes, this is me but No, you should not read too much into it. I was a long term, dedicated "slimer driver", who was gradually forced to bend a little bit by accepting electrickery to power one of more sailplanes.

 Over at the Pro Bro site, there is a good question regarding calculating the requirements for an e-power system. The following reply made a lot of sense to me. I extracted it for posting in here, thinking that it may be of use to some others and/or generate some discussion on its validity. H
Your first question about prop selection and power can be answered with the understanding that so many of the variables of a power system are related. I start the process with the fact that Watts, Amps, and Volts are related.

Watts = Amps x Volts
Amps = Watts / Volts
Volts - Watts / Amps

If you know the Kv of the motor, and the efficiency of the motor, then all that is needed to calculate the RPMs is the ‘real’ volts available to the system, and the propeller constant. RPMs is important because it represents the ‘Work” performed by the system, which in physics is the amount of force it takes to move a specific object a certain distance over a certain amount of time. In our example, we’re talking about a prop with a specific constant (pK) with a specific diameter and pitch, moving at a specific revolutions per minute.

For propellers manufactured for electric motors, I have found this to be in the 1.01 to 1.10 range. APC props are usually about 1.03 and Xoar PJN props are in the 1.03 to 1.08 range and this may be due to the fact that wood props can vary in density since the material is not going to be as consistent as composites.

Let say that I have a 215Kv motor and I want to swing a 22x10 composite prop on 10 cells (~37v). Let’s also assume that the prop constant (pK) is 1.03 and the motor efficiency is 80%. With these variables, I can calculate the RPMs. Here’s the formula:

RPMs = (Volts*Kv)*(%KvE/100)

Volts = 37.0 (You can always measure volts to use the true value but 3.7v per cell is a raw estimate)
Kv = 215
Motor Efficiency = 80%

RPMs = (37 volts * 215Kv) * (80% / 100)
RPMs = (7955) * (0.80)
RPMs = 6364

With the calculated RPMs, I can now calculate the Watts required to turn the prop to this RPM. Here is the formula for Watts-out:

Watts-out = ((Diameter/12)^4)*((RPMs/1000)^3)*pK*(Pitch/12)

RPMs = 6364
Diameter = 22
Pitch = 10
pK = 1.03

Watts-out = ((22 / 12) ^4) * ((6364 / 1000) ^3) * 1.03 * (10 / 12)
Watts-out = 2686

This is the amount of power required to turn a 22x10 prop with a pK of 1.03 to 6364 RPMs.
Since we also know that W = A * v, then we can calculate the current actually used to drive the prop to 6364 RPMs:

2686W / 37v = 72.6 Amps-in

Now keep in mind that this is the amout of power and current used in the process, and not the amount of power and current going into the system. These values can be measured with any decent meter, but since they are related we can also calculate Watts-in and Amps-in.

Watts-in = ((1+(1-(%KvE/100)))*Watts-out)
Watts-in = ((1+(1-(80 / 100))) * Watts-out)
Watts-in = 3223W

This is closer to the value you will see peaking on your meter. Since we also know that W = A x V, then we can calculate the Amps-in:

3223W / 37v = 87.1 Amps

So the intended system, which is a 215Kv motor on 10 cells, swinging a 22x10 prop, will peak around 6364 RPMs, producing 3223 Watts, 2686 Watts at the prop, and pull 87.1 Amps. We also know that if 87.1 Amps are drawn and only 72.6 Amps are needed, then our current efficiency is (87.1 – 72.6) / 72.6, which is 17%.

We can also calculate pitch speed to estimate the airspeed in MPH:

MPH = (((Pitch / 12) * RPMs) * 60) / 5280
MPH = 61.7

Since we also know that there are 746 Watts to 1 Horsepower, then we can estimate that the system is producing about 4.3 HP.

If you bring the prop size, pitch, RPMs, air temperature, and pK, to one of the online static thrust calculators, you will also find than this system produces about 12.25 kg of static thrust or 26.95 pounds.

In some instances, you may find the calculations to be closer to reality than the measured values because in most cases, we have an 8 kHz pulse going to the motor and the meter is 100 Hz. Much of what is actually happening goes unnoticed.
Oct 28, 2020, 03:17 PM
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Servo Degree Wheel (written some time between one and two dog years ago)

 Do you really understand what your servos are doing, or are capable of? Me, not so much - at least until now.

We typically plug our servos into the Receiver, set up the direction via the Transmitter and perhaps make a few other adjustments, such as Dual Rates, Exponential and perhaps even Servo Travel (especially for we Slimer Drivers' throttle servos). Meanwhile, there is Sub Trim - which I have almost never used, as I employ the Old School practice of performing my neutral adjustments mechanically.

Does everyone know that you can drive a servo way beyond the standard 100% Travel? On my old Futaba 7UAFS, you could go to 125%, but I never used that much; on my Spektrum stuff, you can go as high as 150%.

I recently bought an Eagle Tree Guardian 2D/3D Stabilizer to play with. You can adjust something called Master Gain via the Tx. Whether you use a switch or a slider/knob, the commanded "servo position" signal sets this parameter. But, what does the associated Trim do throughout the servo range? Just one of many questions.

So, I made a Servo Degree Wheel jig to learn about these things. I downloaded a template of a Degree Wheel, printed and plasticized it. (A cheap protractor is good, if you have one lying around). I mounted it on a piece of coroplast with a servo at its center. The pointer is a piece of stove wire; it is not glued to the servo wheel, so that I can "zero" it, etc.

This has really helped me figure out how to set up something on my Guardian to give me specific control settings and known adjustment ranges. I now understand my radio system much better - it's about time, as I have had it for over 1 dog year!

Old dogs, new tricks ...

I could almost write an article about what I have discovered ... but that would involve Work, to which I am averse.
Last edited by Deerslayer; Oct 30, 2020 at 03:15 PM.
Oct 28, 2020, 03:18 PM
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Watch out for signs of corrosion on servo connectors, both at the servo end itself, any extensions you may be using and at the Receiver. This is especially important for those who do float flying and/or store their planes for extended periods of time. Case in point (although I have encountered this on other occasions):

I put an AR7000 into my Telemaster today. I noticed that 3 sets of the contact pins in the Reciever had greenish coating on them! These happen to be channels that were not used on the Seamaster, where it last was, or on something else (I forget which, as it was in my box for awhile).

 I scraped those pins carefully, with a dental pick and Exacto knife then brushed them with a toothbrush until there was no sign of the green crap. A little magnifying glass is almost essential here.

I then sprayed all contacts with some contact cleaner.

I plan to do a little maintenance on all of my stuff over the next while - pull the plugs, check them, spray with contact cleaner, etc. Cheap insurance!

An old trick from my motorcycling days, which I haven't bothered with on my planes but probably will do on anything that is used for float flying: Take a small dab of Vaseline and smear it onto any electrical contacts. I used to take a small paintbrush, warm the Vaseline with the heat gun enough that it could be brushed on in a thin film. You now have a perfectly waterproof connection, no chance of corrosion and have not changed the electrical properties of the connection.
Oct 28, 2020, 03:19 PM
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Press 'n Seal

In case someone else has use(s) for this stuff, it is called Press 'n Seal by GLAD.
It is a thin, clear and somewhat stretchy film, much like Saran Wrap. However, it has some sort of stick-um imbedded in the one side (microscopic, methinks). When you apply it to a solid surface, and/or stretch it a bit, the sticky side seems to get activated - perhaps by the heat of your hand? Yet, like Post-Its, it can be easily removed later.

Some folks use it to seal food, but not me! I have some other uses:

1. Clamping. I removed, modified and re-glued a plastic canopy to a foam sailplane. Having set the canopy in place (I used Weldbond glue, which is the same as RC56 or whatever "canopy glue"), I needed to keep it held firmly for a few hours. So, I cut some strips of Press 'n Seal and stretched/wrapped it around the canopy and aircraft body at specific locations. When it gets removed, it will not peel off any decals.

2. Masking. In this canopy project, and in some other unrelated cases, I applied Press 'n Seal and rubbed it down over the area. Then, with a very sharp Xacto knife (I keep the blade clean and also dress it with a fine whetstone), I can then use extremely low pressure to trace around the area I wish to protect. I carefully remove the Press 'n Seal from the portion(s) that I intend to paint. I have even done this VERY CAREFULLY on a fabric surface.  Next, I go back around my Press 'n Seal mask to ensure that it is solidly attached at all edges. As soon as I have painted, I can lift off the mask (I may use the tip of my Xacto to initiate this, perhaps using tweezers at some places to peel it away.

3. Protecting. While I was fooling around with this canopy, paint and glue, I tend to get my hands messy. I slapped some Press 'n Seal on the side of the canopy that I would be handling but not painting or gluing. When done. I peel that off. This is sort of like what you find on sheets of plastic and some plastic parts you buy.

This stuff seems to be much like the heavier, industrial stretch wrap that you sometimes see.
Oct 28, 2020, 03:21 PM
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Medical Tape

The Flypaper College of Aero-Nut-ical Knowledge teaches us to always be on the lookout for different/cheaper ways of doing things. Here is something that may be useful well beyond Foamology.

 There is a 3M product called NexCare that is used in medical work, it comes in a dispenser like "Scotch tape", and can be found at Shoppers and other drug stores. This tape is strong, does no tear, will stretch a bit and has an excellent adhesive. Yet, it is easy to peel off skin, foam, plastics or other hobby building materials. It looks slightly opague, with a pattern of dimples.

 I, and many others, have used this to make hinges for foamies, to seal hinge gaps on foamies, sailpanes, even giant 3D planes.

 Another great use is as a clamping tape when you join pieces with a slower setting adhesive or one that expands as it cures - like Gorilla and other polyurethane-based glues.

You can join the pieces, clean up the excess at the glue joint and apply slightly stretched pieces of the tape across that area to restrain it. In the worst case, when removing it,  if the tape wants to stick around the glue joint, just apply some alcohol and it should promptly release.

 I wish I had known about this long ago, when mounting or repairing canopies on models - much better and easier than using masking tape and/or rubber bands, perhaps even in combination with Stretch 'n Seal, albeit more expensive if you need to use a lot of it. It will not ruin your covering or a well-set paint job, especially if you dab it with alcohol as you peel it off.

 Of course, you can always use it (perhaps combined with a dab of CyA?) to repair a booboo on your finger from a sharp prop or Xacto blade.

 This stuff is now part of my field kit.

 This tip was approved by the Flypaper College of Aero-Nut-ical Knowledge (dedicated to my late flying buddy, Gord "Flypaper" Clifford)

           "Conquering the skies one glue stick at a time"
Oct 28, 2020, 03:27 PM
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Amazing Goop

Yup, that's exactly what they call it.

I am a sucker for buying all kinds of adhesives and scratching my old head to figure out how to use them. My so-called shop (commonly referred to as "The Hole" at my castle) where I idle away much of my winter life looks like the glue section of a crappy hardware store. It has only gotten worse since Flypaper corrupted my aviation interests toward the $Tree and electrickery.

 Recently, I used Shoe Goo to laminate some wheel sets, each from 3 sections of EPP, for a couple of Crak Turbo Beavers. I didn't want to exhaust my limited supply of Foam2Foam at the time.

 This worked out very well, so I proceeded to use the same stuff to laminate 3 sections of a slab fuselage for my latest "special project". In the past, I have done laminations with spay-on water-based contact cement. Note: Shoe Goo, the other Goop products, and many other adhesives will attack Depron and some other plastics, so you need to do a test before jumping in!

 The only drawback to Shoe Goo is that it is very viscous. So, I did some research and came across this site:

 I had not heard of "Amazing Goop" before, but it seemed like what I was after. Well, Canadian Tire just happened to have it in 2 sizes. I bought it, I used it, I like it! It is very easy to work with, less viscous than the other Goop varieties and you can easily spread it with a painter's scapula, knife, old credit card, your finger, etc.

I have used both Shoe Goo and Amazing Goop to create hinges, with great success.  Unlike hot glue, you have to let it set for a few hours, but it is an unbelievable strong and yet supple hinge. With the Amazing Goop, you just hold the 2 sections together and apply a tiny amount of Goop along the hinge line. Then spread it evenly and thinly with your spatula. Pull the joint apart, let it sit for a minute or so and then fit it back together. (Note: I think this last step is optional but may recude the time to set.) Clear up your hinge line the easy way - lick your thumb and run it along the glued area. Make sure that your hinge extends back, say, at least 1/8" or more from the actual joint. The loads on the structure will not simply pull apart the foam at the hinge. Wait a few minutes and then gently flex your new hinge slightly, just to ensure that all is well. If you happen to notice a poor section, you can add new glue at any time, even after lots of flying use.

 The stick-em world is a very confusing place these days, with too many choices. I still like Foam2Foam and Foam-Tac but this Amazing Goop has its place, albeit limited to specific foams.

 This is yet another product approved by the Flypaper College of Aero-nut-ical Knowledge,
           "Conquering the Skies, One Glue Stick at a Time"

Bonus tip: With any of these tube style adhesives, it is important to use and store them properly in order to get long shelf life and maximum glue for your buck. After I open a new tube, and periodically thereafter, I apply some vaseline onto the threaded area. That will ensure that you don't end up with a sticky or stuck top. As I use the glue, I set the tube open end up in a coffee cup or something so that there is no drip out. Before I close the tube, I wipe off any glue from the opening area, using some acetone if necessay, and re-apply some vaseline to the threaded area if necessary. Then, I gently squeeze from the bottom of the tube until there is no air at the open end, then I screw on the top. When it is sealed, I lay the tube down and carefully flatten the bottom end with a glue stick or pencil or something. The next time I unscrew the top, I am careful not to apply pressure to the tube, thus avoiding a mess.
Oct 28, 2020, 03:28 PM
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Dummy Radial Engine for Dummies

I was pondering the need to slap a radial or rotary engine on a little foam piece of crap that I recently finished. This is what I ended up with at zero cost and just a few minutes of work.

The materials are simple:
   -  a plastic bottle of appropriate size for the project (mine was a FREE water sampling bottle) to become the engine block
   -  a section of the corrugated protective wire covering that was laying around gathering dust (we used to have miles of the stuff at work and you can get some at any computer fix-it shop), it comes in a couple of different sizes and will become the cylinders
   -  some old buttons, the new cylinder heads – use you imagination, this is for long distance viewing!

My engine is a 5-cylinder radial. That means that you draw a circle on a piece of paper just a bit bigger than the engine block, i.e., the bottle, and draw radii at 72 degree intervals.

Then cut the bottle to some appropriate section thickness and using this layout, mark the locations of the cylinder centerlines on the bottle. You can choose to leave the bottle as is, or attempt to cut holes appropriate to mount your "cylinders". If you do try to drill the holes, I suggest that you do this before cutting the bottle; pack it with sand to create a solid base to drill into. I chose not to drill out my bottle.

Cut your cylinders from the plastic piping, use hot glue to seal up the joint in each. Note that this piping started out as a solid piece and then the manufacturer slit it for the originally intended purpose, so you are just undoing some of his work.

Using some degree of patience, hot glue each cylinder in place. I roughen up the bottle with an abrasive pad and clean it with acetone before this step.

Rummage around in someone's button collection until you find something that might look cool as cylinder heads. Hot glue them in place. Or, don't bother if you are sticking this thing inside of a cowl.

Paint your engine block. Cut appropriate hole to slip the thing over your motor. Mount some sort of base (foam? balsa?) to attach to your flying machine.

It probably took me 1/2 hour to do the whole thing once I found the materials. Another 1/2 hour to fix up my mistakes, etc., slap some paint on it and that's all, folks!
Oct 28, 2020, 03:29 PM
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Fun Cub-ery (written about one dog year ago)

 The little Fun Cub is a great platform to try out things on, as it has full control surfaces, i.e., independent Aileron and Flap servos.  Not that this little bird really needs anything beyond plain vanilla setups, but you really owe it to yourself to tinker.

 I will describe a little set-up that I have. Why? Because it is a "Fun" Cub. It also is a good test bed on which to learn about Flight Modes, Throttle Curves and a bunch of other stuff. In fact, this setup is essentially what I am employing on 2 sailplanes. I use my Fun Cub as a sort of test bed because I can do gazillions of take-offs and landings with it in very short times and can learn things quickly that way. Note: I am using a Spektrum DX9, either in Airplane (for the Fun Cub) or Sailplane (for the V-ROC and Heron gliders); there are slight differences in the implementation but we achieve the same end result.

 I have a couple of Flight Modes set up: Normal is plain vanilla (yawn); TOGA (Take Off / Go Around) Flight Mode is the interesting one here, as it combines the actions of Throttle on a highly exponential Throttle Curve with Flaps + Spoilerons, all on the Left Stick. I can still retain coupling of Elevator-to-Flaps-and-Flaperons and/or Aileron-to-Flap coupling on the Right Stick , if I wish, either independent of, or dependent upon, any Flight Mode. There are many possibilities to play around with, overall.

So, what is this TOGA Flight Mode all about?

First, I set up a Throttle Curve which is invoked in this Flight Mode:

 The default Curve, which most people use without even examining, is linear. My TOGA-associated Curve is highly exponential (0,5,20,60,100). The lower half of the Left (Throttle) Stick travel only drives the Throttle Channel through a small percentage of its range, from zero rpm up to a fast Idle or so; the remainder of Stick travel is more linear, from perhaps 60% to 100% Throttle output. So, during a landing, the prop is usually serving as a speed brake; during a go-around, it is smoothly applying power. Nice ... so far. Or, I can simple flip Throttle Cut (Switch A) at any time to freeze the prop, e.g., during a glider landing where we want the prop to stop and fold before touchdown.

Next, comes the rest of the TOGA action:

 This Flight Mode couples the Flaps and Ailerons into the Throttle Stick to achieve variable Crow. NOTE: This is NOT the output of the Throttle Channel, just the Stick input to that channel; if you have the Throttle Cut applied, the motor is still disabled even while the stick is controlling  Crow. As the Throttle Stick is pulled back from, say, its half-way position, the Flaps progressively move down and the Alierons/Spoilerons rise. The result is Crow: A variably high Drag, decreased Lift configuration. All the while, you are still driving the aircraft normally, i.e., the Elevator has full control of Pitch.

 Those are the basics! How do you use it?

 So, as you swoop in for a landing or touch-and-go, you can go into TOGA Flight Mode at any time. As you pull back on the Throttle Stick, you are going to start dropping really quickly. Note: This may vary, depending upon the aircraft, e.g., on my sailplanes, I have to push Down Elevator quite a bit before they achieve the considerably reduced L/D while still holding low airspeed.

 Use your Elevator to maintain a suitable Pitch angle, play the Throttle/Crow as you wish. To abort the landing or simply touch-and-go, just nail the Throttle and the aircraft is automatically cleaned up and you are climbing. You can just leave the Flight Mode alone if you wish; provided you are flying at reasonably high Throttle, the Flaps and Ailerons mixing is no longer invoked - the aircraft cleans itself up and climbs out.

 If you do this, you lose nothing. You can, like me, still have available things like Elevator-to-Flaperon/Flap mixing, switch-selectable, whereby Up Elevator couples in some degree of Down Flap and Ailerons(Flaperons), enabling some wicked climb-outs or short take-offs from floats, or whatever else you have in mind.

 These radio systems have an incredible amount of capability. It is a bit intimidating. However, when you delve into it a bit, you will find that there is an awful lot of untapped Fun bottled up inside.

Aside: TOGA = Take Off / Go Around, a term familiar to those who fly bizjets, some airliners, etc. The idea is that a whole lot of stuff can/must happen quickly and precisely during a short and critical time when an aircraft will require a precisely altered configuration, power settings and resultant flying characteristics.
Last edited by Deerslayer; Oct 29, 2020 at 04:13 AM.

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