FlightplanPublished "online" by the Flightmasters
Model Aircraft Club, Inc. of Fort Smith, Arkansas. It's purpose is to inform
the membership and to promote interest in the safe building and flying of model aircraft both in
the Fort Smith Area as well as elsewhere. |
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Volume 43 Number 5 AMA Charter # 742 IMAA Chapter # 362 May 2010 |
- Editor's Corner -by Cecil Collum
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... from the president's perspectiveby Ron RobertsThe month of April and so far this May has been pretty rough months… at least for me. No flying since the 7th of April! I had Rotator Cuff surgery on my right shoulder the morning of the 13th of April, missed the Club Picnic on the 17th and have been pretty much limited in what I can do since. Rodney Darling had this same kind of surgery a couple of years ago or so, and told me about what to expect. It's been pretty much as he said. I mentioned last month that there was another piece of property in the Chaffee Crossing area, more-or-less adjacent to the plot that we were looking at, until we found all the water. That piece is higher and was not under water when the other was, and it has fewer trees! We spoke with Ivy Owen and Larry Evans, the folks at FCRA and Chaffee Crossing, and they think we may be able to get this plot instead of the one we have been looking at. We have received permission to drive and ride 4-wheelers over it and measure and place stakes, then they can tell exactly what we need. Tom Minton and I will do that Saturday morning, the 8th of May and may be able to report some good news at the May 16th Special Meeting. In the mean time, we are still looking at property in the Roland, Oklahoma area. We have asked Carl Albertson, who knows just about everyone over there, to help us and he has contacted a few people. Things look pretty good for being provided a place to fly over there. These properties, at least for now, appear to be similar to the Stephens property on which we now fly - that is, they will not deed it over to us, but will let us use it for "next to nothing" as long as we keep it clean and nice and not damage the surrounding crops. My own opinion is that if we can be deeded land from the Chaffee Area, I would rather have that because it would be ours. However it may be necessary to procure a "short-term" place while negotiations are on-going with the FCRA, and if that is so, then the Oklahoma land may be nice. Hope to see everyone at the field on Sunday afternoon, the 16th of May. That is two weeks before our Jumbo, so we will have some work to do. Also… Saturday, the 22nd of May, is the day for the ABF "Family Day". They have a covered place (ground floor of the parking garage) and are going to provide tables, chairs and food for 10 of us to show off our airplanes with a static display. There will be a model railroad display set up that I'm told is great! We will also finalize this at the meeting on the 16th. Till next time… Ron | ||||||||||||||||||||||||||||||||||
- Batteries and Charging (Part 2) -by Cecil Collum The following segment is the second of two parts on charging the batteries we use to fly and control our models. There are many ramifications to properly charging and storing these wonders of the electronic age and can cause damage to our planes, vehicles and homes if not properly done. I claim no special knowledge, the following is an amalgamation of knowledge found on the web and is presented for your pleasure. | ||||||||||||||||||||||||||||||||||
In Part One, we discussed the three most common types of batteries used by modelers, those being Nickel Cadmium (NiCd), Nickel Metal Hydride (NiMH) and Lithium Polymer (Lipo). We also discussed the basics of charging Nicds and NiMHs. Now let's talk about charging Lipos since these are the most critical batteries, safety wise, that we commonly use. Some manufacturers now supply the batteries “unfinished” from the factory, meaning that they have mixed the chemicals and filled the cells but the cells have NOT been charged. The first several charges are critical to the capacity and life of the battery, as the molecular structure of the battery is aligned during these charges. It's best that the first few charges be done slowly, about 1/10C and taking around 12 hours, more or less. Many chargers have a “charge-discharge” cycle that one can choose which automatically charges the battery, lets it cool and then discharges it, cools it, etc. Some cyclers let you select the number of cycle and charge/discharge rates to suit the battery being cycled. Many don't have the feature allowing one to select the number of cycle, however. Charging Lipos: Lipo batteries MUST be charged correctly or they can explode and set fire to your house, car or workshop! One CANNOT use a charger designed for NiCds or NiMHs! The charger MUST be designed for Lipo batteries! Having said that, Don Jones has shot them and done many other things we have been cautioned against, without any untoward effect. He did, however, charge one at too high a setting and it did burn! He had the battery in a fire-proof container so he didn't suffer any damage other than to the battery. Lipos should be charged at about 0.6C to 1.0C. Charging them too slowly can cause a problem with the chemistry - the innards are actually semi-liquid and metal salts can form if they are charged too slowly. This will drastically shorten their life while charging them at greater than 1C can heat them up and cause them to swell. Continuing to charge them after they begin to swell will cause a very hot chemical fire that will continue to burn even under water! For this reason, any Lipo that has swollen or been deformed by crash damage or over-charging should not be used again. After a Lipo suffers crash damage you should keep them away from anything else but where you can still keep an eye on them for al least an hour. Chemical reactions can occur for some time after a crash, causing the same nasty fire. I don't mean to give the impression that Lipos are extremely dangerous - when correctly charged and monitored for damage, they are safe, it's just that the potential consequences are very severe. Many use “battery bags” or vaults for safety-boxes of fireproof material and sealed so that if the worst happens the damage is localized. Personally, I place my Lipo in a metal ammunition can and place it several feet from my shop door where I can check it every few minutes until charged. One new thing that that crops up with Lipos is “balancing” - no, not as in finding the Center of Gravity, but as in "balancing the charge" in each cell. Many Lipo chargers and batteries utilize a “balancing lead” by which the battery is connected to the charging. The balancing lead has a small multi-pin connector with as many pins as cells in the pack plus one. This connector is used by the charger to measure the voltage of each cell in the pack and to feed in a small extra bit into a single cell so that any that are charging slower than the others will be topped off and balanced. Every cell in the pack will have the same voltage by the end of the cycle. Balance charging is slower than than normal charging so it's not necessary to do more often than every fourth or fifth charge. Another option you may have is just “balance”, not "balance charge". This just discharges individual cells so they all match rather than topping them off. There are a few different types of balancing connectors - chargers often come with small converter boards so one can balance packs with various connectors. Chargers will also have a range of pack sizes (1-6 cells) they can accommodate and a range of balancing connectors to suit with the appropriate number of pins (cells +1). | Lipo cells have no memory effect so they can be charged at any point in the discharge cycle. There is no need to discharge them completely first to a minimum voltage prior to charging as with NiCds. The charger will stop when they are fully charged and will show the amount of charge it squeezed into the pack, in milliamps, naturally. This tells you how much the last flight drained from the pack so you know how much energy is left and just how far you can push it next time. There is no “delta-V” voltage dip with Lipos, so the charger has to monitor the cell voltages. The balance connector is used for this so many chargers insist that the balance connector is plugged in while charging, even if you are not explicitly balancing the pack. Lipo cells give a nominal 3.7 volts per cell and should never be discharged below 3.0 V per cell or you risk a fire. In most cases, Lipos are used with Electronic Speed Controls (ESC) or Battery Eliminator Circuits (BECs) which have a programmable cut-off level, usually factory set to 3.3V so that should circumvent any problems with tasking them below the cut-off voltage. When the cut-off voltage is reached, the receiver is still powered but the motor is either cut off or only given access to maybe 20% power - just enough to get to the scene of the crash! Seriously, at that point, there is enough for one to land the plane safely. Lipos are fully charged at 4.2 volts per cell and should NEVER be charged above 4.25 volts per cell or - guess what? - FIRE! That is why you MUST use a charger designed for Lipos and nothing else. Another figure used with Lipos is the confusing “C” rating. This tells us the maximum discharge rate a pack can deliver - 20C is common (20 Amps for a 1000 mAh pack). Some newer packs have a normal and “burst” rating of 30C and can deliver more for a very short time than they can for a long flight. These are typically used for electric gliders that need most of the power in a few short, intense bursts. Some older and cheaper packs may be available with C ratings as low as 10C but should be avoided as most well sized power set-ups for aircraft require more than they can deliver. The final thing to be careful of is storage. The actual capacity of a Lipo is dependent on the temperature. If you fully charge a pack when the weather is cold then leave it in the car on a sunny day, it can actually become overcharged and you know what that means - FIRE! For that reason it is recommended to store packs at about 60% of charge. This will be safe with almost any likely temperature rise and it will be unlikely to self-discharge to a dangerous level. Lipos discharge much slower than NiCds and NiMHs so stored Lipos only need topping back to the storage level of 3.8 to 4.0 volts every six months or so. Many Lipo chargers have a “Storage” setting which charges or discharges the cells as required to reach the correct storage charge level. SUMMARY: So, is that all you need to know? Well, you need to use the correct charger for the type of battery being charged. This is normally just better for the battery but downright necessary with Lipos to prevent - you guessed it - FIRE! Chargers will normally have sensible default settings, but if you must set them your self, this is the consensus: NiCd
NiMH
LIPO
Thus endth BATTERIES and CHARGING. I hope it contained useful information and that each of you have learned a bit from it. If you like this type of article, please tell me. If you want something else, please tell me. | |||||||||||||||||||||||||||||||||
UPCOMING EVENTS
The following events have been scheduled by the Flightmasters or other organizations. Mark your calendars so
you don't miss any of them. Checking the Event Listing, there will be quite a bit of activity in the western
half of Arkansas this year. Get out there and enjoy all the events you can, even if you have to drive 150 or
so miles. I plan to attend the Petit Jean, SMALL, CAMAA and MARCS Float Fly this year and renew my friendships
with many of the pilots from Central Arkansas. These fellows will make you feel at home even though you may
be a complete stranger when you arrive. You won't be a stranger when you depart and you will have made friends
from other parts of the state and learned how others solve the same problems we all have. To the writer, this
is the most important part of our sport.
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23 & 24 |
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Meeting Notes from last meeting:
The April meeting was on 11 April at the field. President Roberts called the meeting to order with 21 members and 2 guests present. The Minutes of the March meeting were read and approved. The Treasurer's Report was read and approved.
Under Old Business, Ron updated us on the New Field Project. As many are aware, the proposed site at Chaffee Crossing is under water with a beaver dam causing problems. The Committee will propose to the FCRA that we select a piece of property southwest of the current site. This site has fewer trees and no beaver dams and is about 10-12 feet higher in elevation. Should the FCRA concur and we gain ownership of this new site, less work to construct an airfield will be required and it will be available at an earlier date than the current site could be. More to follow...
FMAC has attained Gold Leader Club status in the AMA, which signifies that we are involved in civic activities within the community. The only other Gold Leader Club in the state that the editor is aware of the Mid Arkansas Radio Control Society in Little Rock.
Under New Business, PD Duvall, who along with his partner Carl Gross, sponsored the Gun Show in the Phoenix Expo a couple of months ago, approached the club about participating in a Hobby Show in the November time frame.
The Douglas SBD Dauntless (Scout Bomber, Douglas) was one of the most influential aircraft of World War II.
The airplane was designed at the Douglas Aircraft Plant in California in mid 1930 and it soldiered on as even
more sophisticated aircraft came on board, some designed to replace this tough old bird.
Despite it's classification and appearance, the SBD could more than handle it's own against the lightly armored Japanese aircraft in the Theater. The SBD would build for itself a history of resilience despite it's inherent limitations of design - a history that very few aircraft of the war would be able to match - and be responsible for sinking thousands of tons of Japanese shipping, along with thousands of Japanese soldiers, sailors and airmen.
The design of the SBD was conventional with the large radial engine mounted in the nose of the aircraft just forward of the cockpit. The glazed cockpit accommodated two crewmen, the pilot forward and a gunner/radioman, aft seated back to back. The rear cockpit contained a flex-mounted .30 caliber machine gun which played a major defensive role, saving many a crew and airplane.
The pilot was also the
bombardier and he also had two forward-firing .50 caliber machine guns in the nose of the plane. The wings were
in the low monoplane position and featured the noticeably large perforated dive flaps that was to mark the
series. The tail feathers were a traditional assembly with a single large vertical fin and rudder. The
real meat and potatoes for the SBD was her ability to carry a substantial bomb load that could be supplanted by depth
charges if necessary. The SBD could carry a total of 2,250 pounds of external ordnance.
The SBD's capabilities were adequate for her type with power supplied by the single Wright R-1820 series air cooled radial engine rated at more than 1,000 HP and achieving better rates as new engines became available throughout the production period. Top speeds of 250 mph could be attained with a ceiling of around 25,500 feet and a range of more than 1,000 miles. At first glance, the specs may have left a bit to be desired in the design but she was soon proven to be a steady performer even when called upon to battle the fabled Japanese Zero fighter. Japanese fighters, even though fast and agile, were very lightly armored and offered a fair fight to the equally powerful SBD. The Dauntless would earn itself many an air kill by war's end thanks to the skill, bravery and determination of her crews, and deficiencies in the design of Japanese aircraft.
The SBD was designed by Douglas shortly after absorption of the Northrop Corporation and was designed in response for a new Navy dive bomber proposal. The XBT-1 was the product of this development and led to limited production of BT-1s. This was followed by a new re-designated XSBD-1 series featuring improvements to flying surfaces and landing gear and entered official production with the more identifiable “SBD” designation in the initial SBD-1 models.
Early versions featured a
weak configuration of two forward firing fixed .30 caliber machine guns and a a single flexible mounted .30 caliber gun
in the rear cockpit. The SBD-2 appeared shortly after with an increased fuel capacity. The SBD-3 gave crew
members a bullet-proof front windscreen, self-sealing fuel tanks and more armor protection. Armament was also
revised and improved to the series standard of two .50 caliber forward fixed and two .30 caliber flexible Mgs in the
flexible mount. The SBD-3 also introduced the Wright R-1820-52 engine and even better fuel capacity. The
definitive SBD arrived in the SBD-5 model with the more powerful 1820-60 series engine with an increase in total
ammunition and more than 3,000 examples were produced.
The SBD was also produced in a photo-recon version, designated with the appropriate “P” such as SBD-1P, etc. The Navy and marine SBD-3, 4, and 5 also formed the basis for the US Army's acquisition of the type as the A-24 “Banshee” thought these proved far less successful. The British Fleet Air Arm took delivery of at least nine SBD-5 models, designating them as Dauntless DB. Mk 1 series. These reportedly never saw action.
The Dauntless's introduction to combat immediately after 7 December, serving primarily on the aircraft carriers Hornet, Yorktown and Enterprise, among the most notable. The most notable action they saw early in the war was at Guadalcanal flying as part of the Cactus Air Force and on 4 June 1942 at the Battle of Midway, in which SBD crews destroyed the Akagi, Kaga, Soryu and Hiryu carriers of the Imperial Japanese Navy in a space of five minutes. These four carriers had participated in the attack on Pearl Harbor six months previously, giving the SBD crews great joy and revenge. Many SBD crews perished in this battle, fought at maximum range from their carriers.
The story of the Battle of Midway contains many heart-wrenching tales of courage, devotion to duty and plain old guts that cause one to wonder how that generation produced such giants. Two Torpedo Squadrons were totally destroyed in attacking the IJN carriers, with only one man of 62 surviving. Ensign George Gay, of Oklahoma City, was flying tail-end Charlie of his squadron and saw all their planes crash into the sea before he was shot down. He escaped his sinking plane and watched the ensuing battle from within the IJN screen. The loss of the 31 aircraft had a sliver lining in that the torpedo planes pulled down to sea level the entire Japanese Combat Air Patrol, leaving a clear path for Old "Slow But Deadly" to launch three squadrons of dive-bombers on their deadly dive. Within five minutes they turned the Akagi, Kaga and Soryu into flaming wrecks. Within three hours they flamed the Hiryu, ending the battle with a resounding success against all odds.
The Battle of Guadalcanal continued for six months and was in doubt much of that time and without the Cactus Air Force,
a conglomeration of Navy, Marine and Army Air Force aircraft, it is doubtful that the Marine and Army units on the island
would have prevailed. The contribution made by the fliers was of inestimable value to the ground commander and many
decorations were won during this six month period. Old “Slow But Deadly” was supposed to be replaced by the Curtiss
SB2C “Helldiver” but problems with the new plane kept the SBD in service till war's end.
One interesting feature of the SBD is that it did not have folding wings. The engineers who designed the plane held out for non-folding wings in order to make the wing as strong as possible due to the stresses incurred in the diving attack. It was one of the last planes with non-folding wings in the US Navy. During the Battle of Leyte Gulf, the SBDs flown off the escort carriers of Taffy Five prevented the destruction of the landing forces invading the island of Luzon by harassing and sinking several IJN ships of the two strike forces, including the Yamato, while a decoy force lured Admiral Halsey away to the north with his Fleet carriers and battleships.
The SBD continued to serve to war's end but was obsoleted out as quickly as possible. She was just too slow and dive bombing was rapidly losing favor as an attack option. The old SBD would soon be replaced with the flashy new jet aircraft the Navy favored but she was never replaced in the hearts and minds of her crews. Few aircraft have served a country as well as Old Slow But Deadly. But for the SBD on 4 June 1942, we may now be speaking Japanese!
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