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| Saturday, March 7: | Aerobatic Judging Seminar, Livonia, MI |
| Sunday, March 8: | Precision Aerobatic Seminar, Livonia, MI |
| Sunday, March 8: | Flying Pilgrims R/C Club 5th Annual Swap Meet, Canton, MI |
| Wednesday, March 11: | Skymasters Meeting, Larson Middle School |
| Wednesday, March 25: | Skymasters Meeting, Larson Middle School |
| Friday-Sunday, April 3,4,5* | Toledo 98, Seagate Centre, Toledo, OH |
| Wednesday, April 8: | Skymasters Meeting, Larson Middle School |
| Saturday, April 18: | Bald Mountain Involvement Day, Bald Mountain Park Headquarters |
| Wednesday, April 22: | Skymasters Meeting, Larson Middle School |
Event information from mailings received, Model Aviation Events Calendar and Michigan RC Flying Times
Skymasters Events
This is our current list of events for 1998. Some changes have been made to avoid conflicts with other area clubs during the AMRCC meeting in early February.
April 18, 1998 Bald Mountain Involvement Day - Bald Mountain Park Headquarters. A great start to Spring. Come out and volunteer to help our park prepare for the summer season. There are light jobs, heavy jobs and everything in between. Steve Fredericks
May 16, 1998 Seven Lakes Spring Float Fly - Seven Lakes State Park, Holly. AMA. Our first Float Fly Event of the year. It adds a whole new dimension when flying from water - it's also great to watch. Chet Brady
May 17, 1998 Bald Mountain Float Fly - Bald Mountain Recreation Area, Trout Lake. AMA. The beach will be closed, and R/C float planes will take the place of bathers. Another fun day on a great float plane site. The Scripps Road Field will be closed for this event. Greg Cardillo
May 31, 1998 Chet Brady Memorial Mammoth Fly-In - Scripps Road Field. AMA. 80" span mono-planes and 60" span biplanes. Come and see the big planes. They are a great sight both on the ground and in the air. Bill Leppard
June 7, 1998 Kids Day - Scripps Road Field. Come and try R/C flying. Trainer aircraft and instructors will be available to guide the kids through a short flight of a real R/C aircraft. Carl Long
June 14, 1998 Harold Big H Maseles 4 Stroke and Majestic Flyers - Scripps Road Field. AMA. Anything with a four stroke or a majestic flyer - old timers, slow biplanes. Come and hear the fantastic sound of these miniature four stroke engines. Greg Cardillo
July 12, 1998 Team Fun Fly - Scripps Road Field. Lots of exciting flying events, lots of fun, and even some prizes. There are categories from mild (beginners on buddy cords) to wild (experts using purpose designed fun-fly airplanes. Need a teammate, we'll find one for you! Darrell Watts
July 19, 1998 Warbirds and Scale - Scripps Road Field. AMA. From P51s to Tiger Moths, Cesnas to Tomcats. There should be lots of variety in the air and on the ground. Pete Foss
August 8, 1998 (Saturday!) Multi Engine / Multi Wing - Scripps Road Field. AMA. Both multi wing and multi engine planes from biplanes to P38 Lightnings. The sound of twin engine model aircraft is superb, coupled with some expert flying makes for a very entertaining combination. Gary Walling
August 23, 1998 Corn Roast and Top Gun - Scripps Road Field. This is the club event of the year with our annual Top Gun pilot competition. A field full of aircraft and some great flying - a great day out for all club members, their families, and our neighbors. Joe Finkelstine
September 19-20, 1998 Midwest Regional Float Fly - Island Lake State Park, Brighton. AMA. This is the big one! Float flyers from all over the Midwest bring all sizes, shapes, and color of aircraft imaginable and fly them for two days solid. A blast! Flying starts at 9:30AM both days! Darrell Watts
December 27, 1998 Krazy Snow Fly -
Scripps Road Field. Come and give your planes and winter clothes an outing.
There's plenty of hot food and drinks, a fire, and some cool flying. The
more snow, the better! Steve Fredericks
FCC Rule Changes Take Effect 3/1/98
Effective 3/1/98, the rules governing our transmitters have changed to eliminate use of wideband equipment. All R/C transmitters in use on the 72 MHz or 50 MHz bands must meet one of the following criteria: * Have been manufactured to the narrow band standards within last few years. * Have been tested and/or modified to comply with the narrow band requirements as indicated by presence of a R/CMA Gold Sticker. Use of transmitters not meeting this requirement is illegal! Rules regarding the 53 MHz ham band have not changed. Note that while the FCC rule only affects transmitters, Skymasters Field rules have required the use of both narrow band transmitters and receivers for several years now on 72 and 50 MHz. Narrow band receivers can be identified by words 'Dual Conversion' used by most manufacturers, or 'ABC&W' used by JR. Please insure any old equipment you may have complies with these requirements.
If you have questions, please direct them to a member of the Board, or one of your AMA representatives.
Airfoils by Joe Finklestine
My experiences as one of the club’s instructors leads me to believe that a short course in airfoil and wing design might help explain some of the behavior of our flying marvels that still mystifies many of us.
First though, a few disclaimers
- I am not an aerospace engineer by training or profession, so I promise to keep the math and such to a minimum and instead focus on cause and effect. This will undoubtedly cause objections from the perfectionists reading this. This is not a treatise on aerodynamics, nor even a one minute guide. Detail will be mostly left out here. For those of you who do want to know the nitty gritty, I suggest the following books as starting points that I have read several times. Both of these books assume at least rudimentary algebra skills
- The illustrated guide to Aerodynamics by Hubert "Skip" Smith, tab books, ISBN 0-8306-2390-6
- One of the never-ending arguments in aviation has been the explanation of how a airfoil (wing) generates lift. Many long arguments on the internet (and in person) continue on this subject. One method uses the theories of a family member of the Bernoulli family, that says that conservation of energy provides a pressure differential that causes lift. The second body of thought argues that a momentum change in the air over the wing (air is pushed down, creating lift up) causes lift. I don’t know if you will believe me here, but both ways of looking at this are actually the same. My explanations of things here don’t depend on which version you believe (if it really matters to you!)
- I assure you that all of your planes will still fly as before if you choose not to pay attention to any of this! - Your plane doesn’t care if you think Bernoulli is an Italian bakery or a physicist. If , however, you have any interest in airplane design or why your plane flies the way it does, then read on.
- An explanation of just airfoils alone could be worse than nothing at all. The wing itself also must be talked about here, and a brief discussion on the "other" airfoils on your ship ( you know minor things like the tail feathers, prop, etc. ) - but this discussion will have to wait for Part II
Now lets start with a picture or two to define some key terms (Please forgive the primitive graphics, but I want to finish this in my lifetime!)
Key things to note here
- Chord length - This is the length of the airfoil (I’ll also refer to it as a rib). This is a key parameter as most rib coordinate data is stored independent of chord length, so that any length rib can be created from same data. Also, several other parameters of the rib are expressed as a percentage of chord length. Chord length is also most often stated as just chord.
- Chord Line - This line connects the front edge of the rib to the back edge point. This is also one of the lines that defines the angle of attack the airfoil is at when flying (the "earth" or "relative wind" line is the other and is assumed horizontal)
- Camber line - This line connects all points on the rib that are equally spaced between the upper and lower surfaces. Note that for a fully symmetrical rib the camber line lies exactly on the chord line.
- Thickness is usually defined at the widest point of the rib (which incidentally, is usually the spot where we put our spars). Typically, thickness of the rib is defined as a percentage of chord. We R/C’ers usually play with airfoils in the 10 % to 20% range.
- Fully Symmetrical
- Non symmetrical, or cambered airfoils
Cambered airfoils are not the same above and below the chord line, and generally are very easy to tell which is the up and down side. Cambered airfoils range from almost fully symmetrical (also often called semi-symmetrical) to highly cambered (a flat bottomed rib would be an example). Before I can discuss the merits and applicability’s of each airfoil type though, we need to digress a bit into what are key behaviors and properties of airfoils. These include pitching moment, lift coefficient, stall angle, and maximum lift. I am ignoring discussion on things like profile drag, Reynolds number, etc. These are also quite important for airfoil/airplane design, but not for this short overview.
Lift coefficient refers to an airfoil’s ability to provide lift in a quantitative(i.e. measurable) way. Lift coefficient(often abbreviated CL) depends upon several things including wing aspect ratio, speed of airfoil in the air, angle of attack , effective air density, etc. CL is most useful because it can be used to compare different airfoils when applied properly. When charts of an airfoil’s lift coefficient are made, typically all things are held constant other than the angle of attack, which leads to a convenient chart, that can be used to make "apples to apples" comparisons. Angle of Attack (AOA) is the angle between the relative wind (think of it as always horizontal for us RC’ers) moving over the airfoil the chord line of the airfoil. Look at the charts below.
Looking at the above chart, several interesting things can be seen. First , for the symmetrical airfoil, the positive lift and negative lift are equal (i.e. the airfoil produces the same "negative" lift as positive). Also of note here is that the symmetrical airfoil produces zero lift at zero angle of attack, the maximum value of CL is lower than for a cambered airfoil, and that the lift curve "falls off" quicker than the cambered airfoil - I’ll explain why this is all relevant in a moment.
The cambered airfoil has a few interesting traits as well. First, it is not symmetrical in lift - it produces more lift in the positive than negative mode. In addition generally, a cambered airfoil will begin producing lift even at negative angles of attack. Finally, the cambered airfoil has a usual greater maximum lift coefficient, and that its "fall off" at maximum lift is a broader curve than a symmetrical airfoil.
Incidentally, the "fall off" in both curves correspond to the airfoil stalling - notice that no mention of airspeed in this curve - You can stall an airfoil at any airspeed, which is a foreign concept to most new students, as we usually tell all of our students not to stall the airfoil by slowing too much. - More about stalling later though when I bore you in Part II about wings! So, why are these things important??
The symmetrical airfoil lends itself well to the aerobatic ship. The symmetrical lift is helpful to allow the ship to fly as easily inverted as normally. The sharp drop off in lift at stall angle allows for crisp snap rolls (The leading edge has much to do with this as well!). Also, while not apparent in the above chart, the symmetrical airfoil has the smallest pitching moment, particularly at or near stall. This helps the aerobatic ship turn and tumble in all directions, rather than favoring one. There are several other design factors which allow the aerobatic ship to do its thing, including wing size, span, CG location, tail feather moment, etc. Collectively, these factors have more effect on the ship than just symmetrical airfoils, but the symmetrical airfoil is the first enabler of a slippery design.
There are disadvantages to the symmetrical airfoil (Most aircraft design is an exercise in compromise between competing design requirements!). Two key disadvantages for us RC’ers include the relative inefficiency of the airfoil, and the difficulty in building up a wing panel. Looking back at the lift chart, remember that the lift coefficient’s for the symmetrical airfoil lagged the cambered airfoil at all angles of attack. This means that we must either go faster, build a bigger wing, or fly at higher angles of attack to generate needed lift. This is one reason you usually see the aerobatic ships landing at higher speeds than the trainers (except for me, who just keeps the power on too damn long!). The symmetrical airfoil will demand more of the pilot, but rewards good piloting skills with authoritative flying. Symmetrical airfoils also are a challenge to build up into a straight warp free wing. Since there is no flat bottom to lay the ribs on when building, a separate method to keep the ribs (and wing panel ) square must be used when building up the panel. This shows up as break off tabs on the ribs, pinning square stock underneath, use of a building jig, etc. This is not much of a problem for experienced builders, but it does allow room for error!
The cambered airfoil favors both trainers and high lift slow flying ships. The cambered airfoil has more lift for a given angle of attack, so that slower flying speeds are possible. The cambered airfoil also has a gentler fall off near stall, so that the stall is typically a gentle one. The airfoils low negative lift shows up typically when you try to fly a trainer inverted, which often requires much nose down stick to fly level (this is not the only reason, as trainers are often designed to "right" themselves when displaced from straight and level flight - more on that one in part II as well). The cambered airfoil can lend itself to an easier build up, as several cambered airfoils have a flat bottom. (I believe the Clark -Y is one example). Many full scale smaller general aviation airfoils are cambered ( not talking about aerobatic full size) for the same reasons of stability and efficiency. High cambered design also allows for a very high lift wing to be designed, allowing for a big load to be carried. Disadvantages of the cambered airfoil include the tendency of all cambered airfoils to have a strong pitching moment near stall and the higher (than a symmetrical airfoil) amount of drag at a given airspeed.
Each airfoil has its place and we, as pilot, owner, and designer (sometimes) have a tremendous range of airfoils at our disposal. To every airfoil a plane evolves!
Bald Mountain Involvement Day
Our annual Bald Mountain Involvement Day is fast approaching! This year it is scheduled for Saturday, April 18th. Plan now to attend this event. The importance of this event for the club cannot be overstated! This is our opportunity to give back to the park for all the support we have received. There is something for everyone to do. Past projects have ranged from painting signs and trash barrels, to building a dock and a bridge with everything in between! The club provides lunch for all, so please come join us. Families are welcome! We are looking for a few people to meet ahead of time to coordinate the efforts. Contact Steve Fredericks if you would like to help coordinate our activities!
Contractor Opportunity
Warmer weather is just around the corner and so is the need for field maintenance. The Skymasters are currently taking bids for lawn service at our field for the 1998 season. If you or a family member are looking for this kind of seasonal work let us know about it. We always like the chance to offer these opportunities to members and their families first. We are looking for a contractual arrangement for keeping the grass cut at our field. This arrangement can also include using the club tractor for adult Skymasters members. If this sounds interesting to you or some one you know please call Gary Weaks for more information.
Skymasters Information
Skymasters field is located within the Bald Mountain State Park (see map). State Park Permits are required and can be obtained from the Park Headquarters located on Greenshield Road or at club events. Flying is permitted from 10 AM to 8 PM. The noise limit for 1998 is 95dB at 10 feet - this noise rule is strictly enforced.
Wednesday evenings during the summer is Student Night and there are usually instructors around all afternoon. Student night is also 'pot luck' buffet night so that you can fly-n-feed (though not usually at the same time). Students are encouraged on other days and weekends. It is a great idea to come on Wednesday, meet the Instructors and arrange for more instruction time together. Our Chief Flight Instructor is Pete Foss. Assistant Chief Flight Instructor is Graham Overton.
From June to August, Club Meetings are held at the field on the first Saturday of the month at 12 Noon - a great chance to fly and gossip too! Winter meetings (September to May) are held at Larson Middle School (on Long Lake just east of John R - see map) on the second and fourth Wednesday of the month at 7:30 PM. Show and Tell, coffee and donuts, and model-speak are the order of the evening. Come along - they are fun.
The Skywriter newsletter is sent to all members, local hobby shops and other local R/C clubs. Any and all contributions are welcome, please pass any articles to the Editor. If you know of anyone who may be interested in our hobby (friend, relative, neighbor, colleague or acquaintance) - please give them a copy of this newsletter or a copy of an AMA magazine - it may spark their interest and get them into our hobby!
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