The Marin Aero Club (M.A.C.) comprises a group of fliers who meet regularly to fly model aeroplanes powered by rubber, electric or CO2. Indoor events are held monthly year round, and also outdoors in the summer. The group is very informal as we have no officers or dues and stress that it is more important to have a good time rather than put up a good time. As the M.A.C. has been in existence since about 1948 (in Marin County, just north of San Francisco) it has certainly met a local need.
This is a guideline to those returning or beginning to build and fly balsa wood and tissue covered model planes. It is not intended to be a comprehensive source of instruction, but instead to familiarize one with some of the concepts of building and flying these delightful models. It is also aimed at the M.A.C. situation with access to a gymnasium and an outdoor field. Because the outdoor field is small, we generally fly planes of around 24" maximum span to minimize lost or damaged planes. Scale and non scale models are flown. Gasoline engines or fuse type dethermalizers are not permitted due to fire hazards and noise.
M.A.C. members welcome you and are very happy to assist you with guidance as required. Events and schedule are available on other pages.
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- "Building and Flying Indoor Model Aeroplanes" by Ron Williams is an excellent book and well worth reading. Dedicated to lightweight duration models this book will teach you many lessons valuable to any type of models. Long out of print, this wonderful volume is now available again. The 1984 second edition has been reprinted (ISBN 978-0-615-20203-7), and is available from www.indoormodelairplanes.com for $24.95 plus shipping and handling.
- "Rubber Powered Model Aeroplanes" by Don Ross. About $15. A good overall guide to building and flying a wide range of models. Don has also published a followup volume, "Flying Models, Rubber, CO2, Electric & Micro Radio Control".
- "Hey Kid Ya Wanna Build A Model Aeroplane?" by Bill Warner. A detailed guide to building, trimming and flying two simple rubber powered models available as kits. Two other books follow in the series and cover the Sky Bunny and Flying Aces Moth. While now out of print, they are sometimes seen in local libraries. Volare Products also offers a bound reprint of this series as well as Don Ross's book. www.volareproducts.com
- Peanuts and Pistachios - These six delightful volumes from Bill Hannan have inspired countless thousands of modelers. Upon his retirement, Hannan thankfully
passed them along to www.plansandthings.com where they remain available. These excellent books emphasize "Peanut" scale models spanning 13 inches, as well as unique full scale aircraft to further inspire us.
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- We suggest starting with a very simple precut model such as the Sleek Streak sheet balsa model available in hobby shops, toy stores and larger drug stores. This provides a good way to learn the rudiments of trimming to control turning and climbing and the effects of changes in rubber size. Surprising performance can be had with these simple models.
Next in complexity is a stick model with a built up balsa stick and tissue covered wing and tail. This substantially increases flying time over the preceding sheet models. Many designs are available. The Peck R.O.G. (Rise Off Ground) is covered in Bill Warner's first book and is available as a kit from Peck. A similar model is the Jetco ROG. Click for online plans.
The next step up is to build a model with a built up fuselage instead of a "stick" fuselage. We cannot emphasize too strongly that it is too early to build a scale model as these are trickier to build, harder to fly, more vulnerable to damage and could be very discouraging, whereas we can (almost !!!) guarantee success if your first built up fuselage model is a "Pussycat". Although only 12" wing span, if built lightly it can fly for over a minute in the gymnasium and can fly "Out Of Sight" outdoors.
After the Pussycat is satisfactorily built and flown, we advise building a Bostonian class model. This is a 16" span model in a wide range of designs (ask for plans) resembling full size planes but with proportions better suited to easy trimming and stable flying.
Selection of your first scale model design is very important to avoid discouragement as many full size planes make very poor flying scale models. As a general guide, select a high wing monoplane with a long nose (for better balance) and a minimum of struts and complex landing gear. Planes such as the Nesmith Cougar, Lacey, Fike or early Cessnas can be built from plans or kits.
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Many local hobby shops carry a range of supplies suitable for our needs. If you can't find it near home, consider these sources listed below.
Easy Built Models makes a wide range of older design, mostly scale planes. Kits are inexpensive, light weight, and fly well. Their laser cut Piper Cub and Stinson Reliant Peanuts fly well and are easy to build. www.easybuiltmodels.com
- Peck Polymers, P.O. Box 1284, Madison, CT 06443 USA. Peck Polymers offers kits, plans, balsa, tissue, props, wheels, wire, bearings and more. Pecks also has the hard to find pin clamps, to help hold pieces in place while gluing. www.peck-polymers.com
- Retro RC offers a nice selection of Free Flight and Control Line models as well as their Radio Control fare. They also have some nifty teflon thrust washers, numerous building fixtures, and other workshop goodies to help make your life easier. Don't miss their fantastic wallets, printed with aviation-themed images. www.retrorc.us.com
- Volare Products also offers a wide range of Free Flight supplies, including the fabulous machine cut true pitch balsa wood prop blanks previously made by Superior Props.In addition to all the normal supplies we need, balsa, tissue, winders, rubber, etc, they also offer Costa Rican coffee to help you focus during those long "night before the contest" sessions at the building board. www.volareproducts.com
These suppliers all carry selections of indoor materials and some specialized outdoor supplies, as well as plans and kits.
- Micro Mark, 800-225-1066. A good source of modeling tools. Knives, blades small drills, burrs, clamps, Dremel, etc.
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Materials and Techniques
- Balsa Wood: Long the traditional material for building models, balsa wood is a huge topic that can only be touched upon here. Take a moment to look at the rack of balsa while first browsing your local hobby shop. Selecting wood can be a real science, but for now, notice that some sheets of wood seem much lighter in color, and weight, than others. Hold a few sheets of 1/32" or 1/16" up to a light, and notice the different grain and color banding that can occur. All of these variations help indicate weight and strength. They will become more meaningful as you build models. Balsa can vary in weight from under 4 lbs per cu. ft. to over 20 lbs, a variation of 5:1. Obviously if weight is important, and it is, care must be made to choose wood that is strong enough for the job, but not too heavy. If you want, buy a couple of sheets of 1/32", 1/16" and 1/8" balsa. Try to choose ones that are in between the extremes of weight available. It isn't critical for now, but a little care will help.
Glues: An often debated subject. For gluing balsa some use balsa cement, others use white P.V.A. glue and some use CyA. (Krazy Glue, Hot Stuff, Zap, etc). The CyA is potentially dangerous as it instantly sticks fingers together and is hazardous around the eyes. NOT recommended for juniors or the clumsy! However, if CyA is used, the odorless is preferable as, although more expensive, it does not irritate the nose and also is compatible with blue foam, discussed later.
Glues should be applied sparingly. Use only enough so the joint is as strong as the wood. Additional glue only adds extra weight. One method is to take a piece of modeling clay about half a golf ball in size and flatten it with a depression in the center. Place a disc of waxed paper on the clay and press it down. Pour a little glue on the wax paper and apply the glue to the balsa with a toothpick or a piece of thin Teflon tubing available from hobby stores.
Glue sticks, e.g., Ross Purple Stick, UHU Glue Stick, Kidstick, can be used to adhere paper letters or numbers to tissue. The peelable, non-permanent glue stick is used where separation is later required such as applying a printed pattern for wing ribs or formers to balsa sheet as a template. After cutting out the rib, the paper can easily be removed. Brands available include Avery Removable Glue Stic, Dennison Tack a Note, Post-It Restickable Glue Stick.
Tissue can be attached to the balsa structure by applying a clear liquid glue gel with a small brush to the balsa. Apply the tissue and smooth down with a finger. If necessary, thin in the bottle with rubbing alcohol or water. Brands include UHU, liquid Glue Pen, Roll'n Glue, O'Glue, Dab'n Glue. Do not confuse with solid glue sticks.
Tissue: Use only Japanese tissue and not domestic tissue. Japanese tissue is stronger, lighter and colors do not run when wet. Trim tissue after covering with a new sharp double edged razor blade, cut in half. Careful dissection of a disposable razor can also yield a suitable blade, but please be careful!
Doping is rarely used for our small models as it adds unnecessary weight, can add to the warping problem and we don't usually need the water resistance it provides. Tissue can be lightly shrunk with a thin mist of rubbing alcohol, applied with a spray atomizer. Many light weight models are best covered with tissue which is preshrunk.
To preshrink tissue, a partial sheet of tissue is taped with masking tape around the perimeter, to a picture frame or over a hole cut in a corrugated cardboard box.
A better frame is made from a piece of Masonite. With a saber saw, cut a hole in the center about 1" smaller in length and width than half a tissue sheet. (Hole is about 17" x 11"). Place the Masonite smooth side up with the loose center in place on a flat surface, rest the tissue on top and tape down the tissue around the outside. Lift up the Masonite, (leaving the loose center behind) support at one or both ends, mist with rubbing alcohol and let dry. Repeat several times. The Masonite loose center piece supports the tissue and minimizes wrinkles while taping down.
When tissuing the model, apply in small pieces, and run the tissue grain direction in the long dimension of wings, fuselage, stabilizer. Japanese tissue tears more readily in the grain direction so it is easy to establish grain direction.
- Music Wire: For our purposes, a selection of music wire from .031" down to .015" or even .010" is required. .031" or .025" is used for propeller shafts with .025" to .015" for landing gear. Each increase in wire size doubles the wire weight, so be sure you need the larger size as you build.
- Aluminum Tubing: Tubing is available in 12" lengths. Use 1/16" O.D. for rear motor pegs on Peanuts and Bostonians and 3/32" or 1/8" for larger models.
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Cutting: For cutting, use single edge razor blades and/or an Exacto knife with No. 11 blades. Keep sharp and replace blades regularly. A plastic cutting pad is a very useful luxury (about $15 when on sale at Micro Mark) minimizing dull blades.
Building Board: A piece of Cellotex or similar wood fiber ceiling material about 12" x 24" from building suppliers makes a good board for construction.
Hold Down Pins: T pins are available from hobby stores and Peck for building purposes. These are used to position balsa prior to gluing. Do not push pins through the wood. Pin clamps are plastic "discs" which slide tightly on to T pins to hold down wood to the building board. Pin clamps are available from Peck Polymers, www.peck-polymers.com. Scraps of balsa can also be used.
Craft stores sell long T pins (2" compared to the standard 1" T pin) which are useful to position fuselage sides on to the building board when joining together. A couple of metal blocks about 2"x2"x3" can be used to hold and square up body sides in conjunction with long T pins.
Tweezers & Pliers: Tweezers are used often for positioning bits of wood while building. Try finding a pair of "stamp" tweezers with a broad flat blade. This will help prevent crushing the soft wood.
A small selection of pliers for wire bending is necessary. Needle nose are very useful, as are a good pair of round-nose pliers. These are most useful for prop hooks, and can be tough to find. A good pair of diagonal cutters will be appreciated as music wire can be very hard. Cheap cutters will soon develop notches in the blades.
Sandpaper: This should be the most used tool, perhaps after a sharp cutting blade. Make sure to get a good selection from 100-320 grits. It lasts a long time on balsa wood, and will really make a difference in the quality of your work. Empty oval glue bottles are handy to wrap sandpaper around for shaping concave edges, e.g., wing tips.
Clamps: Miniature toy clothes pins about 1" long are handy to clamp wood when gluing. Also scraps of balsa can be used with a pin to hold down pieces. A selection blocks is also handy for positioning pieces as the models become more 3 dimensional. I often use small transparent plastic boxes filled with pennies.
Dremel tools are a luxury but good for wheel and spinner sanding. They are also used for cutting heavier music wire. A good selection of bits will be appreciated if you make this investment.
Drill Bit Sets: Sizes from No. 61 (.039") to No. 80 (.0135") are useful, and become necessary for drilling aluminum prop bearings on stick models and Nocals. About $15 on sale from Micro Mark. A small pin vise or Dremel is needed to use with these drill bits.
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Propellers & Bearings
Plastic props are very efficient and available in a wide range of sizes from 4" to 9" or more. For Peanuts, Bostonians and Dime Scale (16" span) 5" or 6" are customary.
Plastic nose bearings which fit into a 1/8" or 1/4" hole in the nose block are available and small glass beads about 1/16" diameter are used between the prop and nose bearing. For Nocal and stick models, make a bearing from .030" - .035" aluminum, about 1/8" wide.
Indoor Lightweight Props
For lightweight stick models, Nocals, Seattle 6, etc. a lightweight prop can be built as follows:
- Hubs: Usually made of hard1/8" or 3/32" square balsa, to which blades are glued. A clean ball point pen reservoir can also be used. Insert dowels, bamboo, & toothpick for a snug fit. Blades are glued to dowel. This provides pitch & adjustment.
- Blades: Using a thin foam disposable cup (not the 3/32" to 1/8" thick expanded bead type), lay your blade template on the cup as shown, cut out and glue (odorless C.A., or white glue) to hubs.
Alternatively, 1/32" or 1/20" balsa can be soaked in water, then positioned onto a can or bottle about 3" diameter at 15 degrees off the vertical axis. Wrap with porous cloth (bandage?) to allow moisture to evaporate, and when dry (overnight), remove and glue to hub.
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Rubber and Winding
Rubber: F.A.I. Tan Super Sport is the most popular rubber, and available in widths of 1/16", 3/32", 1/8" and 1/4". Peanuts and Bostonians use widths of around 3/32" or 1/8". Determination of the "best" rubber size is an acquired skill but more experienced modelers or the books listed earlier will help.
Rubber strippers are available ($100+) to strip 1/4" rubber into any width. These are certainly a "luxury" tool which can well wait until the modeling bug really bites. Many experienced modelers have them and can be quite generous with their use at a flying session.
Rubber lubrication is important. Use Armor All, Son-of-a-Gun vinyl restorer or Sil-Glyde silicone grease from auto parts stores. Tie the rubber knot before lubricating.
A small rubber or plastic sleeve which fits over the rubber, behind the prop hook helps reduce motor bunching and climbing. Heat shrink tubing can be used.
Winding Stooge: When winding, it is customary to use a holder or "stooge" to hold the fuselage securely by sliding a thin wire through the rear motor peg tubing. This allows stretch winding without assistance, and will increase flight times dramatically. For design ideas, see these in use at a flying meet. A simple drawing for one is also available.
Winders: To wind the rubber, mechanical winders with ratios of 5 to 1, 10 to 1, or 15 to 1 are readily available. Prices go up from about $10 with expensive ones incorporating a torque meter to provide an indication of the "power" of the rubber when winding. Counters are frequently incorporated into a winder.
A hand drill can be used to make a winder though the ratio is rather low for small rubber. If you decide to go this route, securely fit a hook by removing the chuck and drilling through the side of the shaft. A wire hook can be fixed in this hole and will not pull free while winding.
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- Laminating Wingtips and Fins: Curved outlines such as rudders can be formed by laminating two or three thin balsa or basswood strips about 1/32" x 1/20" around a template cut from a foam plastic plate or foam take out container. Presoaking the wood in water helps with tight curves. Basswood or bamboo about 1/20" square can be used without laminating by soaking and bending around the hot shaft (not the tip) of an electric soldering iron. To laminate two or three strips, apply glue sparingly with a toothpick. R.C. 56 glue is suitable for this as it retains flexibility when dry. Peck catalog lists Basswood in several sizes.
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- Scale Detailing
- Many scale details, e.g., exhausts, wheels, can be made from blue house insulation foam. This is about 3/4" thick and easily cut and sanded, so keep a lookout around construction sites.
- Sharpened brass tubing or sharpened sections from an old telescoping auto antennae are used to cut out small discs from foam or balsa for scale cylinders, wheel centers, etc. Dummy air cooled cylinders for scale engines can also be made by screwing soft balsa into a threaded nut so as to simulate cooling fins.
- Use lightweight materials such as foam or light balsa wheels instead of heavy plastic ones frequently supplied with kits. Blue foam wheels can be cut and sanded to a very scale-like appearance. Use water based acrylic paints or marking pens. Lightweight hub reinforcements can be punched out with paper hole punches from 1/64" or 1/32" ply, and glued to the wheel center. (If CyA glue is used, only use odorless which is foam compatible). Ply discs are lighter than aluminum tubing. Punches in 1/8", 3/16" and 1/4" diameter are available.
- Marking pens are handy for small areas of tissue coloring and do not add weight. Rub on letters are available from art supply stores and are applied to tissue before the tissue is applied to the model.
- Landing gear should be formed from bent music wire then balsa is glued on to provide scale appearance. The wire must be allowed to "flex" on impact. Usually the wire is run from one wheel up to the fuselage, then glued and braced with balsa gussets to the fuselage lower longerons and cross pieces before forming the opposite side. Customary wire size ranges from .031" for heavier planes of around 24" span down to .015" for light Peanut models.
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Plans and Kits
When you visit your local hobby shop, you might find many kits for scale models. Generally these are not recommended when starting model flying. We suggest more simple models for getting your start, including designs like the Jetco ROG, and Dick Baxter's Pussycat and his low wing Akro. all three of these are available as free online plans.
Preserve your plan and do not cut it up when building. Many of us run a photocopy prior to building to preserve the original plan. Photocopiers can be used to scale a plan up or down. Rib and former profiles can be photocopied, glued to balsa with peelable glue stick. Cut out the wood part, and easily peel off the paper template.
As low wing designs tend to be less stable, you might want to build one or two high wing models first. Dick Baxter's Akro might be the best low wing design when starting if you can't wait.
We suggest the wing is built in one piece and fit into a cut out in the body. This is a strong method and avoids the problem of trying to align each wing half correctly.
It is wise to add more dihedral than on a high winger. One rule of thumb is for the wing tips to be at at least the same height as the thrust line.
Some older plans show the stabilizer being built in two halves. Where possible, revise the design to build as one piece.
Stabilizer adjustment can be provided by incorporating a tapered slot in the fuselage using balsa shims for adjustment.
Scale models (especially older plans) frequently benefit from a 10% - 15% increase in stabilizer and fin area. Use an enlarging photocopier.
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Light Weight is Important!
The importance of building light cannot be overstated. This is the key to improved flight times as a 10% weight reduction results in a 15% improvement in flight times. Additionally, because the plane flies slower, it will be damaged less on impacts.
Factors which influence weight include:
Balsa selection: Balsa can vary in weight from 4 lbs. per cu. ft. to as high as 22 lbs., a variation of 5:1, so seek out lightweight sheets using a pocket postal scale to compare sheet weights.
Structure: Minimize weight wherever possible by simplifying the wood structure, perhaps deleting some wood or substituting smaller sizes. Reducing the weight of the tail section is important as most scale planes are tail heavy and the "leverage" effect of the tail and fuselage rear behind the Center of Gravity means that an extra gram at the rear requires about 3 more grams on the nose to counterbalance.
Plastic Propellers: As your models get lighter, you will find that these propellers can be quite heavy. A single edged razor blade can be used to scrape the blades to reduce weight significantly. Often times the blades become nearly transparent in the search of "lightness".
Scales are very useful to aid in lightweight construction. See examples of an easy to build spring scale and other types in common use.
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Experienced help will save a lot of frustration. A comprehensive 10 step flying and trimming guide is also available. Study it!! However, in summary:
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Flying Field Etiquette
- Do not talk to a flier who is winding a motor!!! To see a motor blow as a result of losing count is not a pretty sight.
After launching indoors, immediately step off the floor so as not to impede planes or fliers waiting to launch.
If in doubt, or seeking guidance on building or flying, please ask for advice. We enjoy our hobby and are eager to help, so don't be shy. Remember, there are no stupid questions, only stupid answers!!
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There are many resources of online info for Free Flight modelers. We recommend joining the Free Flight Mailing List. It is an active online community of Free Flighters from around the world, and a great source of all types of info. Also, surf some of the sites of the Free Flight web ring. Many of them contain Event and Contest info.
Locally, check in at the neighborhood hobby shop, and ask for Free Flight contacts. As Free Flight modeling doesn't have the economic visibility or momentum of radio control, they might not be able to help, but don't be discouraged. There are likely modelers in your area that can help. If not, fall back on internet resources for help.
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Fliers, feel free to link to, or print & circulate this document, but please do not claim credit for its creation. It was a lot of work, and a labor of love to help promote the art of model aviation.