NOCALs
Update: 23 DEC 99

What is a NOCAL?

What's Involved in Building A NOCAL?

Wings

Ribs

Body and Tail

Motor Stick

Thrust Bearings

Props

Covering & Marking

Power

Flight

 

What is a NOCAL?

NOCAL models are small, very light, easily built free flight scale models. The term 'NOCAL' evidently stems from the idea of no weight/no calories. They are characterized by a maximum wingspan of 16", minimal structure, a profile look [tho a 2-sided box-body is evidently also allowed - and easily provides a bit of ease in setting thrust offsets], a single loop of 3/32" or 1/8" rubber, and usually are covered on only one side of the structure [a box-body can be covered on all sides]. These models can be flown indoors or out, though outdoor flying must be done in gentle winds. NOCALs can be built to weigh as little as about 2 grams - for reference: the current U.S. one cent piece, the 'penny' weighs 2.5 grams. Pre-1974 US pennies weigh 3.1 grams and some contests [including the indoor FFML postal events] require a NOCAL to weigh a minimum of 6.2 grams. 

Flight times of one minute are fairly easy to achieve outdoors without lift, and indoor times can exceed 2 minutes. In fact, outdoor NOCALs often fly away in thermals, but they are so easy to build that this should not be considered a problem. It is entirely practical to build a NOCAL with ordinary hobby shop stick and sheet wood - and not much is needed. Ordinary plastic props in 6" or 7" diameter work well, although as you progress, you can improve flight times with a 'cottage cheese' prop or one made from thin sheet balsa. Along those lines, a more competitive, but definitely also more delicate, NOCAL model can be built with 'indoor' balsa, nominally 4-6 lb. per cubic foot.

All-in-all, NOCALs are perhaps the biggest bargain in terms of flight results received versus effort and costs expended.

NOCAL models are small, very light, easily built free flight scale models. The term 'NOCAL' evidently stems from the idea of no weight/no calories. They are characterized by a maximum wingspan of 16", minimal structure, a profile look, a single loop of 3/32" or 1/8" rubber, and usually are covered on only one side of the structure. These models can be flown indoors or out, though outdoor flying should be done in gentle winds. NOCALs can be built to weigh as little as about 2 grams - the current U.S. one cent piece, the 'penny' weighs 2.5 grams. A more practical weight, offering enough strength for outdoor flying, is 6-7 grams.

Flight times of one minute are fairly easy to achieve outdoors, and indoor times can exceed 2 minutes. In fact, outdoor NOCALs often fly away in thermals, but, they are so easy to build that this should not be considered a problem. It is entirely practical to build a NOCAL with ordinary hobby shop stick and sheet wood - and not much is needed. Ordinary plastic props in 6" or 7" diameter work well, although as you progress, you can improve flight times with a 'cottage cheese' prop or one made from thin sheet balsa. Along those lines, a more competitive, but also more delicate, NOCAL model can be built with 'indoor' balsa, nominally 4-6 lb. per cubic foot.

It is relatively easy to make a NOCAL model look quite realistic by careful choice of colored tissue and the addition of proper markings. These markings are prepared in/on the tissue before the model is covered. Often, a piece of tissue can be placed over the plan and various markings traced thereon. Markings can be done with dark tissue over light colors, a 'sandwich' covering where light/dark colors are joined in a sort of collage with very narrow overlaps, felt markers, art pencils, sticky-back insignias, and probably even many more ways. One of the more exciting developments is the idea of printing panel lines and markings right on the tissue with inkjet or laser printers. Part of the key to this process is that NOCALs are so delicate that the covering tissue can be neither shrunk nor doped, therefore these inks can be used as-is.

All-in-all, NOCALs are perhaps the biggest bargain in terms of flight results received versus effort and costs expended.

What's Involved in Building A NOCAL?

The term 'profile' has been mentioned - what this means is a simple outline structure of the body [as viewed from the side], and the tail surfaces. These outlines are constructed on the plan, most often from 1/16" square balsa, with a few scraps of 1/16" sheet wood added as needed for creating shapes. Shapes of airplane bodies viewed from the side usually allow using gently curved sticks, braced by a few vertical or angled uprights. There is little need for strength in a NOCAL body as the rubber motor's stress is controlled by a motor stick attached to one side.


Wings:

Lay out and pin down the sticks for the leading and trailing edges. If your model has curved wing tips, there are a couple of choices for methods - laminating and piecing together.

To laminate, make up some strips of balsa 1/32" X 1/16" long. Make up the forming template to match the inside contour of the piece from cardboard or 1/16" plywood. Rub the edge of the template with candle wax so the laminated parts won't stick to it. Soak the stripwood in household ammonia or Windex for a few minutes, dry them on a paper towel and appy a thin layer of white glue to each strip to make the laminate sandwich. Attach the sandwich to one edge of the template with a strip of masking tape. Then, while pulling on the free end gently, apply light pressure to form the curved edge. Add more strips of masking tape and work your way around the template. Recognize that the strips must slide on each other in order to form the curve, and don't be surprized if a strip or the whole stack breaks on your first few tries. To dry the laminate, you have at least 3 choices (1) Let the piece dry overnight, (2) Let the piece dry under the heat of a 100W lightbulb for an hour or so, and (3) Let the piece dry in a microwave oven. Set it one 'High', run for a minute, turn the piece over and run it once more. The tape strips may come loose - but they can be replaced as needed. When dry, remove the tape and lightly sand the edges of the laminate before removing it from the template. Make another piece for the other tip.

Some builders might prefer another method for making curved parts. So, instead, we can piece together the curves using 1/16" square stick wood, in the manner of stick & tissue kit building. Here, pin down the first  stick over the longest portion of the curve. Then, keep adding sticks cut with fairly shallow tapers to move around the curve. Trim and sand the curve to shape, recognizing that the joints may need additional glue as the shaping process continues.


Ribs

NOCAL models are generally built with 'sliced' wing ribs. Sliced ribs are usually 1/16" square [or a bit smaller] in cross section and are cut from sheet balsa, with the grain running front-to-back, using a template as a guide. The template should be made of sheet plastic, aluminum or thin plywood, so that the cutting guide edge can be made quite smooth. Making the template slightly overlength helps to get cleaner ends on the ribs. Use an Xacto with a new #11 blade to cut each rib. Make extra ribs as a few will be weak or thin. It's a good idea to mark the left or leading edge [LE] of the rib sheet and the template to make sure the ribs will all point the same way. Left-handed folks will probably find it better to put the LE at the right edge.

When fitting the ribs in place, trim them to length from the trailing edge end. On a tapered wing, this helps produce a slightly thicker [in percentage terms] airfoil toward the tips, which some authorities advocate for beneficial effects [the wing will have different stall characteristics along its span and not stall all at once]. A few seconds spent in fitting the rib-to-LE & TE joints with fine sandpaper applied to the rib ends will produce a stronger wing.


Body and Tail

These parts go together a bit quicker because they are flat. Piece together, laminate edges or use scrap sheet fill to produce the shapes needed.


Motor Stick

NOCALs are typically equipped with some kind of a motor stick that is strong enough to withstand the tension and torque twist of the rubber motor. Actually, that is a misleading statement as some of my NOCALs with long bodies exhibit a decided twist with the rudder, stabilizer and rear end about 15-20 degrees off the vertical. Upon seeing that, one might wonder about the effects on the climb, but so far, I have not seen any strong change.

The simplest motor sticks can be made from a couple of pieces of 3/32" square balsa joined together. The glue joint seems to add a measure of stiffness beyond that of just cutting one piece 3/32" X 3/16". More serious builders may use rolled sheet balsa motor sticks, with the idea being borrowed from the older indoor endurance model designs.


Thrust Bearings

While some designers advocate a glued-in thrust bearing, I have always felt that one needs to be able to readily adjust the thrust line of a NOCAL. All NOCALs seem to need some downthrust, and most require some kind of offset to the left or right, and you will not know which direction and how much until you do some test flying.  My plans reflect 3 or 4 different ways to do this, but the bearing shown in the diagram is my favorite. This bearing is suitable for outdoor NOCALs that may carry a motor made of a loop of 3/32" or 1/8" rubber. The bearing is readily adjustable by holding the motor stick portion and then twisting or bending the vertical leg of the brass strip - with these actions being accomplished using the thumb and forefinger of both hands. Impacts with the ground or stationary objects probably won't upset the adjustments.

All of these durable qualities suggest that the bearing as shown is probably too strong and heavy for indoor models - but it's a good one to use starting out. For a more lightly builtlighter model, look for the next thinnest brass strip, which is about .015".

The prop shaft is 1/32" dia. wire, running in 1/16" OD X 1/32" ID brass tubing about 1/4" long. After the brass strip has been cut to width, bend it into the 'U' shape. Make up a supporting jig to hold the bent strip securely and then solder the tube in place. While electronic solder does work OK on brass, I prefer Staybrite silver bearing solder - from the hobby shop, or a comparable product available at Radio Shack.

 

By now, you probably have noticed that the body on a NOCAL is not very strong - because it doesn't really have to be. The motor stick really ties the plane together as it typically runs from the thrust bearing back to the stabilizer, and a few vertical or angled sticks tie the motor stick and wing/wing mount together.


It is relatively easy to make a NOCAL model look quite realistic by careful choice of colored tissue and the addition of proper markings. These markings are prepared in/on the tissue before the model is covered. Often, a piece of tissue can be placed over the plan and various markings traced thereon. Markings/comouflage can be done with dark tissue over light colors, by way of a 'sandwich' covering where light/dark colors are joined in a sort of collage via rubber cement or glue stick with very narrow overlaps, felt markers, art pencils, sticky-back insignias, and probably even any more ways. One of the more exciting developments is the idea of printing panel lines and markings right on the tissue with inkjet or laser printers. Part of the key to this process is that NOCALs are so delicate that the covering tissue can [realistically, considering the warping effects of water or dope] be neither shrunk nor doped, therefore these inks can be used as-is.

By the way, you can also 'stabilize' tissue from additional warping with a coat of Krylon clear spray stuff from the hardware store. There's even a new version of the clear that claims to be UV resistant - i.e. it may be more resistant to tissue color changes!


Props

The quick and easy approach to props, especially outdoors, for a NOCAL is to use a 6" or 7" plastic prop. Peck props in those sizes work well and there is a wide-bladed 6" one marked with a 'T' [the old Tern Aero prop] that is worth trying.

As time allows, we will add some specifics about making your own prop to these pages. Making your own prop allows you to experiment with materials [balsa, cottage cheese container stuff, foam coffee cup stuff], the diameter, area and pitch. The first thing to consider is that most plastic props have too low a pitch. We sometimes talk about the P/D ratio, that is, the ratio between the Pitch [the theoretical distance a prop will move in one revolution] and the Diameter, both being expressed in inches. For rubber powered models, the P/D should be about 1.2 or 1.5/1, tho sometimes up to 2/1 is used. In contrast, the P/D of plastic props runs about 1/1 and often less, meaning that efficiency is somewhat less than it should be.


Power

Very satisfying flights can be achieved in outdoor NOCAL with 3/32" and 1/8" FAI Tan II strip rubber. The weight of the model will determine which needs to be used. Generally, one can start with 3/32" in a loop about as long as the distance between the hooks. If the model will climb on this size rubber, then you won't need to go to 1/8". After you get this stuff figured out, you can go to a motor up to about 2.5X the distance between prop and rear hook.

Hand winding a skinny motor like this is tedious - get a geared winder from Peck or SIG. If you have an old hand cranked drill around the house, you probably can use it - but determine its gear ratio first so you'll know just how many turns are being used. Some of the common hand drills run at even number ratios such as 4-to-1, although one that I have runs at 3.67-to-1, thus requiring a conversion table if an exact number of turns is required. These hand-drill ratios are kind of slow for winding a skinny motor [tho they work OK for peanut, walnut, and P-30 models], so a 6-to-1 or 10-to-1 ready made winder might be handier.

Determine the maximum number of turns possible by winding a sample motor to destruction - off the model - hang it on a nail or doorknob! If a 10" long loop bursts at 1,000 turns, then you have established that material as suitable for up to 100 turns per inch of loop length. In reality, something on the order of 90% should be considered a practical, repeatable limit.

Lubricant should be used to protect the motor and to allow more turns. You can buy commercially made lube from SIG or FAI, or you can use Armorall. Just rub some lube on the rubber strip, preferably after the knot is tied [very difficult to tie a knot that will stay in lubed rubber]. A square knot can work well if a very tiny bit of CA glue is applied to each strand where it leaves the knot. Examine the motor frequently - if a strand looks frayed or cracked, throw it out because it will probably break the next time it is used.

Flight Testing

Here we see a real difference between indoor and outdoor. 

Indoor flyers have determined for the most efficient flight that the model must not glide - it must be under power at all times and land with a few turns left. If the plane lands with a lot of turns left, the motor must be made bigger in cross section, i.e. 'stronger' , altho a shortened version of the same motor may still fly the plane if wound tighter. Conversely, if the indoor model runs out of turns while still above the floor, the motor can be made longer and wound more, providing a longer flight.

Outdoors, we can fly the model in a similar manner, but usually the plane finds it harder to achieve enough altitude to clear the ground, cars, people and other obstacles at such low levels of power. Thus we try to achieve a stronger power run and gain altitude in our search for thermals. A freewheeling prop is of some value here, but this idea is periodically discussed among the theoreticians who claim that a stopped prop has somewhat less drag than a freewheeler - you can make your own choice here as thermals don't listen to those theories anyhow - they just try to lift light objects like your plane!

Start flight testing by establishing the proper balance point for your model. As much as it might 'hurt', use a bit of clay to correct  the balance. Outdoor models can be test glided but there's little to learn at such low altitude.

So, good luck in your first efforts at NOCAL! Please do not hesitate to ask questions of me or the FFML in general. / AL
Contact me:
aalmps@aol.com.