Don Slusarczyk had this posted on his website years ago. There is a lot of good information here! His site disappeared, but I kept the text. He has given me permission to post it here. As this is an old article, Don says he has some updates. We will post them when he makes them available.
No-Cal Building Techniques
This page is a by-product of the discussion which came about on the Free Flight mailing list concerning lightweight Indoor No-Cals. It has been suggested and or implied by some that we ‘experts’ are ruining ‘beginner’ events by taking the fun out of these events, and replacing it with competition. I personally will make no apologies for my competitive nature, but in return will provide and educate those who are willing to listen, with the techniques required.
So you want to build a Contest Winning No-Cal?
Know the rules:
I think most of us are aware of the No-Cal rules. The one thing you need to know is what weight rule No-Cal are you building to. As far as I know there are three current No-Cal weight classes, 6.2 grams and over, 5 grams and over, and no weight restriction. (Of course there is WWII combat, but that falls into the same weight categories) Once you decide which event you are flying, then you can choose the model you are going to build.
Choosing a subject (How big should the wing be?):
The model selection is based on the event weight class you are going to build. For 6.2 grams and over, you will need a model with a wing around 80 sq. inches. For 5 grams and over, a model with around 65 sq. inches will work just fine. Unlimited No-cal works quite well with models in the 50 sq. inches of wing area range. Why is this?
Well, a 6.2 gram no-cal is actually a very heavy weight model. You can build a lot of structure for the weight your allowed. This is why this event is now flooded with racers. Most racers have low aspect ratio wings with long bodies. This type of model could not be built very light because there is so much structure needed due to the overall large size of the model. But since you are allowed so much weight, a large fat chorded model can be build without any penalty.
6.2g Subject Examples: Bonzo, Chambermaid, Cassutt Racer
A 5 gram No-cal is pretty much the same. Most people I know fly their 6.2 gram No-cal in this event because most of their models really weight just under 6 grams and they carry some ballast to bring them up to weight. However, I think that a separate model should be built for this class. A slightly smaller model than what is used in the 6.2 gram is ideal.
5 g Subject Examples: Fike, Lacey M10
Unlimited No-cal is the toughest one to decide on. A compromise has to be found between model size and final weight. If you pick a large long model, it may be too heavy to fly well (Chambermaid). If the wing is too small, (Found Centennial or Pilatus Porter), the wing loading is too high even though the model may be light.
A good compromised is a model with around 40 to 50 sq. inches, and around 16″ inches on length. Another thing to consider is landing gear. Retract airplanes do not require landing gear, so weight is saved by the absence of the landing gear.
Unlimited Subject Examples: Bede BD-4, Cessna Cardinal
Choosing a subject (What about motor stick and nose length?):
The nose and motorstick length of the No-cal subject is a major factor in determining the models final weight. For example, the first model I built for 5 gram no-cal was a Farman Biplane. Each wing was about 3″ in chord which yielded about 80 sq. inches. However, the model has a short nose. The model complete weighted 3 grams. I added some nose weight to get it to glide and then reweighed the model. To my shock, the model was now 5.5 grams. This 3.0 gram model needed 2.5 grams of nose weight to make it glide. Additional nose weight was needed to get the model to fly with a rubber motor. Because there was more motor behind the CG than in front of it, I needed to add additional weight to compensate for the motor. In this condition the model weighted 6.5 grams, 3.5 grams being nose weight. A quick calculation told me that for each .1 gram weight reduction in the tail, resulted in a .3 gram reduction in required nose weight. This meant if I made the tail .1 gram lighter, I could remove .3 grams nose weight for a .4 gram total weight reduction. I removed some tail structure, .2 grams, and then removed .6 grams of nose weight and the model instantly dropped .8 grams, to 5.7 grams from 6.5 grams.
This is a good example of how choosing a subject can make or break your effort. If you are building any no-cal, a good rule of thumb is to make sure the middle of the motorstick coincides with the CG location. The motor stick should also be 10″ to 12″ in length (for 5 gram and 6.2 gram), and 8″ to 10″ for unlimited no-cals. Using this rule, you can determine if the nose length for the subject you have chosen is long enough. If it is not, the rules of no-cal allow you to stretch the models fuselage a little since the rules state the model must be a ‘recognizable’ model. So if the nose needs to be a half inch longer, so be it, the rules allow it.
The reason you want the motorstick ‘balanced’ is so that when the motor is added to the model, it will not move back the balance point. If it does, then more nose weight is needed to counteract the motor weight. In fact, on my real light no-cals, there is more motor in front of the CG than behind it. This allows the motor and motorstick to act as nose weight, which in turn lowers the total model weight.
The BD-4 No-cal I have actually has .2 grams in tail weight because it was too nose heavy. My general rule of thumb is that an unlimited no-cal should have at least 60% of the motorstick located in front of the CG. Using this rule, no-cals can be built with the least amount of nose weight needed, in fact they may need any at all like my IL-2 WWII no-cal (1.8 grams). This model has an 8″ motorstick with about 6″ of that being in front of the CG, the motor acts as the model’s nose weight. The reason I could do this is that the IL-2 has a long nose. I could not make a Japanese Zero to this weight, because the nose is much shorter, it would need 1 gram in nose weight just to get the CG in the right location.
My final example to drive this point home even further is about my Clipped wing Spitfire WWII no-cal I use to have. When I built it, it weighed 2.8 grams with a 11″ motorstick. This model required .5 grams in nose ballast. A year later I decided to shorten the motorstick to 8″. The reworked model no longer required the .5 grams of nose weight, since more motor hung in front of the CG than previously. The lighter motorstick also resulted in a weight reduction, and the new model weighed in at 2.2 grams, a .6 gram reduction just because the motorstick was shortened 3″. All of the structure remained the same, but just the way the motorstick was positioned reduced the weight drastically.
Choosing the right wood:
Wood selection is also a critical factor in building a good no-cal. This wood can be purchased from Indoor Model Supply, or any other good indoor supplier. Some of the wood I use is from a local hobby shop, most places do not care if you bring in a scale and quickly weigh the wood.
5 gram and 6.2 gram:
fuselage outline: .050 x .050 5.0 to 5.5 pound A grain
(do not rely on outline to provide support)
wing spars: .065 x .080 6.0 pound A grain (may need to be .095 high)
wing ribs: .035 x .070 4.5 to 5.0 pound A grain
tail surfaces: .035 x .065 5 to 5.5 pound A grain
motorstick: .015 – .020 4.5 to 5.0 pound C grain 5/16″ o.d.
tail boom: .012 – .015 4.5 to 5.0 pound C grain 1/4″ o.d. to 1/8″ o.d.
fuselage outline: .030 x .030 5.0 pound A grain
wing spars: .030 x .065 5.5 to 6.0 pound A grain
wing ribs: .030 x .060 4.0 to 5.0 pound A grain
tail surfaces: .025 x .050 5.0 to 5.5 pound A grain
motorstick: .010 to .012 4.0 to 5.0 pound C grain 1/4: o.d.
tailboom: .008 to .010 4.0 to 5.0 pound C grain 3/16 o.d. to 1/8 o.d.
Choosing the right covering material:
Covering material is based upon the weight class being flown. Unlimited no-cals should be covered with Gampi tissue to keep the weight down as low as possible. For the 5 gram and 6.2 gram events, Japanese tissue can be used without much of a problem. If you feel that you are more comfortable building a model out of heavier wood, then you can use Gampi tissue. Most Gampi is about 3/4 the weight of Japanese tissue, so the weight you save in covering can be turned into structure. This, by the way, is the method I prefer. I would rather have a stronger model with light covering than a weaker model with heavier covering.
The propeller of a model many times is the most overlooked part of the airplane. Many people spend hours building a model, but do not give the propeller the time that it deserves. I am reminded of a story I was once told about a modeler who was having trouble trimming out a particular p-nut scale model. He got some help from a local p-nut guru during a flying session. The model was trimmed out and was flying quit well. About an hour later the guru saw this modeler launch his airplane, and it flew horrible. The guru went over and asked him what he had changed on the model, the modeler replied “Nothing, just the prop.”
Care must be taken to ensure you have a well built, and well tracking prop. Heavy no-cals need to have prop blades made from .020 to .030 5.0 pound C grain wood. Light no-cals use .010 to .014 4.0 to 5.0 pound C grain. The prop spar needs to be rigid and stiff 8.0 to 9.0 pound A grain for heavy no-cals and should be about .095 round in the middle, tapering to .060 round at the ends. The lightweights are made from 6.0 to 6.5 pound A grain, and should be about .065 round to .045 round.
The diameter of the props should be in the 10″ to 12″ range. The pitch should be about 1.2 to 1.5 times the diameter. The blades for all of my no-cals are formed on a 5″ diameter can on about a 15 degree angle.
When building your no-cal, you should try to stay away from super glues, except for special areas. I use Duco Household Cement diluted with acetone (40% glue 60% acetone) for most of my gluing on all my models. It is quick drying, about 15 minutes, and is very light and strong. I only use super glue around the nose bearing, the rear hook, and for gluing the prop shaft to the spar. Super glue is quite heavy if used to build the entire aircraft. When covering the model, I quite often use 3M spray adhesive, or sometimes white glue and water (20% glue 80% water). However, under NO circumstance should clear dope be used for covering indoor no-cals! You might as well put a coat of lead on the model and throw it out.
And that is it! No hocus! No pocus!
I hope the information presented here helps out those who are looking for answers on no-cals.
Some of you have expressed interest in reproducing this web page in part or in whole for various publications. I hereby give permission for all to use, with three (3) stipulations:
- mention my name (who knows maybe you’ll get a good seat!)
- mention this web site address (http://www.indoorfreeflight.com)
- please send me a copy of your finished article/newsletter/publication because I would love to see it!
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