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.
Subject Examples: Bonzo, Chambermaid, Cassutt
Racer
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.
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
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 Jap 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.
Unlimited weight:
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,
Jap 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 Jap 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:
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.
Adhesives:
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. If you would like to ask specific question please feel free to email me: don@indoorfreeflight.com
And finally,
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:
# 1
mention my name (who knows maybe you'll get a good seat!)
#2 mention
this web site address (http://www.indoorfreeflight.com)
#3 please
send me a copy of your finished article/newsletter/publication
because I would love to see it!
Don Slusarczyk 868 Eaglewood Dr. Willoughby, OH 44094