From the PREZ
Prez Sez, by Walter Pierzchala
ANNUAL AWARDS
At the November meeting nominations will be accepted
for the Doug Davidson
and Technical Achievement awards. If you know of an
individual deserving
of either of these awards, please nominate that individual
and tell the
club why that individual is deserving of the award.
At the December meeting
elections will be held of the nominees. The awards
will be presented at
our annual banquet in February.
NEW BOG MEMBERS
At the October meeting there were new Bog members voted
in for the term
2001 to 2002.
Warren Barrick
Rick Bruce
Al Campana
Jim Campana
Mario Chiarolanza
Bob Dolan
Mike Estock
John Matt
Dee Messina
Jim Myers
Joe Pasquini
Ed Snead
Congratulations gentlemen!
CLUB HATS
Ed Snead
Ed Snead who has ordering club hats for the membership
for the last few
years, has finally placed his last order. After ordering
hats from Ed, it
seems that he has to chase after members and plead with
them to pick them
up. How long do people think that Ed should carry these
hats around to
meetings and to the field looking for the owners to
receive them? Ed has
hats for guys that join the club and then quit before
their hats arrived
and due to his honest nature, never even paid for them.
he has hats in his
house,hats in his car,and hats in his van In November
at the club meeting
everyone who ordered a hat should be there to claim
it as all hats not
picked up will be dropped in the #2 barrel to die just
like all of the
others before them This is also to inform all club
members: "DON"T ask me
to get you a hat as I am out of the hat business
from the editor:
I have watched the frustration that Ed has endured
over the last couple of
years. I am sorry that it has come to this. Why wouldn't
the people that
buy hats pick them up? Doesn't any of the lackies appreciate
the fact that
Ed goes to the trouble of doing this service? If
you don't realize the
effort that has gone into it, then you are just plain
insensitive and you
can't smell the coffee in the morning. Thank you Ed
for a job well done and
for the extra effort that you gave to make the program
work.
NOVEMBER RAFFLE
Joe Yalove
The following items will be available at the November
raffle.
1.Dremel multipro 2 speed cordless tool kit
2.Uproar funfly 40 size kit
3. X-acto knife chest
4. OSMAX 40 LA engine
5. Topflite striping tape tool
ANNUAL CLUB AUCTION
Ed Snead chairman
The club auction will take place at the Valley Forge
Middle School on November 4th. This is the first Saturday
in November. This
is the same location as last year. There is a $3
admission. There is no
additional fee for sellers or buyers. Doors open
at 9AM for sellers and
bidding will begin at 10:30AM. Refreshments will be
available. No items may
be sold after they enter the building except at
the auction. Personal
transactions can be made in the parking lot before
the merchandise is
brought into the school. Bring whatever you have to
sell. You can stipulate
a minimum bid for any item. Each item for auction must
be accompanied by a
seller sheet which is published in this Hearye.
Propeller Size Comparisons
Jim Myers
I like to think of an airplane propeller as something
that moves a volume
of air. That air has mass, and in moving that mass
backward along the
plane, the reaction forces the plane to move forward.
As a propeller turns, imagine that it slices through
the air with no
slippage, say, like slicing through Jello. Then, in
one revolution, the
prop would advance a distance just equal to its pitch.
For example, a
10X6 prop would advance six inches. The volume of the
air (or Jello) moved
in one revolution would be equal to the volume of a
circular cylinder, 10
inches in diameter, and 6 inches high. Mathematically,
this volume can be
calculated from the formula
where VPR = "Volume Per Revolution" (cubic
feet), D is diameter (inches),
and P is pitch (inches). Or, we can combine the constants
to make this
equation easier to use:
Again using the 10X6 example, we would compute its VPR
to be 100x6/2200 or
0.27 cubic feet. So, if your engine can spin the prop
at a maximum of
10,000 rpm, it would theoretically move the air at 2700
cubic feet per
minute ("cfm"). However, no propeller is
100% efficient, and the prop will
not really move the air that rapidly. In reality, the
flow rate would be
reduced to maybe 60% or 70% of the theoretical value.
Anyway, my purpose is not to try to compute the absolute
volume flow rates
of propellers. Rather, I just wanted to use the equation
above to
illustrate a comparison of most of the popular sizes
of model propellers
available.
This comparison is shown in the graph below. The legend
at the right of the
graph identifies the symbols that correspond to four
different pitches: 8,
7, 6, and 5 inches. Each marker corresponds to a propeller
size that
should be commercially available. The 10x6 is denoted
by a square symbol,
second from the left, at a diameter of 10 inches, and
placed on the 6"
pitch curve. It is easy to see from this graph that
increasing the pitch,
or the diameter, or both, will always increase the volume
per revolution,
or VPR.Given the engine's limited power, it will be
unable to drive the
larger propeller at the same maximum rpm. I have not
tested this, but I
would expect that the max rpm would decrease by roughly
the same ratio that
the VPR is increased. For example, an 11x6 prop has
a VPR of 0.33 cubic
feet. Using this on your engine would probably reduce
the rpm by the
ratio .27/.33. This will reduce the maximum rpm from
10000 down to
approximately 8200 rpm. This is very likely to reduce
the noise of your
engine. But notice that it will still be moving the
air at the theoretical
rate of 2700 cfm, and therefore, the thrust will not
be diminished.
Now, I am sure that those of you knowledgeable about
the power curve of an
internal combustion engine may find fault with this
simplified analysis.
The reason is that the engine's peak power is attained
at a particular
rpm, using the manufacturer's recommended prop. Therefore,
the "wrong"
size prop will reduce the maximum power output. But,
as long as you don't
make a really radical change, the loss in power should
hardly be
noticeable.
See how this chart works for choosing alternate prop
sizes. If you use
prop diameters larger than 15 inches, or pitches larger
than 8 inches, you
can always use the formula and your calculator. Let
me know if you find
this stuff useful.
Builder's Corner
Gerry Keenan
All of us have to deal with where we are going
to work on our planes.
I've found that the most common areas are, the garage,
the basement, the
kitchen, the living room, the bedroom, and last but
not least, the
bathroom. Let's see what the ideal shop should have
and then see what's the
best space for you.
The environment that you build in should be comfortable.
Is it warm in the
winter and cool in the summer? I like to hear myself
think. Are there
distractions where you're building? Isathere plenty
of light, ventilation,
electrical outlets and room? Your going to be using
C A and ventilation is
real important. I've heard that the government spent
millions of dollars on
a study and determined that gluing your lungs together
can be dangerous to
your health. Good lighting is a must. You can get workshop
lights very
cheap and hang them over the bench. I would also take
my model outside when
it's sunny and look it over, what looks good late at
night doesn't always
look good in the sun. As for outlet's you can get strip
outlets screw them
on you bench and you should be ok. Just don't run everything
at once.
In the ideal workshop you will need a workbench.
The only thing I'll
say is make sure the top is flat. Some guys use a card
table and place a
ceiling tile upside down on it. The T-pins will push
in to it quite easy.
One guy I know got a damage door at home depot and swears
by it. I got a
hardwood workbench at home depot and I lay a piece of
drywall on it.
Whatever you do just make sure it is flat by laying
a straightedge on it.
Some other things you should consider are a chair, storage
bins, shelves
for your tools, something to hang the blueprints on
( I use two hangers
that you hang pants on hooked to the ceiling), a vise,
a file cabinet ( a
cardboard box will do), a coffee pot and or a beer tap,
and a table or
place to put pieces that your not working on. There
are plenty of things
you can add, but the workbench and chair are the heart
of your shop.
Whatever your budget and room situation is, Just
do the best you can,
You can make it as plane or fancy as you please. If
you get stuck, there
are plenty of ideas out at the field. Next month:
FRAMING
BOG MINUTES
Dee Messina
BOG meeting held 10/17/00 opened at 10PM
12 members present 9 new members present
`
1. Some old business cleared up about purchasing a
minimum of repair parts for the old lawn mower.
About
$100 will be allotted.
2. A treasury audit will be performed before the new
officers
convene.
3. The new BOG officers are as follows:
President: Warren Barrick
Vice president: Dennis DiBonaventura
Treasurer: Carl Sutton
Secretary: Dee Messina
The following are new BOG members for the year 2001:
Warren Barrick
Rick Bruce
Al Campana
Jim Campana
Mario Chiarolanza
Bob Dolan
Mike Estock
John Matt
Dee Messina
Jim Myers
Joe Pasquini
Ed Snead
Feedback or comments to:
Ernie McGauley , HearYe editor
Michael Myers, Webmaster
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