SEN 735 - 4 Sep 2002
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SCAT Electronic News 4 September 2002 issue 735
Table of Contents
=================
RE: Model Aviation Free flight Column - Joyner - Indoor Tim
Re: Model Aviation Free Flight Column - Simpkins
F1B timers - Brooks
COPPA GUIDO FEA - Manoni
Re: Doug's formulas for displacement - Thorkildsen
Broken Wings, Bunting and Bureaucrats - Barker
Trig Lesson - Hatschek
Orbiteers Annual Results report? - Beecroft
Tips on tips - O'Dwyer
Reference to curved wing tips: - Barr
Super Max.... - Shailor
Bunting Good Summary - Edge of Beyond
Poitou - Woodhouse
Curved surfaces - Lipori
Extended Max - Boutillier
More area of funny shapes disiderata - SweepetteLee
Whoops - Bogie ... and others
RE: Model Aviation Free flight Column - Joyner
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I spoke to Bob Hunt at length on the subject of the cut in free flight
columns and the truth would seem to be a little different than the terse memo
would indicate. While I believe the letter that was posted is an exact quote of
what Louis received, I think it was a very poor expression of the actual changes
that are going to occurring. In this regard I would suggest to Bob Hunt that he run
his memos by the PR people when he is implementing a major change like this.
A little time spent calling the columnists and selling them on the vision
would have been well invested.
Regarding the changes. This is my understanding of what Bob told me during
our conversation. First off, this is not a move by MA/AMA to down play free
flight or any of the other disciplines in the areomodeling arena. The
current
problem is that there are just too many specialties and they all feel the
need for a column. Because of this the number of pages available in MA for
non-column articles has been shrinking to the point that it is hard to fit
in many feature articles. Another aspect of this is that while the columns
address issues specific to the topic they are not a very useful medium to
introduce participants of an opposite discipline to the column discipline.
With this as a background the changes make more sense. It is my
understanding that all disciplines are being affected by the cut in columns
and that includes control line and RC. The overall goal is to free up
magazine pages for features. That leads to the second part of the vision.
Bob wants to use the feature space to run articles that truly promote the
various disciplines. One of his visions is to have a "state of the sport"
feature article for each discipline. This would have a very large work that
covered everything from how the discipline got started, the notable history,
how a person can get started with it, the reference material, books,
publications, groups, and websites that support it, etc. In other works a
complete run down on what it is, why you would be interested, and how to get
involved and he wants to do this for ALL disciplines in the hobby.
That leaves us with what we can do to take advantage of this opportunity. My
suggestion is that bitching on this list and not renewing your AMA
membership will not do anything positive. The biggest thing we can do is get
busy and start producing some quality articles and submitting them for
publication. As the publisher of Indoor News and Views I can tell you from
experience that many people want to complain that so and so gets published
all the time and this aspect gets too much ink. If you want to know the
secret to getting published and having your interests featured, it is to
write something about it and send it in. So and so get published all the
time because they have something to publish. It is that simple. On the
indoor front we are proactively taking advantage of this opportunity and I
would suggest that outdoor free flight do the same.
Tim
[Denver, CO]
www.IndoorDuration.com
Many new items and tools at
www.F1D.biz
Re: Model Aviation Free Flight Column
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What's next? It seems that free flight is slowly getting squeezed out of
Model Aviation magazine and will be appearing in only four issues a year
with coverage limited to only two pages, another step in the demise of free
flight from an organization that was founded by free flighters. The
excellent articles written by Louis Joyner each month are the only joy I get
from my monthly issue of Model Aviation.
The reality is that AMA is doing very little for the free flight enthusiast,
aside from having a flying field in Muncie. There is no iron clad rule that
a contest or meet has to be sanctioned by AMA. Perhaps it's time for NFFS to
expand it's operations to issue charters and sanctions to the free flight
community exclusively and expand the scope of it's publication, the Digest,
and perhaps include the excellent articles by Mr. Joyner. The summary is
that NFFS would be the core of all free flight activities and not AMA. NFFS
already has a great web site for dispensing news and activities. All current
free flight categories would then be under NFFS jurisdiction and management.
I just hope this not all a pipe dream as I do feel it is time for a change
to an organization that is dedicated to free flight.
Don Simpkins
F1B timers
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I'd like to build a model using a timer to move the surfaces
instead of my torque system. I need the lightest/smallest 3 function
timer available. I've got a Starline 3 function at 14 g, but it's a bit
big for what I want to do. Is there anything smaller at that weight or
less?
COPPA GUIDO FEA
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AGO-TORINO club is pleased to invite you to 9th "Coppa Guido Fea" for
F1G-Coupe d'hiver class with international participation.
Schedule :
Sunday October 6th at 8.30 at Crivelle-Buttigliera d'Asti, 30Km east from
Turin - NW Italy. Contest on 5 rounds.
Entering is possible on the field, a notice of participation is recommended.
On Saturday afternoon it is also scheduled a "fun-fly" event for all
free-flight classes mixed (except F1C) on 3 rounds.
For a full program, any information or participation notice, please e-mail :
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Re: Doug's formulas for displacement
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Doug's formulas work for the displacement which is
equal to the swept volume. The swept volume equals
the area times the stroke times the number of pistons.
The area 3.14178 times the radius squared. Since
the bore is the diameter and two times the radius than
you have to divide the 3.14178 by 4 which gives you
the .78544 factor. A lot of calculators have the pi
symbol which is the 3.14178 number.
As an old drag racer and an engineer it was always
interesting to calculate what your new displacement
would be when you went .030 or .060 inches over on a
small block.
Thermals,
Terry Thorkildsen
Broken Wings, Bunting and Bureaucrats
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SEN is so frequent I can't keep up. I am certainly not complaining but
by the time I have thought of a cogent contribution someone has nearly
always already said it. The following are just a few late opinions.
HLG broken wings - I have ofen seen Kevin launch HLG. He is a big
strong boy with a dedication to HLG and could pull the wings off a
glider if any one can. But from my own experience of long ago, when I
could still throw, I side with those who think a bad launch is more
likely to be responsible for wing breakages. It is when you are trying
to throw your hardest that the smoothness goes.
The modern ways, already mentioned by others, will be the way to measure
the speed but I think a mention shouild be made of Joe Maxwell (the jig
genius) who, back in the 1940s, tackled the problem. He "threw" a
lighted electric light bulb as hard as he could and photographed it with
a still camera. The bulb gave a trace on the photograph with bright
spots every time the bulb was energized by the 60 cycles per second
supply. From this accurate timing and the measured distances he could
calculate the speed. Clever.
Bunting on a knife Edge - Quite often the question is a more important
contribution than the answers because, very often, people do not realize
that there is a question to answer. So thank you Chris for the
question. I have never flown a bunter so I can contribute nothing
practical to the discussion but my instinct, like most other
respondents, is that the quickest way is up, vertical!, but the in and
out phase will make all the difference. The one point I did want to
mention is that the 55 degree climb angle mentioned in Martin Simon's
book is not really relevant. It probably forms a useful exercise for
students but as it relates to aeroplanes in straight flight with no
change of incidence settings between gliding flight and high powered
climbing flight it is not applicable to modern aeroplanes with moving
surfaces and usually turning as well. Incidentally the angle is not
exactly 55 - it changes with L/D ratio. For example 49.8 at L/D 6, 53
at L/D 15.
Area of Curved Wingtips - I think the original query was intended to
apply to any curve not just pure ellipses and so the 0.7854 solutions
are probably not what are needed; however there are plenty of well
documented methods of dealing with curved areas whether regular or
irregular. What interests me much more is, who were the stupid people
who foisted this barmy idea of orthogonally projected area upon us - and
why do we still tolerate it? In the good old days before bureaucrats
one could draw ones plan and calculate the areas directly. What has
been gained? It seems wrong to me that one can use any amount of
dihedral with no loss of wing area, normally one expects to trade
stability with efficiency. Did anyone ask the aeromodellers what they
wanted before this farcical method was imposed upon us? I'll bet they
didn't.
John Barker - England
Trig Lesson
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Just got my first copy of SEN. Whoever put me on the list, Thanks! Also
thanks to Roger Morell for doing the job.
In case anybody wonders about the magic number .7854, it is simply
(pi divided by 4). Remember the formula for the area of a circle: pi x r
squared or pi x r x r. A circle is just an ellipse with a = b (a = span,
b=chord). For an ellipse it's pi x a/2 x b/2 or pi x (a x b)/4. Hence, area
of elliptical stab (or whatever)= span x chord x pi/4 = span x chord x
.7854
That's all, folks.
You should have taken geometry in high school. Even more useful is
trigonometry.
Thermals, Bob Hatschek
Orbiteers Annual Results report?
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From: "Robert K. Beecroft"
Indeed, the I-5 was stopped, Northbound. We measured nearly 4 miles of
cars that were stopped altogether, and miles more that were about to get
stuck in the mess. We were lucky not to be slowed by it.
You ended up third in HLG; I have the trophy for you. I also have one
for you for 1st in F1H and another for John Pratt for 3rd in F1G. I'll
bring them all to Elsinore - likely this Saturday.
Results for the FAI events in total:
F1A One perfect score - no flyoff
1st Rene Limberger 1290 perfect score
2nd Mike McKeever 1278
3rd Hector Diez 1225
4th Norm Smith 1125
5th Martin Cowley 844
F1B Four in the flyoff
1st Bob Tymchek 1673
2nd Michael Davis 1596
3rd Mike Mulligan 1592
4th Rich Rohrke 1513
5th Bill Booth 1314
F1C Didn't write the scores on the copy of the sheets I made - the
overall CD has them. I'll get them and forward the scores. Only a 35
second spread from 1st to 4th (four in flyoff). One flight, 10 min max -
all very, very close!!
1st Randy Archer
2nd Guy Menanno
3rd Terry Kerger Terry very well could have won it; DT wouldn't
run any longer - still had some 25-30' when it DT'd
4th Daryl Perkins
5th John Warren
F1G Two in the flyoff - one flight determined the winner
1st Bill Gannon 742
2nd Jack Emery 723
3rd John Pratt 577
4th Paul Herbst 549
5th Gus del Castillo 545
F1H Three in the flyoff; one flight determined the winner, 10 min
max. Four in the flyoff.
1st Lee Hines 789
2nd Mike McKeever 777
3rd Norm Smith 724
4th Bob Norton 474
5th -------------
F1J Five of six flyers in the flyoff. Very interesting flyoff;
three dropped the first (4 min). Guy was long - didn't DT and went near
to 46, but got back. Had a slightly broken model. Repaired, he got the
round off with less than 30 seconds left. Ed Carroll's 6 minute went
off without a hitch. They both made the 6 minute; Guy was very, very
long coming back - less than three minutes left in the 8 minute round.
Ed had waited, in case he didn't have to put up the flight. He did, and
Guy got off first, very clean and high. Ed flooded a couple of times,
but got the model off with about a minute in the round. Though Guy
seemed to get higher and the air looked really good at first, Ed's model
hung on longer for the win.
1st Ed Carroll 1490
2nd Guy Menanno 1397
3rd Dave Shirley 928
4th Ken Happersett 814
5th Tony Roberson 757
Harry Steinmetz of the Orbiteers was to be FAI CD, but had surgery
recently, so I took it for him. The FAI flyers made the job of CDing an
easy one; it was certainly my pleasure to have had the opportunity to
serve.
I believe Don Bartick, our SDO CD overall, will do a full write up for
the Digest. I'll do a more in-depth one on these events for him to use
as well.
Bob
Tips on tips
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Since we all have computers why not us them?
1. With he wing level. measure the tip dihedral angle,
2. Hold the tip down on a flat bed scanner and scan using the OCR/ trace
function, thus making a line drawing of the flat tip.
3. Save as a .dxf file and export to Autocad. (or save it to a floppy
and take to someone with CAD on their computer.)
4. Scale directionally in line with the span by the cosign of the
dihedral angle. This will shorten it to the projected area.
5. Using the CAD calculate function, determine the area of the tip.
This works with elliptical tips, round tips, Hoerner, Schuller and even
square tips(?) to any accuracy you need up to 1/1000's
of an inch. (or square decimeters or what ever).
John O'Dwyer
Reference to curved wing tips:
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The .7854 formulae was the one that I have always used, and it seems to work
out OK. It was published a long while back in one of Frank Zaics books,
"Model Glider Design" if I remember correctly. I suspect that's what Carl
Goldberg used in his calculations.
Thermals,
Harry Barr.
Super Max....
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I, for one, cannot rally 'round the "Super Max." If the round is flown in
the morning, but is still 1 to 1 1/2 hrs. in length, then it isn't
necessarily a still air round. Most will wait to the end of the round in
hopes of catching a thermal. So then what you have is a long max in thermal
conditions. What does that prove?
And wasn't too much performance/too small of available fields in Europe
given as one reason to reduce rubber weight in F1B?
Will somebody please identify these organizers who complain about big
flyoffs? What are they doing running contests in the first place....In FAI,
flyoffs are the fun part.
Bill Shailor
Bunting Good Summary
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Mr SCAT,
Thanks to all those who have replied to my questions on
bunting. In order to move things forward some more I
thought I would offer a kind of summary and pose some
further questions for the curious.
>From the replies I got the following seems to be the
general view :-
1) To get maximum height you need to use the energy in
the model at launch efficiently. This means no sudden
manoeuvers after release.
2) The angle the model climbs at should be set without
changing the tail angle after release but could be
altered by hook position or aerodynamic (section)
changes.
3) Shortly after release (less than 0.2 seconds) the
tail should be dropped to a minimum drag configuration.
4) The bunt should not be sudden but have a definate
time associated with moving the tail down.
5) The use of a fast glide is highly recommended to
damp out any stalling tendency.
Not that isn't how everyone does it but I would suggest
is used by a majority.
Thinking further, it could be proposed that the most
energy efficient climb would be truely ballistic with a
single tail setting after pitch up but I don't see
anyone trying this. I guess the closest is Van
Wallene/Limberger.
Of course there are other model classes out there that
have a similar problem so can we learn anything from
them ? I'm thinking about RC HLG and F3B. So to pose
some more questions :-
a) Anyone know why RC HLG's don't climb vertically
after the discus launch but at maybe only 60 degrees ?
b) What are the big RC glider guys doing now ? Last
time I saw them they were gaining energy by diving with
the towline attached then pitching up to a vertical
climb followed by a sharp bunt. Is this energy
efficient and does anyone fancy trying it ?
EoB
Poitou
========
Woodhouse
I found the format at Poitou more than acceptable. I do not like the long
first max. The long first flight is a contest killer. Drop this max then
you might as well drop out of the contest. It is a long way to go and a lot
of expense to find that you are dead at the start. If there is a breeze at
the start you may well have a long hard retreive at the wrong end of the
day, putting your back against the wall before the day has really started.
The first round super max will reduce entries and that is not what is
required.
The event should build to a climax. We don't need all those 3 minute rounds
to sort the field we can start the 5 minute round in the last round. fly
this to 5 if you are clean if not go for 3. The next round we go for 7.
This worked well in France.
Curved surfaces
===============
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> Rodger> What ever happened to the old adage of multiplying the chord
by the span and multiplying that by .7854?
> Thx Don.
Don,
I think Roger C. was saying is that the formula is not that accurate if
the surface is not a true ellipse. Anyone can make a slightly fattened
ellipse and gain a few free squares. Martins card board idea is probably
the simplest but requires an accurate scale, and some easy way to get an
outline of the projected surface. Carrol Allen calculated the area under
the curve when testing Wake motors using that method. To increase
accuracy, he would cut out and weigh a square piece to a known
dimension out of the same paper or cardboard as the test piece. This was
to calibrate the paper as to gms. per sq in., and was done with every
new batch of paper to eliminate variations in paper weight.
Bob Lipori
Extended Max
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May I add that I was not involved in Poitou organisation/decision.
I nevertheless appreciated what they did.
Bernard
More area of funny shapes disiderata
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Rog,
For my Big AL, Li'l AL, Baby Al F1A's(design
in colaberated effort with Don Zink and Vasily
Beschasny, BTW) the ear shape of the wings has
swept LE and scimitar pointed TE, ala Perfesser
Geo. Perryman.
Big Al was the first of the series to be made and
the unique shape caused me to try various calc methods, since it is not
eliptical nor parabolic
that I could tell.
Then Jim Parker reminded me of the card trick:
I took a flat piece of cardboard, cut it to the
chord and span of the panel, weighed it, then cut
the shape from it and weighed it again.
Dividing the shape weight by the rectangular weight
gives a factor to figure the area.
As Mike Seagrave related, to find projected area
do the proj span/flat span calc and multiply with
the flat area.
I back-checked by drawing the proj area shape, then
picking station points along the span, measuring chords and transposing
to the flat span and it was
very close to the "count the squares" or other ways.
BTW, I found the factor was .79 for Big Al and Buntero tip shapes.
My revery was shocked when I found that the Li'l AL
shape did NOT calc out with the same factor!
It is/was more full-bodied, and had a .83 factor.
The Baby Al shape has a .80 factor, also being another unique shape.
So then I could take the chord and span of each
shape times the factor for that shape.
Naturally if you mod the shape,
you must recalculate its area.
Re Jason Magill's astute HLG wood comments(BTW, thanks for the nice
Sweepette plug),I tend to agree
that 6-8lb stock(although I will use C grain if it is strong) is a
better choice for when I had
a stronger throwing arm(Yes, I can still vaguely
recall that time, long ago).
I found that total weight in the 34-40gm range was better for thermal
working stability. Plus they did not tax the throwing arm as much as the
lighter jobs, & they stay in sight easier for you & your timekeeper!
Back to Issue 731, re Kevin Moseley's wing breaking
troubles: It is true you can never throw too hard,
but smoothness is very important for control, while
some folks seem to have a violent release, which
twists the bird into odd attitudes, just when you need the most control!
I blew my last launch in
yesterday HLG comp because I tried to over throw it.
To sum up: If you used a built-up structure for the
wing, I suspect a stress-riser situation occurred
at a joint nearby. If it was a solid balsa wing,
it was surely the weakest point, possibly wind
checked, plus you might try a bit higher wood
density. Also try for launching smoothly/cleanly!
Any questions?
Lee
Whoops
=======
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Subject : SCAT Electronic News
Roger,
The last two issues are off in their numbering. Those numbers were assigned
to issues last month.
Bill Bogart
.. you're right Bill ... they should have been 733 and 734 respectfully.
.................
Roger Morrell
