SEN 896 - 20 Aug 2004
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SCAT Electronic News 20 August 2004 issue 896
Table of Contents
=================
RE: Ritz Continental response - Hines et al
Re: Air speeds - Wantzenreither
Turbulator info for Karl Hube - Hines
re: Martin Gregorie - Barnette and Woodhouse
pocket bikes. - Wilkinson
concerning airfoils and Profili - SkyKieng
Latest Sympo - Stalick
Drawer and Cutter - O'Reilly
Ritz Coords O'Reilly - Hines
RE: Ritz Continental response
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Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Hello Jerry and Sky,
I DO know of someone who made the Continental fly well, and that would be
Ken Happersett in the 60s.
In fact, I am fairly sure he won a Los Alamitos, CA NATS, probably '63.
If you look at the plans and read the article carefully, you should see why no
one flies them. They are seemingly a bitch to build, his way at least.
The big stab is Very hard to build down to his goal weight and the boom is long
, also difficult to keep light enuf.
And then the Wings! Very tough to find the exact density and grain wood.
Golden stuff, esp nowadays.
That said, It is a beauty, and someone MUST build one for the CLassic Towline
event.
I think I will finally build a design of mine, called Sharkie, which Dennis
Bronco made the '71 team by winning the Albuquerque finals.
It was inspired by Ritz' Continental, with tips like my Sweepette, so I have do
uble inspiration to crank one out for next year.
Ciao,
Bitting off a bigger chunk,
Leeper
----- Original Message -----
From: This email address is being protected from spambots. You need JavaScript enabled to view it.
To: J. Barnette
Cc: Lee Hines
Sent: 8/20/2004 12:28:47 AM
Subject: Ritz
Jerry, I'm not sure why it was not more widely flown. One who might have a vali
d opinion would be Lee Hines.
Lee was looking for Ritz stuff a couple of years ago I sent him a photo -- tha
t was reproduced in an NFFS Digest -- of Gerry holding the Continental at the
70's finals.
----- Original Message -----
From: J. Barnette
To: This email address is being protected from spambots. You need JavaScript enabled to view it.
Sent: Thursday, August 19, 2004 8:56 PM
Subject: Re: good grief!
> Gerry and had a friendly wager going
Bill,
Speaking off Ritz and his Continental... I have heard that Gerry was the only
person who could make a Continental fly well. Do you know if this has any trut
h and what is your opinion on it? The Continental is such a beautiful model, a
nd with the Classic Towline event, well...
Thanks,
Jerry Barnette
Fredericksburg, VA
Re: Air speeds
==============
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
----- Original Message -----
> Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
> I need to know the airspeed (m/sec). I would be grateful if others could
advise what airspeeds they believe are typical for FF models, on the glide
an under power.<<
Glide of 3 Coupe-d'Hiver of the class 100 g :
wing 12 dm2, various wing sections, measured by rho= 0.120 : 3.51 and 3.85
m/s.
Wing 21 dm2, stab 3.3 dm2, 102 g, by rho= 0.113 : 2.80 m/s
Wakefield climb beginnning, 16 + 3 dm2, 16 strands Pirelli 1/4", instant
thumb release mechanism, filmed with camera 8 mm in 1983 (45 frames per
sec):
time 0 s : 11.6 m/s
time 0.3 s : 12.4 m/s
time 0.5 s : 12.5 m/s
time 0.7 s : 12.3 m/s
Good luck. JW
Turbulator info for Karl Hube
=============================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
There has been a lot of material written on turbulators Karl.
If you get this years' NFFS SYMPO Hank Cole has an airfoil article with turbs l
ocated on some, if not most.
But you could spend a heap of money and time buying and reading various
tomes.. .and for what?
Confusion, I say, is probable until you actually do on the wings field flight t
esting in definitive, real time action.
If you trim a glider, A or H F1 types, then add a turb and hand glide it. If it
goes slightly faster and sinks just a bit more, then the turb is working. Add
a bit of up elevator and glide again. If OK, tow it up and check for how the g
lide responds. If you notice more bouyant, quicker stall recovery from gusts, t
hen it is about as good as can be expected in my experience.
What I am saying is, put a turb[about .4-.6 mm thk at 5-9% chord for A, and sam
e or a bit thinner maybe, for H] and try it out.
Many gliders have been flown with turbs in that location and size, including th
e Sokolov.
I have never had a glider with that section, but a similar one I built had to h
ave a turb at 7% about .6mm high.
A tome by Dieter Althaus for Stuttgart University on airfoils [title: Profilpol
aren fur den Modellflug] shows the Sokolov with a turb, but I can't read German
to know what is written. It relates to wind tunnel test of many profiles, as
does the Schmitz book from the '40s.
Ossie Czepa ['51 A2 World Champ] wrote a fine pair of articles in Aug & Sept '5
6 MAN which have turb comments and refs to Schmitz's book.
I recommend finding it for many reasons.
Gene Wallock should be able to copy Czepa's articles for you.
His email: This email address is being protected from spambots. You need JavaScript enabled to view it.
Hope the above is of use to you.
Yours for better airflow,
Leeper
re: Martin Gregorie
======================
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Not everyone knows Martin. So rather than sending a bunch of updates to
the group, it makes more sense to send info to his concerned friends.
Send me an e-mail if you would like to receive updates.
Jerry Barnette
This email address is being protected from spambots. You need JavaScript enabled to view it.
Fredericksburg, Virginia
Martin Gregorie
===============
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Guys
Update re Martin.
Martin is standing up well to the operations and is making good progress.
He remembers nothing of the accident but is starting to analise what went
wrong. He has asked for a computer! So the e-mails will start to flow
again.
For those wishing to send direct messages and cards etc to Martin; please
send to his sister:
Martin Gregorie
C/o Jane Berisford
Ridley House
Cold Aston
Cheltenham
Gloucestershire
GL54 3BJ
UK
Thanks to all who have already shown their support.
Michael J. Woodhouse
pocket bikes.
=============
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
roger.
i came across theese trhe other day.
thay are small 49cc motorcycles.
they hace electric start two speed transmissions and
centrifical clutch.
they get up to about 35 mph.
the price is four to six houndred dollars.
web site is scooterfactorydirect.com
this is in dothan al but i am sure you could find them
in any good bike shop in the country
who knows theese might be ok for chaseing freeflight
models.
thx don.
[My authority on wheeled toys, Randy Weiler reported that they were
somewhat unstable]
concerning airfoils and Profili
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Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Dear David, welcome to the wonderful world of Profili!
I spent several months glued to the computer fiddling with airfoils in
trying to find the perfect airfoil. I gained about 15 Lbs. of fat and
some limited ideas about airfoils.
Here is my admittedly slanted view on things.
For an high AR F1C use about 50 to 55 K in the glide. (I now favor a
5.7" chord. Last year's design has a 3 meter wing with a chord of 4.7"
It has a wonderful glide but I now assume that 10K reduction in Re
considerably degrades the potential airfoil performance )
Try 40/45K for the Wakefields...of course a tapered platform screws
things up. It may be -- according to one surprising mathematical
analysis -- that the most efficient planform for low Re is 80%
rectangular with short, tapered tips. Doesn't look very elegant but may
be the best aerodynamic approach. Accordingly, my Folder wings have a
basically rectangular planform and that simplifies things in assuming
an Re because I ignore the short tips.
Getting down to 30K the analysis really gets flaky. Take readings with a
grain of salt.
There are a lot of booby traps in the program that you will have to
learn to circumvent. One thing to watch out for is the "smoothing"
function; that can cause a complete computer overhaul of the airfoil and
turn it into a monstrous deformity. Frustrating. There are various ways
of modifying the airfoil..some will backfire. In particular the
"graphic" method can bite you in the butt. You will just have to be
patient and learn what will work for you. If you are just feeding in
stock airfoils then there is generally no problem... but then that is no
fun.
You will be surprised by a lot of things, including the fact that many
of the supposedly great airfoils don't look so great. Another surprise
is that thinning and reducing the mean camber doesn't always help the
performance at the lower Re.
And according to some experts the Profili figures for max CL may be
overly optimistic.
I find the program # 4 the handiest for comparing airfoils. The Max L/D
will be pretty close to the one giving the maximum power factor for min.
sink. Incidentally, You can get a quick ball park read on the polar by
laying a straight edge from the "0" location at the left to intercept
the salient high point of the CL curve.
For the CD on a power ship in vertical climb you want to look for the
reading at zero lift...which will NOT correspond to the lowest CD for
the airfoil unless it happens to be a symmetrical section. A compelling
reason for using a folder or flapper -- or better yet a combination of
both -- is that speed and duration are mutually exclusive.
Figure around 250 + for an F1C in the climb.
Experiment with the various features in the tool bar as that will give
you a better grasp of things beyond quickly glancing at the polar.
The optimum pure glide airfoils I empirically derived from Profili share
a mean camber of over 7% with a maximum thickness of about 4.5% at the
18% chord. The thickness back of the 50% position should be approaching
0%...looking much like a Jedelsky section. Small changes in the nose
configuration doesn't seem too important. The "flap" angle of the last
10 or 20% can make a big difference in the CL. Just an almost
imperceptible change of a degree or so can be surprising. The mold I
made is not that accurate so I just cross my fingers and hope.
Accordingly, my new F1C wing design is essentially -- from nose to tail
across the top -- a molded curved plate of light carbon cloth on the
bias. The spar is a small diameter high tech carbon arrow shaft. A
similar molded carbon sheet caps off the bottom in a half-assed "D" box
to around the 55% spot. Stock carbon rib-capping material is added to
the top and bottom of the single surface every inch or so to provide
chordwise stiffness in the rear. The stiffners are not quite as extreme
as the corrugations on an Iron Annie Junkers 52, but employ the same
principle.
When the wing is folded the rear section of the wing bends under
compression to form a low-drag NACA look-alike 0013 symmetrical
section...that, according to Profili -- and taking into consideration
the reduced area -- yields only 25% of the drag of an ordinary F1C wing.
Without the flexible chord feature the resulting symmetrical section is
ill-formed and about 20% thick with a relatively high profile drag.
Forward turbs seem to hurt. Try turbulators at about 60/ 67%. The
improvement may be only a figment of the computor's imagination, but it
sure makes for a better looking read-out.
Good luck!
Bill Gieskieng
Latest Sympo
============
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
2004 NFFS Symposium now available.
To all readers of SEN, the brand new 2004 Sympo is now available from NFFS
Publications Services. This issue, edited by Walt Ghio, carries on the tradition
of past Symposium publications and contains 180 pages of research, features,
Nakashima cartoons, Models of the year, and Free Flight Hall of Fame
selections.
The cost is $25.00 per copy plus $4.00 postage in the USA. Overseas postage
via Global Priority mail (where available) is $9.00. Payment is accepted via
check, money order or credit card. Credit card payments incur a service charge
of 5%.
Order from: NFFS Publications Services, PO Box 1775, Albany, OR 97321 USA.
Email
European customers should be aware that Ian Kaynes has ordered and will
shortly receive a goodly number of copies of the '04 Symposium for distribution
Bob Stalick
Drawer and Cutter
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Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
To Ron Borg,
Bob Holman and I do the sort of airfoil cutting you are seeking. With
adequate input of the basic airfoil, I draw up the ribs on CAD and e-mail
the files to Bob Holman, who cuts the ribs from wood to your specification.
Jim O'Reilly
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Ritz Continental coordinates
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Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Stations 0, .01, .025, .050, .100, .20, .30, .40, .50, .60,
.70, .80, .90, 1.00
Uppers: .005, .023, .034, .048, .068, .089, .095, .094, .089 .079, .067,
.051, .031, .008
Lowers: .005, .000, .003, .007, .014, .028, .040, .048, .053, .054, .047,
.035, .019, .000
>From 10-'60 MAN. Jim O'Reilly
Ritz section ref
================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Mario,
The Ritz Continental section is in John Malkin's Airfoil Book[rev edition 1981]
and Andre Schandel's Profil Book[ pub date unknown], respectively numbered 7,4
5-5,5G or 74555G.
The coordinates are identical, so if you find one, you have it, so you can stop
looking!
Ciao,
Leeper, the airfoil finder
Lee Hines
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............................
Roger Morrell
