Jet catapult scale postal

[Wout Moerman]

On the moment this is still in the Corben dimer thread and I think it
is good to devote a thread to jet CLG.

Good to see the thread on HPA is opened and updated: [url]http://
www.hippocketaeronautics.com/hpa_forum/index.php?topic=529.0[/url]

Today I tried my Fokker S.14 CLG. Most flights were around 10 seconds
but 2 timed flights were 20 seconds. It is hard to convert the launch
speed into height instead of loops. I used 3/16 rubber and I've got
the feeling that using 1/4 just will give more loops and not more
height. But I'm sure I can improve the climb eventually. BTW, this is
just an report of the trimming flights, official flights will be made
later.
Maybe I'll make a non-scale CLG to practice trimming and launching.
But these often have much more dihedral than scale CLG's and that
probably makes the transition a lot better.

[Bernard Guest]

Hi Wout...try the following trick (taken from FF power endurance notes in a Zaic yearbook) set the c.g. farther back till the model has a zero stab incidence (or even slightly positive) but still floats in the glide (you will have to remove nose weight)....this should keep the model from looping out on launch. When she goes over the top the rearward cg takes over and the glide should be ok.....hope this works (I will check my Zaic year book to make sure I have this correct).

Bernard

Bernard Guest

Assistant Professor of Geology

Section Geology

Dept. of Geo- and Environmental Sciences

Ludwig-Maximilian University

Luisen Str. 37, 80333 Munich

Fax: 0049 89 2180 6514

Tel.: 0049 89 2180 6713

b.g...@iaag.geo.uni-muenchen.de

[Wout Moerman]

Bernard, you are refering to a 0° - 0° trim which indeed should help
the climb enormously. Trouble is that the transition to the glide is
critical and sometimes the model comes down in the same way as it went
up: vertically and fast! I hoped to make a model which is easy to
launch so my kids and others can launch it. I hope to get it trimmed
to achieve a spiralling climb and some launches already went like that
but I have to figure out how to do this reliable.

Wout
-

[Bernard Guest]

Yes I recognize the problem...I was thinking +1 on the wing and zero for the stab or something like that....maybe with a bit of up elevator to get a big half loop and rollout at the top. The launch would be at and angle of 30 degrees up from horizontal. Basically i think we need to find that critical setting that balances a decent high speed flight path with a reasonable roll out and glide. A 2-2 or 3-2 setting works well for hand launch where the launch speed is low but for high launch speeds I suspect 2-1 or 1-0 and a 50% cg will be required....I guess we will have to experiment and learn!

B

Bernard Guest

Assistant Professor of Geology

Dept. of Geo- and Environmental Sciences

Ludwig-Maximilians University

[Wout Moerman]

My Fokker has 0° on the wing and -1.5° on the stab. I first will try a
Gurney flap on the TE of the stab which should result in a bit of down
elevator at high speed. These Gurney flaps function more effectively
at high speed so the effect should be reduced in the glide. If this
doesn't help I will reduce the stab incidence.
BTW, "+1 on the wing and zero for the stab with a bit of up elevator"
means you skip the zero for the stab doesn't it? It probably equals
the 1.5° difference I used.

Wout

On 18 jun, 11:54, Bernard Guest <b.gu...@iaag.geo.uni-muenchen.de>
wrote:

> b.gu...@iaag.geo.uni-muenchen.de

[Pit]

Hi guys,
just posted a pic of my SAAB Viggen cat glider on the HP thread, that
I built a few (DON'T ask how many) years ago. I actually made a whole
trunk-full and sold them quite successfully. The wing loading is
high enough so that it would take a Taft Trash Mover to make it go
OOS, but proved a very nice break from the rigors of R/C flying. I'll
build another for the cookup with a bit more wing area.

Cheers, Pete

[W.Mo...@amd.ru.nl]

Now I don't know which question NOT to ask: how many Viggens did you
build or how many years ago.... It is a nice looking glider!
Any thoughts how big you will make your next Viggen? And can you say
something about the trim? What is the incidence of the canard wing and
the main wing?

Wout

-----Oorspronkelijk bericht-----
Van: fac-e...@googlegroups.com [mailto:fac-e...@googlegroups.com]
Namens Pit
Verzonden: donderdag 19 juni 2008 1:06
Aan: Flying Aces Club Europe
Onderwerp: {Flying Aces Club Europe} Re: Jet catapult scale postal

[Bernard Guest]

Hey guys,

So if you take a look at the HPA catapult thread you will get some interesting insights on cat models ...see http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=184.msg1445#msg1445 by Kev in particular. He favors the 0-0 incidence setup for cat models and 55% cg position. 

B

Bernard Guest

Assistant Professor of Geology

Dept. of Geo- and Environmental Sciences

Ludwig-Maximilians University

[Pit]

Hi Wout,
I made about 100 models and they went like Thüringer Bratwurst at DM
10 ready built and trimmed with catapult. Most were bought by adult R/
Cer's who flew the wings off of them (literally). For the new one,
the only thing I'll do (at first) is to increase the span of the delta
one inch per side. I may have to enlarge the canard a bit.

The main wing is at 0° and the canard at +1° (leading edge higher) and
balances just aft of the first break of the double delta. weight of
the models are 7.50 grams. The main wing has a slight airfoil sanded
into it with the trailing edge thinned to almost a razor edge FROM THE
BOTTOM, giving it a slight reflex. The plane just didn't want to fly
with a 'standard' foil. The canard has a regular 'foil (bottom
flat). The fin has a n airfoil sanded in on the right side only for
left turn.

flight tests indicated that a bit more down canard (LE higher) or a
bit more reflex is needed and a breath more left rudder for a good
transition and glide.

I'll try to dig up the plan. Since it is a published one, I don't
think I can legally post it to the forum,but I will scan it and send
it to whoever wants one.

The WW F-18 was built box stock. I premanently removed the wing pods
as they continually broke off.

Cheers, Pete
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