slow fly

[Ian Walker 2]

hi, I'm a new member plus I am not very experienced with the use of
computers and e- mail etc.
however I feel that this web site is something I want to be able to cope with. Not being a club member I have need this more than most.
Just to put you in the picture.
My first experience of model flying was a Keil Craft Ajax Wakefield
my dad built for me in 1947 he was a clever chap so it flew very well.
From then on I got the bug for life. On and off but always returned to it
In between times always keeping in touch through model magazines.

I do like to design and build my own models but my last attempt
just did do what i hoped for, and that is have slow fly ability.
This model had a 15% clark Y airfoil built up construction and as light as possible it flew very well but still quite fast.

So my question is what gives a model slow fly ability?
I apologise if I have not done this correctly and its not going to right place etc.But I have to make a start. Cheers Ian.

[David Ashby - Moderator]

Welcome aboard Ian, nice to hear from you.

Can you tell us a bit more as to what you're seeking. Slow fly is a term used for a certain genre of park-fly models these days - is this what you're after or do you refer to slow flying models generally?

David.

[Tim Mackey]

Hi Ian and welcome.
I am NOT an aerodynamics ( probably cant even spell it let alone "do" it !! ) expert but would suggest that you are not far off with your assumptions. There is a saying in modelling "add lightness" - and although true in most cases ( perhaps except when ballasting a fast glider for heavier winds ) never more so in striving for slow flight. Anything which adds weight will inevitably tend to increase the mass and therefore "sinkability" - which of course will increase the airspeed.
Nice big wing, airframe light, big slow turning prop on powered models, and small smooth control inputs, remembering also of course ( as so many pilots seem to forget ) on a powered model the throttle is a flight control too.
Good luck with your venture, and come over to the Orme some time and chuck yer glider off a very big hill !

[Ian Walker 2]

hi, thanks to dave ashby and timbo. Its so good to actually get a responce to my enquiry.Idid not think I would
I have a horrible feeling that The answer is not what I wanted to hear ie. dreaded wheight penalty. actuallly Timbo the model in question is electric power but thanks for the invite to your sloping site.
As I said I like to design my own models even if they are not always
successful.
The model in question is shoulder wing 4ft. wingspan and uses a
hacker A20-22L (which I must add exceeded what it said on the can)
and battery is the new flightpower E.lite 2100.Witch can deliver
13 amps to the motor driving a 10x6 aeronaut folder.This gives quite
some pull and has easily got 45 degree climb capability.
Anyway I think Its back to the drawing board.Perhaps I will have to build a feisler storch ( Don't suppose I have even spelt it correctly)and by what I have read its no simple model to build.
So weight is top priorty but, then the weather conditions play such a
big part when low on power. As always you can't have it both ways.
Thanks you for your response. The web site will be a great success I am sure. And yes dave RCM&E is my monthly magazine and I feel the best.And I would Like to pass on gratitude to Nigel Hawes who became a must read section for me on electric flight over the years.
Thanks again Ian.

[David Ashby - Moderator]

Thanks Ian, Nigel drops by on the forum now and then (especially on his EZE-Fan thread) so he should see this ...by the way (sorry if this sounds like I'm trying to sell plans!) but we had an electric Storch as a free plan a couple of years ago..you could get it from the plans service..

David.

[Ian Walker 2]

HiDavid,
The slow flying model I would like to add to my collection is realy a new avenue I want to investigate,I will have to look in my
RCM&E back issues for the electric storch. I don't feel I could design the likes of it on my own.It's my hope that with slots, slats?
Flaps it may be possible to have some authoritve power when needed and as Timbo said the throttle becoming more effective as a contol and not be just like A pico stick which I have got and soon lost interest with.
By the way I will be watching for feedback on the Kong Power lip'o
from al's models I hope they may bring out a lite version.
thanks again David and Timbo
Ian

[Tim Mackey]

Your Welcome Ian :) sorry i wasnt much more help :(

[Alistair Taylor]

Ian

I'm no aerodynamicist either, but I believe that what is needed in a wing profile for slow flight is a good dose of camber, i.e. (imagine
you're looking at a slice through your wing) the degree of curvature of the center-line of your wing (a line that is halfway between the top surface and lower surface) away from the chord line (a straight line joining the tip of the TE to the tip of the LE chordwise).

Your flat bottomed clarke-y wing has some camber (the center-line describes a curve above the chord line), a symmetrical wing has none (chord and center line coincide), and an "undercambered" wing (i.e. one that has a concave lower surface) has lots - the chord line may only touch the TE and LE, and not intersect with any other part of the wing profile.

Look up the wing profiles on any of the really capable free flight duration/glider designs for inspiration, e.g. Lanzo Bomber, KeilKraft Caprice, KeilKraft Chief (this is not my area...I'm clutching at stringers a bit).

This is a fairly simplistic description, and you'll find much better (and more detailed) elsewhere on the web, but for true slowflight ability I would suggest that you build another wing, perhaps bigger and lighter, with more camber.

Of course, flaps have the effect of adding camber (lowering the TE relative to the LE, so that the chord line drops below the center line) when you deploy them, thus enabling slower flight (they also add drag, making slower flight inevitable). So these would help slow things down with your current wing.


AlistairT

[Alistair Taylor]

OK, I checked my facts.

Lift and camber are very closely related - more camber generally means more lift.

So by increasing the camber of your wing, you're increasing it's ability to generate lift - so it will generate more lift at a given speed than a wing without camber. Which means you don't have to fly as fast to maintain height.

AlistairT