Hi
Thank for answers so far.
I like the discussion, so any more ideas are welcome,
also if you have more tips or links to papers on this matter.
On the camera tip, I can say i was there :)
I have done several test, one is a motor stick on a holder,
where i put a prop to analize and i load a rubber. Then i take
pictures (many) with a camera and flash, so i get still images.
By looking thoise pics, you can see if propeller is flaring or
not.
I also film, and then when i play frame by frame (1/15 sec) I can
find instant RPM on diferent moments of discharge. Note that this
RPM are different from a plane flying. They are lower,
flying RPM are faster.
Later I build a motor stick and places a servo motor and a rubber.
With a variable resistance I manage to get the desired RPM. Later I
take pics and also film with the camera.
Using same configuration and diferents props I can compare one against
other. Also I can balance them, chack if shaft is aligned,
and if the reverse-S hook is aligned too.
All this is for a local national category, called P-25, and share
the "flat propeller" rule with yours A-6. But we are not limited
on thickness.
On next link you can see photos and a description (in spanish)
of the device, but sapnish descriptionis almost the same i explain above.
http://il2fb-bellum.com.ar/indoor/forum/viewtopic.php?id=17
Some time ago i think on cuts, but I have the same problem,
that maybe is not legal. I have built arround 20+ props with
different grain orientation, diferent spar length, more flexible,
less flexible. But i do not have any conclusions. Its a nightmare.
For me, now, i do many test, but when i go to fly the have some
propellers that works fine, other not.
Now, im still looking on more about this flat propellers.
Ignacio.
PS: Just for information P-25 rules are:
- wing span max: 25 centimeters
- Wing chord max: 7,5 centimeters
- Tail area max: 50% of wing
- Maximum motor stick length 16 centimeters measured
from the thrust bearing face to the rear hook.
- Min weight: 2 grams without rubber
- Propeller max diameter: 16 centimeters.
Blades to be flat, no forming no twist or camber.
- only balsa wood and cement, No high tech materials, exeptions:
prop shaft, prop bearing and rear hook
- no microfilm to cover.
Received on Wed Apr 12 2006 - 18:02:36 CEST