View Full Version : Fins for FAI on Stratus
Zilly
12-27-2005, 07:05 PM
What fins are most suited to FAI style flying there seem to be a number of different solid fins from MA which are the ones to go for??
z
WayneBrown
12-27-2005, 07:39 PM
Different organizations dictate a specific area to for the horizontal fin.
Try searching within whatever organization you are intending to fly within for the sizes.
In the US it would be http://www.modelaircraft.org/comp/0506Rulebook/rc-heli.pdf
Page 1 paragraph 2 states fixed horizontal surfaces up to 4% of the swept area of the lifting rotors
This may actually be the same as FAI international rules, but it's safer to check for yourself..
IF you are just 'sport' flying to the FAI routine, with the occasional 3D move thrown in, try the hollowed out fins.
I only use the Vertical fin, no horizontal.. made that change due to balance, and can't tell the difference in-flight.
So far it seems like the Stratus with the Tempest FAI head requires a little more than the standard horizontal fin. I am currently running the SAB Pro IIK fin. The standard fin seems to cause the model to pitch up just a tad so I went bigger and that seemed to help, at least so far. I'm not done trimming on it yet. For the Extreme head, I really don't have a clue.
Gordie
Zilly
12-28-2005, 06:32 AM
GM1 what vertical fin are you running ?
Dr.Ben
12-28-2005, 07:28 PM
The size of that horizontal fin is SO model, blade, head, and headSPEED specific. You really have to start with something "that looks about right" with your given set up, then adjust the size of that fin up or down until the model tracks with ZERO swash trim, hands off, in FFF at or near WOT with the head NOT bogging. On my Stratus, I needed a trimmed down version of the large SAB horizontal. Note that the fin size will vary from summer to winter, with the winter fin being a bit smaller b/c the air is more dense and places more pressure on the given surface area of the fin. THe ideal situation is to have a fin with some holes or slots in it that provided good cool weather trim with those slots open, and you then cover them up to provide more area in hot weather. For a vertical, I use either a skeleton or solid fin. It's not critical, though the skeleton fin does give the gyro less to work against in a crosswind.
Ben Minor
I am currently using the SAB lightwieght vertical fin.
Gordie