Propelers / Altitude
07-07-2002 | 11:27 PM
#1
Thread Starter
Junior Member
My Feedback: (2)
Joined: Jun 2002
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
From: Bogota, COLOMBIA
Propelers / Altitude
In my Extra 300 fot a 40 size engine. I am using a Supertiger 51.
with a propeler 12x6. I get aprox 10500 rpm. I live in Bogota - Colombia, wich is located at 2400 mt/8550 ft over sea level. There is not a lot of oxigen at this altitude. I prepare my own fuel, with out nitro.....
My plane fly's well, but I am shurly under powerd because of the lack of oxigen for combustion.
What propsize should I try?
No I am not adding nitro to my fuel..
NO I am not moving..
Thanks
Santiago Torres
with a propeler 12x6. I get aprox 10500 rpm. I live in Bogota - Colombia, wich is located at 2400 mt/8550 ft over sea level. There is not a lot of oxigen at this altitude. I prepare my own fuel, with out nitro.....
My plane fly's well, but I am shurly under powerd because of the lack of oxigen for combustion.
What propsize should I try?
No I am not adding nitro to my fuel..
NO I am not moving..
Thanks
Santiago Torres
07-08-2002 | 12:56 AM
#2
Senior Member
Joined: Dec 2001
Posts: 958
Likes: 0
Received 0 Likes
on
0 Posts
From: Punta Gorda, FL
Prop
Because the air is thinner, the plane has to fly faster to produce enough lift at a given angle of attack. I would try a smaller higher pitch prop that is sized to give a higher RPM. I'm not sure where the ST 51 produces peak horsepower but I'll bet it is closer to 12,000 RPM than to 10,500 RPM.
At such a high altitude you may have to use an even larger engine (or smaller plane) to get the performance you want.
At such a high altitude you may have to use an even larger engine (or smaller plane) to get the performance you want.
07-08-2002 | 02:19 AM
#3
Senior Member
Joined: Jun 2002
Posts: 126
Likes: 0
Received 0 Likes
on
0 Posts
From: St. Catharines, ON,
Propelers / Altitude
Relative density is probably about 75% at that height. If you don't wanna use nitro to restore power, then using a larger engine is a good choice. You'll need at least 30% larger displacement. The .51 seems about right. As for the prop, go up in pitch, don't change the diameter. Pitch doesn't affect rpm all that much and it even if it turns slower static rpm, it will turn faster once it's up to speed. A 12 x 7 should work well enough.
03-05-2003 | 03:38 AM
#4
Junior Member
Joined: Oct 2002
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
From: Santa Ana,
CA
Propelers / Altitude
I believe the recommended prop size for the Supertiger .51 is a 10x6. You can probably even use a 9.5x6 or 7.
I think some of your engine's underperformance is due to the oversize prop. That's a big prop for such a small bore.
Just my two cents worth.
Smithers
I think some of your engine's underperformance is due to the oversize prop. That's a big prop for such a small bore.
Just my two cents worth.
Smithers
03-09-2003 | 10:29 AM
#6
Member
Joined: Mar 2003
Posts: 57
Likes: 0
Received 0 Likes
on
0 Posts
From: Haslemere, UNITED KINGDOM
Propelers / Altitude
Interesting. At sea level my ST 51 turned a 12x6 APC (and also 12x6 Graupner) at 10,000 on 5% nitro (although I always run a bit richer than some of my clubmates).
10x6 is NOT a normal size prop for a 51; too small, too nosiy.
For comparison - best prop for my ST51 in a 5lb Acrowot was an APC 11x6 but it was too nosiy to meet our noise limits. On the 11x6 verticals were effectively unlimited. On the 12x6 they were adequate.
Mike
10x6 is NOT a normal size prop for a 51; too small, too nosiy.
For comparison - best prop for my ST51 in a 5lb Acrowot was an APC 11x6 but it was too nosiy to meet our noise limits. On the 11x6 verticals were effectively unlimited. On the 12x6 they were adequate.
Mike
