Cox Engines Forum
You are not logged in! Please login or register.

Logged in members see NO ADVERTISEMENTS!


off topic air foils - Page 2 Cox_ba12





Log in

I forgot my password

Search
 
 

Display results as :
 


Rechercher Advanced Search

Cox Engine of The Month
September-2022
fredvon4's

Hot Tee Dee .049 featuring a Turbo Head and exhaust collector



PAST WINNERS
CEF Traveling Engine

Win This Engine!
Gallery


off topic air foils - Page 2 Empty

off topic air foils

Page 2 of 2 Previous  1, 2

Go down

off topic air foils - Page 2 Empty Re: off topic air foils

Post  cjuliano Wed Jan 11, 2012 6:12 pm

andrew wrote:
John Goddard wrote:I think you need to give the motor a fair bit of down thrust, it'll just keep looping otherwise.

John's made a very valid point.

If your motor is mounted as shown in the picture, the plane will be uncontrollable. Downthrust, or having the motor pointed downward relative to the angle of attack (the relative angle of the wing as the plane moves thru the air), is necessary to keep the aircraft from continually trying to climb, especially with high lift airfoils. Within a specific speed range, lift is related to the square of the velocity, so it goes up quickly as the speed increases. Before RC, freeflight planes had to be trimmed to fly on their own without pilot input. Downthrust was used as one of the trimming components. When under power and flying faster, the downthrust worked against the lift generated by the wing to keep the plane from ballooning or pitching up. It would be adjusted so the plane would fly in a slight climb. When the motor quit, the speed dropped off, as did the lift. But without the motor trying to pull the nose downward, the plane would be set up to fly in a fairly flat glide.

Downthrust is still used today on planes with lifting airfoils --- partially to compensate for lift to velocity squared relationship. When looking at your plane from the side, with the fuselage sitting as you think it will be angled in the air, the motor should be pointed slightly downward.

400g AUW is fairly light and the Surestart will haul it around quite well.

andrw
thanks I had no idea.
ill fix my engine mount then.
cjuliano
cjuliano
Bronze Member
Bronze Member

Posts : 40
Join date : 2012-01-09
Age : 32
Location : NJ

Back to top Go down

off topic air foils - Page 2 Empty Re: off topic air foils

Post  Kim Wed Jan 11, 2012 6:49 pm

Ditto to what the guys said...also, once you've gotten it going, don't be afraid to make fine adjustments to the engine's mounting angle using washers under the lower or upper mounting screws to continue fine-tuning it's behavior under power and in glide. You'll know you're close when it has a tendency to gradually climb under power, with a gentle transition to glide speed when the engine quits.

Ideally, the entire range of elevator trim you need should be just a few bleeps (or notches) up or down from center.

CG plays a role too, and I balance my planes for the glide, and adjust the angle of the engine for trim under power. This is just my deal, other guys may do it differently.

Kim
Kim
Kim
Top Poster
Top Poster

2020 Supporter

2021 Supporter

2022 Supporter

Posts : 8062
Join date : 2011-09-06
Location : South East Missouri

Back to top Go down

off topic air foils - Page 2 Empty Re: off topic air foils

Post  cjuliano Wed Jan 11, 2012 6:54 pm

thanks for the tip.
cjuliano
cjuliano
Bronze Member
Bronze Member

Posts : 40
Join date : 2012-01-09
Age : 32
Location : NJ

Back to top Go down

off topic air foils - Page 2 Empty Re: off topic air foils

Post  cjuliano Thu Jan 26, 2012 10:43 pm

can flat bottom air foils fly upside down
cjuliano
cjuliano
Bronze Member
Bronze Member

Posts : 40
Join date : 2012-01-09
Age : 32
Location : NJ

Back to top Go down

off topic air foils - Page 2 Empty Re: off topic air foils

Post  Mark Boesen Thu Jan 26, 2012 11:00 pm

Yes, with a enough elevator throw. Think about how a flat wing creates lift? Don't plan on doing a lot of outside loops though.
Mark Boesen
Mark Boesen
Top Poster
Top Poster

Posts : 3929
Join date : 2011-09-01
Age : 64
Location : Rockford, Il

http://groups.yahoo.com/group/049Collectors/

Back to top Go down

off topic air foils - Page 2 Empty Re: off topic air foils

Post  nitroairplane Fri Jan 27, 2012 1:45 am

cjuliano wrote:can flat bottom air foils fly upside down

Hes but for bat inverted performance or for any real aerobatics a symmetrical one it best.
nitroairplane
nitroairplane
Top Poster
Top Poster

Posts : 6956
Join date : 2011-04-11
Location : London

http://modeldieselengines.forumstopic.com/

Back to top Go down

off topic air foils - Page 2 Empty Re: off topic air foils

Post  John Goddard Fri Jan 27, 2012 5:46 am

With enough power and airspeed you don't nesesarily need any air foil, a tea tray can fly.

John Goddard
John Goddard
Diamond Member
Diamond Member

Posts : 2447
Join date : 2011-11-24
Age : 58
Location : Leyton North East London

Back to top Go down

off topic air foils - Page 2 Empty Re: off topic air foils

Post  microflitedude Fri Jan 27, 2012 8:55 am

John Goddard wrote:With enough power and airspeed you don't nesesarily need any air foil, a tea tray can fly.


+1.

I call it "flying by the prop"
microflitedude
microflitedude
Top Poster
Top Poster

Posts : 3417
Join date : 2011-08-17
Age : 24
Location : Columbia, SC

https://www.facebook.com/MiniCub?fref=ts

Back to top Go down

off topic air foils - Page 2 Empty Re: off topic air foils

Post  RknRusty Fri Jan 27, 2012 10:45 am

Brute force flying. That's what I've been accused of with my slat-winged planes like the Stuntman23. The slat wings do bare a lot of load during loops. And they keep it from descending too fast when the engine quits as long as you keep it nosed up a bit. I wonder how a control line fuselage with no wings except for a stabilator would fly. I've wondered but never tried it.

_________________
Don't Panic!
...and never Ever think about how good you are at something...
while you're doing it!


My Hot Rock & Blues Playlist
RknRusty
RknRusty
Rest In Peace
Rest In Peace

2020 Supporter

Posts : 10869
Join date : 2011-08-10
Age : 66
Location : South Carolina, USA

Back to top Go down

off topic air foils - Page 2 Empty Re: off topic air foils

Post  Sponsored content


Sponsored content


Back to top Go down

Page 2 of 2 Previous  1, 2

Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum