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Building Tips and technical articles. => Building techniques => Topic started by: Paul Taylor on June 18, 2011, 08:22:14 PM

Title: Rudder airfoil what side?
Post by: Paul Taylor on June 18, 2011, 08:22:14 PM

If I wanted to sand a airfoil on my rudder what side do I sand it on?

Inboard?

Title: Re: Rudder airfoil what side?
Post by: Damian_Sheehy on June 18, 2011, 08:40:04 PM

Paul,

Do you mean the fin and rudder combination?

If so, the outboard side should be flat. The lift is generated on the curved side, we need lift to pull the tail inward in order to point the nose outward . You may still need some offset. I can give you data for the Nobler fin/rudder if you don't already have them. That may be a good starting point.

Your sketch is correct.

Damian

Title: Re: Rudder airfoil what side?
Post by: Paul Taylor on June 18, 2011, 09:42:33 PM

Thanks!
Now let me find my sand paper.

Title: Re: Rudder airfoil what side?
Post by: Wynn Robins on June 18, 2011, 11:46:00 PM

why do you want to airfoil it?    doesn't achieve much

Title: Re: Rudder airfoil what side?
Post by: Andrew Tinsley on June 19, 2011, 11:41:48 AM

Not everyone is a top notch Nats winner. They don't want trim factors that alter with speed. Your every day Mr Modeler can benefit from a goodly amount of engine outthrust. They wouldn't notice the speed / trim difference, but the extra out thrust can be mighty useful in marginal situations.

Regards,

Andrew.

Title: Re: Rudder airfoil what side?
Post by: Wynn Robins on June 19, 2011, 02:06:51 PM

but an airfoiled fin creates YAW - not out thrust

you dont want additional Yaw - it is another trim item to compete with.   

Title: Re: Rudder airfoil what side?
Post by: john e. holliday on June 19, 2011, 03:23:39 PM

All but one Nobler had the airfoiled rudder.  Never noticed any problems.  The ARF Nobler did not have the airfoiled rudder. H^^

Title: Re: Rudder airfoil what side?
Post by: Wynn Robins on June 19, 2011, 06:36:25 PM

Quote from: john e. holliday on June 19, 2011, 03:23:39 PM

All but one Nobler had the airfoiled rudder.  Never noticed any problems.  The ARF Nobler did not have the airfoiled rudder. H^^

true doc - but things have come a long way since the nobler.

Title: Re: Rudder airfoil what side?
Post by: M Spencer on June 20, 2011, 04:57:19 AM

If you made LE 1/8 across , 1/16  radius , on the centreline , and the tail post is equal about the centreline ,
 itll be a bit offset enough.

The yaw from the offset offsets the yaw from the prop , so the yaws neutral , yawn . n~
If its got right , itll stay neutal throughout the speed range , and help hook it out ( like a
assymetric span ) if you get a big nasty gust try and ruin youre day, can help to leap back
though. LL~ :o ;D