Setting up a V-tail

[stu78]

Not really Modeling Science, but I wasn't sure where else to put it for an educated answer :D

I just need someone to confirm that I have my V-tail throws set up correctly before I go fly. I am sure I have got it right, but I thought its better to check, as the plan/instructions don't give away any info and its my first v-tail. anyway...

UP elevator moves both control surfaces UP
DOWN elevator moves both control surfaces DOWN

That bit Im ok with, it the rudder that bothers me...


This is all viewed from the back.

RIGHT rudder moves the left surface UP and the right surface DOWN
LEFT rudder moves the left surface DOWN and the right surface UP.

I tried to imagine the elevator thows on a conventional elevator with a lot of dihedral! and the rudder throws as if a conventional (vertical) rudder had been split down the centre and parted into a v.

I hope this makes sense, and that somebody can confirm it is how it should be.

I might be able to post some pictures if I didn't expalin it clearly enough.

Thanks

Stuart

[Andy W]

You have it right. For rudder, just imagine both surfaces bent up close to vertical, then they should move just like a regular rudder.. :)
..a

[stu78]

Thanks, I thought I was right, but didn't want to risk it :).

Stuart

[davidfee]

Yes, that's right. V-tails are a little strange to get used to but the way Andy mentioned to visualize things is simplest, I think. With a rudder input, the vertical lift components of each half of the tail will cancel, while the horizontal lift components are summed.

-David

[stu78]

Thinking about it a little bit too hard now...

won't the rudder inputs cause an adverse roll? I know the moment arms are small compared to ailerons, but it would still happen right?

Stuart

[davidfee]

Yes, in theory. This goes away with an inverted V-tail, but they are more prone to breakage on landing. Just build it and go fly. ;)

-David