# Rocsim Question

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#### cdma77

##### Well-Known Member
I am new to Rocsim and it is asking for the slope angle for the fin. Could somebody please explain how to get this ? I can calculate the slope with a simple formula, however this can't be what the program is asking for. I am doing this as a scratch build, so I don't have the number in my hands. Are they asking for the delta between the angle and 90 degs ?

Thanks,

Jeff

i think if you have a point in the middle of the root edge of the fin and connect it to a dot in the center of the tip edge, that will give you the sweep angle relative to the body tube...

Originally posted by Elapid
i think if you have a point in the middle of the root edge of the fin and connect it to a dot in the center of the tip edge, that will give you the sweep angle relative to the body tube...

Wouldn't that be 90 degs ?

Jeff, the sweep angle is simply the angle of the "leading" edge of the fin in relation to the body tube. zero would be square to the body tube , a negative value would be forward swept.

Elapid, what you describe sounds like the mid- chord. tho I'm not positive

of sweep angle would give you the entire FIN sweep, which may or may not be the same as the leading edge angle.

take a theoretical fin with a jagged leading edge... which angle do you choose? How about a cloverleaf shape?
heart shape?

I know what your saying but it doesn't seem to work that way in rocksim.

I grabbed a tube and went to the fin designer screen (simple or eliptical fin)

I see that when I change the tip cord or the root cord the sweep angle number(and the leading edge angle) never changes...nomatter what shape I make the fin
the leading edge remains the same unless I change the sweep angle
If a line runs from the center of the tip cord to the center of the root cord to determine the sweep angle. this can't be true.

what am I missing?

looks like rocksim really means leading edge sweep angle rather than fin sweep angle/

actually I thought your interpretation was the right one ,
cause thats the first I've ever messed with that screen.
well atleast we figured it out.

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