hello a question

leee

2007-08-31 00:55:30 UTC

Post by lina maria perez perez
My name is lina and I am new in this thing but I'm trying to learn, now I'm
trying to make the model of an helicopter that I need for my project, but
there are some things that I don't understand, this is
fuselage: This defines a tubelike structure. It will be given an even
mass and aerodynamic force distribution by the solver. You
can have as many as you like, in any orientation you please.
ax,ay,az: One end of the tube (typically the front)
bx,by,bz: The other ("back") end.
width: The width of the tube, in meters.
taper: The approximate radius at the "tips" of the fuselage
expressed as a fraction (0-1) of the width value.
midpoint: The location of the widest part of the fuselage,
expressed as a fraction of the distance between A and
B. I don't know how to define my fuselage, I know that the helicopter have
full lenght of fuselaje=1220mm(48.03'') and full width
fuselage=140mm(5.51'') (The helicopter is an aeromodel titan raptor 50) but
don't know how to relate it, the part that I have most confuse is in
ax,ay,az: One end of the tube (typically the front), bx,by,bz: The other
("back") end. I don´t know how to made this part. and all, haw I say I'm
new in this but I hope that you can help me.
Thanks a lot.
LINA.

Hi Lina,

regarding fuselage elements in YASim, think of a tube, or ellipsoid, with the
centers of the two ends of the tube defined by the ax,ay,az & bx,by,bz
params. The ax & bx params define the length of the tube. The ay/by params
specify the 'yaw' of the tube, or whether the tube is angled to the left or
right of the central axis of the aircraft and az/bz specifies the pitch of
the tube - whether it's tilted up or down.

The width param specifies how wide the the fuselage is (the assumption is that
the fuselage cross section is circular, or approximately so)

The taper and midpoint params are a little trickier to get your head around
and less obvious to understand - at least I find it so:)

I don't see how these two params can be separated as taper on it's own only
seems to allow for, at most, a sort of B-29/Boeing-377 type fuselage, which
compared to most aircraft is not tapered at all. However, If the fuselage
taper is related to the midpoint then we can get asymmetrical ellipsoid type
egg shapes, which make more sense. If the midpoint is placed forward of the
midpoint of the longitude axis we'd get a tear-drop type shape, with the back
of the fuselage trailing to a point, and if the midpoint is aft of the
midpoint then we'd have a reversed tear-drop shape, with the 'thin' end
leading.

If this is so, and I'm not sure I've got it right;) , the radius then
specifies the curvature of the ellipsoid. Referring to the taper element for
wings, I would say that a taper of 0.0 would produce a cone (or pair of
cones) with the base of the cone(s) at the midpoint, and a taper of 1.0 would
give a perfect egg-shaped ellipsoid.

For your aeromodel titan raptor 50 I'd disregard the boom entirely as it's so
small that it would have little aerodynamic effect and therefore place the
midpoint at about 0.9 i.e. nearly at the back of the fuselage. I'd guess at
a value of about 0.7-0.8 for the taper, favouring the lower end of that
range.

Perhaps AndyR might see this thread and clarify - it's something I've never
been that sure about but working on the basis I've outlined seems to have
worked for the fixed wing aircraft I did.

LeeE

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