Elan trouble

[David Lockhart]

Jerry,

The MK bellcrank was certainly adds 1 oz or more to the tail, perhaps more
depending on what types of clevises and secondary pushrods your are using -
and such high tech tricky devices are not something you will find Dick
Hanson using.  And while glass/paint can be done with minimal weight gain,
it usually does add some weight (call it 1 more oz), and if the paint on the
fuse itself is heavy, that can effectively add 1 oz to the tail.  And the
actual weight of the stabs and rudder can pretty easily vary 1-2 oz,
depending on the builder (heavier wood, amount of epoxy used).  And, an
adjustable stab can add 1 oz.  Tailwheel assemblies could vary by as much as
1 oz.  Might be as much as 7.5 oz between different builders and hardware
choices.  That 7.5 oz equates to substantially more (as noted by others) on
the nose - maybe 15-20 oz.  Dump the bellcrank and take a close look at
linkage hardware and the tailwheel assembly - you might be able to pull 2 oz
off the tail (reducing noseweight by 6-8 oz).

- AND - on the front end - When the Elan was designed, a YS120 AC was
commonly used - that engine weighed in around 34-35 oz if my memory serves
correctly.  The current day YS 120s are, I believe, 1-2 oz lighter.
Unfortunate, but not too hard to see how 12 oz of ballast could be needed on
this plane (or any other).

I would absolutely move the throttle servo forward - bolt it to the bottom
of the tank floor just behind the firewall - this will effectively add 1 oz
to the nose.  You might also be able to move the RX and switch just ahead of
the LE of the wing - maybe effectively 1 more oz on the nose.  Those
changes, coupled with dropping 2 oz on the tail should get you to the point
of needing well under 4 oz (if any) on the nose.  At 9 - 9.25oz, the Elan
will fly extremely well.

Regards,

Dave Lockhart
DaveL322 at comcast.net


----- Original Message -----
From: "Jerry Wilson" <JWilsonJr at houston.rr.com>
To: <discussion at nsrca.org>
Sent: Wednesday, June 29, 2005 9:35 PM
Subject: RE: Elan trouble


> Jim,
>
> I don't know why it is tail heavy.  I was very surprised.  CG is noted on
> the plan. Fuselage is painted as are horizontal stab, elevator, and rudder
> which were also glassed.    Could be my glassing and paint job is heavy
> although I would not have thought so much weight could be attributed to
> this.  Rudder and Elevator servos are over the wing trailing edge as per
> plan.  Battery pack has been moved to the firewall.  Used Central carbon
> fiber push rod for elevator to MK dual bellcrank and MK control horns.
Push
> pull cable on rudder.  Receiver and throttle servo are about at the CG.
>
> Jerry
>
> -----Original Message-----
> From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]
On
> Behalf Of Jim Ivey
> Sent: Wednesday, June 29, 2005 5:24 AM
> To: discussion at nsrca.org
> Subject: Re: Elan trouble
>
> Jerry
>  Why is it  tail heavy. Maybe you are using the wrong CG point or did you
> put servos in the tail? Is the tail painted. I think figure out why, then
> solve the problem that way instead of adding all that weight.?
>
> Jim Ivey>
> > From: "Jerry Wilson" <JWilsonJr at houston.rr.com>
> > Date: 2005/06/29 Wed AM 07:14:53 EDT
> > To: <discussion at nsrca.org>
> > Subject: Elan trouble
> >
> > I have a dilemma and could use some advice from the group.
> >
> >
> >
> > After over a year of building I have nearly completed my Elan which is
my
> > first attempt to build a fiberglass fuse pattern ship.  It is painted,
> > covered, servos, push rods, and engine (120 four stroke) installed.
> Weighs
> > about 9 lbs.  Looks pretty nice.
> >
> >
> >
> > The trouble is to get it to balance at the CG point on the plan (8" from
> > wing LE) requires 11 oz in the nose.
> >
> >
> >
> > According to Dick Hansen's plan the weight should be 8 - 10 lbs.  So it
is
> > still within the design range, at ~9.75 lbs.  But even if I can figure a
> way
> > to add 11 oz of weight to the nose, I'm afraid the plane will not fly
the
> > pattern well and am having serious doubts completing.  My intentions
were
> to
> > fly one or two more Sportsman contests with it and then move on to
> > Intermediate.  Would appreciate some opinions/advice from the group:
> >
> >
> >
> > Should I try to figure out a way to add 11 oz wt. to the nose securely
and
> > finish the plane?
> >
> >
> >
> > Or abandon the ship and move on to something else?
> >
> >
> >
> > TIA
> >
> > Jerry
> >
> >
> >
>
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