Re: F1D longitudinal trim

From: Nick Ray <lasray_at_gmail.com>
Date: Sat, 4 Nov 2006 11:35:12 -0500

Tapio,
Here are my default settings for a new model:
Wing, 0, no wash
Stab, 3/8" negative incidence, with 1/8" wash-in on the left tip,
(when looking from the back)
approximately 30* of stab tilt, and about 5 offset to the left in the tail boom

If the Fuse is floppy, It will come back to haunt you, It took Fred
Tellier point that out with my model for me to see that.

Also, if any of your post are flexing during flight, this would
significantly effect climb. Likewise if your boom, motor stick joint
is flexing.

I topically use three Boron every 60* on the motor stick starting at
the bottom. For the Tail boom, one Boron top and bottom.

If your still not climbing, look at your prop flare, Maybe take a
picture of it and look at its angel/deformation in flight.

Hope that helps.
Nick

On 11/4/06, Tapio Linkosalo <tapio.linkosalo_at_helsinki.fi> wrote:
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> I built my first attempt of F1D this autumn, but have not so far managed
> to get it trimmed. The pmain dimensions are as per Big Square, but I also
> too good look at Kagans model drawings when drawing my model. It came out
> heavy though, 1.8 grams. My first attempt...
>
> The thing is, I do not seem to get level flight out of the model. It
> climbs some on the initial power burst (have flown with 1/3 motors, and
> use back-off) then starts coming down pretty fast. Tried thicker rubber,
> but it did not seem to make difference, also have reduced prop pitch
> (which seems awfully low anyway, and this does not seem to have any effect
> either. So I suspect there is something else going on. The decalage also
> seems quite large (at least compared to F1M, but then D also has smaller
> tailplane, so I guess more forward CG and more decalage is the way to go).
> The model also seems to be very sensitive to decalage setting. At one end
> it stalls, at with just a tiny bit of reduced decalage, it seems to dive.
> And finally, when the stall accurs, it seems deep and model barely
> recovers. I tried one flight with full motor, climbed six meters, then the
> model stalled and made a "waterfall" all the way to the ground level, only
> started flying again at 1 meter.
>
> So the question is, what might cause all this? One thing that came to my
> mind is that the fuselage/tailboom is too flexible. The weight of these
> components is about 30 to 50% more than with "competitive" models, but the
> balsa is not super (but rather Stiffness Coefficient a bit less than
> 100%), and I did not put boron to either tube or boom. The motor tube has
> a rigging to take some load, though.
>
> What kind of decalage should the model have, and what size of rubber is
> used in F1D?
>
> -Tapio-
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Received on Sat Nov 04 2006 - 09:15:54 CET