Looking at it the other way, having the thrustline and wing incidence parallel gives you upthrust in flight. I've always found this to be the best set up.
Some of us tried the droop boom set up on F1D a few years ago but the only one who could get them to fly decently was Ron Green who,sadly, is no longer with us.
Bob
----- Original Message -----
From: Bill Gowen
To: Indoor_Construction_at_yahoogroups.com
Sent: Tuesday, December 02, 2008 1:56 PM
Subject: Re: [Indoor_Construction] Re: Fwd: low ceiling high duration
I agree. But most of my models use the droop boom system which actually provides built-in downthrust if you're considering the thrust angle relative to the wing incidence.
----- Original Message -----
From: RLBailey_at_care4free.net
To: Indoor_Construction_at_yahoogroups.com
Sent: Tuesday, December 02, 2008 7:21 AM
Subject: Re: [Indoor_Construction] Re: Fwd: low ceiling high duration
My own view - no downthrust on any class of model unless necessary to trim the climb. I would only use it as a last resort.
Bob
----- Original Message -----
From: Mark
To: Indoor_Construction_at_yahoogroups.com
Sent: Monday, December 01, 2008 10:31 PM
Subject: [Indoor_Construction] Re: Fwd: low ceiling high duration
--- In Indoor_Construction_at_yahoogroups.com, "and4metoo" <stankos_at_...>
wrote:
>
>Does anyone have an opinion as to what few degrees downward thrust
> might do for you in climb phase? Will it hurt you when your cruise
> phase is over?
> At Sci Oly last year some students had their planes flying ever so
>flat and climbing ever so slow. Prop seemed to be slow so I think
> prop pitch was on the high side.>>
>
> Pete
Most of us accept downthrust as a necessary evil, but try to minimize
how much is needed. But at some point, better stability results in
more time. Sometimes downthrust is accomplished with only stick bow
from rubber tension which is highest at launch (That's where down is
the most needed.)
For low ceiling work, if you are backing off turns, you may be
launching at relatively low torques, so you could experiment with less
or no downthrust there. (But I have always gone back to using
downthrust, after such experiments.) A few indoorists say they do just
fine without any downthrust.
> flat and climbing ever so slow. Prop seemed to be slow so I think
> prop pitch was on the high side.>>
Prop pitch is another subject, not usually related to downthrust, but
sometimes higher RPM from lower pitch can accomplish stability too.
Mark F1diddler
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Received on Tue Dec 02 2008 - 08:34:47 CET