INCIDENCE settings

[Troy A. Newman]

Pat,

to give an answer that you don't want to hear...

We have no idea. The model design will determine it. All the factors 
mentioned from RVP are correct. Also the fuse shape. If the shape is such as 
the model looks like its flying tail down then it needs more positive in the 
wing. Also trim considerations, however I don't try to trim knife edge using 
the wings. I'll leave that to the experts here on the list. I set the 
incidence in the wing to make the fuse sit properly in the air.

A rule of thumb I use is I will set the fuse up with its flying line (datum 
line, zero line what ever) at zero deg to mother earth. I use a digital 
smart level. I then walk across the room or down the hall. If the model 
looks good as in its sitting what my eye perceives as level...I set the 
incidence 0.25 to 0.5 deg to that. I usually start at 1/4 deg and know that 
I will be cranking more positive in it.

I know you said that adjustable is not in the cards. OK that doesn't mean 
you can't adjust it later depending how they did it. If pins in the wings 
and sockets in the fuse. You move the sockets. All it takes is a little move 
and things change.


The criteria I use when flying will depend on what its doing in the air. If 
it still looks tail low while flying level I'll crank in some more positive. 
If it looks level and say it is pulling slightly on upline I might crank in 
positive to see if the upline gets fixed and it doesn't disturb other things 
like power off downlines, or elevator trim. My opinion is a model flies 
better with a little positive in the wing. I tend to fly models that are 
more nose heavy than other people the result is the positive needs to be 
there. And it helps the model track better. I will say this as you move the 
CG aft to amore neutral location as in no elevator inverted and so on...The 
need for positive incidence gets reduced. Also the need for thrust offsets 
gets reduced. But in this config I have yet to get a model to fly in a 
straight line. It might do OK when calm but a tail heavy model (more 
neutral) will be a bear in the wind. I flew my Father in Laws Focus and the 
guys were running the CG up at the front edge of the wing tube. I couldn't 
get the model to settle down until it was almost a full inch ahead of the LE 
of the tube. Then the model tracked like I thought it should. I spoke with 
Don Sczur about his and he had the CG way up forward too.

I believe in providing the model with a Bias so that it tracks on its own. 
This is the way I was taught to do it. Pull the corner and let go. The model 
should do the work for you.

I would say I usually end up with about 0.25 to 0.5 degs of incidence in all 
my models. I could not tell you how much because I don't know where the 
flying line really is on some of them. The ZN Supreme I know where it is as 
a flying line and I know I started with exactly 0.25deg and I cranked more 
positive in it. How much?  Oh about a turn or two until I liked the way it 
tracked.

The other great reason for adjusters is to eliminate aileron trim. If you 
are carrying aileron trim it will be a speed sensitive thing and this will 
not help you at all. You'll have to create a thro to aileron mix to 
eliminate it.

Heck guys do it and beat me with that setup.  But it just doesn't work for 
me, I get the model to fly straight in roll with zero aileron trim with the 
adjusters. Sometimes is a 1/4 turn on a  4-40 bolt and sometimes its more 
like a full turn. If the model is flying tail low or is pitching slight to 
canopy in the upline I might crank just one wing positive. This acts to zero 
out the roll and also increase the positive in the wing as a whole. Then 
sometimes I'll throw in a gob of positive on one side and a smidge on the 
other to raise the tail and also eliminate aileron trim needs. Adjusters are 
a wonderful trim tool.

On big IMAC airplanes we adjust the incidence too. Just sand the socket and 
little ovaled and then put a new ply ring on the inside. Works wonders in 
some case. Other cases the problem doesn't go away and we fix it with thrust 
or the tail or who knows what else.


I have flown a bunch of models in the last few years looking for that 
perfect one. If you email me which one I might be able to help you out.

Troy



----- Original Message ----- 
From: "Pat Hewitt" <phewitt at farmersagent.com>
To: <jonlowe at aol.com>; <discussion at nsrca.org>
Sent: Friday, September 30, 2005 9:53 AM
Subject: INCIDENCE settings


I would like to learn more about incidence settings on our wings. I have a
chance to buy a plane that has preset settings such as O, .25, .50, or .75 
but
how do I make the correct choice. I am sure the best is to have an just able
system but please lets not go there I just want to understand how you pick 
the
correct one.

Thanks

Pat Hewitt
Paola, Ks.






------ Original Message ------
Received: 11:35 AM CDT, 09/30/2005
From: jonlowe at aol.com
To: discussion at nsrca.org
Subject: Backplate Pump for OS 1.60

After seeing the discussion about putting an OS 1.40 pump in the
backplate of an OS 1.60, I got to thinking.  The OS 1.40 pump/backplate
is over $150 from Tower, then you have to get a special 1.60 backplate
for another $100 or so.  In the old days, Perry made special backplates
with integral pumps for .61s.  I had one with a bad pump.  Perry
doesn't make the backplates anymore, but they put in a new pump in my
backplate for less than $50.  As long as we are thinking about making
up special backplates, what about copying the old .61 design for the
1.60, and sending them to Perry to have pumps put in?  This would
certainly clean up the installation of the 1.60, eliminate a couple of
failure points for the separate pump setup, and be a lot cheaper than
using the 1.40 pump.  I have a couple spare old Perry backplates that
could be used as samples for a machinist that I'd be willing to loan
out.  Anyone willing to take this on?

Jon Lowe
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