INCIDENCE settings
vicenterc at comcast.net
vicenterc at comcast.net
Fri Sep 30 17:26:17 AKDT 2005
Troy,
I agree with your analysis 100%. Pat and I fly the Abbra. These models were originally set at 0.75 degree positive incidence with no adjusters. I decided to install adjusters this winter in order to have the full flexibility as you explained. I have had the same experience in regard the incidence and I usually finish with 0.25 degrees. Pat's Abbra could be OK since is gas engine and it is heavier.
Now you can order the Abbra at 0, 0.25, 0.5 and 0.75 degrees. I think it is better to go 0 or 0.25 if you use glow engine.
Thanks,
Vicente Bortone
-------------- Original message --------------
> 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"
> To: ;
> 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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