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Old Aug 14, 2011, 12:34 AM
DS= -$ & :-)
Ezza's Avatar
Byron Bay, Australia
Joined Feb 2006
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Since buying this plane the conditions haven't permitted much flying with it but today was perfect slermal conditions. I got some good stick time and tuned it 90% now. Very happy with it, so well behaved and looks great in the sky. It does the most axial roll. With a slight dive for speed it requires no down stick at all.

I'm flying at the recommended cg which isn't that nuetral but it does need about 4 clicks of down trim(almost 1mm of down) even in the mild lift conditions today. Anybody else finding this?

Eric
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Old Aug 14, 2011, 09:20 AM
Detail Freak
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Harbor City, CA
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So, Are you suggesting that the incidence is off??
This would be odd to me since they nailed it on the Ceres and Cyril both....

R,
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Old Aug 14, 2011, 10:48 AM
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No he did not suggest that. Maybe it is a little nose heavy.
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Old Aug 14, 2011, 01:50 PM
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United States, CA, San Luis Obispo
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Just an aside, the more I see the Fosa fly (in TK's hands) the more I like it! Looks like a very competitive model.

-Aaron
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Old Aug 14, 2011, 01:56 PM
AKA RustyKnee
Dorset, UK
Joined Dec 2006
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Quote:
Originally Posted by David Cortina View Post
No he did not suggest that. Maybe it is a little nose heavy.
dont you mean tail heavy?

Not a Fosa I know, but my Ceres (aslo Baudis) seems to need a bit of down trim. Wonder if the suggested cg by Jiri is quite rear ward.

Stu
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Old Aug 14, 2011, 02:34 PM
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David Cortina's Avatar
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If the CG is ahead of the center of lift the plane will pitch up as it accelerates with elevator trim unchanged.
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Old Aug 14, 2011, 02:36 PM
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San Diego
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The recommended CG of 98 mm from the leading edge is a good cg location. Some may say it is on the aggressive side. A slightly more forward CG will help the model track straight a little more easily at slower speeds.

I do not find the incidence to be off at all. For cruise speed the trim is neutral. For speed I use a little bit of down trim (~.5 mm) and for thermal I use a bit of up trim (~.5).

The Fosa is a very competitive model. I think it is more than capable of holding its own against the other top F3B models available. It is very stiff and strong. The RDS is very well done. The fit and finish is excellent. The support and service I get from SoaringUSA and Baudis models is second to none. They really helped me out on short notice to get me models in time for the World Championships. I really don't think I could be happier with my choice of model for the World Championships.

Tom
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Old Aug 14, 2011, 02:46 PM
AKA RustyKnee
Dorset, UK
Joined Dec 2006
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Quote:
Originally Posted by David Cortina View Post
If the CG is ahead of the center of lift the plane will pitch up as it accelerates with elevator trim unchanged.
I remain to be convinced but I am aware of taking the thread going off topic.

I have only seen the Fosa at an F3F comp as I don't do F3B, but it certainly looks like an efficient and fast plane. My Ceres is nicely finished. Baudis do seem to have good build quality.

Stu
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Old Aug 14, 2011, 03:29 PM
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Ireland, County Kerry, Kerry
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Quote:
Originally Posted by Stuart B View Post
dont you mean tail heavy?

Not a Fosa I know, but my Ceres (aslo Baudis) seems to need a bit of down trim. Wonder if the suggested cg by Jiri is quite rear ward.

Stu
I'm on your side with interpreting the "down trim" situation.
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Old Aug 14, 2011, 03:53 PM
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United States, CA, San Marcos
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I was not taking a side. I merely stated that it is possible to have a forward CG if the plane tends to pitch up as it is accelerated with a fixed trim position. It is counter intuitive at first glance. Look up static/ dynamic stability. I realize that there are instances that forward trim could be needed in static flight if the CG is too aft.
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Old Aug 14, 2011, 03:57 PM
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Ireland, County Kerry, Kerry
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Please don't tell me to look up anything...
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Old Aug 14, 2011, 04:03 PM
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OK, please don't look up anything
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Old Aug 14, 2011, 05:24 PM
AKA RustyKnee
Dorset, UK
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Cheers Chris

I will check out dynamic stability out of interest.
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Old Aug 14, 2011, 05:24 PM
Detail Freak
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Harbor City, CA
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Dave- Ezza never posted if he had up or down trim in the model.

R,
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Old Aug 14, 2011, 06:30 PM
DS= -$ & :-)
Ezza's Avatar
Byron Bay, Australia
Joined Feb 2006
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Hi Guys,

Sorry for the confusion, this is my fault. After reading your comments above it seems my cg is off by 2mm. When I built the plane I measured the centre of the ballast box(I thought 96mm), but after re checking I see that it is 98mm.

I guess the good news is I get to remove some weight and it should fly even better. Even with cg out it flies amazing.

Eric
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