Woodie, mjfredrick, flyncajun and anybody else with Genesis experience:

Can you post your CG location relative to the LE at the root of the wings (to save my mathematically challenged brain from having to sort out the numbers in a formula)? My Genesis wings were from a different source and the wing tube might not be in the same location as what comes from CA. The numbers Woodie has and mjfredrick says are similar to his, are quite a bit forward from the tube than what mine used to be. I say used to be because I have not checked it since doing some repairs (to the fuselage in front of the wing) * spent way too much time trying to get engines to run reliably.

Measurements in relation to the LE at the root would be useful for me. Thanks!
Tom

I want to start pattern and recently finished my model. I am about to start trimming the plane. If the NSRCA trim guide is wrong.

- What do we do?

- What do we use to guide us in the trimming process?

The model I built has 0° thurst down, 2° right thurst, 0° stab, and -1° wing incidences per designer.

Pedro

http://www.hebertcompetitiondesigns....ngulation.html


Mark

Jeese Loiuse
The original designer probably liked his setup so at least start -from HIS referrences . And now for a BIG hint :
there is no magic incidence setup
None
Zip
Nada
Typically a model needs a wee bit of angle between the wing and the stab - but VERY little- just enough to counteract any other forces for good hands off level flight at cruise speed .
One degree is : 1/4" in one foot
This means that if you actually could measure to within .001, you would see that a foot wide chord -at the root- would have the true LE 1/4" higher than the true TE.
That is a lot on an aerobatic model which is very lightly loaded (wing loading) OR very fast .
Those bubble level thingies can easily lead you astray-especially if entire wing LE/TE are not perfect.
The true ZERO LIFT chord line is one where the airfoil -irrespective of the shape - generates ZERO lift
CG is where you will likely spend the most time sorting out what compromises YOU like for your flying.
there is no magic CG either .
If more "designers" took time to build a pot full of flat foamie dsigns and sort out and understand what is happening - they could save a lot of time and money of big models - the same forces are at work on both but the foamie "fixes" and "trims" are quicker and easier to do.

CG relative to LE at root on my Genesis is 5 7/8" back.

I have made one other modification to the Genesis that helped mine a lot and it has nothing to do with CG at all. I always found the responsiveness of the Genesis rudder to be VERY soft at center and then get very touchy beyond about 1/2" throw either side of neutral. Using expo did not help since it made the center dead when I got it to the point where it wasn't touchy. On my Genesis, the rudder leading edge was much thinner than the fin TE, about 1/8" on both sides. The rudder is also pretty large in comparison to the fin. I assume this was a design technique to make the rudder less touchy. Anyway, I first removed about an inch from the TE of the rudder and that helped with the touchiness outside of neutral. But it was still very non-linear in feel. Next, I built a new rudder that had a LE that matched the fin TE and kept the reduced total rudder area. For me, it fixed the dead feeling at neutral and got rid of a lot of the touchiness outside neutral. Rudder has a much more linear feel for me.

Woodie

I have no way of knowing where my CG was set, the plane went in a few months back. I did have the receiver battery all the way up against the firewall, and the receiver was just behind the landing gear plate. The main reason for the softness of the Genesis rudder around center is the shape of the vertical stab. Rather than having a normal airfoil shape, it is shaped like a teardrop, which makes slight rudder inputs relatively ineffective because the rudder is being partially blanked out by the leading edge. Like I said before, a few design issues with the plane, but it's very capable as long as you don't mind using a mix or two. I tend to bad-mouth the Genesis, probably more than I should considering I flew it very well (took 3rd at the Cajun Nats in Intermediate last year versus a field of 13, many of whom had already pointed out of the class). Hope you can get yours flying as good as mine did.

Woodie -

Thanks for the measurement. I'll see where I am in relation to that. The rudder mod sounds like it might be a good winter project. In MN that could well be October...

It will be nice to get some of the quirks ironed out. If I can just get an engine to run consistently again and get some time in the air again...!

Thanks to all!
Tom

I also did a similar rudder mod to my genesis. Except i achieved it in a different fashion. I simply narrowed the vertical fin Tail post by 3/32" on each side. This used a myriad of clamps and angled aluminum to hold the glass to the tailpost while the glue dried. MY rudder is pretty sensitive at neutral, so much so i had to add some expo which i normally never use.

what is the consensus on a pattern biplane with regards to top wing relating to bottom wing incidence?

I run my stab and top wing at zero and bottom wing at +1 to start. I then adjust the incidence on the bottom wing until I get straight uplines.