Need CG location for giant Versa Wing

[Winglet]

About to finish my new Blunt Nose Versa Wing. Added 10 addition inches to the span of the center section and a few more inches in the elevons. I'm hoping for even more glide and and even better soaring capabilities, but who knows? With the increased span also come more drag, so will see what happens. Hey, that is why we call it Flite Test. I'm calling it the Versa Soar.

My question....any idea where the CG should be? I know where it goes on the standard Blunt Nose. Will it still be in the same location or even further back? Need someone smarter than me to give me a rough idea before I start test flights later this week.

Thanks in advance for your help on this one.

Here is a photo.

Mike

 

[stay-fun]

Is it just scaled up, or did you change the blunt nose vs wing size ratio? In the first case, just scale the CG of the plans accordingly. In the other case I don't know . I guess if you would make the blunt nose larger compared to the wings, the CG should become more forward.

But what do I know I've never built or flown a wing :black_eyed:

 

[Winglet]

The center section is the only thing scaled up.

 

[TEAJR66]

Try this calculator. I have not used this particular one (cant find the one I did use). You will need to change the number of panels to allow for the blunt nose conversion. If that one does not work, try a google search of "flying wing calculators" and you will find a plethora of online resources.

http://wingcgcalc.bruder.com.br/en_US/?

Be safe and have fun,
Tommy

 

[joshuabardwell]

I tried my best to build the wing in the CG calculator. I got a CG of 153 mm at 20% or 140 mm at 15%. Here's a URL that will link you to the calculator with the pre-filled values if you want to tweak them.

http://j.mp/1qMQQWY

I used 10 inches as the total width of the middle "blunt" section, but looking at your photo, I think that may not be right.

The only measurement that I couldn't make sense of was the sweep angle. I measured 50 degrees using a protractor on the printed plans, but that didn't look right at all on the calculator. So then I measured the sweep distance and entered that, and it looked mostly right. The resulting angle was about 30 degrees.

 

[TEAJR66]

Since he only made the plane wider, not longer, wouldn't the optimal CG be the same?

There are a couple of ways to find out.

1. Try and fly.
2. Use the calculator with the original dimensions then try again with the new dimensions then compare.
3. Use the calculator with the new dimensions because the old dimensions are irrelevant (unless you just want to know).

Me being the curious sort, I would have to run both sets of dimensions now that the issue has been brought up.

I am also curious to see if he feels that the plane is pitchy. I think that for the real estate I would keep the pointy nose and just scale up the whole plane. Get more room, keep the extra lift and the added stability.

Be safe and have fun,
Tommy

 

[joshuabardwell]

There are a couple of ways to find out.

Dang! Somebody caught the comment before I deleted it. I actually crunched the numbers on the calculator, and, yes, the CG changes. I think the reason is that widening the center section changes the center of pressure (CP). The center section produces lift, and is in the front of the plane. Widening the center section should, therefore, move the CP forward, requiring a forward movement of the CG to compensate.

We can understand this by thinking about two extreme cases of a wing. In one, the wing is an infinitely thin and wide rectangle (zero sweep). In the other, the wing is an infinitely long and thin V shape with no "blunt" center section. It can be seen that the CP for these two scenarios is different, with the CP in the center of the rectangle, and further back for the V.

 

[scottdnc]

I like the W I D E body Versa. Here's a CG calculator that might help.

http://rcwingcog.a0001.net/V3_testing/index.html

 

[Winglet]

Wow! Thanks for all the help. I wasn't aware that calculators even existed for this. I will give them a try but if all else fails or it just doesn't look right, I'll balance it at the original Blunt Nose CG and give it a toss.:black_eyed:

 

[TEAJR66]

I like your attitude!

Let us know how it works.

Be safe and have fun,
Tommy

 

[Jimmyp]

I have use the calculator http://rcwingcog.a0001.net/V3_testing/index.html as well and it worked well for me.

 

[SKT]

I will give them a try but if all else fails or it just doesn't look right, I'll balance it at the original Blunt Nose CG and give it a toss.:black_eyed:

How'd you go Winglet?

I'm contemplating doing something very very similar and would be very keen to know how you went? Did you fit a motor and fly it powered or just as a soarer?

 

[Winglet]

It is going well. I'm flying it powered. Using the same motor and setup as my standard blunt nose. Glides and glides and glides but I'm not sure it is really any better than the Standard Blunt Nose version. It is very easy to see at high altitude however.

 

[SKT]

OK so no data on flight times or throttle % needed compared to the stock blunt?

Any adverse tendancies?