Blunt Nose Versa Wing CG

[luketheduke]

I'm working on building an FPV blunt nose versa. I have the Power Pack C motor in the back and I plan on running it with a 2200 3s and a mobius in the nose. From my crude calculations, I still need 150-175 grams of nose weight with the motor pushed as far forward as I can get it. I've figured out a couple ways to balance it, but which would you recommend?
Option 1) Get a bigger heavier battery
Option 2) Add lead to the nose till it balances
Option 3) Add a metal rod to the leading edge of the wing.
Which of these would work best, or is there a better method I haven't considered yet? I'm trying to build this for short to medium range FPV, so I want it to actually fly decent, unlike the other FT planes I've built that have been pretty tailheavy.

On a completely different note, any suggestions, tips, or advice for a) flying a wing, specifically the versa, and b) flying a wing fpv? Whats the best way to launch this? What about landing?
Thanks,
luketheduke

 

[gloobnib]

I haven't flown a versa yet (it is on my list of 'possibly maybe' for this flying season). However, my general rule of thumb for CG is:
A) Where possible, fix CG issues by moving the spec'd battery around within the airframe.
B) If more weight is needed than can be accomplished with A), use a bigger battery until you can get the CG correct
C) Add weight/ballast only as a last resort

I've built/flown about 12 different models so far. I've only had to resort to C one time and that was in the Bix3 from HK. That plane was designed to carry FPV gear and without any FPV gear my experience is it will be tail-heavy with any battery that will fit in the cockpit. I 'fixed' it by hot-gluing 3 (dead) AA batteries into the cockpit. Now after 3 spectacular crashes and rebuilds, it actually balances without any additional ballast (thanks hot glue and spars!).

The drawback to approach B (bigger battery) is that the added weight will add stress to the airframe and will require you to fly the plane faster to maintain lift. Also, there is definitely a point of diminishing returns in the battery capacity/weight/flight-time equations. But adding mahs to the airframe is better than adding lead with no mahs to the airframe!

 

[luketheduke]

The plans called for a 2200 3s, but even with that all the way forward and a mobius in the nose, it didn't balance. I swapped out the battery for a 3s 3000mah and with that all the way forward it still needs about 130g of lead fishing weights. Hopefully it flies if it's balanced. I'm planning on swinging a 12in prop with the power pack C, so I think thrust shouldn't be too big of a problem...

 

[Tench745]

I loved my blunt versa and flew it often, so I think I am qualified to answer some of your questions. When building, I used a 2200 3 cell, but could not get it to balance correctly. A larger battery won't fit and still let the top close, so I went with option 2, add lead. I actually had a roll of lead that worked well to add weight and reinforce the leading edge of the blunt-nose section. In my experience the airframe really won't feel it all that much. It's far better to have a heavier and balanced wing than an unbalanced lighter one.
I used white gorilla glue instead of hot glue during construction and removed the paper on the inside of the wings wherever I felt it would be safe to do so in order to save weight and reduce the Versa's tendency to need nose weight. Because of this I think I ended up only adding about 80-100grams to the nose (I may be mis-remembering this though).
I also chose not to pay attention to the CG marks on the plans. I ran the Versa's numbers through a flying wing CG calculator to get close and then performed controlled glide tests in my side yard (radio on) until I got the best distance. I found that the CG on the plans was about 1/4 to 1/2 an inch too far forward, at least for my plane.

As to your other questions, I launch left handed so I can keep my right hand on the controls. I hold the plane by the right wingtip letting the left wing hang towards the ground behind me a bit. Then I bump the throttle up to takeoff power and give it a decent back-handed toss into the air. The goal is to let the motion of your swing lift the outer wingtip and release the plane with wings level when it is beside you. This keeps the prop far away from any fleshy-bits you might want to avoid severing.

Landing is pretty simple too. The Versa is a decent glider, so I come in within a few feet (maybe six feet) of the ground and cut power, gliding it down and flaring gently about 6-12 inches from the ground. This gives the prop a chance to stop windmilling and it will usually align with the trailing edge of the wing without hitting the ground or risking a broken prop, at least not in the year or so I flew my Blunt Versa. If you come in with power on and bump the ground you will almost definitely break the prop.

 

[Tench745]

When my Blunt Versa finally died I built a new version, sort of a cross between the Versa and the Spear. It uses the Versa wings without dihedral and a center section that protrudes forward much like the Spear to aid in balancing, plus a wooden spar to strengthen the wing-to center section joint. I haven't tried it as an FPV ship, but it flies on rails even inverted. I'm quite happy with it. I have some plans if you're ever interested.
There's lots of room to play around with the Versa and make it your own. Feel free to experiment once you get yours flying.