Fuse mod for the FT Mini Arrow?

This article outlines the challenges I had in helping my long-time flying pal, Scott Lehr get his FT Mini Arrow flight ready. As well as the bizarre fuselage mod that was born from those challenges!

Scott got into his Mavic Pro about a year ago and just recently "came up for air". He asked me to help ready his FT Mini Arrow for its maiden flight ~ which was covered in really cool carbon fiber tape. I got the basic gear installed (FT's Power Pack A) and his Orange RX receiver. I downloaded the plans to get the CG correct as I remembered how critical this point is on any flying wing. Here's what this sleek wing started to look like:

But when I tried to balance it on the CG (Scott wanted just the plain wing with no FPV in the nose) I couldn't seem to manage it ~ battery all the way forward even a 1800 mah pack wasn't doing the trick. I used quarters and tape just to get an idea of what it might take to achieve the proper CG... here's what that looked like:

Yikes! This seemed like a lot of weight, but the FliteTest Team is never wrong about the CG of their aircraft. So I had to come up with a creative way to load 4.9 ounces into the furthest point on the Arrow. I remembered that I had some bird-shot buried somewhere in my building supplies ~ I can remember buying it for my SIG Ninja slope ship I built 20 years ago! Once found, I poured it into 2 cups to carefully mimic the weight of the quarters.

From there I wasn't quite sure how to encapsulate these little lead bb's ~ but in looking around the apartment I found 2 sports drink caps! Small amount of epoxy floated across the tops and BINGO!

Then came the matter of placing these inside the Arrow as far forward as possible. I reviewed the plans and modified the access hatch outlines on the bottom leading edge of the wing. This was about the best place (in my mad scientist mind) to place these newly created weights.

Once this was all buttoned-up, I triple checked the balance as well as the "reflex guage" that is described in the build video.

I really wished I had weighed the FT Mini Arrow after this picture... but I didn't. Anyway, I called Scott and we met up at one of our favorite flying spots for the maiden. Here's a comparison shot between Scott's Arrow and my FT Versa Wing (without the power pod ~ an amazing slope wing):

We chose a big slope site and thought our best bet was to toss into the wind without power. And on that day, the wind was blowing about 12 - 15 mph according to my Dwyer Wind gauge. The first hand launch was not pretty ~ the Arrow nose-dived into the edge of the slope which required a bit of hiking to retrieve it. I was certain I used the reflex gauge provided in the plans to the correct angle?! Dialed in more up trim and the second launch also nose-dived and stripped out one of the 7 gram servos. Did I put too much weight in the nose? We spent the rest of our time discussing these possible missteps while slope soaring the Versa Wing. Scott got some incredible aerial footage with his Mavic as well ~ even in that wind!

So back at my place I couldn't help think there has got to be another way to lighten this plane (improving the wing loading) while still meeting this balance point per the plans. In it's current state , the little FT Mini Arrow just felt so, SO HEAVY with that weight up front. After upgrading the servos to 9 gram and pulling out those bottle cap weights... this image popped into my head:

It reminded me of Battlestar Galactica and the Colonial Viper! So I made this quick template... and these are the results:

There's a paint stick glued into the bottom floor of the wing (just in front of the CG) to the tip of the nose. This adds a real rigidity and allows for a great shelf to Velcro the battery in at JUST the right spot to balance. 

Scott and I did get this version of the wing to fly. The following weekend at the same slope spot, we launched at 3/4 throttle and we added even more reflex than the gauge suggested... which seemed to help the flight characteristics. The nose held up well, even after my not so perfect landings. Here's a flight with my stepson at our middle school field after a few more trim adjustments.

I admit that this is the first powered wing I've flown so I didn't really know what to expect. There's much less glide slope to an aircraft like this, so you've got to keep the throttle ON. In the video we're not using exponential but another flying buddy suggested I try 30%. I'm determined to add that to the settings and see what a difference it makes.

If you're looking for a unique mod to your FT Mini Arrow (without carrying FPV gear around) you might want to try this design!

Click here for the Full Size side profile plan

And here's another flight video on a much calmer day as well as incorporating 30% expo.