A little while ago, I build the FT mini Speedster, and wanted to use it for indoor flying, but it was a little too fast for my small area.
What I needed was more lift and more drag, and adding a second wing was the perfect way to do this. It not only slowed the plane down quite a bit, but also improved flight caracteristics.
How to do it:
This upgrade is really simple to do. You need foamboard, the plans for the mini Speedster and some scewers. All you need to do is build a new wing whith the same dimensions as the OG wing, but add 5cm or 2 Inches to the outer wing parts. Note that you cant use the old polyhedral gauge any more, try to make the angle as close to the bottom wing as posdible. Also note that numbers change If you choose the big Speedster.
After that, you poke four holes into the top of your bottom wing and into the bottom of your top wing, right in the corners of the middle wing piece. Then you need four skewers cut to the same lenth. First, glue them into your bottom wing. You want them to go straight up when your plane sits on its wheels. That way, the top wing is slightly ahead of the bottom wing while in flight. Then glue the top wing on, one skewer at a time. After its dry, use foamboard or skewers to make some bracings from the fuselage to the top wing. You want both wings to be parallel.
How it flyies:
It flyes almost like a standart Speedster, but much slower and floatier. Because of more polyhedral, it turns sharper, but is also much more stable. In fact, the stability is incradible. One downside of that is the lack of aerobatic capebilyties. It just wants to self right itself. But you can also use it to your advantage, for example you can fly a half loop, and because it wants to self right itself, you end up with an Immelmann. With a little experience, you can also do something that looks almost like an aileron roll. Or you can do some crazy spins. If you practice a bit, you can also fly high-alpha maneuvers, but that requires lots of throttle management. You can even fly it at walking speeds.
Its also a great trainer. I let my friend fly it, who has never flown before, and after one minute, he didnt even need assistance anymore and flew for five minutes, including some loops.
Another weak spot are the landings. Depending on where your landing gear is, youll end up either with a spin or with a nose over.
Durability wise, its as strong as the og Speedster, which means its gonna survive everything. The weakest Spot is that your top wing could maybe come loose.
Flight with lots of wind:
This thing is perfect for cruising around at calm evenings! Its also good for beginners and to put a 25mw FPV system in.
This should also work for the mini Scout and other airplanes.
Recommend powerpack is powerpack A with 500-800 mah 2s LiPo. The 800 will give you around 15 minutes of flight time!
I hope you liked it!
Have fun building airplanes!