My first scratch build - A very heavy Mini Sportster

[SkyEye]

Hello all,

I began attempting my first scratch build last Thursday after my beloved Aeroscout met a tragic demise. Salvaging the Aeroscout's 2306-2250kv motor, its 25A ESC I decided to attempt using them in a Mighty Mini. I've been an inspired FliteTest fan for 10 years now and also decided to use this as an opportunity to try my first scratch build.

The build was a constant learning experience that has really gotten me excited about scratch building.

I used some foam that I found at Walmart called Foam-Cor Pro that is 5mm thick and heavy, although I didn't realize that at the start of the build... I'll have the weight ratios of the foams soon.

Despite having to cut a larger wing hole to accommodate the 5mm thick foam, the build actually went rather smoothly and I attributed most fit issues to my imprecise cutting. I didn't start getting worried until I realized that the fuselage+tail planes mated with wings seemed rather heavy. I forgot what the exact number was, but the airframe alone, with no electronics weighed in the neighborhood of 260g... not the sub 250g backyard flier I had set out to build, and not the projected 204g.

The fit issues became extra apparent when for some reason the battery hatch and cockpit formers wouldn't fit properly. I also had to modify the tail plane tabs to fit properly. I decided to ditch the cockpit/turtledeck accessories, for reasons that are beyond me. No landing gear for now. Holding on to the outlandish hope that it might still be 'floaty'.

Here we are, with my first scratch build, the Mini Sportster with 9g servos all around (what I had), a lemon RX receiver, the Aeroscouts guts, and a 1300mAh 3S that it balances out perfectly with. Weighing in at 438g grams, I question if this thing will climb or even accelerate in any direction but the ground.

Maiden flight is tomorrow morning. Palms sweaty n' all that but I'm nonetheless thoroughly excited and honored to join the scratch building community.

I look forward to hearing any thoughts, comments or advice for the future.

P.S. For my backyard flier, I'll just stick to buying a speed build kit of a mighty mini for now.

________________________________________________
Current Hangar: PZ T-28 Trojan, FT P-40, 2x FT Bloody Baron, Night Radian, FT Simple Scout, Aeroscout (†)

 

[Mr NCT]

Find a large field, it's going to fly fast to stay in the air.

 

[Foamforce]

Looks nice! It won’t be floaty, but it will fly just fine as long as you keep the speed up. Launch fast, get high, and experiment with stalling to see how it behaves. Good luck!

 

[SkyEye]

'Maidened' this morning. The flight was short and violent. After the hand launch at full throttle the plane snap rolled to the left, I over corrected with right aileron and the plane did an inverted dive into the ground. ~ 1 second.

I have never had a crash where I didn't know what went wrong, so this one bothers me a little. I couldn't control the flight at all, which also hasn't happened to me in a long time. Other than a lack of me being able to control the flight, I don't know what happened. Maybe my throws were too high?

Admittingly, I had low hopes for the plane so I was not very diligent about my preflight. Although, my CG was good, throws were as suggested, and wind was moderate (5-7kts). I wanted to fly in light wind to hopefully give the plane more lift at low speed.

Though the damage is minimal, other than needing to rebuild a power pod, I think I will write this one off for now and try again with Adam's Readyboard. Hopefully this will give me the sub 250g park flier I am after. In the future I may build a longer wing for the heavy mini sportster and try again.

I'll post the progress of my second try here.

 

[Mr NCT]

'Maidened' this morning. The flight was short and violent. After the hand launch at full throttle the plane snap rolled to the left, I over corrected with right aileron and the plane did an inverted dive into the ground. ~ 1 second.

I have never had a crash where I didn't know what went wrong, so this one bothers me a little. I couldn't control the flight at all, which also hasn't happened to me in a long time. Other than a lack of me being able to control the flight, I don't know what happened. Maybe my throws were too high?

Admittingly, I had low hopes for the plane so I was not very diligent about my preflight. Although, my CG was good, throws were as suggested, and wind was moderate (5-7kts). I wanted to fly in light wind to hopefully give the plane more lift at low speed.

Though the damage is minimal, other than needing to rebuild a power pod, I think I will write this one off for now and try again with Adam's Readyboard. Hopefully this will give me the sub 250g park flier I am after. In the future I may build a longer wing for the heavy mini sportster and try again.

I'll post the progress of my second try here.

Nothing worse than short, violent maiden flights. They give you nothing to work with to correct. Your brain is going "Did I build it wrong? Bad trim? CG? Too heavy? Am I just a poor test pilot?" It all happens too fast to process.

 

[Foamforce]

It was probably stalling. You need a lot more speed to deal with the weight. How much did it end up weighing including the battery?

 

[SkyEye]

Nothing worse than short, violent maiden flights. They give you nothing to work with to correct. Your brain is going "Did I build it wrong? Bad trim? CG? Too heavy? Am I just a poor test pilot?" It all happens too fast to process.

You said it.

It was probably stalling. You need a lot more speed to deal with the weight. How much did it end up weighing including the battery?

Around 450g of weight at launch.

I started wondering, the plane rolled violently left on launch. Is it possible my motor is too torque-y for the plane? Using a 2308-2300kv motor from the Aeroscout with a 6x4.5CCW. I'm still a novice with propulsion.

In other news, the new sportster with Adams Readiboard is built. Just waiting on a battery and prop. Its already 220g though with no battery which I'm not happy about, but its a good start at least.

 

[Foamforce]

You said it.

Around 450g of weight at launch.

I started wondering, the plane rolled violently left on launch. Is it possible my motor is too torque-y for the plane? Using a 2308-2300kv motor from the Aeroscout with a 6x4.5CCW. I'm still a novice with propulsion.

In other news, the new sportster with Adams Readiboard is built. Just waiting on a battery and prop. Its already 220g though with no battery which I'm not happy about, but its a good start at least.

Rolling hard left at launch is the classic symptom of a stall. That’s exactly what I was going through with my first plane a few years ago. I built a severely overweight Storch. When I took off, I would pull up too soon, it would get about five feet off the ground, and then roll uncontrollably to the left. That’s probably what is happening to yours.

You can still fly it, but you need speed, and you need to not pull up too hard at the beginning. Get somebody to throw it harder, at not too high of an angle. Use full throttle and pull up more gradually. Good luck!

 

[SkyEye]

Rolling hard left at launch is the classic symptom of a stall. That’s exactly what I was going through with my first plane a few years ago. I built a severely overweight Storch. When I took off, I would pull up too soon, it would get about five feet off the ground, and then roll uncontrollably to the left. That’s probably what is happening to yours.

You can still fly it, but you need speed, and you need to not pull up too hard at the beginning. Get somebody to throw it harder, at not too high of an angle. Use full throttle and pull up more gradually. Good luck!

Okay, I will keep all of that in mind. I will update you all with the maiden of my new, lighter mini sportster as well (240g without battery, 320g w/ battery). Though I am encouraged that my original heavy sportster CAN fly, I think I will relegate it to being a chuck glider for my dogs.

I'm only now realizing that the FT mini sportster wasn't designed to fit the 250g rule, so I would be pulling teeth to get it there. I love the sportster, but may shift my focuses towards a Sparrow or Mini Scout for my 250g plane.

 

[SkyEye]

Quick update.

Thanks to everyone who helped me with this topic.

My mighty mini sportster flew great at 320g (and raises a lot less unwanted attention...). I look forward to seeing if I can get the Sparrow or Mini Scout under 250g.