Help Needed with FT Mini Sportster

[Aero5888]

Hi all! This is my first forum post and I am pretty new to RC planes, so I figured I should see what advice.

I built a Mini Sportster from a speed build kit recently. I am having trouble with it's performance and cannot figure out why - so I am looking for some help. It has an Emax MT2204 - 2300kV motor with a 20A ESC (F pack with a bigger ESC). I set it up with the FT recommended throws for all control surfaces and programed in flaperons. The CG seems to be correct per the recommended setup. I don't have a scale, so no clue on weight. But the only difference between my plane and the FT build video is spray paint and the bigger ESC so I assume it's reasonably close to the specs.

2S - 850mAh with 6x3 prop: I had to keep 100% throttle and trim/use a lot of up elevator to keep it in the air. Very poor climbing ability. It flew more stable when I deployed ~40 to 60% flaperons (I had experimented a little with how much); but still would lose altitude easily.

3S -850mAh with a 6x3 prop: I was able to come off the throttle a little bit but was still a bit of a struggle to maintain elevation. Again, I deployed flaperons to 30% which improved stability and maintaining elevation; 60% flaperons performed better.

3S -850mAh with a 6x4.5 prop: Similar experience as the 6x3 prop in terms of stability and maintaining altitude, but obviously a little faster airspeed. It still required flaperons and high throttle. the downside of this combo was that it drew significant power bc my battery was dead in <5 mins and came out much warmer than I expected.

My best guess based on the above is that either the CG is not right or I built the wing incorrectly - or both!?

I had hoped this plane would fly well on both a 2S and 3S. I need some advice on this bc I don't have enough experience to work this issue out without a fatal crash. Any and all advice is welcome!!!!

 

[Ricci]

2s is to small for the 2204. i think the CG should be moved a little bit to the front

 

[Hai-Lee]

I recommend that you invest in a set of digital scales either kitchen or postage type and weigh the plane. Many a beautiful build has been rendered almost useless because it was too "FAT" to fly well.

As for your prop selection I would use the higher pitch prop when using 2S and the lesser pitch when using 3S.

The use of "Flaperons" seems to indicate that the wings need to generate more lift to fly, (a pointer to the plane being too heavy).

Not being able to climb well could be weight related or that the CG is too far forward.

Post some pics of the control surfaces when trimmed for level flight and further suggestions will come.

have fun!

 

[Aero5888]

Thanks for the tips. I haven't had a chance to get back out with it but I'm going to start with shifting the CG back a bit and work on trim. I will probably stick with a 3s and 6x3 prop for the trials. Scale coming soon but I would be shocked if I managed to build it too heavy unless this design is really sensitive. I assumed that this electronics setup would give plea toy of power. I'm still not convinced I built the wing correct - it may be a little thick and blunt at the leading edge.

I will post again after I have more info to share (or some extra parts to start a new project with!)

 

[MiniacRC]

I had several problems with that same plane. It needs to be REALLY light since it has a tiny wing even for a mini. I had basically the same issue with a 2S and a 6x3 prop. Just make sure your powerpod is not being pulled down because of the down-thrust angle. I stuck a popsicle stick through the nose under the powerpod to make sure it can't move down. If there is too much down thrust it will have trouble climbing like you said.

Another point in general is the build quality. Since this is such a small plane, surfaces needed to be glued in well and perpendicularity must be basically perfect. This is a very touchy plane and to make it fly like Josh flies it in his build video, it needs to be as light and well built as his.

Since you're running the bigger motor, you can probably afford to use larger props and draw more amps from your 20A ESC. Flaperons seem like a really smart choice though. Good Luck! Let us know how you work it out, I love the plane and would like to make one fly eventually.