New guy here:)

[JasonK]

your pitching up to much for the plane/power plant which is causing to slow down to much.

Is this the scaled down version?
what size and KV motor?
what prop?

 

[MachineCat]

your pitching up to much for the plane/power plant which is causing to slow down to much.

Is this the scaled down version?
what size and KV motor?
what prop?

Yes, we did realize our pitching issue. And it was getting better and better. Last time we did it too high and the plane could hardly move. But I would still expect it to pick up the speed faster when it was not pitching up that much.

And yes, it is a scaled down version. The wing span is 16inches. I had the brushed 8520 motor with the 5.5 inch propeller (with some gear box to gear it down) before I decided to build the plane. I was told that motor/propeller combination has a thrust of 67g, while my plane is 73g right now.

 

[JasonK]

Yes, we did realize our pitching issue. And it was getting better and better. Last time we did it too high and the plane could hardly move. But I would still expect it to pick up the speed faster when it was not pitching up that much.

And yes, it is a scaled down version. The wing span is 16inches. I had the brushed 8520 motor with the 5.5 inch propeller (with some gear box to gear it down) before I decided to build the plane. I was told that motor/propeller combination has a thrust of 67g, while my plane is 73g right now.

There is more to it then the static thrust, there is also pitch speed (thrust goes down as the craft goes faster until it hits the pitch speed), also air frame drag.

if your static thrust is less then your plane weight like that, you likely won't be able to climb more then 20deg or so... none of the near vertical climbs like you see on some other craft that are sitting with more thrust then total weight.

 

[MachineCat]

There is more to it then the static thrust, there is also pitch speed (thrust goes down as the craft goes faster until it hits the pitch speed), also air frame drag.

if your static thrust is less then your plane weight like that, you likely won't be able to climb more then 20deg or so... none of the near vertical climbs like you see on some other craft that are sitting with more thrust then total weight.

Thanks!

That is my understanding as well. So currently my son and I are taking two routes in parallel: improving our flying skill, and getting a more powerful motor.

Maybe I should get more batteries for backup. One of issues is that we go out and had to come back very soon because the battery runs out. But I do not want to buy more of those 1S battery while I am pretty sure I will switch to a large motor that won't run on 1S.

On the other hand, today we had a big improvement because we really ran the battery out. Before today, we always came home early because the plane crashed too hard and something broke.

 

[MachineCat]

Some update after experiments:
Inspired by @JasonK 's words, I decided to take the watt meter and measure how much power the 8520 is drawing. And before I got any real data, the motor gave up and stopped running. I realized that one of wires (buried inside the fuselage, not touched by anyone) got broken. So I had to take the plane apart and soldered that wire (there was about half mm wire left sticking out of the motor). Then I measured the power, it was about 16w at full throttle. It was a little bit surprising to me. I was expecting a value lot smaller.

Then my other motor got here so I decided to try that one first since the plane was already apart. It is a 1811-2900kv , around 30W max. Plenty of power for my little FT flyer. And it turned out really good. It picks up speed fast and flying/turning was very responsive.

And I have to say it was too responsive. So my son and I soon crashed it again . To my surprise, the place that broke was the firewall. Original FT flyer says the firewall should be 1.5mm plywood. I felt it really fragile, so actually I added another layer of plastic gift card. And it still broke before everything else. How could the original design with the 1.5mm plywood work at all? Maybe I got the wrong type of plywood? I need to find some other way to build the firewall now.

Another thing I noticed with the new motor, is that it rotates so smoothly. Comparing to the 8520, it was just like cutting butter with hot knife. And when I was measuring the power of the 8520, it vibrates so much that I almost could not hold it with my finger. Originally I did not realize that was an issue. Now it seems something maybe wrong with that motor/prop set. Will do more experiments on this later.

 

[MachineCat]

More update on the firewall. I realized that I got the basswood instead of plywood. First time buying this kind of stuff.

So the basswood can handle some load on one direction but not the other. Even with a plastic reinforcement, it bends and breaks easily when bent along the wood grain.

Now I put two layers of basswood together, with their grain perpendicular to each other. And again, reinforced with the plastic gift card, sandwiched between two layers of wood. So far it seems pretty strong. Hope it can survive some crashes.

 

[MachineCat]

Took another fly. Guess there were some damages in the fuselage already, is became so wabbly and crashed very soon. Now the fuselage is broken and we have to start over.

Probably will go with some pusher this time, before another try on FT flyer later.