FliteTest Legacy

[Dad_flyer]

Several flights last week, and 6 more today. Today there was a bit more wind, and it flies vey nicely in calm or not. For the last couple I put the undercarriage back on. Takeoff first time was again difficult. Eager to leave the ground, but seemingly too slow to fly once airborne. Also a rapid roll to the right which was hard to counter with no ailerons. Second takeoff ended nose down/on its back. Gave up and hand launched. Flying was fine, and landing ok (never going to be as easy as belly landing).

Covering is now finished, in homage to the Wot Trainer which gives really clear orientation.

The Eascoat red is rather orange.

Several things to try next:

1: Is it just me? - get someone else to try it on the wheels.

2: More power. I shall need to make more space for cooling ESC and Battery.

3: Connect up ailerons.

4: Make a lower undercarriage, or a belly skid.

[Dad_flyer]

I have been continuing to fly without wheels. Watching Child_flyer with the Storch and talking to others I was less inclined to believe 3 and 4. It seemed most likely that I was holding in too much elevator to keep the tail on the ground, which then got it into the air at too low a speed, and as there is not hooligan quantities of power it cannot climb vertically out of the resulting stall.

Today was beautiful, so I determined to get this sorted. 6 flights in all. The first without wheels to check it over and get used to the sticks for the day. Then put on the wheels and asked an experienced club member to watch the take off to see what was going wrong. I started the run at lower throttle and then let off the elevator to allow the tail to lift, then increased throttle to full and the model just gradually lifted off. Over the rest of the flights it seems best without a deliberate rotation, just leaving the elevator at neutral and allowing it to rise.

So the answer was 1 from above, it was just me. There is also some of 2. Flights are quite short and there is not much power left over for getting out of trouble. The 9x5 prop puts the motor somewhere near its limit I think. I need to measure this again, and measure the weight of the model again. Then I need to remember to write these down.

[Dad_flyer]

More flights this weekend, and no wind. Takeoff now works well.

Another thing I had noticed was that sometimes the model would go left when I wanted right, but then become properly controllable again. With everything else sorted and no wind, it became clear that it was stalling, and then not falling straight. Fortunately not dropping the wing enough to spin. Next flight I trimmed the model for level flight at higher throttle and it flew very solidly. However when the battery was getting down there is not enough power to accelerate out if it gets too slow. Normal flight is 3/4 throttle. This is because the motor is sized for the design weight <2lbs and the strengthened and covered model weighs nearly 3 1/2lbs. That weight is fine for the wing loading, but gives no power margin when running a 250W motor.

I think with the 450Wmax 3536 1100kv on 4s it should be good. It should turn the same 9x6 prop faster than the 1350kv on 3s. I may be able to go up a prop size too. I shall need to move the ESC from the motor pod as there is no space even with a 3s, and it gets quite warm.

[Dad_flyer]

Testing, testing, for the motors and props.

Several interesting things, like the 4-Max budget prop 9x6 and 9x4.7 have exactly the same RPM, current and load. Similar design from HK is less power for the 9x4.7. APCe is much less current than other types and more RPM for the same size prop. The problem is I catch props on the ground, and APCe props break.

On this model I tested the current Airmax 2830/1350 setup. With the 9x6 4-Max that I flew last week, it is 9500RPM at 27A, 300W on a fresh 3s. Beyond the 25A/265W motor specification . A Turnigy cherry wood 9x5 gets it down to 26A, 260W on 3s.

The model is 3 1/2lbs with the current 300g nose weight, so this is marginal in power, as well as being marginal on the motor. As noted above I have had to fly 3/4 throttle which drains the 3s2200 battery quickly.

Therefore I looked at a bigger Airmax 3536/1100 (44A, 450W). This will be more comfortable at the power I need, and give some extra 'escape' power. I also am thinking about using 4s2200 for longer flights, as well as to get the power at lower current as I have 40A ESC.

I started with 3s and a 4-Max 9x6 (not the same prop, but same type, bought at the same time. This motor has a bigger prop driver). Surprisingly, even though the 3s had done a lot of testing and was down to 11.7V, the new lower kv motor delivered almost exactly the same RPM. Less wasted power: 27A, 276W, 9400RPM. On a fresh 4s it got to 40A before full throttle. On a Hobby king 9x4.7 of similar rigid plastic design it is 37A, 525W, 12100RPM on 4s. The max power on Airtek motors do not match with their max current. I know that this model normally flies at <300W, so I should not need to push to that limit often.

I need to fly this next, when I have worked out how to fit the bigger cross mount firmly, and where to put the ESC which is displaced by the 4s.

[Dad_flyer]

Rather windy today, forecast 14mph, but this is supposed to be my winter model so it had to fly. It balanced out with about 180g of M6 nuts up front, total weight now 1750g with 4s battery (3lb13).

Overall it is transformed . Now take off is at a little over half throttle and I can trim for slightly faster level flight so the stall has gone. Coped really well with the wind, and had plenty of reserve power for low passes and going around. In all I was able to choose the throttle setting for more or less power for the manoeuvre I was doing, rather than the binary choice of not enough power to fly or almost full throttle. Much longer flights with the higher capacity (4s2200 instead of 3s2200) added to the lower wasted energy in the motor internal resistance. There is now enough power for a second or third take off when the battery voltage is down a little.

[Dad_flyer]

I made a couple of other final modifications. The larger battery fits rather snugly in the tray, with a foamboard pad keeping it away from the rear motor shaft.

Now the ESC is not in the tray. The motor wires go into the space below, where the nose weight is as well. The ESC is at an angle, coming up through a hole into the upper fuselage behind the battery (I cannot get a good photo of that). All being well this puts it into a decent flow of air. I might need a bigger outlet hole at the rear of the fuselage.

To locate the wings in place I put foamboard on the underside of the wing to lock into the hole in the top of the fuselage. This worked, but also soon got crushed. I have now put on three layers of foamboard, pegged with skewers, and also some more foamboard at the front and back of the fuselage hole. The sides of the hole are flush with the inner edge of the doublers. This gives a good locating slot and plug ~3/4" deep.

No more fiddling allowed for a bit, I need to fly.

(Well, maybe I shall put the ailerons on?)

[Dad_flyer]

Now the wind has finally died down a bit I was able to see more what is my flying and what is the model, and not just trying not to be blown about.

After practicing lots of landings, each one nosing over, it was suggested to me that the wheels were too far back. They were less than 1" in front of the CG. I jury-rigged moving the undercarriage forward, but then did such a hard landing that the mounting broke. However it also felt better in the air with the CG brought a little forward by moving the wheels forward.

Edited By Dad_flyer on 20/01/2020 21:24:47

[Dad_flyer]

So, to move it properly I cut a hole in the bottom.

Then made up a U plate, as with the main mount, but just for two bolts. I shall use a square mounting plate, with the rear bolts in the old front holes.

This is hot-glued to the sides of the fuselage. I Had to make a ply mounting for the torque rods to replace the cracked plastic one.

All up it looks the part, with foamboard spacers.

It flew nicely and landed beautifully. Quite useful that it was for the A test .

The central 1/8" ply sheet gave out landing a bit hard later, so I shall need to make a stronger one.

[Dad_flyer]

New wheel mounting plate, with 1/4" ply. This feels strong enough now. We shall see how it fares at the field.

[Dad_flyer]

Quite a few more flights since lockdown. A lot of take off and landing practice. After the break I find I am very aware of its weight when in the air, and what might happen if it comes down .

[Dad_flyer]

On 30/11/2019 at 14:17, Dad_flyer said:

No more fiddling allowed for a bit, I need to fly.

(Well, maybe I shall put the ailerons on?)

That was quite a while ago, but we have been in lockdown for a lot of the time in between. 

This week I have added ailerons. I set up the servo geometry for some differential as I built this with extra dihedral. The battery was getting a little warm as well, so I modified how the air goes in and around. I also opened up the 'out' hole a bit more.