DH 91 Albatross

All repaired and repainted.

I really don't think the wing will stand any more such a repairs so I will spend some time to make sure the CofG is in a 'safe' position and the props are on good and tight.
I will also do a static power run equivalent to a maiden flight (3 minutes) just to make sure nothing overheats or fails.
Bizarrely it will be hand launched with the U/C down (to provide a finger hold) but flown and landed with it retracted!

Very good camouflage of last mishap.

The saga continues!
With the heavier 1800 mAh battery mounted nearly 2" further forward the CofG is now close to 25%. (Don't know what I was thinking as it was at nearly 40% with the small battery so it was hopelessly tail heavy!)
Ran it on the ground at a realistic flight power setting for a full 3 minutes with no problems, except it felt like the tail was going to come off in my hand!
Calm late this afternoon so took it to the field, connected the battery and....... lots of beeping and the fuselage filled with smoke, lots of it!

Fortunately the battery was not yet in its tray so could be instantly disconnected.
Battery and leads still cold so hopefully not much of an overload but clearly at least two ESCs have blown and seriously burnt through the both the wing and fuselage skins. It don't half pong!

Oh! well at least it gives me something to do.

A bit more examination.
The wing cut out to extract the damaged bits.

Not too big an area but it a moot point whether I will ever be able to get all wired up and back in. To say the wiring is a bit 'spaghetti' is an understatement!
The two ESCs

Obviously the lower one got very hot as testament to the un-soldered wires!
It is not clear if the upper ESC has actually failed or is just 'discoloured' due to the burning Depron.
I will test it but it will not be reused.

It is clear what happened but not so easy for the why.
It is not as if these 20A ESCs are worked hard with each only passing some 7A at full power.
The Albatross had done a 3 minute 'endurance' ground test with no issue but as soon as the battery was connected again about 30 minutes later - poof!
So was the ESC at the point of failing at the end of the 3 minute ground run? Or did a short develop between the ESC and the motor?
Also of concern is the length of the now extended battery cable which gives a total of 12" to each ESC. These ESCs are intended for a quad where battery to ESC wire length is normally very short indeed.
However two identical ESCs are used in my A350. They are running on 4s and passing some 15A each! To date it has flown a good many times but the battery to ESC distance is however a bit shorter at 6".

Perhaps to be safe I will add a suitable capacitor(s) where the battery cable divides into 4 which is close to the ESCs.

Eric
I was carefull with the enamelled wires to pass each through its own hole in the printed ribs so they should always be physically separated but you never know.
Klippy
When the new ESCs arrive (from China!) the wing is still plenty strong even enough without the removed skin to be able to repeat the ground test to see just how hot they get.

I have cobbled up the electrics to test whats left. The radio, UBEC, the two right hand motors/ESCs and the aileron servos all function as they should so it looks like the damage has not spread.

The next test is to couple each left hand motor to a spare ESC to check they run normally.
Then its just a wait for the postman!

With the "Cessna Bits" complete and just waiting for the weather (could be a long wait!) it is back to the Albatross.

Having moved the battery forward twice in response to the so far "unsuccessful" flights I am concerned at the battery to ESC lead length and wondered if this is what caused one of them to blow.
My intention is to move the ESCs right forward in the wing so to be closer to the battery which also means they will be further away from the Rx. The downside is it requires quite a bit of 'surgery' to get them out and still more to get them all back in!

Hopefully it should result in a the electrics being a bit less of the "sardine can" arrangement it was before.

Still struggling to arrive at a solution that keeps the battery leads short and avoids the complete mess of wiring with 4 ESCs, a UBEC and the rx all squashed into the wing centre section like it was.

It worked but as I found it really was just a disaster waiting to happen.
So the proposed solution is to mount the ESCs in a cradle on top of the wing so they poke through a hole in the underside of the fuselage.

This arrangement will keep the battery leads down to about 6", greatly reduce the complexity of the wiring within the wing centre section and still mean only the elevator and rudder servos have to be connected to mount the wing.
Well that the plan but I have to wait for some suitable 22 AWG silicone 'power' wire to arrive from Bury St Edmonds of all placed before I can proceed.

No more odd than Bangor though

Makes me think perhaps speed 400 motors in parallel with one ESC were not so bad after all, at least the wiring was simple.

Agreed and as I found out the high frequency pulses of current they require can cause them to 'react' to each other when all connected to a single battery but on the other hand brushed motors are so relatively heavy, particularly in my light Depron structures.

Just to show I have not given up the four ESCs all wired up in the 'cradle'.

The number of wires is mind boggling.
14 out the back going into the wing (4x3 motor wires plus throttle signal and earth).

16 out the front. 8 joined to 2 (signal and earth) and 8 power feed joined to two (+ and -)
Repairs will not be an option!