Douglas F4D Skyray

Took 2 days but the nose is built and glued on to the fuselage.

The next bit is to build up the solid canopy and then cut it out to make the battery hatch. It will also give access to install the ESC and the rx.

It always surprises me that I never learn.
I found in my 'spares' drawer I had a "Favourite" 20A OPTO ESC. They are minute and need no cooling. It had a suitable UBEC coupled to it.
I checked the UBEC worked and for lightness I soldered the solid motor wires directly to the ESC, making sure the motor ran the right way, but it did mean it was rather 'built in'.

I did wonder why the ESC and UBEC was in the spares draw particularly as the Deans and servo plugs had been simply cut off.
Anyway it all worked using my 'test' 2s battery but when I coupled up the intended 4s LiPo the motor ran up to about 3/4 throttle but beyond that it just started to make an odd noise and went no faster. Was this the same problem I ad had with the He162 with the prop stalling in a long duct? I then remembered the reason it was in the spares draw. It was faulty!

I then found a new and unopened 6s 20A version (the replacement?) and "once bitten twice shy" this time I set it all up using screw connectors so it could all be easily be removed if it did not work properly.

It seems to be ok on a 4s.

It is only drawing 5.7A at full power so if it flies ok it should manage a good 10 minutes even on a 1000mAh 4s.
Now to build the ESC/UBEC all in again.

If things I have are 'dubious' - they go into the spares container labelled BIN!

Yes. I really must throw stuff away and avoid filling the box labelled "String to short to keep" :woohoo:

With the revised electrics back in and tested not much progress just the cockpit canopy built in 3mm Depron.

Its a one piece affair to give the largest opening as a hatch.

Wings next.

The wing is simple in concept, top and bottom 5mm XPS skins with four XPS shear webs to create the section but it does need considerable force to bring the leading and trailing edges together.

And it has to be maintained for at least 24 hours for the glue to set hard enough! The aileron is then cut out.

The aileron servo lies flush with the underside.

With such a thick skin the wing panel is surprisingly stiff. Not that rigidity is much of a problem as the 'fuselage' makes up nearly 1/3 of the 660 mm wing span. :woohoo:

The wings glued in place.

Complete except for a bit of skin, rx, battery and paint it weighs 220g. The 1000mAh 4s weighs 107g so I estimate 350g complete.

Whilst the major dimensions are true scale it is only 'stand off' as far as some detail profiles are concerned partly as a result of working in 5mm brittle XPS and the needs of the duct diameter.
I set the size to limit the amount of XPS used in what is a very low aspect ratio design but with hindsight I could have made it a much as 30% bigger (920 mm span) with an acceptable weight increase and still retaining the same motor and duct. This would have enabled it to be built much closer to 'detail' scale shape particularly around the inlets.
However first to complete 'as is' to see how it flies.
Perhaps bigger next time.

I do love your work Simon, I wish my Shingles would let go so I can get on with something!

Klippy
Thanks.
It does appear the shingles as a recurring condition can be erratic. I hope yours goes back in permanent remission soon.

My own auto immune vasculitis appeared out of the blue but has been in full remission for nearly 20 years, but you never know.

My Shingles also appears to be stress related, Mary has been ill with Sciatica for the last 3 weeks (climbing the walls with pain) and my Shingles which was never dormant is now in full swing.
A note to anyone reading this, if you should get a rash around your waist, see a Doctor immediately for medication. If it starts blistering it's too late!

Been there (years ago) got the rash, sore as hell for a week - lived in a dressing gown, as I couldn't bear ANYTHING touching me around the waist. I've been clear of it since, luckily.

The initial paint goes on.

The US Navy used a pretty pale grey top side unlike the RN "Atlantic grey" but then the US operated in the sunny Pacific most of the time.
The elevons, fin and fuselage strake will be blue . not exactly scale but will improve the visibility.

A bit of nerdy information.
This Russian scale line drawing clearly shows the elevons as barn door type.

However as far as I can tell all production Skrays had mass balance sections on the outer elevon portion.

I am omitting them simply because as a belly lander that needs lots of positive up elevator for touch down they catch on the grass and get ripped off. :woohoo:

It is now virtually complete and decorated.

Just the elevons links and the canopy magnet to add.
The paint and the battery box has added a bit more than I hoped. It now weighs just over 400g with the 1000 mAh 4s on board.

It does fly but.....
There is always a but.
1. It is a bit under powered.
2. The elevons have got to be reset with some permanent reflex, even full up trim was insufficient. It would probably be advantageous to extend the elevons to full span and reduce the throws slightly.
3, The big issue is the motor keeps cutting out! :woohoo: 3 times in what was a short flight.
Each time power returned in no more than a second. Indeed the recovery was so quick I could not determine if control was lost at the same time.
So was it:-
The ESC overheating
A bad connection
A loss of signal.
As you might expect in a 30 second full power ground it ran perfectly!
I have reset the elevons and changed the rx.
As soon as the kids football match finishes I will try again.

Well that did no go too well!

It actually flew or rather staggered round for nearly 3 minutes, still cutting out regularly but I got it wrong trying to come into land and entered a typical delta high alpha stall, a severe wing drop and a very steep descent in from about 8 ft. Not so much a "lawn dart" as a "nose crumple" which of course the XPS does quite well.

The regularity of the motor cut outs (every 15 seconds) coupled with a different rx suggests the ESC and/or the UBEC are the likely cause rather than a loss of signal. Surprising as the motor only draws 5A through the 20A ESC and the 3A UBEC is only driving the rx and two micro servos.
So a new ESC it is.
I have ordered a 3x4.5 three blade to replace the existing 3x3.5 four blade. My experience with the He162 suggest it should both absorb more power and handle the long inlet duct better. The only problem is I can see no practical way to remove the motor let alone change the prop! :woohoo: