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Dec 11, 2018, 12:49 AM
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New version of 3D printed leg fairings


I made up some new main gear leg fairings, because the prior printed ones were not printed well on the I3 Prussa clone, but also to improve them a bit.
The retract mount plate and pivot system are the same, but now the 'pins' for the pivot are totally within the pieces, whereas before they were slightly too large to fit and the plastic 'bulged' out after drilling it to suit. The new ones are only printed 'holes' that take the new pin cleanly.
I also fixed up the way they attach to the gear leg. A short piece of 2mm elastic cord, with 'thin paperclip ends' crimped onto those so that they are 'plugged into' the leg fairing standoff piece.
The leg fairing standoff piece is the part that hits the oleo when the gear is retracted and sets the fairing to be flush to the wing underside. It will also have some very small side rails in the wing as the stop for the fairing. The elastic cord attachment is so that the leg pulls the fairing in, and also has 'give' when it goes in further than the fairing needs to, or if the leg is bent from the retract pin being bent.

There are also 'riders' (ramps?) printed and attached to the oleo up near the suspension 'scissors'. These form a slope so that the fairing standoff rides up onto that and moves even further outwards of the oleo/wheel. If they were not there the fairing only clears the wheel by about 1.5mm. But the full scale P-51 has its fairing move out a LONG way from the oleo/wheel, so that is what this 'rider/ramp' creates.

I forgot to take some of the pics, so will add them soon....


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Dec 11, 2018, 12:53 AM
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Ordinance Rails/Mounts


Long ago I had cut off the stock Drop Tanks to make them removable, but I never made the mounts.
So now I have made up the keyed mounting rails, that go into the Wing foam rails, and will allow fitting various stores items - such as the Drop Tanks, or 500lb Bombs etc.
It is a copy of the Freewing key system, seeing I was making, 3D Printing, other Freewing stuff so then I realised I should do the P-51 right after that!

A "Spiked key rail' is made up to stick/spike into the Drop Tanks - CA'ed in. One of the rare cases of a truly workable use for CA glue!
The Wing Rails have their Key Socket glued in with foam contact glue. Which suits that task.

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Jan 06, 2019, 05:47 PM
Registered User

End of the P-51D Mustang


Ouch!!
The P-51 went down in a big way on the weekend! A lot of damage to the fuselage and that is pretty much not repairable. Not in any way that would come out looking any good, plus the huge amount of TIME it would take. And all for a plane that was a bit 'plain' and mediocore Power/speed anyway.
So it is not worth doing.

I was merrily flying around and decided to do some low passes with the gear out, but it did not extend one leg. This has happened before, and I think it is some pre-load pressure on the oleo/wheel when it is stored. So I flew around trying... re=trying... re-trying.... but it would not come out.
Someone suggested "Do a tight loop to have high G Forces to help it come out", but I knew it was more to do with that pre-load pressure problem. Though it COULD help and work, so I did that.......

As it came over the loop, and towards the 90deg vertical point, I flicked the retract switch and it immediately cork-screwed out of control.... all the way nose first into the ground! Hmmm....
It SEEMS like using the retract caused whatever went amiss.
In hindsight I am not even sure why I didn't wait until almost level to switch the retracts, as that would ahve been higher G Forces then too. Though it probably still would have done some form of crash - maybe. maybe not of the retract actually moved.....

The batteries ejected - one severely damaged - and after re-connecting power after the crash, everything was working. Even the dumb retract that would not come out in flight! This suggests it did not have some fatal failure - like the SBEC etc. But rather it was a temporary 'failure', such as the retract causing low voltage and a brownout. Though it has a 20 Amp(!!) SBEC in it!

There is also a slim chance that it stalled, via an Accelerated Stall. But really, it was a 'clean path' loop and I doubt the AoA rose to be too high at all.
To me it seemed there was ZERO response to controls, but it also happened so fast that you might not even perceive small response(s).

It would need a new fuselage to ever look any good anymore. Let along still a lot of TIME to do ti all.
And then, I had also dis-liked the lack of 'War power' that the weak 4S system had. It really needed to be a much greater Power 6S setup - which would also cost a fair amount of money to do!
So all in all.... I decided it has had its day and I will throw it out.....

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