Depron Cessna O-2

It appears that I did not include a build blog for this - or if I did it has got lost in an earlier generation of this site!
The Cessna O-2 was the military version of the Cessna Skymaster and was used in Vietnam as a forward control observation plane. Mine is a 'special ops' night version all black with low vis markings.
All Depron apart from balsa spar flanges means it is very light (646 g or 22.7 oz) for its size (1320 mm or 52" span) and as a result the 300W available gives 210W/lb or unlimited vertical.
Its last flight (17Apr17) ended in a major crash - its first - the result of a complete power failure - a loose connection?

The first task is to get the broken wing and tail boom secure enough that the plane can handled.
The wing spar has an inserted balsa 'plate' glued onto its front face. All the broken surfaces are simply glued together with UHU POR and held in place with masking tape.
After 24 hours the joints are further reinforced with a polyurethane 'foaming' glue.

With everything now pretty secure work can start on rebuilding that badly crushed nose.

As the Cessna is now 4 years old, quite elderly for a lightweight foamy, I will take the opportunity to restore all the surfaces to an 'as built' condition.

Klippy
I appears I did but under the build topic title of "A tiny plane" which initially had nothing to do with the Cessna!
It does rather show the importance of using a relevant title for any blog!

With the SuperCub more or less complete work can start in earnest on repairing the Cessna O-2.
With the wing and tail boom glued together the true degree of damage to the front can be established.
The impact was quite severe causing the battery to slide forward and puncture the #2 fuselage former and the motor to be pushed back to severely disrupt the 'nose block' and #1 fuselage former. In doing so quite a bit of the fuselage skin was destroyed.
As the skin alone provides all the strength it will be quite a delicate job to replace it.
Still no pictures so any further updates will have to wait.

Lets see if a picture can upload.

Hoorah!
Next shows the nose block rebuilt, #1 & #2 formers repaired with the motor tube in place allowing a start to be made on the re-planking.
One advantage of the Depron skin carrying all the loads is that a simple butt joint with UHU POR is virtually as strong as the original material so no complex scarf joints required which makes life much simpler.

Finish off the planking then filling, sanding (both the nose and the wing repairs) and painting.

This is what it looked like before the crash.

You have to look pretty close to spot anything different but as the wing spar has been repaired I will "tone down" its most severe manoeuvres.

The 'other' plane I crashed at the 2019 Ashbourne Scale Day was the Cessna O-2.
It flew very well, twice and each time for a good 10 minutes but on the second landing I misjudged the speed. Not that surprising as the wind was close to its flying speed!
The result was a severe wing drop 'low and slow' followed by a 'cartwheel'. On a twin boom design that is never going to end well.
Nose badly crushed and motor dislodged, although it did not break the prop.

Each boom was broken off in two places but now glued back on.


Without the tail booms in place the rear motor also took a knock and broke free. Part of the skin had to be removed to get at the bulkhead to re fix it.


I probably should have taken the opportunity to scrap it like the Natter but it simply flies so well.

After cutting away the damaged nose I decided to replace the reinforced Depron motor bulkhead with a 3D printed version that incorporates the 'drum' motor mount as well.

At 7 g it is only 1.5 g heavier that what it replaces.
Not glued in as yet as 2 mm bullets have to be added to the motor wires.

Certainly clever stuff this 3D printing,very useful, no good me getting one i have enough trouble with my new fangled phone

Slowly getting there! The replacement nose block, Depron with 3D printed backing plate.

Baffles in the nose block duct the air from the 'cylinder' intakes directly onto the face of the motor.
Side cheek ducts let the air out again!

And finally despite the crash everything still works!

Complete 03 Nov 18.

Looks ok but I doubt it will worth repairing again.