Scale Soaring UK

Hi Max,

I've loved following your rebuild - good effort!

Just to make sure we are confused, I'm pretty sure your wing area is significantly more than 0.57m².

Even if Aviomodelli stuck with the high aspect ratio of the original (25), you would have 0.68m². But it's much more likely they widened the wing chord a little, so you probably have nearer 0.75m². The 4m Alpina has over 0.80, by comparison.

The effect of this will be to reduce your wing loading significantly.

Assuming your 4.5kg mass is correct, I'd expect your wing loading to be about 60g/dm². This is 19.7oz/ft², in old money.

Oooh, I do love a spot of arithmetic.

Good luck with the test fly.

Rog

Hi Rog

Thanks for that. The maiden will be delayed as I've discovered that the aileron in the right wing has developed a twist over time, which has resulted in wash IN . . .


So I have cut it free and I'm going to re-set it using ammonia/water. Shouldn't take long.

But today I'm hoping to meet the Scouts blokes at Blanchetown so I can photograph the prototype of the Motor Falke.

The calculation of the wing area were done by taking the span and then drawing two triangles, and subtracting one. The span is 2.00 metres. The root chord is 195mm and the tip chord is 90mm. Hopefully your arithmetic will give us a better result.

Cheers

Oh dear - wash-in is not a good thing. Hope it comes out ok.

Thanks for the chord numbers Max. Based on the wing platform, that gives an area of 0.7186m². If the mass is 4.5kg that’s a wing loading of 62.6g/dm², or 20.5 oz/ft². Anyway, I’m sure it will fly well.

Thanks, Rog.

62.6g/dm² is better than 78.9g/dm²

OK Sorry about the delay. I've stopped work on the Falke build to concentrate on getting this model ready for Bordertown aero-tow on 27- 29th of this month. We are ready for a hand launch tomorrow. Fingers crossed.

I've filled the nose with lead shot and covered it with PVA to keep it in place, and glued the original lead plug in with silicone.


Then I assembled my VicRC large model CG machine.


Because of the swept back wings, I balanced it with the CG at 25% of the root chord.

I can always add some stick on wheel weights if I need to.


Here are some random shots of it sitting on the balancer . . .


When the retro fitted retract goes up and down there is a slight deflection on the balance pointer.

Hardly noticeable.

Don't know why I have an extra copy of the photo.

Before we could start hand launching, my friend who was helping me, suggested we try lifting the model at the wingtips to confirm where the CG should be.

As the fuselage lifted clear of the table, a dimple about 50 mm across appeared in the middle of the upper sheeting of the wing; about 1/3rd the way out from the root.

It is clear that some internal damage has occurred to the spar at that location. A similar, smaller dimple also appeared in the other wing at about the same spot.

We decided that it would be necessary to insert a strip of 1 mm carbon fibre on its edge, into the wing.

Unfortunately I won't be able to do it before Bordertown, so the A-14 will become a hangar queen for the time being.

I will turn my attention in what free time I have, to starting the Motor Falke build.

Max

Unless you intend to do violent aerobatics it is a bit extream to try lifting a model like your Calif by the wingtips. A much more realistic test of the strength of the wings would be achieved by lifting at around 1/2 span.
I do accept however that if you have a localised deformation in the wing skin, it needs investigation.

AEB

Yes. We did it very carefully, John.

But it doesn't look good.

Cheers