Magnificent!

Thank you Pat.

I guess the 'golden age' didn't get a whole lot more golden than the Dragonfly!

Another golden moment came when the publication date came and I realised that for the first time one of my models had been given cover position.
Of course the bigger the splash of red, the better magazine editors like it - so the cover hits potential buyers in the eye... but hey! There it was!

Excellent build on a Beauitful Airplane, to a very nice guy! One that I have thought of building for many years!
Joe

Thank you Joe - too kind!

Well, not exactly the same scale as your DH60 - but you know where to find her if the time has come!
http://shop.traplet.com/product.aspx?c=3309

I just noticed an error in my maths (no great surprise there!) in my post #53. I took the power taken by only one motor and divided it by the whole weight of the model to come up with the figure of 32W/lb - which should of course have been doubled for the proper figure of 64W/lb !

My apologies for that!
The reason it took me a while to realise is that my Miles Messenger used to fly at 23W/lb (which being a single-engined model I could not mis-calculate in the same way - and yes, I checked it several times) so it did not immediately strike me as outlandish.

I came across this photo in the Dragonfly file... thought it might be useful for those not clear on the differences between Dragon, Dragon Rapide and Dragonfly.
I think it was probably scanned from RC Model Flyer (a great magazine) so credit is due there. The poor quality is down to my cheapo scanner.

Dan found some nice pics at:
http://www.dehavilland.co.za/DH90_Dragonfly.html
These photos will be of great interest to those wishing to include more detail in their model than I did.

He asked if I knew what the three tubes passing through the port wing root were for - and I didn't know so made an enquiry on Key Aviation forums. The answer is that DeHavillands' designers included these for a number of their aircraft that were equipped for blind flying. The onboard gyros were powered by venturi tubes fed from high pressure air so that they operated at low speed for the take off. This information was included in a Flight magazine article reviewing the aircraft in 1936. Not all Dragonflies had this equipment at delivery and G-AEDU is now back to the standard two venturis having started life with three.

I have to admit that I had not noticed them before... so much for my powers of observation!
As to whether I would have represented them in my model... well probably not as they would have been very close to the siting of the ESCs in the wing undersides... and I do 'sport scale', as my editor is wont to remind me from time to time!

Thanks Dan for raising the point... when do we get to see your progress?

eye4wings:

Thanks for finding that out for me! I guess that is the inspector hat that I wear from time to time having worked in the commercial aviation industry for years. As I enlarged the photos I had noticed what appeared to be the inside part of a venturi tube, but it never occured to me that is what it was. I have never seen a venturi tube configured like that, usually they are mounted on the side of the fuselage. They will pull anywhere from about 3 to 6 in/hg of vacuum to run the gyros. Private planes these days have either an engine driven air pump, or are electric when it comes to running the gyros.

Today is picture day as we bought a new car, I'll sneak some photos of the Dragonfly in too!

Dan

That's where we're all used to seeing venturi tubes Dan! It appears that in the 1930s the gyros they ran were not really operative until at flying speed. Hence the configuration bridging from high to low pressure which no doubt enabled them to generate more suck and operate before reaching flying speed.
The answer that the standard equipment for blind flying models comprised two tubes, that G-AEDU is now returned to, does make me wonder what the third one originally installed ran - but I think I can contain my curiosity!

Glad to hear you're now more mobile again - and looking forward for some photos!

This is my progress so far on the DH 90 Dragonfly, wings will be next. Lots of building fixtures, kind of like full scale construction.

Wow! You HAVE been cracking on Dan!
This is like having deja vu for me!

I suggest adding the top cross member to the cabin before pulling the nose in. It'll save any possibility of distortion of the cabin.

Have you sourced Cyparis for the wing spars or decided to use Basswood?

eye4wings:

I decided to go with basswood with a bit more webbing throughout the center section spar. As we speak I'm in the process of adding those top formers before pulling the nose together, because as you said it will distort things a bit.

Agreed the centre section is where the strength needs to be... any heavy landing will depend on sufficient strength being there - but the outer wing panels are where you can keep it light and win back the weight put into the heart of the model. No beefing it up there!

Just a couple of more pic's after pulling the nose together.

Very Nice, good building!