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Author Topic: Avro Avis aka The Flying Carrot  (Read 468 times)
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RalphS
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« on: April 17, 2017, 11:35:39 AM »

I had hoped to fly this at the Indoor Scale Nats this year.  A dark, miserable winter and no Velodrome flying took the edge off my urge to complete the model and I have failed to finish it.  I bought a Silhouette Portrait craft cutter and did a redesign to take advantage of the fine accurate cutting potential.  This took time and put me yet further behind.  I decided to go with full depth spars with immaculately aligned notches in LE and TE and everything just clicked in position.  The perennial problem of neat thrust adjustment and the various solutions that appear from time to time caused a bit of thinking time but I feel that I have, at last, got a nice system that doesn't need shims behind the noseblock.  The prototype Avis (and there was only one) has challenging writing and there is not much clear evidence of the actual final form of this feature. The existing model designs and published drawings do not match the available photographs and I had to do a drawing and get it approved by the members of the Scale Tech Committee who were very accommodating - thanks Andy and Bill.

It was going together quite nicely until I found that the full depth spars would not stop the wings bowing upwards after covering.  In the end I stripped off the top covering and added an extra 1/16" square spar.  In my hurry and not wanting to do too much brutal sanding I now see that, in good lighting, there are some lumps and bumps that need removing. This means either making some new wings or stripping off the covering and re-sanding. So, unless I can get some of those pills that keep people awake and alert for a couple of days the Flying Carrot will have to wait a bit longer before taking to the air.  Anyway a few photographs to fill up the internet will take up yet more building time.

Photos show original wing structure, fuselage and some trial fits.  I don't know why I make small complicated models.  i could have made a couple of modern coupes in the time I have spent so far on this.
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Avro Avis aka The Flying Carrot
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RalphS
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« Reply #1 on: April 17, 2017, 11:55:20 AM »

The noseblock and thrust adjustment looks ok to me.  When I made a Storch in 2004 I designed a prop bearing with a radiused section that seated in a cup to allow it to adjust for side and down thrust but couldn't find an easy way to hold it in position.  My electric r/c models are mainly made from foam and I have come to love UHU Por adhesive.  It sticks well enough but never seems to go hard and stays flexible.  I tried sticking a brass tube to a piece of balsa and allows the tube to move in all directions but holds together.  The first photo shows the parts used on the Flying Carrot consisting of an ali tube with a ply thrust plate with a slightly oversize hole to allow the brass tube and soldered on washer to take up thrust angles as required. The UHU Por goes inside the tube from the rear and sits around the brass tube/plywood thrust plate juncture to stop it falling out.  The idea is to fit shims between the propshaft tube and the rear of the exit behind the noseblock to give thrust adjustment.   I vacformed the cowling from 10thou acetate.  
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« Last Edit: April 17, 2017, 12:08:37 PM by RalphS » Logged
RalphS
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« Reply #2 on: April 17, 2017, 12:07:02 PM »

Forming card cones for wheel discs always end up with an overlap when I do them so I turned up an ali cone, mounted it on a bit of dowel, heated on my trusty covering iron and plunge moulded a few wheel discs in just a few minutes.  Cut them out, paint them and glue to foam wheels - job done.

With fuselage and wings mylar covered I used the craft cutter to cut the decals from black acrylic sprayed decal paper.  First I did a trial cut on white copy paper to check size and general appearance.  CAD and the ability to use a .dxf file straight from the CAD program into the craft cutter made this easy.  Generous application of Microsol allowed the decals to easily float into their correct positions and suck themselves flat onto the covering.  Too bad about the lumps and bumps.  

Well, there's always next year. Grin
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Mefot
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« Reply #3 on: April 17, 2017, 01:25:55 PM »

It all looks good to me Ralph, particularly your novel method of thrust adjustment.

With almost a year to get it trimmed there's no excuse for not entering it next year !!!  Grin
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DavidJP
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« Reply #4 on: April 18, 2017, 04:18:59 PM »

 Nice!  Reminds me to find my bits - could finally make a FF Nats in a year or two for the AM/MA plan event.  But still need to sort out the pseudo diesel Redphin.  Looks as though will have to get my chum to machine a piston and liner!!

Yours is much more faithful to the original of course so well done. But a bit of an anaemic carrot what?
« Last Edit: April 18, 2017, 04:29:56 PM by DavidJP » Logged
SP250
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« Reply #5 on: April 18, 2017, 04:46:09 PM »

Ralph

What did you do to dull down or matt the silver mylar so it looks like silver doped fabric?

John M
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RalphS
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« Reply #6 on: April 19, 2017, 05:53:51 AM »

What did you do to dull down or matt the silver mylar so it looks like silver doped fabric?

Hi John,   Just cover with dull side of mylar on the outside and lightly airbrush with Tamiya XF-16 Flat Aluminium acrylic paint.  Degrease before spraying with Methylated spirit or similar.

Ralph
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SP250
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« Reply #7 on: April 19, 2017, 01:08:51 PM »

Thanks Ralph

Bring it along on Sunday - i'm sure other folk would like to have look at it as well as me.

John M
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OZPAF
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« Reply #8 on: April 19, 2017, 07:29:07 PM »

Bit of a pity Ralph - that's a really nice effort. However next year Smiley

happy building
John
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RalphS
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« Reply #9 on: April 20, 2017, 10:20:33 AM »

Thanks for the sympathy but that's what comes of changing techniques.  However, the wings are tiddly little things and a few key strokes have already changed the rib design to accept an upper spar and the craft cutter will be sent new instructions and, hopefully, a decent set of wings will quickly appear.  On the other hand I was very pleased with the cutting accuracy of both the balsa and the decals.  Photo shows the fuz and upper wing with decals added. 

Our club A2 contest is next week and I will be flying my Lucifer - now that is a wing. 
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RalphS
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« Reply #10 on: April 20, 2017, 11:14:17 AM »

But a bit of an anaemic carrot what?

The Aeroplane Monthly article gives the colour as yellow-orange.  Through a friend, the manager of the Avro Heritage Museum thought that it would be Chrome Yellow. Photographs showing the Avis prior to the final finish show it to be very dark.  I wonder if it was painted in the dark red dope undercoat given to fabric covered planes right up to the Hurricane.  I imagine the Avro workshop manager saying to the painter with the yellow paint "don't put too much paint on lad it's too b..... heavy already".  So the red grinned through (technical term) giving the yellow-orange colour.  I don't think anyone will ever know exactly what colour it was.  Picture from Manchester Art Gallery showing red paint on Hurricanes during manufacture.  I seem to remember that you like Art.
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DavidJP
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« Reply #11 on: April 20, 2017, 04:05:50 PM »

Your latest picture shows a much more carrot like colour - but just teasing really.  I have seen aircraft finished in that "red" in your Hurricane picture and my recollection is that  it was far less "red" - more brown, and i remember also a piece of fabric from a Wellington which admittedly had possibly faded looked almost brown.  Colours of paint finishes has been a subject argued about since they started to paint unbleached linen so in truth, my view is that very few people today are an authority on colours. I knew someone who worked in the spray shop at Longbridge during the War and said that colours did vary because they mixed the paint there for spraying the bombers and it depended on how accurate the operative was with the proportions and how long it was "mixed".  But there was a War on and apart from the mandarins in the MAP no one really cared, particularly the crews!  They paid little attention to the finish being too busy with other things!

So unless you meet someone who was there and has very accurate recall I doubt anyone can authoritatively challenge you.
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