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Author Topic: Avro F monoplane, 1/20 scale for F4D  (Read 2874 times)
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g_kandylakis
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« Reply #25 on: July 27, 2013, 07:05:46 AM »

The Avro is basically a very simple plane, a mid-wing monoplane, nothing fancy.

But there are some areas that go well out of the ordinary. One of these was the front fuselage aluminium cladding. 1/3rd of the fuselage is done like that. To add to the problem, the cladding is full of windows. And to make matters worse, each window is surrounded by a black frame. And since there is so much transparency, even the opposite inside sides are visible...

My chosen way was to make a sandwich for each panel, made of plain paper with clear acetate in between. The window layout was printed on the paper, next each piece was folded and each window hole was cut with a sharp knife and ruler. Rivets were recreated with simple embossing brom the inside. Next it was painted with aluminium paint. Auxiliary help lines, indicating the position of each black line, were masked during painting and used as guidelines (literally ?) for the black frames. One or two small errors were corrected with some touching up. One panel had to be redone...
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Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
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g_kandylakis
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« Reply #26 on: July 27, 2013, 07:20:07 AM »

For the front bearing, I chose to try something new and maybe a little excessive for the size/type... The use of ball bearings. The front was attached on the front end of the crankcase, the rear on a plate that was made movable and can be adjusted for thrust changes. The pictured prop hook has been replaced by an S-hook.

Another new thing I wanted to try, was the result of many frustrating moments during contests. I always go to contests with new, usually untrimmed models (I know, I am not the only one...)
I do my test trimming and at the same time the model is needed for scale judging. So, I have to remove the flying prop and add the dummy scale prop... So, I cut the prop wire, remove everything etc. Then, I have to redo everything. It might happen 1-2 times during the day, which is devastating enough, especially with the lack of calmness at those times.

So, I thought of a way to make the prop removable, through a front screw, same as is done for CO2 motors. All this involved was to glue an aluminium tubing length to the hook wire (halfway in the wire). The tube was first given an internal thread, to match the small screws I had. It worked perfectly. More details when I take pictures of this and post them, it will be more clear. No time now...

George
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Re: Avro F monoplane, 1/20 scale for F4D
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« Reply #27 on: July 27, 2013, 08:58:52 AM »

Hi George
Thanks for detailing such an excellent build, your approach to the "everyday construction" is superb. Simple ideas as soaking the paper with Cyno before you drill the holes is brilliant, no furry holes. I also like your U/C jig, great ideas, not to mention the mind-blowing CAD and 3-D printed parts, something to aspire too. Kudos
Dave
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g_kandylakis
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« Reply #28 on: July 28, 2013, 01:06:54 PM »

Thanks Dave,

I like documenting some of the ways I use. Helpful for others, as are other inputs helpful to me...

Here are some pictures of the rather different approach I used for the front end of the prop hook assembly.

As I wrote in my previous post, seeing how easy it is to switch props in CO2 motors, I thought of finding a similar way for rubber powered models. Not necessary for everyday use, it is certainly handy in a competition model where a dummy prop is needed for judging. Also useful for changing and trying out different props during triming.

To achieve this, a screw thread is needed somewhere. First thought was an external thread, a piece of aluminium tubing, threaded on the outside and glued to the propeller shaft wire. A hexagonal nut would take care of the fixing.

The other option was an internal thread, in the same manner as a CO2 engine hollow crankshaft. For this the aluminium tubing needs to be threaded inside.

In either case, it is important and necessary to have a back plate, strong enough to resist the force of the screw or nut, during fixing.

Since we are talking about rubber power, the forces are not that high. The back plate was made of plywood, turned on a drill. The hole for the aluminium tubing was made a very tight fit. In addition, the tubing had its rear end slotted lengthwise with an X-Acto blade, to become serrated.
This had two effects. First it made the limited surface joint between back plate and tubing much stronger (the serrations (?) gripped well into the plywood), secondly the diameter of the tubing was slightly increased, adding a mechanical resistance against the force of the screw during assembly.

I chose the internal thread, mainly because I happened to have some extra 1,4mm screws from a Gasparin CO2 motor. The aluminium tubing was 2mm outer diameter, 1,1mm inner diameter. The hook wire was chosen 1mm as well, a little thick and heavy, but it is in front, so that helps with balance. Also, it matched with the small ball bearings I used, of 1mm inner diameter.  Grin

Of course, the same system can be used with a standard plastic nose bearing.

For the internal thread, at first I tried forming it with a screw, slowly working my way in and out, little by little. It took some time, but it worked.  Not a perfect thread, but it held. For the second attempt and with much better results, I used of a small tapping tool. After some search I found a not too expensive set of miniature sizes, useful for many similar modeling applications.

Only half the length of the tubing needs a thread, the rest is glued to the shaft axis.

I believe the sketch and pictures should explain the matter completely.

The assembly is as follows:

The tubing-backplate assembly has been pre-glued with CA, making sure the backplate is completely perpendicular to the revolution axis of the tubing.
Be careful not to let glue inside the tubing.

Prepare the main wire, forming the rubber hook.
Measure the needed length and cut the extra wire.
Insert the wire through the nose bearing (and nose block…)
Insert washers
Insert the tubing-backplate into the wire, about halfway (see sketch). Glue with CA from the rear side, not from the thread side. No matter how careful you are, there is great risk of glue flowing into the bearing and ruining everything. To prevent this I used masking liquid to seal off the wire-nose bearing area. White glue will do just as well. It is removed afterwards.

Only a little glue is necessary, too much can go and ruin the thread…

The props you intend to use need to be drilled to the same diameter (+ tolerance) as the aluminium tubing.

It goes without saying, that you cannot disassemble the system, once it is glued. The only way to remove is to cut the wire hook and throw everything away. Of course, there is no reason why one would want to do that…

The biggest obstacle is finding the necessary wire-tubing-screw sizes and, most importantly, the tapping tool… Also, to not lose the tiny screw… Angry

Last picture shows the dummy propeller with the front plate glued on it. It is just inserted to the tubing for judging and easily removed for the flying prop.

Of course, the same system is used for easily changing and trying different props. And if used as a standard in many models, it makes great sense…

Long post, sorry, but I hope it was interesting…
Attached files Thumbnail(s):
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
« Last Edit: July 28, 2013, 01:57:08 PM by g_kandylakis » Logged

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g_kandylakis
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« Reply #29 on: July 28, 2013, 01:36:21 PM »

that last picture shows something interesting...

During judging, the judges noticed that my prop was carved backwards, compared to the photographs, and pointed this out to me...A moment of great embarassment, for such a basic error  :'(

So, here is the second one, carved and waiting for finial sanding and painting. Too hot for these tasks now...

The funny part is, I later checked again my documentation and there is 1-2 pictures which show the prop the way I did it initially. But these were taken during mock-ups, so the prop might have been inserted backwards and I happened to use these pictures  Angry... Anyway...



Another different approach was for the rear rubber peg.
For personal reasons of scale appearance, I wanted to avoid having a visible peg extending from the fuselage sides. So I hid it... I made it permantent in the fuselage. I did add a paper tube, through which I pass the retaining wire of the stooge, during winding. Some lucky coincidence and calculation had the position of the peg exactly at the lacing area, so even the holes for the wire could be avoided. They are somewher in the side lacing  Grin

Of course, one might ask: and how do you attach the rubber ?

For this I got the idea-hint from german F1B modeller in a german forum. He suggested the use of a removable hook, as is apparently standard practice in F1B. Then, fellow member there and here, hastf1b made a downsized sketch and a quick rough prototype to show the idea...

http://www.rc-network.de/forum/showthread.php/235878-Scale-Modelle-F4D-F4E-F4F-Peanut?p=2109645&viewfull=1#post2109645

Some refining, and it worked. Still needs perfection to make it 100% dependable. And I do not know what happens if the rubber brakes during winding. On the other hand, this system was developed exactly so that the motor could be wound outside the model, then inserted at 45 degrees and rotated to 0 degrees clockwise, to lock the hook in the internal rear peg.

With practice and some fine tuning it should work very well. During the BMFA indoor scale nats it gave me some headaches, but not severe problems. If the model had already been trimmed, it would be nothing... And if I had prepared my equipment in advance... And if...

First picture shows the permanent motor peg made of basswood. The paper tube end is barely visible on the side.

Second shows the rear hook and an exact copy of the peg, used for testing and adjusting the hook. Some kind of special stooge is needed to put it in and out of the model. And that is all...
It could be a little better in focus, btw, sorry for that... Aluminium tubing, ply end plates, piano wire hooks. Weight ~0,3gr, not the best position for extra weight, but you can't have it all...


Anyway, enough with innovations...

George
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Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
« Last Edit: July 28, 2013, 01:54:52 PM by g_kandylakis » Logged

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« Reply #30 on: July 29, 2013, 05:06:09 AM »

Even though my skills are minimal compared to yours I am finding this thread highly motivating and inspirational. The concealed rear motor anchor is a brilliant idea.
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« Reply #31 on: July 29, 2013, 07:20:49 AM »

Hi George
This is a masterclass, and I look forward to the DH9!
Bill
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« Reply #32 on: July 29, 2013, 08:38:31 AM »

Hi George, I am glad that I could make a small contribution to your beautiful model. Smiley I wish you many pleasant flights with it.

Heinz
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« Reply #33 on: July 29, 2013, 01:59:39 PM »

Thanks for the comments...Heinz, thank you for the help  Smiley

Masterclass ?   Shocked 

Back to the model, as time came close to my deadline (April), the building rate increased and the documenting rate droped... So, some of the later stages will have to be shown wih current photographs and descriptions.

I need to add here, that the model is not yet finished. I did enter it at the BMFA Nats, but at 95% state. Another funny question I head from the judges (Paul Briggs specifically):
George, where is the tail skid on your model as shown in the original?
What tailskid? I do not remember a tail skid. Was there supposed to be a tailskid? (Better to sound surprised as having forgotten it, than admitting time was not enough  Grin)

Anyway, here some pictures of the covered fuselage. Each side was done in two pieces, the tissue glued just before the lacing holes. After doping and painting, the tissie edge dissappears and leaves a continuous surface, whixh was the effect I wanted.

The other two pictures show an ad-hoc solution to a problem that appears too often: how to secure parts after painting, when you have only one free hand. Fix them on a pin and use magnets...
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Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
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« Reply #34 on: July 29, 2013, 02:41:43 PM »

After everything was covered and doped it was painted with acrylic color, trying to simulate the off-white fabric of the original.

The black AVRO lettering was sprayed, using artool frisket film for masking (similar to badger but better, lower stick) to both sides of the fuselage and the underside of the wings.

Next, the front side panels where glued and trimmed to size.

Since it started to look the part, some pictures were taken at that time.

Top and bottom fuselage panels were next.



Attached files Thumbnail(s):
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
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« Reply #35 on: July 29, 2013, 02:58:42 PM »

George you are the best Greek model manufacturer in this category.
Good luck in your work.

Elijah Greece Xanthi.
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« Reply #36 on: July 29, 2013, 03:28:32 PM »



Masterclass ?   

"A master class is a class given to students of a particular discipline by an expert of that discipline—usually music, but also painting, drama, any of the arts, or on any other occasion where skills are being developed." I think that fits!
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« Reply #37 on: July 29, 2013, 03:36:48 PM »

Superb......
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g_kandylakis
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« Reply #38 on: August 07, 2013, 05:35:21 PM »

some more photos with details of the finished model.
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Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
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« Reply #39 on: August 07, 2013, 05:41:49 PM »

and the last ones for now...

Given that the model is not yet 100% finished (tailskid and some small details missing), this is still a current build log.

And the model still has to be trimmed, but that will have to wait until the autumn.

George
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Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
Re: Avro F monoplane, 1/20 scale for F4D
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« Reply #40 on: August 07, 2013, 07:01:04 PM »

STUNNING!
Dave
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« Reply #41 on: August 08, 2013, 01:48:40 AM »

george, my eyes are hurting.... Great as always!
Roman
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« Reply #42 on: August 08, 2013, 05:23:03 AM »

Truly amazing.
Some 1/4 scale builders would be jealous.

Paul
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« Reply #43 on: August 08, 2013, 10:45:52 AM »

 Shocked Shocked Shocked Shocked Shocked Shocked Shocked Shocked Shocked Shocked Shocked Shocked Shocked Shocked Shocked Shocked Shocked
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« Reply #44 on: August 10, 2013, 09:42:20 PM »

Outstanding, George!  You put us all to shame!
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« Reply #45 on: May 21, 2016, 06:23:44 PM »

Long overdue and quite delayed, here is a video fo the only qualifying flight of the Avro during Interscale 2015 in Nijmegen...

https://www.youtube.com/watch?v=qtrMi6vD3Rg&feature=youtu.be

I had (and still have) plenty of problems with thrust and center of gravity settings, plus too short a rubber... Must seem funny for such a simple model, but there are some fundamental errors built into it.

At least I got a qualifying flight on video to remember it.

Model had some minor damage, has been repaired since, but not yet flown again, due to lack of a suitably sized hall. Next Interscale, hopefully...

George
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« Reply #46 on: May 22, 2016, 03:13:38 AM »

George, even your videos are flawless, the same as your models  Cheesy

Thanks for a nice Sunday morning reading of your topic, not explored yet, but being studied carefully right now.

Urs
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« Reply #47 on: May 22, 2016, 05:27:50 AM »

Masterclass indeed.  And I think that looking at some of the detail pictures one could be forgiven for wondering if you are looking at shots of the real aeroplane.
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