Author Topic: McDonnell Douglas AV-19A  (Read 20502 times)

Offline kitnut617

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Re: McDonnell Douglas AV-19A
« Reply #75 on: January 29, 2013, 06:18:29 AM »
Thanks BdaB, my son was watching me do this over the weekend and he said to me, ' this would be neat if you were building it in 1/24 scale and make everything work as you think it should'. 

Got me thinking that ---  1/32 maybe -----

Offline ChrisF

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Re: McDonnell Douglas AV-19A
« Reply #76 on: January 29, 2013, 08:06:51 AM »
Ya better finish this one first !

Maybe call it practice ? ;)  lol

Offline elmayerle

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Re: McDonnell Douglas AV-19A
« Reply #77 on: January 29, 2013, 09:31:00 AM »
And this is how it looks now that the ducts are glued in to the model, I've painted around them so I can see what needs tidying up.
Very nice and quite elegant.  Do the cold flow ducts have variable vanes at their exits to give a limited amount of vectoring?  I'm thinking back to the cold exhaust nozzle vanes on the F-35B.

Offline kitnut617

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Re: McDonnell Douglas AV-19A
« Reply #78 on: January 29, 2013, 10:31:21 AM »
And this is how it looks now that the ducts are glued in to the model, I've painted around them so I can see what needs tidying up.
Very nice and quite elegant.  Do the cold flow ducts have variable vanes at their exits to give a limited amount of vectoring?  I'm thinking back to the cold exhaust nozzle vanes on the F-35B.

Thanks Evan, and yes that is what I'm thinking of, there will be about five of them on each duct. The idea is they will be able to rotate so they point five or ten degrees forward so that when in the hover the aircraft could move backwards (like a Harrier) and then they will rotate totally backwards until they close off completely and shut the duct off for forward flight.  And because the vanes are mounted on a hinged frame where the hinge centers are orientated for/aft, there's a certain amount of rocking that can direct the air stream to the sides, which will work in hand with the yaw control of the hot air nozzle. 

The idea is that all the controls for hovering go through these ducts and the hot exhaust nozzle instead of having 'puffers' like the Harrier has.  I had thought that something like an area control actuator in the duct that would vary the pressure in each duct for roll control, but I've had another thought.  I think what it needs is an actuator controlled vent on the top side of the fuselage and when the aircraft goes into the hover, these vents would be partially open so air would be always exiting upwards but only when in the hover.  For the roll control, these vents would either open or close opposite to each other, then for pitch up these vents would close off, and for pitch down they would fully open.  By doing this the vents would raise or lower the pressure in each duct and of course be infinitely variable.

Once all the PSR is finished and I get all the u/c on, I'll add these vanes to the ducts.
« Last Edit: January 29, 2013, 10:35:51 AM by kitnut617 »

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Re: McDonnell Douglas AV-19A
« Reply #79 on: February 02, 2013, 03:21:05 AM »
Ya better finish this one first !

Maybe call it practice ? ;)  lol

A scale model of his scale model... ;D
All hail the God of Frustration!!!

Offline ChrisF

  • Doesn't mind rough when he knows its gonna be rough...
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Re: McDonnell Douglas AV-19A
« Reply #80 on: February 02, 2013, 08:25:56 AM »
Ya better finish this one first !

Maybe call it practice ? ;)  lol

A scale model of his scale model... ;D

Dont pretend you havent at least thought of it yourself ;)

Offline kitnut617

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Re: McDonnell Douglas AV-19A
« Reply #81 on: February 11, 2013, 01:11:20 AM »
Got a bit more done, I've worked on the exhaust nozzle now.  I've made two, one as in forward flight and one for in the hover.  I've made them so they're a friction fit into the rear end of the engine, this way I can display the model two ways although the doors will always be in the down position.


Offline kitnut617

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Re: McDonnell Douglas AV-19A
« Reply #82 on: February 11, 2013, 01:15:09 AM »
I wanted them to have an appearance of having stiffeners on the outside of the pipe so I drew up some shapes which I then printed on sticky-back paper, then stuck to styrene (top pic).

I then cut them out leaving one staying all attached (2nd pic) and the other I split into sections (3rd pic)

Offline kitnut617

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Re: McDonnell Douglas AV-19A
« Reply #83 on: February 11, 2013, 01:21:16 AM »
For the straight through pipe I just glued the joined shape to some brass tubing but I used some aluminum tubing with thicker wall for the turned down pipe.  This was so there was more contact area for super glueing at the joints.  I forgot to take some pics of the straight pipe during fabrication, but it was similar to how I did the turned-down pipe. Top pic shows the two together but with no stiffeners on the turned-down one.  2nd pic is just a scale comparison with a quarter (about the size a 5P coin for our friends on the other side).  3rd pic is of the stiffeners glued on

Offline kitnut617

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Re: McDonnell Douglas AV-19A
« Reply #84 on: February 11, 2013, 01:24:21 AM »
Here's how it looks in the model, top pic is of the straight pipe attached to the engine, you can see I've cut the doors off the rear fuselage.

The others are with the turned-down pipe in place.

Offline Brian da Basher

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Re: McDonnell Douglas AV-19A
« Reply #85 on: February 11, 2013, 02:57:10 AM »
Those are some amazing details, kitnut! By the time you're done, you'll have everyone believing your AV-19A was real!

Brian da Basher

Offline taiidantomcat

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Re: McDonnell Douglas AV-19A
« Reply #86 on: February 11, 2013, 04:10:03 AM »
Holy cow! excellent craftsmanship!
"They know you can do anything, So the question is, what don't you do?"

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Offline kitnut617

  • Measures the actual aircraft before modelling it...we have the photographic evidence.
  • I'd rather be dirtbike riding
Re: McDonnell Douglas AV-19A
« Reply #87 on: February 11, 2013, 08:12:21 AM »
Thanks guys, the photos are really showing up the flaws though, it doesn't look as rough when I'm looking at the parts ----hmm!!

Offline elmayerle

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Re: McDonnell Douglas AV-19A
« Reply #88 on: February 11, 2013, 10:21:15 AM »
Still looking good so far.  I suspect the photos provide you with enough distance that you can see what needs tweaking, but I certainly don't see anything wrong.

Offline kitnut617

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Re: McDonnell Douglas AV-19A
« Reply #89 on: February 11, 2013, 11:34:09 PM »
Thanks Evan ---

Just a technical note,  I used round tube because in this scale it's easier to use (and get by with) but in the real world, the sections of pipe are not actually round, at least that's how they develop out as when I draw it correctly.  The reason is the angled connections are actually round because there's a bearing race there which means the short straight section parts are a round to angled round tranistion, and the middle straight section  is really an elipse in shape

This below might help with the explanation.  If you cut a round pipe at an angle, the resulting cut face is an elipse, in reverse, if the angle cut is actually round then the piece of pipe is really eliptical in shape