Wide Body Avro Atlantic

[kitnut617]

First off, I don't need a lesson on how a turbojet works, I'm fully aware on it's operation

The Vulcan B.2 was powered by four 20,000 lb dry thrust engines, the holes through the rear spar were big enough to accommodate the exhaust pipe for each of these engines.  If I take a high bypass engine of say 75,000 lb dry thrust which has a bypass ratio of 8:1, that gives the hot exhaust a thrust of only 9,375 lbs, the rest of the thrust is bypass air.  Basic thought here would suggest that the hole in the rear spar has more than enough size to accommodate the exhaust pipe, even to the point that it could even be reduced in size.

Likewise, if I use four 25,000 lb dry thrust engines of about 4:1 ratio, the hot exhaust gas thrust is only 6,250 lbs. Again I would say the holes in the rear spar are plenty big enough to accommodate them. And then if I use a modified Harrier engine, the hot exhaust thrust is equal to the bypass air, so that would again make the holes big enough as the exhaust thrust is only about 12,000 lbs

Now go to post #49 and look at the top sketch again, there's a note pointing to two areas where is says " Engine bypass air flows over and under original wing chord profile".   I'm not sure what your interpretation is of that.

Going back to post #35, the photo of the RB-57F shows a strake on either side of the nacelle which starts at the rear of the bypass cowling and extends down the nacelle, there are similar ones under the nacelle.  These strakes form a "channel" to which the bypass air is "channeled" down, is that plain enough for you ?

[Supertom]

Read it.  I cannot see the "channel".  I can see the fan exhausting basically above and below the central engine nacelle - which is not evident in your notes attached to the sketches.  I must admit I missed that threat, concentrating on the sketches.  

This may simply be a misunderstanding, nothing more.  I felt you hadn't taken adequate consideration of the exhaust, that's all.  From your comments you feel you have but I can't find anything in the explanation which indicates that you have.

Wait, you do realize that you guys are splitting hairs over a detail that's theoretical, won't be seen on the completed model, and that the model will not actually fly, right?  It's not the point of this discussion.

As a wise man with coconuts once said, "it's only a model..."

[Green Dragon]

This is a VERY rough sketch of the way I read the engine idea. Hope it helps and if it's totally wrong I send my appologies!


Paul Harrison

[kitnut617]

Not being sarcastic here, but someone here can see what I'm trying to say.

That is just what my idea is Paul  -- thanks

[rickshaw]

Not being sarcastic here, but someone here can see what I'm trying to say.

That is just what my idea is Paul  -- thanks

Now I understand what you wanted to say.  However it was not IMO very clear from what you had posted.  I merely sought clarification.  As I suggested it was a misunderstanding, nothing more, OK?  There was no need to go defensive.

That now being cleared up.  I wonder whether it would work?   What happens to the airflow, in the fan, when air entry is abbreviated by the wing structure?

[Thorvic]

Brian this a build thread if you want to discuss Engine dynamics then start a new thread in the General Chat section and let Robert get on and build his "What-If" model.

[McColm]

Thanks for the explaination, you don't happen to know how a 'Ram jet' works?

[Supertom]

DUDE.  SERIOUSLY.  END.  OF.  ENGINE.  DISCUSSION.  

[kitnut617]

While I'm eagerly awaiting the release of a 1/72 767 (sometime this year I was told) I'm going to get on with the standard Atlantic I was planning to build.  I have all I need in the stash so just needed a KUTA to get it going.  This all came about because I picked up another Vulcan kit a week or so ago and I've been looking at how I would go about it.

I'm going to work out the wing to fuselage connection using my drafting CAD program but first I need a couple of chord profiles to work with.  With the Airfix kit the outer wing parts join on at the same place the real ones do, just outboard the engine bays, so getting this profile is just a case of putting it on a piece of paper and tracing around it.  The profile I really do need, the chord between the engine bay and fuselage, is a bit more problematic as I have to cut the inner wing off the fuselage to get it.  The problem here is the fuselage shape helps to keep the wing shape so cutting off the wing makes it too flexible and it won't keep it's shape.  What I have to do is re-enforce it first ---

[kitnut617]

What I've done here is to assemble the air intake ducts and dry fit them onto the tiny posts that are in the bottom half of the fuselage/wing



then ran glue along the top edge of the ducts where it will contact the top half of the fuselage/wing. Once this was dry I pulled the halves apart (which had the ducts in the top half) then added some styrene strip to hold everything firmly.




Once this was dry I glued the two halves together but before doing that I glued in the bomb bay fairing for the Blue Steel.  I made this much stronger by adding more styrene strip along the whole length of the bay sides as the kit has only four little triangles to hold this part in.




Here I'm making sure it all holds together right



This is now ready to go to the saw and have the inner wings cut off.

[kitnut617]

I started working on the Atlantic fuselage, for this version of the Atlantic I'm going to use a B-36 fuselage for most of it but use a 737 forward fuselage for the front.

Here's the two fuselages I'm using, the Monogram B-36 (which just happens to be 12'-6" diameter) and a Combat Models 737-100 (got this cheap because there's some flaws in the moulding and I told the owner I just needed something to cut up)



I decided to cut the wing root and bomb bay out of the B-36 fuselage and rejoin them after some more styrene strip was added for re-enforcement





Then I glued the two ends back together



I will have to do something similar to the front end where the 737 fuselage joins on, I'll do a 'Z' cut from just behind the gunners window hole, down to the centerline of the side then cut horizontally to a point that is just in front of the gunners window



I haven't decided yet what to do with the rear end but it will have to be about 8" long.  I'll probably have to scratch build this bit.

[kitnut617]

Just looked on the Aircraft in Miniature website to see when the ETA is for the 767, it's now available ---  

So the shopping starts, fan fronts from Braz, Vulcan white metal u/c legs from Scale Aircraft Conversions, Vulcan wheels from Mastercasters, hmm! what else do I need ---  ah yes, decals. Now what scheme to do, one will have to be Canadian

[Brian da Basher]

Woah some B-36 whiffery....love it!

Great to see you tackling such a monster project, Robert! I want to see more!!!

Brian da Basher

[kitnut617]

Thanks Brian ---

Anyway, I've got the nose on now.  It went on fairly easy which was a surprise, the 737 vacuform is only .5mm thick (and very flimsy) whereas the B-36 plastic is 1.5mm thick.  It didn't come out too bad I think.



Now a bit more challenging thing is next, I have to scratch build the tail cone.  Actually they will have to be two half cones as the top half of the rear fuselage cone is shorter in length than the bottom half.  ""Give it some thought I will""

The cones are actually called 'paraboloids' because the profile has a curve to it.  It will probably go a bit like how I did the air intakes on my STOVL Canberra.

I've decided to keep the radome too, backstory will explain everything (when I get around to it     )

[ChernayaAkula]

<...> It didn't come out too bad I think.
<...>

Not too bad?  That nose looks like it was never meant to be anywhere else but right there on that very fuselage!