xffw45343tg Posted July 15, 2008 Author Share Posted July 15, 2008 Photo 1 Isn't that ZH807? And is that from where the FA2 bits keep popping up on ebay? Hey folks. Great work on this machine Kirk!!! Thanks Stuart - just wish I had more time & modelling skill. Hope Dave's answer did the trick. The thing with the Harrier that I too find hard to get my head around is what happens in the hover, especially close to the ground. It was pointed out in an article that I read that the wings actually serve to suck the aircraft down in this regime and hence the size & shape of the (non removable) inner pylons and LID fences on the Harrier IIs. Apparently the aerodynamicists were well aware of this behaviour on the 1st generation aircraft, just used it as an excuse to ask RR for more power!! Without getting too technical... Go on, go on, go on, go on. You know you want to. I'll pretend I understand. Kirk Link to comment Share on other sites More sharing options...
Dave T Posted July 15, 2008 Share Posted July 15, 2008 (edited) Isn't that ZH807? And is that from where the FA2 bits keep popping up on ebay? Indeed it is, well spotted. Although i doubt any cockpit items appear on eBay. If so, the new owner would probably like to know. Go on, go on, go on, go on. You know you want to. I'll pretend I understand. Well, i'm no expert in aerodynamics, i just fix 'em. It's been a long time (20years+) since i sat through lectures on how a Harrier works, but IIRC the shape of the intakes helps to compress the air onto the fan face as well. (eg: squashed air = faster air) One question, are the blow in doors thick or just sheet metal? Jake, they are sheet metal approx' 3mm thick, although folded around and riveted to themselves to form a 'hole' that there mounting pins pass though, a bit like a gate hinge. Cheers........ . Edited July 15, 2008 by Dave T Link to comment Share on other sites More sharing options...
Stuart Posted July 15, 2008 Share Posted July 15, 2008 (edited) As this isn't enough ( the doors are loose btw ) when a Harrier stops in mid-air, the suction from the fan opens them thus drawing in more air......During forward motion at speed, the air outside is slower than inside the intake due to the fan 'sucking' it in also. Therefore by default, the blow in doors are forced out (i.e. flush) during normal flight... Hi Dave, thanks for the response. I totally follow and I understand the fast air/slow air situation. However, You state that in forward flight the air outside is slower due to the fan sucking air in (as well as it getting pushed in by the forward flight), which is obviously correct. So to summarise, the air is faster inside the intake in the hover as well as in forward flight...so why doesn't the fast air inside the intake pull the doors in all the time, due to the fast air sucking them in, like they do in the hover? Sorry for being pernickity and I'm please don't think I'm doubting you, I'm at best mediocre at physics!!! I just wish to understand more! Stuart EDIT: Is it because there's sorta "just enough" airflow outside during fwd flight to pull them flush? Edited July 15, 2008 by Stuart Link to comment Share on other sites More sharing options...
xffw45343tg Posted July 15, 2008 Author Share Posted July 15, 2008 Indeed it is, well spotted. Although i doubt any cockpit items appear on eBay. If so, the new owner would probably like to know. Think it was a HUD I saw, and a DDI from an FRS1. Someone "near Bristol" (IIRC) had a servicable Lucas GTS/APU test rig that I let Art Nalls know about (he missed it by a quid I think). These items rarely reference the aircraft they've been swiped from!!! Jake, they are sheet metal approx' 3mm thick, although folded around and riveted to themselves to form a 'hole' that there mounting pins pass though, a bit like a gate hinge. I also read somewhere that the hinge pins are sprung such that damaged doors can be twisted out and replaced by people with small hands (e.g. Maintenance Engineer's girlfriends). My hinges on the other hand are made out of cut down dressmakers pins and glued to a groove filed into the (approx 1.5mm thick) styrene doors with cyano and located with small strips glued to the inside of the intake parts. I think I may have been trying to be too clever in making them pivot as the construction of the walls makes it highly probable that they'll stick - but I should be able to push them into the "right" places. Stuart - I've got a Hawker-Siddeley diagram somewhere that illustrates the airflow during forward flight and hover. I'll see if I can dig it out. Cheers, Kirk Link to comment Share on other sites More sharing options...
Dave T Posted July 15, 2008 Share Posted July 15, 2008 So to summarise, the air is faster inside the intake in the hover as well as in forward flight...so why doesn't the fast air inside the intake pull the doors in all the time, due to the fast air sucking them in, like they do in the hover? Stu' Yes i see your point, but as i said, there is no airflow fast or otherwise, over the aircraft whilst hovvering. Therefore with no external force the doors (and outside air) are sucked inwards. There are more technical aspects to it, such as the shape of the 'bellmouth', going backwards (!), hovvering in a strong wind and the boundary air doors to name a few If Kirk has such a diagram it would be interesting for a bit of 'revision'. It's been a loooong time since i saw such a diagram on a projector !! Cheers...... . Link to comment Share on other sites More sharing options...
Dave T Posted July 15, 2008 Share Posted July 15, 2008 (edited) aha... here you go. Couple of diagrams from an 'old skool' book i've found. Airflow in the hovver Airflow in flight Cheers..... . Edited July 15, 2008 by Dave T Link to comment Share on other sites More sharing options...
xffw45343tg Posted July 15, 2008 Author Share Posted July 15, 2008 Those were exactly the diags I was talking about. :-) Link to comment Share on other sites More sharing options...
Stuart Posted July 15, 2008 Share Posted July 15, 2008 Those were exactly the diags I was talking about. :-) So there's small enough of a difference to allow the doors to be sucked closed. Cheers chaps. I understand *tips cap* Stuart Link to comment Share on other sites More sharing options...
xffw45343tg Posted July 17, 2008 Author Share Posted July 17, 2008 Just spotted this - which I think illustrates what I'm trying to achieve with the duct. Cheers, Kirk Link to comment Share on other sites More sharing options...
JakeEaton Posted July 17, 2008 Share Posted July 17, 2008 Brilliant picture, cheers Kirk. I see the blow in door 'walls' taper off in thickness as they go inwards towards the intake. Any idea what that white rod is? Link to comment Share on other sites More sharing options...
xffw45343tg Posted July 17, 2008 Author Share Posted July 17, 2008 Brilliant picture, cheers Kirk. I see the blow in door 'walls' taper off in thickness as they go inwards towards the intake. Any idea what that white rod is? I think its actually a strap - maybe to hold a FOD guard on to something on the outside. Certainly not part of the aircraft. This reminds me - I meant to say to you about the intake inner wall detail on the Airfix parts. Although the FRS1 kit is MUCH better than the GR3 (which is just cut off behind the boundary layer duct doors), there's still something not quite right. The inner wall should meet at a sharp edge in front of the fan but instead the edge is cut off. I think that perhaps the inward curve around the back of the wheel well starts too late so it can incorporate the over-wide pivot point of the NLG strut. When you're close to joining the cockpit halves, I'll post some pics on your thread to explain what I mean. On my GR3 I'm fabricating the missing wall from card etc - hopefully some pics of this next time I post. Cheers, Kirk Link to comment Share on other sites More sharing options...
JakeEaton Posted July 17, 2008 Share Posted July 17, 2008 I understand Kirk and this was a question I was going to ask (whether the intake inner wall curves round to meet at a point) I'll have a look at my parts later to see if the curve starts to far backwards. If this is the case, it should be relatively easy to just shorten the part by removing a plug of material just behind the boundary layer ducts and then building up the blunt edge to a point. From your pictures there also seems to be a couple of inches gap between the point and the blades of the turbines. Are there any exact measurements for this gap? Link to comment Share on other sites More sharing options...
xffw45343tg Posted July 20, 2008 Author Share Posted July 20, 2008 OK. A small update and some more pics (which I may have to edit later if I can't get them rotated properly with photobucket). I'm working on the inner walls of the intake. My plan is to join a couple of pieces of styrene to make the edge in front of the engine fan. First up is to make a template from card: This allows me to get the exact depth I want. The picture show the fitting against the intake parts which I've just balanced in place. I can see that I'll have to adjust the fit at top and bottom but it is OK to start with a pair of plain rectangles. Next job is to cut these from styrene. I then sanded the inner face to a chisel edge and glued the 2 pieced together with liquid cement. I added some cyano in there from the inside too once the styrence cement had set as I anticipate there being a lot of stress on the join during fitting. Once dry, I started fitting against the nose gear well. Although the real thing is pretty flat - maybe even slightly concave, there's just no way that I'm going to get the new parts to follow that line without completely compromising the main strut's retraction pivot point. Anyone who has an FRS1 kit will have an idea what I mean - whilst it is much better that the GR3 in this area, Airfix chickened out and left a big rectangle protruding into the duct. The upshot is that the curvature of the wall must be convex where it ought not to be. To achive this, I left the "V" shaped piece over the kettle for a few seconds then forced it into shape. I had to repeat this a couple of times until it looked like this: (Apologies for the quality all you photographers - rush job). I then roughly shaped a piece cut out of one of the kit's 1000lb bombs to form the central bullet. I think this is a little under scale diameter (It should match the diameter at the roots of the fan blades), but I'll work out what to do about that (if anything) later, when I cut the edge back for the a/c vents above and below it. Balanced on the "V"gives this: So now it's time to start testing against the model: I realised at this point that if I'm going to put in the rectangular section bleed air ducts under the large holes I've cut in the rear deck, they need to go in before cementing my intake in place. I've cut a couple of styrene rectangles to form the forward section of wall, and fitted them with the aid of some filler: I've not been able to be 100% sure about the shape of the top opening of the ducts; some Kingston factory pics show the inside tapering markedly towards the seat rail, other pictures make them look rectangular. I'm doing it by eye, and mine are now telling me that I've made them too vertical. Never mind - they're better than nothing I guess. In the shot above you should also get an idea of how much need taking off the aft edges of the wheel bay. I've tried to cut it back to just before the point where I break into the bay. It's paper thin now. Also illustrated here: ....And apart from some tweaks to the cockpit, that's as far as I got with the limited time available this weekend (friends to stay, child with chickenpox, blah, blah, excuses, excuses). But wasn't watching Lewis more fun than scraping plastic?? Cheers, Kirk Link to comment Share on other sites More sharing options...
JakeEaton Posted July 20, 2008 Share Posted July 20, 2008 Looking good Kirk. What are your thoughts on the OOB front gear bay? Also, are you detailing the engine as I see you've added a couple of bits in the engine compartment. Link to comment Share on other sites More sharing options...
Dave T Posted July 21, 2008 Share Posted July 21, 2008 Guys, Is this photo of any help ? I've blocked out the background in the interests of national security Cheers..... . Link to comment Share on other sites More sharing options...
Guest Drewe Posted July 21, 2008 Share Posted July 21, 2008 I'm actually most impressed by getting a thread title which is a word play on a Rush album. But the model looks good as well! Link to comment Share on other sites More sharing options...
xffw45343tg Posted July 21, 2008 Author Share Posted July 21, 2008 Well spotted Drewe. When they turn the pages of history, my GR3 will still not be finished!! But you can't get something for nothing... Link to comment Share on other sites More sharing options...
xffw45343tg Posted July 22, 2008 Author Share Posted July 22, 2008 Looking good Kirk. What are your thoughts on the OOB front gear bay? Also, are you detailing the engine as I see you've added a couple of bits in the engine compartment. The OOB on the GR3 or on the FRS1? Not to put too fine a point on it, that on the former sucks (but at least leaves a blank canvass), whereas the latter is filled with "Harrier inspired" (but ultimately inaccurate) detail. Take a look in one the pics below for what's in the GR3. I decided my lousy first attempt at the forward wall of the duct was just plain wrong and pulled out the card. If I'd bothered either looking at references or thinking about the fact that the duct doors must open onto the duct then I would have realised that they cannot simply drop vertically down from the upper apertures. They don't. So here's the 2nd attempt: In this pic I've inserted the aft wall of the ducts. I then cut out the holes through the "roof" of the NLG bay. This is the view of the super-detailed(!) OOB bay. Finally using some thinner card, I glued in the inner faces of the duct. There's a little filling to be done around the opening and I was planning on completing the duct sections that are found in the NLG bay but I'm fairly happy with this bit now. By the way, Jake, you may be able to see what I'm trying to salvage of the cockpit - shortened side panels, some filler in the floor etc... I'll post again separately on the engine and it's bay - brain too full to explain the plan for that. Guys,Is this photo of any help ? I've blocked out the background in the interests of national security Cheers..... . Really useful Dave. Many thanks again. That was the Trocadero bird again right? However, in trying to get closer to this shape, I think I've mucked up the part I made. If I can soften it in hot water it may be salvagable. Cheers, Kirk PS/ Am liking this BM thing - much faster progress even if my family now hate me for being an anti-social rivet counter. Link to comment Share on other sites More sharing options...
Dave T Posted July 22, 2008 Share Posted July 22, 2008 Kirk, Do you need some nosewheel bay photo's ? . Link to comment Share on other sites More sharing options...
xffw45343tg Posted July 22, 2008 Author Share Posted July 22, 2008 Always Dave. I wasn't going to go to town on this area - hoping that Jake will and that he can be persuaded to take casts!!!(although I think the Shar is a little different). If not, I'll probably limit my attention to the RCV duct, the accumulators and the door jacks. Was the real thing this much of a challenge? Kirk Link to comment Share on other sites More sharing options...
Dave T Posted July 22, 2008 Share Posted July 22, 2008 Was the real thing this much of a challenge? Yes... it is indeed a bar steward Some pics.... Forward Rearward . Link to comment Share on other sites More sharing options...
JakeEaton Posted July 22, 2008 Share Posted July 22, 2008 I like how you have gone about reproducing the ducts. As for the wheelbay, I'd have prefered it if Airfix hadn't touched them. The detail they've put in the FRS.1 bay is so thick that it's very difficult to grind off. As for detailing it, I don't think I'd have the patience or the sanity to do it exactly as it is. Also, the FA.2 forward wheelbay area is very different to the GR.3 which is a shame. We'll see how it goes I guess but if you know anyone who would be interested in some basic (compared to Aires etc) masters for the wheel bay or cockpit I'd be interested in producing some...bit scared of getting in over my depth though! I understand you're going to carry the ducts on into the wheelbay? Also, what are the cylindrical 'tanks' on the inside of the front wheelbay? They're all over the walls of the FA.2 bay! Link to comment Share on other sites More sharing options...
xffw45343tg Posted July 23, 2008 Author Share Posted July 23, 2008 I found the ducts reference pic I meant to post. Its here, in an interesting gallery seemingly taken at Faygate. Kirk Link to comment Share on other sites More sharing options...
xffw45343tg Posted July 27, 2008 Author Share Posted July 27, 2008 Hi. A tiny bit more progress: Some hot water brought the duct walls back into reasonable shape. I sprayed a bit of primer on/in the bleed air ducts enough for me to be happy that they're good enough to seal up, then stuck a couple of rectangular tabs on the inside of the upper part of the AC bay to help space my new insert. At the sharp edge of the "V", above and below the central bullet are vents for the AC heat exchanger - basically removing the sharp edge for half its length. I thought these might be tricky to remove once the duct is in place so I made a cutout before starting gluing. I also shaped the forward ends of the "V" to clear the circular shape of the main duct wall. Finally, lots of styrene cement and on went my duct. Once set I added some filler and rubbed it down before a splash more primer to see how things look. More filling needed but it seems OK. Sorry about the shadow on this one - better pictures when I have more time... Jake - the cylinders in the wheel well are hydraulic reservoirs for the gear retraction, nose wheel steering and bay doors as well as the nitrogen (/helium?) cylinders for emergency gear extension. I agree with your analysis of the Sea Harrier kit parts. I'll post some more comments about this on your build thread when I get a mo. All for now. Thanks for looking. Kirk Link to comment Share on other sites More sharing options...
Col. Posted July 29, 2008 Share Posted July 29, 2008 Top stuff so far Kirk! Between you and Jake there's gonna be a couple cracking 24th scale Harriers taking shape here Link to comment Share on other sites More sharing options...
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