kitnut617 Posted September 12, 2009 Author Share Posted September 12, 2009 (edited) This is the diagram John Adams provided and given me permission to post here. I'm basing my proposition for the nacelle location around where the load cg is shown here. The end result should be something like this. What I find interesting is that this new position of the nacelle actually puts the outer wings root leading edge right where the Harrier wing's root starts, plus as I've already said, the main u/c falls directly under the spar I put in which I believe is where the real world spar would be. Funny how things work out ------- EDIT: I've just noticed in the diagram, it gives the main spar location, I've got mine in the right place. Edited September 12, 2009 by kitnut617 Link to comment Share on other sites More sharing options...
xffw45343tg Posted September 12, 2009 Share Posted September 12, 2009 Don't forget that the most important calculation would be the position of the centre of thrust of your engines which will need to be within striking distance of the aircraft CoG. I need to look up the precise figures but off the top of my head, the Pegasus gives about 58% from the aft nozzles and 42% from the fan... (Nice bit of modelling btw) Kirk Link to comment Share on other sites More sharing options...
kitnut617 Posted September 12, 2009 Author Share Posted September 12, 2009 Don't forget that the most important calculation would be the position of the centre of thrust of your engines which will need to be within striking distance of the aircraft CoG. I need to look up the precise figures but off the top of my head, the Pegasus gives about 58% from the aft nozzles and 42% from the fan...(Nice bit of modelling btw) Kirk I had a look on the internet for that Kirk, but all I could find was 'the front and rear nozzles have about the same thrust'. I read though that the fan has about a 1.2:1 bypass ratio but if it's as you say, that means I can move the nacelles back some which I would like to do anyway. Thanks for the heads up on that as I had wondered if they were exactly the same, and if you could confirm the difference it would be greatly appreciated. I would need the thrust measurement of a GR.7 or 9 though, as this is what I have in mind as a power unit. Or even the 25,000 lb thrust engine. Robert Link to comment Share on other sites More sharing options...
xffw45343tg Posted September 14, 2009 Share Posted September 14, 2009 Harrier.org.uk (here) confirms my "top of the head" 42:58 split. I have more precise figures somewhere - I'll see if I can dig them out tonight. It stands to reason that this split would not change TOO MUCH between engines destined for the same airframe, so I'd guess the 11-21 and 11-61 (as found in the GR7/GR9 and GR7A/GR9A respectively) have the same distribution. Kirk PS/ This book is likely to be useful. Haven't got mine yet so can't tell you much about it. Link to comment Share on other sites More sharing options...
kitnut617 Posted September 14, 2009 Author Share Posted September 14, 2009 (edited) Thanks Kirk, had a look at the .org link, very interesting. One thing I noticed though when I clicked on the 'propulsion' link, it says the 58% comes out of the front nozzles via the plenium, the other 42% then goes through the engine which when mixed with fuel and burnt then produces about the same thrust as the front nozzles when coming out of the hot end. I'll keep reading through it later but it has already given me my answer to a question I had, 'where's the cg of the aircraft?' and it says dead center of the nozzles. That book though has just gone on my shopping list too. Cheers, Robert Edited September 14, 2009 by kitnut617 Link to comment Share on other sites More sharing options...
xffw45343tg Posted September 14, 2009 Share Posted September 14, 2009 Oops. That could be lazy reading on my part, but I'm pretty sure the thrust is NOT equal between the fan & hot end. Like I said, I have another source of info which I'll try & check tonight. CoG is a bit of a movable feast on a Harrier (as on any a/c I suppose) but I could do with those figures before making wild assertions. Watch this space. Link to comment Share on other sites More sharing options...
xffw45343tg Posted September 15, 2009 Share Posted September 15, 2009 I can't seem to find the figures that I've read that lead me to think the hot end exerts more thrust. I have other books to try but won't see these until later in the week. I did learn that the Pegasus' CoG is near as makes no difference on the line of the mounting trunnions which are located just aft of the fan nozzles (which makes perfect sense if you see one on a crane). There's a nagging feeling that the info was discussed on a forum like PPRUNE. So - I'll keep looking. Link to comment Share on other sites More sharing options...
bexwh773 Posted September 15, 2009 Share Posted September 15, 2009 Robert, This is a most impressive bit of work so far, and I cant wait to see more Bexy Link to comment Share on other sites More sharing options...
kitnut617 Posted September 15, 2009 Author Share Posted September 15, 2009 Thanks Bexy, I'll try to keep going on it, got some real world work to do at the moment which has to be done. Kirk, don't worry too much about it, I think that the cg is close to the center of the four nozzles and if it's a bit off, we can always say there's more fixed weight somewhere else that moved it. Link to comment Share on other sites More sharing options...
xffw45343tg Posted September 17, 2009 Share Posted September 17, 2009 Kirk, don't worry too much about it, I think that the cg is close to the center of the four nozzles and if it's a bit off, we can always say there's more fixed weight somewhere else that moved it. Sorry it's been bugging me that I'd read something about this and I finally found it in a copy of a paper delivered to the Society of Engineers by some bloke called John Fozard, who seems to know a thing or two about Harriers . So, although the engine's CoG is just aft of the fan nozzles, the thrust centre is (as you say) pretty much equidistant between the fronts and rears. Figures quoted are for a Pegasus 11 (not sure which Mk but I'd guess the 103 as found in the GR3) and are:- Fan: 58% Mass, 360m/sec, 105deg C Hot: 42% Mass, 550m/sec, 670deg C ...which ties in with Harrier.org.uk but clarifies that the hot end is taking a smaller air mass but accelerating it to a much higher velocity and temperature to balance the slower, greater air mass being emitted at the front. If you are a much better physicist than I (not hard) and I find you the distance between the nozzles (approx 1.8m) then you may be able to calculate the thrust centre for yourself - but I reckon your "its about in the middle" is absolutely the right approach for your model. Phew, I can sleep again. Kirk Link to comment Share on other sites More sharing options...
kitnut617 Posted September 17, 2009 Author Share Posted September 17, 2009 Thanks Kirk, and yes that Fozard guy is quite something, just been reading about some engines he was involved with in the BSP, Hypersonics etc book. Ramjets this time. I'm not much of a physicist or mathematician either so I'll go along with you on this. LOL. Link to comment Share on other sites More sharing options...
kitnut617 Posted September 23, 2009 Author Share Posted September 23, 2009 (edited) Not a lot done this last week or so, other things to attend too but I've had to change my plans a bit after following what I've read in the Harrier and Sea Harrier thread on the What-If forum. I was going to use the GAU-12 gun pods (Plan 'A') but then changed my mind to go with the GR.5/7/9 gun pods instead (Plan 'B', keeping it compatible with the Harriers). But it turns out the GR.5/7/9 doesn't have a gun So it's on to Plan 'C' or Plan 'D' Plan 'C' is to go with the Harrier 30mm gun pods (we know they had guns --right !!) or Plan 'D' , to go with a Canberra gun pack in the bomb bay, move it forward (to keep the expendable load around about the cg point) and then add big strakes to it. Decisions, Decisions --------- Edited September 23, 2009 by kitnut617 Link to comment Share on other sites More sharing options...
sartois66 Posted September 23, 2009 Share Posted September 23, 2009 This is really not what I'm interested in, but I just can't help watching the progress on this! It is quite amazing and a real credit to you, kitnut. Can't wait to see it finished. Cheers Kirk Link to comment Share on other sites More sharing options...
kitnut617 Posted September 30, 2009 Author Share Posted September 30, 2009 I've managad to spend a couple od hours on the project today but been a bit busy just lately so this is the first I've done anything to it for a couple of weeks now. I've cut out the top of the new nacelle to form to the wing, I had to be a bit careful as the chord on each side of the nacelle is completely different. I used the profile gauge as before but I moved one of the little wires out a bit just where the cg point is, this was to make sure the two sides correspond when I mark the line for cutting. This is the end result, when I cut the shape I left a bit extra then carefully trimmed it down until the nacelle fitted nicely in the position I wanted. Here's the nacelle matched up to the wing, it hasn't turned out to bad. I've saved all the top of the nacelle I cut out, as most of it will go back in just like how it was done with the fuselage. I had a bit of a set back though, I dropped the wing and in the photos you can see what happened, the starboard wing broke off, the only good thing about it is I'm not working on that side. Also you can see that nothing is really glued together as I figured I'd do as much cutting and dry fitting before I did that. Now that I'm at this point I can get on with the other nacelle and get some glueing done as most of the working out on how to do something has all ended and what's left is to duplicate the rest. I hope to get a bit more done over the next few days. Link to comment Share on other sites More sharing options...
Nick Belbin Posted September 30, 2009 Share Posted September 30, 2009 Nutter . . . Link to comment Share on other sites More sharing options...
kitnut617 Posted October 1, 2009 Author Share Posted October 1, 2009 Nutter . . . Link to comment Share on other sites More sharing options...
xffw45343tg Posted October 1, 2009 Share Posted October 1, 2009 Quick thought: What are you going to do about a reaction control system? Whilst the Harrier airframe's pitch down control would probably be OK, you've no roll, yaw or pitch up at present... Link to comment Share on other sites More sharing options...
Nick Belbin Posted October 1, 2009 Share Posted October 1, 2009 Yep, that's about right!! Actually, I really enjoy these flights of fantasy and some of the problem-solving that accompanies them . . . Link to comment Share on other sites More sharing options...
kitnut617 Posted October 1, 2009 Author Share Posted October 1, 2009 Yep, that's about right!!Actually, I really enjoy these flights of fantasy and some of the problem-solving that accompanies them . . . Cheers Nick, wasn't sure how to take your comment so tried the easy way to answer. When I do my 'flights of fancy' I try to make them possible, I've read about the Meteor (RA490) which had been converted to 'jet deflection' after it's work as the Metro-Vick Beryl test bed and the tests proved to be quite a success, and along with the pictures I posted at the top of the thread, this project more or less falls into the catagory of 'Could have been'. The only thing that is very iffy, is the relocation of the wing, not sure if that could have been accomplished like that but it makes space where I need it. Link to comment Share on other sites More sharing options...
kitnut617 Posted October 1, 2009 Author Share Posted October 1, 2009 (edited) Quick thought: What are you going to do about a reaction control system? Whilst the Harrier airframe's pitch down control would probably be OK, you've no roll, yaw or pitch up at present... Hi Kirk, My intention it to have all that in the booms sticking out the back of the nacelles, these could have three vents each at the end where they will be one on top, one at the bottom and one facing outwards on the side. My thinking is if as on a Harrier you have a vent that can push up then equally you could have a vent there that pushes down. The only thing I'm wondering about is the roll control, as this has two lift streams spaces quite wide apart as opposed to just the one on a Harrier, would the roll puffers be needed. I've had a look at my pictures of the AW.681, Dornier and Gloster and although I know they are mostly just paper projects, there doesn't appear to be any roll control. On the Dornier you can see the other puffer controls as I explained how I intend to do this one, they're right at the end under the fin and there doesn't appear to be any in the nose. Edited October 1, 2009 by kitnut617 Link to comment Share on other sites More sharing options...
xffw45343tg Posted October 1, 2009 Share Posted October 1, 2009 To be honest, it's above my level of expertise to establish if such a system would work. From the lowly level of "armchair engineer", I'd be concerned that the Harrier's RCS wouldn't be sufficiently powerful for such a significantly larger aircraft with the outlets in the same place. The logical thing to do is to get the valves at the aircraft extemities, though you are perfectly right to suggest that you could get pitch control from a single "end". I've a feeling that I've read that the Harrier's system is spread out as it is to stop the RCS valves in the tail boom melting in use. But that could be a figment of my imagination. I'd also want to have a think about redundancy; although if an engine failed then clearly you couldn't land vertically so the RCS becomes irrelevant. Given this, there's no reason why the roll control couldn't be provided by each engine separately, with a duct to the wing tip (for greatest efficiency) thrusting up or down as it does in the Harrier but each side powered by its own engine. I've a feeling if RR were involved, there'd be redundant systems everywhere. Anyway - this is pure speculation. Keep up the modelling, it's coming along nicely. Cheers, Kirk Link to comment Share on other sites More sharing options...
kitnut617 Posted October 1, 2009 Author Share Posted October 1, 2009 I'm much the same as you Kirk, an armchair engineer. I go on what I read or what people who know have told me, and there's something to what you say about the puffers melting. John Adams told me that the puffers eject air from the hot end. If the project was to use just the Harrier puffers, then I would say your comments are correct about them too, but there's two of them so double the power except in the yaw. I could change that by having a larger tube running to the puffer vents at the rear. In the event of an engine-out in the hover I think the only option is to 'get-out-as quick-as-you-can' just like in a Harrier, in level flight it could be landed like a conventional aircraft. I wonder what the implications would have been if there was an engine out in the hover on that Gloster project, I can't imagine all the passengers being in ejection seats I'll keep in mind the roll puffer too, there's going to be ECM pods on the wingtips (left over from my Nimrod) so these could be permanent pods incorporating the puffers. Link to comment Share on other sites More sharing options...
dambuster Posted October 1, 2009 Share Posted October 1, 2009 How is it done on the Osprey? Same principle could apply here. Peter Quick thought: What are you going to do about a reaction control system? Whilst the Harrier airframe's pitch down control would probably be OK, you've no roll, yaw or pitch up at present... Link to comment Share on other sites More sharing options...
kitnut617 Posted October 1, 2009 Author Share Posted October 1, 2009 How is it done on the Osprey? Same principle could apply here.Peter I don't know how it works on the Osprey (V-22 ?? ), anyone know ? Link to comment Share on other sites More sharing options...
xffw45343tg Posted October 3, 2009 Share Posted October 3, 2009 Tilting rotors like a helicopter & differential power between the 2 engines I think... little resemblance to a turbofan. Link to comment Share on other sites More sharing options...
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