Craig Spence Posted March 23, 2011 Share Posted March 23, 2011 Hi all,I have been looking at some build blogs on jets (fuel powered and edf) the builds always look very interesting and I may consider making one in the future (edf), trouble is I prefer ic but as you all know ic jets cost a fortune all up.So my mind started drifting (as it does most days) and I thought can you incorporate a conventional engine say an Irvine 53 or OS 46 into a ducted fan setup? I know it sounds daft but I'd like to hear peoples thoughts.Could one of the above said engines spin a fan in a tube?, or could you spin a prop in a tube (giving that both ends are open to air flow)?.I know it's not done for a reason but why, engine burn out, engine not powerful enough?. Also I know fitting the engines and starting them would be somewhat impossible but I'm sure some clever sod out there could think of a way.Thoughts please, amusing or thoughtful all welcome.Cheers all. Quote Link to comment Share on other sites More sharing options...
Tim Hooper Posted March 23, 2011 Share Posted March 23, 2011 IC ducted fan used to be the only way to do it! I'd advise a good set of ear defenders though...... tim Quote Link to comment Share on other sites More sharing options...
MarkyMarc Posted March 23, 2011 Share Posted March 23, 2011 Yes - that's how it used to be done in the 80s. Highly tuned engines turning silly rpm. Look up Bob Violet and IC ducted fan on Google Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 23, 2011 Share Posted March 23, 2011 CraigCurrent EDFs spin pretty fast 20,000 rpm or more, rather beyond most IC engines. You could build really big (expensive) and then you might get the fan down to IC speeds. It is the powerful high speed brushless motors that has made EDFs really practical. Quote Link to comment Share on other sites More sharing options...
John Privett Posted March 23, 2011 Share Posted March 23, 2011 Craig, as the others have said, it used to be common-place. Well, amongst those who built jets anyway! Some engines were designed and built specifically for ducted fan use. Starting was (I think!) either with a "wand" inserted into the appropriate place, like starting an i/c heli, or with a pulley and belt using an opening hatch - like with i/c model boats, or the earlier i/c helis. Quote Link to comment Share on other sites More sharing options...
Phil 9 Posted March 23, 2011 Share Posted March 23, 2011 Edited By Phil B on 23/03/2011 19:22:59 Edited By Phil B on 23/03/2011 19:23:29 Edited By Phil B on 23/03/2011 19:23:56Edited By Biggles' Elder Brother - Moderator on 23/03/2011 20:32:25 Quote Link to comment Share on other sites More sharing options...
Craig Spence Posted March 23, 2011 Author Share Posted March 23, 2011 I had no idea that is the way it used to go, I'm gonna have to do a bit more research into this lol!.I was just born early 80's so I missed that lol.Bob violet, I'll look him up first.Hi Simon, as I say I am an ic man. I do fly some electrics but don't know a great deal about them so please forgive my inexperience. But as I say I may consider an edf, but at the moment I am getting a picture of how these engines work in a jet ha, ha.Very interested in this, must have been a pig to fit the engines. Quote Link to comment Share on other sites More sharing options...
Craig Spence Posted March 23, 2011 Author Share Posted March 23, 2011 Those links looked interesting, nowadays though would there be any fans that could be adapted?. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 23, 2011 Share Posted March 23, 2011 David James of Clevedon was also big into IC ducted fans, and wrote several books on them. Nice chap too, serviced my rear induction Rossi 90 one day while I waited at his home. Anyway, back to topic - they were very noisy, often overheated, the fan units were mainly home made and notorious for throwing blades. The Thorpe brothers also were specialists in the field back in those days, and could supply commmercial fans - but they were very costly compared to todays composite /plastic jobs.Frankly, I wouldnt go near IC DF with a very large barge pole, even though I enjoyed the Wroughton jet meetings once every year, as it was all groundbreaking stuff back then.Today, electric tech has advanced so far and so fast, its simply the only sensible alternative to proper gas turbines for jets. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 23, 2011 Share Posted March 23, 2011 I did have this book, but now cannot find it, or I would send you it. Pete and Paul Thorpe ( Thorjet ) Quote Link to comment Share on other sites More sharing options...
Mowerman Posted March 23, 2011 Share Posted March 23, 2011 Some of us olduns remember when ic was the only way for DF. How many readers remember P E Norman and the Veron Lavochkin and FD2. which used small diesels ? One of each was built in the club I belonged to at the time but I dont recall either one ever flying. If any of those Veron kits survive could they be converted to EDF ?Edited By Mowerman on 23/03/2011 19:44:35 Quote Link to comment Share on other sites More sharing options...
sharpy1071 Posted March 23, 2011 Share Posted March 23, 2011 Yes mowerman, I've built both veron models from plans and flew them both with EDF, there is a U-Tube of a beautiful FD2, its worth looking at as he had more success than me. the big problem was where to put the batteries in the La. The FD2 was a simple build as far as where to put everything it was Cg problems that caused some head scratching!!BS Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted March 23, 2011 Share Posted March 23, 2011 I don't think the engines lasted very long in i.c. ducted fans. Bob Kress did some for Cox engines, some in plastic and some in plywood. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted March 23, 2011 Share Posted March 23, 2011 If I remember correctly they were often a bit "marginal" on power as well. Or was it just the ones I saw? BEB PS There was a guy did loads of plans for IC DF - "Pavel something" can't remember his name - anyone help me out?. I seem to recall he was Czech - is that right? It was a very long time ago. The plans are probably still available - he did a pretty neat looking MiG15 I remember. Edited By Biggles' Elder Brother - Moderator on 23/03/2011 20:39:05 Quote Link to comment Share on other sites More sharing options...
John Privett Posted March 23, 2011 Share Posted March 23, 2011 Posted by Mowerman on 23/03/2011 19:42:54: How many readers remember P E Norman and the Veron Lavochkin and FD2. which used small diesels ? He was a decade or two before my time, but I gather P E Norman was a familiar figure on Epsom Downs where I now fly. Indeed, our club secretary has recently built a few free-flight ducted fan models with small Cox engines. I think it's the .020 that he generally uses. Being free-flight they only have a very short engine run (5 secs. or so) so I don't think engine wear is much of a problem for him! Quote Link to comment Share on other sites More sharing options...
001 Posted March 23, 2011 Share Posted March 23, 2011 The Czech mentioned might be Pavel Bosak, I remember him more for pusher jet style models mainly made of sheet balsa. I have a book with very good drawings of early ducted fans, including centrifugal fans (vertical axis) I wonder if there would be any advantage using a large one now that powerful outrunners are available. (No motor blocking up the middle of the duct). Could fit well in a thick delta wing such as a Javelin. O.S., Rossi etc. used to make some very expensive specialised D/F motors, classics now. Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted March 23, 2011 Share Posted March 23, 2011 They were always marginal on power, yes - yet as a kid just learning R/C in the 80's I always dreamed of owning one. I think the best I/C ducted fan model I ever saw was the Thorjet F-5/F-20, it just seemed to achieve a most realistic flight envelope similar to the full size, great when moving fast but with a limited thrust to weight ratio... other models were always lacking in some regard, and often looked like they were flying underpowered, certainly not jet like really. But other than free flight (and PSS of course ), this was the only way at the time to own a scale jet without ruining the lines with either a tractor or pusher IC prop. 2-stroke engines used to rev to 22,000 rpm plus, on special high nitro fuel and with a limited life, often you'd have to use a new glow plug every other flight too! But thats how it was done before Gas Turbines and EDF were realised/practical/cost realistic. Ive got some shots to hand here of the 'Jet' Meet at RAF Abingdon taken in 1988 - Ill scan some and put them up on the forum, there was 1 home made gas turbine that year, every other model was IC ducted fan. Still a great meet none the less good memories! Quote Link to comment Share on other sites More sharing options...
Dave Towell Posted March 23, 2011 Share Posted March 23, 2011 Dont mention pulse jets......opps. Now they were LOUD!!!!!!!!!!! Quote Link to comment Share on other sites More sharing options...
Dave Towell Posted March 23, 2011 Share Posted March 23, 2011 Or you could speek yo this guy http://www.modelflying.co.uk/forums/postings.asp?th=49708 Quote Link to comment Share on other sites More sharing options...
Craig Spence Posted March 23, 2011 Author Share Posted March 23, 2011 Blimey, wasn't expecting so much feedback lol!. Good to see that it can be done though, but looking at the feedback it's clear to see why people no longer do it.It's good to see/ hear about some history on it though, a little rc history (for me anyhow, for some of you it's recent history, no offense intended). As I say I have been looking at some builds on edf's, I think I'm going to go for building one after my current project.I'd like to build one that I could glass and paint, I've seen a nice black bird (at least thats what I think it is). However I would also like to build it around my existing lipo stock (11v 2200mah. 20c about three of them).Does anyone have any thoughts on kits for this, also would it be cheaper building edf or buying new?.Thoughts please.Cheers all. Quote Link to comment Share on other sites More sharing options...
mal brewer Posted March 23, 2011 Share Posted March 23, 2011 Yes, P.E.Norman was one of the pioneers of i/c ducted fans,and his work was carried on by his son,Marcus,who was tragically killed in a full-size air crash,flying,I believe,a Stampe,but I could be wrong about the aircraft type.I remember the Veron kits ,designed by Phil Smith,coming out with the propulsion system mysteriously called the 'Imp' .This would be around 1952,with the first model the Lavochkin 17,then the Sabre,later the Fairey Delta 2,and finally a semi-scale delta called the Deltacepter.As schoolkids,we had many an argument about how the were powered,until we found out it was by a fan within the fuselage.The early fans consisted of a bent aluminium fan powered by an Albon Dart diesel of 0.5 cc.I don't know if any ever flew,they must have been very underpowered !................Mal Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 23, 2011 Share Posted March 23, 2011 My main concern would be the expected power you will achieve from the lipos you have.3s 2.2A @ 20C is not great for EDF, which suck a lot out of a battery. Realistically, those packs are probably only good for 30 - 35A and maybe only 10V under load.Now thats only 300 - 350 Watts. EDF jets tend to be at WOT almost the whole flight.Aiming for jet performance, we need around 150 Watts per pound at least, so with 300 on tap your model can weigh no more than 2lbs. Thats a pretty small SR71.Most of my current EDFs are using very high C rated batteries ( 30 - 50C+ ), which perform far better under heavy load. Quote Link to comment Share on other sites More sharing options...
Craig Spence Posted March 23, 2011 Author Share Posted March 23, 2011 Hi tim,Thanks for the headsup there. Need to do a bit of research then, what about dual/ or more edf's in one plane then?! That's gonna be some serious money on batteries really, see I would really enjoy building a scale edf. Trouble is lipo's cost a fortune, you do get some great deals but only occasionally, so my predicament would be I could build the plane and not fly it for a year lol!, but then that could work out ok I suppose, just buy a battery every couple of months plus a new charger.I'll have a look at a kit tomorrow and let you know, if you could advise on a power set up I would be very grateful.Thanks very much. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 23, 2011 Share Posted March 23, 2011 Simply adding more edfs to the same model gets you a ticket to the power to weight roundabout. Lipos do NOT cost a fortune - unless you shop at the wrong places! They are ridiculously cheap these days from the likes of GC or hobbyking etcI received a mailshot the other day that HK were selling 2200 3s lipos at under 9 USDThats around 6 quid! My early 2000m/a 3s Kokam lipos were almost 70 quid each a few years back Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 23, 2011 Share Posted March 23, 2011 Incidentally, for your first EDF I suggest you dont get a kit - buy a purpose designed ARTF which comes complete with fan and motor etc matched to the model. Quote Link to comment Share on other sites More sharing options...
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