Yostumpy Posted March 19, 2008 Share Posted March 19, 2008 Has any one of you out there done, or know of a study on aero dynamics on a defender. YES I know its a shed, but then so are firkin big Merc trucks, but these have been studied. You see I have a 110 ht with a full length roof rack, std galv box section cage. Now, when its raining, and say I'm going 50-60 on m-way I'm obviously driving into the rain, and if I look out of the side window, the rain appears to be at an angle of approx 45 degrees. WAKE UP!!!! BUT the rain that comes off the roof and falls into the roof gutter on the sides, goes the opposite way, I mean it ACTUALLY flies off back to front, ie, TOWARDS the windscreen from the raer door post area., Ive seen SO many large drops going the wrong way I got to thinking that there is either a vortex or a vacuum, caused by the flat screen. On trucks they now have those mini vertical spoilers about 10" long on the lower front panel, these must DO something. Some one out there must have access to a wind tunnel/ smoke machine, or a computer simulated program with a model of a defender in its program. Wouldn't it be great if a little plastic spoiler attatched either side ot the windscreen post gave us 35 mpg!!!!!!!!!! Wat do you think, Stumpy Quote Link to comment Share on other sites More sharing options...
siearl Posted March 19, 2008 Share Posted March 19, 2008 JUst a suggestion, You have far to much time on your hands. Quote Link to comment Share on other sites More sharing options...
Scotian Posted March 19, 2008 Share Posted March 19, 2008 It would be interesting to see if someone can show us. Once when I was out on a job in a Landrover the driver threw his fag out the window. then a few seconds later he started shouting to look. We were doing about 60 on the motorway and the fag was just floating there just outside the window in what I guess was an eddie created by the windscreen and wing mirror. Quote Link to comment Share on other sites More sharing options...
Guest diesel_jim Posted March 19, 2008 Share Posted March 19, 2008 Sorry, not much use! Quote Link to comment Share on other sites More sharing options...
Night Train Posted March 19, 2008 Share Posted March 19, 2008 I've not done a wind tunnel test on a Land Rover but I suppose I could do if I really have to. A 110 will be lousy. The sharp edges will cause lots of turbulance around the windscreen and the back of the body. If it was nicely rounded that would make a huge difference. I did a real life test on my Skoda Octavia estate for fuel economy a while ago. On a regular 230 mile return trip motorway drive: leaving the two roof bars on increased fuel consumption by 11%, opening the drivers side window added 15%, tyre pressures low by 10psi added 5% and was scary. This was based on regularly getting 60mpg on every standard run, same day of the week and same time of day, and making one change at a time. Quote Link to comment Share on other sites More sharing options...
hattymender Posted March 19, 2008 Share Posted March 19, 2008 There's an old film I've seen of a Buccaneer (low level bomber for those too young) 'dropping' a 1000lb Mk83 bomb. Except it didn't'. It got trapped in the boundary layer ('dead' air close to structure easiest description) and flew alongside for quite some way. Eventually it got bored, rolled down the underside of the wing and fell away. Also quite common is to find 'chaff' (radar blanketing stuff) which is fired out of the back stuck in doors and panels at the front of an aircraft. The point of this? Dunno really. Don't throw a cig out at 400mph? Boundary layer on 110 at 50mph bigger than a jet at 400? (wouldn't surprise me) Rich Quote Link to comment Share on other sites More sharing options...
hattymender Posted March 19, 2008 Share Posted March 19, 2008 And another thing........ Not only are the aerodynamics non-existent they've also got a carp radar cross section. I can get within 50yards of our local 'slow down' sign in a Focus (strictly at legal speeds of course ) without it picking me up. In my 110 it gets me from miles away. Which is ironic 'cos it's got such carp aerodynamics it takes a ten mile run-up to get anywhere near the speed limit. With a back wind. Downhill.................... Quote Link to comment Share on other sites More sharing options...
Night Train Posted March 19, 2008 Share Posted March 19, 2008 I don't think it would be a boundary layer on a Land Rover. Boundary layers form with very smooth flow over an aerodynamic shape where the flow becomes laminar. The turbulance caused by a Land Rover would prevent any laminar flow from forming. It would cause turbulance and eddies of rotating air that travels with the vehicle. It is the same sort of airflow that allows truck drivers to keep their mirrors clean with a strip of rag tied to their mirror arms. The air flow swerls around the the edges of the mirror and causes a low pressure against the mirror glass. This sucks the rag onto the glass and swishes at around wiping the mirror clean. The door mirrors and the widscreen edges would cause a similar effect around the area of the door glass. Quote Link to comment Share on other sites More sharing options...
hattymender Posted March 19, 2008 Share Posted March 19, 2008 I'm still trying to figure out which aerodynamic effect causes my washer jets, which squirt symmetrically at standstill, to always (and I mean ALWAYS) wash the nearside and not my side regardless of wind, gradient, phase of moon, tides, or whatever............... Quote Link to comment Share on other sites More sharing options...
Yostumpy Posted March 19, 2008 Author Share Posted March 19, 2008 Night train. I take it that from your post you have access to a wind tunnel, therefoer you presumably have access to the aerodynamics programs. Once you've done the test, then you can play with the air flow with theoretical spoilers, bonnet deflectors. I've not seen it done anywhwre foe a defender. If there was a simple solution, and was manufactured, and marketed, providing it worked , but not BOY RACER stuff, I think you could make some serious money, world wide patent. Quote Link to comment Share on other sites More sharing options...
Night Train Posted March 19, 2008 Share Posted March 19, 2008 I had access to a wind tunnel when I was at Middlesex University but I was doing experiments with fluid flow from about 10 years old (placing toy cars in the smooth flow of water from a hose pipe and assessing the turbulance by where air bubbles were trapped against the bodywork). I can make up a wind tunnel using a big perspex box with my work shop dust extractor attached at the outlet end and a stack of drinking straws at the inlet end to smooth the flow. A smouldering sash cord would provide the smoke. It would be difficult to guage the wind speed at that scale but a small anenometer might do it. It would also depend on the accuracy of my collection of Land Rover models. I was drawing trucks with air flow conditioners attached in 1974 when I was at school. Not sure when they finally appeared on real trucks but one of my teaches took my drawings home to show her husband who was a designer... I'm not accusing anyone but one does wonder sometimes. Quote Link to comment Share on other sites More sharing options...
Astro_Al Posted March 19, 2008 Share Posted March 19, 2008 Defenders do just about everything wrong aerodynamically. Thats part of the reason you'll never get good economy out of one. For a start you'll never lose the profile drag associated with its silhouette, let alone the carp hanging down underneath, all the useless angles, flat faces, nasty sharp edges and sticky out handles/gutters/bits and bobs, huge cutouts and interruptions in the bodywork - like wheel arches with lots of clearance, dreadful wheels and tyres, etc etc. They will, however, fit into the 'typical' aerodynamic profile of a generic 'car'. There are certain similarities between pretty much all cars. High pressure points (base of windscreen, front grille, just ahead of a rear spoiler etc), vortices etc etc. As well as flow separation above the windscreen on cars that aren't nice and smooth. This is nothing to do with the boundary layer, your forward flowing water is due to a large vortex over the roof just behind the windscreen where the air flows up the windscreen, 'keeps going' a bit further due to its inertia, then gets rolled down under itself, so that the flow over the roof directly over the drivers head is actually in the forward direction. More sophisticated cars manage to keep the flow attached over the windscreen/roof joint, a Land Rover almost certainly does not. I suppose you could add some vortex generators along the start of the roof and see if the problem persists. My bet is that they wouldn't be enough and you'd not see a difference. They might delay flow separation with increasing velocity though, you could probably test that. Hope it helps explain your observations. Al Quote Link to comment Share on other sites More sharing options...
Scotian Posted March 19, 2008 Share Posted March 19, 2008 Can we have an X-spoiler? Quote Link to comment Share on other sites More sharing options...
Mo Murphy Posted March 19, 2008 Share Posted March 19, 2008 Night train. I take it that from your post you have access to a wind tunnel, therefoer you presumably have access to the aerodynamics programs. Once you've done the test, then you can play with the air flow with theoretical spoilers, bonnet deflectors. I've not seen it done anywhwre foe a defender. If there was a simple solution, and was manufactured, and marketed, providing it worked , but not BOY RACER stuff, I think you could make some serious money, world wide patent. Spoilers are so 1980's, I think I'd be too embarassed even if It did save fuel ! Mo Quote Link to comment Share on other sites More sharing options...
Mo Murphy Posted March 19, 2008 Share Posted March 19, 2008 ... and it would just get ripped off by branches every time I go laning just like anything else I bolt to the outside of the 90. Mo Quote Link to comment Share on other sites More sharing options...
LR90 Posted March 19, 2008 Share Posted March 19, 2008 If anyones got a Fluent journal file to hand (or could build one) I have a handy cluster to run the simulation on. Quote Link to comment Share on other sites More sharing options...
Night Train Posted March 19, 2008 Share Posted March 19, 2008 If anyones got a Blah Blah file to hand (or could build one) I have a Blah Blah to run the simulation on. ??? When I last did fluid dynamics there was only one computer on the Uni campus and we had to buy time on it. We also had to write all the programmes ourselves in ForTran and hope that it worked. Most of the calculations were done by hand using simple calculators and log tables. Quote Link to comment Share on other sites More sharing options...
Eightpot Posted March 20, 2008 Share Posted March 20, 2008 I've had a bullet shaped see through plastic inflatable made, it covers the whole front of my 90 from grill to the top of the screen, and when fully inflated gives me a tear drop shaped front end. I can do 165mph now, and it's reallyhelped with river cossings as well. Quote Link to comment Share on other sites More sharing options...
freeagent Posted March 20, 2008 Share Posted March 20, 2008 it amazes me that even with your inflatable plastic bullet that you can get 165mph out of it... considering your flappy canvas frame tent roof, bald G90 tyres and two fat collie dogs weighing you down. Quote Link to comment Share on other sites More sharing options...
tacr2man Posted March 20, 2008 Share Posted March 20, 2008 Aerodynamically speaking , I know that landrover found that a series 3 with a bonnet mounted spare was faster than without. In OZ a lot of the roof racks come with a solid contoured front end , lot of roof racks out there. Driving when snowing gives a prettygood demo of landrover aerodynamics(lack of) Quote Link to comment Share on other sites More sharing options...
Sharp Pointy Thing Posted March 20, 2008 Share Posted March 20, 2008 And another thing........Not only are the aerodynamics non-existent they've also got a carp radar cross section. I can get within 50yards of our local 'slow down' sign in a Focus (strictly at legal speeds of course ) without it picking me up. In my 110 it gets me from miles away. Which is ironic 'cos it's got such carp aerodynamics it takes a ten mile run-up to get anywhere near the speed limit. With a back wind. Downhill.................... My friend once set one of those off WALKING past with his guitar on his back and I've driven past the same one in my Golf and it hasn't gone off at all more than once! Quote Link to comment Share on other sites More sharing options...
GBMUD Posted March 20, 2008 Share Posted March 20, 2008 I was once told that a Defender was more aerodynamic in reverse than forwards. Chris Quote Link to comment Share on other sites More sharing options...
landroversforever Posted March 20, 2008 Share Posted March 20, 2008 would it not be more aerodynamic if you opened the bulkhead vents and took off the back door? Or pipe it in and make a wind tunnel to test a modle landy!! Quote Link to comment Share on other sites More sharing options...
Astro_Al Posted March 20, 2008 Share Posted March 20, 2008 would it not be more aerodynamic if you opened the bulkhead vents and took off the back door? Probably not, oddly. Al. Quote Link to comment Share on other sites More sharing options...
Yostumpy Posted March 20, 2008 Author Share Posted March 20, 2008 Probably not, oddly.Al. Actually i have seen a thread where a guy got amazing economy by opening vents and rear windows in a 90 sw, releaves pressure at bottom of screen. So witha spare on the bonnet, being rounded and smooth, this would brak up the air flow and divert it sideways. Any one else heard of the s3 being faster with wheel on bonnet! In OZ a lot of the roof racks are only 3/4 long, and stop before the roof slopes down to the windscreen. I do remember when I put a steering guard on my old one, it knocked abouy 2 mpg off. All I am trying to do is build up a theoretical model of 'best case' with each thing worth a %, ie 3/4 flat roof rack, wheel on bonnet, windows closed, vents open! Problem is NO 2 journeys are EVER the same, hence wind tunnel static testing! Quote Link to comment Share on other sites More sharing options...
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