windshield
So i am looking into the windshield angle mod listed in the efficiency mods section, and i was wondering what windshield would be the best replacement for a mazda miata to maintain best visibility with the new windshield angle?
if i just kept it stock, i expect i would be seeing 20% less of the road. |
Modifying the windshield for what? You will see very little gain in efficiency by changing it, and it sounds like a galactic pain in the butt if you want it to look and work good. Your efforts would be better spent elsewhere on the car.
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unless your building a showcar/hotrod.....why would you start at the windshield?
I would look at a body kit to get a lower profile withuot scraficing the ride quality by lowering the suspension. |
total conversion
its a total conversion project
im harvesting the mazda miata drivetrain/suspesion and building a sandrail style chassis, attaching a body to it. So the amount of work is astronomical and wouldnt be reduced by keeping the old windshield. But i want it to be more aerodynamic, so i need a windshield which is the approximate width of the stock miata but a little bit taller so that the angle can be changed with no ill effects on visibility. |
I think a lot of people are going to start posting images of that green teardrop template if you don't clarify that you are doing this so that it "looks" faster and more aerodynamic.
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reasons
it doesnt have to look anything
it needs to be more aerodynamic the stock miata is something like .37 coef of drag frontal area should be pretty much stock miata though since the width/height are being determined by a lot of the harvested parts, but the aerodynamics can hopefully be improved to be a .25 or so coef of drag. So to do that i basically need to follow almost all of the aeromods listed on this website, which includes changing the angle the windshield meets the hood at to be less severe of a change. to do that i think i will need a taller windshield. I was thinking of switching to the toyota prius windshield, which is slightly wider as well so the wheels would end up being slightly recessed which would be ok since then i can cover them with panels without there being a bump. but im open to other options. |
windshield
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My neighbor ditched his Miata ,got a CRX and picked up 12 mpg without lifting a finger. |
People still think the hood/windshield junction is the problem :rolleyes:
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Have a look here, for some basics on the ideal shape to strive for.
http://ecomodder.com/forum/showthrea...rt-c-9287.html Yes you'll want to optimize your windshield - but I would think you would want to optimize the entire 3 dimensional shape of the vehicle. |
But isn't most of the drag from the rear of the vehicle and from the underside, the amount of drag from the shape of the front is such a small percentage it's hardly even worth worrying about if you are ignoring the rest.
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not
the rest will not be ignored
the only things im basically stuck with are a 66 inch width, and a wheelbase of 89 inches because of the drivetrain. So that means yes, there will be rear mods, underside mods, tire mods etc. Think i found a better fit for the windshield now, the honda insight is 66.7 inches wide so i wouldnt be gaining as many inches for the windshield mod. for the creation of the boat tail as linked in that picture, i find it difficult to read. are the numbers the change in degree or are they coordinates on a x/y grid? Basically, for every 1 foot towards the back of the car how many inches towards the ground should it advance? |
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Get your objectives straight in your mind. Do you want to work the usual ecomodding approach to improved fuel economy, or do you want a custom street rod? Making basic changes such as windshield angle are very difficult technically, and the associated adaptations, such top, seats, doors, side glass, etc. just ripple on forever. If you are determined to proceed with the Miata, I'd buy a good front spoiler such a the one by flyingmiata.com, built a complete smooth belly pan, remove the right side mirror, possibly add rear tire spats. Then I'd look at constructing a template derived extension of the hardtop rear, with new rear window. Can such a thing pass road safety inspection in your state????? |
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Muffildy, if you're gonna go all-out, use the rear hatch glass from a 1984 Camaro:
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all out
yes, this is an all out project
none of the unibody will be re-used, we are going to be bending/welding a completely new body and attaching it to a tube frame chassis. the 1984 camero rear window is a good idea, only problem is that the camero is 72 inches wide, which is 6 inches more wide than the miata; since we are using the A-arms/differential etc that would mean i would need to get longer CV joints which can be pricey; do you know of a similar rear window thats made for a 66 inch wide car? If i used the insight front windshield i would be at 66.7 wide instead so between 66 and 67 would be good. 68 might be pushing the CV joint issue. also a 3000 dollar windshield is out of the question - budget is not that big. |
Check out using an Insight hatch. It should be about the right width. Any Insight parts you can hang on your tube frame will put you ahead of the game weight wise. If you could use the entire roof and A pillar assembly you would get the windshield and the nice shallow angle that it has. Just one of many options I'm sure.
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Put an Insight body on your sandrail chasis?
Or get a junked Insight and give it the power train you want it to have. You'll start with really good aero and a lightweight shell. |
food for thought
hrm, may do just that; i was going to go more for a full boat tail but i cant seem to find glass for that option.
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http://media.ed.edmunds-media.com/pi...ght.5074-E.jpg |
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Another option might be a Corvette hatch glass. But I imagine it would cost more than a Camaro hatch. |
Nissan Murano rear glass looks good, though the glass is not laminated windshield glass = not legal for use as one. Has a wiper already built in though.
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It'll help the streamlining beyond the windshield-roof transition. |
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Previa Thread http://joshp77.files.wordpress.com/2...agestima31.jpg |
Camaro
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They won't even let me,or anyone else run one of these at Bonneville.Glass shards all over the course should they break. And State Inspections won't pass them for passenger vehicles as they're not DOT rated for windshield service. RATS!!!!!!!!!!!!!!!! |
Dodge Viper?
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Less of a sharp edge the air has to break over. IF the template is the ideal, then the rounder and smoother we make the front of the car the better the rear will work, yes? If one took a vertical flat plate and the rear was the template from max camber, would "that" be just as good as the full template? If the windshield is of no matter, why do the better aero cars all have laid back windshields? Prius...
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Rumpler.
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If the flow is decent as far back as the A-pillars/windshield header it doesn't matter what's going on ahead of them. |
Rumpler, .28 so? It follows your template in plan view, if it was template in side view, it would be really something.
"If the flow is decent as far back as the A-pillars/windshield header it doesn't matter what's going on ahead of them." Prove it. Vertical flat plate with template rear = full template, I don't think so. |
Here's what Hucho (1987, pp. 133, 135, 136) has to say about windshield angle:
As the windshield becomes flatter, the aerodynamic drag decreases. ... From all these data it can be concluded that the direct influence of windshield inclination on drag is only moderate. The effect is assumed to be more pronounced the more the flow is routed over the windshield. Windshield inclination angles of more than 60 degrees are not practical because of light diffusion. In addition, large, highly inclined windshields lead to increased solar heating of the passenger compartment. Two effects are responsible for the favourable, though moderate, influence of a highly inclined windshield on drag. First, the excessive speed in the area of the A-pillar is reduced so that the momentum loss occurring at that point is smaller. Second, the deflection of the flow at the transition from the windshield to the roof is weaker. The low pressure peak occurring there is therefore smaller and the positive pressure gradient in the remaining flow is less steep. Hence the momentum loss in the boundary layer is lower, allowing greater pressure recovery in the area of the rear end. . . . Therefore, even if a strongly inclined windshield does not contribute to a local drag reduction, it helps to improve the flow over the rear part of the car and thus to reduce the overall drag. |
buick riviera
found the buick riviera has a really nice looking rear glass
problem is i cant seem to find any information on the dimensions of it so i dont know if it will even fit. also, cant find anyplace that sells it in particular except ebay. |
Recommend cleaning up the trailing flow...and it'll look way cooler!
http://pic90.picturetrail.com/VOL237.../387846677.jpg http://www.paul-davis.com/vehicles/miata/fasback.jpg http://lh5.ggpht.com/_e9GW4M7g5Rk/Sv...miatalhMOD.JPG http://www.autokonexion.com/images/f...epic%20589.jpg |
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Instead of an angle change, modders easily chops the glass and lowers overall frontal area.
Even at SEMA 2011, they chopped the windshield for a Spyder concept. http://www.autoevolution.com/images/...y-medium_4.jpg |
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The Previa ruins it through sheer size and its rear though. On the Prius and Insight, Mercedes A and B, ... the angle between hood and windshield is also minimal. |
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First: http://www.vonemdeheim.com/picture_library/P1270034.jpg Third (latest): http://priuschat.com/forums/attachme..._prius-prv.jpg james |
Rumpler
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Riviera
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Rumpler Tropfen-Auto
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A plan-view of the car appears in Baron Fachsenfeld's book of 1951. The body is relying on a 2-D type of flow with the air going primarily around the body rather than over. The body itself is a 3.044:1 streamline section with 100% aft-body. *At maximum body camber point the tangent angle is of course zero. *At 10% aft-body length the tangent angle is 4.5-degrees. *At 20% aft-body 8.5-degrees. *At 30% aft-body 14-degrees. *And from there on to the terminus the tail maintains a 14-degree angle. -------------------------------------------------------------------------- The roof in plan-view is a 2.164:1 streamline section of 0.89-width forebody and 1.27-width aft-body. I've not put a protractor to the roof although the rear curvature is quite aggressive and just looking at the image I would presume the flow is separating by the rear axle centerline. Flow over the roof is very good.It has a familiar architecture. -------------------------------------------------------------------------- I believe that a 3.92:1 section has the lowest Cd in 2-D flow.And little is published about 'cars' based on sections.They are more like inverted boat hulls or wingtips than sections. -------------------------------------------------------------------------- At Cd 0.28 the car was remarkable for its day however when compared to Jaray's 'pumpkin seed' of 1921 @ Cd 0.13,we have a better path to follow. |
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http://static1.carsablanca.de/files/...jpg?1280329052 Not so good over the top, is it. But most air, as you said went around the side. Maybe that was much cleaner, given the shapes. james |
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