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Okay, I've read many, many complaints about this issue, and I think I have an idea that could help. No, I don't mean wind deflectors on the sides of the windshield, sidescreens, or any of the other similar ideas that have made some (or no) improvements.

My thinking is this (and I invite the input of aeronautical engineers, brain scientists and assorted rocket surgeons to help out here...) - the air coming up to the windshield is forced almost to a relative stop (relative to the car, that is...), creating a very high pressure zone. The air directly behind the windshield is a relative vacuum (or, at least, a very low-pressure zone). As we all know, nature abhors a vacuum, and so the high-pressure air in front of the windshield is in an awful, burning, headlong hurry to rush around the sides of the windshield to fill in the relative vacuum behind. Result - air pounding the sides of your head, as it's in the way of this high velocity vacuum-filling.

Now, then - suppose we came up with a way to allow the high-pressure air in front of the windshield to meet the low-pressure air behind the windshield, and have the two travel up & over the top of the windshield in harmony (at more-or-less the same speed). I believe the term, in science-speak, is "laminar flow". My feeling is that simply raising the bottom of the windshield off the scuttle wouldn't work - you'd get air shooting under the windscreen, and still have a pile-up of high pressure air in front (and still the relative vacuum behind), as nothing is inducing the air to travel in a laminar flow up & over the screen.

I'm thinking of something like ducts at the base of the front of the windshield, ducted through the scuttle (under the windshield) to blow upward on the inside of the windshield (like defroster ducts, sort of), to create a high-speed flow of air UP the back of the windshield. If this works, the air coming past the sides of the windshield will simply be passing by, without charging in at the side of your head.

By way of illustration, I got a Cee Bailey windshield for my 1000 cc Kawasaki Concours. The original one produced monstrous buffeting, even when wearing a helmet. The new windscreen has a small NACA duct near the base, and ducts air in to the back of the windscreen. Prodigious amounts of high-velocity air come through the duct, up the inside of the windshield, and carry the entire flow up & over my head in an apparent "laminar flow", leaving a fairly large area of relative calm behind the windscreen, around my head. Of course, in a Locost, there would have to be several ducts, but it should work. And it needn't add any weight.

Any thoughts??

So windshield defroster vents?

I'm surprised, but theirs nothing like a working example. Can you get a picture, just to get an idea of the relative sizes?

Here's a small pic of the Concours windscreen with the NACA duct, to give an idea of the relative size of the duct....although the windscreen is roughly 5 sq. ft. in area, the duct is only about 4" across, and 1/2" or so deep. It would be even more effective if there were more of 'em...

Yeah, but with the supply air coming from the base of the front of the windshield (no boosting or blowers required). Of course, I guess it would be possible to use a really, really powerful defrost blower to fill in the partial vacuum instead of bypass vents, but it would be hard to get it to match the airspeeds required at varying road speeds.

I guess the effect I'm searching for is kind of like holding the flat of your hand out a car window at highway speeds - lots of buffeting. As you turn your hand on edge to the wind, resistance goes down, and buffeting goes down. Kind of like lowering the Cd of the windshield? Any physics/aeronautics gurus out there?

I have a silverwing, but this photo is not of mine. Note the duct. The flow helps to keep the screen defogged and decreases the pressure on the front of the screen, which has no side or upper supports. Rain also comes through the port.

At highway speed, the air can't fill the low pressure within a couple feet of the windscreen. The air comes from behind the seats. Many convertible mfgs offer a window between the headrests that prevents the air from flowing forward. Experiment with a piece of cardboard duct taped up there first. Keep cutting it down then driving to see how big it needs to be for the speed you wish to go, then make one out of plexiglass or framed safetyglass.

Where does the water go if it's raining?

I haven't figured that part out yet, although most cars take fresh air from in front of the windshield, and send the water...somewhere. Maybe a drain in the bottom of the ducting to a drain tube? I suppose it couldn't be any worse than the rain doing mach 1 from the side into your ear

In years gone by, (back in, say, the 1940's), most cars had a pop-up vent at the base of the front of the windshield, for forcing air into the car (kind of a Cro-Magnon air conditioning). However they did it, water didn't seem to come into the car when it rained...

The air at the base of the windshield goes thru a convoluted pathway to get inside which lets the water go the lowest spot and drain out.

Those Cro-magnon drains did let in the water. You closed them or almost closed them to try to keep it out.

For this to work you need an almost unimpeded pathway so that you can move enough air to fill the void.

My old 65 Cuda had some straight thru air boxes at the driver and passenger's feet. There was a door that opened or close (manually of course) and they flowed a LOT of air. Much more than anything I've seen in many a year.

Maybe something like that could be a good supplement or even replacement for the window vents. Then it has the added benefit of keeping the cockpit comfy-er.

Yup, that's the kind of thing I'm talking about. Come on, guys, let's have some more ideas!!

Zombie thread rises to roam the boards again! Rarrr!!!

Did you ever come up with anything, or are you at that point in your build yet?

One question that would need to be asked is how often you anticipate being caught in the rain in your Locost. Being in BC, that may be a silly question. I do like the way you're thinking, just to prevent buffeting.

There are two sources of water you'd need to deal with here. One would be water entrained in the air, the other would be water on the body that is being blown back towards the windshield. For the latter, you'll need to have some sort of rain gutter to allow the water to drain from. As for entrained water, the only way I could see dealing with that without undue flow restrictions would be to direct the air through a chamber with curved baffles made out of some sort of wicking material (pretty much any hydrophilic cloth). The curve would be sufficient to force the water out of the entrained air by centripetal force, and then the baffle would allow the water to wick down to a drain.

Hmmm... how about 2 NACA ducts about a foot in front of the windscreen, and from there you make curved ducts out of stretched fabric? (I was just reading the thread about the fabric-bodied BMW concept car, and still like the idea of a stretched fabric hood.) You'd need to duct the duct once you're into the scuttle to keep your dash electronics dry, of course...

If you ever get around to trying something like this, please let me know!

and dislikes a vacuum cleaner....





Ok you caught me .... some have reported a high under hood air pressure ..... What would happen if you vent from under the hood to the inside of the windshield.... providing defrost....and providing some similar benefits.

I have experimented with reducing wind buffeting on my Locost for several years now. The high vacuum “ low-pressure area” behind the front windshield is worst then if you are on a bike at the same relative road speed. I have tried several approaches to reduce the buffeting. Some worked others did not, I have no way of measuring buffeting but these are my general findings.
Winglets will reduce buffeting around 10 to 15% depending on size. The attachment should allow some air to pass between the screen and the winglet.
Laying back the front windshield an addition 5* reduce buffeting by about 10%. It helped mostly at lower speeds and no change at higher speeds.
Wind screen behind the seats, Attached across the full width of the roll bar and at head height. I also experimented with cutting down the screen with gaps on the top, gap at the bottom, and both top and bottom gaps to allow some air to fill the low-pressure air behind the windshield. I used Plexi-glass and it did not help, It actually made it worst. May be a wire or cloth wind screen may work better.
Bikini top, you still have high vacuum area, but a high percentage of the air flow is behind your head. It reduced buffeting in the 30 to 40% range.
Side doors, without the top. My doors are a lot longer then most. They run from the front of the windshield all the way to the roll bar. They reduce buffeting a good 40 to 50%.
I have a defroster, and a 5 speed heater fan, but I can not feel any difference in buffeting with the system running. I would venture to say that it would take a lot more volume the a typical heater could put out.

This is a sample of one, Your results may vary. Dave W

On my Rhino, I raised the windshield about an inch off the Dash/scuttle. It helped a lot with the buffeting but I still get dust sucked in from the very back of the rhino.

A solution might be a spoiler right behind you read that draws air from way above the burbling air from the windshield. My 32 Ford sedan has a windshield that tlits out at the bottom and it really vents the interior quickly. But I never go above the 32's terminal velocity of 38 mph though.

Tom

Can anyone comment on those tiny brooklands? screens? They are so small that should make a big difference - but maybe basically removing the windshield is not really on subject....