Thread: Prius 75-91mpg
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Old 10-26-2022, 03:22 AM   #320 (permalink)
Nathan jones
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Hi

The frontal area is the same, from an above angle it may appear more as the bumper angle is different, on a regular prius from the grill down air is directed down, on this all is pushed upwards or to the side.

Dimples create turbulence which strangely enough restricts the size of the boundary layer of air and also when it departs from the body in low pressure areas, so my wings or bonnet for example the air will be controlled and kept closer just after curves and angle changes or near the windscreen. So even though turbulence is created there is less overall area of the vehicle as a whole. Like a bubble is created around the car which is smaller than the bubble of a car without dimples. Personally I should have really started at the back of the car where most negative pressure is. I have started my 4th rear bumper and as of yesterday redesigned it again. The mean reductions are so low as stated because the shape of the car is not so square to start with. The main reason I change it is because if I am making new parts to reduce weight I may as well add a few shapes at the same time. To me and my experience mass has a bigger effect.

I cannot and don't bother measuring it's effectiveness as so many things change. The time I leave and where I go changes, also temperatures and trip lenths. These affect mpg far more than an approximate 1% of a dimple bonnet. But physics laws says it must work so I throw it in with a bunch of other stuff. Between 60 and 90mpg I would say, 60 being a frosy morning and 90 35c. But as I said, subjective numbers, I do not measure it. Just keep working. My definite two week record of 102 was without rear doors, plus having small wheels and a heatwave.

Thanks. As far as fiber products go I am more leaning back to polyester and csm glass. If well structured it can be as light and with much greater flex modulus. Also with the high styrene resin it rebonds to old resin but epoxy doesn't. I will still use epoxy as a surface layer when molding a painted part so the paint does not get wrecked. I found that however I try to hand lay woven glass, carbon or kevlar on the tight part of weaves it does not infuse. Even rollering sections for half an hour, sawing them up reveals dry weave centres, especially above 200g. I will keep my kevlar, unpick it and make a kind of biaxial cloth for the drivers door

Best thing is to buy stuff and try it. From my own experience stick to csm and hand lay. I have a vacuum thing but it takes longer is more expensive and is more likely to go wrong (but could be my impatience). See what works for you, you may be tidier with air leaks and have more and patience...

Also with polyester I can add less catalyst, have a great pot life and then leave it in the sun which you can't do with epoxy.

Incidentally if you are sure about using epoxy, german 'di-poxy' laminating epoxy is available on amazon for 11 a litre. Along with a few other tricks you can create cf for less than 10 a metre. Takes the punch out of mistakes


Quote:
Originally Posted by Andyinchville1 View Post
HI,

I like the dimpling idea and the lower air dam but it looks like alot more frontal area (maybe it's just the sheer volume of white).

Has the front end mods and dimpling helped alot (I saw the drag reduction percentages but what does that equate to in terms of MPG improvements. Also how did you figure drag reduction ?).

Thanks

Andrew

PS - Great thread .... come to the USA and I'll put you up to make my jetta in carbon fiber!
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