Davidljones88
Well-Known Member
Has anyone thought about or used a Pitot tube to test to add strakes under the car?
Aerodynamics
- Thread starter Davidljones88
- Start date
Desert Sasqwatch
Goblin Guru
Not sure what your trying to ask? Using pitot tube(s) to test? Air flow? Vacuum?
Keep in mind almost every racing sanctioning body doesn't allow for underbody skirts/strakes - except for an allowance of a rear diffuser with a maximum width and length that can incorporate strikes. Many builders who could benefit from full length aero are unable to use them.
But to answer your question, yes, I remember reading at least a few builders have looked at and some have incorporated skirts/strakes. Yes, they do help with underbody aerodynamics, when incorporated correctly.
Keep in mind almost every racing sanctioning body doesn't allow for underbody skirts/strakes - except for an allowance of a rear diffuser with a maximum width and length that can incorporate strikes. Many builders who could benefit from full length aero are unable to use them.
But to answer your question, yes, I remember reading at least a few builders have looked at and some have incorporated skirts/strakes. Yes, they do help with underbody aerodynamics, when incorporated correctly.
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KingChuck24
Well-Known Member
Is the drag coefficient known of the goblin?
KingChuck24
Well-Known Member
Does taking off the windscreen help or hurt the aerodynamics?
Desert Sasqwatch
Goblin Guru
Aerodynamics was probably not the proper term to apply, it should have referenced downforce. Don't disagree that adding aerodynamic aides to the Goblin is a marginal proposition, but Justin Reed and others have found them to be of benefit - so they do work on a tube framed open wheel car.
But even with the top side aerodynamics of a golf cart, having a flat bottom and adding skirts/strakes under the floor pan - among other aero tricks - can create a low pressure area under the Goblin, which is the topic of this discussion. But I think we can all agree that anything applied that can help with downforce (and aerodynamics) is of benefit to the Goblin.
But even with the top side aerodynamics of a golf cart, having a flat bottom and adding skirts/strakes under the floor pan - among other aero tricks - can create a low pressure area under the Goblin, which is the topic of this discussion. But I think we can all agree that anything applied that can help with downforce (and aerodynamics) is of benefit to the Goblin.
TravMac
Well-Known Member
I'm waiting for the day someone pays 9 lives to run CFD on their ride and we can get some good value of these discussions. It's always split - half who believe we have the aerodynamics of a cow (which is arguably better than a wrangler as seen below), and half who hope our efforts mean something with a bit of seat of the pants feel and maybe some laptime numbers. Anyone want to volunteer to get a vehicle scan?
(and yes, this is only a contour plot, it doesn't actually prove much of anything, but it's funny)
(and yes, this is only a contour plot, it doesn't actually prove much of anything, but it's funny)
Desert Sasqwatch
Goblin Guru
If you want to get scientific and do some guesstimating, the following Cd examples can generalize what to expect if a Goblin were to be dropped into a wind tunnel:
From a practical standpoint, my guess is a Goblin is generally akin to a long cylinder (0.82) but does have a somewhat cone shape (0.50) with the hood and side panels installed - depending upon your point of view. Not great by any stretch of the imagination.
But frontal area (area that is >45 degrees perpendicular to airflow) also plays into the equation as Cd - as this factor multipied by frontal area equals total drag. Essentially, 2 exposed tires (12.5X9 inches - 1/2 of the height), a windshield (40X12 inches) and a radiator opening (13X16 inches) makes up the bulk of the frontal area, plus some frame tube structure - or about 6ish square feet (this excludes wings, spoilers, etc).
If the guesstimate for Cd is between the cylinder (0.82) and the cone (0.50), say 0.66 (which correlates to a Lotus 7 listed as 0.65 Cd), the Goblin should have a total drag of about 39 ft2 calculated. Yes, it's a brick, but adding downforce to that brick, that minimzes any added drag, is what can help on the track.
The best way to achieve that is to have a front splitter, flat bottom from front to rear, side splitters/strakes/skirts, and a rear diffuser - all of which contribute to the most efficient means of creating downforce and don't contribute significantly to aerodynamic drag (no frontal area is added and can slightly improve the Cd). Which was the original premise of this discussion. Look at it this way, there must be a bottom on the Goblin, why not make the most of it and modify it to achieve maximum downforce.
From a practical standpoint, my guess is a Goblin is generally akin to a long cylinder (0.82) but does have a somewhat cone shape (0.50) with the hood and side panels installed - depending upon your point of view. Not great by any stretch of the imagination.
But frontal area (area that is >45 degrees perpendicular to airflow) also plays into the equation as Cd - as this factor multipied by frontal area equals total drag. Essentially, 2 exposed tires (12.5X9 inches - 1/2 of the height), a windshield (40X12 inches) and a radiator opening (13X16 inches) makes up the bulk of the frontal area, plus some frame tube structure - or about 6ish square feet (this excludes wings, spoilers, etc).
If the guesstimate for Cd is between the cylinder (0.82) and the cone (0.50), say 0.66 (which correlates to a Lotus 7 listed as 0.65 Cd), the Goblin should have a total drag of about 39 ft2 calculated. Yes, it's a brick, but adding downforce to that brick, that minimzes any added drag, is what can help on the track.
The best way to achieve that is to have a front splitter, flat bottom from front to rear, side splitters/strakes/skirts, and a rear diffuser - all of which contribute to the most efficient means of creating downforce and don't contribute significantly to aerodynamic drag (no frontal area is added and can slightly improve the Cd). Which was the original premise of this discussion. Look at it this way, there must be a bottom on the Goblin, why not make the most of it and modify it to achieve maximum downforce.
KingChuck24
Well-Known Member
That's some good estimation Desert Sasquatch! In regards to running the goblin through CFD I am taking an engineering course which allows us to really make anything we want. I have thought about for a while either getting a 3d scan of the goblin or mocking it up in CAD and running it through CFD which we have access to at my school. Not really sure how pricey it would be to get it scanned but it would be really nice for the community to be able to have a 3d model goblin that can be worked on for aero pieces and such. Just an idea though but I know for my final project for that class it will likely be a front splitter for the goblin. The ones I have seen I liked but I would like to take a crack at doing one myself, maybe if I have time I will do some underbody things or side skirts.
Davidljones88
Well-Known Member
We should all pitch in or start a gofundme.I'm waiting for the day someone pays 9 lives to run CFD on their ride and we can get some good value of these discussions. It's always split - half who believe we have the aerodynamics of a cow (which is arguably better than a wrangler as seen below), and half who hope our efforts mean something with a bit of seat of the pants feel and maybe some laptime numbers. Anyone want to volunteer to get a vehicle scan?
View attachment 35991
(and yes, this is only a contour plot, it doesn't actually prove much of anything, but it's funny)
KingChuck24
Well-Known Member
Does anyone know how much it would cost?
Edit: I'm stupid the link says 2,250, that's extremely expensive...
Edit: I'm stupid the link says 2,250, that's extremely expensive...
comegetjoe
Goblin Guru
Split across a handful a members, it might be worth it.
KingChuck24
Well-Known Member
Would it not be more worth it if we all just started mocking up parts in CAD? If we were all able to make a couple components we could get most of the front end of the car pretty fast I would assume. The whole car might be more difficult but I don't know. 22 members would need to give a little more than 100 dollars, that might be difficult but maybe it would be possible and maybe DF themselves would chip in?
KingChuck24
Well-Known Member
Davidljones88
Well-Known Member
I'd definitely commit to some a bit of cash to get some data tested designs/aero improvements. I don't like the idea of just throwing a universal wing on the front. Strakes and diffusers would be nice.
I wonder if the rear engine cover helps
I wonder if the rear engine cover helps
Ross
Goblin Guru
I'll ask tomorrow.