Jersey Tom wrote:Izzy410 wrote:maybe i'll move the wheelbase forward. but that will mess the CG now wouldnt it ?
Why does the CG matter on this project?
I finally got hold of STAR-CCM+
im running simulation in it because its abit more accurate on the data than the Pheonics VWT is
More accurate? Says who? You could have the most expensive, fancy CFD software in the world... it means nothing when put in perspective of the end user. You can make pretty, colorful plots, but how do you know they aren't complete crap? How do you know what boundary conditions to set? How refined is your mesh, and how is that impacting your result? How are you taking into account the gas flow from the CO2 canister and its effect on things?
Don't mean to come across as harsh... but it sucks that competitions like this encourage blind "engineering" work - aka playing with engineering tools without knowing what's going on and assuming the answer is OK.
Comment taken well and positive. I do understand your statement of encourage blind engineerig work but our team works with a University that helps us in making the design. of course we ask them and i do now boundary setting that although not accurate but are good enough.
When i meant MORE accurate there is a reason, the older CFD program pheonics can only max out at 100 thousand mesh because of academic license but with the newer one i can set up to whatever my computer can handle. of course it helps that the university we work with also uses STAR CCM+ so their experience and knowledge put us on the literate side. I do my homework but of course i still am in the blind side.
But your comment is well taken. I do understand your concern
About the CG it does matter. if i move the wheelbase forward the CG will be (in relative) moved back thus more tendency to wheelie. which is very bad for the objective.
pudin wrote:Check your front wing,it looks like its not 3mm from the track surface.
The rules stated the car parts must 3mm from the track surface.
And,about the mass,you dont have to worry about it,the finishing part does it all for you,you just have to find a really pro airbrusher that always calculate your car's mass after he sprayed a little.From the looks of your car,i think it only weight about below 30 grams after manufactured,because i've done 50 cars just like yours.
So,fairing the wheels with the sidepods is a good idea.Take a good look on basilisk world final car and also team Aixtreme Racing.From the front to the back,their sides are straight without any shape
Thanks for the comment. The front wing if you read properly from the rule book can be below 3mm. we did that in national and we passed the regulation check. the part that has to be 3mm from the track surface is the part IN BETWEEN the front and rear axle as quoted here
2b. Body to track distance
Min: 3mm / Max: 15mm
(Excluding tether line guides and aerofoils, but
including side pods and the tether line slot.
Measured from the track surface to the
underside of the car body between the axles
and side pod extremities.
I.e. Within the underside
area bounded by the
axles and side pod extremities, no point can be
lower than 3mm from track surface or higher
than 15mm from track surface)
As for the weight issue take a look at basilisk thread. they talked about an increment of 1 gram is equal to approx. 0.05 second on the track. that is alot. so keeping the mass down is crucial. as for the finish we do have a good airbrush service. the last time we did our national the clear coat was thinner to reduce weight. since the car was heavy. this car would be only 18 grammes when cut. but we are trying to get less dense wood. If you check the mass before cutting some block weigh as high as 140 grammes while another weigh only 88 grammes. so we can take the lowest density balsa.
The fairing is understood. we just run a test. it shows a lower Cd. but im rerunning it at a higher iteration to find out for real.
Thank you for the comment. now only if STAR CCM would kindly not use up all the PCs memory -.-
