Over and Under or around the sides

[tok-tokkie]

Very interesting thread. What about wheels out but in spats to shield them from the airstream? Minimal frontal area. Rear wheels in turbulance from front if it is a 4-wheeler.

[greenpower dude reloaded]

Interesting thought, I had looked in to that for this season, making a carbon tub then wheels out and spatted, problem is it takes very careful designing from mostly an aerodynamics point of view but also a structural point of view. when I finally crack (how to use, not illegally downloading ) either fluent or Openfoam I'll be able to look in to this all a little more thoroughly.

The biggest problem at the moment is getting the car going again after it's incident at the Ford test track, that maybe progressing well but it wasn't built into our plan as such... that's racing i suppose!

[greenpower dude reloaded]

Just working out how to mould the new body, pics of which I intend to post later, to give you an idea it's quite similar to slimjims more developed version.

My biggest problem with moulding is getting a large chunk of something to shape so i was thinking (heres the simplified version) of making a ply tub thats roughly to shape, then filling it with PU foam "popping" it out and sanding to the right radii etc.

Problem is, to make the ply tub I need to cut out a compound curve from a flat sheet, I've got this shape in Pro/Desktop and Solidworks but don't know how I could take the lines from it as it were.

Any hints or tips would be greatly received

[greenpower dude reloaded]

As promised here are a few pics of the shape im proposing.

Side


3/4 rear


Plan



Solidworks kind of deformed the helmet fairing. I've got the drawing in .sldprt but can export to most formats if anyone would like a crack at running it in CFD or whatever just let me know.

RE: Moulding has anybody got anysuggestions as to how we do it cheapest and easiest?

[Ciro Pabón]

Wow. It looks beautiful. Perhaps in red or silver? Maybe yellow and white is OK.

This is an idea (a little weird, cut instead of mould):

Fabrication of partially double-curved surfaces out of flat sheet

This is along the same line of thought (cut and paste, instead of moulding):

How to make a parabolic reflector out of flat sheet

Let's hope some moulder extraordinaire comes along... [-o<

[greenpower dude reloaded]

Fascinating Ciro, they're really interesting snippets, I do wonder though If it doesn't matter how you go about trying to acheive the shape it will always take nigh on forever to get it ready.

Funny you joke about the colour, I am really stuck on what to paint it, I want to do a good job either way, easiest way may be to use pigment in the resin and add in detail afterwards if need be.

So i'm open to suggestions on colour so long as you can find it here http://www.ecfibreglasssupplies.co.uk/s ... 90d2613e8d

And please no red... Long story..

[Carlos]

You could use a steam box to make the plywood a compound curved panel, it's a boatbuilding technique; simple, inexpensive and very low tech.

http://www.amateurboatbuilding.com/arti ... nding.html
http://www.instructables.com/id/How-to- ... ding-wood/
http://www.woodworkingcanada.com/Bendin ... -will.html

With plastic panels you could try an inexpensive sheet plastic vacuum former.
http://www.instructables.com/id/Make-a- ... astic-vacu

A thought... could you put a half height fairing in front of the cockpit to complement the aft structure... but small enough so it doesn't obstruct the driver's sightlines?

[James_graham]

Could I ask what materials you are making your body out of? The moulding technique and materials may depend on this

[greenpower dude reloaded]

Thanks Carlos, they are excellent links, I quite fancy a crack at making a massive Vac former. Having said that a small one could really be a huge boon being able to make quick, cheap & light component/fairings.

I'm also thinking about making a boat if i ever get any "down time" so those other links are also great, might just be a bit too heavy for Formula 24.

The bit i'm struggling with at the moment is the taking the 3d image i've created and turning that in to a net as such. I want to make a wooden tub (no rounded edges but to the right profiles.) Maybe something can be done with a projector.. any other suggestions?

James,I was donated about 250m of Fibreglass CSM last year, it's not the lightest stuff or strongest but its pretty good

[James_graham]

Ah okay will you be using an epoxy with that? or acrylic? Could you make a male mould and do some wet lay up?

What do you mean for the profiles?

[greenpower dude reloaded]

We've got a load of polyester resin so we'll more than likely use that up.

My biggest difficulty is creating that male mould in the 1st place. What I was thinking of doing to create that a big square version first by making up a wooden tub and filling it with 2 part PU foam. once i'd extracted that I'd round the corners off.

Problem is I have a great shape that I know would fit, but it's replicating that shape that could prove to be a challenge because I have a collection of curves that would be a nightmare to replicate being as they themselves are rounded over another curve.

I was wondering whether maybe a projector could help with this, it may need some careful setup but it would take out any complicated maths....

[James_graham]

Yeah that may work try to get as close as you can to the shape you want in a tub and then work it down. I get what you mean using a projector.

You could make it out of some sort of foam to make a male mould? and do it in the same way an F1 team does a chassis pattern? may take alot of man time? I'll have a think about it but you are after a male mould?

[greenpower dude reloaded]

excellent thanks James, we did it in a similar fashion to F1 last year and it took an absolute age, It was worth it though, of what we actually got finished it looked great.

Yeah I think you're right, male plugs are much easier to work with in my experience.

[flynfrog]

I would do the foam and fiber glass method I posted earlier. you basically cut cross sections out of ply wood then weight your foam in place glue in bulkheads then glass both sides its light molds are cheap and its pretty easy to do.

They even construct home built planes out of similar methods

http://www.rqriley.com/frp-foam.htm
http://agelesswings.com/CONSTRUCTION.HTM

[James_graham]

That would be good but if it depends on what you are trying to acheive, if you want just a shell of the car which can be removed to work on components underneath you would be left with a sandwhich construction which would be hevier than a conventional released mould (and stronger than just using glass). As it mentions in the article to use a male mould and CSM would leave a bumpy uneven finsh to the part which would have to be worked on later to provide a smooth surface which I am guessing you are after for aerodymanic purposes?

Are you after just a shell to go over a chassis type construction?

Do you intend on having a sandwich construction? or just the glass fibre?

Sorry for the questions just getting as much info as possible!