Tuesday, January 04, 2011 - 09:20 pm, by: Ben Lipman(Ben12a)
I am currently constructing a new front splitter/air dam/undertray for the Soarer. I know there are fibreglass gurus out there who would love to share their knowledge and expertise with the Soarer community. Whilst it is too late to help me with this iteration of splitter, I am already thinking of ways to improve what I have.
Here are some areas of concern and issues I have come across in my long four days experience in the fibreglass construction field:
I purchased kits from bunnings that came with 1sq m chopped matt, 1kg resin, hardener, etc and I also purchased a little roller at the same time.
1. I believe this was a bad move as tonight I found I could have bought much more for lots less on ebay, and I reckon a local supplier would have been cheaper as well.
2. After using up the kits I discovered fibreglass woven cloth and bought a square metre of that and some more resin. This stuff was a godsend- so much easier to work with and has a 'cool' looking texture. I also found a lot less resin was needed than the chopped matt. I bought it at bunnings (slow learner- doh!) This is what caused me to want to build another splitter already, and this one is not finished.
3. I used 9mm plywood and then fibreglassed over it. This is over kill, especially with the chopped matt. Don't get me wrong it is strong as but getting a little heavy- there is 2kg of resin on the damn thing alone. I can stand in the centre and it deflects only a couple of mm. Now christmas was good to me and I way over 85 kegs at then moment. Reading time attack focussed forums a lot of guys just apply resin to the plywood. I would consider 6 or even 3mm ply next time and do a couple of layers of the woven cloth or even "woven roving" which I just read about on the net ( I need more research, hence this thread.)
4. I made the lot as a single piece. I think it would have been smarter to make it in two pieces as the undertray does not need to be immensely strong, just the splitter component.
5. An easy on easy off system for the lower half (ie splitter) would be smart as well- I read about a guy using aero catch bonnet pins. This would mean no compromises in design.
Wednesday, January 05, 2011 - 12:06 pm, by: Aiden Cheese(Chillpen)
Whenever i'm working with the stuff i tend to buy lots of i think its flower foam stuff? People use it to stick stuff in and you get it from 2 dollars shops. It comes in bricks i think they only cost about a dollar each brick..
I then shape that foam through cutting etc and stick it to the plywood base that i'll cover. Then i cover the whole thing in a waxed tape and then fiberglass over that.
I've only done small things though, but i think the basic idea might work for you too, big plywood base the size of the area you want to fiberglass and then stick some shaped blocks as you need to give you the contours and so on.
Of course I have no idea what if any contours if any you'd need.
Anyway goodluck. Sounds like fun
I like arts and crafts when it comes to car stuff.
Wednesday, January 05, 2011 - 12:44 pm, by: Aaron Mead(Aaron)
Ben, that compressed foam stuff that signmakers, graphics companys use to make 3D signage/logos.
Its not a hard board, it would break pretty easily, but if you are going to fibreglass it heavily its perfect. Similar to what inside of a surf board is made of.
You can buy at plastics outlets (i.e. Ramstar Plastics on bombing road winellie), comes in 2400x1200. I got a sheet of 9mm that had a corner broken for $100. Once fibreglassed over, its tuff as, and easily 'rebuildable' when worn.
Phil Gibson Goo Roo WA '91 UZZ30, '91 manual UZZ31 track bunky, '94 blk/blk UZZ31
Wednesday, January 05, 2011 - 05:02 pm, by: Phil Gibson(Sciflyer)
Your base material can be pretty damn thin and flexible because once you fibreglass it properly it will be strong as.
That flower foam stuff Aiden mentioned, or balsa wood, or even cardboard will work. As i mentioned in my thread my old man does fibreglassing and is making me a bonnet, although obviously that requires making a mould first. One material ive seen him use for strengthening "ribs" is the thin wood framing strips you can get from Bunnings, etc, they are semi-circular in cross section, weigh practically nothing and flexible enough but when glassed they are strong as
Oh yes and find another supplier for the glassing materials, dad almost had a fit when he saw how much Bunnings charge for the stuff compared to what he gets it for heheh
Ben Lipman Goo Roo SA Soarer TT manual, plus TT track car
I have just finished reading the book Racecar Aerodynamics by Katz mentioned in this article.
It has readjusted some of my thinking wrt the low aspect ratio 3D aerodynamics that are the reality of a car. Everything they teach you about 2D aerodynamics at uni is just about useless due to the low aspect ratio, ground effect and body interactions that can largely be ignored when you are designing A380s. The benefits of all kinds of wickers, vortex generators, barge boards etc in certain applications was also enlightening.
As to tips for construction:
1- aim for high fibre fraction i.e. minimum resin but still fully wetting out. You can do this by setting up a vacuum bag and a temperature cure resin. All you need is the plastic, sealing tape, release layer and absorbtion mat (probably all available for the same price as your Bunnings kit). Use an eductor on your compressor to create the vacuum and make an oven on the garage floor with cardboard boxes and a domestic fan heater. I know a guy who built keels and rudders for America's cup yachts using these low cost techniques.
2. Stiffness does not come from using lots of material, but more from the distance between the top and bottom layers. The foam or honeycomb sandwich is how you achieve stiffness, think like an I-beam (RSJ), but the material and application can be expensive. 5mm of foam between 1mm layers of fibreglass is very stiff, make it 10mm and it is even stiffer. I have seen one sports sedan competitor's front splitter made with rolled up newspaper to get the required stiffness, and he was regularly winning races and championships. You could also use an inflated bag in the middle of two layers in a mould to get to the same end.
3. Suppliers - look at SPS systems, Fibreglass International, Fibreglass Material Services etc.
4. Why use plywood at all? If you are using it because you are scraping the splitter on the ground, then it will be too low to get enough air under the car to get downforce from your diffuser. There is a point below which it just increases drag and reduces downforce.
If you are using plywood to achieve stiffness, then see 2. above.
If it was me and I was using plywood at all, then I would only use it as a template or mould for the vacuum bag to get the flat bottom and outline. Throw a layer of wax and/or PVA release film on it and lay the bottom layer of glass + resin, then shaped foam, then glass + resin, bag, suck, bake. Then pull it off and attach to car.
Ben Lipman Goo Roo SA Soarer TT manual, plus TT track car
Tuesday, January 18, 2011 - 03:29 pm, by: Ben Lipman(Ben12a)
Plywood is a hangover from the very first iteration. It was plywood only. Andrew asked the same question: if you cover your plywood in 'glass, why use the plywood?
I never even considered it.
I want to build something again this year and am looking for ideas and insights, such as all the above.
I have read a bunch of stuff by and extracted from Mr McBeath and the racecar aerodynamics book keeps coming up as well. I am considering reading it, but was worried it might be too technical/conceptual for my small untrained mind. I don't understand a lot of the images and how to read the pressure 'maps' (?) in some of the articles I have read so far, and usually just absorb the conclusion/summary.
just so you know what I mean by vacuum bagging, here is a picture. You can get polyester, vinylester or epoxy resins and prepregs that can be used this way.
I used to work at FMS in Sydney during my uni days. Most of the time I was out in the warehouse picking, packing, loading etc. I even made up those little kits that were sold to the hardware chains. Filling 5ml bottles of MEKP by hand was not a lot of fun.
As I got to know more about the stuff, I worked once a month on the counter on Saturdays. This is when guys like you would come in to get their small amount of materials and advice. It was really interesting the number of weird and whacky things people were trying to do.
Mark Larkham's wife came in a few times to get resin and woven kevlar matting to repair the front splitter on his V8 stupidcar.
There was a couple of guys came in to get some paint for their boat. They wanted it to be midnight blue all over. We advise that this was probably not a wise choice for being out on the water at dawn or dusk because no one else would be able to see them, but they insisted.
By the way, woven rovings are far too coarse for your application. Stick with the woven mat or even a light chopped strand mat.
Anyway, point being that we were there to give the advice, so i reckon you should try some of the following for face to face chats.
Thursday, January 20, 2011 - 08:43 pm, by: Ben Lipman(Ben12a)
FGI has a store about half an hour down the road (Greenfields), but Adelaide has some weird trading hour restrictions meaning that it wasn't open on any of the days over christmas/new years when I was getting stuck into the splitter. I was using their site to learn enough to know what I was asking for.
One day down the track I'll go in and get them to set me up with what I need for a couple of small projects.