COM Sports Car Club

Not sure it's the right place, but...

After breaking my last front splitter I'd like to get the new one to be fiberglassed for strenght. The splitter is 60" wide by 18" long, made of 1/4" birch plywood. I'd like to have someone fiberglass and vacuum bag it to add stiffness. Is there anyone who can do it reasonably? Thinking of boat repair shop, but maybe someone here?

Failing that, wet fiberglassing can be done instead of vacuum. I have the resin and hardener, will get the cloth, just need someone with experience to hold my hand and help out... or just take over and do it The closer to Boston, the better.

I would suggest using 1/2" marine plywood with just a coating of polyester resin and paint. The one on my GT3 Miata has survived some serious abuse on curbing and is still in great shape. The Poly resin helps it slide nicely on pavement. Also a router to the leading edge to round it helps remove any edge that would grab berms. Mine is only held on by 8 10-32 bolts and has survived several off track agricultural experiences.

I do a crap load of composite work .
ply wood is a bad idea ! I will not get into all the reasons as to why .
I have made countless numbers of splitter Gordon's MX-5 being one of them .
I also have repaired it a few times after some crash damage .
when it comes to aero most all flat pieces of some thing sticking out from the front of your bumper just doesn't work !
a proper splitter has to be designed in a aerodynamics simulation program .
to fat from ply wood and all it does is crate drag . most all people think the drag from the home made splitter is giving down force and think they made some thing that works great . NO drag is not great !

if you want a proper splitter it takes time to design one that truly works . giving the least amount of drag to the most amount of down force .
then the core material is also important . you want it light but strong ! the myth of having to be able to step in it and hole your weight is total BS ! a splitter will never see force loads like that and I mean never !
things like stays to support a splitter do more harm then good .
air has to flow around the stays and this takes away most of any usefulness the splitter is designed for .
one 1/4" round stay / support will disrupt the air flow for more then 4" on each side of that support .

Gordons 1st splitter scaled in at 6LBS in a finished form .
I use what is called a low wet lay up resin is what adds most of the weight .

so if you want dirt cheap you will get some totally useless the others in your class will love you for it as it will not do a dam thing but just you added points .

what you need is some one like my self with a aerodynamics degree to design a proper splitter .
if it's some thing that can be marketed this could cut down some of the cost as they can be made and sold as what was done with the ones I have done for the BMW's . porsches ,NC MX-5 and others .

My ideas are not mine on splitter material. They are gleaned from IMSA teams that I have talked to. I thought it odd that they had such thick splitters. So I asked why they built them that way. I was told it was more important to have a splitter that survived an impact than to have that last 10 % of efficency. And weight is not always as important as durability. In order to win, you first must finish. Watch any Pro race and you will see when they have an off, the splitter is one of the surviving parts of the front of the car. Get both a life, and a clue. And stop trying to sell smoke.

That might be true for a track car, but we are talking about autocross here.

I'm the chief engineer for a IMSA two car Porsche GT3 team . I also build aero devices for 2 other teams in IMSA with a 3rd starting for next season building FIA legal wings for them .
I don't know who or why some one would tell you that but wood core material is not used by any one I know of in IMSA . I know of one team using a press board as part of the flat bottom but it's not being used as a core material .
ply wood does not takes resin well at all so when it does take a hit it will tend to delaminate the composite off the plywood . one reason why boats use balsa core is un like plywood it soaks up resins .
I will use plywood for building plugs to make the molds but not for the product that is intended for being installed on the car .

you hit the leading edge of a piece of plywood and it splits ! it offers no strength at all being a glued laminated product a real core material is 4 times stronger and 80% lighter in a fiberglass material if it's carbon fiber is up to 93 % less weight then the same size of a wood cloth and resin part .

there are many misconceptions when it comes to splitters and there designs , materials , shapes and sizes .
one is how far a splitter sticks out from the leading edge of and bumper .
some clubs add more points for how far they stick out they are not penises so bigger is not always better .
many factors come into play with a splitters design shape of the cars nose frontal mass air flow over the nose materials being use is the car using canards or not are some factors in a splitters final design .

I just happen to be working with Lexan lately, and this stuff would make a great splitter! Strong,light and easy to work with. The 1/4" thick stuff is virtually bulletproof..and the 1/8" thick is amazingly rugged. I put a 90 degree bend on a piece and it is strong as the straight piece.Lexan (polycarbonate) is NOT Plexiglass,(acrylic) which many assume is the same stuff. Plexiglass is 20 times stronger than glass,but Lexan is 200 times stronger than glass and will not shatter.

yes lexan doesn't shatter but the down side to using it for splitters is flutter also a well design splitter should have some texture to it to reduce the boundary layer not so much for the top side but more on the under side .
the flutter is not some thing you tend to see as it's more microscopic but what it does do is change the pressures .

there is also the myth of trying to get your splitter as low to the ground as you can.
many home builders will do this !
what this does more often then not is 1st takes the splitter less efficient as for a splitter to work you need air flow over and under it . 2nd is again more often then not is it packs up air in front of the car as the air needs to go some were . you have to think of air more like a fluid . you can have a large opening on the top of a funnel but if the other side has a small opening the funnel will take a long time to drain out . the air between the ground and your splitter acts in the same way . this is why you see some splitter designs that raze up in the center to let more air pass under the car . air flow under a car is not a bad thing at all it's how it's being used is what makes it bad or good .

I just finished up another lexan job on a BMW E46 M3 and have a engine cover to build out of lexan for a MR2 coming in next .

Some Lexan has rough texture. I can't imagine anything 3/16" or larger would flutter,especially the 1/4" stuff..it's like steel! But..I'm only new to playing with it,so that's all I can go by. Makes dandy windows..

yes it does make great windows !
I knew you would pick right up working with the material also .
I have made a crap load of things out of it like cool air block off ,dash panels ,a arm rest bending it and covering it with thin foam and vinyl to some inner door panels . 101 uses !

what I like about composite for splitters is if it does take a hit you can in most cases repair it . again like I have done for Gordon .
it's allot less to repair then cut a hole new piece .

I have not seen splitters made of Lexan for some reason. How heavy would 1/4" Lexan piece be if it's about 5' wide and 1.5' long (contoured to the bumper shape on the front, so about 5 square foot area in total)?

BTW, I'm just monkeying a Nationals-winning car with plywood splitter. For autocross with speeds of about 65 mph a lot of things are irrelevant especially, I would think, texture, flutter and other esoterica. As a former engineer, I understand why they'd e important at 120+ mph speeds.

5 sq.ft...I'd say about 8-9lbs. Lets see.. I have a sheet that is 48"x48",which is 16sq.ft..and weighs 28lbs. (on my digital scale) ...so 1/4" Lexan weighs about 1.75lbs/sq.ft. ....times 5 sq.ft= 8.75lbs. You will never ever never ever never break it. Matter of fact, I will wager 1/4" Lexan would stop a .22 caliber long rifle bullet. Hmm..I may try that tomorrow on a scrap piece..just for giggles...

I can vouch for Dave's work and strength of the honeycomb fiberglass, very light and strong. I had the opportunity to test it few times last season, repairs came out like new.

For a flat cut splitter I think Tegris is the new material of choice http://tegris.milliken.com/en-us/Pages/default.aspx

that stuff is very god but like other composites it a matter of cost . for a race team with a good budget it is a very good option .

lexan is not some indestructible product if you hit the leading edge with a BFH it will deform the leading edge .
take a piece and go out side and hit it on a rock to see what will happen . I just did that and sure as hell it damaged the edge . I tried to post a photo but like always to do so in this forum it gives me BB to do so .
the piece I did it to was 1/4" thick .
you may think that well no big deal it has a divot but not that big .
but in fact that little 3/4 " divot does effect the air flow and the efficiency of a splitter .
even a scratch will effect the air flow of a splitter and it's efficiency .
the other problem with using some materials for splitters is the need to add winglets to the sides .
in many cases when the air just dumps off the side of the splitter it creates allot of drag . the more the splitter raps around the side of the car the more drag you will get .
this is what I was saying about some clubs add more points for the length a splitter sticks out for the front edge of a bumper . how far it does in most cases doesn't give or generate more down force often it just adds to more drag as the air has more surface to dump off of .
so with materials like lexan and sign sheeting yes it cheat or I should say low cost but it's not the best material as in many cases you want winglets . you could bolt or rivet some winglets on the side but again the down side is now you have added some thing for the air needing to flow over and around so your adding winglets to reduce drag but adding drag back in by using fasteners . at least with lexan you could flush mount the fasteners but not so with most sign board sheeting .
if you really wanted to get into using lexan you could heat and mold it but if your going to make a mold you may as well just build it out of a composite material that can be repaired for low cost and quickly . this is why you don't see lexan being use on a pro level race team .
on the GT3 Porsche team I'm the engineer on one of the drivers had an off and scratched up the under side of the splitter . not a big deal as I poured more resin over the scratches let it dry and sanded it back down with a DA and 180 then when to 220 and sprayed one coat of resin over the hole under side . it was a quick and ez low cost repair .
if the same damage happened to lexan or sign sheeting you would have to scrap the thing and make a new splitter .