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One of my winter projects is a new splitter for the DSR. I thought I'd float the question of materials of construction out to the forum. I'm looking at possibly aluminum honeycomb with either carbon or glass skin for the finished piece but I thought I'd do some testing first with marine plywood to get the shape and size down. Any other suggestions or experiences here? Based on the rules I can incorporate some diffusers etc but not sure if they will be worth the effort at our speeds. I noticed that many of the sports racers at nationals have also added some low front wings. Any pro's/cons to these vs a well designed splitter?

Thanks! 

Joe

 you are on the right path. Cardboard for a template, then plywood for the first few pieces until you refine the splitter into what you want. Then  aluminum or nomex honeycomb covered in carbon or f/glass with epoxy. It is more costly but better value to buy the carbon piece and just shape it to your plywood template.

Working with honeycombs or other core materials can be a little frustrating for the DIY'er the first time, especially if you do not have vacuum tools, and an oven available.

If you are a real cheap shade tree mechanic, and have some weight allowance to play with (I am not familiar with the weights in BM), then marine ply covered in a couple of layers of lightweight f/glass, and wetted out in Epoxy Resin (recommend West System) is a good solution. It will be heavier than a composite equivalent, but the weight is as low as you can get it, and the $$$ savings will be substantial.

One issue you may face in buying a carbon honeycomb sheet is that for most sportsracers, you will need an 8x4 sheet. The front of a Radical is wider than 4 feet, so you either have to use two pieces from a 4x4 sheet, or cough up a lot of money for a 4x8 sheet. I think the last 8x4 sheet (1/2 thick, nomex core, two layers carbon skin each side) I purchased was in excess of $400, and of course that size needs to be delivered by freight, not UPS.

A properly designed front diffuser will be more efficient than a front wing element, but will be more costly both in dollars and labor. That is probably the reason you see the proliferation of front wings - cheap and easy.

HTH

HTH

Thanks for the feed back. I do have some weight to play with as I already have 10-15 lbs of lead down low up front. I'm definitely looking at building on the cheap at first until I make sure the piece will do what I am looking for it to do. If this works out in wood and I decide to go with a composite,  can you recommend a good source for sheet material?  I'm pretty sure I need a 4x8 due to the width of the car.

Thanks again...
 

go to aircraft spruce buy the composite techniques book that was written by Burt Rutan.   then  use the MGS resin systemfrom aircraft spruce ,  it is one of the strongest and lightest i have found , the next best is the Polypoxy structural system, the last is the west system. I have found the west system is only moderatly compatable with bonding resins and polyester finishing compounds , so if the west system is not aged (at least 2 weeks in summer weather)  , sanded and wiped before skim coating for a finish,  the polyester skim coat could take weeks to harden up .  Buy vaccum bag supplies from james town distributers  they are very economical and you can use a shop vac for the vaccum source.   aluminum tape works perfect for sealing the vaccum bag  edges.  the first reference below is cloth,  the second is foam core material that can be bent shaped sanded and is compatable with both polyester resins as well as all the epoxy systems.

http://www.jamestowndistributors.com/userportal/search_category.do?categoryName=Fiberglass%20Supplies&categoryId=373&page=GRID

http://www.jamestowndistributors.com/userportal/show_product.do?pid=1586&familyName=Divinycell+H80+Grid+Scored.

I have built whole cars as well as numerous aircraft and aircraft parts using these techniques. Leave the foam in the layup as it adds structural integrity and is easy to layup over , versus  nomex honeycomb. If you are going to use honey comb then it is easy to fill the honeycomb with foam then sand and layup the glass or carbon fiber layers. Carbon fiber is very difficult to saturate correctly with all but the MGS resin system and is usually not a good place to start . Use the glass  cloth and MGS resin system  with a foam core and results with a shop vac are great. always saturate the cloth layup on a flat surface witha  a piece of bagging film under it  before placing and smoothing on the foam and applying the vaccum.  If you are planning to build hollow parts you must use a more conventional foam ( styrafoam) that is usually not compatable with polyester resins, and melt it out with acetone.

JG

JG,

is there a reason you prefer using polyester finishing compounds, rather than using epoxy with microspheres or other additives instead?

 Not nitpicking, just curious?

Grant

Yes the epoxy with microspheres takes quite a bit more talent to use effectively, has the bad effects of needing a way to ensure the sanded GLASS microsphere dust is not breathed, and does not get embedded in ones eyes, skin etc: The light weight polyester systems developed for composite aircraft and sold by aircraft spruce  and others work fantastic,are  easy to work , one can control their working time by ratio of hardner which most epoxy systems cannot , one must either elevate the temperature or use a different speed hardner for epoxies.  Since one is using the polyester as a skim coat it is only to get good surface finish with a moldless composite layup and is not used for strength  since most of it will be sanded off (almost 90 plus percent) if the bagging and smoothing was done correctly  one really does not need the hassle  of the micro sphere issues. I would use either epoxy and cotton flox then maybe  epoxy microspheres in fillet areas or large buildup areas but not in areas that are just like metal surfaces and one is attempting to produce a fast effecient way to smooth small imperfections.  One will apply a gallon of polyster surface filler that weights 5 to 6 pounds cured and sand all but .5  (one half) pound off if it is being done correctly . Now I also use spray on surfacers, both epoxy, ureathane and poyester type ,as well as different bonding and fastner attachment resins,  The right material for the right job.  For a car tub, side pods and wings  It typically takes as many as 12 to 14 different  resins and materials used in the right way to get great results for different parts of the car. For a simple splitter glass cloth , foam core and the mgs resins with a polyester skim coat to get surface finish is more than enough for that project.

jg

Gotcha, thanks for the reply.

The vast majority of my experience is boat building, or vehicle fabrication, rather than aircraft manufacture. So if the decision is made to use epoxy resins, it is usually desirable to stick with epoxy for the whole process. And usually we are not dealing with one off pieces that require a surface finish, mostly pieces from a mold, where the inside surface has the peel-ply finish (maybe knock off any high spots with a DA)

In recent years, I have had great success using a sandable primer that is high build, on area's where I am looking for a smooth paintable surface. I cannot remember the product name offhand, but believe it is a Dupont product. I am guessing it is poly-based, but I have never had any problems with interaction with the epoxy structure.

Grant

quite frankly  because i know gonzo's car  extremely well , i would put money in a diff for the car first , the spool that was in it  is a major performance limiter in solo, a good diff and the fabrication  to get the diff in and suspension components working together is about 3 to 4 k ,  the next  would be a 2006 or later motor  which is another 2500 to 5 k .

the last place I would place any money would be any type of splitter as the car shape is already very effective as is and  changes really cannot overcome the issues with the spool and the soft motor.

John,

I agree with you on the differential, it would probably be the biggest single improvement in the car as it sits now. I'm just not sure if I will keep the car long enough to bother changing it. I actually had the R1 completely done when I brought it home and it is making good HP now. If I do end up keeping the car and change the diff and motor I will throw in the Hayabusa I already have sitting in the garage and one of Taggart's units and switch over to CSR, way easier to make power out of one of those and the clutch and trans (stock or after market) are much sturdier than the newer liter bike units.

Thanks for all the info on the splitter construction. I am looking at learning at how to work with those materials so might as well make an actual project out of it. I'll definitely look into that book.