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sam
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Hello all,
I wrote late last year and asked if assistance could be give to make a mould for a F3 defuser. race car. and that a couple of attempts had been made with a sad ending, and too the rubbish heap they went.
I have made a mould off the old defuser using glass etc. and I thought I would use this as a mould for the defuser however, my troubles began when I used foam and carbon fiber to form the underneath ribs and when it was pulled down with the vacumm bagging process the ribs become out of shape under pressure.
I am no expert with this process and I would appreciate assistance?.
Do you have to have a split mould top and bottom to form the mould.
I would appreciate your comments, I will take a photo tomorrow and post it until then
Thanks
Sam
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sam
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Group: Forum Members
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Hello
I have a photo of the job at hand, trust this may assist the suggestions. Its the underside of the rear defuser .
I look forward to your moments
Sam
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scottracing
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If you are trying to make an exact copy of this then you will run into trouble. Especially with the very thin strakes of the diffuser, and the right angles. Have a look at other modern motorsport diffusers and you will see the height of the end plates and strakes are not usually that high with the ratio to wall thickness, and they have much more blended and radiused edges. You could always make the flat diffuser, then make the strakes after and cold bond them on.
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sam
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Group: Forum Members
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Hello,
Thanks for the reply and your comments. - what bonding agent would you use in this case to bond the ribs to the under section of the defuser?.
I appreciate your comments.
Sam
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Ronny
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As Scottracing said, but i think id create the ribs as L-shaped plates (maybe T-shaped even), as the ones you already have.
That way you can use pop rivets to attach the ribs to the plate (as done today).
I recon after some use, running over the curbs and such the edges of the ribs will get alot of beating.
That way you can easily replace the worn ribs.
Also keep in mind what is over/under the diffuser, if exhaust, turbos or engine is close by, you might consider high temp resin.
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ChrisR
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If you are going to fix the fins on after then I would look at either a methacrylate adhesive, countersunk rivnuts (with thread lock) or back fixing floating K-nuts. That way you can cut the bond if needed or just unbolt the part if a fin gets damaged and needs to be replaced.
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davro
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Hi sam, I have been looking into making a diffuser from scratch for my car very soon, and I have been planning something along the lines of what ChrisR is talking about. Using a combination of separate replaceable fins using methacrylate adhesive and flush aero bolt fixings for added strength. I am also considering adding kevlar in to the stack where points of stress will occur basically where the fins are going to be mounted. I am currently trying to simulate the stresses of this using the Fusion360 software but I'm still learning 
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scottracing
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I bought some 3m DP490 of ebay for 12.99 a tube which is pretty cheap, we use it in motorsport a lot to bond everything together, if you havent any Hysol 9394 to hand. Another suitable alternative which robf1 told me about is wurth replast, about 16quid a shot on ebay, you will need to buy the correct mixing gun and nozzles for them though. But as above if you think you will need to replace them, some nice flush fit fasteners and rivnuts will do the job nicely. A combination of carbon and glass works well, if you cant afford the kevlar, Davro Im hoping to make a diffuser in the long line of parts for the caterham, will be nice to see how you get on!
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MarkMK
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As described above, I've made a single plane diffuser with strakes bonded to the underside for my Westfield and have sold a few to date I built the pattern from scratch using a combination of foam and e-glass https://www.dropbox.com/s/bhk2lai5v6n3fq4/diffuser%202.jpg?dl=0https://www.dropbox.com/s/e6yag7c25comj7w/diffuser%205.jpg?dl=0Looking at the OP's diffuser, the suggestion regarding making the flat section first and then making and fixing the strakes separately looks like the best way to go
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sam
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Group: Forum Members
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Hello all,
I do appreciate all the info to hand making the ribs seperate makes sence. and the mounting as suggested with K nuts or even a rail machined from alluminium so that adjustments could be made to fine tune its best advantage.
I have a mould from the existing defuser and I will vacuum bag up a base section and then the under section ribs/.
I"ll send a photo when its completed.
Thanks again from down under
Sam
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