2G Rear Diffuser Design

[AngelOfPassion]

Holy diffuser!

Can you make one like that please? jk

 

[Atuca]

As a matter of fact mine is alot like this one. Look at the strake placement and then mine.

The center is not level because for the distance they had to cover, for 7* they had to make it shorter to avoid hitting the rear diff, and to go shorter and keep 7*, the end point had to be lower.

So that is why its not level at the back.

Then on the far sides they had two short multi tier diffusers. The outermost elements have a twin deck because they are shorter due to the rear wheelwells and the double deck allows a shorter diffuser section to work better. The strakes in the diffuser generate vortexes which causes the flow in the diffuser not to separate increasing its effectiveness, thus breaking the 7* rule.

Since I didn't want to hack up the bumper back there I just left that area flat.

But if you really look at it, wysiwyg.

 

[AngelOfPassion]

Yeah the middle portion of theirs is very similar to yours. But we want MOAR panels/decks/strakes! So are you going to eventually make a fully functional high rise wing for us as well?

MOAR strakes.

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[Atuca]

haha...

I am a theorist in all this, Andrew is the DSM engineer. The work he did on Nemo's car is just...There are so many strangely (to me) placed diffusers, canards, and that stuff actually takes individual engineering, balancing, and.. it's just crazy. Every car I have seen him touch just makes me giddy to look at.

I am so intrigued by aero work and what little I can do with a rear diffuser is nothing to what that man can.

Andrew has a wing he designed. It has been prototyped and due out already; I know Kevin and I are waiting on it to balance the work we have in the front done already.

http://www.amb-aero.com/files/APR004_public.pdf

At 52-degree
flap angle, it produces 1115lbf at 120mph and 1650lbf at 160mph for a 3.6:1 L/D.

^

 

[mitsumikey]

By the way I am still interested in all of this, good work still so far! I might need to get one this summer, I hope that is OK
Just bad timing for me on this one
Really interested in seeing how these look with stock bumper!

 

[Atuca]

I knew that there had to be someone closer to you that would have what you need, I will also call my supplier Monday to get some prices and we can compare notes later.

The prices I told you I get were wrong, since I buy by the roll, they are by pound not yards, so it is even cheaper.

The reason I know about this material is that I was thinking of making some tubing out of it to use maybe after the inter cooler and some after the air filter, just these out the mainstream ideas I get.

Call me if you like after you find out about it.


Mandy

No go.

The "lead guy" there said he's never heard of anything that cures at room temp that is good for over 150 degrees. He said maybe the stuff I'm talking about requires a full chemical suit, plutonium, and a flux core powered applicator.

I still will get my materials from there, but not resin from the sounds of it. You heard anything Mandy?

 

[arrowhead]

I will let you know tomorrow.
Did you call the company?

 

[Atuca]

No, just my local distributor, and by local, they are still over an hour away, but that still beats the shipping prices I was looking at.

 

[greengoblin]

A 700 vinyl ester resin would be an ideal product to use. That or a 404 isophthalic polyester resin.

Look here: Polyester Resins

 

[Atuca]

Yea I was looking at them for the 700, that was what I was going to buy, but if I go a 17oz Biaxial route, I would use first a layer of 3/4 ounce mat, two layers of the 17oz biaxial, and then nearly a gallon of resin.

I think it actually came to 3 quarts of resin for the amount that biaxial soaks up, but it is a lot.

Ordering one from there and shipping cross country, the hazard fee and shipping frieght is crazy, since I have to order so much resin at once.

But if I have no choice, I have contacted them and they said that resin would be good for me. But they quoted me 160 shipping.

 

[greengoblin]

You should be able to find a vinyl ester resin somewhere else that closer . Your in Cali right? Try these guys.

VINYL ESTER RESIN from Aircraft Spruce

 

[Atuca]

oh, I didn't know aircraft spruce did fiberglass stuff (now you mention it, I think you linked me stuff to there for the front diffuser actually..)

I'll check with them tomorrow, 200 degrees Heat Distortion Temp., F, if I am reading that right? That should work still.

This is all on you AngelofPassion, lets hope you got an accurate temp measurement You feel safe with a 200* resin?

 

[AngelOfPassion]

I think two hundred would be fine. In the winter 150 would be a no brainer with the temps I was getting the other day, but the asphalt gets hotter than 150 here in the summer on its own .

I've literally seen 130+ temperatures less than a foot off the ground here on our roads. It's up to you man but I think 150 was cutting it close...

 

[DSMnoobsause]

If temps are an issue heat reflective tape works great. Also worst case make a heat shield around the pipe or muffler.

 

[AngelOfPassion]

I think the idea if Phillip ever wants to make more of these for the community is to make it so people won't have to do stuff like that. But yes, that would help.

 

[DSMnoobsause]

I think the idea if Phillip ever wants to make more of these for the community is to make it so people won't have to do stuff like that. But yes, that would help.

Could include heat reflective tape with instructions. They come in sheets or strips.

 

[Atuca]

I am flying to GA on Saturday to get my DD. I am driving it back here, so I expect some time Wednesday I'll return. Then I have an appointment with the local fiberglass supplier on that Friday to talk about materials. Then I need to turn the barn next to the car into a "clean room" so that I can work, and then actually producing molds and such for the diffuser panel.

I got some of the tools I need shipped already, just need some resin and cloth! We're almost there. Aircraft spruce still has their 200 degree resin on back order til the 25th, so if my local supplier can't come up with anything I'll just place my order online with Aircraft Spruce and be done with it.

Good news is plug is already done and I don't see crafting the first diffuser is going to take very long (talking the week-two week time frame here, it's really cold and I think the resin will take several days to cure per layer).

Don't know if I said this already, but one good thing about living with my parents turned out to be the fact my father has been very helpful with getting stuff done to my car, and is interested in helping to produce a diffuser. That should help alot with time since I am needing to create both the diffuser panel and the sub frame panel.







-----


As to the heat reflective tape.. meh.. That is something I'll have to leave up to the installer. I am recomending people reroute their exhaust; if they stray from that idea this turns a DIY project into something even more DIY. Picking a 200* safe resin just makes those who want to keep their stock(ish) routed exhaust able to do so with a little more effort.

One tester has said they are rerouting, another said they were not; so we'll have examples of both to see.

 

[greengoblin]

You can use heat lamps and really speed up cure time. You just need to figure out the best configuration to get even heat distribution so you do not get any got spots/warping. Also you will find this resin is a layup resin(no wax) so you can take your time and lay up at a lesser pace and the glass stays tacky between coats. Then your final coat you add your wax . This seals out the air allowing a full cure( not tacky) and can be sanded. If you know all this already sorry. I had a long talk with the tech guy at us compsite a while back and this was/ is all new to me.

 

[Atuca]

The more I hear it the better.

I am going to seal that building up with plastic the best I can, but with bugs and with the horses kicking dust up not 20 feet from the building, the sooner I can get the panel sandable and not tacky the better. I'm scared a dog or cat will jump on it or SOMETHING is going to go wrong while they are curing to give me a headache.

Once again.. cannot wait til I have a garage again..

 

[arrowhead]

I am confused.

You say you have a plug made or matrix or an original like piece from which you are going to cast a mold.

Said mold will then be used to cast your new parts.

In all this process there is no heavy sanding involved, except in the first one to fix or prepare your plug for a nice casting of the mold. but you already have that, then touch up of your final pieces from the mold.

Am I missing something here?

There is no need to add wax to any of the layers, since there is no sanding involved.

 

[Atuca]

If I'm not mistaken, you had wax to the final layer of any pulled piece so that it drys hard and not tacky when using a layup resin. The gel coat side is obviously the sanded paint prepped side, but the back (or final layer when making from a mold) needs to be smooth as well.

Or am I misunderstanding the purpose of wax?

 

[greengoblin]

If I'm not mistaken, you had wax to the final layer of any pulled piece so that it drys hard and not tacky when using a layup resin. The gel coat side is obviously the sanded paint prepped side, but the back (or final layer when making from a mold) needs to be smooth as well.

Or am I misunderstanding the purpose of wax?

That is my understanding too. You can also use pva as a way to seal it so it will cure to a non tacky finish too.

 

[greengoblin]

Or you can vacuum. Bag it too.

 

[Atuca]

Yea, PVA was the route I was going to take.

 

[arrowhead]

Lets go thru the steps if you are using a mold:

1- Wax your mold and polish after each coat if you have a green mold (one that has not been used or been used very little), do about 5 to 7 coats, the wax will cover small imperfections and easier to release.

2-Spray or brush one light coat of PVA, wait until it dries well then apply a second heavier coat, (this is where you have to be careful it does not puddle up and watch for the bugs or hay), wait until it dries, do not pull it or go over after it dries as this is a film and will peel off.

3-Spray or brush the gel coat to get even and good coverage, wait until it is almost dry or it feels tacky.

4-Apply a heavy coat of resin before laying down your first 3/4 and dont pound it or be very heavy with the roller, this is your most important step, take your time and make sure you cover the overhang with resin also.

5- Like I explained to you before I lay another 3/4 as my second layer, let these 2 layers become a little tacky.

6-Ater you have laid your 2 layers of 3/4, then you can apply what ever you are going to be using.

7-Wax is only used as a sanding aid, if you want to use it.

8- After your lay ups are cured and removed from the mold, wash the PVA with water as soon as possible

9- If you want to have a smoother finish on the last layer use 2 or 4 ounce cloth, unless the material you are using has a cloth like finish to it.

Maybe I am misunderstanding your sequence, but if you have any questions feel free to call me again at anytime.

Mandy

Take your time and be patient.