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Old 07-14-2012, 11:06 PM   #21 (permalink)
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The foam is going to be the mold. It is going to be a wet layup. Will spray glue on the foam then stick the fabric on.

Paint on epoxy. cover it with peel ply. Remove the peel ply after it cures. It makes a nice surface to apply a secondary bond. The filler can be made from a paste of wood fiber or micro. I will smooth it out similar to what I did on the first section then pry off the parts from the car and get rid of the foam. The part can be then glued or riveted back on to the car. I have built other objects this way including a recumbent bicycle.

Sorry for the long answer.

I still have my original whale tail I may stick it on over this structure. Before I cover it with carbon.

I drove the car into town with tufts on the back tail this evening. My wife verified that the back half of the tail had the straight back flow. The front half of the wing was still turbulent.

Thanks to all who offered ideas so far.

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Old 07-15-2012, 02:36 PM   #22 (permalink)
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Here is a little howto on how I apply composite as a wet layup over foam. The first thing that I would do is to make sure that you have the shape that you want. before you commit to using composite reinforcement.

I took the advice from euromodder and tapered the rear of the uprights in about half an inch over the length of 6-8"

I then started in with duct tape to finish putting radii on the areas where the shape didn't come out as well as I liked.


Got out the roll of cloth and made some adjustments and cut it off. I save the bits that are bigger than 6x6" as they can be used somewhere.


I use Super 77 spray to stick the composite onto the foam.


When it looks right I mix up a batch of epoxy and get my wife to paint it on.


We then cover the wet epoxy surface with polyester or nylon cloth. This ensures the edges are smooth.


The edges that don't want to lay down or are upside down we cover with duct tape.


Before it hardens completely (it is still green) is a good time to trim up any areas that might need it. I also peel off the cloth before it cures fully. Let it cure, then work on the surface with flox. Once the surface is to your liking take the parts off dissolve out the foam do a final trim and put them back on the car with shoe goo and rivets if you need them.

The cloth that I am using is 25 oz triaxial weave carbon fiber. It is really thicker than I would like but it makes a very hard part with a single layer. Fiber glass would work if you were to commit to 3-5 layers. I have the heavy carbon in my shop so that is what I used.
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Old 07-15-2012, 04:11 PM   #23 (permalink)
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Where did you get the carbon fiber cloth? How pricy was it? You are blessed to have your wife do the epoxi. I am not that good with it.
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Old 07-15-2012, 08:36 PM   #24 (permalink)
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I bought the carbon from soller composites several years ago. I just broke into my last 5 yards of it.

Working with composites and foam is kind of artsy. Mrs says thank you.

Here is what I ended up with as of today. I put a piece of cpvc pipe on top to show the line.


I am not going to get a chance to finish it up for a couple of weeks.

We spend the last year riding around in it this old car covered with coroplast with sometimes loose duct tape on it. I could get better fuel mileage but it was kind of creepy looking. It is going to get finished up in the next few weeks. Lets hope for better mileage.
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Old 07-16-2012, 12:43 PM   #25 (permalink)
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Wow, I really like your tuft testing solution. Interested to see how this park bench style spoiler works.
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Old 07-16-2012, 02:52 PM   #26 (permalink)
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Weatherguy,

Working with this stuff takes experience to learn what works.
I don't do it a lot and learn with each time through it.

Most important steps for me are to use the foam board and get the two part foam. You can use the two part foam both as a glue and as a filler. It cures fast. Use duct tape to bridge any small imperfections. Use a fairly heavy composite cloth and spray glue it to your part. Work only on the top or sides don't try and work against gravity. Cover any wet lay ups to keep the seams and edges smooth. I get dollar a yard polyester cloth usually. On this the spoiler came out smoother than the window cover. I guess I didn't prep the foam well enough.

Don't be afraid to try something new.

Wait till you see what I do for the front of the car.
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“The further a society drifts from the truth, the more it will hate those that speak it.” George Orwell

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Old 07-16-2012, 06:44 PM   #27 (permalink)
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varn,

I did my whole tail in fiberglass but it was between Christmas and new years (18 months ago) so it (and I) were too cold it do it well. I need to rework some areas and want to improve my skills.

Where do you get your cloth? a buck a yard sounds good to me
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Old 07-16-2012, 06:58 PM   #28 (permalink)
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Weather,
I remember when you did it. Bad timing, hope you used fast cure hardener.

The cloth that I am talking about for a buck a yard is the polyester peel ply not the fiberglass or other composite material. Go to a material store and look for their clearance stuff. Usually some ugly color.
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Old 07-16-2012, 07:03 PM   #29 (permalink)
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I used the normal harden (noob) and was going slowly trying to do a good job. Then I got a job and needed the car in a few days and had to hurry it up. But the place I worked at let me park in the back of the heated shop and that helped cure it faster.

So the material you refer to, where is that used in your process?
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Old 07-16-2012, 07:18 PM   #30 (permalink)
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weather
I take strips (3"x18") of polyester or nylon cloth and cover the still wet carbon or fiberglass. They smooth the surface out and leave a finish that you can apply another layer if needed. You peel them off as the layup cures. Leaves no sharp edges.

As far as using the wrong hardener I have been there done that. Try using fast when the temps are over 90. Much worse.

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“Before a standing army can rule, the people must be disarmed; as they are in almost every kingdom in Europe.

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