Vacum bagging CF/Fiberglass

[j-c-c]

Not sure this is the right forum, doesn't look to be a hot topic here.

I'm prototyping some wing struts for my car(s). I want to overlay the struts with a composite.

Vacum bagging would be my best solution, but not ready to add to the cost/investment at this stage.

So my question, is it possible to shade tree mechanic a solution, like take two rigid steel plates, do my hand lay up, use release film, breather cloth, and sandwich the flat part between the two plates, with an appropriate amount of weight.



Anybody done/seen this technique before?

Any suggestions?

[minendrews68]

Watch the video here and see if this is something your interested in. These people sell the kits, but the video shows how.
http://easycomposites.co.uk/resin-in...arter-kit.aspx

Carl

[pro67coupe]

Vacuum bagging isn't only about the pressure your applying. It is also pulling air and volatiles out of the lay up

[pro67coupe]

You can buy a venturi to pull the vacuum. Your compressor just has to be able to keep up. I have one. I get my composite stuff from Jamestown distributors

[j-c-c]

As an added point, this project is in the prototype stage, and my goal for mimicking vacuum bagging was to attempt for max strength with minimum weight, which besides vacuum bagging removing air bubbles, etc, I thought it was real good at achieving a "dry" minimum wetness composite, never thought much about the need to remove/vent volatile compounds. If it's that important seems the typical mold/hand lay up process would be problem area, which I done many times, and never noticed an issue with volatile's? Maybe will the lower viscosity epoxies the volatile s used in infusions are greater?

[pro67coupe]

You wont really see the benefits from vacuum bagging unless your weighing you parts. Or your stressing the parts. If you weigh a vacuum bagged part vs just a normal wet layup part the bagged part will be lighter. And the bagged part will have a better resin/fiber ratio and will be less britle

[j-c-c]

Yes, weight and strength are important, these are high mounted rear wing struts. But not sure how the bagging improves strength, maybe the strength to weight ratio.

[jlcustomz]

Lots of different procedures used with vacuum bagging. Some actually suck the resin used into the material. Even the simpler versions are a lot of crap to deal with for 1 or so home projects.

Haven't personally worked with cf yet, but read several books on composites.
Have you looked into the prepreg cf yet?? this may be a better option to consider.

When making a composite part, there are 2 main methods. You can lay material over what may remain the interior of the project. This could be a number of types of foam which you could shape. Some foams can even be melted out with solvent.This method will get the project going quicker, but have to be bodyworked to be smooth. Then of course are all the different methods of making a perfect as possible mold to cast with.

Many of the cf products you see on the street are overlayed over traditional fiberglass.
Just a thought to consider, you state your project is wing struts. While strength is definitely important, even the huge old superbird rear spoiler sides to the wing won't weigh a whole lot more if made with thicker fiberglass rather than highest tech cf product. Not worth too large an effort for weight savings unless done on an all out max effort car. Not like a hood or doors.
Just sayin.
Ps I once made a flush el camino bedcover from fiberglass sheet, aluminum, & lightweight wood including a huge superbird style wing, which allowed me to see under it in the rearview mirror. entire bedcover, wing, stainless hinges, latches & gas struts weighed in @62.5lbs with paint. Sort of an old aircraft construction style. Approx 2' tall wing sides from fiberglass with 2 small steel rods in center was probably 4 lbs max. If I remember right,I ground down some residential fiberglass door skin to near paper thin, glued into shape over the base & rods, then went over with epoxy resin & fiberglass mat, then sanded, light body filler & paint.

[pro67coupe]

A vacuum bagged part will always be stronger than if the same part were just laid up. Vacuum bagging helps to bond the layers together better. And the strength benefit comes from having a better resin to cloth ratio by pulling the excess resin out of the part. As mentioned by jlcustom pre preg is ideal. But it is more expensive and probably not worth it in an application like this

[j-c-c]

I did the first layup. I'll do pics later. I'm satisfied with the plate method for now, actually came out better then I expected. Its not shiny, but is smooth because of the release material. I plan on paonting so no CF visible. FWIW, the core is 6mm 4 ply Baltic birch PW, (think Spruce Goose). The current laminated weight is 1.1lb ea strut, with epoxy and 5.5oz 2x2 CF. I'm debating adding i more layer. I will static load test until failure or around 300-400lbs if it will take it. This is a swan neck strut. Current CF wing weighs 7.1 LBs, so there will be very little dynamic loading, and car will never more then 120 mph, so DF will never get above 300lbs? between the two struts. Did I miss anything?