infusion for large car hood

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#1

I am in the early stages of preparing to do a vacuum infusion of a large car hood to be done in carbon fiber. I have watched the “Easy composites” video on how they did theirs but my setup will be somewhat different and i had some questions regarding the best way to go about it. The hood itself is quite large at around 4.5ftx5ft (1.37x1.53m) and has some contours but nothing all that difficult.
first is the carbon for the hood. I plan to use 3 layers of 5.7 oz (160gram) 3k twill weave for the hood with additional carbon tape strips along the perimeter to increase its chip resistance and add a little stiffnes to the hood. This hood is for a drag race only vehicle and needs to be as light as possible but still stiff enough that one person could take off alone from one side of thw hood. In the easy composites video they had only 2 layers of cabon and one layer od soric as a flow media. would a hood as large as mine require a glow media between layers? could i get away with only 2 layers of carbon and no inter layer flow media? for the carbon layers the visible layer will have to be a specially sourced wide roll fabric so there is no seam lines on the top of the hood. if i use that as to first layer but use less wide fabric for the seccon layer and have a seam line somewhere on tw underside of the hood will the overlap print through to the surface layer?

since the component is so large will i need to do something special with the resin infusion inlet and channels to ensure it will travel the part in a 2 hr timeframe? should i be looking to get a really fast resin travel rate to make it across the part? will that induce voids on the surface?

for the mould surface if it is a “perfect” surface and i am using wax and pva for release will I still have to clear coat the hood after? would using frekote be worth the investment?

If i leave the layup in the mold for several days to ensure it cures without distortion will that cause difficulty in releasing it from the mold later?

the mold will be made out of glass an i will be using some wood ribs as additional bracing which will be glassed into the mold but as i understand using the typical glass resin has a lot of shrinkage and distortion, should i use epoxy resin or can i get away woth the othey type (the name escapes me). if i have to use epoxy is there a epoxy friendly gel coat? or something similar that will produce a good surface?

#2

I can help with some of your questions here but not all.

I would be using a core in something that size and would go 2 CF, core, 2 cf, but you could get away with out depending on the ribs/shape and possibly using some tape through the hood to assist with stiffnes.

If the mould surface is perfect chances are your part will be perfect with the infusion process.

you mould will depend on how many your making or plan to make. there are epoxy gel coats or additives you can use to mix up your own. mixing it is usually a better option if your not planing to make lots of moulds. the next best thing is VE resin but this will still shrink a little over time.

Distortion can some what be controlled with correctly placed bracing.

#3

shrinkage? I suspect that if you don’t use a skeleton on the underside or a decent core shrinkage will be the least of the problems. at 200mph+ it will flop around like a xxxx in a sock. I tend to use 6-8mm nomex in between carbon skins or a light laminate with a carbon skeleton. stability at high speed is just as important as weight.

#4

Thank you for the replies guys, I apologize for this thread being a duplicate of my other one. I tried submitted this one on my phone weeks ago and it didn’t go through so I made a new thread of " Vac Infusion of large parts" and it is much more detailed than this one. If you do have extra answers just go ahead and throw them in there