I am contracted to make a couple TSX hoods for the Rolex Grand Am Cup and worked very little with coring materials. Right now I have 1/8 inch, 3 lb. Density vinyl core foam that I want to use. My question is how many layers of carbon fiber would I use with the core material and also will this material full vacuum with infusion? I will be using only an outer frame. The center will be cut out. Also this will be hood pinned down as well
I think the contruction of the hood should be discussed with the TSX team. You should find out what their requirements are, and go from there. You’ll then know how many layers of a certain weave and fabric weight you’ll need.
A “layer” of carbon fiber isn’t very specific. It could be 4 layers of 5oz, or 1 layer of 20oz, so you need to determine the strength and stiffness specs first.
There is no point in using both an outer frame and a core material. Choose one or the other. The outer frame would be bonded to the bottom of the hood, and would be a weak point. And reconsider using the 1/8" foam, that’s too thin. A 1/4" or 1/2" honeycomb core would provide more than enough rigidity.
Watch out for the vacuum during the bagging process. Too much vacuum and can crush some foam cores, and can cause fabric dimpling with honeycomb cores. A 2 or 3 step bagging schedule may be needed to cure the bottom, bond the core, and apply the final plys.
oh I have all the info I need from the TSX team. Maybe I should have reworded it. It is just going to be a track hood, they were going to get a ViS hood before ours. It just needs to be light yet still ridged. It will be 2 hood pinned down. I would still need the frame for the mounting brackets and latch. The top layer will be carbon kevlar. I am pretty much looking for the best suggestion on making the hood material wise. I will be infusing it so the methods or materials have to be comaptible with that. I am not stuck on using a core material. I just thought it would have been a good chance to play with it 
I can make the hood anyway I want with no weight restrictions but I want to make it as light and as strong as I can.
I am sending you some samples and there is one with 10 oz. fiberglass cloth, paper 1 mm (?) core material, 1x more 10 oz. fiberglass cloth with PER used.
Not carbon or Epoxy, but…check it out!
What speed are they racing at?
Since this is not a structual part (?) but to just cover the engine…and not to flex any to distrupt air flow…
Its funny that you post this. I was just messing around with this larger size hood and looking for a new combination of materials to both lighten and cut costs. I finished up this first version.
Using vacuum infusion, I have used with success both Divinycell and Lantor Soric. The Divinycell is used is the H80 scored with feed channels and allows the foam to conform well with a thin scrim on the back to hold it together. The Lantor Soric is good also 2mm or 4mm with feed channels. I found that I get more print through with the Lantor Soric than the Divinycell, but still get some. Either way, I would use a two stage process creating the skin first and then infusing the secondary core / under skin second. I have been using an 8 layer combination of carbon / glass with vinyl ester resin yielding a sufficiently strong outer shell. This then bonded to the subframe.
I was thinking of moving to a 1/4 Divinycell core over a 1 layer surface layer 5.7 carbon and 2nd layer of glass. The core would then be infused over this outer skin with another couple layers of carbon / glass over that. The objective being increased stiffness with a reduction in the layers / weight. Thoughts?
Yes, I understand, it’s a hood made for a race car. I can’t believe a race team would ever consider a VIS hood for a splite second!
You don’t need a frame just for the hinge mounting points, and a race car shouldn’t be using an OEM latch. Using a core material will be much stronger and stiffer than a separately bonded frame.
We have done Porsche and Mazda hoods for Speedworld Challenge cars, and were able to keep weight down to under 11 lbs. The Mazda hoods used 2 layers of 9oz S glass, 1/2" Nidacore H8pp honeycomb, and another 2 layers of 9oz S glass all with epoxy resin. It was much stiffer than stock, and was easy to lay up. The Porche front boot lids were made from 2 layers of 8oz carbon on each side of a 1/4" core. That hood was incredibly stiff, and was probably the most effective solution short of autoclaving. All this work was done with vacuum bagging and oven curing, but it should be similar to infusion. We don’t use infusion due to the limited core material choices.
I was very surprised that were getting a ViS hood at first too. They have built 2 other cars and both had ViS hoods. The top speeds are 150mph with an average of about 90mph. Kyanton, could you post pics of the underside of the hood?
Here ya go! In this picture, I have already mounted the hood brackets and other hardware. The thing with these older Saab hoods are that they swing forward when they open. That is why there is a bracket/hinge on the nose of the hood. I use Fusor to bond the subframe to the skin. The only thing I don’t like about this stuff is the yellow color doesn’t give it the finished look I would prefer.
These recent posts have got me thinking that maybe I could elimiate the subframe as a separate piece and just use 1" core material in the same place with a skin over it. I could then drill out where I needed the brackets to mount. It would probably take less time and materials also. I will have to think on this.
