Well I want to make a hood, I don't think to many of my customers care about what the bottom looks like too much. I was wondering if anyone had any ideas where I could just reinforce the hood with something universal?

 

Instead of making the 2 molds I'd like to just make the top and figure out a way to make the other side without another giant mold.



If Brute Force Isn''''t working your not using enough...

I guess the backing of the enginehood is important for some rigidity and stifness, the shapes of the squares and triangles of the backpart gives it's stifness to the bonnet.

I had a similar situation with a Ford Transit Hood (look I have gone all American) As this was a "one off" this is what I did. Made a good quality Mould for the outer skin. I then continued as I would for a full Mould ie leave the Hood in the Mould fill in any holes etc but instead of making a Mould of the inner skin, just lay up 2 layers of 380 grm Chopped Matt with some Black Pigment in the Resin. Once cured, trim and do any cut-outs etc. You now have a inner skin that is slightly bigger (1mm ish) than the original but provides the stiffness and mounting points for the Hinges and Catches but at a fraction of the time/cost. Bond the two  skins together and job done.

Carbon Copies Ltd

Doesn't it go against your whole concept of "Quality race parts for your exotic ride" ?

i know this may sound a little like 'you can't do that' but its not meant to. a bonnet (hood) on a car serves a few purposes, it covers the engine and looks nice, it stops people getting caught in the engine if they happen to be on the road the same time you are. but it's designed to work a very specific way.

it should fold and crumple in certain places in the event of a crash and it is also designed to be as soft as possible in the event a pedestrian happens to land on it while your out pimping your newly made bonnet.

i'm not saying that you shouldn't make carbon bonnet's as lots of company's do and sell them to the public but certain parts of the world have different law's and it could be that if you lived in one of those places that sue anyone for anything. in the event that the pedestrian that landed on your bonnet recieves more damage to their body than a steel bonnet would have caused you may end up in the court room pleeding your case.

just something to think about

A couple thoughts here,

First, if you are looking for something to strengthen the underside, you more than likely need to "tie the corners" together, especially if you do not use any +45/-45 fibers in your top laminate. The hood will barely flex, if at all, along the orientation of the carbon fibers (usually front bumper to rear bumper, or drivers fender to passenger fender), but if there are no +45/-45 fibers to take the corner-to-corner load, it can twist quite easily. I once saw a carbon fiber hood designed like this, and with the prop rod holding the front passenger corner of the hood up, the front driver's corner was halfway closed as there was nothing to keep the passenger hinged corner and the front driver's corner aligned. It looked really floppy and quite bad.

Regardless, there are three ways you can build strength into the hood that I can think of:

The first is simple, but effective. Just make your top laminate thicker. Strength and stiffness increases exponentially with thickness. The problems you may encounter here are added cost and weight, as you do not necessarily need thickness over the entire hood's surface (hence why the underside of a hood usually has triangles and channels built into it. You get more than enough strength without the added weight or cost). That being said, it would save you having to make two moulds and bond two separate pieces together.

The second, which is using my imagination slightly, would be to use aluminum rod, or aluminum c-channel, or even carbon rods or c-channels across the underside of the hood. If you design them properly, you could even make then adjustable (so that they fit different customer vehicles) but I feel that you would spend even more time and money trying to adapt that to the underside of the hood, than you would making a mould. Plus, there is no guarantee that there is enough room between the engine bay parts, and the hood when its closed, to have room for an aluminum or carbon tube.

The third option is a blend of the two. If you can make a regular thickness top laminate for the outside of the hood, but before infusing, place pre-manufactured triangular aluminum or carbon pieces onto the back of the laminate (where strength is required, and to tie to corners together). Now when you infuse it they will be bonded onto the back of your hood. I have found that a lot of people like the "rippled" look found on the backside of an infusion using the stretchy bagging material, so you could simply add it to your design element (using a non-stretch vacuum bag with the added depth of the triangular supports could create some nasty bag-seams and would be a pleating nightmare).

I agree with you that most people do not pay any attention to the underside of the hood, but that's because they are usually boring and industrial looking. In my opinion, why not make the underside of the hood worth looking at. Make your logo embossed in the carbon fiber and have a white LED cast a shadow on it. Or maybe incorporate the car's logo into the underside of the hood. Or use some carbon/fiberglass colour matched to the vehicle's paint. It could be a selling feature that could demand extra value for your products. Plus people driving exotic cars usually want something unique and have the means to pay for said uniqueness.

Just my thoughts, but let me know what you come up with and post pictures as I would like to see the final result. Your lotus stuff is looking really good, and a matching hood would look amazing!

-Mike-

A simple way would be to make a mould for a generic stiffening rib, say 1.5m long by 20cm wide.  Then you just mould said ribs, cut to length and bond on as required.  for curved parts dont postcure the ribs and remove them asap on curing then bend them while still can.

for logo'ing, trim a piece of kevlar into a logo shape you want and spray tack it under the mould. The yellow contrasts with the carbon.  I mark most my pieces with a little yellow submarine shaped piece of kevlar so i know whats mine out there.

You can just use 6mm-8mm foam core on the top part of the hood to add stifness. That's how I make hoods for race cars. Stiff & light.