First time to make a mold. love to have some questions answered.

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#1

I have a quarter panel i plan to copy and make an overfender out of it.

the quarter panel is New, not attached to the car, still in OEM crate.

If i can post a series of questions i have in mind, it would be great to get your opinion or input.

I have read and viewed about 20 hrs of videos, articles, how-to’s.

I have purchased the following,

1 roll of 38" 300gram/ 1.0oz CSM
1 roll of 50" 450gram/ 1.5oz CSM

2 5 gallon pails of unwaxed resin
1 5 gallon pail of unwaxed gelcoat
1 1 gallon pail of unwaxed tooling gelcoat
1 quart of air dry additive (unwaxed to waxed for final coat of resin)
1 gallon of MEKP
1 gallon of PVA
1 gallon of Acetone
1 carnuba wax tin

1, whats the best method to clean the surface? acetone? soap/water then dry?
2, wax on, let it sit for how long, wipe off, then repeat how many times?
3, PVA, sprayed on with preval sprayer. how many coats? does the PVA make the surface mold to the outcome of the PVA layer or still reflects the original surface? how long to wait after dry for next step?
4, tooling gelcoat, after i reach full mil thickness, and let it dry to the fingernail test, do i only put one layer of 1.0oz and let that fully dry before making several layers on top?
5, frp, should i only put 1 layer of 1.0oz and put 1.5oz on every layer after? Or should I even go smaller, like .5oz for the first coat of frp?
6, if the mold is large, how many layers or Oz’s of coverage should i use? like 15oz worth of layers? 10oz of layers?
7, how many layers should i stack on before letting it dry, 2-3 layers, wait til dry, and add 2-3 more once again? and repeat this til full thickness? with last coat having the air-dry additive for waxed outcome.
8, how long should i wait to separate the mold from item?

9, once items are separated, and cleaned off the pva, is there any steps i need to ensure the mold is primed or ready for use? ( i read that once the item comes out, you clean, wax it, wait an hour, clean off the wax, and do this a few times. then put PVA on it, gelcoat, and 1 layer of 1.5oz, once that dries, remove from mold, and now the mold is ready for production use)

10, when it comes time to make the copies from the mold, same questions apply, wax, how many times, PVA then first layer of gelcoat, to full thickness, what size of FRP should i start with, and how many layers after of what thickness. these are just overfenders for a widebody car. no structural strength needed.

thanks alot in advance.

#2

  1. Best not to use acetone, it’s a bit harsh and flashes too quickly. Use something like Prepsol or wax and grease remover; any spray paint supply store should have it. You want to use two cloths to do it, one you soak in the wax and grease remover and use to wipe down the panel, and the other you leave dry and use to immediately wipe the panel dry. You don’t want the wet film to evaporate, you want to be wiping it dry. Otherwise what happens is you dissolve any contaminants, and when it evaporates it deposits the contaminants right back on the surface.

  2. Depends on brand. Refer to the the instructions of your specific product. Be sure that the wax you are using is specifically compatible with PVA, otherwise it will repel the PVA when you try to apply it and ruin your surface. If it isn’t compatible with PVA, I would recommend not using it. You don’t need to use wax when you’re using PVA, provided you have a sufficient layer of PVA.

  3. Go lightly with the PVA and let it fully dry to the touch before doing the next layer as it runs easily. 4-5 light coats should be sufficient, and do the last one heavy enough that it gives you a relatively glossy surface but not so heavy that it runs. You can apply gelcoat as soon as the PVA is completely dry to the touch. Your mould surface will come out the same as the PVA surface not the original, so be prepared to polish up the mould surface. Obviously the less dust and debris you get in the PVA, the less work you will have to do to get a perfect mould.

  4. Yes, this is your skin layer. You want to ensure that you don’t trap any air under this layer of fibreglass, so take your time ensuring you get all the voids out.

  5. I would recommend something lighter for the first layer of glass, 300gsm is a bit heavy and you will likely get some print through. I don’t know what the weight is in pounds, but 225gsm is the heaviest I would go for this layer, and ideally if you can get it go for a 100gsm. But don’t use surface tissue, it’s rubbish for trapping voids.

  6. Depends on the geometry of the part. For a complex part, 4 layers of 450g on top of your skin coat is normally enough. For a flat part, you’re probably going to want more like 8-10 layers of 450, and even then you may need to bond on a backing structure like pieces of timber to hold the rigidity.

  7. Nailed it.

  8. At least 24 hours if the ambient temperature is 25 degrees. If cooler, wait longer, if warmer - still wait the 24 hours. If you can be patient, you will get less print and less chance of distortion if you leave it for at least a week before demoulding.

  9. Depends on your production method and your release agent. If you’re using wax and PVA, then your described method can reduce the chance of a stick. If you’re using a chemical release agent like Easylease or Frekote or similar then you can simply apply this as per the instructions and then there’s no need for an initial splash moulding, you can go straight into production.

  10. Virtually the same process as making the mould, but you don’t need to do as many layers. You don’t NEED a skin coat for components, you can just do the gelcoat and then back it up with your complete layup. That said, I prefer to still do a skin coat - it reduces the chance of trapping voids and having weak areas beneath the gelcoat, as well as reducing print through.

#3

Thanks for letting me pick your brain. I feel much more confident now. After learning so much it is nice to be able to ask specific questions that I feel wasn’t explained well enough from the sources I found.

#4

6oz is roughly equal to 200gsm. Maybe you mean 10oz and 15oz not 1.0 and 1.5?

#5

here in canada it is 1.5oz per sq ft. not the sq meter measurement.

but looks to be the same scale.

#6

I would suggest not practining in a fender. Practice a mold on something else first. Trust me. I’ve been there.

#7

I agree with Infused. No matter how much research you do, there will always be lessons learned. The first cake a person tries to make shouldn’t be a huge wedding cake. That said, I would recommend using Partall #2 wax so you don’t have issues with the PVA.

#8

I do have a gas door that must be done with the two fenders, I could practice on that.

Thank you for the partall#2 suggestion.

Ill buy that this coming week.