hood molding

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#1

Ok, this is the first hood i have made. I did not have a mold so i just molded right off the topside of the plug.

I used 2 layers of 2oz fg mat. I vacuum bagged it at moderate pressure ( and I think i just found my problem ). I overlaid that fiberglass skin with one layer of 3k twill cf. topped it off with vinyl ester sprayed on. I notice now with the hood skin it is warped down in two areas.

By typing this i think i answered my own question… it warped because the hood plug sucked in on itself under vacuum.

Since I know there are folks on here that know more about molding… how would you make the mold for a hood skin?

I typically use VER and tooling gel coat. What lay up schedule can you recomend for a mold tool this size?

#2

Tooling gell first. Two layers of the gel

then a skin coat of 300 gsm csm. Let that cure then denib it to loose any spiky hairs and if you have any air bubbles these can be rubbed out.
Then at least five layers of 450 gsm. csm. That will make the mould strong enough.

Make sure that your mould has good sized flanges on it and then build a frame onto the backside to stop the mould from being able to twish overtime.

#3

Thanks guys.

Is 300 gsm Mat = 1oz Mat?

Matvd, that sounds very similar to how i make other molds…

I am going to change the first layer on the tooling gel coat. Can i safely use 2 layers of 2oz fiberglass cloth then switch over to 2oz mat for the remaining layers? Just trying to not have to buy more materials, and work with what we have available here. But if it won’t work then i’ll order.

#4

As you really do not want the first layer to have any air bubbles I would not use a cloth as this is more likely to end up with air in the laminate, you could just use your heavier CSM Mat but just have to be more carefull than if using a thinner/lighter weight mat, maybe a layer of glass tissue first would help you.

Not sure if 1 Oz is the same as 300gsm but i think it might be… 1 oz is weight per sq foot isnt it? gsm = grams per square metre.

Remember big flanges!

#5

thanks, that helped me a lot! regards, chantal

#6

300 gsm is closer to 9 ounce square yard. 300 gsm is a pretty heavy product.

#7

you think that a 300 gsm is heavy weight? I oftern use 600 gsm mat on moulds and have used 900 gsm quite a few times.

#8

In the US CSM is weighed by the square foot, if im not mistaken(didnt do the math conversion) I believe 300GSM is 1oz csm, 900GSM being 3oz

#9

300 g/m^2 is .3 kg/m^2
.3 kg/m^2 x 2.2 lbs/kg = .66 lb/m^2
.66 lb/m^2 x 1 m^2/1.196 yd^2 = .552 lb/yd^2
.552 lb/yd^2 x 16 oz./lb = 8.8 oz./yd^2

If hojo is correct that CSM in the USA is by the ft^2, then
.300 g/m^2 = 8.8 oz./yd^2 x 1 yd^2/9 ft^2 = ~ 1 oz./ft^2

#10

haha, thats exactly why I didnt take the time to do the math, but I was pretty sure it worked out to 1oz just doing it in my head. Good job!

#11

Yep, you owe me, hojo! :slight_smile:

#12

GSM divided by 33.91 gives you oz sy. Divide that by 9 and you have oz sf.

#13

300 gr/m2 mat = 1 oz mat
450 gr/m2 mat = 1.5 oz mat (industry standard)
600 gr/m2 mat = 2 oz mat

300 gr/m2 woven roving = 9 oz roving.
600 gr/m2 woven roving = 18 oz roving.

You guys are driving me crazy at times…

#14

yeah I thought that was the case 300 gsm = 1 oz per square foot

#15

I’ll pick up some 1oz mat for my first two layers of the mold.

Thank you