Indentations in your mold

General Composites Discussions Composites Talk
#1

I am building a mold for a wing, and want to have an access hatch to the inside of the wing. Please don’t ask me why- it isn’t important. What is important is how to do it. I am working on my wing plug right now. I hotwired a wing section, laid up a 6oz fiberglass shell (which is curing out in the garage as I write this), and the plan is to spend the rest of the week slinging body putty and sandpaper to get it perfect.

When the finished part pops out of the mold I will hopefully make next week, It needs to have an indentation for an access panel. I will then cut out a hole about 1/8" offset from the indentation so I will have a lip. I’ll then drill holes in the corners of the lip so I can screw the access panel to the part. I hope I’ve illustrated this so you can understand.

So, what is the easiest way to make this recess? My first thought was to create the recess in the plug, but I recently saw a youtube video where they guy laid prepreg in his mold, vacuum bagged it, then finished it. It looked fairly easy, but he was a pro and this is my first time doing anything with composite materials by myself (noob alert).

So, how would you do it? Thanks.

#2

I prefer to make them in the plug. Option 2 is to glue a piece of laminate into the mold.

#3

If you are planning not to pop out too much products from the mould, you can scribe the circumference of the recess on your plug, so you can find it on the mould. Then apply a piece of calibrated sheet wax the thickness you need, and round off the edges (with wax filler, or wax fillet strips.

Wax is surprisingly durable. Just keep in mind the heat resistance.

#4

If the planets align, I’m hoping to get 50 parts from the mold. Will that wax survive infusion? Thanks!

#5

Room temp cure? Just cut it out of plate aluminum, g10, or laminate with a caul plate etc… Wax or release, and double stick tape it in. Locate it with a scribe line, pins, screws etc.

#6

Yes, the wax survives infusion, and can be made to stick to compound curves.

#7

I agree with Herman, sheet wax is the way forward for your situation unless you are planning to manufacture these in numbers…