What do you use for mold flanges?

General Composites Discussions Engineering Talk
#1

Hello!
I am doing some composite builds on a diy scale and wonder what you guys would use for making the mold flange/edge, especially on a multi part mold?

Lets say you want to make a mold for a car bonnet and you use an existing bonnet that you must not damage in any way. I want a flange around 2"/5cm wide that follows the splitting lines closely.

What material would you use for the flange?
How do you fasten the mold flanges on the bonnet before making the mold?

I have used foamboard for the edges, fixed by melt glue on my previous molds but it has some clear disadvantages.

Bonus question:
How do you shape the curvature of the flanges to match the bonnet?

#2

Flanges should be 6" or greater to provide adequate space for EOP excess, resin bleed, and application of bagging materials.

Make a “table” that will support the original part and extends at least 6" all around. Use foam or body filler to bring “table” surface up to match the shape of the original part. It should basically create a seamless continuation of the original part.
Smooth the surface with body filler and apply a high gloss coating. Then make the composite tooling off of that.
Before all that, make a mold that captures just the edges and trim it to the exact size of the original part. This will serve as your trimming template for the finished composite parts.

#3

Well… if you can’t damage the hood, or aren’t supposed to ( best wishes there) you can go to home depot or a sheetmetal supply company that sells 2" wide or 6" wide sheetmetal aluminum that is clad coated. Cut the metal 3" wide ( a good reason for this!). Use an all temperature hot glue gun to bond the metal to the hood temporarily. The craft type… not those industrial type may get too hot and damage the paint. Glue from the underside where you will not be laying up the mold. Use modeling clay to fill in the gap edge smooth. Take your time here because the smoother you get the clay the less sanding/finishing of the mold after. Mold release wax the aluminum and the hood. Now spray down your tooling gel coat or roll on your epoxy tooling surface coat. Laminate away! It all peels off after. Better wax that hood a minimum of 15 times with the correct wax. If you are trying to really protect the hood’s finish spray PVA on top of the wax.

Good idea on the mold template TET. I think he wants to save the paint finish on the original hood though… otherwise that is a great way to make a hood plug. Also what he said… 6" flanges are best.

#4

Ok, good info!
Not sure i understand how the mold for the trimming template works? Do you make it as just a wide strip around the rim of the part? how would you use it, trail some sort of saw along the edge and cut your part to size? Have you got a picture?

and as for getting the right curves on the sheetmetal flanges, do you have something you measure the bonnet curvature to get flange curve to fit closely or do you just have fantastic hand-eye coordination or… Smart ideas for flange fitting are welcome!

How do you splice different flanges together if they are too short?

This might seem like super easy questions but what i’m after are the smart ways to do stuff (since i’v tried some of the not so smart ones :slight_smile: )

#5

I generally use hard board wood that is about 3/16" thick, one side is shiny so it will release without to much trouble. bends easily and is easy to cut.

Hold onto your origional panel with hot melt glue gun, put masking tape on the panel where the glue will make contact (this makes clean up and removal easier). Cut some small gussets to go on the underside to stop your heardboard from flexing down.

Use clay or plastercine to fill and blend any edges, wire type clay tools are needed to do a good job of this I find.

#6

Im flanging a part at the moment that I am doing the way that I mentioned above. I will take some Pics later and while im doing it and post some pics for you to see.

#7

As I said I am flanging a part right now so here are a few pics to show you what Im doing it and hopefully let you see how im doing it. This part will have the mould in six Pieces, then layed up as top and bottom halfs that are then bonded together to form the finished part.

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Ready for waxing

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Egdes gap filled with plastercine, wire clay tools used to smooth.

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Hard Board wood attached, gussets and support frame under to stop it from moving or coming away.

#8

great pictures :slight_smile:
i should have taken pics last night as well - me and my flatmate last night released the mould we had made of a gauge holder [so the whole mould was about the size of my hands] but the flanges on that were tiny little 3cm things, and i just used hot glue to hold… i just used cardboard for that because it takes to shape quite easily, but for bigger ones maybe light mdf… i was actually speaking to a friend the other day he prefers not to flange at all if he doesnt have too…

#9

I always try to make my flanges a minimum of 6 inches, all of the flanges in these pics are over 8 inches, the flanges also help with keeping the mould ridgid aswel. I may start a thread showing my complete mould making process for this part if anone is interested. This is just a ‘hospital job’ that im pitting in here and there between other jobs for one of my regular customers so it will be a month or so probable between now and when I start pulling any panels out of the mould.

#10

Post them!

#11

Ok canyon ! which forum would you prefer for me to post in? (ill start a brand new thread)

#12

The general composites would probably be the best I assume but use your discretion. I’m really enjoying the enthusiasm here!

Cheers,
Canyon

#13

Not a problem,

Probably wont be tonight tho as my internet is on a real go slow and at its currnet speed it will take about an hour just to upload one pic! also how come I can only see the pics that I uploaded in this thread when I click on them, not just as I scroll down the page? is it the way that I upladed them?

#14

Not sure. I can see the small thumbnails in your post and then when I click on them the larger version pops out in a lightbox. What browser are you using?

#15

just using internet explorer. Uploaded the pics the way it said in the FAQ on here, post reply, click attach photo’s, upload etc etc

#16

Tested it out in my installation of Internet Explorer and I see what you mean.

Unfortunately it looks like there is a bug in Internet Explorer that doesn’t allow for the images to be properly displayed. I try looking for a fix but it seems like this is something that Microsoft needs to fix since I cannot change the way IE parses the images. I’ll keep you updated on what I find. You could try switching to another browser such as Chrome or Firefox if it’s a big issue. Sorry for the trouble

#17

Hi all,
Newbie here so go easy on me!!:wink:
I have used ali and also cheap ply with ali foil tape on for my flanges, seems to work ok, prefer using ali mind, I put Parcel tape on the buck where I intend the flange to go then make a whole load of 90 degree formers and the stick the lot together with poly filler (this knocks of the Parcel tape easily after and does not damage the buck surface) I am trying to scratch build a Porsche 917esque replica and have started with the body using some basic dimensions etc A link to a load of pictures from start to where Im at now!
http://www.flickr.com/photos/47153142@N03/sets/72157623861979360/

#18

I came across your photo album a while back on another forum whilst looking at a T70 spider body that a guy has built in south affrica. Looks like you are doing a really nice job on that, what experience do you have doing this stuff? I cant believe this is the first thing that you have ever done!

#19

Yes, that will prob be the GT40 forum, I do a build thread there when I have time. Thanks for the compliment, it is the first body I have done, although used to work for a car restoration specialist a long long time ago, so learnt about paint etc and before that used to make a lot of model aeroplanes so learnt a bit about molds etc doing that. But this is the first large scale project I have undertaken (well, large to me anyway!!!) Am still learning mind! Hence why I am on here! But my day job is a being a grumpy farmer!!:bigsmile: