id put the resin feed at the complicated light end of the mould (the top of the light if on the car) and the vac feed at the bottom.  In theory it shouldnt make much difference if you use the EC method of clamping off both ends as the resin should of travelled everywhere, but i like to have the complicated bit infused first as you can mess around a bit with resin flow etc early on in the infusion if its not going where you want etc.

With envelope bagging and putty you MUST sand the putty smooth as it WILL have small strands of fibreglass poking out and they WILL pop your bag giving you small leaks you cant find.

Ideally even seal the putty in with a resin so the surface is smooth and wont puncture bags.

I think ill be envelope bagging and laying dry then infusing resin, do i still need more than 2 flanges? where would the best 2 places for flanges be if i do just the resin in, and vacuum out flanges? The 2 farthest points from each other or across the most complicated part of the mold?

Thanks for all the advice guys I really appreciate it

Chris

yes you should use a gel coat on top of the resin as that will be a surface you use bagging tape on to get a seal (if not envelope bagging).  If you are extra paranoid about the strength of the mould, srew a few screws in half way in the putty on the mould to give a solidly mounted item the new putty will set round.  new putty on old putty will always be a slightly weak bond so an extra mechanical bit of help might stop the flange cracking off if your a bit heavy handed releasing a part or bang the mould.

I think I'm going to add a flange. It seems easy enough to do. Should I use gel-coat on top of the flange as well? How wide should I make the flange for this particular part?

Ideally you want a flange all the way round.

However you might get away with a flange at each end, one flange for the resin feed, one for the vacuum connection.

Then envelope bag it.

Ive done envelope bagging on a couple of moulds and you get virtually zero resin underneath the mould. Remember the vacuum pump is drawing a force through one axis so the resin has no reason to under the mould when the forces applied are sucking it in the part and out other side.

Only bit you will get some resin weepage is due to gravity at the sides due to your zero flanges.

What i did on one of my moulds was sand the putty smooth as it has glass strands that could puncture the bag, then coat it with a thin layer of old resin i have.  I then gave it a quick coat of easylease just in case. (Matt and Paul think i have a drinking problem with easylease but i just throw it everywhere and do loads of layers just to be oversafe).

As an alternative to whats Mr Rooty Tooty said,

I would try the "vacuum bagging" method, without the infusion side of it.

To wet my fabric on the mold then wrap the whole thing with perforated release film, then wrap the whole thing with breather cloth, then wrap it all in a bag, then pull vacuum.

Perforated release film would prevent breather to stick to the part.

Breather is meant to distribute pressure all over the part evenly, and soak up excess resin thru the perforated release film holes.

Using that method would skip the "Add a flange" process.

If you want to add a flange as Mr Rooty Tooty suggests, that can be done too. I made some test with some mold making putty: adding a coat of putty on an already cured coat of putty. It will stick together, however I did not make a real mechanical test (aka smashing it on the ground and see what happens, or using a lever to tear the two layers apart). Maybe the EC guys would tell you if it can be done in a reliable way.

I hope I helped.

 



 


    A $1000 electronic device will always protect a 10 cents fuse

Thats exactly what I was thinking of doing. Will resin pull around the whole mold even with extra flanges around the outside? Or do I tape the bag onto the flanges and pull resin over the top? Anyone have a video or pictures on how this can be done? I'm new to composites so I need some help.

As an example of my inexperience....

For something like that I'd prefer resin infusion. You've got very complex curved shapes in there and you'd be much better off laying the fabric in dry and tacking in place with a spray adhesive. You can always adjust the lay of the cloth as you pull vacuum. Then once it's all happy pull resin through Resin infusion won't cost any more than vac bagging, unless you're planning on pulling a vacuum with a hoover or sommat

There's no reason you can't use that mold with vac bagging, as long as there aren't any sharp projections. Only trouble being you don't have a flange to tape materials to I'm not sure if anyone has any reccs for that, the only thing I can think of is using an epoxy putty to build an edge up on the mold and then coating it in tooling gel, but that sounds a bit bodged. Maybe someone else has a better idea?

Can I modify this mold to use a vacuum bag? I think that may be my only real shot at visually perfect parts

Your mold is not screwed, you can scratch your resin on your mold with a plastic tool. Like bondo spreader or anything like that. Plastic would help not to ruin your mold surface finish.

Hope i helped, and good luck for your next try.

 



 


    A $1000 electronic device will always protect a 10 cents fuse