heating fiberglass molds

Anyone want to share ideas and techniques for heating and cooling of fiberglass molds?

I've heard of using copper tubing imbedded in the mold. I'd like to know exactly the best way this is done. And what is used to heat and circulate the water/oil in the tubing

Also if you know any good websites on the subject please post them.

Anyone up on this stuff?

Thanks
Vanbokklen

 

So no one here uses built in heating in their tooling?

 

We looked at it, but it was not practical at all for one-off's and the like. We were also worried about cool spots on the mold.

Our plan was to use copper refrigeration tubing, a circulation pump, reservior and a Bosch on demand hot water heater all with glycol fuid. That plus a insulated tarp over the top of the mold would bring us as high as 170F.

The risks made the savings less attractive, we went with an oven instead.

 

I agree the oven is the best choice.

 

One-off oven's can also be built quite easily using plastic pipe bent into hoops and heat shrinkwrap plastic. Two layers separated if you want more insulation.
Going one step further and making a "tent" (inside the shrinkwrap tent) out of light weight film plastic over the hull/deck/etc and inflating it with canon heaters and circulation fans gives a surprisingly consistant temperature over the surface's.
It sounds labour intensive, but 3 guys can build both tents over an 80' boat in about a day. The shrinkwrap tent can be put up at the start of the build thus isolating the build from other builds, and giving some control over the atmosphere for the duration of the build.

Of course, its not really feasible for production building.
A builder has heated production molds by effectively "floating" the mold in a second mold with the cavity filled with circulating heated water. Works very well if your'v got the money and inclination to set up and maintain such a system.

I had involvment with a yard that had a modular system of "clip-together" industrial insulation panels. When a particular large part was ready for heating the panels could be put together quickly forming an oven over it. They had some panels with doors in them, some attached with heating systems etc.
They also had a permanent oven for smaller parts.

Rob

 

These are very good points. I'll look into building an oven that can keep my mold and laminate at around 100 during infusion. Currently I've built a small one for post cure out of insulating board from Lowe's and infared lights, would like to get a heater though. If you have any good oven ideas let me know here. Thanks, Grant

 

I have worked with a company called Plastech TT. They spealise in making RTM mouldings. On a recent RTM mould design course, a range of possible ideals were discussed. The best idea is electrical methods. A fine mesh is attached to the tooling once the plug has been made. The meshing attached to the underside of the moulds. Check out the website. I think its plastech.co.uk

Hope this helps

 

Buckle,
Yes I know that many RTM users use heated molds. That is how I heard about the copper tubing in a seminar I went to put on by http://www.rtmnorth.com/, that was hosted by C1 about a year ago. But at the time I did not pay close attention to the heating grid attached to the bottom of the mold or how actually it was attached and they were not using it anyway at the time so I did not see the system used to heat and circulate the water in the tubing either. They only made mention of it. But I was there really for an infusion class the day before and only attended the next day to see what was up.

But I checked out the site you mention and they don't have any mention of the heating you describe. Maybe I should email them and see if they can help out with ideas. If you hear anymore would you please post back? The molds that I want to heat are for smaller parts so actually if I could get the oven thing down that would work too.
Thanks!

 

I know it's an old thread, but I wonder how you got on with your mould heating problem?

We plan to heat our moulds with copper pipe on the grounds that it is a simple, readily available, reliable solution.

The plan, so far, is to use a standard gas central-heating boiler. This will supply radiators in the workshop during the day, and the hot water will be diverted at night to the moulds for a 10 hour post-cure programme.

Christopher