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Author: Subject: Ducktape moulds – cheap and cheerful
Mr Whippy

posted on 20/11/17 at 11:12 AM Reply With Quote
Ducktape moulds – cheap and cheerful

Ducktape moulds – cheap and cheerful

Hi,
Just a quick one. I’ve had to knock up simple cheap moulds for GRP items, out of foam, wire mesh and bits of wood stuck on, very basic requirements. Rather than spend heaps of time finishing these off with wax and release agents etc. which usually puts me off the whole moulding idea. I’ve simply covered the mould surface with duct tape which seems to be a great method of knocking out panels for things like inner wings or covers in no time at all.

I’ve used both black and silver coloured versions of the tape and the silver one seems to work best. I’ve only used polyester resin for these mouldings so not sure if epoxy will behave the same but as the GRP cures it seems to penetrate the tape and make the adhesive soft. You’ll find no battles to remove the moulding and the tape and new part just pulls away from the back moulding surface, the tape itself peals easily off the GRP leaving no sticky residue. Ok I wouldn’t tend to use it to make exterior body panels but for parts like inner wings, covers etc, its ideal. There’s no damage to the mould at all and put on some new tape and you’re ready to go again. Want to change it or sort imperfections, fine, slap on some filter/foam/wood etc and then recover that bit with some more tape, simples.

Last night I knocked up a new inner wing for the landrover, which has an annoyingly difficult shape to do in metal due to the power steering conversion and I was not happy with the aluminium first attempt. The moulded part is now busy curing out of the cold but thought I’d show you how basic the mould needs to be. I laid up quite a few layers of GRP so it actually looks smoother than the mould once finished. For what it is, its fine and besides its then coated in underseal so perfectly acceptable…if I had more time or could be bothered I could have got it looking prettier.

I also did a little landrover bonnet a while ago which shows how a body panel can be quickly made up, this took only two nights (4hrs) to produce to this finish.

Hope this helps someone






[Edited on 20/11/17 by Mr Whippy]

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theduck

posted on 20/11/17 at 11:51 AM Reply With Quote
I’ve used parcel tape before to do exactly this, works well and intend to do it again on my current project.
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Schrodinger

posted on 20/11/17 at 12:00 PM Reply With Quote
somthing else you can use if you have easy access to it is acetate sheets used on overhead projectors but I guess they are not that common these days and they used to be expensive new.





Keith

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drt

posted on 20/11/17 at 01:27 PM Reply With Quote
I used aluminium heat insulation tape, since it's the most smooth...
(see exoskeleton thread) BUT it still was a PITA to get the mold of the model!
What release agent did you use ?

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mark chandler

posted on 20/11/17 at 01:33 PM Reply With Quote
Cling film for me, gives a lively smooth finish as well, where it's not crinkled up that is!
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Simon

posted on 20/11/17 at 07:46 PM Reply With Quote
I used brown parcel tape a few years back when doing my bonnet but had serious issues when it reacted and bubbled up - took a lot of filler and sanding to fix
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Mr Whippy

posted on 20/11/17 at 10:26 PM Reply With Quote
and here is the finished part fitted to the landy, more than strong enough and a perfect fit

not bad for two nights work


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motorcycle_mayhem

posted on 21/11/17 at 09:43 AM Reply With Quote
Thanks, another use for duct tape, and one I hadn't considered. Normally I only use it to hold things together in/on a mould.

Duct tape is essentially rubber with (assorted) cross-linking agents, pretty immune to styrene attack. Your parcel tape (however) normally consists of a styrene co-polymer so unsure if that'll work as well.

I normally 'tape surface' rough mouldings with a clear tape specially made for the job (styrene-proof). It's not too expensive from your local GRP material stockist and does give a smooth weave-less finish.

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theduck

posted on 21/11/17 at 04:51 PM Reply With Quote
I must have been lucky before. Stupid question time, if I wanted to test the tape I had was safe with the resin I have, could I just put the resin on the tape or would I need to mix up with the hardener? The stuff I have uses very little hardener and so mixing up a very small quantity to test would be a pain
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theduck

posted on 21/11/17 at 04:51 PM Reply With Quote
I must have been lucky before. Stupid question time, if I wanted to test the tape I had was safe with the resin I have, could I just put the resin on the tape or would I need to mix up with the hardener? The stuff I have uses very little hardener and so mixing up a very small quantity to test would be a pain
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rusty nuts

posted on 21/11/17 at 07:17 PM Reply With Quote
Another vote for cling film.
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motorcycle_mayhem

posted on 22/11/17 at 10:39 AM Reply With Quote
quote:
Originally posted by theduck
Stupid question time, if I wanted to test the tape I had was safe with the resin I have, could I just put the resin on the tape or would I need to mix up with the hardener?


No question is 'stupid', only those folk who don't ask them.

The solvent is the styrene, assuming you're meaning polyester here, which is in the resin, not the 'hardener'. 'Hardener' in the polyester context is simply a peroxide that gets the styrene cross-linking. Remembering your school chemistry, I teach it as a drawbridge opening (that styrene C=C double bond).

I've found a German-manufactured parcel tape in Aldi which is resistant (to a point) which might be akin to the tape you've had success with. Certainly the thin/fragile shite that I've obtained everywhere else has been far less applicable (for any purpose!).

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Mr Whippy

posted on 22/11/17 at 12:25 PM Reply With Quote
quote:
Originally posted by rusty nuts
Another vote for cling film.


only prob with cling film is it would not work in my case of a vertical surface but I'd guess you'd get an even better finish than ducktape

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