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Old May 05, 2014, 06:48 AM
PB of 733kph
ALEX HEWSON's Avatar
Christchurch, New Zealand
Joined Jul 2005
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Molds on the cheap...

I am about to make some molds so we can get some 60" composite models into the hands of the locals and hopefully build a bit of a DS community in one of the best places to DS in the world!

But I can't afford to jump in and spend $1000+ on tooling resins, spray guns, compressor, etc etc. I am sorted with the plugs and parting boards, just need to work out how I am going to surface the mold. The backing is easy.

I have read of some guys using standard resin mixed with filler and graphite powder, and also think I remember Josh saying he just used straight resin on his Scorcher mold.

Ideas to help me complete this project in a small budget. I don't see it getting completed unless I can do so on the cheap. It only has to be good for up to 20 releases. I don't see myself making more than 20 models in a year. I will make new molds properly if things work out ok, next year.

Really want to be able to have some molds so my mates can fly some nicer models that don't cost heaps, are more robust and they can also be involved in the build and learn some composite skills
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Old May 05, 2014, 08:31 AM
by ZIPPER
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East Kurrajong Sydney Australia
Joined Aug 2004
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To do it on the cheap just use polyester resin with with a good layer of gel-coat and about 4 layers of chop strand glass backed with concrete.
Don't use straight resin without the glass, it gets very hot as its going off and will also crack.
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Old May 05, 2014, 09:31 AM
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Graphite powder should work fine. I did a tooling coat once using a carbon powder mixed with a standard laminating epoxy. Worked great.
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Old May 05, 2014, 10:33 AM
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That's commendable what your doing. I've done a few mold making serie's of post's here on the groups. One of them is Tango the dance begin's. I go from drawing to plug to mold's to completed aircraft. I get my quart of gel coat locally but I get most of the rest from the auto body dept at Wal-Mart, because I have one around the corner. I do polyester tool's and make epoxy/glass or what ever fuse's, etc. Understand I've been working in composite's almost all my life,i.e. 27 year's with Grumman. I just do 2 brushed coat's of gel coat and 12 later's of glass. The heating up of the lay-up, exotherm is controlled by going 3 layer's of glass at a time it usually cool's down after the exotherm has stopped then it's time for the next three layer's. I also alternate the warp direction of the glass, this also help's control the possible warp's. Hope this info help's in some way. I'll be looking forward to reading of your progress.
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Old May 05, 2014, 02:56 PM
Where is the inspiration
wdeighton's Avatar
Moira
Joined Feb 2006
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Wow, Go for it dude.

Couple of things that ma help.
When you buy resins in bulk they are cheaper. So if possible get it all at once, and if possible resin for others too.

Surf dudes use epoxy too, and the stuff they use it considerably cheap. (About 23 for 1.5L of resin)
I also sometimes use another cheap resin from another a company that supply industries. They don't really want to deal with hobbyists, and their shipping is expensive, but If I collect its dirt cheep (10/kg resin 17/kg harder 100:17 mix ratio)

Go for a quality thin resin for your first coat. I have added cabosil (Kind of defeats the purpose of buying thin resin), carbon powder and aluminium powder the latter 2 at 10%

Then for the bulking you can go for the cheapest epoxy you can get your hands on.


The other option is polyester tooling resins. The shrinkage rate is much less than normal polyester. In the UK most major players do one.

http://www.ecfibreglasssupplies.co.u...-catalyst.aspx
http://www.easycomposites.co.uk/prod...ing-resin.aspx

I have used the Optimould a couple of times and so have friends of mine. It works well.
These resins do have a short shelf life, so buy it as you need it.
This resin is really a good compromise between epoxy and standard poleyester. Also you can use these with the cheaper polyester tooling gel coats.

Wings are the more particular. Use the best product you have on these.
The section of the fuz makes the mould much more stable and less liable to twist.

If you are going to use polyester resin, try balance your layup. (Not sure if this is an old wife's tail) the point it that it should help stop the distortion. if your lay up is 50g, 100g, 200g, 600g, then go back to 200g, 100g, 50g.

It may also save quite a bit of money making "Box" moulds a bit like the AvB AB. Andrew has filled his with poraver, others fill theirs with a sand epoxy mix.
even if your box is only 20mm deep, and then some more cloth on the back again.

Use NCF (Non Crimp Fabric). IMHO its cheaper than woven and has a better resin to cloth ratio than woven fabrics.

That's all I got.
I know its a bit fragmented, and if you need some clarity or elaboration let me know.
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Old May 05, 2014, 03:01 PM
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gold coast australia
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I agree with all the above.

Also I've just made my first batch of corian. I'm doing it to try a new set of mold of my warhead 60
I'm using tooling coat first , then pouring the liquid corian into one corner. I'm doing it with epoxy ( normally acrylic or polyester)
So this makes it less polishable.
So far the tests I've done with out tooling coat have a bubble free surface. Next ones will be using SW10 tooling coat for ease of repair etc

I'm just chipping away at it an I'll know more in the next few weeks
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Old May 05, 2014, 03:12 PM
Where is the inspiration
wdeighton's Avatar
Moira
Joined Feb 2006
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Quote:
Originally Posted by timbuck View Post
... then pouring the liquid corian into one corner.
Now this is interesting.

Please do share. Where do you buy it. Is it Dear? is it expensive? Shrinkage? availability? minimum order quantity?.....

Back on topic.

Some people have been making MDF moulds. cnc cutting cavities, then some resin impregnated (Like Sean on his d3dp plugs) final cut, polish and layup.

I would probably seal the complete MDF to ensure there is no change to the level of moisture in it.
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Old May 05, 2014, 03:39 PM
ETS....Energy retention system
timbuck's Avatar
gold coast australia
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I'm making my own from filler Aluminium tridydrate. Super slow hardener with no exotherm. I pay $80 for 15kg of powder which sounds like a lot but it's very heavy ( being crushed rock)

I'm sure using same technique with very fine sand you could get a very similar result and have a mould for about $50
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Old May 05, 2014, 03:56 PM
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What about ultracal or hydrostone?
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Old May 05, 2014, 04:19 PM
ETS....Energy retention system
timbuck's Avatar
gold coast australia
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Originally Posted by AUSELECTRIC View Post
What about ultracal or hydrostone?
Very fragile.

I'm after something long lasting
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Old May 05, 2014, 04:28 PM
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Wellington, New Zealand
Joined Sep 2009
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Your commitment and enthusiasm to our mad sport is awesome, Alex! I'd be happy to fling ya $100 to help build up a kitty for this project.

I reckon you should 'crowd-source' a bit of funding to help you get there.
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Old May 05, 2014, 05:48 PM
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Australia, QLD, Elimbah
Joined Jan 2005
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I've also used Fumed Silica (Areosil/Cabosil) in tinted epoxy as a tooling surface to make a cheap mould for a PSS Avon Sabre.
Having said that, because the product was post-painted, I was always only going to use wax and PVA as a release agent ... just to be sure of a trouble free release.

D.
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Old May 05, 2014, 11:58 PM
PB of 733kph
ALEX HEWSON's Avatar
Christchurch, New Zealand
Joined Jul 2005
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Originally Posted by taurineman View Post
Your commitment and enthusiasm to our mad sport is awesome, Alex! I'd be happy to fling ya $100 to help build up a kitty for this project.

I reckon you should 'crowd-source' a bit of funding to help you get there.
I just really like sharing the joy that this hobby gives me, in any way I can I realised it is worth more to me than money to have my mates enjoy it to

Thanks for the abundment of awesome ideas and advice everyone! I really appreciate it.

The big problem we face here in NZ is sourcing product locally, and if found locally, it is usually twice the price of overseas. Hence making molds here in NZ is expensive.

I just need to find somewhere in NZ that sells graphite powder or the like. I am keen to use polyester to make the molds if possible due to the fact Polyester and epoxy don't like each other, which helps with avoid sticking in the molding process when using epoxy for parts. But which brand to use, where can I get it from, can I get it shipped for a reasonable price from somewhere else?

I have had some good help and guidance on mold making from a local and have made molds before, but using somone elses workshop and eqipment. It was a Fiberglass shop with all the gear, spray booths, guns, correct products by the drum all on hand. Am now on my own trying to work out what to use, the process is familiar with me. I have some molds for the RT42 which are made from polyester and glass with coremat backing. Has a polyester spray tooling gelcoat surface. I, unfortunately, don't have any spray gear. I understand there is brush on and spray on coatings.

Thinking of selling a few planes to get some money to get this thing moving.

I guess I am looking for guidance in the form of, Use this _____ and this ______ and you can get it from ______

Have been searching but would be making an educated guess at best what to buy, and that's not really the best approach I don't think

Just want to add, you guys rock!!!!
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Old May 06, 2014, 02:04 AM
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New Zealand, Auckland
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Are these molds for the 60inch sloper we discussed at
Soar champs?
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Old May 06, 2014, 02:04 AM
I am actually really slow
SlowBarless's Avatar
Brisbane
Joined Jun 2008
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Quote:
Originally Posted by ALEX HEWSON View Post
I am keen to use polyester to make the molds if possible due to the fact Polyester and epoxy don't like each other, which helps with avoid sticking in the molding process when using epoxy for parts.
This is a common misconception. Epoxy will stick to polyester just as well as epoxy sticks to anything else.

It's not that epoxy and polyester don't like each other. Epoxy makes a good adhesive while polyester does not. Polyester works best when it can form chemical bonds with itself, while epoxy doesn't really care what it bonds with or how it does it (chemical/mechanical).

The only real benefit of building moulds using polyester resin is cost, it's much cheaper.
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