Mirror copying a shape/object

[Noods]

Hi All..

I working on a project and I think I'm about to ask for a solution for an age old problem..

I'm wishing to make a prototype fuel tank/

a tank like the above... This eventually will be made from carbon fibre.. As a start I designed the 2 dimensional profile by pen and then created half of it in cardboard.. From there I either wish to produce a 3 D version via plywood layers polystyrene or clay on a wife frame.. My problem is.. Without cad or 3 d design programmes how can I replicate the first half successfully as a mirror copy, eg so I have two exact halves.. ?

I've looked on line but found nothing relevant to it..

Thank you..

 

[the snooper]

Hi All..

on a wife frame..

Thank you..

wont the wife complain

 

[the snooper]

cant you just produce the whole tank then cut in half to make moulds

 

[MattF]

Make a mould using plaster of paris then make two halves from papier mache using that mould.

 

[rikrobson]

make a series of templates for the half profile every inch or so. Then you can use them as a reference to make each side.

 

[Rocketman]

cant you just produce the whole tank then cut in half to make moulds

I think this is the only way without getting involved with CAD. This would also ensure tangency where the curves/straight lines meet up.

 

[CRB]

make a series of templates for the half profile every inch or so. Then you can use them as a reference to make each side.

Precisely the way I did the ships hulls, except negatives rather than Noods positives.

 

[rikrobson]

I'd make a positive first, then amke the mould lated. it would be easier to see any imperfections.

polystyrene would be easier to work with than ply. a layer of filler over the top and sand ti smooth to the correct shape.

Or get a 3d printer

 

[Noods]

Precisely the way I did the ships hulls, except negatives rather than Noods positives.

Anyway you can explain in a little more depth.. A you tube vid would be good if I knew what to search for... Sounds a good concept though, it's just being sure of what to do before I start
NOODS

 

[rikrobson]

A Bit like this

 

[hotrodder]

Google images station buck most of those will be male (positive) bucks that are used as a physical guide when shaping metal panels. Same principle with female (negative). The number of stations and the distance between them varies with the shape of the part i.e. more complex shapes need more, closely spaced stations to define them. Assuming the part is symetrical then if you have made templates for the left half of it in card they just need flipping for the right half

Obviously no need if using them as a guide for metal shaping but if working with composites can fill the gaps with various materials that are easier/faster to shape (plaster of paris as mentioned, polystyrene followed by a skim of bodyfiller for a smooth finish etc) and when you're finished you have a plug to pull a mold from.

If you're altering the shape of a part or starting from scratch then male bucks make more sense, even if they're created from female templates... most people find it easier/faster to tweak the shape outside curves than inside, you get a visual representation of the finished part etc

Competition Car Composites by Simon McBeath is a good book on the subject that covers everything from basic principles, buck and mold making and materials from chopped strand fibreglass through glass/kevlar/carbon cloths both wet layup with different flaours of resin and pre pregs/vacuum bagging etc

Bear in mind that the ethanol in todays petrol will soften some (many, all?) of the common flavours of resin used with FRPs or even eat them for breakfast

 

[Noods]

Good work guys... You've got my mind ticking nicely..
TY

 

[CRB]

Chaps above have got it dead right.

After a little searching for something suitable, this would appear to do the job. I could not find a suitable video though, planking to 3d routing and nothing in between.

Although the drawing is for a tanker or large cargo vessel, the concept remains.

Each line is a half-section through at an even interval, let us say 30mm. The half-stations are at 15mm, where more detail is required.

John Britten used wire and a hot-glue gun. That turned out fine.

 

[Rocketman]

Can't you use blue foam and cut it and shape it and once you have the idea shape you can lay the carbon fibre over it.

 

[Noods]

Yes I'd thought about foam and polystyrene but the issue is getting it exactly symetrical.. If you made a perfect half great, but flipping it over and it would be back to front or upside down..

 

[Rocketman]

Well it's going to be using templates at various position down the form to get what you need as out lined in principle by others. You can use foam if you wanted it's just a matter of adapting the principles.

 

[CRB]

If you built up the basic form in plywood templates, you could fill the gaps with expanding foam and then cut it back to the templates.

 

[Noods]

If you built up the basic form in plywood templates, you could fill the gaps with expanding foam and then cut it back to the templates.

That's a good idea too..

I've just stumbled on this on ...tube you... Starts off crude but boy does he achieve..

I was also going to ask.. Once you have created the shape/forme/plug would it have to be cut in half to carbon fibre it.. If you see what I'm saying, how would you get the mould out? Unless the carbon fibre was made as two halves and then joined..

Very interesting this thread now..

 

[CRB]

It depends what the shape ends up being. You could design it so the plug is in a few parts which come out, in a certain order.

Once you have the outside, an inflatable bag could probably be used.

Never done anything like this by the way.

 

[Rocketman]

If it's a core with undercuts you would have to cut it all out - only using foam would be preferred if so.

If you make a cavity instead you can have the mould split in the middle and bolted together. Once fully cured, unbolt and pull the two halves of the mould off.

edit to make it clear.
outside face is the cavity (or A surface in automotive model talk)
inside faces is core (or B surfaces in automotive model talk)