http://www.diy.com/departments/gypro...g/35736_BQ.prd
Try that its very much like a good quality powder interior filler to sand once its properly dry but be warned its a pig to sand before hand, and 5mm depth takes 2 days to dry and that's inside on a plasterboard ceiling, not all smaller b&qs stock it I would mix a little PVA into the water too to help it stick and be less porous, I will be using it tomorrow I will do a test on something and stick it in the garage see how long it takes to set and if its up to the job. Ed/

cheers going shopping tomorrow so I will try my local builders merchants see what they can come up with any thing worth trying will add it to the post

picky update
 

had a few days off work so been on the car, front valence cut off and lowered started to blend back in the grill gap I did not like so I am going to blend it and look for a grill to cut in latter. other wing made up and the complete front end will now lift off. its going to need a lot of filler to smooth the bonnet but I will get there the resin got to the polystyrene.
starting to glass the roof and drivers door so all been well for Sunday the complete back end should be removable to work on.

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last pic the sun was shining on my toys so it would be rude not to take a pic
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Why does stuff look better when the suns out? Nice green BTW, not convinced by my filler trails, its very very brittle and the paint just sinks in coat on coat, get some Polly filler powder and try yourself but I wouldn't fancy putting the effort in when it could go very wrong whilst molding ?

not all things look better in the sun should see the mother in law not a pretty site even with the sun making you squint. did you try a plaster sealer or even pva. from experience of trying to cover damp marks in ceilings oil base paint always works and seals it ware as a water base will always show the mark.

quick pic update
 

The weather turned bad so I did not get as much dune as I hoped, but the roof has now got glass on the engine opening has been formed and the engine lid is on the way. still need to buy some filler always something


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No I pretty much destroyed the samples I did for you whilst seeing if I thought they where too brittle, I can mess about with some more tomorrow for you if you like, if i where you I'd use standard car filler for the large areas that you can flat easy with a da or random orbit sander and maybe try a powder household filler on the intricate bits. Ed

I was thinking something on the lines of the gyproc filler you said mixed one to one with a board finish plaster. it should give working time of a good 40mins then set hard but sandable. end of the day it only has to last as long as it takes to take a cast off.

It would work fine if there was absolutely no movement or flex in the surface underneath maybe add some bracing. You could also use a matt emulsion paint with a foam roller once working to the final finish, this is fantastic to sand and gives a very smooth finish, but I would be in fear of having 50 hours sanding and paint prep ready for molding then a slight knock or tweak and chunks of filler start flaking off. Have you priced up 2 part body filler from a local paint factors? The one I use has good prices on bulk.
In the car design houses they used to make life size mock ups from clay I wonder if they ever considered curing them and taking molds. Ed.

hi yep I did price and buy some easy sand car filler 15quid off ebay delivered for a 3 kilo tin.I am a bit torn what to do for the best easy sand filler is a lot of work and a lot of cost. so I do think the diy filler has got to be tried easy to sand and shape maybe add some pva to the mix .
The engine cover is the one part that can be reused after a mould has been taken so that I will properly.

well that's the car plastered
 

I've come up with what seems to be a good easy sand bulk filler 1 to 1 plaster board joint cement and board finish mixed with a good blob of pva and a hand full of cement to aid the setting time. it mixes up well and has the same texture as normal body filler sands really well when bone dry give it a good coat of pva it sets like rock. be warned only pva after you finished sanding other wise it dam hard work. After some thought I have changed the rear end of the car I was just not happy so see if you can tell the difference.

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I pulled the rear end off to flip it over to glass around the window
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rear end all change
 

started with the new filler mix nice day to plaster a car out in the sun you can watch it dry in a semi warm garage you would be looking to days to dry out fully
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before and after you can see I have stared to flatten out the wing the bonnet is not quite dry enough .
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you can just see the new body lines they now follow through front to back just need sanding out, good thing about this filler pile it on and sand it back with shape. it dose look rough at the mo but I sanded the roof off in less than a hour so a good day will make a big difference.

Looking better, you are going to have a large pile of dust before long, I told you its a pillock of a job to sand joint filler when is not quite dried out, I had to do a whole wall last week that still had a that beige tint too it after many days, your going to have your work cut out in the symmetry department though. Ed.

it dry s out pretty quick when in the sun you could fill and sand within a couple of hours even in the garage over night just about ok. as it a not a porous surface and with a bit of cement it speeds up the drying time.

Can't you use something like a cheese grater or a coarse angle grinder disk to take off the rough surface and get back to near the desired shape? Neither of this would clog and once the surfaced is roughed out it would dry a bit quicker.

As builder I would be sacked for plastering as roughly as that... We get a perfect (well nearly!) surface off the trowel. Perhaps you need a plasterer?

nay problem when its dry sands very easy problem I had the car was parked in full sun to dry it quick. all good but meant it skinned over so trying to float it over just pulled it. think thick tile adhesive then try to trowel it out smooth. A good rasp file would work but course grit sand paper works well just has to dry so it dose not clog.

Cheaper than body filler though just don't flex it, my venture with the joint compound was my first and last use of dry lining, I can't really see the benefits its quicker to plaster in fact I have put up skimmed and painted 2 other ceilings and I'm still messing about trying to get an even paint finish on the dry lined one.plus I quite like plastering, I will be interested to see how the paint seals with your mix, hope you get a good finish for the mold, you could make all sorts of back ends that would suit your new nose. Ed

I know you have a 250 swb on the way Andy, but have you made any progress on this mate?

been mega busy with the show last weekend few bits to do on the gto today then I will be back on it, smoothed it out a bit will add some pics latter . nice to see someone is interested thanks

I'm interested too... I want to see what you come up with.