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Learning how to build Lotus Seven replicas...together!
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PostPosted: April 17, 2015, 11:32 am 
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Joined: September 3, 2012, 10:48 pm
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Location: Hamden CT.
because of the project over running in cost I have to find ways to cut costs down .
for some thing like this I would have used polyurethane foam but it's at a higher cost .
a friend gave me a big stack of this pink foam some time ago and I never had a good use of it .
I though I would try using it to make a plug out of .
I know the resin eats it but I also knew that clear packaging tape makes for a low cost release for FG .
so what I did was take spray glue and glued the pink foam boards together then like you would with polyurethane foam I carved it into shape using 36 and 80 grit paper .
I then covered the foam with clear packaging tape and did my layups over it .
still not knowing if it would all just go to hell .
this morning I can in and popped the pieces I made off the plug and it kind of worked OK .
on my happy meter it's a 7.6 not the 10 I would like but it's ok .
it would have been better if I used the polyurethane foam but all and all for a low cost plug it worked .
now I have to trim the pieces and graft them into the fender .
at least I have a ok starting point to do so .
I will build up the back sides of the pieces I made so they will not be any fatter and still be even with the door skin.

I don't know the cost of the pink foam but the cost to me for the spray glue and clear tape was 15 dollars .


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PostPosted: April 17, 2015, 12:01 pm 
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Location: meadview arizona
lay the foam up with tissue and solarez, then put it outside for about 5 minutes.

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PostPosted: April 17, 2015, 12:03 pm 
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I was going to suggest that large plastic shrink wrap, but that wouldn't have worked for a shape like that. Tape will do any shape. Things like latex paint might work too. Probably not easier.

I wonder if there is something like vinyl tape that would stretch just a bit to make a smoother surface than packing tape?

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PostPosted: April 17, 2015, 1:06 pm 
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maybe some of that rubber paint stuff that people spray wheels with?

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PostPosted: April 17, 2015, 1:28 pm 
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Joined: September 3, 2012, 10:48 pm
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Location: Hamden CT.
yes like plasti dip ?
I did do a test and it did soak into the foam in little areas from the solvents .
I'm bulking up the insides . this will give me material to sand the out side down smooth .
again not the best way and the only time I would try this again is for a down and dirty plug .
but the foam was free and I have a pickup truck big load of it .


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PostPosted: April 17, 2015, 2:27 pm 
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Joined: July 17, 2008, 9:11 am
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Location: West Chicago,IL
Shellac is the answer.

When making my hardtop, I tried latex paint with poor results. Also tried the packaging tape, which was a bit better but still had issues.

When I made my half-doors, I used white poly foam, layered it with paper mache' to secure the little pellets of foam. Yeah, you read it right, newspaper flour and water and salt. You probably could skip the newspaper step on pink foam. I smoothed out the imperfections with drywall compound and sanded smooth. Then primed with a shellac based primer(Zinsser BIN) and a final coat of real shellac for the smoothness. Coated with Johnson's paste wax for a mold release. It worked OK for me as a 1-off buck.

Image

I did some experimentation over here and the next page. viewtopic.php?f=35&t=4145&start=555

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PostPosted: April 17, 2015, 2:57 pm 
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Location: Hamden CT.
there could have been many other ways to do this .
as I do it for a living I most likely have done them .
the point was not to spend any money to do them .
the budget cost to do the FG work is way over what it was estimated for .
I would have used the other foams I have here but at a higher cost .
to cut cost I also used scrap pieces of cloth .


it was all about free and not use shop supplies .


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PostPosted: April 17, 2015, 7:26 pm 
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Location: meadview arizona
cover it in baking foil.

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PostPosted: April 17, 2015, 8:05 pm 
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I was thinking aluminum foil .
I have 2 or 3 rolls in the shop as we use it when priming and painting to rap wiring in to keep the over spray off it .

I laid up 3 layers of a 9.7 cloth to in back side .
there should be enough bulk to sand the front side with some 80 grit and get it even and smooth for 3 coats of feather fill .

next I have to widen the fender flares 3 more inches to cover the tires all the way .
so I have to figure out a no or very low cost way to do that .


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PostPosted: April 17, 2015, 10:06 pm 
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I used foil to do my scuttle. Worked well. viewtopic.php?f=23&t=11633

Only thing is spend the extra bit on the aluminum tape. I used masking tape and it ended up in the bottom layer of the resin. No big deal really though. And don't forget to leave enough space for the thickness of the fiberglass. It's always needs more layers than you think (at least for me).

Cheers.

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PostPosted: April 18, 2015, 1:46 am 
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Epoxy resins won't dissolve styrene foams; I usually cover my patterns with one layer of fiberglass cloth and whatever epoxy resin I have handy. I generally have some cans of epoxy laying around that are out of date, or had their seals broken a year or more ago, or are otherwise questionable for structural use, and one layer of cloth doesn't call for much resin, but epoxies cost roughly double what polyester resins cost so you have to weigh the cheaper foam against the pricier resin if you're buying materials rather than using leftovers. To finish after cure, Featherfill or the like will fill the cloth pattern nicely, and from there, sand 'till you're happy.

One layer of light cloth gives you a firm surface to work against, but it thickens the surface by about .032" (which by amazing math coincidence is also about 1/32") but I don't often compensate by making my pattern smaller because the mold will shrink a tiny bit and the part will shrink another tiny bit, so the pattern should be a trifle bigger than the finished part anyway.
horizenjob wrote:
I was going to suggest that large plastic shrink wrap...
...which is available in big sheets at every hardware store in Autumn/Winter (and many hardware stores year 'round) as a cover for drafty windows. But be warned, the activation temp for the shrink wrap isn't far off from the goober temp of the styrene foam, so go easy with that hair drier.

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PostPosted: April 18, 2015, 5:30 am 
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Joined: August 19, 2014, 5:17 pm
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A while ago I stumbled across this article on mold making. http://makezine.com/2013/08/01/3d-print ... on-martin/

If I was not such a technophobe I would by a 3d printer and have a play, its seems a very cost effective way forward.

Bob

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PostPosted: April 18, 2015, 6:22 am 
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I used wax (a candle and canning wax) to make the connector from a turbo to the carb as well as fuel tank filler. Works great for small, complex one offs, carves easily. Melt the wax and reuse it for the next job.

Bill


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