45 replies to this topic

[mariner]

As best I can tell the " usual" way of reproducing a steel production body part in glass fibre/composite seems to be waxing up the body panel and building a female mould in GF followed by running male copies of the panel from the master female mould.

I can see that this is best for quantity runs of GF replica panels and where the GF panel must fit exactly in the location of the steel original but I am wondering if ti is necessary for "one off" GF copies.

I was thinking that you could use the actual steel panel itself as the female mould by applying a release agant to the inside of the steel original and laying up the GF copy directly on that. I can see the copy will be slightly smaller but as steel panels are around 0.7mm thick that is a minor variation. If the GF copy is being hung on a spaceframe or similar new chassis it would seem, on the surface (!) that direct moulding should work for one or two copies.


I appreciate that the surface finish will be poorer because of the flaws and kinks inside a steel panel but some extra finishing could fix that.

Has anybody here seen this sort of direct copying one on individual panels and was it successful?

Edited by mariner, 10 April 2011 - 18:11.

[primer]

Um, have you seen the metal insides of a modern car's door? Or hood? It won't look anything like a replica, it would be as subtle as wearing a dress shirt inside out. Besides if you are hanging the glass fibre body panels around a frame wouldn't you want the them to be slightly bigger, or are you making allowance in the design of the frame so that the parts fit? Actually either way you will have to dimension the frame so that the shut lines look respectable once you hang the fibre panels.

EDIT: Can't ***** read.

Edited by primer, 10 April 2011 - 19:11.

[gruntguru]

For most of the body panels I have seen, you wouldn't be able to remove the FG part due to returns etc in the steel part trapping it.

[cheapracer]

Done it myself as have many, it works fine. I use Meguiar's Mold Release Wax, 2 coats and never once had an issue. Of course the release wax is used on both the original buck and then in the molds for each piece from then on.

And yes you have to allow for a slightly thicker panel in some circumstances but on a race or rally car no one notices the difference but for a street car they can be noticeable.

The physical side of fiberglassing is as simple as it looks, the problems arise with product variations (the time the hardener goes off) and room temperatures (again the hardener). Rig up a heat lamp in preparation, too cold is your enemy.

I also use good quality 3" paint brushes and wash them out with hot water and lots of clothes washing powder immediately, I never use acetone anymore.

Edited by cheapracer, 11 April 2011 - 09:00.

[Lee Nicolle]

There is hardly a panel that could be moulded using the inside of an existing panel as most have complex shapes inside to support or attach the panel on the vehicle. The occasional front guard maybe but then they are so light as to make the exercise hardly worthwhile.
Taking a mould from a panel is the ONLY way to get a panel that fits and even then I have never found one that fits as well as original. And that is the ones done by professionals yet alone us amatuers.
Though as Cheapy says the temps and mixes with resin afect the job. I have ever only made one panel, and that was with a good mould. It was ok for a racecar,,, just! Though I have done quite a few repairs , both in the mould and without.
Anything else though I will leave to the experts to get a good light strong panel that looks ok. Gelcoat is a good means of getting a very good finish but will always be a bit heavier than glass only though you will never get as good a finish with glass only.
My Sports Sedan was painted in straight tinter colors deliberatly as A. the paint was cheaper. B. the gelcoat came in the same colors making painting an option, and if painted using one coat of color and the stone chips did not show much at all.
If you do that gelcoating the panel ends up as much the same weight as priming then painting raw fibreglass.

[cheapracer]

Oh I didn't notice the "inside" comment before, it's quite easy actually but takes time as you need to bog up (even add steel panels) and smooth all the reinforcement's edges etc. and of course you have to mod so you don't have verticals less than about 85 degrees so you can pull your piece from the mold with reasonable ease.

I have seen doors reproduced like this.

I like the way Alpine Renault doors are done, very clever the way the diagonal brace is a part of the 'look' ...





In fact, I like Alpines! I wouldn't know what to do if someone made me choose between an Alpine A110 and a Stratos !!

Edited by cheapracer, 11 April 2011 - 12:04.

[Magoo]

If you take the internal reinforcement out of a body panel (hood, door, fender, roof) it will not hold its shape very well -- it will spring in one or more directions. If you splash a fiberglass part from it, the new piece will possess all these distortions, plus its own funny business generated in curing. Also, swages and creases in a panel will look rather different on the inside as compared to the outside. When the sheet metal is stamped, they know which side is going to show so they put the sharp draws to the outside and hide the weak ones. The convex side of a swage will be much crisper than the concave side, so a copy taken from the back side will be much softer. All this might be marginally ok for a race car that needs to look good from 30 ft, but for other uses the results will tend toward the disappointing.

The nice thing about pulling a splash or plug from a part is you can then easily tune, finish, and perfect the plug. Then you can pull a mold from the plug and in turn tune, finish, and perfect the mold. A little bit of touching-up effort here reaps big gains in the results. And you can reinforce the mold to make it nice and rigid so it doesn't warp or rack. Then you have a fair chance of pulling a decent part.

[cheapracer]

And you can reinforce the mold to make it nice and rigid so it doesn't warp or rack. Then you have a fair chance of pulling a decent part.

thats an absolute must, I actually use expanding foam in criss cross patterns and then glass over them, this keeps the molds very lightweight - if I remember my camera tomorrow I'll take snaps.

By the way, mould is to actually shape something as in a verb and mold is the noun I believe.

[Magoo]

By the way, mould is to actually shape something as in a verb and mold is the noun I believe.

Not in America. And as you know, we make the rules.

http://www.youtube.c...feature=related

[cheapracer]

Not in America. And as you know, we make the rules.

Not true, many countries make their own rules - America allows them too.

mariner, you also need to study up about resins and matting - you can go from extremely flexible and soft panels that you can twist 180 degrees to extremely rigid (and brittle) depending on your requirements. I usually use a fine weave smooth fiberglass cloth for the top layer for good looks and ease of laying that first layer and then multidirectional fiberglass mat for strength - how many layers is up to you.

I usually go light on hardener too, about 20 to 30 minutes setting is fine for me cause I'm not running a business and I'm worried about making mistakes and time to wash my brushes out - seriously, don't worry about rollers, dabbing with brushes gets all air bubbles out just as fast and with less mess but keep a sharpened 3" nail or fork close by to prick the air bubbles that occasionally are disobedient. Oh and a large pair of scissors, sometimes the darn cloth or mat will not fold into position in a corner or overlap so you need to get a small cut in quickly.

I really like glassing, I think it's heaps of fun and very creative.

Edited by cheapracer, 11 April 2011 - 19:49.

[Tony Matthews]

I really like glassing, I think it's heaps of fun and very creative.

Smells nice, too.

[cheapracer]

Amazingly (for me) I remembered my camera ..

Just wanted to show the expanding foam (comes in a spray can) strengthing ribs, 2 piece mold because I have a 100+ degree angle that you need to unbolt to remove the workpiece. You make your basic mold over the buck and then spray lines of the foam on, wait a few hours or the next day for it to expand and dry then simply glass over the foam.

....also a finished, albeit very dusty and untrimmed piece ....

Smells nice, too.

Yep, people have been known to be very happy smelling it, usually just gives me a foul headache though.

Edited by cheapracer, 12 April 2011 - 02:20.

[mariner]

Thank you to Cheapracer and everybody else for the suggestion and comments.

I have made body panels using moulds and the mouldless process but its the slowness of mould-making and the weight of the resultant mould which has frustrated me. So Cheapracer's method of spraying foam on the back of the copy mould and then skinning it seems a really great idea.

When I make a mould off a stell panel I will try his method as I don't anticipate the need to make multiple copies frosale.

[Tony Matthews]

I think I prefer the mould, looks quite sexy...

[Lee Nicolle]

Smells nice, too.

I personally hate the stuff, gives me a headache and it makes me itch!! But the inevitable minor repairs means I have on occasion have t ues it.
My fibreglass man used to be a kilometre away but very unsportingly moved to the country so has been very inconvenient for some years!!

[kikiturbo2]

I actually use expanding foam in criss cross patterns and then glass over them, ....

man, this is the most valuable piece of advice I read on forums in a loong while... thx..

[NeilR]

The initial mould surface still needs to be thick enough to resist the distortion of the backing foam and the added resin and cloth. So you must put enough layers into the mould.

[Grumbles]

My fibreglass man used to be a kilometre away but very unsportingly moved to the country...

I think I know him, is he named Mat?

[kikiturbo2]

Matt Rowing maybe ?

[Tony Matthews]

Chopped Strand Matt?

[cheapracer]

The initial mould surface still needs to be thick enough to resist the distortion of the backing foam and the added resin and cloth. So you must put enough layers into the mould.

I use about 5 mm initially, let it cure for a day then spray on the foam, another 1/2 day and then then final over the foam and at least another day or 2 before I attempt to remove from the buck.

I have never had an issue with distortion even on 2 meter x 2 meter molds probably because of the minimul hardener I go with and always inside, never in the sun - my glass never gets more than just warm when going off and I'm never in a hurry when 'glassing.

Edited by cheapracer, 17 April 2011 - 06:42.

[Grumbles]

Matt Rowing maybe ?

Chopped Strand Matt?

He had several aliases but I try to avoid him. He makes my skin crawl.

[Tony Matthews]

He had several aliases but I try to avoid him. He makes my skin crawl.

I thought you must have a resin for ignoring him...

[Grumbles]

I thought you must have a resin for ignoring him...

[cheapracer]

He had several aliases but I try to avoid him. He makes my skin crawl.

Yes Mat was a man of many layers and has hardened over the years.

[Tony Matthews]

Is that why the relationship didn't gel?

If I remember rightly, Elan bonnets (hoods) had a reinforcing structure on the underside, formed by laying cloth over a sort of soft paper 'rope' with a thin, maleable wire core. It worked the same way as cheapie's foam, of course. It may have been used elsewhere on the car, but I only saw it being used in that instance. Lotus Components and the Service Department at Panshanger Aerodrome was built on glass fibre and resin, everything smelt of it, and the dust from sanding filler and gel-coat. That's probably why I've got Itchy Eye syndrome.

Edited by Tony Matthews, 17 April 2011 - 13:24.

[cheapracer]

Is that why the relationship didn't gel?

Well the catalyst was that Mat, unknown to Grumbles when he needed a hand, was laid up and spoke to him with an acetone, err acid tone.

Mat was chopped and was later found to be crazed.

[mariner]

I hope people will forgive me while I ask Cheapracer some real nerdy GF questions.

Being weight obsessed I have never done a lay up as thick as 5 mm before - how many layers of mat do you use and what mat weight please.

As it is usually cold in England (!) I normally use 2-3 % hardener to ensure a good reaction time. I suspect that could cause exotherm with thick lay ups. What hardener percentage do you use please?

I think you mentioned using Meguiar's Mold Release Wax,I just use a non silicon car wax normally and it seems to work fine. Is there any reason why I would have to use specialised Meguiar's Mold Release Wax for this process?

thanks

[Tony Matthews]

Being weight obsessed I have never done a lay up as thick as 5 mm before -
thanks

If I can butt in, I think cheapie meant 5mm for the mold. He's obviously got the Mold Release wax franchise...

[OfficeLinebacker]

That's probably why I've got Itchy Eye syndrome.

Is that what you tell your wife when you're out and about in the summer?

[cheapracer]

I hope people will forgive me while I ask Cheapracer some real nerdy GF questions.

Being weight obsessed I have never done a lay up as thick as 5 mm before - how many layers of mat do you use and what mat weight please.

As it is usually cold in England (!) I normally use 2-3 % hardener to ensure a good reaction time. I suspect that could cause exotherm with thick lay ups. What hardener percentage do you use please?

I think you mentioned using Meguiar's Mold Release Wax,I just use a non silicon car wax normally and it seems to work fine. Is there any reason why I would have to use specialised Meguiar's Mold Release Wax for this process?

thanks

5 mm roughly (3 or 4 layers) for the mold plus the whatever you use for strength, plastic pipes, steel tubes, expanding foam in my case and then another single layer of close weave. I have been known to throws sheets, table clothes, T shirts, anything else to hand at molds for the 3rd and 4th layers.

Most of my workpieces are only 2 layer, one close weave cloth then chopped mat plus area strengthning as required or some slight ribbing with rope or similar as Tony mentioned by Lotus - even strips of steel, just depends on the purpose. I always do a dry run first with the mats and keep some pre-cut hand sized squares for corners etc.

I use around 2% as a starting measure but you need to test for 15 to 30 minutes cure each batch you buy, I have found large differences even with the same brand products. Cool is good (but not silly cold) but make sure you have heat lamps ready, if it doesn't go off in 30 minutes get those lamps going.

Meguiar's Mold Release Wax is obviously based on their range of car waxes so in the words of Billy Joel "don't go changing ..." if what you currently use works - but there is better release waxes than others thats for sure.

[Tony Matthews]

Is that what you tell your wife when you're out and about in the summer?

She can tell by the way I walk...

[carlt]

Another good way of adding strengthening ribs is to use the foam lagging tubes for 15mm plumbing pipes,
these can be split lengthwise to form half round lengths , laid in after the first lay up and glassed over to form nice straight ribs in the back of panels , ideal for large panels such as doors , bonnets etc , but really anywhere you need a strengthening shape.
They weigh next to nothing and can be laid up all in one process and look nice and tidy

[mariner]

Another rather esoteric but cheap fabrication technique was used to make carbon fibre tubes for one of the early man powered planes.

Apparently you wrap CF tape around an aluminium tube as tightly as possible and then heat the assembly in some sort of box which does not have to be pressurised. The auluminium expands thus compacting the CF tape together whilst the heat cures it.

Then you fill the aluminium tube with acid to destoy the tube mandrel without damging the CF as it is not prone to acid attack.

I have to say that I have never used this idea but it seems to have the advantage of producing a CF part via an autoclave like process without all the cost of an autocalve.

[kikiturbo2]

Another rather esoteric but cheap fabrication technique was used to make carbon fibre tubes for one of the early man powered planes.

Apparently you wrap CF tape around an aluminium tube as tightly as possible and then heat the assembly in some sort of box which does not have to be pressurised. The auluminium expands thus compacting the CF tape together whilst the heat cures it.

Then you fill the aluminium tube with acid to destoy the tube mandrel without damging the CF as it is not prone to acid attack.

I have to say that I have never used this idea but it seems to have the advantage of producing a CF part via an autoclave like process without all the cost of an autocalve.

I saw this method used for fishing poles and lamp posts... but the mandrel was never destroyed, just heated / cooled, and then the finished product is simply pushed off the mandrel...

[cheapracer]

Then you fill the aluminium tube with acid to destoy the tube mandrel without damging the CF as it is not prone to acid attack.

Swimming pool acid (hydrochloric acid), ask me how I know?

Glad you asked....

As a young teen I was delighted to find that swimming pool acid was a wonderous thing for removing any amounts of rust off any steel, amazing results so one day when I found a lawnmower engine laying around all seized up I threw it into a drum of swimming pool acid and the next morning there was a cam, gudgeon pin, crankshaft some valves etc all spotlessly clean like brand new but other than a black bubbly gunge floating on the surface not one spec of the aluminium cases or piston to be seen

I have since learnt to clean aluminium in swimming pool acid as well but in weakened doses (mix with water) and of course very short times and drop part into a bucket of water overnight immediately.

Great idea actually, never thought that could be a way to make fibreglass glass tubes/pipe and other various shapes..

Edited by cheapracer, 21 April 2011 - 09:39.

[Catalina Park]

We use acid for washing concrete trucks. We used to use hydrochloric acid but now we use a blend that is citric acid and some other acid that I can't remember. (probably a side effect of the acid)
The hydrochloric acid is a lot nicer on aluminium than the citric acid blend. Hydrochloric will eat the aluminium fairly slowly where the citric will chew it up quickly. It just foams up, turns black and pretty soon there is nothing left.

[mariner]

I saw this method used for fishing poles and lamp posts... but the mandrel was never destroyed, just heated / cooled, and then the finished product is simply pushed off the mandrel...

That is even beter. IIRC they were making tubes with a taper so maybe that is why they washed out the Aluminium as it couldn't be simply withdrawn. I suppose if you felt VERY brave you could make radius arms this way but that is way beyond any amateur stressing/CF knowledge thing I think.

[Tony Matthews]

IIRC they were making tubes with a taper so maybe that is why they washed out the Aluminium as it couldn't be simply withdrawn.

With, or without, mariner? Surely with a taper it's even easier...

[275 GTB-4]

We use acid for washing concrete trucks. We used to use hydrochloric acid but now we use a blend that is citric acid and some other acid that I can't remember. (probably a side effect of the acid)
The hydrochloric acid is a lot nicer on aluminium than the citric acid blend. Hydrochloric will eat the aluminium fairly slowly where the citric will chew it up quickly. It just foams up, turns black and pretty soon there is nothing left.

Whats wrong with muriatic acid/spirits of salt!! not fragrant enough for the agitator boys...phhhffttt!

[Tony Matthews]

...some other acid that I can't remember.

Uric acid? I've seen that used on vehicles, mainly on wheels and tyres, in the dark of night...

[mariner]

With, or without, mariner? Surely with a taper it's even easier...

I think the taper would be a both ends so as to have the maximum cross section in the middle where the bending stress is greater. Also this reduces the size of insert needed to fit a metal joint mount onto th CF tube.

From all your famous drawing days you may recall the special french alloy radius arms which were formed of one peice but were bigger in the middle than at the ends where the uniball joints were screwed in. I think Matra was a big user of those special radius links which I suspect were mega expensive by the standards of the 1970's.

[Catalina Park]

Uric acid? I've seen that used on vehicles, mainly on wheels and tyres, in the dark of night...

Surely you are taking the piss?

[Greg Locock]

Jim Cook (motorbike frame fabricator) built our solar car chassis from expanded polystyrene rods (about 2" diamater) then vac bagged the prepreg down onto that. He didn't need to destroy the core as it was so light. Obviously almost any 3D shape is possible like that.

I like the idea of heating the aluminium mandrels, that'll tend to eliminate any danger of wrinkles.

[Lee Nicolle]

Friends used to put all the dirty parts into a drum of real citric acid.,,,, Lemons, straigjht off the tree.,,,,,It worked really well and I feel sure they used it on alloy too. Though I may be wrong.

[Tony Matthews]

It removes limescale from shower heads, too. Oh, not the plumbing thread...