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Bog vs fiberglass?
https://www.ausmini.com/forums/viewtopic.php?f=2&t=14479		 Page 1 of 2
Author:  h0nk [ Sun Jan 01, 2006 7:39 pm ]
Post subject:  Bog vs fiberglass?
You dont hear of many people using fiberglass to fill dents, or fix rust areas on body work.. why is this? Wouldn't it be better then bog?
Author:  Siclad [ Sun Jan 01, 2006 7:53 pm ]
Post subject: 
its stronger than bog, but is much harder to work :? , apparently its good for holes (obviously not a good as welding, which whould always be done to repair holes IMO)

thats only from what ive heard/figured out ay... someone else should know
Author:  simon k [ Sun Jan 01, 2006 7:55 pm ]
Post subject: 
I've only used each of them a little bit, so there will be better answers, but I reckon bog is used to smoothing over metal to get an even surface or filling cavities, where fibreglass is used to patch over actual holes.... that's what I've used them for anyway
Author:  Smokie [ Sun Jan 01, 2006 8:07 pm ]
Post subject: 
The fibreglass stuff was used on my LS to fix the rust holes in the roof as it apparently does not absorb moisture like the bog does..
Author:  Besser [ Sun Jan 01, 2006 8:27 pm ]
Post subject:  Application
Really they apply to two different needs

The "bog" which is talc infused epoxy resin is for finishing off a rough steel prifile and allowing you to work it to any thickness and still finish the painting process.

"Fibreglass" which is glass fibre strands held to gether with epoxy resin (which is 5x stronger then steel in tension) is for strength and bridging gaps. If you profile it after hardening and cut into the glass matting or strands then you will need to fill (bog) over to attain a smooth surface.

I can see a need for fibreglass on a mini except maybe as flairs. Better to steel patch and then "Bog" over the top.

A Flapper bar with get you so close to finished profile that you will only nee 0.5-2mm of bog.
Author:  Zizzle [ Sun Jan 01, 2006 8:45 pm ]
Post subject: 
I have heard that the pros will patch with steel, then fibre glass over the top to seal out the moisture, followed by bog to get a good smooth surface.

Bog is hygroscopic which will cause the steel patch to rust if your weld seems are not perfectly air tight.
Author:  mickmini [ Sun Jan 01, 2006 9:20 pm ]
Post subject: 
most automotive bog is actually polyester resin with talc. and most cheap fibreglass repair kits are also polyester resin.

but yeah - bog is a filler for smoothing SMALL dents and other imperfections. to avoid the rust issue that polyester resin fillers may present, you can use "marine" filler which is designed to be used in a wet environment and so uses vinylester resin i think, less water penetrates. any repair of a hole using filler is dodgey because it has no strength at all, and is usually done by people who want to paint oer it and sell the car on. they don't care if it falls apart in a couple of weeks time.

what most people refer to as fibreglass is resin reinforced with glass fibres in the form of chopped strands. it is very good stuff, but most repairs done using it are not done properly. you still have to get rid of ALL the rusty metal and have a perfectly clean rust free surface to bond it to. you may as well do the same prep for a welded steel repair - if you know how to weld. also you can't sand the cured article because the fibres come through the surface, so for a perfect smooth finish you still need to use filler over the top and sand that.

you can also get the glass fibres in the form of woven cloth, continuous random orientation fibre mat. there are also many other fibre/resin combinations like epoxy with carbon fibre or aramid fibre (kevlar is the dupont brand).

for really good, easy to work with fillers you can use epoxy resin mixed with glass microspheres or West Systems has something called microfibres(i think, brown stuff really light), which are all heaps easier to sand than talc in polyester. West Systems sells that stuff for boats, but they still need a paint over top to make it waterproof.

check out
Fibreglass Material Services (FMS) http://www.fibreglassmaterials.com.au/, seven hills, gosford, newcastle

Fibreglass International (fgi) http://www.fgi.com.au/ brookvale nsw , cairns, labrador, wacol qld, green fields SA, springvale vic, canning vale WA

or SP Systems http://www.spsystems.com at Mona Vale for good advice and materials for anything in composites
Author:  Miniless [ Sun Jan 01, 2006 9:21 pm ]
Post subject:  Re: Application
Besser wrote:
The "bog" which is talc infused epoxy resin is for finishing off a rough steel prifile and allowing you to work it to any thickness and still finish the painting process.


Most 'bog' people will be using isnt epoxy. Plus if it has talc in it its shithouse.

Besser wrote:
"Fibreglass" which is glass fibre strands held to gether with epoxy resin.......


Most fibreglass people use wont be held together with epoxy resin.


And what was said above ^^^

Although I think the 'brown stuff' is called microballons. Its used for underwater areas which are constantly immersed. i.e. boats in a marina.
Author:  drmini in aust [ Sun Jan 01, 2006 9:23 pm ]
Post subject: 
Both bog, and fibreglass repair kits these days use polyester resin. :wink:
Author:  mickmini [ Sun Jan 01, 2006 9:35 pm ]
Post subject:  Re: Application
Miniless wrote:
Besser wrote:
The "bog" which is talc infused epoxy resin is for finishing off a rough steel prifile and allowing you to work it to any thickness and still finish the painting process.


Most 'bog' people will be using isnt epoxy. Plus if it has talc in it its shithouse.

Besser wrote:
"Fibreglass" which is glass fibre strands held to gether with epoxy resin.......


Most fibreglass people use wont be held together with epoxy resin.


And what was said above ^^^

Although I think the 'brown stuff' is called microballons. Its used for underwater areas which are constantly immersed. i.e. boats in a marina.


that could be it, knew it was micro something
<edit> just went to http://www.westsystem.com/ and found the stuff i was thinking of - "410 MicrolightTM
410 MicrolightTM is the ideal low-density filler for creating a light, easily-worked fairing compound especially suited for fairing large areas. Microlight mixes with greater ease than 407 Low-Density filler or microballoons and is approximately 30% easier to sand. It feathers to a fine edge and is also more economical for large fairing jobs. Not recommended under dark paint or other surfaces subject to high temperatures. Cures to a tan color."

believe me this is the stuff to use. when i was at uni, we had to make a model of the supersonic business jet we designed to put in the wind tunnel. we used a CNC machine to carve the main shapes then glued them together and faired it using this stuff in epoxy. we put in about 200 man hours on that model, and it would have been much worse using bloody talc. an i got it for cost price too, since i worked at FMS (free plug)
Author:  Miniless [ Sun Jan 01, 2006 9:49 pm ]
Post subject: 
That would be one expensive filling and fairing job using west
Author:  mickmini [ Sun Jan 01, 2006 9:58 pm ]
Post subject: 
was not a real big model. i know guys who used it on 40ft wooden boats. that's expensive.
Author:  Miniless [ Sun Jan 01, 2006 10:05 pm ]
Post subject: 
I'm one of those crazy people thats done just that
Author:  Brown Clubman [ Mon Jan 02, 2006 8:32 am ]
Post subject: 
What about lead rubbing/wiping???

Shouldn't this also be in this poll?

I know virtually nothing about this method but have heard about it and some people swear by it.

Would love to hear more about it.

Cheers,
BC.
Author:  Bromley [ Mon Jan 02, 2006 8:40 am ]
Post subject: 
I have heard that lead wiping in a dying art. Very few people are doing it now because of the convenience and cost effectiveness of bog. I have been told it requires a lot of patience and workmanship but achieves flawless results. It is very expensive for these reasons.
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