Kermit the K Posted July 27, 2008 Share Posted July 27, 2008 At the bottom of the panel, about half way along the side of the body, there is bubbling under the paint. Is this a common problem? Anyone else had it? Was it serious? What's the cure? Link to comment Share on other sites More sharing options...
CageyH Posted July 27, 2008 Share Posted July 27, 2008 Yes, it is common. Yes other people have had it. Only real way to get rid of it is to reskin the chassis, and close up the gap between the footwells and the side skin, as this is where all the grot collects. Only dead fish go with the flow....! Link to comment Share on other sites More sharing options...
grahambiddulph Posted July 29, 2008 Share Posted July 29, 2008 Yes I also had this problem. Had to have new side skins fitted at Arch. Link to comment Share on other sites More sharing options...
Phil G Posted July 29, 2008 Share Posted July 29, 2008 Yep! Common problem and I wish there was an alternative to re-skinning but as yet no suggestions. I too have bad bubbling in same area. Unable to disassemble for partial re-skin at Arch due to limited space, facilities and time; therefore, left in limbo. Woe is me *cry* Phil SummerLightningHaze Link to comment Share on other sites More sharing options...
k80rum Posted July 29, 2008 Share Posted July 29, 2008 If you have to reskin, you could consider a pair of RiF sidepanels.. I'm not sure how the costs stack up but I'd imagine there wouldn't be too great a cost difference. Upsides are the problem's gone for good and you've probably saved some weight One downside would be if you decide to keep the colourscheme - painting over carbon would hurt I'd imagine Darren E K80RUM Website and Emerald maps library Superlight R #54 Link to comment Share on other sites More sharing options...
CageyH Posted July 29, 2008 Share Posted July 29, 2008 Carbon panels will still set up electrolytic corrosion with steel and aluminium.... Only dead fish go with the flow....! Link to comment Share on other sites More sharing options...
k80rum Posted July 29, 2008 Share Posted July 29, 2008 So a c/f panel bonded to an aluminium tube would cause corrosion of the tube? Eek. Sorry for the misleading information then Darren E K80RUM Website and Emerald maps library Superlight R #54 Link to comment Share on other sites More sharing options...
CageyH Posted July 29, 2008 Share Posted July 29, 2008 If you successfully manage to insulate the two from each other, you should be ok... Only dead fish go with the flow....! Link to comment Share on other sites More sharing options...
Phil G Posted July 29, 2008 Share Posted July 29, 2008 Aluminium tube. where?? Not on my car thats for sure........... I thought sevens were steel tubing which suggests that stainless steel rivets securing CF panels would not create electrolytic corrosion. Phil SummerLightningHaze Link to comment Share on other sites More sharing options...
MAK Posted July 30, 2008 Share Posted July 30, 2008 If you add carbon Side skins and make no other changes you will get CRP in contact with Steel tubes attached using rivets which can be Aluminium, or Steel/Stainless Steel or possibly Monel. You will also have the CRP in contact with surrounding Aluminium sheet at the rear and floor. Some of these are not good with regard to electrolytic/Galvanic corrosion, but this is not only dependant on the materials in contact but also affected by the relative areas of materials in contact and the environment this all sits in. Finishes on the materials (eg Paint/powder coat) do not necessarily provide an effective barrier either. I am sure there are others more experienced in these matters that would be able to provide a more comprehensive response. Safe to say replacing with Carbon Reinforced Plastic alone will not automatically solve a corrosion problem. Malcolm Link to comment Share on other sites More sharing options...
Mickrick Posted July 30, 2008 Share Posted July 30, 2008 As far as I know, you only get galvanic corrosion when two dissimilar metals are immersed in salt water. The saltwater acting as an electrolite. The less noble metal acts as an anode, and the more noble metal acting as a cathode. Therefore the bubbling of the sideskin is just good old corrosion from damp/crud, and not galvanic. Otherwise your aluminium rivets would be dissolving in the steel tubes! However if this was the case, you could run your sidelights off the chassis! 😬 As an aside, monel rivets are used on aluminium sailboat masts, and would probably be better quality than the usual aluminium ones. Or you could drill and tap the tubes, and fit countersunk aircraft screws. I'm sure an academic will be along shortly to put me right though! 😬 Link to comment Share on other sites More sharing options...
Roadsport06 Posted July 30, 2008 Share Posted July 30, 2008 It is far quicker in salt water, but it is not necessary for this corrosion BRG and Yellow nose VU06 XZX Link to comment Share on other sites More sharing options...
Mickrick Posted July 30, 2008 Share Posted July 30, 2008 But my point is, it's not "Galvanic" corrosion. More likely a build up of crap over the years, keeping the area moist. Like the wheel arches rotting out on an old car, because the mud has never been cleaned out of a dirttrap. You'll find the skins only corrode where there's a dirt trap. Like I said, if it was galvanic corrosion, the rivets would fall out of the car! Link to comment Share on other sites More sharing options...
Jason Plato Posted July 30, 2008 Share Posted July 30, 2008 more to the point ......... when are Caterham going to engineer out the grot trap 😔 *thumbdown* its another example of the lack of development or sorting basic design flaws here is C7 TOP Taffia rear gunner Link to comment Share on other sites More sharing options...
Mickrick Posted July 30, 2008 Share Posted July 30, 2008 Or get the bonnet/body/nosecone interface to fit properly! Careful DJ, criticising CC could cause an issue! 😬 (Where's she put the popcorn! ) Carbon panels will still set up electrolytic corrosion with steel and aluminium.... Another point....carbon panels won't cause rot. Or galvanic activity. Impossible. Carbon fibre isn't a metal. You add carbont to a metal, to change its caracterisics, but its not a metal. I think you're confusing the fact that carbon's a good conductor. Edited by - Mickrick on 30 Jul 2008 12:11:55 Link to comment Share on other sites More sharing options...
MAK Posted July 30, 2008 Share Posted July 30, 2008 Electrolytic, Galvanic, Dissimilar metal Corrosion - all names that describe the same process. I think all that is required is Dissimilar metals, moisture, access to oxygen Extract from a Boeing web site http://www.boeing.com/commercial/aeromagazine/aero_07/corrosn.html#table01 "...For example, graphite fibers, which are used to reinforce some plastic structure, present a particularly challenging galvanic corrosion combination. The fibers are good electrical conductors and they produce a large galvanic potential with the aluminum alloys used in airplane structure. The only practical, effective method of preventing corrosion is to keep moisture from simultaneously contacting aluminum structure and carbon fibers by finishing, sealing, using durable isolating materials such as fiberglass, and providing drainage. " I would think that corrosion has been enhanced in the location of the Bubbles mentioned above, because the mud that gets trapped between the footwell and side skin will retain moisture Yes I agree - It should not be beyond the wit of man to address this at the design stage Malcolm Link to comment Share on other sites More sharing options...
Roadsport06 Posted July 30, 2008 Share Posted July 30, 2008 Yes, your right MAK, all that is needed are two different metals, with different standard electrode potentials and rain water is enough for a galvanic cell. I think CC should supply cf panrls at no extra cost 😬 BRG and Yellow nose VU06 XZX Link to comment Share on other sites More sharing options...
Mickrick Posted July 30, 2008 Share Posted July 30, 2008 So it's not plain old oxidisation then? Link to comment Share on other sites More sharing options...
Roadsport06 Posted July 30, 2008 Share Posted July 30, 2008 There will be plenty of that too. I suppose the best place for the car would be Leguna Seca with the dry air BRG and Yellow nose VU06 XZX Link to comment Share on other sites More sharing options...
Kevsta Posted July 30, 2008 Share Posted July 30, 2008 Something I am probably going to do to pause the corrosion (it has set in and I will rebuild the car in a year or two....with RIf skins 😬 ) is to put a sacrificial anode on the car. I think they do this on boats so that this will corrode instead of the ali...will not fix it but at least pause it til you get it done (and maybe be worth doing post build to prevent it happening again) Link to comment Share on other sites More sharing options...
Mickrick Posted July 30, 2008 Share Posted July 30, 2008 Something I am probably going to do to pause the corrosion (it has set in and I will rebuild the car in a year or two....with RIf skins ) is to put a sacrificial anode on the car. I think they do this on boats so that this will corrode instead of the ali...will not fix it but at least pause it til you get it done (and maybe be worth doing post build to prevent it happening again) You'll be wasting your time. Just get some waxoil in where you can. Unless of course you're thinking of completely immersing your car. If you are building an amphibious Seven, you'll have to "bond" all the dissimilar metals of your car to the anode. Boats have a copper bonding strip running around the inside of the hull, to connect skin fittings, (usually bronze) and any other underwater gear, (P-brakets, rudders, props, shafts etc.) which is in turn connected to hull anodes. Zinc in saltwater. Anodes also have to be "in line of sight" of whatever they're protecting. So you'll need to bolt them all around your nice aluminium body. Let me know how she sails! 😬 Folks love to band around big words like Galvanic corrossion, electrolisis etc. Folks also get bonding and grounding mixed up. I'll say it again, it aint Galvanic corrosion, or any other scientific hypotheses. It's plain old oxidation. Notice you only get it in the "grot trap". I've worked in the yachting industry for over 15 years now. I see galvanic corrosion, electrolisis, stray current corrosion, errosion from cavitation, etc. all the time. You won't be getting it on your car. A powder coated tube, a bit of aluminium, and some damp, aren't the perfect combination for a galvanic cell. Edited because I got my corrosion mixed up with my errosion! 😳 Academics are seldom any use at engineering. One must have a mistrust of theorists. (Keith Duckworth) Edited by - Mickrick on 30 Jul 2008 14:51:33 Link to comment Share on other sites More sharing options...
Midnight Posted July 30, 2008 Share Posted July 30, 2008 When building my car I completely filled the area between the sideskins and footwell boxes with waxoyl and then made up little fences in front of these sections to stop road dirt, stones etc getting blown into this area and causing this usually 'damp mud' to start off the corrosion. The waxoyl might make the engine bay look a bit messy but whenever I've cleaned it off to do other repairs the steel/ally is still as good as new and only very small amounts of crud need to be hoovered from the area in question. Link to comment Share on other sites More sharing options...
RiF Posted July 30, 2008 Share Posted July 30, 2008 Our carbon composite does not have carbon near the surface. The surface is not conductive. In addition we recommend bonding much of the panelling with a mastic adhesive. Yes there are still the rivets but if you limit dampness in an aluminium skin or a carbon skin you will reduce corrosion. If it was electrolytic then the problem would be all over. Corrosion is normally limited to the places that remain damp. That is why I always seal the floors and footwells. RiF Driving one of the first Duratec 7, and building CA07BON for Henrietta 😬 😬 😬.for pictures of 7 and carbon andCA07BON Link to comment Share on other sites More sharing options...
FTH Posted July 30, 2008 Share Posted July 30, 2008 If you are building an amphibious Seven, you'll have to "bond".... I see what you did there 😬 Link to comment Share on other sites More sharing options...
Mickrick Posted July 30, 2008 Share Posted July 30, 2008 FTH I didn't think anyone would catch that 😬 But that was an Esprit. The surface is not conductive. In addition we recommend bonding Exactly, but I'll highlight that your "bonding" refers to sealer, rather than electrical conductivity. Never seen a carbon hull with corrosion! 😬 Link to comment Share on other sites More sharing options...
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