kempy Posted February 2, 2015 Share Posted February 2, 2015 I've had some replacement aluminum panels made up for my caravan project as over the years the aluminum that was pop riveted onto the steel frame has corroded. Question 1 is, How do I cut the alloy so it's straight?, I'm useless with shears, I have a nibbler but that thing is all over the place. Q2 is, because there's different materials touching, I'm guessing my best bet is to etch prime the alloy and top coat underneath, use aluminum pop rivets? Open to good advice. Here's a pic of what i propose to do. Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted February 3, 2015 Share Posted February 3, 2015 Set up a good sturdy guide clamped to the aluminum. It needs to be smooth and you need to be careful not to dent or scratch the aluminum (iv always covered shit in masking tape that I wanted to protect. Be smart) Then slice off the unwanted material with a skill saw or router. 1 Quote Link to comment Share on other sites More sharing options...
My name is Russell Posted February 3, 2015 Share Posted February 3, 2015 Sounds like you require a plastic separation between the two materials with stainless rivets? to prevent electrolysis. Quote Link to comment Share on other sites More sharing options...
Steelies Posted February 3, 2015 Share Posted February 3, 2015 would not any electrical connection (like a stainless rivet) between the metals allow electrolysis anyways? perhaps mark a straight line and cut it with a grinder and thin disc? if you hit the frame on the inside with a skilly or router you could fuck something. cutting alloy with an abrasive disc is a bit wack, but will work with thin stuff. Quote Link to comment Share on other sites More sharing options...
kempy Posted February 3, 2015 Author Share Posted February 3, 2015 Yea, any rivet will allow electrolysis to a degree. Spoke to an old fella down the road today that was a coach builder, he suggested painting the back of the Ali sheet was good idea and that I dont use SS rivets, stick to Ali ones as SS aggravates the issue of electrolysis further. He advised that I should put an automotive sealant/chassis glue down the drilled holes just to seal them and keep oxygen out, just before the rivet goes in. To cut the sheet he suggested a strip of MDF on the back and the straight edge clamped on the front using a circular saw (or a router). I went and purchased a 185mm ultra fine carbide 60 tooth multi-material saw blade (say that fast..), apparently the negative rake of the teeth makes cutting Ali a lot nicer. That's what I got told... Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted February 3, 2015 Share Posted February 3, 2015 would not any electrical connection (like a stainless rivet) between the metals allow electrolysis anyways? perhaps mark a straight line and cut it with a grinder and thin disc? if you hit the frame on the inside with a skilly or router you could fuck something. cutting alloy with an abrasive disc is a bit wack, but will work with thin stuff. Lol I assumed he would cut it off the caravan Quote Link to comment Share on other sites More sharing options...
kempy Posted February 3, 2015 Author Share Posted February 3, 2015 Nah, I dont like cutting along the side so I'll tip the caravan on its side to make it easier 1 Quote Link to comment Share on other sites More sharing options...
sentra Posted February 3, 2015 Share Posted February 3, 2015 on aluminium boats (the one i have atleast) every interface and fastener is gooped in "tefgel" which is ptfe paste to slow this down. we named it harry monk as its fucking discusting, corrosion probibly just doesnt want to touch it as its 10/10 gross. its been there 5 years now and hasnt changed or harderned or anything. 2 Quote Link to comment Share on other sites More sharing options...
kempy Posted February 5, 2015 Author Share Posted February 5, 2015 Ripped into the caravan today with one of those rotating nozzles on the waterblaster as I figured that I may as well find holes now while all the interior is out, subesquently Iv'e found a couple more. In a couple of spots there are 3-5mm holes in the roof where water has gone through a corroded rivet, underneath there is steel framing and both the aluminium and steel has corroded. Thought so far, and this is where I need advice... I cant get to the corrosion from the inside at all, meaning I need to treat the rust and corrrosion through the hole somehow. Is there product that will neutralise the rust and ali corrosion? I believe I need to dissolve the ali oxidation somehow and then use something to key the Ali so I can coat it, fill it and eventualy put a rubber coating over it. In some areas I can put another layer of Ali sheet underneath but on some I just cant without pulling a significant part of the outer skin off. Open to suggestions... Quote Link to comment Share on other sites More sharing options...
Bangbug Posted February 6, 2015 Share Posted February 6, 2015 Cut & replace would be my suggestion but perhaps not your preference Good to see some love going into an old caravan though 1 Quote Link to comment Share on other sites More sharing options...
kempy Posted February 7, 2015 Author Share Posted February 7, 2015 Bit stuck on this one, it's a curved panel with one hole on it. Ideally I'd like to patch somehow but unsure how to go about it, to me replacing the panel is a major, but admit I have zero panel skills. Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted February 7, 2015 Share Posted February 7, 2015 So that's aluminum? If it were me I'd either have someone weld in a patch OR I'd rivet a patch under or over that hole with a bit of quality chassis adhesive Quote Link to comment Share on other sites More sharing options...
kempy Posted February 7, 2015 Author Share Posted February 7, 2015 Yea it's Aluminum, it appears rusty from the steel underneath and the steel screws that were used. Any good aluminum and steel welders about that want a small job? Also need to replace the draw-bar and a couple of other bits as well. Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted February 7, 2015 Share Posted February 7, 2015 Where are you Quote Link to comment Share on other sites More sharing options...
kempy Posted February 7, 2015 Author Share Posted February 7, 2015 Auckland, but the caravan's in Warkworth. Happy to transport people and offer bribes Quote Link to comment Share on other sites More sharing options...
kempy Posted February 9, 2015 Author Share Posted February 9, 2015 Think I have a solution for that hole. Neutralise the rust on the steel. Clean off the corrosion on the Ali and neutralise. Use an Aluminium metal epoxy to fill holes, machine /sand to shape. Rubber coat entire roof. Paint/seal. Quote Link to comment Share on other sites More sharing options...
kempy Posted February 9, 2015 Author Share Posted February 9, 2015 on aluminium boats (the one i have atleast) every interface and fastener is gooped in "tefgel" which is ptfe paste to slow this down. we named it harry monk as its fucking discusting, corrosion probibly just doesnt want to touch it as its 10/10 gross. its been there 5 years now and hasnt changed or harderned or anything. I think I may have come across that stuff when cleaning the caravan in the weekend, there was a pile of white soft goop in each corner of the floor the size of a tennis ball to seal the holes. it would have been in there for at least 30 years. I'm not quite sure why they did that as it blocked off any possibility of drainage. poor design? have ripped it out and going to make a small drain channel. Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted February 10, 2015 Share Posted February 10, 2015 What that old guys said to you, in your post about 10 back is nearly exactly what we do on aircraft, good quality sealant between dissimilar metals and down the holes to help insulate everything. And sealant anywhere you think moisture might get in as its the moisture that will really alow the electrolysis to happen at a rate that's going to matter 1 Quote Link to comment Share on other sites More sharing options...
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