under what conditions will a wet layup of carbon react with aluminium..?
in the idear of rapping a alli boom with carbom ti stiffen it .. who cares how much it will weight
Nick
Resins will not laminate to aluminium well. It will stick, but the strength of the bond is much less than say epoxy/carbon laminate cured and then more epoxy/carbon laminated on top of it. I think it is the oxide layer that stuffs it.
Aluminium needs a good sanding followed by treating with an etching solution.
From memory it is sulfuric acid, potassium chromate or dichromate and some other stuff - possibly expensive to go and buy all the stuff you need just to make a little bit.
I have it somewhere in the Ciba-Geigy data sheets I have for Araldite resins but I'd never find it (just moved house) so perhaps Google and / or the Ciba-Geigy & West Systems websites.
maybe that kind of searching may identify an off the shelf etching solution for you?
A point maybe not considered besides all the above is the increase in boom diameter
A single wrap will add ~1mm to the diameter.
Go the carbon, the boom will only be as strong as it's weakest part which will then be the boom head
^ a lot of those 2 part expanding foams absorb and trap water in them.....
If you have a compressor and you want to get tricky an inflated bladder would be a better option.
have you priced carbon and epoxy lately ??
the stuff is as dear as poison ,also as you mentioned you will be adding a heap of weight even though your using carbon and epoxy then you got the problem of the epoxy keying to the alloy (should be ok if you rough it up) then you got to replace the grip!!
I'd consider the option below............
http://cgi.ebay.com.au/High-Quality-Windsurfing-Carbon-Wave-boom-140-190-/260534315864?cmd=ViewItem&pt=AU_Sport_Surfing&hash=item3ca90e2b58
cgi.ebay.com.au/High-Quality-Windsurfing-Carbon-Wave-boom-140-200-used-/260549159368?cmd=ViewItem&pt=AU_Sport_Surfing&hash=item3ca9f0a9c8
could you get a carbon boom and add some more carbon?
would the weight increase be that much?
OK. this is my industry.
Don't waste your time and money.
You can abrade the surface with the resin, so instead of using water to sand you use resin. ie no oxidation ( use gloves). You can get epoxies that are formulated to bond to metal but they are typicaly adhesives rather than laminating resins. Yes glass veil to insulate for galvanic reaction. But honestly you are just wasting your time. Any core you try to put inside the ali tube will have no effect whatsoever. If you're not carefull the laminate will be full of voids with high resin content.
You can't just put together material with different modulii. Putting ali and carbon together is similar to putting steel and bungy together as an example......attach a piece of bungy to a strip of steel, now pull some tension on it...which one's doing the work?
It will stiffen the boom to an extent, but the advantage you'll get of laminating in the back shed just won't do the carbon justice.
I could go on and on but you're better of buying a carbon boom.
I thought about doing it but never got around to it. If I did I'd use a 28 mm boom, sand it with 80 grit, wipe clean with acetone and give it a clear coat of epoxy. Cut a 300 mm strip of 6 oz carbon the length of th boom arm with 10 mm masking tape half on the long edge.
Pre wet the carbon on a bench on thin plastic sheet but only up to the masking tape. Lift the whole sheet up and stick edge of tape to the boom arm and start wraping it firmly around it peeling the plastic backing sheet off as you go and rolling it. Once done and on tight I'd start wraping it with electrical tape from the middle to the ends, with this style each layer will only be 0.5 mm thick with a high carbon to resin ratio and wouldn't be much room for water to get in though some sika around any openings before glassing would make sure of it.
