Three years late to the thread! But I did some rattle canning yesterday so here goes:
Prep, prep, prep....and just when you think you have it smooth - prep!
For Fiberglass parts - Cracks and repairs - avoid "bondo" car body fillers - they eventually don't adhere and crack. Also any solvent in the bondo that gets entrapped but eventually off gases on hot day and your paint will bubble. You want an epoxy based filler. West 105 thickened with some micro-balloons to a soft peanut butter consistency when filling. It is an all solids resin with no solvents to off gas. Thoroughly cure.
Then 400 grit to knock all the shine off the gelcoat and filler. You want an even matt finish all over. Vacuum with a CLEAN (not the workshop greasy) soft brush to get all dust off.
Then JUST prior to painting - a lint free, clean acetone dampened rag and wipe the part to get the absolute last of the dust off. This will also chemically "tack" the resin and helps ENORMOUSLY with paint adhesion. But you have to let it evaporate off properly too or you get solvent entrapment. A scrap test piece to shoot and check for bubbling before commiting to the part helps.
For Aluminum - Alodine the part. I know Alodine just changed name - this is the stuff you want - follow the directions:
https://www.aircraftspruce.com/catalog/ ... kkey=11999Now to the painting.
Read the can instructions for specifics as it relates to temperature, humidity and overcoating times. If at all possible you want to be on the low humidity end of the range - the paint dries faster, the low temperature end of the range - it doesn't flash off so fast and flows better, and you want
time to do the job. If the can says "overcoat every 25 mins or wait 24 hours between coats" then make sure you do! Impatience has ruined many a long and thorough prep job. Not all colors have the same overcoat time - so check what you are using.
SHAKE the cans the good full two minutes from the rattle ball beginning to move in the can. This gets the solids well mixed through the solvents. But it also gets the gases that pressurize the can full of energy. You can also keep a bucket of warm water handy to have the cans standing by in and you will get even and more consistent sprays. Have a second can ready to go. If you get a spray tip sputters or clogs - drop the can and keep going with the next can that is ready. You really need to maintain the wet edge. If it sputters on your work - don't try and save it. Move on and finish the job, let the paint harden (a week) and then sand it out with 400 grit and reshoot.
For Fibreglass - one of the Rustoleum Gray Filler Primers - it will help take care of pin holes in the gel and lets you visually check you have a really good smooth basis to carry on with. Especially if you did any filling.
For Aluminum - Zinc Chromate Primer. Rustoleum do one in a can - green and usually you have to order it. You can follow with the gray filler primer at this point if you need a color barrier for light colors over the green.
Then put on your color coats. Lightly, at the recommended spray distance. On small parts it is easy to keep a wet edge, on large parts not so easy as you get so far along the part - that on your return the edge has dried. Another reason for painting on the cooler end of the temperature range for the can. Wet edges last longer.
The paint is heavily reduced to get it to spray out the can - so getting deep colors by hanging on a good coat is not going to happen. Multiple coats at the recommended intervals will get you there. But it takes time.
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I dont think rattle cans are cheaper - in fact they are more expensive in the medium to long term. What rattle cans are is convenient and saves you investing capital in a spray gun that might only get used once.
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This checkerboard was done with rattle cans by the builder of my Sonex and is visually very acceptable standing next to it. The design of the pattern also helps break up the visuals and helps overcome any painting imperfections.
The wheel pants were done with the Rustoleum "Metallic" paints. Visually acceptable at 6ft or so. (I did them yesterday - which is what prompted this reply on the thread).