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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => Project Custom Motobricks => Topic started by: mudcat on December 08, 2016, 07:51:49 PM
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I managed to get replacements for the damaged parts of the fairing of my 1987 K75S. They were a different color so I had them all sofa blasted, or so I thought. It appears that the shop used something more abrasive than soda now I'm not sure how to prepare them for painting. If anyone here has experience repairing or painting I would appreciate some advice on how to salvage these parts. The pictures are of only two parts followed by a closer view of the surface. All the Tupperware has the same appearance.
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It looks like they stripped down to the base material. The bulk molding compound BMW used for the tupperware can be a bit soft once you get past the surface.
I would suggest a high build epoxy primer applied by a pro shop. Shouldn't cost much if you do all the masking and have the parts ready to shoot. That will be the quickest and least labor intensive way to get a usable surface. Several coats followed by sanding with open coat 320 grit should give a paintable surface. This primer is designed to correct surfaces like yours and will sand fairly easily. I have hand sanded 35 foot sailboats primed with this stuff in a few hours, so I would think you could do all your parts in a weekend. Be aware, it will be a dusty job. Wear a dust mask and work outdoors if you can.
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Obviously didn't know what they were doing. What did they say, as to the damage they inflicted, I presume you went off at them. I would probably seek compensation. It looks like they have completely removed the gel coat. I would go with what Gryph advises on repainting. If you want to have a go at them I would probably take it to a professional and ask his advice.
Good luck regards Martin.
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Thanks for the suggestion Gryph, I'll do that. Martin, I didn't know how bad the job was until I took the parts to a body shop where they told me it would cost about $2400 as a rough estimate to prep and paint the parts. Since that was out of my budget I didn't know how I would get them prepared for painting. I'm going to try Gryphon's suggestion, that should cut some of the labor cost.
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I'd first go back to the sand blaster with the estimate, see if you can get it in writing. There is no harm in confronting him over the damage and getting an explanation. At the very very least you should get a refund for the cost of the blasting.
Regards Martin.
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They were a different color so I had them all sofa blasted, or so I thought. It appears that the shop used something more abrasive than soda . . .
The first hitch here might be that they didn't need to be blasted in the first place. They needed to be wet-sanded, primered, filled where necessary, primered some more, sanded some more then painted—at least according to an explanation here by somebody who should know which direction is up.
It seems like you asked for it and you got it. Now if you asked for them to prep the parts for painting and they chose soda blasting, that's a horse of a different color. They screwed up.
If it were my bike, I'd follow Gryph's lead in this.
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#1 These parts have no gel coat. The parts are compression molded like the agitator in a washing machine. They come from the mold with a smooth finish, but not the glossy finish that you get from gel coat in a fiberglass layup.
#2 The proper preparation would have been a wet sanding with 600 wet or dry, followed by repair of the chips and dings with filler, followed by a light colored sanding primer which is wet sanded again with 600 wet or dry.
It would be interesting to see how high the surface is beneath the labels on the tail cowl. That would give an idea of how brutal they were. Asking to have plastic parts blasted with any media is a mistake, and IMO it would be hard to get compensation for something you asked the blasters to do.
The good news here, if there is any to be had, is that sanding the primer is easier than the original paint and in the end will be about the same amount of work(possibly less) as the thorough wet sanding and filling of the chips in the old paint. You will also have a paint job that has no residuals of the previous color and a very well prepared surface.
Take the parts to the paint shop and get an estimate of what it would cost to shoot the epoxy primer for you. Tell them you're in no hurry and you are willing to wait until they are doing another primer job if they can give you a better price. Then see if the blaster will cover some or all of the cost. They should have at least warned you of what you were getting into. I suspect you will have to write this off as a learning experience.
If you do the sanding you will eliminate a large chunk of the labor in this job. When I did my K100RS i did the prep, including masking so all the painter did was the base and clear. Total cost was $500 for a complete RS fairing. Add $150 for the primer, and that would be a good price for the job. Check a couple shops to see who can give you the best price. Another way to get the cost into a reasonable range is to not use a BMW color. Some of them are special three coat finishes that will require you to go to a shop that uses BASF Glasurit paint. That will drastically limit the places you can have do your job. Pick a nice common automobile color and go with that.
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i hate to add to the "piling on" but i have to agree that they should have been sanded not blasted. I've had a little experience with prepping plastics for painting that were fairly pitted and damaged with sandable filler primer. It may take 4 or 5 coats with wet sanding between but elbow grease is free and cans of primer are not too expensive. Make sure to check a test spot with the color paint you are using and clear coat cause some primers and top coats don't play well together. I have had primer bubble and blister when i applied the top coat. If you can match brands of primer and top coat you obviously run less risk.
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Hence the reason for using a professional 2 part epoxy high build primer. You can do multiple coats without sanding in between to build up enough to cover the surface roughness. It is also compatible with the professional 2 part finishing systems that are applied over it.
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MG thanks for the suggestion on how to move forward.