fender with fails - any suggestions?

General Composites Discussions Showcase
#1

Hi!

Here pics of a fender I ordered from a local fiber professional, to my motorbike. There are a lot of “little fails”, like tiny holes in the part. I´m sanding, preparing it to the clear coating. But afraid of this fails will not disappear.

I see others work here at the forum, and the CF part comes ready to install, perfect finish! How come? My local pro friend seems not to be that good I thought! :wink:

Also, I would like to know better the cause of that holes, to improve the work of that professional, because here at my city he is the only one to do this.

Any suggestions in prepping this fender, or about the causes of the fails?

Sorry about my “rusty” english.

Best regards,
Bressan

#2

Your professional friend is not that professional if he makes people pay to purchase an item like that!!! All the pinholes could have been caused by a bag leak, or not vacuum bagging the part at all.
I would get my money back!!! And then start practicing yourself :wink:

#3

That looks like garbage. I can only imagine his molds are not good, and most likely neither is his technique.
How is he making these parts?

#4

I’d say no gel or surface coat.

To dry of a wet lay up.

Hope you didn’t pay much for that!

…maybe sold for repainting with color paints?

#5

it will be fine. clean all the pits out very well with a solvent cleaner so theres no white in them. As long as all the pits are clean it will turn out fine, but you will have to clear it and sand it, clear it again, then sand it… many times to get a good flat finish.

#6

hojo is right,

It’s going to take a lot of work to finish the fender. use a sharp exacto knife to “pop” all the pinholes in the resin and clean them out. Get a container of soapy water and a clean toothbrush. Use it to scrub the white spots out of the pinholes until no white color is remaining in the holes. Now on the pinholes get a toothpick and fill in each pinhole with clear resin… epoxy is probably best, but make sure it is clear epoxy.

It’s going to be tedious work. Once the epoxy cures after say 36-48 hours wet sand the repair work smooth but try not to sand into the carbon fiber weave or it will not look too nice.

Once all sanded down to 320 or 400 wet get out your clean soap and water and give the entire part a good wash. Then use some amonia in clean water on a clean cloth to prewash the fender for clear coat paint. Clear it and your good to go.

#7

I’m making two motorcycle fender molds now. So it’s good and cool you posted this. I’ll wet lay up those fenders next week and show my progress and results. Wish me well because fenders are VERY hard to make right.

Here is a photo of how the mold is progressing… it’s just a cheap mold, not meant for making more than 5 fenders or so.

http://s210.photobucket.com/albums/bb186/Fastrr_photos/Fender%20Molds/?action=view&current=motorcyclefendermolds008.jpg

#8

Thanks for all the replies, folks!

I was looking for someone to do this fender, here in Brazil, about two month of asking and searching. So a friend envolved with car races indicated him.

The guy who has made that fender does fiberglass and carbon fiber parts to stock car racing teams (like the american Nascar races). So, my guess is that maybe he is not familiar with very good looking parts.

I´m talking with him to improve the technique/materials, maybe sometime in the future he can produce much better parts and make a better living. Depends on his efforts.

For me, it lasts a lot clear resin filling and sanding! I have experience with airbrush and house of kolor stuff :wink:

Best Regards!
Bressan

#9

Hi this is my first post here but my ONE experience trying to make a part like this resulted in that finish. Its a layer of clear resin in the mold which is green’d then the carbon is layed and possibly vacuumed. The clear bits are where the resin for the carbon didn’t pull out all the air between the top clear resin coat and the carbon layer. Best not to use a clear coat like this before you lay up the carbon and then clear if after its popped out of the mold. As an amateur this is how i would do it until it worked out how to get it looking right (i have wasted $1000-1500 trying to get it right and still failed)

Im amazed at how some of you get parts to look like the way they do. I have tried to many times even with a pressure intensifier and i still can’t get it to work! I will post some pictures of my molds later when i can hopefully someone can help me.

#10

you know, i suspect the carbon cloth could be at fault too. i used to use a 200grm twill, and it’s weaving was too loose. then i used a 245, and that cloth was tight! used it on my bonnet… 1 layer of polyester clear gelcoat, and 1 day later, i cooked up 0.5kg of epoxy resin, wetted out the whole area, laid the carbon inside, then poured another 0.5kg of resin in the middle of the mold, and brushed it toward the edges, so no air would be trapped. after that i laid the woven fiberglass layers , sometimes soaking up the resin, adding where it was needed. the surface was perfect!

#11

bridging and bubble clusters can be caused by poor vacuum bagging technique. It takes a lot of practice, making sure to pleat the vacuum bag ( youtube search " carbon fiber vacuum infusion Civic hood" also that the bag is air tight…even a pinhole leak can cause air bubbles in/on the laminated part. There are leak detectors you can buy, but most people here I believe just use their ear to listen for leaks… put your ear close to the bag.

Also if you are wet lay up - vacuum bagging… make sure to use either peel ply or perforated release ply and on top of that compltely cover the laminate with a layer of breather. No breather means that area not covered will likely not get sufficient vacuum pressure… also make sure your vacuum line connection at the bag has a lot of breather cloth. You need a steady path flow for air to reach every sq. inch of the laminate.

Are you wet lay up and bagging, or just wet lay up no bagging, or vacuum infusing?

I know with vacuum infusion it is especially critical you have no vacuum leaks. even a tiny pinhole leak can leave the part riddled with air bubbles.

To help solve bridging… use just use 2hg of vacuum or so to massage the laminate stack down tight to the mold surface… use a paddle tool in corners and along edges. Once you have it all massaged down, apply full vacuum. If you have time before the resin kicks… release full vacuum and massage the stack down once again… then re-apply full vacuum.

But on rolled edges you will need some type of mold shaped tool to lay under the vacuum bag and over the release ply/peel ply. This is to evenly apply pressure and force the stack to that curved rolled edge.