Seen some dirt bike parts, which are made from prepreg carbon, with rough weave pattern on the face.
Looks almost as though the pre-preg has been layed over the top of a male mould tool, and then simply put in an oven to cure.
Would this be possible I wonder? Parts in question are very simple curved exhaust guards, and maybe when the prepreg is heated it would conform nicely to these sort of shapes?
no, the prepreg will not conform under heat without something adding it, you must vacuum bag the prepreg, or press it. they may have used the bleeder release film instead of a peelply which left a shiny surface. are sure these parts are prepreg? perhaps they just did a open mold layup, I have seen some rowing shells from germany made this way
Thanks for that info…here is a pic of one of the parts:
http://www.scorpaaustralia.com.au/Photos/500x500_carbonexhaustpipeprotection.JPG
The face is just rough weave pattern, but there is no evidence of any sort of vacuum assistance, or 2 part mould, being used to produce them.
Oh, rough as in the surface texture is the weave.
You won’t get that, along with a shape like that in a solid mold then. Possibly, IF they are actually using prepreg, and that IS a weaved texture, then possibly they are using a silicone mold, and the weave is pushing into the soft rubber, leaving the surface like that. Would be interesting to see more of it.
http://www.scorpaaustralia.com.au/BIKES/Scorpa%20SY250F/SY250F08.jpg
Now THAT is a big assed tire to wack someone over the head with.
I cant see that it can be anything but prepreg, as there doesnt seem to any way of the rough weave pattern actually forming the surface of the finished parts, without any sign of the part having been contact or vacuum moulded?
Maybe parts are made using a modified vac forming process, but substituting prepreg carbon, for sheet of thermoform plastic?
I dont think its prepreg. to me, it looks like they used the tube as a mold then layed up with-out bagging or peel plying, leaving a lean resin content. it looks almost the same as the rowing shells made by BBG, a germany company.I have seen these in person at durham boat company in NH. they are a hybird with honeycomb core, very nicely built. These may have been bag with bleeder no peel, but I have seen other boats that have not bagged and had this look. heres a photo
I get that texture all the time when vacuum bagging with hand layups…
When I use peel ply with bleeder cloth, and get the vaccuum juust right, it turns out like that, very minimal resin, but without dry spots. This is in multi-layer constructions.
When I do the above, but the vaccuum isn’t perfect, or there is some bridging, a thin film of resin remains, but it takes the texture of the bleeder cloth.
This is probably useless info, but I can get that sort of texture, nonetheless…
On these parts there is no evidence at all of any resin on the outer face surface, and will post some pics of a part I have ordered as soon as it arrives.
Why did you pick the part with the smallest picture anyway 
Maybe it was just a reverse molded wet layup and no bag (overlay, but on a mold, not a part)
Or maybe bagged, but with stretchy bag film only, thereby sucking down between the tows.
I get the feeling these parts are being made using some sort of semi automated industrial process.
The company that makes these parts (Scorpa) makes off-road motorcycles, but is also involved in various other areas of industry, so wouldnt think producing simple carbon parts, cheaply and quickly is going to present much of a problem.
how much does that part cost? if cheap enough I would just buy one to figure how there doing it. I still think they are wet laying on a male mold and not peelplying or bagging, but hard to tell
I have seen a couple of these parts close up before, and to me it looks highly unlikely any form of contact moulding has been used.
Of course I may well be completely wrong in this, and will post some high res close up pics as soon as I have a part to photograph.
in the mean time I think I will try my method and see if I can match it.
So…why do people want to reproduce this ugly finish?
These parts are actually very functional, and cosmetic appearance is not that important.
Personally I dont like the finish myself, but would think they are probably being made using a semi automated industrial process…which results in a nice profit margin!
you can still get a perfect smooth finish using an “industrial process”, so whatever finish they have, is done on purpose, or lack of caring what it is.
I would think the main reason for the finish on these parts has to do with making them faster/cheaper, but still being fully functional.
Guy who used to make parts for F1 cars is looking at one of these parts today, and may well know how they were made.
So yeah, I emailed them.
David
Yes, is is pre-preg, and uses a male mould. It has what you describe as a “rough” finish. This is on purpose, and it looks brilliant on the bike. We also supply a final muffler cover that is manufactured the same way. These are made in France by Scorpa FR.
We sell aftermarket “smooth” carbon covers as well, made by a third party in England, but the “rough” variety are more popular.
If you need any more “ideas”, please don’t hesitate to email me, or I could sell you a “sample” if you get serious!
regards
Paul
PAUL ARNOTT I THE HELL TEAM / SCORPA AUSTRALIA I arnoux@thehellteam.com I 11/78 Reserve Road, Artarmon, NSW, 2064, Australia I T: +61.2.9966.5562 M: +61.418.415.129
Interestingly enough been exchanging emails with Paul recently, as a laminator that used to make parts for me, used to do the smooth carbon covers, and I now have the moulds…
Thinking of doing a few more, and making moulds for a couple of additional parts as well. Main problem with the parts made by Scorpa is the cost, and not everyone likes the rough surface finish.