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I don't normally photograph an entire project, but seeing as I had some free sample prepregs from 2 different suppliers I thought I'd turn it into a giggle. They both know I use VTF, and they assured me that their materials would compete. They told me that although the materials are made for autoclave, that I should see promising results OOA. I didnt get my hopes up as Ive tried several before and they all sucked.
I thought I'd turn it into a simple little project to play with these samples. The idea was to take a wooden part (as wood is something I haven't replicated before) that had a simple shape (I didn't have much hope for snything that isnt VTF). Nothing that would take longer than a week. So here it is, from original part to polished carbon copy:
Original wood part:
I tryed using teak oil to seal it, but that didnt work, it just kept sucking the oil, grain was still open.
So I used aluminium tape:
Flanges:
I knew I was gonna have to sand the stripes left by the aluminium tape, so i took the safest route which was to take a mould off the B side, this would in turn become a plug which I could sand down, most likely sanding the gelcoat quite thin. If I sand too far into the gelcoat, I dont have to worry as I will be taking a proper mould off it later. So making of the plug, followed by the mould:
Sanded the lines down with a block, and tried to get rid of negatives on the flanges. You can see why I did it this way, the grey spot there is where I sanded through the gelcoat into the skin coat, theres other spots like it and you can start to see the grey show through the green:
Postcure:
Taking the ali off was a right bitch, and it left a residue which was even harder to take off. Next time, Ill find a better way to do this:
To the prepreg room! Sealed and released:
Thawing and cutting the material:
Layup:
Bagging:
Bake:
Fresh out the oven:
Releasing was this easy:
Oh dear, it seems there was a bit of bridging. Im not surprised. As Iv'e said before, nothing beats VTF. These two photos were sent straight to the sales rep. Hes sending another sample  :
No carbon is scarp though, so I battled on. My plan was to fill the voids, mask them and put black stripes at the ends:
Sanding:
Some peeps on here get paranoid about fillinf the pinholes and voids with dust. Its nothing to worry about, the dust is transparent, and a layer of clear will make it dissapear:
Before the next coat, I'll try something new, branding. I've got a vinyl cutter, plus I made all of my branding myself, so I have the vector files, seemed rude not to do it:
The masking didnt really work, but I think it looks quite cool, even if by accident:
So, more sanding and lacquering, until the pinholes were filled, now go up the grades 400, 600, 800, 1200, 1500, 3000 then compounds coarse then fine:
Finished product on my desk:
Determined not to be beat, I remembered the second sample I had. Along with some new found knowledge gained from this paper:
http://digitool.library.mcgill.ca/webclient/StreamGate?folder_id=0&dvs=1371902526959~725
You could read the whole thing, or I could summarize it to this:
DONT USE BREATHER!
As simple as it is, I did learn something. If youre making a part out of wood, don't use ali tape. Two reasons. First, You have to sand back the gelcoat to get the lines off, and hence making your mould weaker (unless you did the plug-mould method I did. And second, if the original is not sacrificial, youre going to have a hard time taking the ali and its adhesive off very carefully. WD40 got it off without staining it, but I wouldnt place a bet if it was a different wood that was untreated.
I will also be commencing production without breather on the part, just on the mould.
Overall good experience, and the tea tray sold for £150 (for a weeks work!). Hopefully you guys can take something from it too.
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andygtt (15/08/2013)
Love the tea tray, really gives an idea of what's involved with per preg... How large are the biggest parts you make, is it practical to make large car body panels from it? Can you use soric in per preg? Never used soric.. But you can make some big parts at home if you build an oven using simple parts and take your time... I have been using a friends oven that he built and it works perfectly...He uses it for his business so it is very well made and would be quite expensive to copy. But he has it on wheels and can move it round and run it on gas or electricity! Car body parts?? I would say it is not too hard to do them in a Pre-preg. I do bike parts in Pre-preg using VTF 261 for the surface and a material from SHD called LTC250XL. The other material I use is a PRF material called RF 464 which is a good material and is a good alternative to VTF261 if you dont mind some pin holes. To be honest all pre-preg parts need a coat of lacquer anyway to protect them from UV so the cost saving outweighs the little extra work the painter has to do if you send it for lacquer. I am charged £150 for a full bike kit regardless of how good or bad the pinholes may be and the parts look amazing anyway. Just for an idea the kits I make use about 6 Linea meters of 1.25 wide material so the cost if I use the PRF material is about £300 in carbon.. Not sure how big you are thinking but the seat and fuel tank unit is just over 5feet long or about 1.8m long and the fairing is a typical motorcycle fairing size... The seat/tank is a full monocoque and self supporting so has a LOT of carbon in the back up layers to give strength...    These are not small parts.. lol..  I am building a portable oven for some of my smaller parts and have just made a simple PID controller I can connect to a 3Kw fan heater and place in a simple oven. I have used anything from two cardboard boxes inside each other to a large garden wheelie bin (clean one of course).  The controller cost about £40 for the case, PID controller and a 40Amp Solid state relay and 5 thermocouples.. The fan heater was about £30 from eBay and the only other thing I got was a remote meat thermometer to measure the temp of the mould so I have both oven temp controlled and can let the heat soak into the mould and time my cure using the mould temperature but also know the oven will not get too hot if I tried to just take the temp from the part only the oven temp may not be right.
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