Hi there,

I did some resin infusions now and my parts are quite ok. But now I want to make the next step and the part I want to make can be seen from every side, for example a rear wing. How do you make parts which can be lacked and have high gloss from two sides?

Thanks
Sebastian

a rear wing is usually a foam structure wrapped in carbon (and then several laquer coats, sanding and polishing) for one offs, or small numbers. or made in a two piece mold, usually in two halves, and the joined together, for serial production.
for monolithic pieces (or simple sandwich structures), like carbon sheets, two gloss sides can be achieved in ones step via vari, rtm, or prepreg press moulding.

Thanks.

the one step methods seem to be a bit different for a beginner

But what is the difference between vacuum resin infusion (which I used) and VARI? It seems like the same!? Should I skip the peel ply so that the bottom side is not rough and polish it afterwards?

So if you use a two piece mould and put the pieces together, how do you get smooth and round corners where you match the pieces? When I look at my actual products there is a thin and sharp carbon edge. Just sanding and polishing or is there a “Trick“?

VARTM or VARI is quite different to standard infusion, as it uses matched moulds and a cavity with very tightly controlled tolerances. Basically instead of having a vacuum bag, you have another mould. The space between the two moulds is precisely measured to be just enough for the consolidated fabric and resin, so all the compaction on the fabric is delivered by the moulds. The moulds are sealed together, and vacuum is only used to draw the resin in rather than provide any compaction. If you are using a vacuum bag, it is virtually impossible to get a perfect finish on both sides without refinishing the 'B' side.

In the case of a rear wing, oekmont nailed it. Often the preferred method is to carve a solid foam core and then wrap it in carbon, and in this way you can keep the leading and trailing edges smooth, which is extremely important especially for the leading edge. For less critical applications, you can do a simple two piece mould with the split line on the leading and trailing edges, and then bond the skins together. Generally you would then smooth the exterior of the joints as best you can, which usually means a bit of sanding. 

That said, the way I do it personally is to build a mould with a recess in it that let's me move the split line off the leading edge as well as provide a better bonding area. Easy enough to do, but pretty involved and not a quick or cheap way to make moulds. You basically make the top skin as per normal, with barriers on the leading and trailing edges so you don't have mechanical locks. But then rather than just flipping the wing over and making the bottom skin, you make the second part of the mould just a narrow section about 2" from the leading edge. Once cured, you remove that narrow section from the pattern, and then continue with making the entire bottom skin in one piece, including the 2" section that you have already moulded.

Then when it comes to making the part, you put the moulds for the top skin together with the narrow section, so that the leading edge is kept whole. The bottom skin is laid up in one piece as per normal, but you need to place a 2" strip of 2mm (who whatever thickness is appropriate for your desired skin thickness + bond gap) sheet wax along the leading edge. It can be helpful to use the narrow section of mould as a template for the sheet wax.

Now when you demould the parts, you will have a top skin that wraps around the bottom for 2", keeping the leading edge smooth and in one piece (obviously there will be a flash line here that you will need to smooth off). And the bottom piece will have a 2" recess that slides inside the leading edge, giving you 2" of solid bonding area, as well as making the join of the wing on the bottom.

That is probably slightly hard to get your head around from just the description, so I'll post some pictures of a job I did recently. 

So this is a front splitter I made for a Porsche recently



I made the top skin of the mould as per normal, flipped it over and then set up barriers to make the overlap section of the mould.






When that was cured, I removed it without demoulding the top skin



And then the bottom section is laid up as per normal



Now in this case, I wasn't actually trying to keep the leading edge smooth, I just wanted a recessed overlap section for a better bond. So I placed the sheet wax on the overlap section of the mould itself, but for a rear wing I would place the sheet wax on the bottom skin mould.








When finished, you're left with this:








In this case, when I bonded the two skins together, I smoothed off the join using the adhesive that squeezed out of the gap, so it was only visible as a solid black line but was very smooth.

how to getting gloss on all sides really depends on the actual part. If it is a one of rear wing, skin a foam model. If it is something like a carbon Christmas ornament, use bladder techniques. if it is a flat sheet, use ooa prepreg between two thick glass sheets.
some parts can be made with multiple piece moulds, some bonded, a few can be made glossy from several sides in one step.