How tight a corner can be made using wet layup techniques?

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#1

Just hoping to gain some input from people who have more experience than myself with this.

I’m just finishing up a few plugs and wondering how tight of a corner, or how sharp an edge it’s possible to make using wet layup? First up let’s say it’s just a straight up wet lay job, no sandwich moulds etc.

For example this one with the edges running along the top:


Fender Plug - Complete by mugget, on Flickr

I’ve sanded the tops of the edges down a little bit, but don’t want to paint the plug and make the mould just to find that I get bridging problems etc. when I go to make the first part. What kind of guideline would you use if you were making a part like this yourself?

As another example this part has a fairly crisp edge on the top that has been formed by working the top and sides.


under seat gap by mugget, on Flickr

I’ve since rounded it off a bit, but would like to know if there’s any way I could have left that edge?

And out of curiosity, with something like a sandwich mould with a 2nd mould part applied to the back of the job after layup, would that allow for a much sharper edge? Is it as simple as just holding down the area so it doesn’t bridge, or is there more to it?

Even better if anyone can share some photos showing the type of edges/corners/contours that you’ve been able to make using wet layup.

Cheers for any info!

#2

Just a couple of mine… The frame protectors either have a detail on them or need a nice sharp edge on them…

The engine case protectors have tight corners all over them too…

I think you would be fine…

#3

Wow… I had seen those pics before but never noticed the bracket looking detail on the lower side of the frame protector - crazy! And the case protectors look like a gnarly layup also!

Those parts of yours were wet layup and then vacuum bagged, right? I know that vacuum bagging is no solution for bridging, or at least it shouldn’t be, but do you think you’d be able to make the same parts without bagging?? I dunno… part of me still has a hard time believing!

Actually now I’m curious how you go about laying the CF down… do you use a surface layer of resin, and let that tack off? Do you have any trick for laying the CF down, because that would stick as soon as it touched down and would ruin the weave if you tried to move it?

#4

I could do them without a bag… Bagging does almost zero for bridging if the gel coat has gone to tack… The carbon sticks and will not move… I do let the gel coat go off almost completely so it has little or no tack. Putting the carbon down is slow but if you get it down fully then you should have good parts… I use a vacuum bag to try and keep weight down a little and squeeze out exess resin. You would be surprised how much exess resin there can be even if the last layer of glass or carbon is put down dry!

I would suggest you get some of the cheapest hair spray you can… The hair spray breaks down when the resin hits it… So put the carbon down on a gel coat that has no tack then lightly spray the carbon with hair spray… It only needs a light film of hair spray and it will stick to the gel enough to hold it there as you work down the rest of the carbon… Work it into every place you can and then lay up as normal…

I would suggest getting a cheap ebay vacuum pump and some consumables… It helps make a more consistant part. A 2 CFM pump is enough… I got one from a German ebay shop for less than half of the price Easy Composites sell theirs for and it actually pulls a better vacuum too!

#5

Hair spray? Gonna have to try this one. :slight_smile:

#6

What resin do you use? I think you mentioned a vinylester previously? Or polyester… I can’t remember…

Are you sure that the hair spray breaks down in the resin? The only reason I ask is because I have used hair spray before - but as a mould release! Works pretty darn good as a release as well, so I’d be kinda wary of using it on gel coat. :eek:

Cheers for the tip on the eBay pump, I will look into that (eventually!)

#7

Yep… Hairspray sprayed very lightly is fine but it is on the back of the carbon. I was shown how to use hairspray to pre-form carbon for complex shapes too… The guy who showed me has been doing this for 30 years and he sprayed some carbon so it would stay in the shape and was as stiff as wire. I have been doing it for a while and no problems and you can feel the carbon soften again slightly.

#8

Hmmm… very interesting… if you have no adhesion/delamination problems then I guess that’s that! I will have to try this out if I ever get caught on a really tricky part. Thanks for the suggestion and clarification!

#9

How are the KTM parts going? Any progress to talk about?

#10

Hi Fastrr,

Unfortunately there’s not much new progress to report on the KTM bodywork. I have been super-busy since last July setting up a new business (another big first for me, I guess 2013 was the year for all the “firsts”!).

I am hoping to get back to some good progress really soon, I have all the main plugs primed and just have to flat them and spray the topcoat. Then I’ll be making molds and it’s all downhill from there… I hope!

I will be posting the very minute I have news to my WIP thread here: Work In Progress: Custom Motorcycle (Supermoto) Bodywork(in case you want to subscribe to the thread).

Here’s some of the latest pics from that thread to tide you over:

And the rear side panels were the first ones I sprayed the topcoat on, just because their shape is much easier to fix defects. And I do need to sand back the clear a little bit, want it to be smooth as glass (easy fix). Pretty confident to spray the rest now since I’ve done a fair bit of repair work and resprayed some sections of a van, all good practice.

Wow, looking at all this stuff has started to get me excited to get back to it - there may be an update sooner rather than later!

#11

What kind of hair spray? I’m not convinced… Doesn’t Sper77 do the same thing? And is used by more people?

#12

That fender looks familiar…here’s one of mine. This is what you’ve got to look forward to:D

#13

Don’t use hairspray! We tested it and the layers delaminated very easy. You can use it better as PVA than Sprayadhesive.

#14

Very nice r0bsk1! Just what I need to get me amped to make some progress!

#15

DDCompound - what resins did you test the hairspray with?

That’s why I was so surprised to hear about it being used directly on the fabric. If I’m using polyester resin I use hairspray as a mould release, if I’m doing a quick splash mould etc., or if it’s a part I think might be difficult or for a bit of extra peace of mind on the initial layup. If it’s a really quick part, I have used hair spray as the only mould release!

I tested it as a release with epoxy resin (wax with hair spray dusted on top) and it seemed to work just the same. But I haven’t really used epoxy apart from that small test.