Hello

I should think that if it is that close you could glue it on to keep it in place.

You want a glue that is easily removed. I might suggest a silicone product that is called seal and peel.It comes in a caulking tube and is used to temporarily seal windows for the winter season. It is crystal clear. Once cured you just grab a corner and it comes off totally clean in one pull.

I was going to use it on my airplane canopy and wanted to be sure it would come off easily once it weathered.

Fred  

Muhahah

Well, i think people only see carbon fiber as 2*2 twill leave  

I know that twill will drape easier on curves and corners than plain weave. I know half spheres can be easily done with it.

There is also the Eight Harness Satin which is known as quite pliable too, but I never used it so i could not compare it to 2*2 twill. And people will think its not carbon haha.

 



 


    A $1000 electronic device will always protect a 10 cents fuse

Thanks Joe

I'm actually quite hopeful about using room temp home made prepreg as opposed to remaking moulds. I think that if I cut the corners of the cloth as close as possible to the mould then it might be perfect. Now that's ironic, I have to cut corners for better quality.

Unfortunately I have run out of cloth though. My friend gave me some strange 1x1 super heavy and stiff cloth but using it wouldn't help me get the 2x2 twill perfect. It'll be next week now before I can try again with the good stuff.

Am I right in saying that twill is the good stuff? That's what people want to see isn't it?

Hey, Adam.

Its great to see you did not give up. i think development is a very interesting part of the composite world.

Keep us updated !!

 



 


    A $1000 electronic device will always protect a 10 cents fuse

Hi Maverick

Paul fron EC said the same thing, Then I can rely on the thermal expansion for the compression. Then I'd need a split mould as the cover curves back on itself. I can't imagine making a spilt mould that would be as reusable as the silicone. Also I'd have to make a different size plug for every temperature prepreg. I can just see myself spending hundreds of dollars making a new plug for a 150 degree prepreg only to have 150 degree prepreg being replaced by 120 degree prepreg.

In regards to a glossier finish, I've been clear coating them with UV protective car clear. I have read that epoxy goes yellow without it. The one in the photo hadn't got to that stage yet.

Thanks for the interest though, it's encouraging. I have come so close to scrapping this whole idea so many times.

Sounds like you want to go for a rigid outer tool, this should give to a flatter gloss finish on the outside, and it shouldn't expand anything like as much as the silicone so I'd say that would fix your size problems... when you get them sorted you can put me down for one!

Thermal expansion update...

I put an iphone sized plug in the fridge at 3 celcius. I left it for a bit and then shoved it in the oven at 120 celcius for 10 mins. The results are very bad for my existing moulds...

114.7mm @ 3 degrees

116.2mm @ 120 degrees

1.3% expansion for the size of an iphone. That means my covers would fall straight off the phone. I just died a little inside.

Hi everyone, this post is an information sharing exercise rather than a question. I've been asked for details about my experience with using silicone for moulds.

I have used two types of silicone so far and they have both been "Wacker Chemie" products. Both were platinum cured and one was firmer than the other. Model numbers were 4644 and 4670.

It's a part A plus part B scenario just like resin but a lot thicker. I think you can get one part stuff but it's not as good. I just want to clarify that those two model numbers weren't the part A and part B numbers. Each of those models come with their own part A and part B.

It takes about 24 hours to cure and when it does, it's just like a block of rubber. It has excellent detail reproduction too. Even the logo from the back of my iPhone could be seen in the silicone and you can't even feel the logo on the phone.

It is very strong stuff and extremely resilient to epoxy. I've used my moulds about 20 times so far without any degradation.

It is very heat resistant, even to the point where you can cast "low melt alloys" in it. I'm about to find out how much thermal expansion it has too so watch this space.

It is fairly expensive and so you wouldn't want to make anything too big with it. Just google RTV2 for a local supplier and prices.

It doesn't need any release agent. That's one of my favourite things about it. In the same breath though, you can't really stick wet cloth to it and so your product really needs to be made with one small piece of carbon. Or all the bits need gravity to keep them in place.

Here's a pic of my mould but please don't laugh at all the air bubbles, I don't have access to a vacuum chamber...



Most of those air bubbles have actually floated away from the good surface by the way. When I say most I really mean most, there might only be a handful still touching the good side. Resin does get into them but when you demould your carbon those resin bubbles just pick off as if they were never there.

Here is a pic of what came out of the mould... This pic, by the way, is of the cover I just made with the homemade prepreg. That's for those of you following the "kitchen oven" thread...



Silicone seems to work for me as I'm working with small flat shapes but it won't work for everyone.

Lastly, I would like to stress that I'm NOT an expert and everything you just read might be rubbish.