SV Carbon Tank project for Zoran

[tygaboy]

New patterns for this tank

Even though I was able to use the patterns from my SV/MV tank to make the mold, we want the final product to look as nice as possible. The SV/MV tank underside is 'close' to this shape but we really need specific patterns for each part. So I started with the top. This is a much easier shape to deal with, compared to the top - see the pattern making we did for the top earlier in this thread for details about that.
Newspaper works just fine. Cover as much of the surface as possible while checking fit and taking the draping issue into account.

 

[tygaboy]

Fit, fit, cut, cut, fit fit, trim, relief cut, fit and...
One set of SV underside tank patterns.

Prep that mold with wax and PVA, cut the carbon to shape and I'm ready to lay up and bag!

 

[tygaboy]

Chris,
this thead gave me the inspiration to try this stuff myself. I've got a question for you. What brand scratch filling primer are you using? I've got some duplicolor primer but it doesn't seem to hold up very well to heat generated by the epoxy.
Thanks,
Brian

The stuff I'm using is a rattle can brand called "Tempo". I think any scratch-filling primer will work.
I'm getting a spray gun and am going to give FeatherFill a try. It's supposed to be twice as thick so should be a time saver.

 

[tygaboy]

BAGGED!

Found a bit of time this afternoon and thought I'd lay up and vacuum bag the production underside part.
Let me start by introducing you to my vacuum pump rig. It's just a little Gast model I got off e-bay for about $100. It pulls around 24 inches of mercury so less than 1 atmosphere but plenty for what we're up to here.
The set up consists of the pump, specific vacuum line (regular plastic line would collapse under the vacuum), a shut off valve, a vacuum gauge and a through-the-bag type connector.
You can see in the pic, I've cut a small X in the top of the bag and fitted the connector to it.
The idea is that once the part is under full vacuum, I close the valve and shut off the pump. It is certainly not the case of letting the pump run during the cure cycle - it wouldn't last as this one is not designed for continuous duty.

 

[tygaboy]

I won't take you through the lay up process. It's the same as what I've done with the 'glass - use the patterns to cut the carbon, lay it all out so it's easy to work with and go to town.
I did learn one new thing - this is the first time I've worked with the 2x2 twill on irregular shapes and it does NOT like to stay together. It pulls apart at the edges and moves around like mad compared to the plain weave. I hadn't noticed that on the exhaust hangers and other small parts I've used it for but man, it was hard to keep it looking nice at the edges.
So if you sharp eyed readers notice, the carbon you see here is the plain weave. Yep, I realized the twill was going to be a bitch so I only used it on the outside layer - the one that will be visible when the tank is assembled. Just like the Wizard said - "Pay no attention to the man behind the curtain..!"
But I can sure see why the finishes the pros get with the prepreg is so nice. I hope to some day get my hands on some prepreg. Mmmmmm....prepreg...
Sorry, back to reality. I used three layers of carbon and two of the heavier weight fiberglass. No kevlar as it's not needed here.
And here we are, all layed up and ready to bag.

 

[tygaboy]

Once the layup is complete, I fit the peel ply over the laminate as neatly as possible then wrap it in the breather. Then it gets put in the vacuum bag. I have already layed in the final strip of sealant tape along the mouth of the bag so once everything is inside, I seal up the bag and turn on the pump.
You may not have noticed but the pump-to-bag connector can't just go any old place, it has to have an air path to the breather. So I wad up some extra breather and lay it under the connector and up onto the breather that's wrapped around the part. Again, a simple little trick that keeps the connector off the part and eliminates the possibility that the part picks up the imprint of the connector...don't laugh, I have a Ducati exhaust heat shield with a nice big connector-looking imprint in the finish...
When the vacuum starts to pull and the bag starts to clamp the part, the fun really begins - trying to be sure the bag is fitting everywhere it needs to fit while it's starting to clamp down and quickly become harder and harder to adjust. Remember, it's important to ensure there are no bridges in the vacuum bag and that the breather and peel ply are staying where I want them to be.
If I see something I don't like, I shut down the pump and bleed air in to release the bag so I can make the needed adjustments. It usually takes me a couple tries to get things where I want them. Once I do, I let the pump pull until it maxes out. Start to finish, to get all the air out, it only takes about a minute.

 

[tygaboy]

And here's the other side. Look closely - see those slightly darker spots all over the side and top? The excess epoxy is being squeezed out of out laminate, through the peel ply and into the breather. The vacuum is doing just what we want. We're going to get a lighter, stronger part than we would if we just did the wet lay up and no vacuum. Lighter AND stronger. Cool, huh?
Now to let it cure. With a bit of luck, we'll have the first half of our tank ready to go tomorrow afternoon! So far, so good. Now it's on to the top and back to the Bondo.
Time invested to date, about 27 hours.

 

[lizard]

Hey Chris, how come you're not using kevlar on this project?

 

[tygaboy]

Hey Chris, how come you're not using kevlar on this project?

Ah, but I am. The entire top of the tank will have a layer of kevlar. I'm skipping it here, on the underside, as the odds of the underside taking an impact are (hopefully!) zero.

 

[tygaboy]

Production Underside is ALIVE!

I got everything all nice and hot and it cured enough to pull the part. I had a couple problems with the bag that I figured would bugger the part so I decided to pull it out, figuring I could always make another.
I suppose this is kind of an excuse or at least an indication of my approach but it usually takes me two tries to get the result I want from a process. And I haven't bagged a complex part since I did my SV/MV tank about two years back. So I'm re-remembering those "oh, yeah...that was a problem last time..." learnings. Anyway...
Here's the peel ply and the breather being pulled off. And it's not like things just fall off. Remember, that breather has some epoxy in it and the peel ply, while it won't bond to the laminate, still grips it such that I have to apply some serious force to pull it off. Here, I've run a blade down a few sections and am peeling it all off a strip at a time.

 

[tygaboy]

The part is still on the mold but now it's been freed from the peel ply and the breather.
Here you can see one of the problems I had:
The breather got wrapped under the peel ply on the right and left side flanges. Not good, but since I have plenty of room, I hope to be able to trim those areas such that we'll be OK. I don't need that much area to get a strong top-to-underside bond. Let's see how it looks once it's out of the mold and trimmed. Fingers crossed...

 

[tygaboy]

I did a little warming with the space heater. The sun was out so I took advantage of that to do a bit of solar curing, too. Just laying it in the sun yields surprising results. The part gets very warm and speeds the cure along nicely.
Normally, I'd wait another day before pulling the part but again, since I saw there were a couple flaws, I figured I'd pull it now and if it wasn't what I wanted, I'd call it a 'learning part' and start over. But it's cured enough that if the flaws are liveable or can be eliminated, it'll work just fine as a production part.

 

[tygaboy]

OK, here we go...
I've trimmed and sanded the problem areas and guess what?
We're Good To GO! It's going to be just fine.
(Huge sigh of relief...)
Let's start with the 'inside' of the part.

 

[tygaboy]

And finally, after all this, here's the money shot:
One carbon fiber SV tank underside production part!

Can I get a 'Hallelujah', people?!?!?

Sexy, wouldn't you say? And it weighs about as much as a bag of potato chips.
OK, you can see there are a couple stray fibers but like I said, that twill weave is a bitch. Pretty as it is, I think I'm going back to plain weave, at least for the complex stuff. I'd rather have a higher quality part.
So a bit of function over form seems OK to me. Plus it's not like plain weave is ugly or anything.

 

[drizz]

 

[tygaboy]

And here, I've painted on a coat of the tank sealer. I like this as an insurance policy.
I keep it away from the flange as that's the part that will bond to the top part of the tank and I want a carbon-to-carbon bond.
This part can be set aside until final assembly. On to the top...

 

[xtasie99]

Did you use any sort of gelcoat? My vacuum parts always seem to have pinholes in them, even against something like a polished/waxed metal sheet. And the real clear gelcoats I've seen are too expensive for my taste.

Also, you are just brushing on the pva, right? The only time I brushed it on, it turned out complete crap and I've sprayed ever since. But yours turns out very well.

 

[tygaboy]

Did you use any sort of gelcoat?
Also, you are just brushing on the pva, right? The only time I brushed it on, it turned out complete crap and I've sprayed ever since. But yours turns out very well.

No gelcoat and I did get some pin holes with the twill weave. But the finish on my plain weave stuff comes out great. Essentially, the first layer of epoxy is the gel coat. If I want to ensure no pin holes, I just let the first coat of epoxy get uber tacky then lay in the first layer of carbon. That usually results in a perfect surface.
As to the PVA, I just use a blue shop paper towel to wipe it on. I've never had any problems with that approach.

 

[drizz]

No gelcoat and I did get some pin holes with the twill weave. But the finish on my plain weave stuff comes out great. Essentially, the first layer of epoxy is the gel coat. If I want to ensure no pin holes, I just let the first coat of epoxy get uber tacky then lay in the first layer of carbon. That usually results in a perfect surface.
As to the PVA, I just use a blue shop paper towel to wipe it on. I've never had any problems with that approach.

Any movement on the top part yet? Or is that on hold for a bit?

 

[tygaboy]

Any movement on the top part yet? Or is that on hold for a bit?

Back to sanding, shaping, etc, on the top. Also taking some time to make my SV fairing parts.
And since I've already posted the process for how I make splitter plates and top molds, I figured no one would find that very interesting. Thought I'd just post the new stuff as I get to it. I was going to throw in 'progress' pics but go light on that until something new was happening.
Let me know if you want the full play by play. - I'd be happy to document the whole thing...