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Old 07-26-2017, 03:36 PM   #1
Kevin Sheets
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Pre Preg Carbon Wrap

Anyone use Pre-preg Carbon Fiber? I know it has to heated. Not sure the laminates will survive the 200F temp.
Thoughts???
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Old 07-26-2017, 03:46 PM   #2
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Re: Pre Preg Carbon Wrap

I would look into the temp tolerances of your adhesive once it has set. I haven't done any CF wrapping, but im sure other that have can tell you if the moisture in the lumber could cause any issues.
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Old 07-27-2017, 09:37 AM   #3
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Re: Pre Preg Carbon Wrap

Pre preg needs to be stored in a freezer, so while it's a boon for the composites industry it's rather impractical for hobbyists.
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Old 07-28-2017, 04:13 AM   #4
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Re: Pre Preg Carbon Wrap

I think a lot of wood would outgas at the high temps needed by prepreg, so that would possibly make it a no-go. If you want to get fancy, then wrap dry and infuse with room temp curing infusion epoxy. And then you could possibly do a post-cure at a higher temp later on.
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Old 07-28-2017, 05:33 AM   #5
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Re: Pre Preg Carbon Wrap

If you want to wrap your gun with Carbon Fiber, by far the easiest and best way is to use braided CF sleeves. They will create a seamless CF cover that contours around the shape of your gun. According to the Carbon Fiber experts, a braided sleeve is also the strongest and most efficient way to add CF to a changing shape (as in a speargun). On areas where the gun is thinner, you will end up with more CF as the sleeve constricts ... and where the diameter is higher ... it will put less CF ... so it adds strength where you need it most. Say you are using a 3K braid ... on areas where the stock thins down (around the trigger) the 3K might become 6K. I think you can get away with adding a CF sleeve without the use of a vacuum bag (although I haven't personally tried it). I think it can be done by just wrapping the sleeve with heat shrink tape and blowing hot air on it with a heat gun or a hair dryer. Obviously much better results can be had with a proper laid up vacuum bagging setup ... but if you don't have that setup and still wanted to CF your gun, that might be a good option.
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Old 07-28-2017, 05:54 AM   #6
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Re: Pre Preg Carbon Wrap

Thanks for the responses. I recently did my first carbon wrap with Soller Composite sleeve.
I used vacuum bag on first layer, had some bridging issues at the ends. Getting a nice tight beat seam at the end (muzzle) prove to be a challenge. The next layer I used the same material but a heat shrink tube. The heatshrink itself was fragile and tore. While adjusting for that the carbon wrap shifted and wrinkled which I didn't catch until afterward.
The gun is finished and with some epoxy sculpt mix I overcame my mistakes.
The learning curve was steep and I looked at pre preg because it is premixed, and the seams are sharp and clean. The storage in a freezer is not a problem. But I have some real concerns about the 212 F cure temp. I doubt the gun laminates would survive that.
Thinking of using a solid blank and pre curing it first to out gas it, then go with the carbon pre preg.
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Old 07-28-2017, 06:12 AM   #7
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Re: Pre Preg Carbon Wrap

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Originally Posted by Kevin Sheets View Post
Thanks for the responses. I recently did my first carbon wrap with Soller Composite sleeve.
I used vacuum bag on first layer, had some bridging issues at the ends. Getting a nice tight beat seam at the end (muzzle) prove to be a challenge. The next layer I used the same material but a heat shrink tube. The heatshrink itself was fragile and tore. While adjusting for that the carbon wrap shifted and wrinkled which I didn't catch until afterward.
The gun is finished and with some epoxy sculpt mix I overcame my mistakes.
The learning curve was steep and I looked at pre preg because it is premixed, and the seams are sharp and clean. The storage in a freezer is not a problem. But I have some real concerns about the 212 F cure temp. I doubt the gun laminates would survive that.
Thinking of using a solid blank and pre curing it first to out gas it, then go with the carbon pre preg.
Everything you do will have a learning curve, and I wouldn't give up with sleeves yet. You should zip tie on end (the muzzle) and have the sleeve setup like an inside out sock ... thus start from the muzzle and slowly unfold the sleeve. Make sure you spray adhesive spray on the ends of sleeves to prevent the strands from unravelling. I use very slow cure epoxy (209) to give me as much time as possible and to keep the epoxy as forgiving as possible. Once you reach the other end you pull a little and make sure everything is draping properly and you zip tie. Using tubed shrink wrap might not be best as the stuff shrinks very little and thus will probably not work well unless the stock has no contours (like a pipe). Shrink wrap tape might work better as you can lay the tape very tight on the stock and it won't have to shrink that much to reach the stock and squeeze. If you insist on using shrink tubes then use different diameter ones that better fit your stock contours and place them accordingly. If you burn the tape in some part as you are heating it ... just lay another layer on that area and heat again. You will have to do some sanding of course (especially on the edges) ... but really not that difficult of a job.

If you want to go the pre-preg route ... you should do your laminates with a high heat epoxy first. Conventional epoxy might soften with high heat. To have a good structural shape you would also have to go over the seam. I actually think it will be much harder to do than just using a sleeve. I have done about a dozen guns with CF sleeves, and like many procedures, there is a learning curve to do it properly ... but even the first one I did was perfectly functional, although aesthetically not as pretty as the last one.
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Old 07-28-2017, 07:16 AM   #8
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Re: Pre Preg Carbon Wrap

Thanks, that's great advice. I won't be using shrink wrap again. I know where I made my mistake on the vacuum bag. I have heard of the inverted sock method before. I think I will try that on the next gun. I like the look and the strength of the carbon fiber.
I have a design in mind for Bluewater that is tapered and thin, with the polyplast band set up. My last gun was a conventional 5/8 band roller with four 3/4 inch x 12 inch long bands on the polyplast. It was smooth and strong when I tested it.
Thanks for the help
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Old 07-29-2017, 02:47 AM   #9
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Re: Pre Preg Carbon Wrap

Majd, what sort of actual vacuum time required with the 209 hardener?
Looking at cheapest/most compact option for bagging sleeve and handle here, something small but with sufficient run time.
Got plenty of pressure here with Bauer and tanks, but no SUCTION…….
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Old 07-29-2017, 04:15 AM   #10
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Re: Pre Preg Carbon Wrap

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Originally Posted by kavachi View Post
Majd, what sort of actual vacuum time required with the 209 hardener?
Looking at cheapest/most compact option for bagging sleeve and handle here, something small but with sufficient run time.
Got plenty of pressure here with Bauer and tanks, but no SUCTION…….
Time is totally dependent on the ambient temperature. If it is cold, I might have to leave the vacuum on overnight ... and maybe a little more. In our hot summers, I just leave it on for about an hour or two. Of course if it is cold then I would just use 206 as it still gives enough time. Lately I have been using epoxy from easycomposites in the UK and their stuff is incredibly liquidy and has even longer cure time than 209. My last few CF wraps, I actually just put the CF sleeve over a dry stock ... makes things much much easier. I apply the epoxy after the sleeve is on ... since it is so liquidy it wets out the CF extremely well. I also don't use the typical vacuum bags any more. I bought some new vacuum bags that are shaped into sleeves ...this avoids the typical hassles of sealing a typical vacuum bag. I just seal one end of the tube ... push the CF wrapped speargun inside and then just seal the other end. I keep that tube longer than I need as this way I can re-use the bag again and again ... I just cut the edge to allow me to remove the gun after cure, and with the added length I can re-seal it and thus re-use it several times. My latest CF wrap protocol is actually extremely easy to do and takes only a few minutes of work. Using the thin epoxy allows the vacuum to really suck up any extra epoxy ... thus keeping additional weight to an absolute minimum. I do keep a peel ply layer that gives the surface a nice rough finish to allow a final coat of epoxy. This also helps as it keeps the need for sanding to an absolute minimum ... which also makes things easier and faster. I always keep sanding CF to an absolute minimum ... and if I have to sand I always use heavy grit like 100 or to file off the zip tied ends I just use a file ... this keeps sanded particles large and thus avoids them floating all over the place. CF dust can be extremely irritating to your skin and you should take precautions against that ... a mask and gloves is a must if you are sanding. I even use a Tyvek suit to make sure no dust gets into my clothes and have a Hepa 13 vacuum cleaner on to suck up as much debris as possible if I work indoors. I did a lot of research regarding the hazards of CF dust, and somehow it seems that it is not hazardous like say asbestos as it is carbon and we are carbon based ... but it can really be irritating to your skin especially if it has curing epoxy on it. What is extremely hazardous is the new nano carbon fiber that is being introduced. That stuff is dramatically stronger than normal CF ... but I will never touch that stuff as it just isn't worth it.

If you don't have a vacuum pump you can get away with a compressor and add a special valve that allows the compressor to suck up vacuum. Of course a compressor is not designed to be left on over night ... so I would just use faster cure epoxy and have a setup which the seal is very good where I can just turn off the vacuum without having the bag leak. With sleeves that is pretty easy to do but with a typical vacuum bag it is more difficult to have a 100% leak proof bag ... so maybe you would need to keep an eye on the bag for a while as you seal of the leaks. Personally I just leave the vacuum pump on as this allows me to forget about it and do something else.

Last edited by spearq8; 07-29-2017 at 04:39 AM.
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Old 07-29-2017, 08:24 AM   #11
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Re: Pre Preg Carbon Wrap

Yo Sheets, I don't think Pre-Preg is the right option for the home builder. It requires a long Auto Enclave to maintain @220 degrees Fahrenheit and pressure, and I'm quite sure if you cut the stock in half and put it in your oven, the missus is going to be unpleasant. Also. A wood core brought up to 220 is just not the best idea for our purposes (Straight as an Arrow). A wooden stock brought up to 220 is a good way to make a bannana. To say nothing about offgassing.

I've seen some amazing AutoEnclaves locally. Rhode Island has a long history of Boat and Mast Building. I saw an AutoEnclave 160' long the other day which was pretty impressive.. With Prepreg, the idea is to Mould your shape with pure inert composites. Then to Cure that shape in the Auto Enclave under Heat and Pressure. It's a completely different process then what you are talking about.

What you want to do is Resin Infusion. Anyways. In shop all day as usual.. if you're in neighborhood. NorEaster next few days.
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Old 07-29-2017, 09:21 AM   #12
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Re: Pre Preg Carbon Wrap

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Originally Posted by Behslayer View Post
Yo Sheets, I don't think Pre-Preg is the right option for the home builder. It requires a long Auto Enclave to maintain @220 degrees Fahrenheit and pressure, and I'm quite sure if you cut the stock in half and put it in your oven, the missus is going to be unpleasant. Also. A wood core brought up to 220 is just not the best idea for our purposes (Straight as an Arrow). A wooden stock brought up to 220 is a good way to make a bannana. To say nothing about offgassing.

I've seen some amazing AutoEnclaves locally. Rhode Island has a long history of Boat and Mast Building. I saw an AutoEnclave 160' long the other day which was pretty impressive.. With Prepreg, the idea is to Mould your shape with pure inert composites. Then to Cure that shape in the Auto Enclave under Heat and Pressure. It's a completely different process then what you are talking about.

What you want to do is Resin Infusion. Anyways. In shop all day as usual.. if you're in neighborhood. NorEaster next few days.
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Old 07-30-2017, 02:00 AM   #13
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Re: Pre Preg Carbon Wrap

- For turning pressure into vacuum, look into venturi pumps or just build a cheap vacuum pump yourself. Look up Joe Woodworker vacuum pump for inspiration. Not difficult, and with a good, cheapo pump from Ebay, it won't be very expensive either. I built a small one myself with pressure switch and reservoir.

- You can get OOA (Out Of Autoclave) pregpreg, where an autoclave is not required. But I would, as mentioned earlier, look into infusion. You get some nice benefits, dry lay up and as long a working time as you want to arrange the plies. You can debulk (pulling vacuum on the dry layers of CF to help them set properly) in between layups and when you are all happy with the layup, you bag and infuse. Less messy, more control, too.

Last edited by Diving Gecko; 07-30-2017 at 02:08 AM.
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Old 07-30-2017, 06:11 AM   #14
Kevin Sheets
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Re: Pre Preg Carbon Wrap

Thanks all for the great advice. It was "Out of Autoclave", I was looking at. Very good video on You Tube by Easy Composites from U.K. showing Pre-Preg techniques.
Jon, if I get a chance I may drop by later today. It would be a sin to wrap one of your guns. They are at their pinnacle in design and appearance.
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Old 07-30-2017, 06:26 AM   #15
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Re: Pre Preg Carbon Wrap

Spearq8, if you don't mind me asking, where did you get the vacuum tubes you are referring to. That's a great idea!
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