Carbon Fiber FS14 LS

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SeaWeed
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Carbon Fiber FS14 LS

Post by SeaWeed »

Hello,

I just purchased the FS14LS plans and am considering a carbon fiber version. I saw a FS18 online in 2016 and it's been stuck in my head ever since. I recently saw Mike's "seaslug" build and decided that is what I would like over the SK14.

I work in R&D for a company that manufactures fabric and epoxy for applications requiring high stiffness and exposure to strong chemicals. We weave or stitch our own fiberglass, basalt, kevlar, and carbon fiber fabric. We also make various epoxy formulations for use up to 700°F. I have no experience in actual vessel design other than looking at making carbon fiber stringers for a large vessel but we were provided the required material properties.

Working in R&D I realize carbon fiber is sometimes a gimmick but I have access to some left overs so I figured it would be worthwhile. This includes hexagonal Jacquard weave, satin carbon/glass weaves, and even UHM carbon fiber which is stiffer and stronger than steel once infused and I will probably use to make a grab bar.

I am very knowledgeable in mechanical properties of composites as I have been doing this for 10 years.

I read previous posts that the issue with carbon fiber for this build is puncture resistance. I also read the hull stiffness is an issue because of the thickness requirements. It was mentioned the flat parts should not be an issue. I see the hull uses biaxial +/-45° glass so I would think the main issue is twisting resistance. We usually make quad axial fabric for boats.

One option I have is that I know a surfboard builder with a CNC so it would be possible to make a jig out of inexpensive expanded foam to lay the hull up on. The possibilities for this mean I could make a hull out of carbon fiber with no foam core if stiffness is an issue. I can also include a foam core of any thickness if I have to for the flexural stiffness. I do not have access to foam core so the less I use the better.

If I could understand more about the stiffness requirements for the hull I can proceed forward on selecting the appropriate lamination schedule for this build without making it heavier than the plywood version.

I look forward to anyone's thoughts.

fallguy1000
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Re: Carbon Fiber FS14 LS

Post by fallguy1000 »

The primary problem with cf is the elongation properties
of it and foam are not a great match. The foam can give, the skin cannot. Same with most of the epoxy resin systems. The cf becomes the failure, from my understanding.

However, cf and plywood are a good match because plywood does not really have elongation issues or benefits, if you will.

So, foam boat still use cf. Sure, but with those misaligned engineering attributes.

As for cf and resin alone; the cf still breaks before it bends ftmp.

But the idea of a cf on ply build I like. It would not be as light, at least in theory, as a foam boat, but in the smaller size it may actually win out. But the schedule would be the only way to assure it.

There are a few tricks to laying up a whole hull in cf. i seem to recall a few issues, but I am too tired to remember now.
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VT_Jeff
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Re: Carbon Fiber FS14 LS

Post by VT_Jeff »

Welcome Seaweed!

I'd personally love to see a full-on CF FS14LS, esp if you're going to feature the fabric. I was thinking that the way to do this would be to make some thin-cored CF panels first and then build the boat from those, same as you would from plywood. I've been thinking about building another driftboat this way since I finished my plywood driftboat.

My wife has a very awesome CF whitewater freestyle kayak. Extremely light and very stiff, perfect for big wave tricks where you don't want a soft boat that absorbs any energy. It's not a boat you want to take down rocky, low-water river-runs, it's purpose-built for playboating in big, deep water. I would see your CF boat similarly: it may have some usage limitations due to the super-light layup, but boats are a collection of compromises to begin with, so no reason any boat has to do it all, and no reason not to build an experimental boat for the fun of it and then see where it's limits are, at least in my opinion.

Seaslug has infected a number of people, including myself, with his amazing FS14LS and FS18 builds. I'd urge you to read through some more build threads on here if you haven't already, there are a lot of incredibly nice builds well-worth gawking at.

Best of luck, staying tuned!

Jeff
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Completed Paul Butler 14' Clark Fork Drifter
Completed Jacques Mertens FS14LS + 10%, Build Thread
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TomW1
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Re: Carbon Fiber FS14 LS

Post by TomW1 »

SeaWeed we would all like to see how a carbon FS14 as you describe would perform. Contact Jacques Merten and he would in all likelihood work up the specs for you. Best way would be call Jeff 772 742 8535, at the bottom is a contact us button which will let you send an email to him.

But wait a day or so he may see this and answer on his own.

Tom
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SeaWeed
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Re: Carbon Fiber FS14 LS

Post by SeaWeed »

Thanks for the feedback guys, I have been and will continue to peruse the build threads here and hopefully have more good replies. Mainly my concern is what issues I need to take into account when using carbon so I can try to fix it. I am guessing it is going to be cracking at the joints.

Elongation of CF is about 1% compared to glass at 2-3% and carbon fiber is 3 times stiffer than glass, but that depends what angles are chosen when you lay it up. 1% doesn't sound like much but you can flex a CF panel quite a bit before it breaks. I have read the FS14LS is very strong to begin with and could use less glass for a lighter version. Perhaps the plywood provides most of the needed structural properties. The large weight savings are probably due to changing from plywood to core. You won't save much weight from going to carbon for such thin laminates.

Frames, decks, and stringers don't seem like an issue. On the hull, using thin core and CF would give more flexibility but not be good for puncture resistance. Perhaps hull can be a glass outside, foam, and a carbon fiber inside. I can also look around to see if we have enough hybrid glass, Innegra, or Kevlar leftovers.

I would like to feature the CF but living in FL I am sure you won't be able to step on it if it's in the sun for any time. So perhaps the vertical surfaces with a UV stable epoxy. Picture below shows what I have for this.

Image

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Re: Carbon Fiber FS14 LS

Post by fallguy1000 »

Personally, I think featuring the hull as cf not worthwhile.

But a helm is cool!
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Browndog
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Re: Carbon Fiber FS14 LS

Post by Browndog »

My flats skiff is an Egret 189 Carbon Kevlar. Although not a boat that I built it may be relevant to note that the Carbon Kevlar version of this boat does trim a bit of weight off compared to the Fiberglass only version. 825 lbs vs. 950 lbs. 13% weight reduction.

I believe the Kevlar component gives it the puncture resistance. The underside of the hatches show visible fabric that looks to be woven with black and yellow strands. Perhaps that might be an option vs. only carbon fiber.

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Evan_Gatehouse
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Re: Carbon Fiber FS14 LS

Post by Evan_Gatehouse »

1. Carbon/foam IS a good match. Tons of high end race boats, race cars etc are built this way. You just design to the elongation of the CF. The foam is stretchy but you're not counting on the stiffness of foam; just acting as the shear web in a sandwich.

2. An all carbon boat (no core) will be heavy because to gain adequate panel stiffness you need thickness. By the time it is thick enough to stop flexing, it is way too strong.

3. So the best bet is carbon/foam sandwich construction with 6 or 10mm foam core. (6 in the sides maybe or non impact areas; 10 elsewhere; thicker at the transom where you mount a motor)

4. Adequate for puncture resistance is 600 gm/m2; Super light/no high heels, and don't drag it over any rocks etc. is 450 gm/m2.

I'm a Naval Architect/Mech. Engineer. I've designed America's Cup yachts and Grand Prix racing sailboats. You never would think of using solid CF except in rare areas (slamming of the hull over big waves at speed). I think for resale value that a carbon/foam is a lot more attractive than carbon/plywood.
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fallguy1000
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Re: Carbon Fiber FS14 LS

Post by fallguy1000 »

fallguy1000 wrote: Fri Mar 12, 2021 7:20 pm Personally, I think featuring the hull as cf not worthwhile.

But a helm is cool!
By featuring, I mean being able to see it. If Evan is advocating for foam/cf, I say go for it. But I'd never bother to try seeing it.

Elongation of Silvertip resin is much higher than the 1% of cf; try 8%.
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cape_fisherman
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Re: Carbon Fiber FS14 LS

Post by cape_fisherman »

Inside- carbon/foam core. Outside- core/aramid/carbon...exact schedule is up to the experts, but this solves some of the issues. The aramid will aid in puncture resistance if you were to experience a catastrophic failure (I have a friend who unfortunately had that proven on one of his sportfishing boats where he incorporates an aramid/glass blend that is buried in the outer schedule...the boat hit something offshore & everything was busted...glass, epoxy, plywood core, inner glass...the only thing that held the water out for them to make it back to port was that tiny bit of aramid...those fibers held).

I say get a lamination schedule worked up & go for it. Laying up the hull in divinycell should be very doable.
Last edited by cape_fisherman on Sat Mar 13, 2021 7:38 pm, edited 2 times in total.

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