787 Rollout
- Thread starter chromer
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RJD Wannabe
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And, it there a real use for kevlar/aramid in boat projects??
I am planning on a 22 angler down the road and plan on extensive customization of the interior. Is there any advantage to using carbon fiber vs fiberglass??
I am planning on a 22 angler down the road and plan on extensive customization of the interior. Is there any advantage to using carbon fiber vs fiberglass??
dogon dory
New member
Sorry, Folks - Post Deleted By Author
RJD Wannabe
New member
Agreed about plywood, but if you want to glass something, or need light wieght and strength, is there any advantage to kevlar??
Working in highly exotic materials like kevlar, carbon fiber, and boron fiber is extremely expensive and usually difficult. This construction technique is used where weight saving and strength are so overwhelmingly important to justify the extreme expense.
The techniques often require two-part molds, autoclaving (heating in an oven), or vacuum bagging.
Sometimes the materials are pre-preg, which means the fibers are already imbedded in soft epoxy resin, which then must be heated to get the final bonding and curing, all while locked between the two parts of a metal mold. The costs of making these two-part metal molds makes the use of these fibers prohibitive in many projects.
While some use of these fibers can be imbedded within conventional fiberglass reinforced plastic projects like a boat, the vast majority require skills and techniques that are beyond practical use by most boatbuilders, especially considering the cost.
I have seen a factory that builds carbon fiber bicycles and another that builds carbon fiber glider airplanes.
This is not back-yard hobbyist stuff, but more like cost-unlimited military projects. It's a case of being more like NASA and less like Bayliner.
You can, however, make things out of pre-formed carbon-fiber components, like carbon-fiber tubes, making them into booms, spinnaker poles, tillers, and tiller extensions for sailboats.
One-half of mold for carbon fiber bike frame.
Finished product.
Carbon fiber canard pusher high-tech airplane.
1) McLaren F1 Supercar with carbon fiber body.~$300k. 2)Carbon fiber auto racing seat, $1750. 3)Carbon fiber corset, made from a mold taken from your body, it sez....I'm hoping it's for a jousting tournament with your horse! Only $250! Funny anyway! Madonna eat your heart out!
Joe. :teeth
The techniques often require two-part molds, autoclaving (heating in an oven), or vacuum bagging.
Sometimes the materials are pre-preg, which means the fibers are already imbedded in soft epoxy resin, which then must be heated to get the final bonding and curing, all while locked between the two parts of a metal mold. The costs of making these two-part metal molds makes the use of these fibers prohibitive in many projects.
While some use of these fibers can be imbedded within conventional fiberglass reinforced plastic projects like a boat, the vast majority require skills and techniques that are beyond practical use by most boatbuilders, especially considering the cost.
I have seen a factory that builds carbon fiber bicycles and another that builds carbon fiber glider airplanes.
This is not back-yard hobbyist stuff, but more like cost-unlimited military projects. It's a case of being more like NASA and less like Bayliner.
You can, however, make things out of pre-formed carbon-fiber components, like carbon-fiber tubes, making them into booms, spinnaker poles, tillers, and tiller extensions for sailboats.
One-half of mold for carbon fiber bike frame.
Finished product.
Carbon fiber canard pusher high-tech airplane.
1) McLaren F1 Supercar with carbon fiber body.~$300k. 2)Carbon fiber auto racing seat, $1750. 3)Carbon fiber corset, made from a mold taken from your body, it sez....I'm hoping it's for a jousting tournament with your horse! Only $250! Funny anyway! Madonna eat your heart out!
Joe. :teeth
RJD Wannabe
New member
Thanks, looks like I'll stick with glass when needed
Kevlacat makes cats using carbon fiber. They are very light and fuel efficient. Unfortunately the ones made here in the US have had a lot of construction problems. They have been making them in Australia for many years and are known for their high quality there. You can check out their website here.
www.kevlacat.com.au
Bill
www.kevlacat.com.au
Bill
I would not see any use for carbon fiber or Kevlar in a C Dory modification. Agree that Plywood and epoxy/glass, or some core material/epoxy glass is the best modification material.
Kelvacats only have two layers of unidirectional Kevlar material. the majority of the boat is conventional fiberglass constuction, including some balsa core--and other cored materials. I am not sure of carbon fiber use in Kelvacats. Carbon fiber is actuall heavier than glass fibers, but it is much stiffer and stronger, so you get a greater strength to weight ratio.
There are a number of high speed racing power boats which use kevlar, as well as kayaks etc. There is a definate strength/weight advantage there.
Althought the large hulls (such as the America's cup, around the world Volvo racers etc) use large amounts of carbon fiber, and autoclaves etc.
There are a number of custom one off builders who epoxy carbon fiber into and onto a laminate to increase stiffness and strength. Vacuum baging is within the realm of all backyard builders and is used extensively in light weight boats. Vacuum bagging gives better lamination of fibers and infusion of resins into the fibers, keeping the weight down. I have a friend who used both materials to build a 32 foot cat (he used a single mold for both hulls, the rest of the boat was built up. Divinycell was used as core material. The deck and cabin house were all vacuum bagged in segments with a layer of kevlar and glass in each. The mast (it was a motor sailor) was a light weight aluminum tube which was re-inforced with epoxy/laid on carbon fibers. This 32 footer, all up, incluing rig and 14 hp outboard weighs 1200 lbs. It will cruise at 12 knots under power or on a reach under sail (relitatively small sail area). The cost of materials alone riveled the cost of a new C Dory 25, plus two years of labor. If you were to buy this it would cost over $200,000.
One of the problems of carbon fibers is that they are rather brittle. Those who follow the America's Cup, will remember broken masts; those who follow the around the world Volvo racers will remember the multiple problems with the canting keel and the structure which held them--it broke.
Kelvacats only have two layers of unidirectional Kevlar material. the majority of the boat is conventional fiberglass constuction, including some balsa core--and other cored materials. I am not sure of carbon fiber use in Kelvacats. Carbon fiber is actuall heavier than glass fibers, but it is much stiffer and stronger, so you get a greater strength to weight ratio.
There are a number of high speed racing power boats which use kevlar, as well as kayaks etc. There is a definate strength/weight advantage there.
Althought the large hulls (such as the America's cup, around the world Volvo racers etc) use large amounts of carbon fiber, and autoclaves etc.
There are a number of custom one off builders who epoxy carbon fiber into and onto a laminate to increase stiffness and strength. Vacuum baging is within the realm of all backyard builders and is used extensively in light weight boats. Vacuum bagging gives better lamination of fibers and infusion of resins into the fibers, keeping the weight down. I have a friend who used both materials to build a 32 foot cat (he used a single mold for both hulls, the rest of the boat was built up. Divinycell was used as core material. The deck and cabin house were all vacuum bagged in segments with a layer of kevlar and glass in each. The mast (it was a motor sailor) was a light weight aluminum tube which was re-inforced with epoxy/laid on carbon fibers. This 32 footer, all up, incluing rig and 14 hp outboard weighs 1200 lbs. It will cruise at 12 knots under power or on a reach under sail (relitatively small sail area). The cost of materials alone riveled the cost of a new C Dory 25, plus two years of labor. If you were to buy this it would cost over $200,000.
One of the problems of carbon fibers is that they are rather brittle. Those who follow the America's Cup, will remember broken masts; those who follow the around the world Volvo racers will remember the multiple problems with the canting keel and the structure which held them--it broke.
A while back they got the idea to use carbon fiber rollers in the machines at work that make toilet paper. Some of the rollers are 12' long and 6" OD. The machine operators didn't like them because they don't have the inertia of the heavier aluminum rollers, so there's a hundred thousand dollars or so worth of the things laying around unused. I always thought two or three of them together standing upright would make a good flagpole.
Bob's comment about the stuff being brittle got my attention. We also use much smaller tubes made of carbon fiber in the wrapping machines. Those are about 3/4" OD and a couple feet long. They are pretty tough when the load is applied across most of the length, but a narrow load will break them clean and easy. Maybe it's just the construction process used to make the tubes, but it seemed odd to me that bending one across the knee makes it break off with nearly square ends and it looks like it was cut with a saw. Makes me wonder what a good sized bird could do to an airplane wing.
Bob's comment about the stuff being brittle got my attention. We also use much smaller tubes made of carbon fiber in the wrapping machines. Those are about 3/4" OD and a couple feet long. They are pretty tough when the load is applied across most of the length, but a narrow load will break them clean and easy. Maybe it's just the construction process used to make the tubes, but it seemed odd to me that bending one across the knee makes it break off with nearly square ends and it looks like it was cut with a saw. Makes me wonder what a good sized bird could do to an airplane wing.
AstoriaDave
New member
No experience with carbon fiber in full size vessels, but Tyboo's experience with the small diameter tubes rings true with what folks in the sea kayak crowd find in carbon fiber paddle shafts: any small scratch creates a stress riser, and the carbon is so brittle that a small scratch can lead to failure at the scratch under load. In a large expanse surface like a boat hull, this would not be a huge problem, my gut tells me, but I would sure yield to someone with experience in this technology.
Just for reference: carbon fiber has been used in sea kayaks as a strengthener/stiffener, in isolated spots as part of the rest of the layup. AFAIK, no one has built an entire sea kayak hull using carbon fiber. Kevlar is common, but expensive, and nasty to repair.
Just for reference: carbon fiber has been used in sea kayaks as a strengthener/stiffener, in isolated spots as part of the rest of the layup. AFAIK, no one has built an entire sea kayak hull using carbon fiber. Kevlar is common, but expensive, and nasty to repair.