But what resin?
Can epoxy’s curing be sufficiently retarded with refrigeration? Or does pre-preg require a catylized resin (polyester or vinylester) to get the laminate to cure?
I really need to know this - I plan on building a full scale F-117 this winter and am wondering if the wing skins, made from pre-preg will cure before spring flying season.
Jim
think
autoclave
One thing that hasn’t been
mentioned is the use of woven roving.
http://www.mertons.com/Reinforcements/woven.html
I have seen this in several boats, usually older models. What are the builder’s opinion on the use of this?
~wetzool
Mat
My '98 Romany uses mat. I’m not sure of the exact distribution of that mat. On the hull if it’s there it’s covered with woven roving. The bulkheads are mat and are glassed in with mat. Looks like the cockpit coaming is part mat. The deck is mat.
New Material - Nano-Fiber Additives
There is a new class of composite materials called nano-fibers. Basically these are microscopic fibers that are added directly to the resin. The resins are then used to layup the composite like normal. The nano-fibers make the resin itself a more structurally significant component of the composite by strengthening the resin-filled voids in between the primary fibers.
While most new materials usually cost more, the use of nano-fibers within the resin can result in a finished product that has the desired compressive strenmgth with either less material or using a lower cost material.
Forte Composite in Ledyard, CT is licensed to use this technology to build marine related components like masts, booms, spinnaker poles, etc…Here is what they say about nano-fibers:
“Optional Carbon Nano-Fiber Additives
Carbon Nano-Fiber additives are also available. Generally, we have found that compounding Carbon Nano-Fibers into our epoxy matrix increases the compressive strength of an intermediate modulus carbon composite to that of a high modulus composite. So why use nano-technology? Besides the space age sex appeal and bragging rights, the increase in compressive strength comes at a bargain price compared to incorporating a high modulus fiber, such as IM7. While the Nano-Fiber composite will cost more than our standard composite, it will be easily 50% less expensive than the high modulus equivalent.”
Are nano-fibers suitable for kayak construction?I don’t know. Perhaps they will find their way into high end paddles first. In the eyes of this mast producer, it seems nano-fiber’s primary benefit is enhancing the compressive strength of the structure.
I can’t think of many areas of kayak construction where compressive strength is already adequate enough just by ensuring adequate flexural stiffnes. However, there may be some use for nano-fibers in the outer layers of sandwich construction seen on most high end racing boats including surfskis. The outer layers of sandwich composites are in compression when resisting flexing. Perhaps nano-fibers would allow the use of lighterweight skins.
Still Used
Still used on some kayaks. I have an Estonian kayak built this year that uses it. It can comform to shapes easier, and it builds up thickness. As my wooden kayaks have gotten more complex in the features that I’ve been adding, these fabrics are slightly easier to use to make the complex shapes.
It’s also less expensive.
Bamboo Cloth
One exciting direction that composite technology is moving that hasn’t been mention is into greener components and methods.
The most exciting for me is the use of bamboo cloth and bio-resins. Where I’ve read about it is mainly in the surfboard industry, where the amount of cloth being used isn’t as great as in the kayak industry. This stuff is expensive! Some links:
http://www.grainsurfboards.com/2007/09/20/grain-surfboard-glassed-with-bamboo-cloth/
http://www.greenlightsurfsupply.com/organic_plastics.html
Bamboo
very interesting development - tx 4 the links. Ten years ago bamboo flooring was very exotic, expensive and could only be installed as unfinished tongue and groove w. a nailer with a limited range of grain and color.
Now big box stores like Lowe’s and Home Depot have it in prefinished snap together boards in a floating system (no nails, no glues)in a myriad of finishes and colors, including black, mahogany and nearly white, in crosscut or longitudinal grain, for less cost per square foot than premium red oak. It also proves out a little higher than red or white oak on the Janka hardness scale!
Progress may not move as fast in paddlecraft as in flooring but it could become a viable option.
Check out yield to break values
of high grade Vinylester…
Prepreg is Epoxy
Jim;
Prepreg is almost always a thermoset epoxy. There was an epoxy that set via a specific wavelength of light, but I haven’t heard of it in years.
Poly and Vinyl esters are usually catalized w/ MEKP or a similar catalyst, and would be difficult to apply evenly throught out pre resinated fabric.
Good luck on the B/F 117. Put pontoons on it. We can fly to Raystown in October
Woven Roving
Sawyer and moore Canoe both used woven roving, as did Bell when I arrived. It is heavy, tends to bridge across tightly turned shapes and, while it takes a great amount of resin, which is not good, it also creates voids between the heavy denier weave. These voids collect dirt and water, so the boat becomes a biology experiment. Then when the water freezes… Roving is not a good material for high quality; high fiber, low resin content canoes and kayaks.
carbon chopper gun
Brian, I was talking to a fellow who described a type of chopper gun used in some high tech production work, I forget the application but it was a carbon fiber material. Have you heard of it? He was clear, this wasn’t the regular glass gun system.
Dental work
My dentist uses the epoxy or similar product that is triggered by a specific wavelength on my teeth. Come to think of it I have more of my wallet tied up in those aging teeth then I do in my boat shed.
New repair kit
NSR (yes, NSR not NRS) is offering a photo-curable repair kit. The headlamp is blue LEDs that offer the correct wave length although it would set up in natural light within a few hours.
http://www.rutabaga.com/product.asp?pid=1020831
It’s also used in clothing
Google bamboo fiber clothing and you will find it’s used in many high tech garments, like softshells, underwear, etc.
early corvettes
Corvettes used a chopper gun to spray stands and resin onto half a mold. The mold half with sprayed glass was then mated to the other half of the mold, under pressure, to create a press molded panel. Handlaid woven cloth was used on some parts of the first model year vettes along with gelcoat. After that no woven cloth panels or gelcoat was used on corvettes.
The corvettes were composed of many seperate press molded panels as opposed to one or two large panels like a canoe or kayak might be. Each panel was glued to a common bonding strip. Assume the construction method took in to account accident damage reduction and ease of repair.
I like to use pieces of that early vette ‘glass’ to rivet aluminum angle and then epoxy into the hull to mount footbraces or pedestal seats with pins and clips thru the alum angle.
Bamboo Cloth
I’ve got a sample of the bamboo cloth from Greenlight. I will be testing it soon. It is interesting stuff. It is knit instead of woven. The layup process requires you stretch the material. This works fine for convex surfaces. I’m not sure that it is ready for concave surfaces, such as kayak mold.
All you have to do…
…is take a look inside an NDK boat and you can see the mat everywhere. It ain’t rocket science! Additionally, their website says as much, if you take the time to actually look.
I’ve started one…
…but my new job is taking most of my time and it’s going to be a very long writing process.