I was racing at the time that alternatives to fiberglass boats were being floated.
Aramid fiber (Kevlar) was tried and was considered to be too flexible, so layers of s glass were laid it to stiffen it.
Then solid carbon boats came out, but it was discovered to be too rigid, and prone to micro-cracking. A couple of boats actually broke into pieces.
The next iteration was an aramid outer layer with a carbon inner layer.
Now they use mixed cloth, a layer on nomex honeycomb and glass to smooth the inside.
There is no industry standard on layers, but they all agree that Aramid works great as an outer layer, because it is tough stuff, both to work with and against scratches.
Many commercial builders used layers of interior glass as a cheaper way to get them rigid enough to feel solid. Many companies think boats need to be built like motorcycle helmets. That is fine if you are strong enough to lift them.
Use two layers of 6 ounce glass and a decent epoxy for repair. Use the epoxy sparingly, on the first coat. The glass can float and not be as strong as it would if well adhered.
I like to then fill the weave and let it cure for a day. Others like to keep applying layers. That can get really messy, but doesn’t seem to cause other problems.
Looks just like my Kevlar CD hulls all the layers. All layers have fuzzy edges color is exactly the same. You can buy patches if Kevlar 3 bucks each and you can buy Kevlar tape in different widths and lengths. Not that expensive.
Want ride of fuzz coat of epoxy on there and 220 wet sand area.
I took the kayak on a maiden voyage today on a glass-calm lake. It paddles nice and I never thought about the seat so that must mean it’s comfortable. So, looks like my fleet has grown.
There were no leaks and my feet rub further forward, so I can wait for a crappy day to do the patch. I’ll use epoxy resin and fiberglass cloth that I already have (not sure of the weight, but as Paddledog said, it’s not going into space). I like rstevens15s idea of a little painters tape to edge the final layer of epoxy to make a neater job so I’ll do that too.
Here are a couple of additional photos of the kayak. It’s amazing how good the hull and deck look considering it’s a 2004. Not bad for $500 and it was only an hour’s drive from me.
Looks like new. I have a 1999 Necky Arluk 1.9 that I have no intention of replacing. With minimal care many kayaks will last almost forever. My kayak will surely outlast me after I’m pining for the fjords.
I think that Kevlar is impact resistant and carbon fiber is abrasion resistant, if I remember correctly.
Some manufacturers will have layup diagrams, etc., on their websites. You could probably throw some fiberglass on that, just make sure that if it’s a polyester layup that you use polyester resin rather than epoxy (although for a small patch like that it probably won’t matter). I’m sure there are some people on this site with more knowledge than I. But I know that polyester will bond better with polyester than epoxy will.
I don’t know about others, but I put my half-size z-rest foam pad under my feet. I do it for comfort, but I think it probably has the added benefit of preventing this kind of wear.
The problem as told to me by a boatbuilder friend is that, when doing multiple repairs, it’s better to have all polyester rather than a mishmash with epoxy because the two materials behave differently. He cursed at epoxy when he had to work on repairs that others had done to his boats. I’ve also read something similar.
Re: Kevlar- it is impact resistant (think bulletproof vest) whereas carbon is abrasion resistant.
Kevlar is light and flexible with good impact and abrasion resistance. Carbon fiber is light, stiff and strong, but doesn’t have great impact resistance and it’s abrasion resistance is actually pretty poor.
Nope. Epoxy bonds fine to polyester or vinylester resin and it stronger than both. It’s harder to sand, which is probably why your friend was complaining.
The resin used doesn’t make anywhere near as much difference in the resulting repair as the reinforcing fabric used. Matching the material (fiberlass, Kevlar, carbon fiber) and the type of fabric (weight, weave, number or layers) as closely as possible is important, though it doesn’t have to be exact.
Aramids do have good abrasion resistance but don’t necessarily behave nicely when abraded tending to fuzz up into strong little spicules that need to be shaved off when repairs are required. Fiberglass will just abrade through leaving a relatively smooth void which is easier to patch over. S fiberglass has significantly more abrasion resistance than E fiberglass. Dynel has better abrasion resistance than either.
The relatively poor compression strength is one of the weaknesses of aramids and that is why I prefer to use them on the concave side interior side of a curved hull rather than the exterior convex side. Another significant weakness of aramids is the fact that resins do not bond nearly was well to the fibers as fiberglass and other materials do. When an aramid laminate is severely stressed the fibers will often remain intact but will dissociate from the resin matrix greatly diminishing the strength of the laminate.
Carbon fiber has the highest strength to weight ratio of all and produces a laminate with a high Young’s modulus meaning it is very stiff. That makes it great for lightweight racing boats or flat water boats. It will resist some pretty strong impacts but it has very little “give” and when it fails it tends to do so catastrophically. Carbon fiber laminates often break leaving very sharp, irregular edges something like broken glass and just as sharp.
Builders of top-end boats will combine different materials using them in ways that maximize their positive attributes rather than use a single material. Very common lay-up schedules are one or two layers of fiberglass on the external surface and a couple or several layers of aramid or Innegra hybrid on the interior of carbon fiber on the outside with aramid on the inside. Chemically-activated polyester is often used in conjunction with fiberglass to result in a stronger laminate than fiberglass alone.
This thread kind of migrated to a general advice discussion on what materials and methods to use for a small repair. So, I figure I’ll post what I’ve done to patch the two worn spots that started the discussion. This is what I did, not necessarily the right thing to do or the best way to do it. I’m sure I’ll get some advice on things I might have done better.
I scraped the worn area gently with a carbide scraper, but found that too much scraping on the edges just enlarged the radius of the frayed area. I then cleaned the area of the hull with a little acetone (since I have some) and then a wipe with isopropyl rubbing alcohol. I used 6 oz fiberglass cloth and 5:1 epoxy resin which I already had. I made a small oval patch to roughly fill in the middle of each worn spot and then a 3.5 x 6.5 inch patch, cut on a 45 degree bias, over that. The rectangle covered the entire worn area. I fiber glassed those in one application, and squeegeed the patch to try to push out any air bubbles.
After it all cured, I scraped the edges a bit with the carbide scraper, cleaned with a little soap and water and then isopropyl to get rid of any amine bluish. I then applied a larger 8 x 10 inch patch over the whole area. I had a piece of brown craft paper with a 10 x 12 opening taped down to neaten the edges and protect from drips. Same process as step one: wet the area with resin, apply patch, saturate patch, squeegee out air, smooth out resin with brush.
The temperature for both steps was in the low 70s with moderate humidity, so I used a fast hardener, and for the final step I’m also applying gentle heat with a 40 watt incandescent bulb. I have a temperature probe near the patch that’s reading 81 deg F (thin white wire in the photo).
Frayed fiberglass edges can be dealt with by simply sanding them smooth. With aramid it is sometimes easiest to apply a bit of epoxy over the frayed edges, let it cure to reasonably hard, and then shave off the epoxy-coated spicules with a sharp blade like a scalpel or X-acto knife.
You can also diminish the tendency of the strands at the edges of a cut fiberglass patch from swelling up when wetted out by using mold release fabric (“peel-ply”) over the patch when you wet it out.
I agree that it looks good and based on your description, it’s structurally sound. Once it’s cured, you can clean up the edges a bit with the scraper, then apply another coat of epoxy.
One word of caution; you mention “rubbing alcohol”. Most off-the-shelf isopropyl alcohol is 70% alcohol and 30% water, but some types of “rubbing alcohol” contain oils, scents and other chemicals that could adversely affect a glue bond. so it’s important to read the label and know what you’re buying. Ideally, if you’re going to use isopropyl, get either the 91% stuff from the pharmacy or the 99.9+% that’s often available from electronics suppliers.
An easier to find and cheaper alternative is “denatured” alcohol from a hardware store or home center. It’s ethanol with enough methanol added to make it too poisonous to drink. I always keep a gallon can of it kicking around, as it’s really useful stuff.
Good catch. Mine is the 70/30 type, just isopropyl and water. It’s cheap and I usually use it as my first attempt as a cleaner, sticker remover, etc. before going to something stronger.
