Fiberglass pro's and cons

-- Last Updated: Apr-21-13 6:44 AM EST --

I've been looking for a solo tripping boat to use in the Adirondacks. Mostly flatwater, maybe some easy moving (C1-easy C2). I found the model I wanted, but it's in fiberglass, not kevlar. Should I even consider fiberglass, or is kevlar the only way to go? (I figure I don't need royalex if I'm not doing whitewater.) Will fiberglass stand up to repeated rocky shore landings and the occasional rock? I'm a very experienced paddler so won't be ramming into landings. What are the drawbacks to FG beside added weight?

For rocky landings, fiberglass …

– Last Updated: Apr-20-13 6:16 PM EST –

... is actually tougher than Kevlar. Others here will know more details than I, but fiberglass has very good abrasion resistance. 100-percent Kevlar is what you find mainly in ultra-light hulls, and they, being so light, have less impact resistance too.

Anyway, for landings and launchings, there's no need to worry much about rocks. You'll get some scratches, and if you feel like being careful you can make sure the scratches are fewer and more minor than if you handle the boat more roughly. Your bigger concern is accidental collisions with rocks, not controlled landings. Also, an all-Kelvar hull is likely to have a foam-core floor, in which case it is more susceptible to damage from scraping over barely-submerged rocks than a single-layer hull, and much harder to repair too.

Nothing will stand up to “repeated …
rocky shore landings”

Why not get a leg out of the boat to prevent it from hitting the rocks?

With that said, I would opt for kevlar any day just because of it’s lightness vs. fibreglass.

Jack L

Fiberglass is used in Millbrook
whitewater boats.

There are a variety of glass layups. Not all are the same. There is E glass, chopper mat, and S glass in various weights.

Yes FG is more abrasion resistant than Kevlar.

Which fiberglass solo boat are you considering? Weight can be an issue on portages in the Adirondacks. Its much more fun portaging a kevlar boat over three miles than a glass one.

As Jackl said, get out of the boat in the water. Don’t run it up on shore.Oh well you are solo, you will learn quick enough the instability with bridging a boat.

Debark properly and scuffs should not even be in your head.

Millbrook makes a 14.5’ canoe,
the Patriot, but it isn’t pictured in the catalog. It is supposedly like a solo version of the Millbrook AC/DC. Like all of Millbrook boats, it has outside layers of S-glass and inside layers of Kevlar. This SS/KK layup has long been considered good for wear, impact resistance, stiffness and lightness. You would have to talk to Kaz of Millbrook to arrange for him to lay one up. The weight of the boat, before outfitting, would probably be under 35 pounds.

For rocky country and beaches, I would avoid canoes that use Kevlar for the outside layers, such as Wenonah. Too bad, because they have nice designs. But if you can tolerate somewhat more weight to get wear resistance and repairability, check their solo line for canoes that come in Tufweave Flexcore. Tufweave uses cloth that is half glass, half polyester, and the vinylester resin grabs the fibers better than it does Kevlar.

Kevlar’s main advantage is saving weight. If you portage a lot and are a flat water paddler, then there are advantages. Most kevlar boats are not stronger than fiberglass, just lighter. Abrasion resistance seems better in fiberglass boats.

The one big difference is that fiberglass boats are easier to repair. Ever try to run a grinder on all that fuzzy kevlar? Run boats in the rocks are you are likely to need some repairs down the line.

S-glass outer layers and Kevlar layers
… inside.

Mighty fine layup.

In my opinion, one is as easy to repair.
as the other.

I have done mostly kevlar and lots of them, and they are very easy to patch or repair.

Jack L

Wouldn’t a S-glass/polyester co-weave
Be something?

I’m surprised how fast Kevlar wears away in the heel area of Kevlar kayaks. I’ve put a lot of patches on Kevlar kayaks where heels have worn half way through the core.

not always possible in CL II

So will fiberglass break/crack…
with a direct impact? I’m happy to be gentle and get wet feet at landings/launches, but can never be sure I won’t smack a rock on some easy moving water. Would kevlar be better in that circumstance? Honestly, while I’m no masochist, the weight factor is less important to me than the durability.

It could, but so will Kevlar
Take some duct tape. I have holed Kevlar canoes fifty miles from any civilazation and field bandaged with duct tape.

Same for fiberglass. You did read all the posts above, corrrect? Kevlar is not a miracle fiber. If it were not for the weight fiberglass would still rule these days. Carbon and kevlar work well together. Kevlar tends to buckle under compression.

“Kevlar’s main advantage…
… is saving weight.”

In whitewater boats, Kevlar’s main advantage is making a boat more impact resistant. Weight savings is certainly nice, but replacing inner Kevlar layers with carbon would mean catastrophic failure. Kevlar keeps the pieces smaller, and keeps them together.

Kevlar is a great “inside” cloth, but deficient in two ways when used for outside layers. First, as already noted, it has mediocre strength in compression, and compression strength is important in outer layers both for stiffness and for resisting blows. Second, though Kevlar fibers resist tearing from being dragged over rough surfaces, that resistance can cause them to pull out of the resin and “fuzz”. That fuzz won’t sand off (I’ve tried torching before sanding) and is a nuisance to correct.

Glass as outside layers makes for better compression strength, wears smooth, and is easy to sand before repairs. S-glass is the hardest readily available cloth for outside layers.

An S-glass/carbon cloth has been available, but I haven’t heard of it being used in a boat. A Kevlar/S-glass weave may not be feasible because usually the glass has to be coated, in part for weaving purposes, in part for good resin adhesion.

You might be surprised at how hard
a shot a well-made fiberglass boat can take before breaking. What caused “Kevlar” boats to displace all-FG boats was not resistance to damage, but reduced weight. You just cannot get a 17 foot FG tandem cruiser down into the 40-50 pound range without it being too flexible and too easily broken. But replace some inside FG layers with Kevlar, and Kevlar’s strength in tension actually stiffens the boat, while its light weight shaves the boat weight down. Kevlar helps the FG outer layers stand up to blows, and if the FG starts splitting, the Kevlar keeps the cracks from spreading as much, and holds the pieces together.

I owned a 13 foot Mad River Compatriot that was all FG, a thin and flexible layup. It weighed 50 pounds. I used that boat on a lot of easy whitewater, and the only place the hull actually broke was at the front stem, from pitoning rocks. The reason it broke there was, in part, that the hull in the stem can’t flex.

We still own a '73 Moore Voyageur, an 18.5’all FG “supercanoe” often used for ww downriver racing. It weighed 85 pounds. We used it tandem on whitewater, including one trip down Chattooga section 3. The only place it broke was under the stern, from thumping hard when going over ledges. It took many other blows, but never broke.

So properly made all FG canoes are not necessarily fragile. But these days, you often can’t buy a quality canoe design that is all fiberglass. So it may not be anything you need to worry about.

Not to change the subject, but…
You might want to check out packing tape, (the stuff with the strings through it) rather than duct tape,

It is much stronger, and will adhere a lot better in water.

We started a carrying that a few years ago after getting the advise from a high end paddler.

Jack l

How about an aluminum canoe?
Grumman canoes sure can take a beating!

either can crack with a hard impact
It is absolutely true that a well-made composite boat is stronger than many on this board assume. For your stated purposes either an all glass or a Kevlar/glass boat should hold up very well, assuming it was made by a quality builder.

For the matter of that, I have two all Kevlar, gel-coated boats that date back to the 1980s that have done very well. They are not light layups, not foam-cored, and they have seen a fair bit of river use. Kevlar is not going to abrade and fuzz up overnight and gel coat provides a good bit of abrasion resistance. If the gel coat is starting to wear through it is not that difficult to either repair it, or cover the abraded area with a layer or layers of fiberglass before the aramid cloth abrades.

As said, a fiberglass boat can be very strong, or it can be crap. Chopper gun fiberglass boats are typically heavy, brittle and weak. Kevlar boats can certainly be cracked as well. In my experience, boats with aramid interiors are less susceptible to catastrophic failures but the aramid fibers, though they may well remain intact, tend to separate from the resin matrix to the extent that water might leak right through the cracked area.

Not as delicate
as I thought it would be.

My first “real canoe” was fiberglass and I used it on some shallow rocky rivers where I repeatedly glanced off rocks. Every time I bounced off one it made god-awful cracking noises, but rarely could I find any damage beyond a chink in the gelcoat. If you can stand the weight of them, don’t worry too much about the strength.

And, because they are old technology, you can buy a lot of boat for very little money provided you can find a good one.


pb, one reason there are more reports
of delamination of Kevlar than for glass, CAP, Nylon, etc., is that Kevlar is harder to tear than other cloths. The Kevlar fibers may hang together, but they tear partly out of the resin matrix, and you may see water seepage.

Glass and carbon are rather brittle, and if their limit is exceeded, the fibers snap off and a big split may propagate through the hull. No one would call that delamination, and it isn’t.

Nylon, CAP, and polypropylene are all stretchy, and resist propagating splits, but they aren’t as resistant to tearing as Kevlar.

The other delamination issue is the degree to which the resin adheres to the cloth. Polypropylene is very resistant to tearing, but getting a resin that sticks to it is difficult. (See Twintex.) Some detractors of Kevlar claim that resin adhesion is poor, leading to delamination. There seems to be little published data, but I found one report that Kevlar was about 15% lower than the general run of boat cloths in resin adhesion.

Again, however, since Kevlar holds together better, anecdotal reports of delamination may not be due to poor resin bonding, but to Kevlar’s resistance to tearing. Hit a glass boat the same way, and the matrix may split or crush rather than delaminate.

Just ask me, I’ll make up something good.

thank you all…
for the advice and information. I procrastinated long enough that the fiberglass boat I had been considering got bought by someone else!—but I know more now than I did a few days ago and can make a more educated purchase.