Building a canoe: S2-glass vs kevlar vs carbon

I started working on a canoe mold 15 years ago. Moved, lost my work space, and put the project on hold. Now I am back on the project and will be building a canoe soon.

The project is a 12'4" whitewater boat. I started this when I was paddling a lot of whitewater. Now I'm older and not paddling any of the same whitewater rivers, but want to build a boat anyway. My intention is to not create a boat to run extreme rapids but one to paddle mild whitewater.

I want it to be very light, less than 20 pounds for the hull. I have a small pond in the back yard and will use it there in addition to some river paddling.

I have some carbon and S2-glass. My initial plan was to have two layers of reinforcement on the outside and inside with a core in between. Additional reinforcement in the front, back, and another layer for the lower section. S2-glass on the outside and carbon or kevlar as the next layer. Now I'm thinking just make the boat all S2-glass. Pretty sure all my materials are 6 ozs per yard. The surface area of the mold is about 4 sq yds.

I have several paddling buddies who may also want a boat and S2-glass is certainly cheaper.

Any downside to going all S2-glass? I know carbon would be a little lighter/stiffer and kevlar has its positives and negatives. From my limited knowledge, it seems the best characteristic of kevlar is when it breaks it stays in one piece. No so for carbon and fiberglass.

I will use resin infusion for this project.

Thanks...Alan

 

The resin choice plays into it too.

Any advantages that Kevlar and carbon have to offer are muted when using anything but epoxy.

Either way I’d go with s glass though, mainly because of the durability.

 

I don't know much about ultralights, but never heard of a solid glass ultralight.

Something like 6 oz woven is not a very strong glass. Even a cedar strip uses two layers of it on bottoms, but the glass is not the main structure,
the cedar is.. You would not likely build a glass canoe with woven... I guess.

I would recommend kevlar, but kevlar is rumored to float in layups; although infusion would likely negate that issue.

The downside to kevlar is it is a bear to repair.

And I am not sure about a carbon canoe. It sounds interesting, but might crack easier..

Sorry to be so indefinite here. Hopeful for some crosstalk mostly.

 

S2 glass is better than Eglass in almost all properties. Carbon on the outside is best for cored construction but is too expensive. Kevlar is tough but poor in compression and it cannot be placed outside because once abraded. it wicks water.

So S2 glass is a good choice. Cored construction will make it stiff so there is less frames to hold up the panels. That is what makes it light.

Epoxy is good but Vinyl Ester is cheaper. If postcured, it achieves the strength of room temp cured (of most) epoxy. Also VE's viscosity lends well to infusion. you don't need special blend of epoxy.

 

What core? Sounds like a great idea with a core.

 

Edited:
Thanks to all who have replied. I will be using epoxy. For my core, in addition to considering 3D-Core PET 100, I have been experimenting using Gorilla Glue with fumed silica added to form a paste. Because Gorilla Glue expands, the results have been quite promising. The downside is a lot of sanding will be required prior to the last reinforcement layer being infused. I am used to a lot of sanding! This type core will conform to any surface and is harder than any core material I have tested, other than end-grain balsa. Resin absorption should be minimal. I am using layered dry wall mesh to help with equal distribution. I do not add moisture. Adding moisture will increase foaming/thickness but also reduces hardness.

 

Do you want ultra light or a bit more durability.

Carbon is lighter and if you’re careful it works very well, don’t expect to bang it around on the beach and have it last though. S glass weighs a little more, but can take much more abuse.

On a small craft the weight penalty won’t be much.

I have customers that build racing shells, they don’t use cores, just infused carbon and epoxy.

My fist job in the industry was building glass kayaks, we never used a core, even on the lightest builds.

The hull shape doesn’t require a core to maintain its shape in the water.

 

Thanks for your reply. More durability, but light. Before I lay up everything, I will do a few small panels to see how they do.

 

you realize the elongation properties are important?

if gorilla glue and fumed silica are not more breakable than s glass, I'd be surprised

the stack needs to be a system of similars

a very hard core may fair poorly on impacts or with mechanical fatigue, for example

 

Thanks for your comment Fallguy. I'm not sure what it will do right now. I was originally leaning towards 3D-Core until I found out one meter squared absorbed/required 400 grams (14 ozs) of resin. I will do a couple of test panels with the Gorilla Glue and go from there. The Gorilla Glue/fumed silica is very hard but flexible. In my test so far, when bent quite a bit, it does not break. This is not going to be a boat I abuse.

 

Don’t make flat panels, they need to have the same contour as the hull will. You’ll probably see that a core isn’t required.

 

For light vessels like canoes the skin thickness to achieve enought puncture resistance is adequate for most of the hull without any core. With core you must have allmost the same skin on both sides plus the core and you end up double the weight. Instead add a few stringers if more stifness is needed.

 

Every single all glass canoe I have ever encountered has been heavy.

Undoubtedly, you will probably figure this has drifted down Polemics Canal, but not so.

I grabbed a glass canoe online that weighs about 20 pounds more than my rather heavy strip canoe of similar beam and length.

If coreless is okay and less weigh, what are they doing different? And why would manufacturers put more material into a canoe than needed? Is this canoe that much more durable?

15' 10" Old River Square Stern Canoe http://directboats.com/1510sqstca.html

 

A commercialy sold canoe is built to last for many decades of abuse out of the lowest cost materials available. There is no comparison to a special built product that will be cared for.

 

Ondarvr & TeddyDiver: Thanks for your comments. I haven't considered a boat with less than a full core.

Fallguy: Thanks for commenting. The link you posted most likely represents a hand-lay up fiberglass boat. If it were sprayed/chopped fiberglass, it would be heavier. Most of my experience is with Mad River Canoes. Just purchased a 16' Mad River Ultralight kevlar boat in August. Mad River says is weighs 45 lbs, but the actual weight is 50 lbs. It has a clear epoxy gel coat, a single layer of fiberglass, a single layer of kevlar, foam ribs, a thick core on the bottom, and extra kevlar in the bow/stern and lower/bottom sections.

Mad River also makes a fiberglass boat with the same dimensions. Mad River says it weights 61 pounds so it probably weighs 66 pounds. It has no core or ribs. There is no indication the Ultralight or the fiberglass canoes are resin-infused. Their new 2019 carbon and kevlar boats are resin-infused. They have discontinued the fiberglass model.

In the above canoes, the fiberglass boat weighs about 32% more. The fiberglass boat also has no core or stringers so it will have more layers of glass than the Ultralight. The Ultralight is not designed for any abuse. I know nothing about how much abuse the fiberglass version can take.

With all that said, I'll be the first to admit I am a newbie to the world of composites. That is why I am posting on this site - to learn more about composites. With resin infusion, I have read where S2-glass can have the same resin content as kevlar and carbon. I assume that is why it is used a lot in aerospace. If I am wrong, I hope someone will correct me. I have also read kevlar is 43% lighter than fiberglass. I'm not sure what this refers to. If I resin-infuse a canoe with one layer of 9 oz S2-glass will it be heavier than a canoe built with one layer of 9 oz kevlar? I have no idea.

I just bought 20 yards of 50" 9 oz S2-glass for $8 a yard. That's not a bad deal. I do have some 50" 6 oz carbon but no kevlar. The carbon I bought 15 years ago for $6 a yard. It's rather stiff but will get used at some point.

Looking forward to additional comments.

Again, thanks for your post.