H Channel seam vs. Fiberglass seam?

I’ll be acquiring a new Current Designs Caribou. I have the choice of the standard seam construction, using H channel to connect the deck and hull, or an upgrade to a fiberglass seam. The CD web site describing this construction says: “The seam is fiberglass tape impregnated with gel coat in your choice of color, and replaces the ‘H’ channel extrusion. It’s just as strong as the standard method and gives you another way to make a statement about your passion for paddling.”

I really don’t need to “make a statement”, but it seems to me that the fiberglass seam would be much easier to repair in the case of a leak or damage. The H channel seems to create an obstacle to access the seam. On the other hand, the H channel does provide a kind of “bumper” for the seam and may protect it from damage in the first place. Also, is it actually better construction?

I’d be interested to hear peoples’ opinions on this. Thanks.

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I think you’re correct, although I’ve
never had to fix an H channel seam.

For ww boats, the inside seam is sometimes Kevlar, and perhaps bias-oriented tape, which puts twice as many fibers across the seam. The outside seam may involve two layers. Probably the layup of the seam should be comparable in quality to the layup of the adjoining hull.

Depending on their selection of the plastic for the extrusion, and the quality of the adhesive, an H channel seam might be very, very good. I don’t know. But if a repair became necessary, I don’t know what one would use except for glass cloth and epoxy, and I’d rather do that over a glass seam than a plastic extrusion.

Both are guaranteed
CD warrants both seem methods for life, so it’s mostly a matter of which method you like best and if you’re willing to pay the difference.

2007 CD Suka w. fglass seam
mine is a custom glass/kevlar boat originally used in a rep’s demo fleet. This was the second model year for the Suka.

He told me he opted for the fiberglass seam for the extra strength and because it could be colormatched to the coaming. He also said it saved a bit of weight ~ 1 lb. Nice for me to have a kayak 16’6" weighing 41 lbs.

Whether or not these factors have value for you or any buyer is a personal decision. I don’t have a strong feeling about the seam construction myself.

I’ve had no troubles w. the glass seam (or any other part of the kayak) The fit and finish overall (incl the seam) is excellent.

Would not have been a dealbreaker if the H channel seam were there instead.

Glass seam
Without question. A poster on another forum is dealing with a seam leak on an H-channel boat that CD themselves couldn’t fix. Cheaper & easier for the manufacturer is not often better for the consumer.

Just some info I found - fiberglasssite?
With the H seams on the inside of the hull, the inside perimeter of the deck-to-hull joint has a “fiberglass biaxial roving strip” laid in. So the inside seam is glassed. I was curious what that was, and it is the last item listed below, if this source is good (fiberglasssite). Evidently woven roving, the item before biaxial below, needs to be combined with chopped strand mat in situations that require waterproofness, and the biaxial mat, or combination mat, that CD uses combines the two to meet this need. I have no idea about the structural integrity of the competing methods. I can say I have a 99 Caribou, a 97 Solstice GTS, an 03 Extreme all going strong. I’m pretty sure they all have the H seam.


Woven cloth

Fiberglass cloth is made much as any other cloth is . It is woven on textile weaving machinery. It can be woven several different ways, plain weave, long shaft satin weave, and unidirectional weave. (fig 2-1). There are also other more complicated weaves, such as twill weave, but we will stick to these three types for our purposes.

Fiberglass cloth is measured by ounces per yard in the USA, and grams per square yard in Europe. Cloth sold in the USA can vary from one half ounce per square yard, up to over 50 ounces per square yard. The most commonly used weights for most projects are four, six, and ten ounces per square yard.

Most cloths that you will find yourself using are plain weave. Plain weave cloth usually has the same number of strands running it’s length and width( warp and weft). Plain weave produces a stiffer end product than most other weaves, and because it has the same number of strands running in each direction it is easier to keep the laminate strength balanced.

Plain weave cloth is ideal for large and simples molds, and flat, or nearly flat surfaces.

For each kind of cloth we will explain it’s benefits and it’s limitations. Woven cloth gives the most strength, but is the least thick. Cloth requires the least amount of resin, this makes the cloth very strong, but it lacks stiffness. Also, it does not give good waterproof ness because of the small amount of resin. It is the resin, not the cloth that gives you the waterproof ness. To solve this problem, cloth is usually layered with chopped strand mat. More about mat later.

Fiberglass cloth



Chopped strand mat is made by laying down chopped strands of glass fibers in a random pattern on a flat surface. Each stand is about two inches long. A bonding agent (usually a powder) is used to hold the strands together. The result is a mat of even thickness , made up of fibers going in every possible direction. This will give you strength in every possible direction.

CSM as we will call it, is sold in ounces per square foot. All other reinforcements are sold in ounces per square yard. It can be purchased in weights ranging from ¾ ounces per square foot, up to 4 ounces per square foot. In the USA the two most used weights are 1.5 ounce, and 2.0 ounce per square foot.

The CSM that you find in stores, in plastic packages is 1.5 ounces per square yard, and it is overpriced. Compare the prices to the prices on www.FiberglassSite.com.

CSM usually comes in widths from 38 to 50 inches. In can be purchased by the yard or in large rolls.

CSM Is the least expensive of all reinforcements, and it is very versatile. CSM soaks up more resin than any other reinforcement. The advantage of this is that is gives more waterproof ness than any other type of reinforcement. CSM produces the stiffest laminate, and because the strands are in a random pattern, it gives strength in every direction.

For repairs jobs , CSM is the easiest material to use. It is easy to wet out, or saturate with resin. In it’s dry state it is fairly stiff and will not easily go into tight curves, but when saturated with resin, the binder holding the individual strand together breaks down, and this allows the mat to be shaped into any configuration.

When using mat on curved surfaces, 1.5 ounce per square foot is recommended. 2.0 ounce is better suited for flat surfaces, and for buildup, because it is stiff.

It takes about 20 layers of 1.5 ounce CSM to make a laminate 1 inch thick. In most repairs , two layers of CSM will be sufficient, but you can make it as thick as you wish to get the desired strength.

CHOPPED STRAND MAT www.FiberglassSite.com

Woven Roving

Fiberglass woven roving (see picture below) is different from fiberglass cloth. Fiberglass cloth is made from glass fiber thread that is twisted like yarn, woven roving is made from continuous strands of glass fibers that are grouped together. Woven roving is a thick cloth like reinforcing material. In the 18 and 24 ounce weights, it is as thick as a blanket. The two most common weights for woven roving, are 18, and 24 ounces per square yard.

Woven roving is mostly used for buildup when thickness is needed. It is alternated with layers of chopped strand mat to fill in the heavy weave pattern of the woven roving.

The combination gives good thickness and strength. On a weight basis, woven roving is cheaper than cloth, and more expensive than chopped strand mat… The advantage of using woven roving, is that is gives a quicker buildup of thickness , compared to using cloth. Because of the heavy thick weave, you are not going to get the nice smooth finish of cloth when you use woven roving. , that is why it is generally used for buildup, after you use cloth for your first layer , to get the smooth finish. Like cloth. Woven roving uses less resin then chopped strand mat. That is why in situations that require waterproof ness, chopped strand mat is used in combination with woven roving.

WOVEN ROVING www.fiberglassSite.com


There is a product available called “combination mat” or Biaxial mat . it is a “combination” of woven roving , and chopped strand mat. They are stitched together. It is sold in various weights. It is also called stitch bonded mat. This is used to save time when very heavy buildup is needed. It is flat instead of woven and has a better appearance than woven roving. It also has the advantage of saving on resin because you are doing two steps at one time ( roving and mat). In most projects resin will be your highest expense, so the higher expense of Biaxial mat may be worth it. Many of our clients have switched to it. SEE PICTURE on this web site

good info
thanks…mind providing that link? I’d like to better inform myself and others may, too.



that input from Matt Broze pretty much decided things for me. I’d go fiberglass seam all day long.

There are other makers using H channel seams as well (other than Eddyline and Current Designs). Don’t have time now to visit their websites but I can recall reading of it & in fact the H seam was touted as a superior feature (?) Matt Broze’s description and reasoning would indicate otherwise.

good discussion.

Thanks, everyone, for your feedback
I think I’ll go with the fiberglass seam. Although some posters have had good experiences with the H channel, it might add some potential flaws that aren’t necessary.

Cross link verse Plexus
H seam is an efficient way to seam kayaks. No-one sticks their head in the boat, Methacrylate adhesives are strong and proven and costs are controlled.

Tape seaming with resinated fabric strips is a messy and ugly busines. It needs be done inside and out, the inside part done with a brush on a pole with someones torso inside the hull. 'probably want to wear a hat and respirator.

All that said, we want the seams to be put on soon eenough after the hull and deck are laminated to achieve cross linking of the resin, i.e. two or three days.

One can imagine how that might be done in a small shop that can build hulls one at a time. How we might ascertain that cross link can be achieved in a huge Chinese factory is a question.

Most likely
The repairs you make w the kayak won’t have to do with the seams.

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One would want to pick the seam
method that obviated having to land and tape a leaking seam.

Found this old thread someone I know damaged the H seam when there QCC fell from the SUV. Pieces now missing. How can they repair the damage? Cut outside of seam off in damaged areas? If so bond back new face piece with what? Just fill where seam is damaged with glass and paint or gelcoat? :blush: Thanks

Google Photos

Glassed on the inside of hull over the channel.

Not repairable as I figured. No material even available to put a face piece on if that was even feasible.

Guess they will be re-seaming with fiberglass after cutting of exterior H channel.

Going to Turning Point Boatworks new seam glassed on all the way around. Less than 600 thanks all. It’s a 14’ composite QCC. THANKS ALL