Syringe Fillet?

I am looking into building my first kayak which at this point looks like it will be a chesapeake 17lt, some of the posts on here about large fillets effecting weight are very interesting.

I found a video on youtube demonstrating a kayak build in which they do not seem to thicken the epoxy when filleting, they simply syringe a small neat amount of epoxy along the joint and then apply the glass tape over the top.

This technique  appears to be neater and uses less epoxy, is there any reason why i cannot use this method on my Chesapeake 17lt, take a look at the vid. Many thanks.

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RE: Syringe Fillet?


YES!  There's a reason you can't do this.  Unthickened epoxy will run right through the seams of your plywood, making interesting shapes on the floor of your work-space (mine are all over the garage floor!!!). 

I tried using slightly thickened MAS to do an end pour and most of it trailed down the center of the hull, seeping through the seam and leaving a line of glue (now hardened and forever affixed) on the concrete.

In my experience, which is recent and limited to one build, the thicker the better!  Thickened epoxy is easy to spread, doesn't sag, run, or otherwise frustrate you.  And after you fillet, that thickened epoxy will take a tape overlay easily, letting you smooth things along as you wet the glass out.

See my trail of pics at Chesapeake 17 Lt (modified) on this forum.  Not always pretty, but I'm pretty impressed with where I am today!

Good luck, and great choice,


RE: Syringe Fillet?

I believe there's also an issue with providing a rounded shape (created by a built-up area of epoxy) for the glass to properly cover, rather than a sharp corner.

RE: Syringe Fillet?

The way to do what you're suggesting, but keep the strength that comes from good smooth fillets is to stitch your hull and do small epoxy 'tabs' with the syringe in between stitches.  Wait a day or two, then remove your stitches.  Go ahead and proceed with your fillets and taping at this point.  Without the stitches taking up space, you'll be able to do much thinner fillets, and thus save a lot of weight.  I got through a whole build and only used a little more then one container of wood flour.   This method is actually quite popular, and several builders on here can speak to its simplicity and ease of application.  


Good luck,


RE: Syringe Fillet?

The main purpose of fillets is to provide a base for the cloth to curve without leaving air bubbles underneath. They also fill in the wire holes and the spaces between the epoxy "tabs" described by Chris. The size of the minimum fillet increases with the weight of the cloth. For four ounce cloth, carefully applied, you only need about 1/4-inch radius. I find the best fillets come from a peanut butter consistency made with three parts Cab-o-sil and one part wood flour. Where you can reach the seam easily, spread the mix with a tongue depressor, then smooth it out with the same tongue depresor held at a 90-degree angle to the seam. For areas that are hard to reach, like inside the end compartments after you have attached the deck. I used a new technique with great success on my last boat. I bought empty West caulking tubes (2 for $3), stuffed the epoxy mix into them and spread it with an ordinary cauking gun. The tubes can be cleaned out easily after the remaining epoxy cures and then reused. -Wes

RE: Syringe Fillet?

Where did you get the 'West caulking tubes'-Alan

RE: Syringe Fillet?

I bought them at West Marine. -Wes

All of the above and...

...your seams will be stronger with a thickened fillet. Use a rounded piece of scrap plywood or wide popsicle stick to shape the thickened epoxy so that it is cunvex-shaped, then add your glass tapes to further strengthen the seams. If you don't use the thickened epoxy and you bump the kayak hard on a rock or whatever, odds are you will brek the seam. As stated before, epoxy will not fill the seam on its own, it will run right through (practical experience talking here). Hope this helps.


Robert N Pruden

RE: Syringe Fillet?

From twofootartist's post, it sounds like there is a benefit in terms of fillet weight to relatively more layers of relatively  lighter-weight-glass fillets.

So, I guess if you can build up the required thickness out of 4 oz. cloth, with an initial 1/4 inch radius fillet, that would be lighter than an initial fillet of heavier cloth with the higher radius needed (to limit built-in bending strain on the fibers, and the resulting loss of strength.)

Wait, I have another great invention!  Someone should sell biased, multi-layer tape, stitched together on the centerline, of 1 oz glass that would require no fillet at all.  All the strength, none of the weight.

No charge for this.  Just tell the interviewers, when they ask you how you came about your great riches, that a long-forgotten CLC forum guy gave you the idea.  (Except the use of biased tape, which Laszlo says someone already thought of.) 

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