travels and travails

Monday, June 03, 2019

An epoxy keel strip for the P&H Capella 163

Introduction

I like to have keel strips on my kayaks, helping to avoid the deeper scratches in the gelcoat that occur along the keel line in normal launches and landings. I have used Keel Eazy in the past and consider it a good product. Nevertheless, my problems with Keel Eazy are that
  • the glue isn't that dependable and must be routinely examined, sometimes ‘refreshed’
  • the strip isn't that easy to repair once sand gets under the strip
So here I tried another approach. I made the strip itself out of an epoxy adhesive, as will be described later. I used peel ply over the epoxy to get a smooth enough finish to avoid sanding the epoxy. The epoxy was G/flex which remains flexible, yet very tough. Note that this kayak is composite. Plastic kayaks (ABS or rotomolded polyethylene) may require somewhat different surface preparation.

Note that one must get everything ready before mixing the epoxy because it has a 45 minute working time, leaving little time to run to the hardware store.

You should have eye protection and work in a very well ventilated area. In my case, I worked outside. Additionally, a fine enough dust mask would be useful. Rubber gloves would be advisable for working with the epoxy.

What was used:

  • Dust mask, rubber gloves, eye protection
  • Sandpaper to prep the keel surface – I used 100 grit.
  • Something to clean the kayak after sanding – I used alcohol.
  • G/Flex 655 Epoxy – I bought more than needed and may keel strip another kayak later. The 655 product is “thickened”, whereas the 650 product is not - probably either would have worked. At any rate, I got 1 quart of epoxy resin (includes the thickener) and 1 quart of hardener. This is mixed in a 1:1 ratio just before applying.
  • 3 cups, the larger for the final epoxy mix and two identical smaller cups – one for the resin and one for the hardener before mixing. The smaller ones together should not have more volume than the larger.
  • A roll of masking tape, maybe 2" wide.
  • Something to apply the epoxy - I used a putty knife of width 2”.
  • Peel ply - This is typically sold in large sheets, which I cut as needed.
  • A roller e.g. a small paint roller - This is used to smooth the peel ply and work out any air bubbles.
  • Single edged razor blade, used to help cleanup after the project.
  • G/flex 650 Epoxy in its 2 small tubes and a small stiff brush, to clean up any missed/neglected areas.
Sequential Steps

My kayak was conveniently set on two saw horses, hull up. As a short person, this made a nice height for me to work. This particular kayak was scuffed here and there, but not damaged so there was no need to patch the keel area before this project.

Preparing the Kayak:
  1. Clean the kayak hull, especially the keel area.
  2. Use masking tape to ‘frame’ where the keel strip will go. My keel strip was planned as ~3.5” wide, so once the masking tape is applied the keel strip will lie inside the masking tape perimeter.
  3. Sand the keel strip area very lightly then clean that area with alcohol. Let that dry out.
Preparing the Peel Ply:
  1. Cut a long strip (about 4” wide) of Peel Ply, long enough to cover most of the keel other than the curved bow, curved stern, and skeg cavity.
  2. Cut a strip (about 4” wide) that is a bit longer than the skeg cavity. It should overlap the adjacent Peel Ply strips once applied (later).
  3. I cut short strips about 1 or 2” wide and maybe 4” long. There should be enough strips to cover the bow and stern curves. When the time comes, these will be placed along the keel curves with the 4” side of the strip perpendicular to the keel, The short sides of the strip must then overlap. The Peel Ply doesn’t do curves well, so the short pieces allow applying the Peel Ply to curves.
Preparing the epoxy:

I had purchased 1 quart of the resin and 1 quart of the hardener. I used about a third of each for this kayak. Use 2 equal size smaller cups and fill one with the resin and the other with the hardener. Then dump those into a third larger container, big enough to hold the 1/3 quart of resin plus the 1/3 quart of hardener. This may take several repetitions to transfer all the goo from the two smaller cups into the larger.. Mix the goo thoroughly in the larger container. You have ~45 minutes to complete the job, which is plenty of time.

Note: One can add carbide powder to the epoxy mix to give the resulting keel strip a more attractive and consistent black color. I did not investigate this or other similar options. My keel strip is not handsome, so theft of the kayak becomes less likely.

Applying the epoxy mix:

Using the putty knife, apply the epoxy mix to the hull within the masking tape boundary. Take care to get as little epoxy on the masking tape as possible. Also do not slop any of the epoxy into the skeg cavity.

Applying the Peel Ply:

Do this right after the prior step. As the Peel Ply is placed over the epoxy, ensure that
  • a decent size piece at the end of each Peel Ply strip remains free of the epoxy so the whole strip can be pulled off after the initial epoxy cure
  • little if any of the epoxy mix slops over onto the masking tape (makes cleanup easier later)
  • each strip of Peel Ply overlaps any adjacent strip.
Use the short strips over the bow and stern curves, the longer skeg piece over the skeg cavity, and the really long piece for the ‘straight’ part of the keel. As it is applied, the Peel Ply will begin to ‘wet out’. Use the paint roller to smooth out the wetted Peel Ply. Pay special attention to any white air bubbles and work those out to the side with the roller.

Once the epoxy has cured sufficiently:

The cure time for the epoxy depends on temperature. In my case, the initial cure took about 12 hours. Pull off all the Peel Ply strips. Pull off all the masking tape.

Cleanup and final cure:

Any excess masking tape that did not pull off can be removed by judiciously scraping with a razor blade. The skeg cavity needed extra attention because I was overzealous in avoiding getting any epoxy into the cavity. I had some G/flex 650 which I mixed and applied to the skeg box edges with a small stiff brush. I also used this approach on any other areas not properly covered with epoxy. Let the epoxy cure for at least another 24 hours.

The Result

The keel strip ends up looking neat enough, but the option of a nice black color would be nice. I would not hesitate to embark on the same sort of project again, but I would need to see
  • how it holds up after a long season
  • how easy it is to repair (should be very easy, using G/flex 650
My initial guess is that this will be preferable to Keel Easy, yet easier than the somewhat similar job with a fiberglass keel strip.