Caulking a Small Boat - Tools, Tips and Materials

12 May 24:

Caulking cotton and wicking are used to fill seams between planks. When water finds the cotton, both the cotton and wood swell to create a watertight seam. A one pound roll of caulking cotton = 210 feet. We ordered from Defender but Jamestown Distributors is our usual source. We also ordered caulking wicking. We used Defender because we wanted to try the Teak Decking System seam sander and reefing knife, but found out that these tools are way too big for the tiny seams on our dinghy.

One tip with the cotton is to roll it into a ball and keep the ball in a clean container. This keeps the cotton from picking up sawdust, dirt, twigs etc... from the shop floor and other tools can ride around in the box as we work our way around the seams.

Different seam sizes = different materials. Wicking and cotton can be either peeled apart to get the right size for smaller seams or doubled up for larger seams. For this thin 3/8" planking we used about 1/3 of a strand for a 1/8" seam, and less for the tighter seams. When the seams got real tight we switched to wicking. 

We have a traditional caulking hammer, irons and seam roller. For light boats and small planks a caulking hammer can provide very light taps to the metal irons. Any other type of mallet or hammer can be used, but it is best to strike the metal irons with wood or nylon, as a metal hammer would wear out the head of the caulking irons and it is noisy. 

We are not sure what this tool was originally designed for, leather work possibly, but it makes a great tool to roll half a strand of cotton into a 1/16" seam.

Video: https://youtu.be/BNg4X5PO5hM

We broke out the TotalBoat TotalFair to cover the rivets heads. Some folks do not fair over the heads, but they had been faired over in HENNING, so that tradition continues. 

Once the cotton was in the seams, we put a protective coat of primer over the cotton from George Kirby Jr. Paint Company. If your wood is very dry and/or new, it may help to seal up the seams with a wood sealer or primer before caulking. Then either wait for those products to dry or plan on having a messy caulking experience. 

This side is caulked and faired.

Still need to caulk this side but the rivet heads are faired. 

Next up? Sand the TotalFair then get more primer on the wood. Following that we will put a flexible compound in the seam to protect the cotton and that will move a little as planks shrink and swell. And paint. 

Log of HENNING.

1978 AMF Sunfish SUGAR 2 29 Jul 18 Paint Finished

29 Jul 18:

Final coat of Kirby's Maynard Bray Off White, rolled 100% with a Mighty Max Mini Roller and tipped with a Corona Deck and Trim brush. George Kirby recommended the brush, they also sell them, is had a soft, full head on it and held a lot of paint. The bristles were very flexible and we are very happy with the paint.

She'll be doing loops and rolls soon!

Restoration Log of SUGAR 2.

1978 AMF Sunfish SUGAR 2 26 Jul 18 Kirby Deck Paint

26 Jul 18:

Catching up the blog. Each layer of primer or paint took about a day, so we skipped posting about each coat. Sanded old paint off of SUGAR 2's deck with 120 grit pads on a DeWalt Random Orbital sander. Fixed one more void on the seam with THIXO injected by a syringe then lightly clamped. Then did another leak test, which she passed.

Put a coat of TotalBoat Gleam Satin Varnish on the rudder, tiller and tiller extension.

Sanded, leak tested, ready for tape, primer and paint.

Removed the bridle eyestraps, took out one screw at a time, swiveled the eyestrap out of the way, reinserted screw, then took out other screw. This helps ensure that the wood backer block inside does not drop off. The blocks are glued and fiberglassed into position, but 40 years later they can come loose. Sometimes excess expanding foam holds them in place.

Taped off the bow and stern and brushed on Kirby Primer tinted with #4 Orange with a short handled sash brush. 2 coats.

2 coats of Kirby's #4 Orange, it went on smooth with a brush, 100% in 90F temp. Color is awesome and so is Kirby's Tech Support, George answers the phone!

Skipper peeled the tape!



Removed the cockpit trim, 1/8 inch drill bit to drill out the head of the rivet. A wide, flat screw driver is handy to tap the trim loose. Sometimes a remnant of the rivet is stuck in the fiberglass, like you see on the far left of the photo, we used an awl and hammer to tap that piece out.

We've enjoyed using the Kirby Paint. They have been making paint since 1846 and custom mix the colors. It has been easy to use, levels well and the colors pop on this boat.

Before we did the deck we sprayed the perimeter and cubby of the cockpit with light gray Rust-Oleum, it was east to reach far corners with the spray. On the non-skid portion we brushed on Kirby #25 Light Gray.

Kirby White Primer on the mid deck then first coat of Kirby's Maynard Bray Off White. Primer brushed and then lightly sanded with 120 grit. Paint rolled with a Mighty Mini roller and tipped with a Corona Deck and Trim brush. Very happy with the results!

Applied the US Navy Fixed Wing Flight Training Squadron 27 (VT-27) markings.

Restoration Log of SUGAR 2.

1978 AMF Sunfish SUGAR 2 15 Jun 18 Rudder Cheek and Coaming

15 Jun 18:

The pintle on the rudder cheek was bent so we changed it out, then sprayed the aluminum rudder cheek satin black.

We tried a few test patches of the Kirby #4 Orange, it looks great! We thinned the paint for the coaming with about 5% Penetrol. George also has some conditioner on the way to us.

Log of SUGAR 2.