Sanding, Fairing & Tabbing

April 22, 2019

I returned to the Allied 24 after a week off of all work - taking my daughter on a few days of vacation - and got straight into more sanding (no surprise).  I began with sanding the cockpit locker hatches.  Since I had water-washed them in the previous work session, I grabbed the 5" ROB sander and 80-grit paper, and then proceeded to sand the surfaces to fair.

The cockpit locker hatches are roughly 90% complete (ready for primer paint), and will be finished within the coming week...at least set to the side and ready for primer paint.

The next task I had on the list today was to complete a small amount of tabbing on the forward side of the bulkhead (to both port and starboard) that was set to support the cockpit well.  Its location was roughly in the middle of the cockpit well, when viewed lengthwise.

The first step was to vacuum and solvent-wash the previously sanded surfaces.  I then mixed a small amount of epoxy resin and painted it onto the surfaces to be tabbed.  Next, I mixed a pot of thickened epoxy and applied fillets to the transition between the bulkhead and hull.  The fillet, a curved radius, would allow the fiberglass tabbing to lay down without any voids persisting in the laminate.

Before I applied the epoxy resin to the surfaces, I had measured for the length of tabbing material: 24" on the starboard side, and 16" to port.  Back in the shop, I removed the roll of 6" tabbing from storage and cut the 24" and 16" lengths.  With the fillets in place, I wet out the lengths of 6" tabbing (1708 biaxial) on scrap pieces of cardboard, and then carried them to the boat.

One at a time, I applied the tabbing to the bulkhead and hull surfaces.  I carefully pushed out the air bubbles to ensure a maximum-strength bond.

To finish off the tabbing, I applied a length of peel ply fabric.

The peel ply would reduce the amount of water-washing of the amine blush and sanding required for secondary, mechanical bonding of epoxy-based primers (to come very soon).  There would be a bit of sanding here due to the imperfect application of the peel ply, but greatly reduced nevertheless.

With the tabbing chore out of the way, I brought the 5" ROB sander and vacuum to the deck of the boat for a round of sanding, but first I needed to make my way around the boat with the scotch bright pad to water-wash the amine blush from the previous filler application.  I methodically made my way around the boat, scrubbing and drying the filled surfaces as I went.  Satisfied, I then began the sanding rounds...5" ROB with 80-grit discs.  There were a number of tight radius curves, so I elected to utilize the 5" sander to allow for maneuverability.  The sanding took the bulk of the time today, and even required a fair bit of hand sanding, but always results in a pleasing product.

With the sanding of the deck complete (for this session), I vacuumed the surfaces and solvent-washed them to remove any remaining sanding residue.  I had a few larger areas to tackle...to further fill with thickened epoxy.  If you are a new reader, for most jobs I thicken the West System epoxy resin with 406 colloidal silica and 407 low-density filler.   I began on the aft deck, and applied to the ongoing repair of the lazarette hatch frame.  A huge chuck had been cut out of the forward-port side of the hatch frame, and through previous work sessions I had built up the hatch frame using a combination of 1708 biaxial cloth and thickened epoxy.  I applied another round of thickened epoxy to bring the repair into the same plane as the balance of the hatch frame.  I also applied additional skim coats to the old mainsheet traveler track fastener holes - just forward of the hatch frame.

Next, I moved to the coach roof around the companionway hatch.  The slide hatch frame fastener holes had been addressed in a previous session (grinding tapers and generally opening them up for more surface area for the epoxy resin to bond to), so all that was left to do was apply thickened epoxy to fill them in.

Finally, I moved to the forward hatch, and applied more thickened epoxy to the concave surfaces (voids, chips, and ground out holes); sanding and fairing these repair areas would follow next.

Total Time Today: 5.25 hrs