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Wednesday, April 08, 2009

Deck Bonding: The Messy Details

To skip the words and go right to the pictures, click here. A little background, in case you just tuned in. We are latest owner (third we think) of this Westsail 42 project that was one of the original "kits". These kits could be purchased in various stages of completion from Westsail Corp. targeted at those who wish to live the "boatbuilding lifestyle" (let me tell you it is very glamorous). This particular kit, #60, appears to have been sold as one of the barest of the kits. It came as hull, deck (unattached) and some spars. There probably were more original parts like rudder and pulpits, but those were likely lost/sold/stolen/who knows, over the past two owners. What we are dealing with...
From Building A Westsail 42: Bonding the Hull and Deck
The deck joint is of the type where the edges of the deck simply rest on a fiberglass flange that runs the perimeter of the hull. The flange was constructed when the hull was laid up by simply "pulling away" the last couple hull laminates to be perpendicular to the toerail. It was reinforced on the top surface with mat and fiberglass rope was run all the way around the perimeter. Finally, it was trimmed to about two inches wide. The deck was then placed atop the flange and tacked in with a few tapping screws and that is how the hull/deck was delivered. It has been like that for the last 30 years. Recently, as build out of the interior has progressed, we reached the point where the underside of the deck joint would soon be covered up with interior framing and cabinetry. This prompted the bonding of the deck. Not knowing how heavy the thing was, I thought through various ways to elevate the deck till I just tried something that worked. This involved a 10 ton hydraulic floor jack, and two bottle jacks. The Planning...
From Building A Westsail 42: Bonding the Hull and Deck
Once we successfully raised the deck, we started planning how to do the bonding. The original Westsail 42 construction manual specifies fastening with about 200 1/4-20 stainless bolts and sealing with a polysulfide sealant/adhesive (an example would be 3M 101 adhesive/sealant). Now, we are always hearing about "leaky deck joints" on boats from this same era, so in order to minimize that chance we decided to "one up" the factory so to speak. We went up one size on the thru bolts to 3/8-16 and sealing with 3M 5200 (a polyurethane adhesive/sealant which is stronger and more permanent than the polysulfides. It doesn't stink as much either). The Work...
From Building A Westsail 42: Bonding the Hull and Deck
Over the years, either the hull has "drooped" outward, or the deck has "shrunk" inward, or both, as there was significant gap (as much as 1/2") between the edges of the deck and hull. Maybe that is how it came from the factory, who knows. Through some trial elevations we centered the hull on the flange as best as possible. Using clamps made of plywood we "pinched" bulwark to help close the hull/deck gap. From there we centered the T-Tracks and drilled/countersunk holes and set backing plates (see earlier posts). Deck Bonding: Day 1
From Building A Westsail 42: Bonding the Hull and Deck
On the first day of the "home stretch weekend" for bonding, we blocked up the deck about six inches to access the inside of the bulwark in order to spot/mount the lifeline stanchions purchased earlier from Worldcruiser. We glued and threaded in the backing plates behind the stanchions using 3M 4200 Fast Cure, so as to be sure it set up before the following day. Deck Bonding: Day 2
From Building A Westsail 42: Bonding the Hull and Deck
Took a grinder to the edge of the deck to give it a nice bevel so the 5200 had a nice place to 'seal'. With warm water and detergent, scrubbed the top and underside of the hull/deck flange. It had accumulated some 30 years of dirt. We had to change the water at least five times. Once dry we wiped it down with acetone to make sure it was really clean. Deck Bonding: Day 3 With the deck raised and better access to the top of the bulkheads, I took the opportunity to clean up and tidy some previous glasswork. My wife did a final vacuum of the hull sides of dust from the drilling of the holes. Followed with an acetone wipe on the inside underneath the flange and finally taped a drop cloth around the perimeter to catch any sealant the might squish out and fall on the inside. That afternoon, we started squirting 5200 onto the flange using an air powered caulking gun (totally beats battery powered or manual guns!).
From Building A Westsail 42: Bonding the Hull and Deck
Two hours and eighteen tubes of 5200 later, we had the flange all "gooped up".
From Building A Westsail 42: Bonding the Hull and Deck
Now comes the tricky part. We must lower the deck such that the previously bored holes line up PERFECTLY. While the 3/8" holes for the thru bolts were bore slightly larger for wiggle room, the 5/16" holes for the T-Track were not. Those need to line up perfectly so the bolts can be threaded onto the backing plate already beneath. With the deck lifted on three points, gravity did shift the deck slightly. The very peak of the bow was the gauge for determining alignment. If the deck mated flush with the filler on the flange, we were ok. The first drop, bow only, came up short. Deck shifted about half inch aft. Bow was lifted again. Push forward on the inside of the deck (with support only on three points, it was easy to push, but difficult to control the 1000+ lbs of deck). Drop again. Too much. Overshot forward by about an inch. Lift the bow again and push back shimming the cabin sides against a bulkhead to limit the movement. Drop. Perfect!
From Building A Westsail 42: Bonding the Hull and Deck
Third time is a charm, right? Well, not yet. Checking the hole indexing on the side T-tracks showed the aft had shifted sideways about a quarter inch. Back up she goes. This time, pushing on the sides to shift it to port. Drop. NOW she's perfect. The fastening now begins.
From Building A Westsail 42: Bonding the Hull and Deck
We start with the T-track bolts. The same 5/16" steel bolts used to temporarily preset the T-tracks are threaded with washers, sans t-track. Most bolts thread ok. A few more backing plates fall away on the underside due to poor adhesion, but the bolts pass thru without problem (the most important thing). We can always reset the backing plates. From the aft t-tracks, we move backward with the 3/8 bolts and "washer nuts" I baked earlier. Me on the underside with the 9/16 socket and ratchet extension, my wife topside with the cordless driver. One-by-one all of the thru bolts went in around the stern without a problem. Now forward of the t-tracks. Starboard side. Each bolt goes in pretty well, clamping the joint as needed, until we get forward of the head. There, the bulwark gets "deeper" and the slope of the hull more extreme such that you can't get your hand up inside. Furthermore, the slope of the bulwark and the straight socket extension is such that you can't line up the nut with the bolt to start the thread. We try switching roles with my wife below starting the thread as she can get up in there with her smaller hands. This was more successful than my attempts, but still difficult. It was dark and 11pm. Frustrations were high, and all this time we wondered how the hell did they do this at the factory?! We decide to sleep on it and leave the forward bolts unfastened till the following day. 3M 5200 remains soft and tacky for 48 hours and it doesn't fully cure for at least seven days, so it is not like this is a race against time. Deck Bonding: Day 4
From Building A Westsail 42: Bonding the Hull and Deck
I get up and check into the day job to tell them I wont be in and head to the hardware store to find ANY sort of tool that might help fastening these forward bolts. I pick up a number of 1/4 inch drive extensions and flexible hex driver extensions, and, the tool that saved us: a 1/4 inch drive 9/16 socket on a u-joint! The wobbly nature of the u-joint should allow me to come at the bolt from an angle, yet still align the nut correctly with the bolt to start the thread. Back to the boat, we resumed the fastening. With the new tools, nuts went on smoother and faster than the night before. By lunchtime, we had all fasteners installed except one at the very front. The length and angle of the bulwark at the front is just too extreme to even touch, let alone see, the bolt itself. Even with a mirror, never mind the cramped space to work in at the bow. That is where the ONLY tapping screw was installed. The rest of the day was spent scraping off the excess 5200 that squished out from the joint and smearing some on the tops of the thru bolts to seal them nicely.
From Building A Westsail 42: Bonding the Hull and Deck
The day finished with cleaning up the 5200 that by now was on EVERYTHING. The major players for this project
  • me and my wife
  • 18 10 oz tubes of 5200
  • about 260 bolts, nuts and washers
  • air powered caulking gun
  • various 1/4 drive sockets and extensions
  • boxes of disposable gloves
  • three hydraulic jacks
From Building A Westsail 42: Bonding the Hull and Deck
Final Words No more do I need to keep plastic over the joint to keep the water out. No more will there be little bits of water accumulating in the bilge that I must manually siphon or vacuum! The boat is now a significant step further to being seaworthy (except for the big hole where the prop shaft goes, lol). The first test of this craftsmanship will be pressure washer weekend in a few weeks. We will see just how water tight things are then.
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