1954 Penn Yan Captivator: How to Seal Bottom Seams using Thixo Flex

1954 penn yan captivator seal seams

Sorry about the behemoth compressor firing up in the “background.” With five preservation projects fully engaged right now, I cannot simply shut the shop down when I shoot a video.

Finally, I am confident we have solved a chronic wood boat preservation conundrum, “My boat has an original bottom with open seams. I do not wish to, or in the case of a Striptite hull cannot, install a True 5200 Bottom. Nor do I typically drop her in the water where she lives all season. What are my options short of waiting for her to swell each time we launch and hope to use her?”

Hmmm …. Our stock answer has been, “Use Interlux Seam Compound for below water applications. It will remain elastic, compressible and able to withstand the swell-shrink cycle, even if the movement is miniscule, without overly compressing the wood on each side of the seam.” Save for two cases where a boat came back for new bottom paint and we found that some of the Seam Compound had become hard and brittle, I am still comfortable with it as a product that solves the problem. However….

OMG! Even when heated, it pays very, very poorly, and will fight you every inch of the way. What’s worse than all the time involved, Interlux recommends three applications.

There must be something better, especially in terms of ease and time cost of application.

I recently answered a query about the best material to use when sealing lapstrake topside strake seams with a small fillet. Our practice to date has been 3M5200, as long as the fillet is tiny, tiny in cross section, and any feathers beyond it are removed. One of you answered simply, “Use West G-Flex and you will be good.”

Hours and hours of subsequent research tells me that this person is correct. However, while two-part G-Flex is supplied in squeeze bottles and quart cans, Jamestown Distributors offers Thixo Flex, a TotalBoat brand version that is also two-part, satisfies G-Flex’s criteria for adhesion and lasting elasticity and is packaged in 10 oz. caulking tubes along with a mixing tip that delivers material in a fine stream that comes out having been mixed precisely.

Our tests, albeit only over several weeks rather than several years, and painfully small sampled, delivered a bond that is flexible and simply cannot be torn apart unless the wood fibers fail. After paying a seam’s worth, I use a super flexible putty knife to drive the material into the seam. (A plastic spreader may work as well, but I prefer the putty knife.)

The waste is scooped and spread into the next seam.

I should be able to finish the Captivator’s bottom spending about 2+ hours per side. Paying Seam Compound would take time measured in days, by contrast.

Once the Thixo Flex has cured, and after we’ve checked for any pin holes or holidays, we will sand the cured residue off the planks and seal the entire bottom with three full coats of Smith’s Clear Penetrating Epoxy Sealer.

Priming it with three coats of Pettit Tie Coat Primer 6627 will follow.

We must install the new transom bracing and transom before we can finish paying TotalBoat Thixo Flex into the bottom seams, however.


1938 Chris Craft Runabout Special: How to Seal Bottom Plank Seams

1938 chris craft sealing bottom plank seams

We continue racing against the March 21, 2017, deadline, the day I begin towing my 1938 19’ Chris-Craft Custom Runabout to Tavares, FL, and the Sunnyland ACBS Show.

We have applies the first five of an eventual twenty coats of Pettit Hi-Build Varnish have begun the process of varnishing her above the waterline.

Mickey Dupuis, Custom Metal Restoration in Holyoke, MA, is about half-way to restoring all of the hardware, including Flyin’ By’s long cutwater.

Her original bottom has our attention now. We tested about 50 fasteners, finding all of them rock solid tight. The red enamel, not bottom paint, yielded to the Circa 1850 Heavy Body Paint & Varnish Remover quite easily. Removing her original copper bronze paint was another matter, but, finally, we reached our goal, bare wood from stem to stern and chine to keel.

The planking, which is original to the boat, is in near perfect condition. No splits or cracks could be found. The inevitable dings and gouges have been addressed using 3M Premium Marine Filler.

This morning, and what is the topic of this video, we are focused on sealing her bottom seams using Interlux Seam Compound for Underwater Seams.

Seam Sealer must only be applied to wood that has been primed. The three coats of CPES also acts as an excellent primer for this purpose.

Filling each seam completely is the goal. Reaching that goal will likely involve at least two applications of Seam Sealer, done 24 – 48 hours apart.

The tools for this task are simple: an about 5’ x 8” piece of thin wood of some sort, a flexible putty knife, Interlux 216 Special Thinner as the solvent, and a quart of Interlux brown seam sealer. We have “only” 80+ feet of seams to fill… What fun!

1942 Century Imperial Sportsman: Why Filling Seams with 3M5200 Is Forbidden

1942 century imperial sportsman 3m5200 not seam filler

This morning’s 1942 Century Imperial Sportsman preservation project update is a plea, “Please, please do not pay 3M5200 into below-waterline seams.”

It is an adhesive, not caulk, pure and simple.

I have lost count of the number of otherwise wonderful woodies who arrive at the shop presenting curtains of old 3M5200 – stalactites – hanging from the bottom plank seams.

Once cured, 3M5200 will not compress when wetted planks try to expand. The result? Here is stark evidence of what happens next. The planks buckle and split, as several of them have in the ’42 Imperial Sportsman.

I have begun cleaning the seams using a curved pick and a reefing hook, supported by utterances that are for other than polite company.

As John noticed when he examined my growing pile of released 5200, “Most of this stuff never even adhered to the edges of the planks! Look at all the dirt and debris. So, not only did putting it in there buckle planks, it did not even work as an impediment to moisture infiltration!”

Right and right.

OK, what will we use in its place? I am opening seams that are up to 3/16” wide, which is at the outer limit of what it can bridge effectively, but we will use Interlux Seam Sealer for below-waterline applications. It cures, holds paint, and makes a watertight seal, but, even when cured, it never becomes hard. It compresses as the planks expand and expands if/when the planks shrink.

After applying the CPES and one coat of Interlux 2000E barrier coat primer, we will work up to three coats into the seams until they are almost fair with the planks. The wider seams may require more.

Some folks use Life Caulk for this purpose, a product I have used for bedding sailboat deck hardware, but never below the waterline, so I really do not have a view on its efficacy or appropriateness for this purpose.)

Then we will apply four more coats of the 2000E before we apply one coat of Pettit Tie Coat Primer and at least three of the deep, dark green topcoat our owner has approved. (Since she will be a trailer boat, We will likely reach for a paint like Interlux Brightside or Premium Yacht Enamel, unless we can find a gloss hard bottom paint.)

1952 Chris Craft Riviera How We Fill Deck Seams

1952 chris craft how we fill deck seams

As one of my guys loves to say, “She’s coming into it now.” The 1952 Riviera runabout’s seams will be Sikaflexed by this evening, painted by Thursday and begin wearing her hardware next week.
We use white Sikaflex 295 UV, followed by high-gloss Total Boat Wet Edge topside paint.
As RJ is Mr. Varnish, John is the guru of filling seams. Not surprisingly, as is the case with most everything else in delivering finishes to die for, it is all about preparation. It took John most of an afternoon to tape the aft deck and covering boards, and all morning today to tape off the foredeck.
Why so long? Every edge must follow the seam’s shoulder precisely. Using a utility knife blade and incredible patience, John slices slivers of tape away so that all arcs are perfect and all straight lines are exactly straight.
He will be doing the ’46 Gar Wood Ensign once we apply the final coat of Pettit Hi-Build gloss varnish.

How to Caulk Seams With Cotton Roving – Palmer Launch Roxanne

vintage boat caulk seams cotton roving

Carvel planked construction leaves spaces in the seams between the planks that are traditionally caulked with cotton caulking. Here I am about one-third finished caulking Roxanne’s topsides, and share how I go about this process with you

The tools are very low-tech: two caulking irons, a plastic-headed hammer, a smallish plastic pail and a hank of rope. The cotton caulking arrives packed in one-pound packages of loosely coiled “rope.”

Before the caulking begins, I roll the cotton into balls somewhere between a large orange and a small grapefruit in size. After dropping a couple of balls into the bucket, hanging it around my neck, I grab the hammer and sharper, smaller of the two irons and proceed with step one of stuffing the seams with cotton caulking.

The goal in this first step is to create what looks all the works like braided rope. The cotton passes through the palm of my hand and beneath the iron, as I successively capture approximately one-inch-long lengths against the plank below the seam, slide it up into place and drive it home with a couple of taps of the hammer. It is amazing the rhythm that begins to take hold: grab, slide, tap, tap; and over and over until the entire length of the seam is filled. Then, using the blunter, wider iron set at an angle, I attack the “rope” and drive it home until the cotton disappears into the seam.

Once all seams are filled, the cotton and edges of each seam must receive a copious coat of oil-base paint, preferable one that is consistent with whatever the final topside paint will be, We will use Interlux Pre-Kote on Roxanne since our topcoat will be Interlux Premium Yacht enamel 220 — semi-gloss white.

Before we can begin our finish painting, however, we will fill and fair all of the seams using Interlux white Seam Compound above, and Davis Slick Seam below the waterline.