How to Install Bottom Battens in a True 5200 Bottom – 1938 19′ Chris-Craft Custom Runabout

1938 chris craft runabout bottom battens

As is typical of all Chris-Craft utilities and runabouts, this 1938 19’ Chris-Craft Custom Runabout, Flyin’ By’s hull is comprised of a series of heavy frames to which the bottom is fastened. A series of battens run athwart between the frames, thereby adding substantial stiffness to the bottom.

Simply put installing battens is a thankless, two-person challenge. Here are the steps for installing one batten at a time, followed by filling the countersinks, fairing the bottom, sealing, priming and applying bottom paint. The process is described for one batten, one that will be repeated for all of them:

Installing the Battens.

  • From the inside, drill two pilot holes towards the ends of the batten. • Using a straightedge and pencil, scribe a line between the pair of holes.
  • Drill holes along the line, about 1.5 inches apart using a countersink pilot drill.
  • Dry fit the batten and, while the guy underneath presses it in place, drill two holes from the outside in through two of the countersinks.
  • Sink screws through those two holes. We use #6 x 1 or x 1-1/4, depending on the thickness of the inner plywood skin plus the exterior planks.
  • Stand the remaining screws through the remaining holes and drive them home.
  • Release all of those screws for now.
  • Butter the batten’s bottom face about 1/8” thick with 3M 5200 – mahogany.
  • Hand it to the guy beneath the boat, who presses it in place.
  • Starting with the two end screws, and remembering to stand screws in all of the holes, drive all of them in place. (Standing the screws in the holes first ensures that fountains – volcanoes? – of 5200 do not squirt though the other screw holes as you work along the batten.)
  • Repeat for all battens on both bottom faces. Flyin’ By has twenty of them per face.

Filling Countersinks and Fairing the Bottom.

Filling countersinks and fairing the bottom is next. We use 3M Premium Marine Filler, available from Jamestown and elsewhere, to fill and fair the countersinks.

Three applications are required. We sand using 80 grit and one of our Festool random orbit sanders after the first coat, just to knock down ridges and what I call overspread.

Once the last application has cured – about 4 – 6 hours – we sand the entire bottom fair using 80 grit on our pneumatic longboard sanders. Declivities may show themselves at this stage, which requires interrupting the sanding as Premium Filler is applied to them. Sealing, Priming and Bottom Paint.

Once the bottom is fair, apply three coats of Smith’s Clear Penetrating Epoxy Sealer. Danenberg recommends applying the second coat immediately after the first, so we apply the CPES to one entire face and then return to where we began and apply a second coat.

I know there are other penetrating sealers available, and we’ve tested most of them. Let me just say that we use Smith’s CPES, which is available at good prices from Star Distributing in West Mystic, CT:….)

Our go-to primer is Interlux InterProtect 2000E Two-Part Barrier Coat Epoxy Primer because it works

From Jamestown:

Interlux’s Micro-Plate formula creates an effective barrier against water permeation. 2000E may be used above and below the waterline as a universal primer for all surfaces. It is also an excellent primer for all metals and can be used as part of a no sand system.

From Interlux:

  • Two-part epoxy water barrier with Micro-Plates
  • Up to two weeks is allowed between coats of 2000E
  • Now available in two colors, Gray and White
  • Fast drying, easy application
  • Sag resistance to insure the elimination of sags and runs during application

Technically, InterProtect Micro-Plates provide millions of overlapping microscopic plates that create a barrier similar to shingles on a roof. These overlapping Micro-Plates eliminate any direct path for water migration and also improve the sag resistance of the epoxy making application easier.

We will have a gallon each of gray and white 2000E on hand for Flyin’ By’s bottom and chine plank – boot stripe included. Once we’ve applied five thin coats, we will have created an impenetrable barrier against water permeation.

Since Flyin’ By will be dry sailed by her new owners, we will apply three coats of Pettit Old Salem Copper Bronze Hard Racing Enamel, at which point she will sport a True 5200 Bottom.

Finally, she was in show ready condition, with over 20 coats of varnish having been applied and buffed when the moment to flip her arrives. No matter how careful any of us is, and no matter how many pads we placed strategically, Flyin’ By is heavy, and her hull shape presents long sweeping curves. And with three of us working around, under and even atop her, bumps and bangs are all but inevitable.

That said her varnish is scuffed in several places, so we will sand the entire hull flat anew and apply three or so coats of Interlux Perfection Plus Two-Part Varnish to her, and let it clear before she returns to storage.

How to Install Bottom Planks in a True 5200 Bottom – 1938 19′ Chris Craft Custom Runabout

1938 chris craft runabout install bottom planks

Installing the bottom planks can be tedious and is fraught with all manner of challenges.

First and foremost, unless the planks are dry-fit so that the seams between them are of uniform width, you will all but certainly experience and “Oh X$#%^!” moment when try to install the final, chine, plank.

I cannot tell you how many bottoms we’ve encountered that sport the telltale “skinny plank” along the chine. Failing to fit first, mark the edge of each plank heavily and then obey the lines usually translates into a super wide seam, sometime over an inch, and a plank that does not fit at the stem.

Once again we drop screws part way into all of a plank’s holes before setting it in place, and screw each of them in only part way thereafter. Once all the screws are down far enough that the shanks are in the plank’s holes, begin driving them home. (We work from the middle out, but given how narrow the planks are, you can also work from either, or both ends towards the middle.)

When you clean excess 5200 – that which squeezes out – work towards to ancillary goals. Keep the countersinks free of the 5200 so that the 3M Premium Marine Filler can make a purchase on wood, not on slipper adhesive. And, be sure that all seams are filled fair with 5200.

Clean with Interlux Brushing Liquid 333, and then wipe everything down with acetone, which will accelerate the curing process.

Finally, be patient. I do not care what Interlux says, 5200 can have a mind of its own around curing.

Sometimes waiting 2 – 3 days are fine, but we wait longer, at least a week, before we go at the bottom with sandpaper.

You will be helped with being patient as the countersink filling and bottom fairing process is might time consuming when done correctly. Remember, whether it is 3M Premium Marine Filler or some other fairing compound of your choosing, it shrinks as it cures. You want every countersink filled fair to the plank surface. Apply it twice and then sand everything as smooth as you can with 80 grit – no finer, before applying it a third time and sanding again.

Even though the planks were dosed with three coats of CPES before installation, you have likely sanded into the sealed layers, so applying three more coats is not overkill.

We prime all bottoms with five, not three or four – coats of Interlux 2000E Barrier Coat Primer before applying Pettit Hard Racing Copper Bronze Bottom Paint – three coats.

How to Install the Inner Plywood Skin in a True 5200 Bottom – 1938 19′ Chris Craft Custom Runabout

1938 chris craft runabout inner plywood skin

Actually installing Flyin’ By’s True 5200 bottom begins today.

After cutting and fitting all of them, we applied three full coats of Smith’s Clear Penetrating Epoxy Sealer (CPES) to both surfaces and the edges of the 4 mm Aquatek meranti marine plywood panels.

Once the CPES was cured, three coats of Sandusky Chris-Craft Mahogany Bilge Paint were applied to the inner (bilge) side of each sheet.

We are installing those panels bedded in 1/8-inch-thick layer of Mahogany 3M5200 and secured with #6 x ¾” Frearson (Reed & Prince) silicon bronze screws.

This install is a multiple-step process

  • Lay each panel down dry – without any 5200 – and scribe lines running through the center of each frame.
  • Pre-drill, complete with countersink, all of the hole we will drive the screws through.
  • Apply a solid, 1/8”-thick layer of 5200 along each frame and the landings along the keel, chine and transom (in the cast of the aft-most panels).

The layers spread on the landings are a generous 1/8”, especially along the seams between the panel edges and the landings. Doing so produces amble squeeze-out, which, when cleaned with Interlux Brushing Liquid 333, leaves a complete seal.

As Danenberg admonishes, scrimp on 5200 and you end up with a shortcut bottom that will not last. We will apply in excess of one hundred tubes of 5200, which works out to about five tubes per foot LOA, for Flyin’ By’s True 5200 bottom.

  • Use a plastic spreader to essentially “frost” the beads of 5200 into a uniform layer.
  • Lay the panel in place and begin inserting screws.
  • Do not drive and of the screws home until all of them are driven about halfway down. Why? We know by bitter experience that driving the screws home from any edge or other starting place ensures creating fountains of 5200 up and out of the empty pilot holes that lie ahead of you. Inserting all of the screws halfway ensures zero fountains and a much more pleasant experience.
  • Drive all the screws home.
  • Clean all of the squeeze-out inside and out with Interlux Brushing Liquid 333.
  • Wipe all seams and any visible 5200 down with Acetone, which accelerates curing.

Once all the panels are installed and we’ve allowed the 5200 to cure for several days, it will be time to install the mahogany bottom planks. (Remember, all of them received three full coats of CPES – both faces, the edges and the butts – after releasing and cleaning them.)

Then it is time to fill the countersinks with 3M Premium Marine Filler and fair the bottom to be absolutely fair from stem to stern and chines to keel.

Next comes three more coats of CPES before we apply five coats of Interlux 2000E Barrier Coat Primer, and then three coats of hard racing bronze bottom paint.

How To Remove Bottom Fasteners in a True 5200 Bottom – 1938 19′ Chris Craft Custom Runabout

1938 chris craft runabout bottom fasteners

That Flyin’ By’s bottom was original to the boat is absolutely certain. How do we know for sure? After stripping her bottom’s port face bare, and finding nothing but an original inner layer of 3/16” mahogany laid on the bias, we inspected each frame searching for any evidence of extra screw holes or holes that had been filled during a bottom replacement. No such evidence exists.

Additionally, save for the aft garboard planks, the screw pattern, their sizes and lengths are precisely consistent throughout both bottom faces. The substitution of bronze Reed and Prince fasteners for the original brass slot-headed fasteners tells us that both aft garboards were removed and then reattached at some point.

Nowhere is there any evidence that the inner layer has deteriorated or been replaced. What remains of the original canvas interlayer is somewhere between some and none. Additionally, the original brass screws have been replaced along the keel edge of both forward garboards.

The aft garboards – the #1 planks – and the next ones outboard – the #2 aft planks – lie immediately beneath the engine and transmission, and are sufficiently oil-soaked that their ability to hold 5200 and paint is at best suspect. They must be replaced.

The balance of the original bottom planking is as hard and as sound as the day it left Algonac, MI in 1938. Releasing the screws fastening the bottom is a four-part sequence

  • Using a 3/8” Rotabroach cutter and electric drill set at high speed, drill each countersink until you hear the telltale sound of the steel cutter grinding the head of the brass or bronze (or stainless) screw. Take care here. The Rotabroach is designed for grinding off excess spot weld. The cutters are super hard and super sharp. Applying too much down force or grinding for too long risks rounding off the screw’s head and erasing its driving slots.
  • Reach for a sharpened awl and clean each countersink, paying particular attention to the screw’s slot or R&P driver. Grind through these and you will “enjoy” extracting the screw using one of the damaged screw extractors available today.
  • Blast all residue out of the countersink with an air chuck and compressor delivering at least 110 PSI. (That’s why wearing safety glasses are absolutely required. The particles erupt from the countersink with surprising force.)
  • Using either a slot or R&P driver inserted in a variable-speed impact gun, carefully and slowly tease the screw as it begins backing out of the wood. Trigger control is critical lest you want to destroy the screw’s head and be reaching for the damaged screw extractor.

Voila’! One screw is released. You have only hundreds and hundreds and hundreds to go!

Every screw I’ve released to this point was dropped into a plastic paint pail that now weighs over 20 pounds!

Only a hundred or so to go…

How to Open Countersinks and Remove Fasteners from the bottom of a 1938 19’ Chris-Craft Custom Runabout

1938 chris craft runabout countersinks fasteners

We clean fastener countersinks using a Blair Equipment 11090N Rotabroach Cutter Kit, which is available from (…)

Yes, even if a plank will be reused and is filled with either a wood or putty, we remove its wood bungs, but in this application always choose a cutter that is smaller than the diameter of the bungs being removed. The cutter bores through the bung without touching the countersink’s edges and is then cleaned using one of the awls we have on hand.

We are much less careful when releasing failed planking, and often use a cutter one size larger than the diameter of the countersink. The goal here is removing the plank without breaking it so it remains available to patterning.

The air chuck is key here, as RJ demonstrates in the clip. With our compressor set at 110 PSI, the chuck delivers a concentrated blast of air that (almost always) leaves the countersink bereft of waste material.

Finally, if you have a super steady hand, as RJ does, you too can back the screws out with an impact gun, not a hand screwdriver.

When stripping a bottom, be sure to remember RJ’s admonishment. Climb beneath the hull, or down into if she’s not flipped yet, and number the intermediate frames, sometimes referred to as battens.

While we will bed them in 3M5200 during final assembly, they are originally installed by driving screws from outside the hull, through the external planking and inner skin, and into the batten without any adhesive applied to the batten or inner skin.

Numbering these battens before they’ve dropped to the floor and skittered about will save endless time and frustration during reassembly.

1946 Chris Craft Brightside U22: How to Plank Bedded in 5200

1946 chris craft u22 plank bedded in 5200

Bedding the bottom planking in a 1/8” thick layer of 3M5200 without making a huge mess and without creating even more work cleaning it up, is perhaps the most critical component of the last “woodworking” step in fabricating a True 5200 Bottom.

Yes, I know we have covered this topic earlier, but it bears repeating. “Frosting” the plywood inner layer with a full 1/8” thick layer of 5200 is critical, as doing so ensures that there are no voids, and that, when fastened down, the squeeze out will fill the seams between the planks.

Fill the seams, yes, but do so without also filling the fastener countersink, as fairing the surface once the 5200 has cured requires that the countersinks be filled with 3M Premium Marine Filler.

Every, and I mean every spec of 5200 must be removed from the countersinks once the fasteners have been driven home.

Our method results in minimal infiltration of 5200 into those countersinks. You will need multiple cases of 5200 on hand. Use mahogany 5200 for forward planks that run upward through the waterline. White, which is much less expensive, if fine elsewhere. My rule of thumb for estimating cases needed is 40 – 60 percent of Length Overall (LOA). Since beam, and therefore the width between chines grows with LOA, I plan on closer to 60 percent for a 22-foot boat like this U22. (I am planning to use 12 cases for her.) In response to the many questions the community has sent my way, here is the “chronology” followed at Snake Mountain Boatworks: • Dry fit and fasten all of the planks with a dozen or so fasteners each; • Drill every pilot hole/countersink now; • Remove the planks one at a time, starting at the keel; • Using a permanent marker, draw an outline of each plank – one side and the butt – before it is removed; • Use these outlines to guide frosting one plank area at a time with a 1/8” thick layer of 5200; • Have at least four boxes of latex or, better, nitrile exam gloves and have a large garbage can nearby; • Apply the 5200 using a pneumatic caulking gun in a closely spaced squiggle pattern; • Spread the squiggles into a uniform layer using plastic spreaders; • Lay that one plank in place and begin inserting silicon bronze wood screws by hand, sinking just enough of them as you go to hold the plank in place; • Begin at the forward end of the planks terminating at the stem, using the length of that plank as the lever to slowly bend it into the correct shape; • Once there is a screw in every pilot hole, each of which has been screwed about 90 percent of the way home, drive all of the screws home; and, finally • Make a first pass using plastic scrapers along the plank’s open edge, and along its seam with the previously-installed plank, scooping all the squeeze out from the surface; • Using Interlux 333 Special Liquid – sometimes called special thinner, and lots of rags, clean and clean and clean until all squeeze out is gone. Time to install the next plank ….

1946 Chris Craft Mahogany U22 Bottom Planking Fabrication

1946 chris craft u22 bottom planking

Our 1946 Chris-Craft Mahogany (Brightside) U22 project enters the bottom planking fabrication stage today.
We will replace all existing planking, which is mostly cedar, with newly fabricated mahogany.

Yes, we abhor being unable to save the original planking, but most of it is just too oil-soaked, split and broken. Not replacing these planks means a bottom that is not well adhered to the 3M5200, and cannot hold paint from amidships aft.

John and I are dry fitting the original planks in place, and will scribe them on the plywood skin. Given the structural work this hull has received, especially removing the twist and hog from it, means that some of these planks, and especially those running to the stem, must be sanded in to fit.

Once we are confident we have a perfect set of pattern planks, we will scribe them to new mahogany.

The new planks’ faces and edges will be thoroughly sealed with CPES before we begin laying them down.

Following a final application of CPES to all exterior surfaces, we will begin applying the first of five coats of Interlux 2000E barrier coat, followed by three coats of period-correct blue antifouling paint.

1946 Chris Craft U22 5200 Bottom Assembly is Launched!

1946 chris craft U22 5200 bottom launch

Let the True 5200 Bottom assembly begin! It has been a long winter, but, finally, all of the structural work is behind us. Today begins the final steps in giving this 1946 Chris-Craft Brightside U22 a True 5200 Bottom.

We begin at the transom and work forward, which allows us to make huge strides right away. Once we’ve installed the first two sheets of Aquatek Marine plywood, we are at least 80 percent of the way to the bow.

Using our pneumatic caulking guns. Ribbons of mahogany 5200 are applied to the frames and bottom landing on the keel. Then, using 7/8” strips of plastic caulking spreaders, we carefully “frost” the surfaces with enough material so that there will be a bead of squeeze-out visible along the frame-plywood seams in the bilge. (ACBS judges have been known to penalize boats sporting no leak bottoms that have no visible squeeze-out. Why? The absence of squeeze-out signals the possibility of an incomplete seal between the frame faces and the plywood.)

We have learned not to apply a ribbon of 5200 to the chine frame face. Rather, there is always surplus material available as we smooth the 5200 along the frames. The chine frames offer a perfect depository for this surplus, which also greatly reduces waste. (The other reason involves the risk of T-shirt bottoms draping and dragging in 5200, which will NOT come out in the wash.) Once all of the surfaces have been frosted, we carefully lay the sheet in place, being sure to pound it flat. You will notice that the fasteners sunk into the frames are one 8” to 12” centers. Our goal here is securing the sheet until the 5200 cures. We will be sinking screws through the external planks on about 2” centers when they are installed.

Finally, and most unpleasant, is the task of cleaning, cleaning, cleaning the excess 5200 that squeezes out around the edges of the sheet. Our go-to solvent here is Interlux Brushing Liquid 333, which liquefies the 5200 and allows us to wipe it away. (Yes, we ruin lots of old shop towels in the process.)

Then, since the 333 tends to retard curing, we make a final pass along all of the beads of 5200 with a rag soaked in Acetone. The Acetone both removes the 333 residue and contributes to accelerated curing.

We are on our way!

1946 Chris Craft Brightside U22 5200 Bottom Patterning

1946 chris craft brightside 5200 bottom patterning

OK, we’ve received a myriad of questions about how, once the hull is ready, we go from 4’ x 8’ sheets of Aquatek Marine Plywood to the inner skin of our True 5200 bottoms. John shares his “tricks of the trade” in this clip.

Once John has fabricated all of the pattern pieces for one face of the bottom, tension builds. If we have done our work well and the hull is true stem to stern and port to starboard, once flipped to the other face, the panels will fit perfectly.

Today they fit within 1/16 – 1/8 inch, which is excellent, given that we began with a corkscrewed, hogged hull. Phew!

Once we have fabricated all of the component pieces, which we dry screw in place so we can ensure an absolutely perfect fit, we release them and begin prepping them for installation.

Each sheet will receive 3 heavy coats of Clear Penetrating Epoxy Sealer (CPES). [Yes, as Danenberg prescribes, the second coat is applied immediately following the first coat. We then wait 24-48 hours to apply the third coat and give it 48 hours to cure.

Once they are sealed, the inner surfaces will receive a heavy coat of Sandusky Paint Company Chris-Craft Red Bilge Paint, and we will begin installing the skin, piece by piece, heavily bedded in 3M5200.

Before the plywood begins going down, however, we will ensure that all mating frame surfaces have received one light coat of the same bilge pain – again following Danenberg, By this time next week, plywood should have replaced construction paper.

Happy Saint Patrick’s Day!

1959 Chris Craft: How to Install Bottom Planking When Fabricating a 5200 Bottom

1959 Chris Craft fabricating 5200 bottom

I have had several requests for a video showing our crew installing the bottom planks into a bed of 3M5200.

Here it is. Using the 1959 17’ Chris-Craft Sportsman as our “lab rat,” John and RJ share some of the tricks we have learned that help us ensure a complete seal between the planking and the plywood outer skin, and, what in some ways is critical, that the 3M5200 ends up where we want it without suffering hours of misery cleaning the 5200 off places it does not belong – in countersinks, oozing between the planks, and – horror of horrors, dripping down the topsides.

First and foremost, as Danenberg urges to all who will listen, scrimping on the 5200 translates into a shortcut 5200 bottom that will not last. Lay it on … thickly. We lay down at least 1/8” to 3/16” of the goo. Yes, that translates into a huge number of very expensive tubes of 5200, probably at least 60 for the layer between the inner plywood skin and the bottom planks in this case of this 17’ hull. And, yes, you will end up removing lots and lots of the stuff where it squeezes out through the seams. But, as is so trite, but also so true, price and cost diverge quickly here. A proper 5200 bottom means investing in mountains of 5200. Do it right, however, and you have a bottom that will last many decades. Take the shortcut route and, well, you might well experience the pain and suffering of removing a failed cheap alternative.

And, not Life Caulk, which is fantastic when used for its intended applications, cannot be substituted to save money. It’s cheaper now for sure, but oh so much more expensive in the long run.

We use blue painter’s tape to keep the 5200 away from adjoining planks and also the surface of the plank being installed. You will see how in the clip.

We learned the hard way what a disaster we and you will have on your hands if the 5200 pushes up through empty pre-drilled fastener holes. The silicon bronze fasteners, the drill bit, the disposable gloves, and the plank’s surface end up hopelessly befouled by 5200. Yes, it can be cleaned using Interlux Brushing Liquid 333, but why put this horror show on you when a technique John and RJ developed absolutely ensures no fountains of 5200 rising through fastener holes?

As with so many super creative and completely intuitive solutions, this one is trivially simple. Sink a fastener in each hole, but stop just short of driving it home. The fastener head will have seated in its countersink just enough to act as a seal. No 5200 can squeeze by.

Once all of the fasteners have been sunk in this manner, a crew member begins at each end of the plank, driving them home. As is illustrated in the video, yes, there is squeeze out, and lots of it, but the escaping 5200 lands on the blue tape, not the wood, or the screws or the gloves, well, not so much on the gloves.

Once every screw has been driven home, the squeeze-out is scooped off the tape using a combination of a plastic scraper and a simple wood paint stirring stick. Having removed all of it, we simply pull the tape, leaving an almost clean surface.

Using Interlux Brushing Liquid 333, we then scrub everything absolutely clean. However, the 333 actually retards 5200 curing, so the final step involves wiping everything down with Acetone.

C’est finis!