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.

1946 Chris Craft Brightside U22 Plywood Inner Bottom Skin Milestone!

1946 chris craft brightside u22 plywood inner bottom skin

Not much to say, or that I can say, other than, “Her bottom is skinned!”

What a huge milestone we have fading into our wake! Finally, John found the last sheet of Aquatek marine plywood, slathered the frame members with mahogany 3M5200 and began driving #6 x ¾” silicon bronze screws home.

Intermediate frame installation begins tomorrow, followed by fabricating chines and bottom planks.


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!

1953 22′ Shepherd Sportsman Fabricating Her Bottom Skin

1953 shepherd sportsman 110s fabricating bottom skin

Our goal, fabricating a true 5200 bottom on Shirley’s and my 1953 22’ Shepherd Sportsman, obliterated another milestone today, or I should say, John obliterated it.

When I arrived here way too early this morning, John was already well into patterning, and once again quietly demonstrating his never-ending resourcefulness and creativity, but let’s allow John to speak for himself on the clip. Enjoy!

favorite finishing tools, a monster Makita belt sander and our 48” horizontal belt sander. By lunch the starboard side was behind him and I was hard at applying multiple coats of CPES to the edges and both sides of all four panels.

I notice that John seemed uncharacteristically tense as he dragged his patterns to the port side of the bottom. If the boat is straight and true, he should be able to flop them down and enjoy watching them fall into place, fitting perfectly. His smile told the story. They did and do fit perfectly on either side. Our painstaking, and oft-times incredibly tedious work, first on the keel and then the frames, doing all we could to regain a true hull, something that was lost to her years of hanging from her lifting eyes with water up to her chines all summer, every summer.

By the end of the day, all eight panels have been liberally CPES’d.

Tomorrow we will begin scribing lines needed to locate each rib, and begin also installing the between-rib battens – think of a Chris-Craft hull – Shepherd expert, Phil Jones of Lynchburg, VA, urged that we do. These battens, together with the thicker ribs will render the bottom as stiff as she can be, and fully prepared for anything the dual-quad-four Hemi 331 delivers.

What a great day!