This update continues following as we install the starboard bottom planks to our 1946 U22.
Notice the blue painter’s tape we use to mask the seam edge of each installed plank.
Doing so allows the squeeze out from the seams flow onto the tape rather than an already-cleaned and fully-installed plank. We have one partial and one full plank left to install on starboard. We have consumed a bit over 5 cases of 3M5200, four boxes of nitrile exam gloves, 2 gallons of Interlux 333 and over 1,000 fasteners by this point.
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 ….
Haven’t seen it snow white oak before? Well now you can as flakes fly off the newly fabricated chine under John’s power plane.
The chine must be trimmed to being fair with the bottom planks. John uses the power plane to take the surface down to within 1/8” of the planks. Then he reaches for his favorite “finishing” took, a 3” x 8” Makita belt sander.
By the end of today, he will be finished fairing the new chine. Tomorrow we will work with him as we begin fabricating new bottom planks. (We are saving and reinstalling the three mahogany planks the forward ends of which sweep upward through and terminate above the boot stripe. These have been carefully cleaned, sanded and have had their back sides sealed with CPES.
Additionally, the garboard planks will not be fabricated until all other planks are in place.
That way we can scribe these planks to the actual width and shape remaining after all others are in place. Meranti is our go-to material for bottom planking. Click here to appreciate why and how it differs from genuine mahogany and Sapele.
Working from the chine inward, each plank will temporarily installed, and the garboard plank will be rough cut and then scribed to fit.
All of them will then be released and sealed with three coats of CPES, with the second coat being applied immediately following the first, which delivers enhanced adhesion between coats, and enhanced penetration into the plank’s fibers.
Final installation involves copious amounts of 5200, a continuous layer at least 1/8” thick is required, which translates into cases and cases of 5200. I will be sure we have ten cases on hand, along with at least 1,200 silicon bronze wood screws.
Well, you will see what I mean when we get to that point, but very soon, this elegant girl will be sporting a brand new bottom, on its way to becoming a True 5200 Bottom once we’ve applied five coats of Interlux 2000E Two-Part Epoxy Primer (barrier coat.)
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.
As promised two videos above, here are both an up-close view of the finished product following installing the first sheet of Aquatek Marine plywood, and the resulting issue with the bottom transom plank being too tall.
You cannot be too detail oriented in cleaning the excess 5200 from everywhere, and this includes sending RJ under the boat to confirm we have no ribbons of squeeze-out hanging from the frames in the bilge.
As is clear in the clip, before we removed the hog, the center of the bottom transom plank was at a good ¾” taller than it will be once we trim it flush with the plywood. The bottom planking will pass over this plank and terminate flush with the transom’s exterior surface.
The excess height shrinks to less than ¼” at the chines, which tells us that our “friend” jacked the center of the transom up, well, down once she is upright, which was the major contributing factor in the genesis of the hog.
Launching the True 5200 Bottom assembly is upon us … finally!
But first John and I must address a major issue we discovered when we began re-installing the bottom two transom planks, a discovery that also informed the “why/how” of the hog the hull was suffering when she arrived.
I will follow up with more detail once we have installed the first sheet of Aquatek Marine plywood on the bottom – two videos hence, but here is the gist of the discovery. When we tried to set it in place, post-reframing and re-shaping the transom to remove the hog, John exclaimed, “Oh my God! This plank is almost ¾” too tall in the center, and about ¼” tall at the chines!”
Yep! Old Mr. Butt Joint was here as well. Remember all the open joints we found in the transom framing before we rebuilt it? Well, Mr. Butt Joint was also Mr. Sloppy Joint, and the transom grew in height by almost ¾” in the process. (I now understand why the chine he installed was so ill-fitting. He had to goof around with it so that it fit between the bottom chine plank and the bottom planking.)
We will address the situation, and trim this plank, but not until the inner plywood bottom layer is fastened. Then we can scribe a line and trim the bottom transom plank accurately using our Fein Multimaster tool.
The happy news is that John and RJ finished fabricating, sealing and coating the components of the True 5200 Bottom’s inner plywood skin with Sandusky Chris-Craft Bilge Paint while I was tracing endless woodies in Tavares, FL.
We are ready to begin fastening the plywood. The finished True 5200 Bottom cannot be far behind!
Finally! She, and her previous “restorers” fought us every inch of the way. Perhaps most distressing is that, rather than neglect and just use her, this 1946 Chris-Craft Brightside U22 owners consigned her to shops for periodic maintenance.
Sadly we now know that she returned worse for wear because these folks took every shortcut and made every mistake possible. Bottom line, they worked to embarrassing low standards. Rather that repair, these incompetent souls created water traps, used softwood where white oak belongs, drove in stainless fasteners below the waterline, and on and on.
Sistering bottom frames resulted from being too lazy to simply release the keel, so that broken and rotted frames could be removed and replaced in whole, not piecemeal. Undoing all of the sloppy, ill-informed and just plain destructive results has been our prime challenge as we worked to essentially rebuild the transom and bottom framing, virtually from scratch.
Example: we replaced her rotted and split gripe because of the water traps these guys created, an issue that was compounded by not taking the time to replace broken carriage bolt fasteners. However, all of that is behind us as of today. We removed the corkscrew twist in the hull, the severe hogging caused by improper frame work, replaced at least two-thirds of the frames and cross ties, junked the replacement (softwood!) steering box mount with rugged white oak, replaced the gripe and much, much more.
Every square inch of every surface below the waterline received three coats of Clear Penetrating Epoxy Sealer (CPES) and two initial coats of Sandusky Chris-Craft Mahogany Bilge Paint. With proper maintenance over time, none of these members should ever soak up water again.
Now the hull is absolutely solid and ready for her True 5200 bottom. First, we will give the many tubes – at least 30 – of 3M5200 time to cure before we begin stressing it as we will when the inner sheets of plywood and outer planking are applied.
The sense of relief in the shop was like venting a huge boil as John tightened the final hex nut on the steering box mount.
Now the fun begins as she will look more and more like the graceful woody she is as we begin the construction (rather than deconstruction and replacement) phase of saving this wonderful and venerable Chris-Craft, who will grace Ahmic Lake in Ontario, Canada once again starting next summer!
We so hoped we would have passed the bottom framing milestone by the New Year, but she just keeps fighting us.
We discovered one more broken frame/cross-tie unit – that lying directly beneath the stuffing box – during what we fully expected would be our final integrity check.
And, what we hoped would be a minor repair to the steering box mounting system morphed into a complete removal and fabricating anew when I grabbed it during the inspection, only to pull a handful of completely rotted softwood, yes, softwood, out of what appeared to be a sound block.
This block is not original, as is evident from inspecting the forward section of the starboard bilge stringer and finding empty carriage bolt holes. But now we have fabricated, sealed and bilge painted a new mounting system using FAS grade, fully 2+ inch thick white oak that is more than equal to the task at hand.
John has finished fabricating the new cross tie, and plans to finish the frame sometime this weekend. Once it is sealed, painted and in place, we can install the keel, which will be bedded in 3M5200, and that milestone will begin fading in our wake.
Next comes installing the two chine planks temporarily as guides to sending the outer edges of the new chine frames to the proper bevel, and also sanding the bottom faces of the – now seven – new frames into the proper profile.
Finally, finally, then we can begin making patterns for the 1/8 inch thick Aquatek plywood, slathering the frames with 3M5200 – at least 1/8 inch thick, and fastening it down with thousands of silicon bronze screws.
By this time next week we should be fabricating and installing the inner layer of 1/8” Aquatek marine plywood to the bottom.
John will first fabricate an entire set of paper pattern sheets for each of the two surfaces and transfer them to the plywood. Once each component is cut and installed to test for fit, it will be removed and all sides will be sealed with Clear Penetrating Epoxy Sealer, followed by two coats of Sandusky Chris-Craft Red Mahogany bilge paint.
Then all three of us will work together applying mahogany 3M5200 to all ribs and other landings, followed by sinking thousands of silicon bronze screws.
The fun begins once the plywood is screwed down – cleaning the squeeze out, and there should be copious amounts of squeeze out, or you have not applied sufficient 3M5200.
The mahogany planks are next, and, while we will do our best to save the original planking, it is in pretty poor shape, which will force us to fabricate new planking using the originals as patterns.
But such considerations push us way ahead of where we are now, which is all about passing the bottom framing complete milestone!
Yes, another update on the Brightside Chris-Craft U22’s bottom framing.
The bottom is framed with a combination of main and intermediate members. The main frames land on the main topside frames and are fastened with a plywood gusset in addition to the #10 x 3” wood screw through the chine frame.
These frames are spaced 28.5” on center, save for the final three, which are spaced 26.5”, 25.5” and 25” on center.
The intermediate frames a screwed to the chine frame and joined beneath the keel with a cross tie plank that is screwed through and into the face of each frame member.
John announced yesterday that all new frames were installed and positioned so that the keel just lands on every pair from bow to stern, “But we seem to have a problem. There are no intermediate frames in the three bays lying beneath and aft of the engine and transmission.”
Sure enough, as you see in the clip, these three bays, bays which must withstand the torque of the engine and slamming against the water at speed, are bereft of intermediate frames.
Inspecting the replaced chine framing indicated that Chris-Craft simply omitted these frame members from the design, a contention that was confirmed when RJ inspected the whit-side 1946 U22 we have in storage.
We contacted the owner, who agreed with our contention that fabricating and installing three pair of intermediate frames beneath and aft of the engine/transmission only makes good sense. So we will.
Doing so will significantly increase the stiffness and strength of the bottom and the hull, which should translate into more of the engine’s torque powering the prop, rather than tweaking the hull.
Yes, we will repeat this process with the white-side U22 when we get to her preservation.
