Priscilla, our 1940 seventeen-foot Chris-Craft Runabout has blasted through her True 5200 Bottom milestone!
After replacing nearly half of her rotted bottom framing and installing a new inner skin comprised of 4 mm Meranti mahogany marine plywood six-inch-wide planks laid at an approximately 45 degree angle with respect to the chines and keel, all of which was bedded in 3M5200, we fabricated and installed outer planking using three-eighths FAS-grade Meranti mahogany plywood, also bedded in 3M5200.
It was all sanded fair with countersinks and declivities filled using 3M Premium Marine Filler before being faired and sealed with CPES a final time.
Priming – five coats of Interlux 2000E Barrier Coat Primer – was followed by applying multiple coats of dark green Interlux Ultra-Coat hard antifoul paint.
We will now flip her upright, repair several dings and gouges and then hand block sand her using 250 and 600 grit. Finally, she will receive upwards of ten coats of Pettit Captain’s Ultra Clear varnish and buffed.
Once she is reassembled, she will be ready for her final milestone, returning home to Delaware, OH.
Priscilla, our 1940 17-foot Barrelback “lab rat” experiment is progressing rapidly now that we finally took delivery and milled the Meranti mahogany planking needed to complete her True 5200 bottom. As we shared in our last update, rather than install her inner skin using 6 mm plywood panels, we are reverting to what is a truly very old school alternative: replacing the inner skin using strips of planking laid at approximately 45 degrees to the keel.
In so doing, we will deliver a bottom, the inner skin of which precisely matches that installed in Algonac in 1940.
Once we dry-fitted each, approximately 5-3/4”-wide plank, everything was sealed with four coats of Smith’s CPES, after which we have applied three coats of Chris-Craft mahogany bilge paint to their inner surfaces. Next, we installed these planks bedded in mahogany 5200 using #6×1” Frearson-drive, flathead silicon bronze wood screws.
Happily, her bilge now presents exactly as it did when Priscilla left Algonac in 1940.
Planking the inner skin produces a tighter, more rigid skin that follows the bottom’s contours precisely. Any interior squeeze-out will be removed using nylon putty knives before it, too, receives three full coats of Chris-Craft mahogany bilge paint.
Post this experiment, SMB will make individually planking inner skins our standard for SMB True 5200 bottoms.
With the Meranti planking in-hand, and having milled it to land fair with the chines, and began dry fitting it to her bottom. Our first step involves measuring both bottom faces at their widest point between the keel and the chine.
Here, and as we’ve shared with you earlier, we once again confirmed that Chris-Craft’s rule-of-thumb was operating at Algonac when her hull was being laid out. She is 7/8” wider on port than she is on starboard at the widest point between her keel and chines. And, at the transom, she is a 1/2” wider on starboard than she is on port.
Joe will dry fit and fasten the outer planks temporarily, working from her keel to her chines. Once laid out completely, the planks will be released and sealed on all sides with four coats of Smith’s CPES. We will also apply one final “insurance” coat of CPES to her inner skin’s bottom.
The final assembly step involves bedding each outer plank in an at least one-eight-inch-thick bed of white 3M5200, before fastening them with #8×1-1/4” flathead silicon bronze wood screws. Finally, and that’s when she really begins looking good, we apply five coats of Interlux InterProtect 2000E Barrier Coat Epoxy Primer, with alternating gray and white coats, which helps expose any holidays. Per Interlux’s instructions, 2000E should be applied in thin coats.
Priscilla, our 1940 17-foot Barrelback became our lab rat today as we tested what we are calling a New Day at Snake Mountain Boatworks when installing a truly True 5200 bottom.
Rather than install her inner skin using 6 mm plywood panels, we are reverting to what is a truly very old school alternative: replacing the inner skin using 6mm strips of planking laid at approximately 45 degrees to the keel.
In so doing, we are able to deliver a bottom, the inner skin of which precisely matches that installed in Algonac in 1940.
Once we have dry-fitted each, approximately 5-3/4”-wide plank, everything will be sealed with four coats of Smith’s CPES, and we have applied three coats of Chris-Craft mahogany bilge paint to the inner surfaces, we will then install these planks bedded in mahogany 5200 using #6×1” Frearson-drive, flathead silicon bronze wood screws.
Once finished, the bilge will present exactly as it did when Priscilla left Algonac in 1940.
We will then proceed as we do with all SMB True 5200 bottoms, installing the outer mahogany planks bedded in white 5200 using #8×1-1/4” Frearson drive, flathead, silicon bronze wood screws.
Planking the inner skin produces a tighter, more rigid skin that follows the bottom’s contours precisely. Any interior squeeze-out will be removed using nylon putty knives before it, too, receives three full coats of Chris-Craft mahogany bilge paint.
Post this new day, SMB will make individually planking inner skins our standard for SMB True 5200 bottoms.
