Screw Sizes for Planking and Deck Fastenings according to Nathanael Herreshoff
Captain Nat Herreshoff, known fondly as the "Wizard of Bristol" was one of the most innovative and progressive builders and designers the world has ever known. He designed and built hundreds of yachts in his own shipyard right here in Bristol, Rhode Island. That very site is now occupied by the Herreshoff Marine Museum, but at one time it had all the equipment necessary for Nat to control every detail of yacht construction, with it's own timber mill, pattern shop, foundry, sail loft, and more.
Along with Henry B. Nevins, Nat Herreshoff worked with the Lloyd's Register of Shipping to formulate a list of yacht construction rules devised to ensure the construction of safe and seaworthy vessels. You can find the entirety of the Herreshoff and Nevins Rules for Yacht Contruction in a .pdf format available here.
Since of course Fair Wind Fasteners is in the fastener business, I've found it particularly interesting the Nevins and Herreshoff created a table for Silicon Bronze Screw sizes to be used for planking and deck fastenings, as well as a reference for the size of wood bung or plug you'll need, which we also carry. With this resource, there is no reason to leave screw sizing to chance, and you can reference the wisdom of some of the greatest boat builders the world has ever known. Here is what they have to say about which size screws to use on your yacht:
| PLANKING THICKNESS |
APPROXIMATE DIAMETER |
SCREW GAUGE NUMBER | LENGTH | DIAMETER OF BUNG |
| 3/8" | 9/64" | 6 | 3/4" | 5/16" |
| 7/16" | 5/32" | 7 | 7/8" | 5/16" |
| 1/2" | 11/64" | 8 | 1" | 3/8" |
| 9/16" | 3/16" | 9 | 1-1/8" | 3/8" |
| 5/8" | 3/16" | 10 | 1-1/4" | 7/16" |
| 3/4" | 7/32" | 12 | 1-1/2" | 7/16" |
| 7/8" | 1/4" | 14 | 1-3/4" | 1/2" |
| 1" | 17/64" | 16 | 2" | 9/16" |
| 1-1/8" | 19/64" | 18 | 2-1/4" | 5/8" |
| 1-1/4" | 5/16" | 20 | 2-1/2" | 11/16" |
| 1-1/2" | 11/32" | 22 | 2-3/4" | 11/16" or 3/4" |
| 1-3/4" | 3/8" | 24 | 3" | 3/4" or 13/16" |
| 2" | 13/32" | 26 | 3-1/2" | 13/16" |
All of the sizes above are of course in imperial measurements. I can't help but think metric would be easier once I start looking at measurements such as 19/64"... But hey - it's what we have!
Nat also notes that for double planked yachts use the table sizes for inner plank fastening to timbers and same gauge but length as required for fastening between timbers. For the outer planks, use sizes for total thickness of both inner and outer planking.
I hope that by passing on a bit of the wisdom of Nat Herreshoff and Henry Nevins your search for the right size screw is over! Fair Winds and happy boatbuilding.