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Kudzu
03-14-2017, 12:04 PM
I have the replacement boards cut for my lapstrake Chris Craft. When the new and the old overlap they were held together with bronze nails with the ends peened over. Removing those left holes in the good planks so I can't go back with these. Motor stringer is in the way so penning a rivit would be very difficult so I am considering using machine screws and MP nuts. Just looking for a little feedback on these. It is my understanding these were used in some boats but I have no experience with them.

Second, I need a bronze screws, who has good quality with good prices?

wizbang 13
03-14-2017, 01:17 PM
Ply or timber planks?...either way, I see epoxy in your future .
Jamestown distributors is my go to for bronze fastenings.

Kudzu
03-14-2017, 01:35 PM
Plywood strakes. The planks are screwed to the bent frames, the nails were just used between the frames.

wizbang 13
03-14-2017, 01:55 PM
What uh, IS a pm/mp nut?

Gordon Bartlett
03-14-2017, 03:50 PM
I don't know what is meant by "PM Nuts", but if it is any help, a lot of old Thompson lapstrake runabouts were fastened with brass machine screws and hex nuts. I think they were #6-32.

Tom Robb
03-14-2017, 04:38 PM
I'm led to understand that brass has NO place in the structure of a boat. Copper, yes.
Is that true?
And +1 on the question, what's a PM nut? Only gets used between noon and midnight?

robm
03-14-2017, 04:45 PM
Salt water, brass is not recommended. Fresh water, it is not too bad. So Thompson boats probably did just fine with their brass screws.

Bronze is usually the best bet.

PM nuts are square, with a dished bottom, so they grip the wood, no wrench needed on the nut side.

https://www.jamestowndistributors.com/userportal/show_product.do?pid=55197

Kudzu
03-14-2017, 05:16 PM
Here is a photo of a some.

http://www.brass-inserts-fasteners-india.com/silicon-bronze-fasteners/silicon-bronze-nuts/silicon-bronze-pm-nuts.jpg

JimConlin
03-14-2017, 08:41 PM
I'd use epoxy. Stronger, faster and lower cost, but more of a PITA if you have to open it up someday.

Garret
03-14-2017, 08:50 PM
I used bronze PM nuts for attaching the rubrail on my Dyer Dhow. Yes, a glass dinghy, but oak rubrail that had to take a serious bend. Been on for 6 years now & never had an issue.

Kudzu
06-08-2017, 10:07 AM
Found two sources and wanted to post for the next person searching for these.

Jamestown has them in stainless only.

CC Fasteners (http://www.ccfasteners.com/cgi-local/browse.pl?type=topic&id=60&cart_id=3212d14d8c6df9a6eb1ff3f1fc1bf22f) Only reasonable priced place I have found.

Top Notch fastners. (http://www.tnfasteners.com/cgi-local/browse.pl?type=topic&id=60&cart_id=00e4d70b094c7e6eccccc5dae4c45adc)Expensive but they have them.

Jay Greer
06-08-2017, 11:35 AM
Machine screws are not made of bronze small enough for what you are in need of. They would be a very expensive way to go if you can locate same. Better to
go with copper nails that are riveted using roves, cupped washers, to draw the peen tight. The Northwest Wooden Boat Foundation can supply you with what you need including the necessary tools.
Jay

Garret
06-08-2017, 12:26 PM
Machine screws are not made of bronze small enough for what you are in need of. They would be a very expensive way to go if you can locate same. Better to
go with copper nails that are riveted using roves, cupped washers, to draw the peen tight. The Northwest Wooden Boat Foundation can supply you with what you need including the necessary tools.
Jay

You are correct about price, but they are available: https://www.google.com/search?q=12-24+bronze+machince+screws&ie=utf-8&oe=utf-8#q=12-24+bronze+machine+screws

Kudzu
06-08-2017, 04:17 PM
Nails and roves would work but I work by myself and do not have anyone to help. They are just not a one man job on an existing hull repair.

These seem to be my best options. Plus I can easily put it temporarily together with these and take it apart. The seams are sealed with 5200 so once it is together I don't see it coming apart once it is in place. And I will probably need well under 100 pieces for this repair.