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View Full Version : Cold Molding vs. Replanking



kmarengo
05-16-2003, 09:37 PM
I am repairing a mahogany planked boat, my question is...what would be the best way to fix it? There are over 20 broken or cracked frames...should I replace the frames and rework the original planks, or is cold molding over the planks a better way to go? And when do you refasten? Do you have to redo all the screws at the same time?

kmarengo

JimD
05-16-2003, 10:04 PM
Hello, kmerengo. Firstly, I have no experience whatsoever with restoring a planked boat, but seems to me that you are talking about whether to restore a boat to its original construction type or to turn it into a completely different type of hull. Personally I think its a sad thing to take a traditionally planked boat and change it like that but it ain't my boat :D Also, veneering a hull with a lot of busted frames sounds like a dangerous band aid cure that could add a lot of weight but not necessarily strength where you need it. Are the planks themselves in good shape? T'were it me, I'd replace the frames.Perhaps others with more experience with this will jump in (and make me look foolish smile.gif ) .

imported_Conrad
05-16-2003, 11:13 PM
How big a boat are we talking about? An open 20'er- repair the frames and refasten, it's easy and fun. A 40'er with lots of interior stuff in the way and other issues, maybe cold mold. A lot depends....

kmarengo
05-18-2003, 05:16 PM
Thanks for responding...
The boat is a one design 30', I believe it is a "American Knarr". The interior (what little there was) is almost pull out of the boat. 75% or so, of the planking is ok, all of the dead wood needs replacing and the deck & cabin roof needs replacing...as far as I can find out the boat is not one that is in demand...so I am thinking I might as well modify this boat to meet my tastes. I am also intrested in make the hull as stiff as possible. I am wondering what the difference in costs would be between the two methods...since labor is donated for the pure pleasure.

imported_Conrad
05-18-2003, 09:47 PM
Knarrs are nice boats- I've seen them in Seattle, and they're popular in the Bay area here on the west coast. While not a high dollar boat, they do have a following, and numbers are limited, all of which suggests a traditional approach to repair.

That said, I've done a fair amount of cold-molding both as new construction and as a repair strategy, and can share the following. First, it's not the cure-all many represent it to be- to be successful, you first have to do many of the repairs you'd have to complete anyway. There's no point in molding over rot or bad hull to keel joints, etc. Think through what the cold-molding will strengthen, and what connections within the structure will still be weak.

Second, it is neither cheap nor labor efficient unless you're air nailing sheets of plywood to a very large hull with a number of helpers. My current project involves two layers of ply strips on the bottom of a 37' power boat, about 400 square feet of surface area. In addition to first completing all the repairs required for a traditional reconstruction, the molding has consumed $1500 and about 300 hours.

Given my level of experience, I'm convinced it only makes sense in two situatuions- where you really want to add strength to a lightly built design, and where it can be done very quick and dirty to get an extra 10 years or so out of large, dying/dead power boats.

R.I.Singer30
05-18-2003, 10:25 PM
I've got a 30' mahogany planked sloop built in the 50's.I don't plan on being in the water with it for several years,but i am enjoying the challenge.I'll be building a steam box and replacing all of the ribs one at a time or so.Every other one and then the others.Then some of the planking.Then the interior.My goal is to rebuild it to it's close to original shape.If I wanted I probably could do a quick job and put it in the water this season but I'd be putting off the inevitable.I am also watching the papers and boat yards for a decent /affordable /trailerable boat to keep my urges satisfied. I guess it's what you want/need. I also have friends with boats to satisfy the itch.All I need is a 4 hr.work day and a 36 hr. day.Good luck Dan L. smile.gif

warwick
05-20-2003, 09:57 PM
from my own experience and research of cold molding planked boats, there are some priniples involved. All rot and I mean all rot must be taken care of, personally I would and I have done, repair all broken frames, difference being if you go cold mold you can laminate them in glued to the planking, otherwise laminate but don't glue 'em to the planks,all seams should be splined, cold molding will add strength to the hull and you will have a "dry" boat, the extra layers, I only ever use veneers, not ply, will add bouyancy to the hull, it is a big job to do right but worth it, however only do this if it is necessary, otherwise repair it as it was built. Read up on the west system for doing this and look up Tim Carr's boat Curlew for mor info.