Cold-Molding Over Planking?

[rfnk]

I'm about to embark on restoration of a timber Twister (28' yacht, Kim Holman design). I have 3 options re hull restoration. 1. Simply restore planking - it seems to be in reasonable condition, 2. Repair and glass it, or 3. Cold-mold over the old planking. Any thoughts on this would be welcome. I'm wondering too how to terminate the cold-molding (or glass) at the ballast so that I don't simply create a moisture inviting open ended sandwich (if you catch my drift!). Any thoughts welcome. Cold-molding is my preference at this point due to the increased strength for an old boat (1967) so if anyone knows of a good book on how to cold-mold over old planking, I'd also be grateful for that information! Thanks! Rick Location - Port Stephens, NSW, Australia

[PAR]

Cold molding over questionable spots in the planking is inviting trouble. Cold molding over freshly repaired or sound planking can rejuvenate a tired hull. You could also strip plank over the hull, which is much easier.

'Glassing over the planking eventually causes issues, especially if it's a thin sheathing. A 'glass skin that is thick enough to do the job, adds considerable weight.

Planking repairs are usually the most economical way to go.

You would handle the bolt on ballast casting just as you would if the hull was all cold molded, 'glass or other construction method. The ballast is removed (yep, I know it sucks), the planking or sheathing is "tied together" from side to side, bolt holes drilled and the ballast bedded again. Each building method will have application specific techniques to accomplish this task. Basically it entails planking (or sheathing) the portion of the hull at the ballast joint too.

This is a relatively odd ball restoration technique. Not that it's not preformed, but it's not particularly common, so books covering the subject aren't available as far as I know. On the other hand, many repair and building books do offer something on this treatment.

[rfnk]

Thanks PAR
The ballast will be coming off anyway. I'm not sure what you mean by tying the planking together. Where the new strips meet the ballast it's going to be thicker so do you mean fairing back the timber keel at that point - I mean, what is your suggestion for fairing so that the cold-molding strips fair into the old ballast? Regards, Rick

[Ike]

I'd go with PAR. Repair the existing planking. As you said "it seems to be in reasonable condition" Don't glass it or put cold molding over it. It will just create issues you will have to deal with later.

[PAR]

No, don't remove material from the current keel area, you may need to install longer ballast bolts, but most have enough extra length to absorb the 1/2" or so of additional planking material you'll layup over the existing keel.

A lot depends on how the rabbit is handled on your boat. Is it a built up rabbit, a cut rabbit, does the ballast casting carry all or part of the rabbit, etc. Typically you do something similar to what's already there and terminate the planking at the rabbit. You can mold right around to the other side on certain shaped hulls, but again it all depends on how the rabbit is engineered.

Cold molding, strip planking and 'glass sheathing should be a last resort to save a tired old hull from the chain saw. Planking repairs would be the preferred and likely cheapest method.

[Chris Merriam]

If you can get your hands on old Wooden Boat magazines, there is a great article in #168 Sept/Oct 2002 "Alternative Repair Stategies for Wooden Boats". Another article you can maybe google is "A Cold-Mold Rebuild: Covering an Old Wooden Hull with New Wood" by Fritz Seyfarfh. Both helped me get some incite on what direction to take along with PAR and other's expert advice.

Good luck, Chris

[rfnk]

Thanks PAR and Chris
I'll certainly be repairing any suspect planking etc. prior to cold-molding if I do go that way, and will only consider cold-molding if the hull turns out to really be at that stage. The boat's out of the water now and due to be craned onto our driveway this week. I'm working in Vietnam at present so I won't actually get to see the crane drop it on the driveway or knock the house down, and I won't be able to really inspect the hull properly for a few months. Firstly, I want to let it dry right out slowly and secondly, I won't be there! I'll try to get a copy of those Woodenboat articles. Regards, Rick