cold molding over cedar strip

I've done a bit of boat building over the last few of years. I took a class at the CWB in Seattle where 3 of us built a cedar strip kayak over 9 days. I also took 1 quarter at the Seattle Central C.C.'s boat building program where we built a glass dingy (2 of us) using a female mold.

It has been my dream to build something larger... 20 feet or more, and I think I'd like to do this using a modified cold molding method. I say modified because most everything I read about the CM method says you first build a male plug then apply the strips over that. For my needs, I think it would be easier and better to use a method similar to cedar strip to give myself something to put the CM strips over, and not do a male plug at all.

I'm open to input though. Yeah, I know the obvious question might be "what boat do you want to build, and what do the plans specify for the construction technique..." well, I don't know yet what boat I want to build. It could be that I will build a few over my lifetime, but for now I'd like talk about the idea of doing CM strips over a cedar strip layer... then glassing the whole thing, of course, inside and out. In my thinking, the cedar strips just go over a framed out bulkheads, etc.

This is my first post here. I did search before posting to see what I could find and I didn't see this topic covered in much depth. Would enjoy the chance to talk this over with others that might have done or tried something similar.

Regards,
octavius

 

This is actually a common method, usually employed to add strength (of course) but also to prevent strip plank seam "print through".

Strip planking still needs to be done over a mold or closely spaced station forms, so you're not saving much effort.

Strip planking is a very novice friendly method, but cold molding isn't. With strip planked hulls, you can use less then ideal lumber of random lengths. A cold molded hull requires much better grades of material and the planks desire considerable skill when fitting them.

Select a design that uses this method, rather then take on the task of arranging new scantlings around a pure strip planked design. I say this because of the importance the molded veneers play in the structural picture, which isn't an easy concept for the budding designer to grasp.

Enlarge your boatbuilding library, possibly with some of the offerings from our on line book store. Strip plank and cold molding have many variations (I can think of at least a dozen or so), some not especially compatible with others.

 

Thanks for the feedback.

I'm #1 on the waitlist for the CWB course on cold molded construction, taught by John Guzzwell, this September. I wanted to take it last year but missed out.

I had a hunch the task of fitting the planks would take some skill.

Any reason why the stations can't just be framing that becomes part of the boat, rather than something that needs to be removed during construction? To me, from the perspective of holistic construction, thist just makes sense, provided that the design takes this into consideration.

Regards,
octavius

 

octavius,

For what purpose is it that you want to cold mould over the strip planking.
Are you looking for the cosmetic appearance or is there some other reason (better "lock in" of materials for instance).

I am asking this because the strip plank method of building is very attractive in its own way (assuming quality joinery). I know that some are built pretty shoddily, just using glue to fill the gaps, but strip planking with the planks formed previously as bullnose, concaves, really locks up, it looks good, and certainly is solid (particularly when sheathed).

I believe it makes very good bots, both cosmetically and structurally.

 

Mainly strength... the main reason I would be doing the strips in the first place is to give those cold mould strips something to lay on -- thus avoiding the need to build a male plug.

The cedar strip kayak we build in the class I mentioned certainly was very attractive, but everything I've read is that cold molding produces stronger hulls. That appeals to me.... that might be somewhat subjective, but it is what it is. I've seen and read about larger boats (20' - 80') built using a cold molded method... I wasn't aware of anything larger than kayaks and canoes built using just a cedar strip method.

I even saw in Devlin's stich and glue book that he has done cold molding over an initial stich and glue layer... I think strenght was the reason, but I could be wrong about that.

Regards,
octavius

 

Oh OK, no we build boats in Australia quite large from strip planking, certainly to the 50 foot range.

yes, cold moulded hulls are exceptionally strong, no doubt about it.

Strip planked and cold moulded over it would , i guess , be the strongest method i can think of to make the strongest wooden boat.

 

It depends on how you define strength. Molded hulls are lighter then just about any other wooden building method, unless you get into Lord method or composite cores. Pound for pound Lindsay Lord method is probably strongest.

Strip planked hulls have a nasty habit of "printing through" their strip seams, if lightly sheathed (which most are). This is commonly solved with an exterior layer or two of molded veneer.

You can take this concept one step further and decrease strip dimensions in favor of the molded veneers. In this case you're cooking with gas, using both methods to advantage and decreasing some of the draw backs.

As I mentioned, both strip plank and cold molded builds can come in a variety of configurations, some with frames, others just over furniture and bulkheads and others with just a few athwartship structural elements.

Strip planking is a category including several methods. The same is true of cold molding.

Again, the advantages of strip planking are the modest planking materials cost and ease of planking. Both molded and strip construction methods require a mold, either male or female, though typically male for ease of planking. Molded construction permits the designer to orient the veneers to take most advantage of their physical properties and the reason light, yet strong hulls can be built.

 

One way to reduce framing in the mold is using "ribbets" as I did. However this way is more inaccurate than proper framing, and not good for thin ('er) planking. Take a look at my pictures at the Gallery..