Wood Choices for Cold Molding

[Pericles]

Hello Tom,

The Sculley and Jarrett Bay sites demonstrate your points about coldmoulded Carolina sports fishers very well. They are beautifully shaped and I wonder whether you are toying with the idea of building a smaller version for yourself

I am in the midst of moving house, so that I can start building my very own stitch and glue motor yacht, with the help of my three sons. They are willing to work with me, because they figure I'll live aboard and they can have the house. They aren't wrong actually!

What I am finding intriguing is the way the boat keeps evolving in my mind's eye. I love the look of the Sterling Atlantic 43 flush decker style married to the Devlin Czarinna/Sockeye pilothouse and aftcabin design, but with a monohedron hull form with large flat chines for speed and powered with water jets. I no sooner get the outlines settled, then along comes another idea. Just look at the Vicem Down Easters. Bloody gorgeous!.

One idea concerns erecting the shelter for building. Steel scaffolding poles can be purchased quite reasonably and the supplier I talked to here in the UK is willing to buy them back, when construction is completed. Properly erected, they will support hoists and provide working platforms alongside the hull as it grows. Being a temporary framework means no building permission needed. A wood framed construction would attract the attention of the planners over here. Strange, but true.

The Renn Tolman skiffs are partly built in a cradle, whereas Sam Devlin sometimes uses moulds and builds the hulls upside down. As a monohedron hull form is basically one profile for most of its length, how about draping the wired bottom panels over an A frame of scaffolding to create the basic V shape and attaching the separately formed bow by butt jointing it on with overlapping layers of ply outside and then inside to obtain the desired bottom thickness. This hull bottom is glassed inside and out and the fairing completed. The outer bottom is fully finished before it is set into a strong cradle ready for the hull sides to go up and the bulkheads installed. The basic hull is turned only once and final painting is simplified. OK, it's different, but my first idea was to use a 35 foot length of very thick and tough plastic sewer pipe mounted horizontally as a "horse" and build from that. No hook or hogging then eh?

Regards,

Pericles

[Boston]

Im going to go with Tad on this one
as compared to solid wood ply is just not going to turn out as strong a product in this application
the issue of the inner veneer's of the pywood being shorts is a obviously inferior to solid veneer's without this issue

cheers
B

[cudashark]

I absolutly dont agree.

I used 5 layers of 3/16 inch mahogany veneers to build this and it is far stronger than "solid" wood.

Ray

See the build in the gallery section for user name "cudashark"

[Boston]

I think you misunderstand me
I do not consider ply to be solid wood

Im betting you used mahogany in that mahogany build of yours ( nice looking job by the way )
I would consider mahogany veneers to be solid and plywood veneers to be made up of a laminate material
not solid like the mahogany you used

point being that if you rip a sheet of ply you end up with half the inner veneers being of extremely short pieces
certainly a situation to be avoided in a truly quality build like the one you have shown here

I like the idea of mahogany but its mind bending expensive compared to my other choices

[Boston]

hmmm
not sure were my post just disapeared to but basically I suggested we misunderstood one another

I dont consider ply to be a solid wood
mahogany is

a veneer in cold molding can be made up of ply a laminate type wood or solid veneers of wood

my bad if I did not make myself more clear
B

[cudashark]

I think I do misunderstand Boston.

When I think of solid wood I think of a chunck of 4 or 6 quarter solid wood. When I use a ply it is a veneer of many layers glued togeather to make a strong panel.

Ply comes in many pefabricated variaties and grades of quality. I use a lot of solid face frame construction with ply cabinets to build most projects.

Ray

[Boston]

yup
its walking a pretty fine line
in cold molding your making your own full length laminate layers if you use solid wood to begin with
but if you use ply and then slice it to say 4 inch widths
well break open the ply and you will see every other layer is made up of grains going the short way
not a great way to gain the most strength
might as well use solid wood in the veneer's as you did with the mahogany build you presented

nice job to by the way

B

[dskira]

Originally Posted by gonzo

Coldmolding doesn't always use veneers. Strip planking is also a form of cold molding. If you are going to laminate with fiberglass over it, strip planking is cheaper and faster.

I have to disagree with this statement. Strip planking has nothing to do with cold molding.
I will say it can be a "base" for the cold molding.
But I agree with the second part of the statement about cheaper, while it is time consuming also.
Well thought in advance the cold molding can go pretty fast.
You do not need to laminate on top of strip plank. Just edge glued and fastened is enough. A lot of O-Yolle still sailing after been built in the 1920 with this very classic method.
I don't really understand why the trend is to epoxy everything. No real need if the based is well done.
I built and raced my own IOR made of cold molded (just three layers on space frames and close longitudinal) and just painted for years, nothing ever shown. We used at that time the Aerodux glue and a gun stapler.
Latter on I built several fishing trawler with very thick square section planking in a strip plank fashion, with thick paint in between on the edge and heavily fastened .
Also I built small sailing boat with strip plank, never used epoxy. Still sailing.
But I suppose using epoxy sheathing will make boat lighter and stronger with thinner scantling.
I will not use plywood for cold molded, half of the wood if for nothing, and the boat will end up to heavy. Veneer of thin plank is the only way to go.
And I admit I never used the vacuum system. Must be quite a good way to make sure the gluing pressure is the same everywhere.
As usual, my two cents.
Daniel