Cheapest and easiest building material

I started a thread regarding the lightest building material. http://www.boatdesign.net/forums/showthread.php?p=147290#post147290

Frosh quite rightly pointed out that for the 30ft, 25 knot powerboat in question that light weight is not the only consideration. Amongst other things - not least of which is ease of construction - cost is a major factor in any boat build.

So, once again, setting aside the exotics, which is the easiest and which is the cheapest building material / method?
Aluminium
Foam Core
Balsa Core
Strip plank
Glass over ply
Something else

 

Glass over ply. Fast, cheaper than the rest. Easier to fair flat panels, no need to fully glass inside. Self-aligning with proper patterns and stitch and glue.

 

And also plain plywood without glass, for example in the topsides, little sainding, no fairing, just epoxy and varnish.

 

Agree with Raggi and Alan… And if you saturate all parts in Ethylene Glycol (see THIS thread) you will greatly protect against rot at an economical price too.

 

A lapstrake hull (or planked in any way that duplicates seperate planks) is ideal for varnish over epoxy. Makes a beautiful and light boat with a minimum of cost Lapstrake requires skill, but almost entirely carpentry skill, which is the way it should be.

 

Ok - so the consensus is very definite that, for developable shapes, stitch and glue is easiest and quickest. And probably almost as light as the other build methods.... so what are the downsides?

 

Prepreg 12k uni- and biaxial carbon fibre, autoclave-cured at ten atmospheres, 180 Celsius.
Oh, you wanted cheap and easy? Glass over ply it is, IMHO. Or just plain plywood. Stitching with wire, a la stitch-n-glue, is in my opinion (and I got this originally from H.H. Payson) an unnecessary and tedious step that isn't at all necessary if the developed panels are shaped to actually fit together properly in the first place. In Bolger boats, the seams line up well enough that you can just fillet and tape, the wire wouldn't do a thing. Makes the build a lot easier to get the developable shapes right from the start.

 

I think making all those holes and stitch panels together is very time consuming and a bit messy. A few frames lined up with som longitudinal stiffeners is better, I think, first the inner structure, then the outer skin.

 

Downside is the limitation to designs that use panels that won't curve two ways. Lapstrake makes for convexity and concavity, however, in the fashion of the original planked hull it copies.
A dory, most sharpies, and many other designs don't need developed sections, of course, but plywood's one limitation is what designs can be made from it. Otherwise, cold-molded hulls are really "homemade" plywood, an indication of the inherent strength of ply.
Ply is also not available in long lengths except in very rare cases. That means butting or scarfing long pieces.
But all in all, it is nearly the perfect boatbuilding material when its limitations to form compound curves do not apply to the hull you are building.

Alan

 

Stitching panels together may slow down the pro builder, but in this day and age nearly everyone owns a cordless drill and the backyard builder, I think, doesn't mind all that drilling and wiring (and removing and de-gooking).
I would not personally choose stitch and glue as a semi-production method, but I would have a good mold, which is an investment that few home builders would prefer over stitching.

 

I just tested a one step joint and some finger joints made by cnc router and epoxy glue. The joints are stronger than the other areas, but not so much stiffer (after sanding) as a 1:12 scarf, that means I think fingers are better than scarfs.

 

On a bent panel, yes. On a flat surface such as a cockpit sole, I'd choose a scarf because it has less glue line exposed.
Thanks for that info, Rag.

Alan

 

I'm sure there's zillions about, but can you guys point towards an online step-by-step description on the process? I searched the forums but came up blank
Using the molds sounds like the go - from what I've read, there's less likelyhood of winding up with an out of shape boat that way too. Male or Female molds? I s'pose with female molds you can use bulkheads as some of the formers, whereas with males they'd all be 'extra's'. It'd also make glassing the bottom and topsides a whole lot easier with the boat upside down.
Then again, males would allow you to build in most or all of the internal structure with the boat still held to shape in the molds....

Thanks again for all your help

 

Scarf and other Joints in Plywood

Dave Carnell has a somewhat different opinion (as usual!) about making long plywood. See http://www.angelfire.com/nc3/davecarnell/epoxy.html

As usual, he has done significant testing to back up his ideas...

 

Good article. Especially when they sell filler at the marine supply for ridiculous prices. Butting and taping isn't so renegade an idea. Inadvertantly grinding or sanding through it later is probably the biggest detractor, and there are people out there who will do just that, especially if there is a slight hump they want to "feather out". Although not necessary, slightly dishing in the joint to a few inches on the outside might prevent this. Every boat gets old unless it blows up or something equally catastrophic, and most boats eventually fall into the hands of enthusiastic but uninformed owners.
How many times will a fifty year old boat have been "refinished" by an amateur? Three? Five?
We all know somebody...

And yet, how far should a builder go in anticipating such things? Certainly, not many large companies care to think about such things unless required by law. I see how companies comply even when ordered to comply, like the acetone I bought the other day, which has a plastic cap requiring a screwdriver to open, upon which it sprays all over your clothes (my eyes are closed) from the jerking action. But they complied!
I find builders here to be an example of what is being lost in corporatizing every industry. They would actually consider such far-flung ramifications as someone owning the boat years after they themselves have left this Earth.
No wonder none of them are millionaires!

Alan