Thread: Stringers

I'm not sure I understand your question, but it sounds like you wish to convert from a strip plank build, to a molded plywood build.

This can be done, but it's not something that I'd recommend a novice attempt. As a strip planked build, it will be about the easiest round bilge build you can imagine. As a triple layer, molded plywood build, you'd experience considerably more "fitting" issues and carpentry skills would have to be much higher. I also wonder about the value of a triple layer, molded hull, when a double diagonal or Ashcroft planked build would save on labor (Ashcroft considerably so).


What is your logic behind changing the planking scantlings on Amigo? You do realize that 3 quarter inch plywood layers (I'm assuming this is your idea), will be considerably heavier then the strip planked method?

I was thinking of using 3 layers of 1/4" marine ply.

Just to give you an idea of how heavy that is, if you use BS 1088 Okoume and not counting the adheasive to bond them together, a single square foot of hull surface will be 1.9 pounds each. If you use Meranti plywood (lauan) this sq. ft. will weigh 2.4 pounds. The .75" strip planked version of the same area will be about 3/4's (.75) a pound. This is a huge difference and just one reason why novices shouldn't attempt these types of design changes.

Again what is your logic in this change? Are you sitting on a stock pile of 6 mm plywood? Well, if you are, you'll need a minium of 28 full sheets (assuming no waste) for three layers of plywood on this boat. If you're not and assuming you can get the pricing I can on plywood (wholesale in the USA) 6 mm, BS 1088 marine Okoume will be in the $75 range per sheet, times 28 sheets is $2,100 (USD) for the planking. Or you could order 300 linear feet of clean, clear 1x2's from a local mill for likely a fraction of the $2,100 and do the hull as designed in strip planking.

The best part of using strip planking for this hull, is it will float at the place where the plans told you to paint the waterline. Planked with plywood, it will not and this is a fairly important consideration.

I can get Pacific Maple BS 1088 6mm ply for around $42 AUS/ sheet.

If 300 linear feet works out to be 91 linear meters then I could get it from the local for around $380.

God! I thought it would be more expensive! I see a teak deck........

Originally Posted by rohinmyson

I can get Pacific Maple BS 1088 6mm ply for around $42 AUS/ sheet.

Mate, you'd be wasting your time and money. Pacific Maple is a cheap plywood for cheap boats ... I'm currently using it on my Little Black Dog which is a 'budget' build rowing skiff and am already regretting the choice due to weight and quality (yup, forgotten about the pain of paying for it already). You also need to consider that Gaboon (yes, the expensive stuff) is not only better quality but 2/3 the weight and with what you're planning, weight is going to be an issue.

If I was doing a build like that, I'd be paying whatever it takes to get the very best gaboon plywood ... plus a bottle of scotch to dull the pain.

Sadly, while you need to buy ply with the standards stamps, those stamps are also whacked on ply that doesn't even try to pretend to meet the standard - your cheap pacific maple might be good stuff but it might also be rubbish (pacific maple tends to be a generic term covering a lot of types of timber). Regardless of the timber, the company or the price, always inspect it personally before buying it (I hate having to give advice like that )

How about you explain why you want to build this boat this way. You've obviously considered it, maybe you have good reasons that we haven't considered - not all builds are the same you know.

Richard

I guess why I have thought of going this way is that is what seems to dominate all the do it yourself boat building magazines.
It just seems to be a lot more work taking 1 1x2 at a time, but I guess in hindsight one would spend just as much time on 1 layer of 3/4 than 3 layers of 1/4.
I do like the Amigo and I'm tired of researching (more than 3 years) you name it I've researched it.
The Amigo fits everyone of my requirements and I have approval from the minister of finance as she thinks it's "pretty".

You'd also be able to do it glued lapstrake.

Like you, I'm a bit intimidated by the amount of work in a strip plank boat, even if 90% of it is repetitive.

Ask GlenL what options they have available and what they suggest - because it has been designed as a round bilge boat built over frames, you'll probably find you have a few options available to you.

Richard

It would look nice as a lapstrake. But I think I have decided to go with the original design without any mods to the hull. Got the space marked out in the back a yard and have ordered the study plans.
I might do a 1" : 1' scale model and see how she goes.

With the 1" strips, will there be much of an open seam in between the planks? I know in Buehler designs he calls for "twine" (I forget the proper name), or is the gap sealable with epoxy?

Haven't read Buehler, but he's calling for caulking of any sort between planks,
he's unlikely to be talking about modern epoxy strip planking.

Idea with strip planking is that you edge-glue each strip to its neighbour.
Once the hull is complete, sand it smoothe & fair, fill any gaps, then give it a
layer of glass/epoxy to seal & strengthen it. Then do the same on the inside
of the hull, creating a wood cored glass sandwich, which should be a single,
self-supporting 3D shell. The wood core is kept completely dry by the
moisture-barrier epoxy/glass sheaths.

What Buehler seems to be referring to is some sort of carvel construction,
planks over permanent frames, where the planks are designed to get wet &
seal the joint by swelling and crushing a fibrous caulk in between them. No
glass coating on the outside at all.


You mention lapstrake. Often, designers do offer the choice of round-bottom
(strip planked) or glued lapstrake. Those that do, would provide you with the
data you need - thickness of ply, overlap width etc. In many cases, stringers
are not required as the lap joint itself forms a stringer. Bolger's Chebacco
Boats are one such design that comes to mind. If it isn't a standard option on
the plans, the best person to ask is the designer. They will know if what you
propose is feasible. For a modest fee, they may well be able to do a lapstrake
version for you.

hope this helps
cheers
AJ

Nothing you've read in Buehler's book will be applicable in your Amigo build. George Buehler is a nice guy, but none of his methods apply in this type of construction, so forget everything you've learned in his book.

Do not change the size of the strips. The boat is "planked" with 1x2's (.75" x 1.5" nominal). The only place this may change is where you install "cheaters" or "stealers", (if you elect to).

Yes, in certain areas of the hull, the gaps will be fairly big. These areas are; along the turn of the bilge, near the bow below the LWL and near the centerline aft below the LWL (on the inside). This is normal and a function of this type of build. In these areas you can bevel the strips (a pain in the ass) or just back fill with thickened epoxy (the most common method).

Amigo is a tradisional strip plank design and has 8 frames (if memory serves me), one of which is a full bulkhead near midship (typical). This means her well glued strips are all that's necessary to make the hull water tight (no sheathing necessary, for strength or waterproofing). This is why the strips are so big in dimension, they carry most of the longitudinal strength necessary for the design. Of course it would be a wise choice to sheath the exterior of the boat with cloth, for abrasion resistance. The inside doesn't have to be sheathed either, but could benefit from it, if so inclined.

I'm glad you've elected to use Amigo's scantlings as designed. To give you an idea how much you would have affected the hull, with a triple layer plywood version as you described. A bare (no deck) Okoume hull would be in the 560 pound range, a Meranti hull 700 pounds, Pacific maple, closer to 800 pounds and a bare hull as designed in the 300 pound range (depending on species).

Amigo is a very good looking boat as a lapstrake. Built as a glued lapstrake, you could make a pretty much bullet proof version of one and eliminate several of her frames too. This wouldn't be a difficult conversion, but again you'd need someone to make the changes for you (in the plans).

Strip planking can be tedious, but it's very easy and fast to do. If you mill up all your planking stock before hand, you and a friend could plank this whole hull in a couple of days fairly easily. This assumes some economy of movement and both builders have a clue about what they're doing. Alone, an average person could plank her in 40 to 50 hours with little more then some reading up on strip planking techniques.

Of all the back yard methods to produce a round bilge hull shape, strip planking is hands down the fastest and easiest.

It seems my better half is pretty keen on getting this boat built and she has done a bit of research on the sly....She has ordered these books through Amazon....

"Cold-molded and Strip Planked Wood Boatbuilding" by Ian Nicholson
"The Gougeon Brothers on Boat Construction".
"Lofting", by Alan Vaitses
"The Complete Rigger's Apprentice" by Brion Toss
"Cost Conscious Cruiser" L & L Pardey
"Details of Classic Boat Construction" L & L Pardey

And she has bought several books on seamanship and navigation. She wanted to go travelling and get a caravan and I explained that this is a caravan on the water and we could go anywhere (almost) in the world - within reason- that she wanted to.So I think with these books I'll be of to a good start.

Toss out the "Pardey" books . . .

Why.....