lapstrake - plywood waste

[KenC]

One of these days, I will begin work on a glued-lap-plywood Herreshoff/Gardner double-ended rowing skiff. I haven't built lapstrake before, and am wondering how much waste I should expect, and therefore how much material I will need.

TIA,
Ken

[L.W. Baxter]

You can cut down on waste by making patterns for all the strakes with cheap cdx ply. That way, you can scarph together relatively thin rips of your (expensive) marine ply at advantageous angles. It's also easier to shuffle your joint landings around that way. Not to mention less aggravation when you make a mistake. And you can keep the patterns, in case you want to build a sister ship!

If I were to guess, by this method your total waste could be less than 20 percent of the area of your sheets...

[NormMessinger]

My hunch is there will be something more waste than 20% (wild guess) but not as much as 50%. Unless you do the way I did for the first two strakes on my first lapstrake boat :rolleyes: . I cut a piece wide enough to get out one strake, about 10" to get a 3" strake. After the second one I finally got the idea there might be a better way. Heavy kraft paper was too flexible for patterns and I settled on 1/8" masonite (hard board, the dark brown stuff slick on one side). Luan underlayment would be okay. Clamp the pattern on the expensive plywood and use a flush trim bit in your router to cut to size.

On second thought, if you measure the width of your strakes at the widest point and add 20% you should be fine IF you use patterns and don't make any mistakes.

[Bruce Taylor]

I find I'm too impatient to make patterns...it's like building the same boat twice. With good spiling technique, you can get the most out of your stock, & still have enough scrap to keep the woodstove going.

Mind you, I'm more frugal w/ time than material. For Blackfly (round bottom, 14 strakes, beam 4', length 14') I cut into 5 sheets of ply. I could have saved a sheet or two by scarfing up full sheets (instead of 2' wide half sheets)...or, better yet, cutting dog-leg scarfs to fit each plank. But as I said, I'm impatient....

[Keith Wilson]

That's a lovely boat, and would be really nice in glued-lap plywood. I expect that the plank shapes will be relatively straight, as such things go. I've always ripped my plywood sheets in half and scarfed them to make 2' x 15'+ panels - easier to handle but more straight edges, which is of course where the waste is, since you can nest planks on the sheet.

Oh, never mind, that boat is 17' or so, isn't it? Then you'd need two half-panels and a quarter-panel bit to give a 2' x 19'+ sheet. I think Norm's estimate of waste is about right. There will be more waste with the flat bottom than the topside planking; more curvature. - I'd guess five sheets for the sides (four 2 x 19 panels), plus whatever the bottom uses. Are you making the bottom out of thicker plywood? You might be able to get it out of one sheet if you're careful.

I've only built boats over a Tom Hill-style jig with stringers defining the plank shapes, so I've never used plank patterns until my current project. 1/8" doorskin ply is nice for patterns, and they're certainly handy if you ever want to build another one. If you use patterns, you could scarf the plywood in 4'-wide sheets, which is more of a pain but produces less waste. I've never made crooked scarfs, but it certainly makes sense, particualrly if you have a pattern and know how crooked to make it.

A suggestion for all those long skinny tapering strips of plywood left over from the planking: I laminated a tiller out of them because I couldn't bear to throw them away.

And BTW, a hand-held power plane sure makes cutting the scarfs quick. I just got one; no good for fine work, at least in my hands, but my God it sure can throw chips.

[ 10-08-2003, 10:19 AM: Message edited by: Keith Wilson ]

[Bill Perkins]

Ken you'll find marine ply available in 4 by 10 and 5 by 10 as well as 4 by 8 .You can save time and use little more material by eliminating one scarf ( but angle the one you make). See if an 8 and a 10 foot strip will work , or two 10's .You could stretch a string along the diagonals shown on the lines plan to get a good idea of the required plank lengths

I got a chance to row that boat at Mystic , it was very nice .

[dmede]

Ken,

I'm just finishing up the last planks on a glued lap canoe. I'd say the best method for reducing your waste would be good spiling as mentioned above. You can very easily gauge the max thickness of your plank and it's general shape with your spiling batten before nailing it down to mark the final plank shape. With the exception of a pair of mis-measured planks I had very little waste in my opinion (maybe 20%). I supose patters would be a more precise way to do this but not worth the extra work in the case of a small boat.

dave

[KenC]

Thanks, everyone.

I have thought that there may be a "sister ship" at some point - I really like the lines of this skiff - so patterns have some appeal. But on the other hand, there are lots of other designs screaming to be built, and I need to get on with #1 before starting to think about #2.

Gardner's book includes a fairly thorough section on spiling methods. I've read it twice, but need to go over it again. I'm sure it'll make far more sense after I've done one or two strakes. I've also got Iain Oughtred's and Tom Hill's books on glued-lapstrake building. Any other suggested reading on spiling methods?

Keith - yes, this one's 17' long. And I intend to use thicker ply for the flat bottom. I'm sure I can get that out of a single sheet.

Bill - Unfortunately, I haven't yet found a supplier in Ontario that carries, or will order for me, 10' lengths of marine plywood. I'm still looking, but I might have to go further afield (but still within Canada). Cross-border purchases are generally a pain, although I do order my epoxy directly from Raka in Florida.

Cheers;
Ken

[Venchka]

No worries about the off cuts of marine plywood. Depending on the needs of this boat, you'll find lots of uses for the "scraps". Save the rest. You'll find places to use them on the next boat.

[NormMessinger]

'Course ya could just lay your plywood right on the form and mark around the battons. tongue.gif

http://www.imagestation.com/picture/sraid16/p008fd23f91d26961f7a1e9f0e1c7ae27/fdefa2b7.jpg

Someone please define spiling. All I know about is relevant to beans and milk.

[Steve Lansdowne]

Type in "spiling" in the Forum's search function and you'll get some ideas -- Bud McIntosh's book, and perhaps John Brooks' (who uses some plank-like patterns joined in several places with pivots). Hard to understand verbally, but easier to understand if you've seen it done. Likely Greg Rossel's Building Small Boats book has a good section, though right now I can't find mine. HELP!!

[Bruce Taylor]

Goes to show there's more than one way to hang a plank, eh?

Spiling is just a method of transferring your lining-off marks to a long batten and then using those marks to reconstitute a finished plank in your flat stock.

Basically, you take your spiling batten--floppy and sloppy and made out of scraps--and clamp it to the moulds (taking care not to put any "set" in the edge). Then you use a set of dividers, or a compass (or a block of wood...whatever) to measure down from the upper lining-off mark, and up from the lower one. You make a little mark for each measurement. Then you take your batten to the bench, lay it down on the stock and repeat the measuring process in reverse. If you do it right, you end up with a plank that fits perfectly when sprung around the moulds.

It goes quickly, and you can often reuse the battens (I tack them together from whatever is lying on the shop floor). Sometimes I'll saw one in two and reassemble it in a different shape.

I imagine the pattern method would be just as quick, if you'd already notched stringers into your moulds at the plank lands (Tom Hill style). I'm too lazy and impatient for that too, I guess. Oughtred's method seems to agree with me.

[L.W. Baxter]

Hey Norm, nice method you have there... are you holding that sheet up with your head? Your hair isn't going to grow back if you keep mistreating your scalp like that, you know... :D

Nifty looking molds by the way... can I borrow them?

[ 10-08-2003, 08:00 PM: Message edited by: L.W. Baxter ]

[NormMessinger]

Nifty looking molds by the way... can I borrow them?

Maybe, if you are not in a hurry. We might drive out to see Wes one of these months in which case I could toss the mold in the pickup. Where are you from Eugene?

Ah, I've been spiling all along and didn't know it though I suppose some would say my batten is a little wide. ...or my mind a little narrow.

[L.W. Baxter]

Well, I'm about two hours north of Eugene. But I was really just admiring the clean fit and fair curve of those battens. I'm new to this internet "chat" stuff, and am finding that it's easy to sound like a heel, or in this case a mooch, if you forget that the written word doesn't convey all the nuance of regular conversation!

Nice "spiling batten", by the way. I knew what you were doing all along!

[Bruce Taylor]

or my mind a little narrowJust the opposite, Norm. You're too broad-minded...hence the good stable work-surface you've got on top.

OK, so you're a lumper & I'm a splitter. You've forced me back on the OED, and most every quotation there mentions a "rule-staff" or "spiling staff". I'm digging in my heels, old fella...if you're offering up the actual planking stock, you're not spiling, I say. I don't know what you're doing, but it looks mighty uncomfortable. :D

[NormMessinger]

So, Ken? Did you get the answer to your question? May we continue to hijack your thread?

I didn't see your question as mooching, L.W. and I would be pleased to pass the mold on to someone who has a set of plans for the Humble Bee and wants to use it. I haven't been able to break it up so it is only taking up space.

Okay, so I was scribing not spiling. Anyway, after the first strake or two, with the curve of the strake more or less established on the edge of the plywood I'd slice of a strip a bit over sized, clamp it in place, run my router around it on the battens and use it as a pattern for the other side. Two strakes with one slice--to paraphrase wisdom of birds and stones.

I might try spiling if I fall off the wagon but so far so good. I've been building free for almost 15 months now.

Another idea is to use two battens and a bunch of cross pieces to make an adjustable pattern. Maybe I'll try that instead.

HELP! Somebody stop me before I build again.

[KenC]

Yup - I got my answer. I haven't decided which method I'll use yet to mark out the planks, but I've got my material needs estimated. Whether I use patterns, spiling batten, or an entire sheet balanced on my head, I think the planks on this design will nest nicely. I guess I'll scarph the sheets in 4' widths instead of 2' like had initially thought, to minimize the first plank / last plank waste. Hmmm - that means I'll need to reorganize the garage.

Feel free to continue hi-jacking the thread, if you feel inclined.