Adapting Molds for battens (Glued lapstrake)

[Jim M]

The Hill way, the Oughtred way.

The Hill way, molds are smaller by the thickness of the battens, which makes the batten edge available to a router bit bearing. The battens themselves define the shape of the plank. Plank blank clamped to battens, traced underneath, done.
But how do you reduce the molds accurately? IF the plans show the lands, do you draw a line from them to the centerline and reduce along those lines?

The Oughtred way, a batten is tacked to the next upper plank boundary. The plank is shaped the "normal" way, i.e. by taking the pattern and/or plank on and off the boat about twenty times, shaving a bit here and there each time. How is that better?

I also don't understand the plank pattern deal with the two strips and the diagonals. You force two battens onto the upper and lower plank boundaries (curves) and fix the curves with the diagonals. Then you take it off. How do you flatten the curves accurately onto the plank blank?

[MarkWoyWoy]

Jim,

I simply took a compass set to the size of the battens and ran around the mold to reduce the size. The molds were then cut to this line.

I think Mr Oughtred believes the Hill way is a lot of work for one boat and also that it may lead to an unfair boat.

I used the Hill way for my first boat and was very happy with the results. I took a couple of days to lay the stringers out nicely and it let me see what the finished planking would look like. It seems that this would be difficult the Oughtred way.

As far as the fairness issue is concerned I ran the stringers nearly to the stem and then spilt them vertically back to the first mold, this meant that they bent easily when the planking was layed. Because the stringers were longer than Hill recommends it pushed the planking out slightly between the first and second molds.

It ended up fair.

It is true that Mr Hills method is more initial work however it probably saved me time in the long run and also allowed me to visualise the end result prior to actually planking.

Mark S.

[DougWilde]

A couple of Charlotte canoes were the first boats I built. Cutting and assembling the molds on the strongback, then spacing and attaching the ribbands was great practice and a confidence builder.

But beware of routing planks on the building jig. Especially true if you have a large router because I had a tendancy to apply a bit of downward pressure to keep the router bit in contact with the guiding ribband. Unfortunately the ribband can bow under such pressure, resulting in a bit of whoopdeedoo in the edge of the plank.

One can reduce such deviations from "fair" by chucking your bit in a laminate trimmer. I know I reach for my DeWalt trimmer for light work.

Otherwise, just use the ribband to mark the cut with a pencil and do your planing on the workbench, to port and starboard planks at once.

As far as reducing the size of the molds to compensate for ribband thickness...
Find a washer, whose width (from outer edge to center hole) equals the thickness of the ribband stock. While your batten is bent to shape, put the washer against the batten, pencil on the edge of the washer hole, and roll the washer along the batten. The pencil will describe a line, parallel to the batten, at a uniform distance.

Doug Wilde

[EdenRose]

I notched my ribbands into the molds, leaving them the size indicated on plans. A little extra work to cut notches ( I used a router).
I then left the ribbands almost as long as the boat and the bow and stern came out fair.
It was a bit akward as you cannot use the ribbands to define the plank shape between stem and station 1 ( and at stern). You are using a batten on the plank before cutting, which worked out fine in the end.
I still do not know how to spile traditionally
and the boat came out fine. However, I do
want to learn how to define a plank shape
in the traditional way.

[Jim M]

Thanks for the responses.

Yeah, ribbands is what I meant, not battens.

Laminate trimmer, light touch, very careful -- got it.

Reduce the molds by pulling the lines in - got it. But what about the plank lands? I guess the lower inboard corner of the ribband represents one mark, and the lower outboard corner represents the other?

Upper, lower etc. all with reference to the boat when right side up.

I built the Oughtred MacGregor the Oughtred way. Making the set-up was no big deal but determining the plank shapes sure was. They're long, thin and narrow, I think 9 per side. When people talk about the "extra work" involved in fitting ribbands a la Tom Hill, I wonder what they mean. The beveling part is good, but getting the plank shapes with ribbands seems like it would have to be way faster, net; the more planks, the faster.

[Keith Wilson]

I just reduced the molds; why cut all those notches? If you notch the molds, the notch should be wide enough to wiggle the ribands around a bit so they lie in fair curves. I don't trust my lofting to define the plank lands that accurately, so I fiddle with the riband positions, some might say compulsively.

The riband should be just about the width of the lap, so that (with the hull upside down) the lower edge of the upper plank lies on the lower edge of the ribband, and the upper edge of the lower plank lies on the upper edge of the ribband.

I don't trust the ribbands not to bow when using a router to trim the planks, and an unfair curve along a plank edge will look really lousy. I do the following:
- Clamp the plank stock to the mold.
- Trace along the ribands with a pencil. Note that you have to mark the plank BEFORE the previous one is glued up.
- Take the plank stock off the mold
- Cut just outside the line
- Use the rough-cut piece as a pattern for the opposite-side plank
- Clamp the two planks together
- Plane the plank edges to a fair curve, hopefully one close to the line, but a good line takes priority. Nice plank lines are more important than constant width laps.

One has to be careful with the portion of the plank between the first mold and the stem. The riband won't bend fair in this area because the end is unsupported, and if you're not careful you'll get droopy-looking plank ends. I make the riband long, run it out past the stem, establish (by eye) where the plank edge will fall on the stem and mark it, and then cut the riband short, usually right at the first mold. You have to pay particular attention to this area when planing the plank edges fair. For boats with transoms, I build a sort of pseudo-mold inside the transom to which I can fasten the ribbands.

[Don Maurer]

My ribbands were 3/4" x 1/2" and were quite sturdy on my Tammie Norrie mould , with station spacing at about 20". I used the router to trim along the top of the planks (bottom on the mould) . I traced the lower edge (top on the mould) of the planks off the ribbands, but planed them fair by hand on the bench. The top of the plank ends up inside the boat and is less visible, but you want the lines for the bottom of the planks near perfect.

I cut my moulds smaller, and attached the ribbands without notches. I drew out the planks on the original patterns, then drew the cross section of the ribbands on the inside of the plank cross sections. Extending the lines between the ribbands gave me the new mould pattern. This also helped me visualize what was happening at the keelson and transom.

[Sailman58]

Several years ago I took John Brooks' class on plywood lapstrake construction at WBS. We used a spiling batten to get the plank shape from the form. Then used a batten to lay out the shape on the planking. The planking material was stacked so that the planks for both sides were made in one session. The first cut was with a skill saw and the second with a router. I see that John's book is due out this year, and I hope that he describes some of his jigs there. It should be worth the wait.

Ron

[EdenRose]

I trimmed my planks a little proud and then, afte the plank is glued on, used a hand plane along the ribband to finish it off. Using
a power tool as powerful as a router on the plank once it is glued in place and can't be replaced
is pretty scary. Using a hand plane is, on the other hand, very pleasurable.
Fairing the ribbands if notched, did take a little extra work. I made little spacers to raise
and lower the ribband. Some notches I had to
make large, so I had some wiggle room.
As I said before, I would not notch them next time.

[Bill Perkins]

58 I took Johns' course too and await the book . He convinced me that marking and cutting the planks flat on the horses ( in pairs ) useing full length battens tacked in place is the way to go , at least for one boat. The router sits upright and fully supported by the work piece and can run the whole plank edge . Perfect .

[ 10-01-2002, 11:56 AM: Message edited by: Bill Perkins ]

[Jim M]

Between the stem and the next station, would this work -- taper the ribband at the stem end down to the plank thickness, bend it fair onto the stem, hold it in place with a string/clamps or something? That would at least give you the plank shape.

[Meerkat]

From the WB store:

How to Build Glued-Lapstrake Wooden Boats

A quality builder in every sense of the word, John Brooks is also a teacher to aspiring boatbuilders. He makes his living as Brooks Boats on Mt. Desert Island, Maine, specializing in new construction of small craft. Co- authoring the book is John's wife Ruth Ann Hill, who when not building boats, is authoring books, and writing articles for magazines. You'll benefit from her ability to clearly and concisely convert the physical building processes into words.

You'll find this glued-lapstrake mahogany plywood construction exceptionally desirable. The boats are rugged, very low maintenance, and these boats don't leak, and don't need to "swell". John's attention to detail, and his unique, efficient clamping system will make this book a valuable part of anyone's woodworking or boatbuilding library. His unique building jig is easy to set-up, and it allows you to clean up nearly every speck of squeezed-out epoxy, inside and outside the hull, before the stuff hardens. We suspect you'll get about half-way through the book, and then find yourself clearing shop space in between reading the final chapters.

Hardcover, 196 pgs.
Available Winter 2002

WB print catalog said December, but publishers are only slightly more reliable then a politician's promise as to delivery dates.

[Sailman58]

It's gotta be getting close, they have been pushig the date back for close to 18 months now. The article in WoodenBoat Magazine was part of the book, so we know that part of it is done.

[rhickman]

If the moulds are reduced by the ribband thickness, do the moulds still need to be faired to allow the ribbands to lay flat? Previous replies seem to indicate they do not have to be faired. Trying to visualize this is making my head hurt. I bet it is going to be hurting a lot more before I am through with this boat....

FYI, I am building a whilly boat and this is a first time project.

[DougWilde]

I don't remeber it being a problem. Any mismatch (i.e., gap between plank and ribband) is small and of little consequence.

But what you must do, be obsessive about, make a fetish of, is scraping away, wiping-up, and otherwise removing any epoxy squeeze-out before it kicks. It is SO MUCH EASIER to attend to while soft, compared to sanding latter on. Use brown packing tape on the ribbands rather than wax or paraffin.

Doug Wilde

[rhickman]

Thanks Doug. I am going to put on the ribbands. I am not worried about a little extra work. Sounds like a safe approach. The moulds have actually been cut already so I need to reduce the size to accomodate the ribbands. Would you recommend extending the ribbands to the stem? Seems like it would be easy to blend the ribband right into the stem but not many people are talking about doing it that way.

Robert

[JimConlin]

In building my 'Liz', I didn't decide to use the ribband method until after i'd gotten the molds out and set up. Call me goofy. So, I marked the approximate locations of the plank joints and, with a router and a template, cut notches in the molds maybe 1-1/2" wide and 3/4" deep. The ribbands were 1/2" x 3/4", on edge. A touch with a rasp adjusted the depth of the notch as needed. To refine the lining-off, I held the ribbands in the notches with wedges. These made it easy to shift a ribband by a fraction to get it fair. When I was happy with the fairness of the lining off on one side, I duplicated it on the other and screwed the ribbands to the molds and covered them with tape.

I did not extend the ribbands to the stem and should have done something here, as I got a small unwanted bulge in the planking. Next time, I might try controlling the spread of the ribbands in the first frame bay either by extending them to the stem or with a light plywood web between opposing pairs of ribbands. Then again, maybe planking stock more substantial than 4mm okoume would have been less wayward.

I did not sense any lateral deflection of the ribbands under the pressure of the router. All of the edges were cleaned up with a small rabbet plane later in the process.

[chrisk]

In order to reduce the moulds to fit say 1/2" ribbands you could run a router across them with a 1/2" rabbet bit about half the depth of the mould thickness or more. Then run a second pass with a flush trim bit to bring the other side of the mould down to the rabbet depth. If you got the original mould shape correct this should put the ribbands pretty close to the correct shape of the
original moulds.

[Don Maurer]

I ran the ribbands out to the stem, but they don't take the same curve as the strakes do between station 1 and the stem. It does give you a nice fair curve between stations 1 and 2. If the ribbands end at station 1 or just beyond, the curve between stations 1 and 2 flattens out a bit.

[DougWilde]

No need to extend the ribbands to the stem. Just end them somewhere forward of the last station. You'll install the keelson and attach the stems next. Then you'll mark the location where the strakes will fall on the stems. After offering up the planking stock and marking the the bottom edge (top of the stock 'cause you're building upside down) and the mark from the stems, take the stock to your workbench and, with a batten, strike a fair line out to the stem mark.

JUST REMEMBER TO MARK AND CUT THE NEXT PLANK BEFORE INSTALLING THE LAST ONE.

Doug Wilde

[Bill Perkins]

Just as a matter of interest ( it may be academic ) if you simply subtract the riband thickness from the moulds you won't be exactly reproducing the designed shape . If the ribands are at least 3/4 in. thick and the bow of the boat is full , so the planks sweep sharply in toward the stem it might make a difference , especially if you're using other templates that assume the designed shape has been held .

If a 3/4 in. riband crosses the forward most mould at an angle of 60 degrees for instance , its' thickness in the plane of the mould is about 7/8ths of an inch . A 45 deg. intersection yields an effective thickness of about 1 in. One poster mentioned notching the designed mouldes the thickness of his ribands , then deepening the notches where necessary . I'm talking about the reason that adjustment was necessary .The notchers have the advantage of preserving the intended profile of the station mould , and fiddling untill the riband sets flush with that .

[ 10-16-2002, 12:17 AM: Message edited by: Bill Perkins ]

[rhickman]

I just got finished reducing the moulds to accomadate a ribband thickness of 1/2". The width of the ribband is 3/4", which represents the overlap of the strakes. I used a small section of ribband (up against the mold like it was notched in place) to mark the bottom edge of the ribband at each plank land. I then connected the dots to give me the reduced pattern. That bottom mark is the land point for ribband. The top outer edge of the ribband will be in the exact location of the plank land from the original pattern. This yields the same results as cutting a notch since the ribband is in the same spot.

Just offsetting the pattern lines and taking the intersection as the land point does not replicate the original pattern but it is actually only 0.080" off. Does that confuse everyone because it sure is hard to explain.