MODIFY THOSE BOAT PLANS???
Not all boat designers care to see their plans modified. It's true
some changes will be an invitation to disaster but here is how I feel
about it. Most of you go to work each day and get told how to do
everything, even though you may know a lot more about your job than
the boss. So when you come home to follow your hobby you really don't
want to be told to just follow the plans and shut up. Your hobby is
your chance to be creative, maybe the only chance in your life. True,
you could take your boat plans and add different trim or fittings.
But a lot of you, probably most of you, are capable of a lot more
than that. You could go higher, lower, wider, narrower, shorter or
longer to start with. You might move everything around (maybe for a
good reason), change the rig, etc, etc. Then you are on the road to
being your own designer.
I recall in the old Small Boat Journal a reader writing to Phil
Bolger, who had a regular boat design essay each issue, whether he
could simply scale up a given design (of a dinghy in this case) to
get something more suitable for his use. Phil said, "Yes, go right
ahead." But added such a change would give a new design and that the
reader, not Phil, would be the boat's designer. You see, almost any
boat is a rework of a previous design.
I don't think Phil minded folks changing his plans much, as long as
it was done with some thought and the builder would take the blame
for any blunder. I don't mind it much either. It's cool to see what
you guys will come up with!
START WITH SOMETHING EASY...RAISING THE ROOF...
As an example of a simple major change, let's say a fellow wants more
interior room and is bound to raise the cabin roof a bit to gain it.
Now, if the boat is designed with plumb sides, like many Bolger box
boats and I've followed along those lines, it isn't hard to figure
out how to do it by looking at the plans. Like a normal box house,
you make the walls higher and the roof will go with it. Take a look
at the new Australian Scram Pram, a capture from the youtube
video.....
Greg Flemming raised the roof a few inches in construction and I
never noticed it! Ross Lillistone who completed the details said he
wasn't sure of that also, but added it had plenty of headroom inside.
It's a very simple change to make and can really enhance your
interior life.
Now, if you have a hull with flared sides it won't be so easy.
Because the boat gets wider as it gets higher and you will need to do
a lot more head scratching and moan chair sitting to figure it out as
you go. But I'll bet you can still do it.
THE DOWNSIDE...
But there are usually downsides to this. To me the real problem is
that when you raise the cabin roof, you will need to raise the
cockpit in order to see over the taller roof and when you do that the
crew weight is also moved upward. On my boats the crew weight is a
significant percentage of the total so the ability to stand up to a
wind is reduced. Also coming into play here is that the sail rig
would probably also be raised upward giving more heeling in a given
wind. These things apply mostly to the usual sailing cabin boat, not
so to a powerboat or a birdwatcher cabin type sailboat.
(By the way, raising the cabin roof should improve the self righting
ability of a knock down sailboat because buoyancy up high is an
important part of the righting equation. If you go too far with this
you can get a sailboat that is very tender to sail - always wanting
to tip over but always self righting.)
Another downside is the looks. Everybody wants a long lean looking
boat. Even Bolger told me once that I needed to improve the looks of
my boats. "Try making them longer and lower," he told me, the man who
invented the LooseMoose! Herreshoff boats had that long lean look but
as they would say about standing headroom, "What are you going to do
in there - sleep standing up?" Best to not ask a designer to draw a
boat around an outhouse either!
There is also the ever present problem involving the sizes of common
materials. If your boat was designed for 4' deep sides, if you go
deeper you will need to start scarfing plywood or something. Most
designers keep this sort of material sizing in mind as they draw
plans.
WIDER AND NARROWER.....
This is a really tough one. In olden days plans were simply lines
drawings with a table of offsets that allowed the builder to draw
full size on the shop floor. From there he made all the detail
measurements he needed to lay out the real boat. Today's "instant"
building, with all the major element shapes predefined on the
drawings, eliminates that step (plus the need to make many forms and
templates and have a shop with a floor that is capable of mounting
all of those solidly). So I suppose in the olden days a fellow might
say,"This boat is designed to be 4' wide but I'm gonna go to 6' wide
by multiplying all the breadth dimensions by 1.5". That would work
then but not with "instant" plans because all of the panel shapes are
defined either by drafting or computer work to the original offsets.
Make the boat wider or narrower and none of the pieces will fit even
if you expanded the breadths of the bulkheads and such correctly.
I don't recall anyone wanting to modify one of my boats this way so
perhaps it is not a big deal. But if you try to do it I'd say the
kicker is that the roll stability of the boat will be affected way
beyond what you might expect. I've never sat down to figure it out
and that would be an interesting study. But perhaps the stability is
affected as the cube of the beam, that is to say if you doubled the
width of a hull, leaving all else the same, the new hull would be 8
times as stable in roll. That is not so much the worry as going
narrower. Let's say you decide that you can stand up to fish in a
boat that is 3' wide. Then you decide your next dreamboat will be a
faster 2' wide. The new boat has less than 1/3 the roll stability of
the old. ( I need to study this more but the fact is you can easily
stand in a 3' wide Bolder Teal, and easily fall out of the 2' wide
Bolger Light Dory as Phil said happened to him.)
So I guess my advice here is never modify a set of complete plans to
go wider or narrower. Start with a fresh design on a new piece of
paper.
MOVING BULKHEADS...
This is fairly common. The usual effort is to move a cabin bulkhead
to get more room in the cabin. If you aren't modifying the basic
lines you should be able to scale off you new bulkhead from the plans
and figure it out. The bevels of the new bulkhead may not be obvious
but they are easily checked once you have the hull started, as in
olden days when no plans included bevels.
HIDDEN TRAPS...
I use bulkheads to divide the hull into sections and to force the
crew to sit where they are supposed to. Doesn't always work but you
have to try. So, for example, if you omit the bulkhead that forms a
stern box and run the cockpit clear to the transom, and then use that
extra to give a larger cabin, you can expect the boat to be way out
of trim when the crew gets loaded towards the stern.
I think experienced boaters are always very aware of fore and aft
trim and new boaters are never aware of it. So you can almost tell
how salty a sailor is by how he trims his boat. The late and great
Thomas Firth Jones had a cool story about this in his book "Boats To
Go". As I recall, he designed and built a mid size sail cruiser for a
customer. He was very pleased with the results but the buyer was not.
The buyer insisted on wheel steering instead of tiller steering and
insisted the boat be modified. Aside for the cost of the wheel
steering Jones was dreadful of its weight, plus the skipper's weight,
being in the extreme stern of the boat. But the boat was modified for
the buyer. Tom said the result was the terrible trim he predicted,
and that the buyer was completely happy!
And, by the way, leaving out buoyancy boxes that are supposed to save
your ass in a swamping is not thoughtful, but it is done all the time
I'm afraid. I might add that most buoyancy boxes are minimal for
this, we really should be designing them larger as I saw demonstrated
at the SailOK in 2012. I think that this sort of safety design is an
art to itself and I am not an artist. Not only must there be enough
emergency buoyancy, it all has to be in the right places to support
the swamped boat in a way useful for self recovery. Having it all in
the stern or the bow is not the correct answer.
Actually there is more to the bulkhead thing in that bulkheads are
also there to distribute sailing loads, especially mast and leeboard
(or daggerboard or centerboard or keel) loads. I've seen some
distiguished boats with problems this way - they get sagging rigs,
loose keels, and such over time. Not so much a problem in olden days
when boats were made of thick lumber (although the old carvel planked
hulls would warp mightily over time) and the sailing rigs were much
less taut than today's. So if you move a bulkhead that supports a
mast fitting, maybe the mast needs to be moved with it. It's
something you need to consider. I'll get to that later in the series
because it seems to be the main trap that hull modifiers fall into,
at least for my designs.
It's closely related to the "longer and shorter" of it and we will
get to that next issue....
Contents
Larsboat
LARSBOAT, DOUBLE PADDLE CANOE, 15.5' X 30", 65 POUNDS EMPTY
Larsboat was built by Lars Hasselgren to replace a Folboat that had
finally met its end. Lars wanted capacity for two, plus decking, as
with his old boat.
I took Toto and lengthened it with a 30" plug in the middle to gain
capacity. But lengthening a hull with a straight plug like this
usually improves a boat in almost every way and Larsboat should be
faster than Toto in good conditions. In this case the plug meant I
didn't have to refigure the shape of the twisted bow panels as I
would if I'd lengthened Toto with an overall stretch. (I can figure
twisted panels pretty reliably now, but not back when Toto and
Larsboat were drawn.)
The decking was quite simple because even the original Toto could
take a forward deck of flat sheets with a center peak. I should add
that I feel the decking is very optional. This prototype weighs 61
pounds and deleting the deck might cut another 10 pounds or so. The
undecked boat also would have a better cartopping shape. I'd keep
the stern chamber. It will ease your mind about taking a big wave
over the stern.
This would be a preferred project for someonw who intends to do a
lot of cruising and camping. In the Toto camping I've done the
sleeping room has been OK, but the storage is limited. Larsboat
would be better both because of increased capacity and because
there is dry storage under the bow deck.
The basic hull is taped seam construction needing four sheets of
1/4" plywood for the decked version and three sheets for the
undecked version. No jigs or lofting required. Plans are two
blueprints with keyed instructions for $20.
The photo above is of Bob Smithson's Larsboat. He customized the
decking a bit. I think he also built the boat of 1/8" ply to save
weight. I've forgotten what his boat weighed but he did say it was
sufficiently rigid for him.
Bob Hoyle built this one without a deck down in Florida:
Paul Moffitt built this one. You can see this is a much better two
person boat than the shorter Toto:
And remember Garth Battista's vertical Larsboat?
And the old outboard motor guru Max Wawrzniak often goes for a
paddle in his Larsboat:
Larsboat plans are $20.
Contents
Prototype News
Some of you may know that in addition to the one buck catalog
which now contains 20 "done" boats, I offer another catalog of 20
unbuilt prototypes. The buck catalog has on its last page a list
and brief description of the boats currently in the Catalog of
Prototypes. That catalog also contains some articles that I wrote
for Messing About In Boats and Boatbuilder magazines. The Catalog
of Prototypes costs $3. The both together amount to 50 pages for
$4, an offer you may have seen in Woodenboat ads. Payment must be
in US funds. The banks here won't accept anything else. (I've got
a little stash of foreign currency that I can admire but not
spend.) I'm way too small for credit cards.
I think David Hahn's Out West Picara is the winner of the Picara
race. Shown here on its first sail except there was no wind.
Hopefully more later. (Not sure if a polytarp sail is suitable
for a boat this heavy.
Here is a Musicbox2 out West.
This is Ted Arkey's Jukebox2 down in Sydney. Shown with the
"ketchooner" rig, featuring his own polytarp sails, that is shown
on the plans. Should have a sailing report soon.
And the Vole in New York is Garth Battista's of
www.breakawaybooks.com, printer of my book and Max's old outboard
book and many other fine sports books. Beautiful job! Garth is
using a small lug rig for sail, not the sharpie sprit sail shown
on the plans, so I will continue to carry the design as a
prototype boat. But he has used it extensively on his Bahamas
trip towed behind his Cormorant. Sort of like having a compact
car towed behind an RV.
And a Deansbox seen in Texas:
Another prototype Twister is well along:
And the first D'arcy Bryn is taped and bottom painted. You can
follow the builder's progress at http://moffitt1.wordpress.com/
....
Contents
AN INDEX OF PAST ISSUES
THE WAY BACK ISSUES RETURN!
MANY THANKS TO CANADIAN READER GAETAN
JETTE WHO NOT ONLY SAVED THEM FROM THE 1997 BEGINNING BUT
ALSO PUT TOGETHER AN EXCELLENT INDEX PAGE TO SORT THEM
OUT....
THE WAY
BACK ISSUES
SOME LINKS
SOME
LINKS
Mother of All Boat
Links
Cheap Pages
Duckworks
Magazine
The Boatbuilding
Community
Kilburn's Power
Skiff
Bruce Builds
Roar
Dave Carnell
Rich builds AF2
JB Builds AF4
JB Builds
Sportdory
Hullforms Download (archived copy)
Puddle Duck
Website
Brian builds Roar2 (archived copy)
Herb builds AF3 (archived copy)
Herb builds RB42 (archived copy)
Barry Builds
Toto
Table of
Contents
