Eldon,
I also claim some competence in the boat building arena as well as in CNC
profiling, having completely built 3 boats and participated substantially in
the building of two others. In addition, I have also worked professionally with
a large number of CNC profilers cutting components for boats, and shipbuilders,
including the contractors building frigates for the Australian Navy.
Of the boats I have personally built, all were of timber construction, 2 in
stitch and glue, the other - a 7.8m (26ft) trailable yacht was strip planked in
Western Red Cedar using bead and cove strips. All were boats built to rigidly
enforced class rules. I have another under construction.
In my experience the definition of what constitutes "plans" for a boat really
depends solely on what the designer, or the owner of the plans, decides is
necessary for a builder to be able to construct a vessel that complies with the
class rules. (Or complies with the performance specification, in the case of
military vessels.)
On the first boat I built, a Mosquito catamaran, (a 16 ft Tornado lookalike
with two on trapeze) the "plans" were quarter scale dimensioned drawings of the
ply panels only, with a list of critical finished hull dimensions. Accompanying
them were a series of typed sheets of instructions and sketches of the rig,
centreboards, rudders and trampoline.
Hundreds of Mosquitos have been built using the same plans. About 98% of them
measured on the first pass. all but one or two on the second pass.
Plans for the second boat - a 7.8m Lidguard strip planked trailable included a
one tenth scale lines drawing, a rig layout, a table of offsets and six pages
(only) of typed instructions. To ensure fairness of the hull, I lofted the
lines full scale on the garage floor using straight edge, square and measuring
tape with story sticks. The class numbers more than 50, less than 100.
Although the lines were accurate, confirmed by intersection of section lines,
buttocks, diagonals and waterlines, the section forms were only as accurate as
I could duplicate them. Similarly the alignment of forms was as accurate as I
could get it with a tensioned wire centerline and a plumbob.
The advantage with strip planking is that the strips are self fairing, so even
if there were any unfairness in the forms, that was very evident once I began
applying strips. (So unless you produce hollows in the forms, or oversand some
sections of the planked hull, you never need fairing filler.) The end result
was not only beautifully fair, but also very competitive - in one season, our
family, (my wife and I and four kids aged at that time from 10 to 16) won 12 of
a possible 14 trophies in one of the most competitive trailable yacht fleets on
Port Philip Bay, Victoria, Australia.
Incidentally, a friend who lofted his Lidguard to only one quarter scale, then
scaled up the forms from it, finished with inaccuracies and resultant hollows
in the bow which were ultimately filled with fairing compound. The total
increase in weight for a panel each side of the bow, averaging about 3mm thick
and 600mm diameter was less than 0.5 kg. (About a pound) So although you
shouldn't need it, even if you do, the weight penalty is absolutely minimal.
The third boat I built for the kids - a sabot training dinghy. That came with
"plans" that were full size (paper) bulkhead patterns and dimensioned drawings
of hull panels. Thousands have been built using the same process.
With the most recent of the boats on which I have assisted construction, a 23ft
Tolman skiff (Alaskan outboard powered fishing dory in stitch and glue) the
"plans" consist of a detailed instruction manual of about 80 pages. The boat
does not have line drawings - none exist - not even with the designer. The
design has been developed empirically from what works. Hundreds have been built.
The largest boat I have assisted on construction of is a 14m steel hulled
cruising yacht, - a scaled up version of an 11m three-time winner of the Sydney
to Hobart yacht race. Although built as a cruising yacht, we ocean raced it
extensively around Victorian and Tasmanian waters, regularly placing about mid
field in a mixed fleet that included some rocketships. The "plans" were the
original lines drawings and table of offsets for the 11 m original. The scaling
up was done as each frame was built. It was a one-off. Last time I heard of it,
the boat was being used for adventure sailing cruises from Cape Horn to
Antarctica.
The boat I have under construction is a One-Oceans Cape Ann Storm sea kayak -
strip planked. The "plans" consist of a set of undimensioned lines drawings,
and a set of paper templates to be cut out and glued to the forms. Hundreds
have been built using the same process. In fact all of One Oceans strip planked
designs and those of Guillemot Kayaks - the two most popular strip built sea
kayak designers are offered this way.
Therefore, to suggest that, to be "accurate" you must have accurately cut mylar
templates or cnc cut forms, to achieve a fair hull that measures, or conforms
with the designers intent, is, in my opinion (and my experience), quite
frankly, utter nonsense!
If you want a full set of lines drawings, take the section forms for which you
have paper copies, measure them accurately, and loft a full size lines drawing,
- or enter them in a CAD package like MacSurf, and reengineer them - you'll
probably be able to get within 1 or 2 mm of the mean all over. You could even
provide the output in a DXF file to a CNC profiler and have them cut the forms
for you.
But I'll bet that none of that helps you produce a more accurate boat. Or a
faster one.
And nor will it help the certified builders any more than what you have in your
hands already. It might make the process faster and less costly, but no better
in terms of final output.
Unless someone uses a digital representation of the hull to drive 3 axis
milling machine or router over a planked hull to finish machine it, no-one is
going to get closer.
Careful gluing of the paper templates to the forms using a spray-on contact
glue,(to minimise size change), careful alignment of the forms and careful
stripping will guarantee a fair hull. If you then carefully use a fairing
board, till you think your arms are about to drop off, you will have a hull
form that is as fair and fast as it is going to get - whether it was built on
CNC cut forms or on hand cut forms.
Besides, half the joy of sailing a boat you built yourself is being able to
say, proudly and truthfully, "I built it myself, with my own hands". The other
half is the joy of the building process itself.
All enjoyment that comes from actually sailing it effectively, is pure cream!
Instead of nit-picking any further and continuing to attack Bram personally, I
would suggest you wait till the full set of rules is published within the next
day or two, with graphics and drawings and review them. I am sure you will then
be able to satisfy yourself that with the plans you have, together with the
reference points in the measurers guide, that with a little bit of effort, you
will be able to build a boat that measures, within the plus or minus 6 mm
tolerance of the mean. That boat will be competitive, if you sail it
effectively.
I am sure that you will then be able to look for ways that you can actively
contribute to the advancement of the class.
Happy building.
Ron Deane
Brisbane, Australia.
----- Original Message -----
From: Harveynestor@xxxxxxxxxxxxx
To: swiftsolo@xxxxxxxxxxxx
Sent: Thursday, November 27, 2003 1:11 AM
Subject: Reasons For Proposed Amendment to Class Rules
Fellow Swift Solo Sailors:
As many of you know, I have proposed that our class rules should be written
such that either:
(a) boats built with the use of CNC technology should be prohibited or
(b) alternatively, some different measurement rules should be used for
boats built without the use of CNC machinery.
These are the reasons why I have made this proposal:
1. Bram has not provided us with plans to build our Swift Solos.
Plans are lines drawings that show a hull in three views--profile view,
plan view, and body plan view. They are typically provided on mylar that does
not change shape with temperature and humidity or else as CAD files. These
drawings enable a builder to check his measurements as he progresses with the
construction of his boat. Without plans we cannot check our measurements as we
build our boats.
2. In lieu of plans, Bram has provided us with station templates printed on
paper.
Station templates are typically made by either (a) drawing plans out
full size and taking measurements from them or (b) a computer process if a CAD
file is used.
The paper templates provided by Bram are subject to changes in both
size and shape as a result of humidity and temperature changes. The paper
templates are also subjected to some moisture when they are glued down to cut
out the mold stations and will ultimately produce construction problems such
as:
(a) the mold stations are not the precise size and shape that
they should be
(b) the mold stations are not perfectly aligned,
(c) the jig is not fair
3. Any errors resulting from the use of paper templates will produce a jig
that is not fair.
The only ways to fair a hull built on an unfair jig:
(a) fair the hull before glassing,
(b) fair the hull after glassing by building up low spots with
fairing compound,
(c) some combination of (a) and (b).
(a) Fairing the hull before glassing reduces the core thickness and
weakens the hull.
Western Red Cedar is a very high density core material, and its weight
and the class rules prohibit using a core thickness greater than 1/4".
Sanding an already thin core material reduces stiffness that is obtained
through panel thickness.
(b) Fairing the hull after glassing by building up low spots with
fairing compound adds otherwise useless weight to the boat.
Large amounts of fairing compound increase the weight of the hull
needlessly. This weight could be better used to strengthen the hull.
4. A boat built from a jig constructed from paper moistened with glue and
then cut by hand with a jig-saw pales in comparison with a boat built from a
jig cut with CNC machinery.
A blind man with a CAD file and CNC machinery could produce a jig far
superior to one produced by a skilled craftsman with 20/20 vision using
moistened paper as his pattern and cutting the wood with a hand-held jig-saw.
www.fabricam.com has a very good picture of a CNC router table. Can
your glued paper mold stations and jig-saw compete with this equipment
available to Patrick Owen and John Vinkemuhler of VMG Skiffs?
5. Bram claims that the use of CNC machinery to produce bulkheads, mold
stations, transoms, and misc. would be a service to the class, and to deny the
use of CNC machinery would be a disservice to the class.
Would it not be a better service to the class to level the playing
field by either (a) allowing ALL builders to use CNC machinery, provide them
with the mylar templates, CAD files, etc. or else (b) not allow the use of CNC
machinery by any individual or certified builder.
6. The use of CNC machinery by certified builders only starts the class down
the slippery slope of a class dominated by certified builders.
This would move the building process one step at a time out of the
hands of class members and pave the way to allowing design and construction
changes that could obsolete hand crafted boats.
7. Bram touts his concern with fairness and foiling "cheaters" who might try
to gain an unfair advantage by altering his design.
Bram apparently fears that there are some or many among those
approximately 50 constituting the Swift Solo class building their own boats who
would use "builder error" as a cover for redesigning his Swift Solo and thus
build a more competitive boat.
Fairness dictates that the approximately 50 people who have
purchased plans at the cost of $575.00 should be allowed to build competitive
boats that are equal to those built by his certified builders.
8. The unfair advantage definitely goes to the certified builders who are
allowed to use CNC machinery.
We, as individual builders who are denied plans and/or measurement
templates with which to check our hand crafted boats cannot hope to achieve the
precision and accuracy of computer driven machinery. Bram's subjective test of
allowable "builder error" might force sailors who would otherwise build their
own boats to purchase boats from his certified builders at several times the
cost of building their own boats, thus destroying an aspect of the class that
first attracted us to it; otherwise, why else would we have paid $575.00 for a
set of plans (which we have not yet received)?
Alternatively,
#1. If the class feels that CNC capabilities should be allowed,
then CAD files of the plans should be provided to ALL builders who have paid
for plans, not just to Bram's certified builders,
OR ELSE
#2. Different rules should be used to measure the dimensions of
non-CNC boats so they can be as well built as their CNC counterparts through
fairing of the jigs upon which they are constructed before they are built.
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