Bram, Greg, and the Swift Solo BB,
Having spent about 7 years of my life engineering and selling CNC and robotic
profiling equipment, into a variety of industries, I feel competent to comment
about the accuracy and repeatability of the technology.
There is absolutely no question that CNC, or robotic equipment will produce a
set of components to a level of accuracy that it is almost impossible to
achieve manually. And that accuracy will be repeated time after time - every
set will be the same as its predecessor. Exactly, to within a couple of
thousands of an inch or hundredths of a millimetre. However, this is only true
if the tooling is kept sharp, the tooling offsets are accurately set, and the
bulk material clamping is consistently secure throughout the entire process.
But philosophically, in terms of the effect on the class, and the performance
of each boat, all of that is almost immaterial.
As an open development class, the hull dimensions are to be controlled, as Bram
has said, to within plus or minus 1/4" of the design section profiles, (and
consequently, the waterlines, buttocks and diagonals).
Within that envelope, there is continuum of accuracy possible for anyone
attempting to build within the rules, rather than bend them.
At one end, there will be the roughest of home builder, who, with even limited
care in cutting and without sanding the station forms, should be able to jigsaw
them to within, at most, 1/8" of the line.
To produce a profile with a tolerance any wider than that would mean that the
builder was either totally careless, vision impaired or physically uncoodinated
or both. It is unlikely that someone with any of theses disabilities would
choose to build such a fast, physically demanding skiff design as the Swift
Solo where all three capabilities will be required to effectively (and safely)
sail it.
At the other end of the scale is the high volume licenced production builder,
who, for reasons of speed and economy, will have the components CNC or
robotically machined.
In between, will be the average home builder or the low volume licenced
production builder, whose output will be somewhere between those accuracy
extremes. In my opinion, (which supports your guess Bram), most of these would
be well within 1/3rd of the tolerance (1/6" or about 4 mm total). The majority
(also in my opinion) would be well under about half of that (less than 1/10" or
about 2 mm total). The most careful, and skilled, of the home or low volume
constructors will be able to approach the accuracy of the CNC profiled
components.
If the intent is (as I believe it to be) to keep the class rules simple but
effective, then again, in my opinion, there is no good reason to introduce
complexity
All of these production methods will produce a boat that measures, and conforms
with the rules, and with the intent of the rules.
A long winded response perhaps, but as I see it, there is absolutely no reason
to introduce an amendment that requires one set of measurements for hulls
produced with CNC equipment, and another for those produced manually. To do so
would introduce unnecessary complexity. It would also produce two fleets,
rather than one, with, in all probability, no discernable performance
difference between them.
Seems to me also, that the licence fee and registration fee issue is crystal
clear. You either want a boat that conforms with the class rules, registered
with the class, that measures, - or you don't.
If you do - you pay $375, provide proof of correct construction and get it
officially measured. You receive the appropriate documentation and you go
racing with the fleet.
If you don't, you cheat, and somehow get around paying and providing proof of
construction or having it measured. In this latter case, don't ever expect to
race with the rest of the fleet.
Simple really.
On another subject, I'd personally like this coming weekend to more fully
peruse the rules and these latest suggestions. So far they look logical,
understandable and enforceable.
Thanks for soldiering on with the process, the design and the class. It
promises to be very exciting. The issue of rules seems to be approaching
finality, despite the vexations.
Regards, Ron Deane,
Brisbane, Australia.
----- Original Message -----
From: BDally6107@xxxxxxx
To: swiftsolo@xxxxxxxxxxxx
Sent: Wednesday, November 26, 2003 11:30 AM
Subject: a possible amendment
Eldon is proposing an amendment that would either disallow or require
different tolerances for CNC boats. If there is support for this view please
post it on the list server and we will entertain such an amendment.
A bit of history and some facts and opinions to consider.
I. I am against such an amendment
II. You are required to build your boat within a Ââ (12MM)
boundary. That is Ââ (6mm) each side of the lines on your station
templates. If you are having trouble cutting your stations to that tolerance
you should definitely support this idea.
III. My guess is that there is not a set of templates out there
that approaches 33% of that margin for error.
IV. The broader the tolerance, the more likely that someone will
redesign the boat to get around the intent of the rules. While the rules are
clear that the measurer is to disallow such attempts, this is subjective and
lends itself to litigation. The actual difference in tolerance between hand
cutting and CNC should be about 1/16â for someone with average skills using
some care.
V. The reasons for changing my stance and allowing CNC to a
limited number of certified commercial builders include the following: Our
new DN ice boaters Michael and Randy (blame them) convinced me that they would
like to have the option of buying not only the stations but also the completed
bulkheads and transom and possibly other parts. I asked VMG Skiffs (John,
Lynn, Pat, and Anita) if they were interested in providing these parts to the
class and they said yes. This will allow someone who wants to build their own
boat but is in a hurry to complete the project in half the time. It will, of
course, cost more. VMG Skiff will be required to pay the cost of certification
(travel expenses, lodging, etc.) and to collect and pay each required license
fee. The big advantage is that the machine can do this work in 1/10 the time
or less.
Please respond if you have support for Eldon's amendment that would either
disallow this CNC service to the class or require them to have different
tolerances. We will put a hold on composing the final draft until you have had
20 hours to respond. If there is support we will end debate have Eldon draft
the amendment, and âcall for the questionâ tomorrow at 2pm. Because it is
Thanksgiving weekend in the USA we will postpone voting on the final draft
until Monday the 1st of December.
Eldon, Please prepare the language for the ammendment and post it ASAP.
Bram
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