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From: Aaron Ross, President American 505 Section
Sent: 19 June 2003 17:16
To: 505world-list
Subject: 505 mast rule - Larry Tuttle
Forwarded with permission from Larry Tuttle of Waterat.
----- Original Message -----
From: Larry Tuttle
To: "505west"
Sent: Wednesday, June 18, 2003 10:49 PM
Subject: 505 mast rule
As the builder of the carbon masts that won the 1981 & 1982 Worlds, I
want to comment on the proposed carbon mast rule.
With all respect to those who continue to volunteer their time to the class for all aspects of class management, I find specific areas in the
proposed rule that I believe are not in the best interests of the class.
As a result, I recommend that the class members vote against this rule change.
- Rule 7.2.1 maximum transverse dimension of 64 mm.
The most economical way to build masts is from round tubes. There are many manufacturers worldwide who can build tubes to a designers
specification. Round tubes also can be built more easily in two pieces and joined than a shaped section. The I14 is an example of a
high-performance class that chooses round tubes.
The problem is that a tube larger than 64 mm may be required for a reasonable mast. There are several ways to accommodate the mast gate
restriction - taper the mast to fit the gate, make the gate wider, or deck step the mast.
The rule should let the customers decide which is preferred and not mandate this aspect.
- Rule 7.2.6 minimum weight
This does not protect those who continue to use aluminium masts for the transition period. This provides incentive to build a mast that is
greater than 2 kg lighter, add the 2 kg corrector, and have a mast that is lighter, has better bend characteristics, and better aerodynamics.
Any serious sailor would need to have one.
The only way I perceive to make a fair transition period is to put a minimum weight on the carbon mast that is significantly over the
aluminium mast. That rule would read something like 'the mast with standing & running rigging shall weigh 12 kg. Any correctors must be
placed a minimum of 3000 mm above the deck band'. This way we can build
a base mast of any weight, and the sailor using it will have the advantage of better bend characteristics, and better aerodynamics, but
will carry a weight and moment of inertia penalty.
The proposed rules provide significant incentive to build with more expensive materials and methods to meet the
athwartships dimensions with
a minimum weight mast.
Defining and weighting rigged masts is a very simple procedure, and that
should not be consideration when implementing a rule change of this magnitude.
- The proposed rule does not include an effective date. It should become effective immediately after a worlds, so there is ample to adapt
and prepare for the next event.
While there are some other assumptions about what builders or sailors may do that I disagree with, these main issues are what is important for
making a reasonable transition to carbon masts.
Regards;
Larry Tuttle
Waterat Sailing Equipment
1041-C 17th Ave P.O.Box 2790
Santa Cruz, CA 95062 USA
From: Simon J Lake
Sent: 24 June 2003 15:55
To: 505world-list
Subject: RE: 505 mast rule- Larry Tuttle
A response to Larry's observations from a member of the Carbon Spars sub
committee.
Please remember that Thad Lieb was a member of the Carbon Spars sub committee and that he has significant experience designing carbon spars
for AC yachts. His contribution on technical issues is reflected in the proposal.
Rule 7.2.1 maximum transverse dimension of 64 mm - this was included to prevent very light thin walled (large diameter) spars being built. By
their nature these would be very fragile and prone to damage and therefore not in the best interests of the class. The dimension was
arrived at as if was felt that 2" (~50mm) tubes are generally available throughout the world and that this leaves up to 7mm wall thickness
available which was felt to be more than enough.
Rule 7.2.6 minimum weight - this is a transitional rule and as such was
amended by the IRC to one which is easily enforced. To my knowledge there was disagreement with this change from the members of the Carbon
Spars sub committee. The original proposal along the line that Larry is suggesting was thought to be very difficult and time consuming to
enforce and that as a transitional measure something more practical was required.
It is my hope that Association members will do as much research into this subject as possible, and arrive at their own, considered, opinion
before voting in the ballot.
It is NOT the place for Larry Tuttle, Clive Watts or any other individual with a commercial interest in the class to advise Association
members on how to vote. They are, of course, entitled to their opinions,
and if they are boat owning members of the Association, they may influence the outcome of the ballot by casting their vote in any way
they wish.
Regards,
Simon J Lake
Chairman Carbon Spars sub committee
GBR8835? - hopefully sometime very soon.
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