Hi all, I have been slowly improving a Tony Abel Mandarin boat over the last few months. I first started with new new bulb and fin, and now I am now in the process of updating the rigs. Ive lowered the jib as much as possible and am now looking at lowering the main boom. Lower limit on the mast is at 68 mm. Being a flat decked boat the deck limit mark is just fore of the mast slot, which is approximately 23 by 11mm in size. With the new fin the mast is in the front of this slot. I would like to get the main boom as low as is possible but my gooseneck is about 65mm long. 

So my questions are:

1. Does shortning the body of a gooseneck change the angle of the kicker to boom and therefore change the pressure on the leech to twist off or is it self balancing and you just allow for it in set up.

2. Am I allowed to drop the screwhead of the gooseneck below the deck limit mark. There is enough room for it to swing without fouling. This then allows me to bring the lower band to the 60mm mark. 

3. Because I like to change things and be mischevious, and Mandarin being a wooden deck this would be really easy, would I be allowed to put in a small well. This would be about 2 cm diameter and 1 cm deep behind the mast in the deck that would allow me to drop the gooseneck further and then place the deck limit mark within that well. I'm not sure its in the spirit of the rules but was just interested   

I know these may seem stupid questions but i was just interested as I could only find Rule D1.5 re the limit mark. I am sure there must something elsewhere but I couldn't see it.

D.1.5 DECK LIMIT MARK
The deck limit mark shall be displayed on the centre plane of the hull near to the mast position. It shall be a minimum of 5 mm in diameter.

Feel free to criticize my mistakes, i wont take it personally, as its often the quickest way I learn

Take care

Mark

The mainsail tack may not be lower than the top of the lower limit mark. The gooseneck position is not specified, and you may relocate it lower.

John

Many thanks John for this it will allow me to get the mainsail as low as is legal. Out of interest do you know how a deck limit mark is defined in terms of position? Is it just the lowest point of the deck beside the mast? 

Take care

Mark 

The class rules just say

D.1.5 DECK LIMIT MARK The deck limit mark shall be displayed on the centre plane of the hull near to the mast position. It shall be a minimum of 5 mm in diameter.
 

Yes, as low as possible yet near the mast and on a section of deck large enough for 5mm mark.

John

This is my view, not a definitive statement:

Section C.6.3 serves two purposes.  1) It defines the maximum luff length of a mainsail and 2) it defines the foretriangle height as a proportion of the mast height   The gooseneck height is not limited so the higher the gooseneck, the higher the foretriangle can be.

If you take the simple case of a flat deck and a triangular sail  with the tack just above the gooseneck,(which was possibly the only thing the original rules considered) then the deck limit is the point where the mast intersects the deck, the lower limit is just above the gooseneck and the upper limit is the top of the mast.  The height of the foretriangle is then calculated from these dimensions.  All very straightforward,

If we now consider raised foredecks and mast wells, things get a bit more complicated.  The following picture is actually a 10R but illustrates the issues

Where does the deck limit mark go?  On the lowest point of exposed mast, at the intersection of the flat portion of the deck and the mast, or at the highest point at which the mast is supported?  The rules only say that the position must be marked on the deck so, in my view, either the foredeck or the mast well could be used.  

If you assume that a higher foretriangle is an advantage (probably true) then using the deck well is the obvious choice.  If it is an advantage then making the deck well even lower (at least round the mast) becomes an option.  In my view the rule should be clarified and the deck limit should be defined as the lowest point on the mast which is not supported by the hull structure.  This would prevent extreme designs from gaining an advantage and is probably closer to the original intent of the rule.

Currently there is no maximum gooseneck height - does anyone fancy a 3 metre high mast with the gooseneck 1 metre above the deck for those windless days inland?  You could also have the clews significantly lower than the tacks as this gives you some free extra area thanks to way M sails are measured.

 

Thank you John, I think its interesting that we understand the point of the deck limit mark and its use fully, but dont seem to have a defined rule as to its position. Maybe its my assumption but the change in design from flat decks to stepped decks with wells and now it seems raised rear decks has all been to get the mainsail to deck distance smaller. This has led to complicated deck designs and access to the inside seems to be keyhole surgery. I wonder how many people now sail with boats that were built on the kitchen table. Mine was a simple fibreglass hull with a flat wooden deck. This was cheap to build and manufacture. Will it win every race, certainly not, but there is no doubt I make more mistakes that lose me a race than my boat design does. My challenge has been to get the most out of a 28 year old flat deck design and in that process learn as much as I can. When I started I was last to the first mark on every race. Now I am beginning to get to the mark in the middle or towards the front of the fleet and sometimes I even keep up to the finish I am now asking these questions as I am updating all the rigs from the 28 year old sails and masts I am currently using and am looking at the best way to lower the mainsail within the current rules. As John Ball said there is no rule that does not allow a portion of the gooseneck below the deck limit mark and  I will go with that as it is the simplest way for me to get the mast lower limit to 60mm.

But if you could lower the deck limit with just a small well  could a flat deck boat be built on a modern hull design, that was simpler and cheaper to manufactuer, and yet still be competitive?

Take care

Mark

Please remember the overall philosophy:

"The class rules for the International One Metre Class are closed class rules in which anything not specifically permitted by the class rules is prohibited. Individual rules may require, limit, or permit as necessary."

A direct quote from the IOM Class rules...

Thank you John, I think its interesting that we understand the point of the deck limit mark and its use fully, but dont seem to have a defined rule as to its position. Maybe its my assumption but the change in design from flat decks to stepped decks with wells and now it seems raised rear decks has all been to get the mainsail to deck distance smaller. This has led to complicated deck designs and access to the inside seems to be keyhole surgery. I wonder how many people now sail with boats that were built on the kitchen table. Mine was a simple fibreglass hull with a flat wooden deck. This was cheap to build and manufacture. Will it win every race, certainly not, but there is no doubt I make more mistakes that lose me a race than my boat design does. My challenge has been to get the most out of a 28 year old flat deck design and in that process learn as much as I can. When I started I was last to the first mark on every race. Now I am beginning to get to the mark in the middle or towards the front of the fleet and sometimes I even keep up to the finish I am now asking these questions as I am updating all the rigs from the 28 year old sails and masts I am currently using and am looking at the best way to lower the mainsail within the current rules. As John Ball said there is no rule that does not allow a portion of the gooseneck below the deck limit mark and  I will go with that as it is the simplest way for me to get the mast lower limit to 60mm.

But if you could lower the deck limit with just a small well  could a flat deck boat be built on a modern hull design, that was simpler and cheaper to manufactuer, and yet still be competitive?

Take care

Mark

51 minutes ago, Guzzilazz said:

Please remember the overall philosophy:

"The class rules for the International One Metre Class are closed class rules in which anything not specifically permitted by the class rules is prohibited. Individual rules may require, limit, or permit as necessary."

A direct quote from the IOM Class rules...

So I am playing devils advocate here, how does a small well beside the mast differ to a larger well behind a stepped foredeck. One is just a flattened and smaller version of the other. In the rules is one prohibited and the other permitted. Dont get me wrong, I think what I am proposing is not within the spirit of the rules, and certainly not what I intend to implement on my boat, but I have found in sports I have been involved with in the past, any loophole or undefined limit is often used if people believe it could gain an advantage.

Take care

Mark

As a measurer, I'm not going to comment on the Class Rules.  There is a process for the amending of them, and if you look back through this section of the forum, you will find the UK association asked for votes on the proposed changes for this year international AGM. 

 

Apologies Larry,  no intention to put you on the spot in your position. 

Take care

Mark

No problem, I didn't take it that way... IOM Class Management is very political at the international level from what I have been told.