Seat Back measurement Interpretation needed?

Dear All,

In this question first of all I need to point out the insignificance of this rule. It does not influence any of the boat’s performances, it is only an aesthetic option.

If I were to decide, I would delete A/13 completely from the specifications and let everybody use their imagination and skills to fulfill their creative ambitions and as it fits to serve their artistic thinking.

It is the only part of the DN that can give any personality to it and distinguish the different design styles.

In my interpretation, the current rule A/13 is a minimum area that can be placed anywhere on the backseat’s centerline. If the backseat is larger than the minimum, the above the deck area can be considered the backseat support that has no dimensions specified.

My interpretation of the current rule is:

If the backseat’s flat area at any point on the centerline is larger than 11″ in length 4″ in width and covers radius 2″ on the top side until the minimum length, it fulfills the rule A/13.

The intention of the rule is not very clear, some say it was a safety issue, some say it has something to do with hiking at the back when very hard masts were common.

I hope in reality we are not overthinking this issue.

In Jeff’s list, point 4 has a problem by overruling the specifications, where there is no mention of the rear deck level. It would require a ballot to change the specifications.

Thanks!

I think the real question mark is related to 2” radius and where is has to be met. My opinion is that the rule makes it clear: “the crown on top of seat must be a minimum of 2’’(50.8 mm) radius”. There is only one top of the crown and it doesn’t matter if seat back is 11” or more. Top is top. There is no word about area.
Therefore I believe below (attached) drawing represents my take on A.13.
Green = compliant
Red = illegal
http://http://serwer1376810.home.pl/P55_Images/backseat.jpg

the discussion about how it influences boat performance and is non relevant for this case.

I agree to 1-4 mentioned by Jeff.

There are a couple of questions in my mind:

1. How does any attached extension to the backseat influence the flatness and size of the backseat in measuring? Like the commonly used sponge kind of plastic attached to the headrest part to hold the helmet during sailing? Is that allowed?

2. How would you distinguish between the backseat and the headrest support?

Thanks!

Peter

Hi All,

I agree with Richard and Paul. If the top needs to be a 2″ radius, then any lesser value shouldn’t be acceptable on any part of the edge line of the headrest.

I am still saying that it is not a crucial issue. And I would allow any form or shape.

I dont see any safety problems with the headrest regarding the top radius, as there are many much sharper edges around your head, like the boom, the side panels top, the tiller, and so on. Why they do not make any concerns about safety? Why the thickness of the backseat (or the lack of it) is not an issue here if we talk about safety?

The padding on the headrest provides hold for the skipper’s helmet and head and helps the neck not to be tired too soon. That is a functionality that gives an advantage in sailing. Noone uses it for additional safety.

We are talking about some aesthetic issues that in reality not worth the e-paper, but not questioning something that has an absolute advantage over the others, besides overwrites the allowed parameters in the rules…

I still have 2 questions, which could be important not to be overlooked and to define in this discussion:

1. I still dont know what separates the headrest from the support? This could be answered.

2. If I glue anything to the hull or any part of the DN, is it outside of the measurement dimensions?

Thanks,

Peter

Tomek

It has been my continuing opinion to A.13, that it applies to portion at centerline “crown” what happens outside the 2″ radius is beyond the controlled area

therefore I would believe there is no issue with Vaiko’s approach.

jk

at 6:35 pm
Edit
Richard LarssonRichard Larsson
I agree with Paul. We should decide if the green line in Peters picture is a minimum surface that could be bigger outside the line and be shaped free, or if the upper edge of the flat surface should be at least a 2″ curved radius.
As Jeff pointed out above we only talk about the flat surface. That makes some complicated effects. If Vaiko would provide a sticker 0.1mm thick shaped as the green line all his hulls would be clear. The surface behind the sticker would be a support for the sticker and the sticker would be defined as back seat. This is not cool, or maybe it is?
Peter, now i realize the problem with this. It is way harder to handle than I thought.
My adviser board helped me to clear up this problem. We discussed how a back seat should be defined. We think it could be ¼” thick from the surface that has to be flat. The back seat is allowed to be faired with a ¼” radius as the corners of the hull are. We measure the sides of the hull as if they were not faired. Let’s measure the back seat in the same way. The “green line” (the measurement of the rule) then will be measured in the widest spot of the upper part and sides of the back seat not further back/down than ¼” perpendicular to the flat surface. The measured edge of the back seat shall, all the way, have a convex curve of minimum 2” radius. Less radius along the upper edge of the back seat are not allowed. (Sorry Vaiko, I gladly interpret this somehow so the 10mm radius is ok. Please make another interpretation, maybe I will support it. Otherwise it is very easy to correct the back seat).

We also want to interpret the support of the back seat. This is our suggestion. The support of the back seat is defined as the material above the deck and behind the back seat of ¼” thickness. The support cannot be higher from the deck, or wider, than the back seat. The support cannot stretch further back than 1/3 of the length of the deck.