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#263250 - 09/05/13 06:32 PM Front Beam  
Joined: Feb 2005
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Karl_Brogger Offline
Carpal Tunnel
Karl_Brogger  Offline
Carpal Tunnel

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Northfield Mn
Do we need a dolphin striker?


I'm boatless.
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#263255 - 09/06/13 01:21 AM Re: Front Beam [Re: Karl_Brogger]  

**DONOTDELETE**
Unregistered
Scarecrow
Unregistered


On a Viper with Ali beams? Yes

Alternately there is only one way to find out for sure....

#263260 - 09/06/13 06:54 AM Re: Front Beam [Re: Karl_Brogger]  
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Karl_Brogger Offline
Carpal Tunnel
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Northfield Mn
I mean rules wise. Is it required?


I'm boatless.
#263262 - 09/06/13 07:10 AM Re: Front Beam [Re: Karl_Brogger]  
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Rolf_Nilsen Offline
Rolf_Nilsen  Offline


Carpal Tunnel

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West coast of Norway
From the top of my head: A dolphin striker is not required in the rules.

Materials in the beams are not restricted either.


Class rules are missing on the class website so it is impossible to check if there have been any changes on this over time.

Last edited by Rolf_Nilsen; 09/06/13 07:16 AM.
#263263 - 09/06/13 07:16 AM Re: Front Beam [Re: Karl_Brogger]  
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Karl_Brogger Offline
Carpal Tunnel
Karl_Brogger  Offline
Carpal Tunnel

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Northfield Mn
I didn't think so, or at least I didn't remember seeing anything about it. I knew materials weren't limited. A carbon front beam could be designed to not have a dolphin striker, whether or not there is a savings in weight I don't know. It could certainly be stiffer.


I'm boatless.
#263265 - 09/06/13 07:23 AM Re: Front Beam [Re: Karl_Brogger]  
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Rolf_Nilsen Offline
Rolf_Nilsen  Offline


Carpal Tunnel

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West coast of Norway
No dolphin striker to hit waves is faster.

I dont know what happened to the rules in 2010 as the ISAFisation process was going on.. Look at this for the rudders in a PDF of the 2010 rules I found on the forum on the class website.

Quote

E.4.4 CONSTRUCTION
(a) The cross section of each rudder shall be symmetrical about its fore and
aft centre line .



Now what does this mean?? Rudder winglets certainly is allowed in multiplie configuration and is used in the class but this effectively does not allow L-shaped winglets. No discussion, no ballot and comments..

#263274 - 09/06/13 09:00 AM Re: Front Beam [Re: Rolf_Nilsen]  
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Posts: 141
mini Offline
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mini  Offline
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Originally Posted by Rolf_Nilsen
No dolphin striker to hit waves is faster.

I dont know what happened to the rules in 2010 as the ISAFisation process was going on.. Look at this for the rudders in a PDF of the 2010 rules I found on the forum on the class website.

Quote

E.4.4 CONSTRUCTION
(a) The cross section of each rudder shall be symmetrical about its fore and
aft centre line .



Now what does this mean?? Rudder winglets certainly is allowed in multiplie configuration and is used in the class but this effectively does not allow L-shaped winglets. No discussion, no ballot and comments..


T foil rudders are specifically mentioned as allowed. No varying shape is allowed on the dagger although they could be assym as long as they are straight and canted no more than 6 degrees. You could easily argue that a J or L foil on the rudder would be likewise allowed.
What is not mentioned is moving flaps or likewise appendages. By the rules you could add them on the rudders now and vertical flaps to the daggers too if you wanted to. - That ought to bring forth a big rules debate as soon as somebody shows up to a worlds sporting moveable flaps.

#263276 - 09/06/13 09:52 AM Re: Front Beam [Re: Karl_Brogger]  
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pgp Offline
Carpal Tunnel
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Does anyone have a link to the current rules set?

Was there a class meeting at Racine?


Pete Pollard
Blade 702

'When you have a lot of things to do, it's best to get your nap out of the way first.

#263277 - 09/06/13 09:52 AM Re: Front Beam [Re: Karl_Brogger]  
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Rolf_Nilsen Offline
Rolf_Nilsen  Offline


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Posts: 4,451
West coast of Norway
Which after this AC and little AC cycle is a total reality smile

#263278 - 09/06/13 09:56 AM Re: Front Beam [Re: Karl_Brogger]  
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pgp Offline
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I think the hulls as we have known them are going away and the boat will become a ladder frame to attach sponsons and foils.

I was unwilling pay the collectors price for the Bernard Smith book, but iirc he talks about fat foils which lead to limitless design possibilites.


Pete Pollard
Blade 702

'When you have a lot of things to do, it's best to get your nap out of the way first.

#263280 - 09/06/13 11:15 AM Re: Front Beam [Re: pgp]  
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Rolf_Nilsen Offline
Rolf_Nilsen  Offline


Carpal Tunnel

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West coast of Norway
Mirabaud already went that route. It is not fast when not foiling wink

#263282 - 09/06/13 11:21 AM Re: Front Beam [Re: mini]  
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samc99us Offline
old hand
samc99us  Offline
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Solomon's Island, MD
This might be a good thing for the class if it can be done well, and still be usable for single handing, and not add a lot of hassle to sailing off the beach. I for one would be pretty likely to switch to a full flying F16, as we're in the ball park weight range and have an existing local fleet. Trouble is the existing boats are not good in short chop on a distance course where waterline is king. Full flying changes all of that.


F18 Infusion
#263284 - 09/06/13 11:44 AM Re: Front Beam [Re: samc99us]  
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Rolf_Nilsen Offline
Rolf_Nilsen  Offline


Carpal Tunnel

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West coast of Norway
No foiling in the F16 class as the daggerboards can not go more than 6deg off vertical. This makes it hard to get enough surface producing vertical lift in the water.

Sensible approach in my opinion. It is still early days for foiling. What would be cool was if somebody starter testing foiling under the platform outside class racing.

#263289 - 09/06/13 02:19 PM Re: Front Beam [Re: Karl_Brogger]  
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waynemarlow Offline
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The early Stealths did not have a front Dolphin striker and had T Foils way back in 2001, very stiff boat reliant on an oversize extrusion designed for the Dart 18's. It was only when John couldn't source the beams any longer did he change to a conventional set up.

As to foiling, nah we are just too heavy, but a semi foiling mode maybe the answer. Interestingly the SCHRS handicap system will defeat most foiling boats ability to really shine. Type in your boats details and then try the same with the lifting boards tick box activated. Watch that handicap get real tough. It amounts to a penalty of about 20 kilos of ballast. Mmmm

#263291 - 09/06/13 02:39 PM Re: Front Beam [Re: Karl_Brogger]  
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Timbo Offline
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Timbo  Offline
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Sebring, Florida.
I would love to see some of the A Cat guys build an arched front beam with no dolphin striker. Are there any out there already?

It would have to be made of carbon of course, unless you're really good at custom bending alum. tubes.

I guess you could put on a huge oversized straight tube, either alum. or carbon, with a thick enough wall, it wouldn't need a striker for support, but it'd be heavier and more drag when you do hit the top of a wave with the beam.


Blade F16
#777
#263317 - 09/07/13 01:18 PM Re: Front Beam [Re: Karl_Brogger]  
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Rolf_Nilsen Offline
Rolf_Nilsen  Offline


Carpal Tunnel

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West coast of Norway
I have not seen arched front beams on A-cats. More surface area to contend with in the build.

The C-cats do have curved beams, but with dolphin strikers from what I remember.

Bending an alu tube of 80-100mm diam would not be possible I think without compromising the structural integrity.

#263408 - 09/09/13 07:37 AM Re: Front Beam [Re: Karl_Brogger]  
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samc99us Offline
old hand
samc99us  Offline
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Solomon's Island, MD
Hydro's has a dolphin striker (here: http://4.bp.blogspot.com/-plJNEqIu7...k3vAWmg0/s1600/cclasshydrosADimages1.jpg)

That doesn't mean the other boats do. The DNA does not have a dolphin striker, meaning you can probably do the same on a F16. That is the kicker with the F16 rules as currently written, as has long been discussed elsewhere.

Phantom built a foiling F18, but in carbon of course. Reading between the lines the existing hull shapes are fine but longer and wider is much better, as is having a second pair of hands to work the dagger boards. Time will tell.


F18 Infusion
#263418 - 09/09/13 11:33 AM Re: Front Beam [Re: samc99us]  
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mini Offline
member
mini  Offline
member

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Posts: 141
The early F18 used the beams from the 20 foot 10 foot wide Tornado because it was easy to source and that became the standard. Some of the builders are using this same oversized beam now on their F16. Both are overkill and it would be a simple calculation to see if they would be structurally capable of handling the loads without a striker.

If they could it would likely be a bit more flexy. I heard a rumor where Ashby installed a striker on his A class “stikerless beam” anyway because he thought the increased stiffness outweighed the added windage and weight.

The C class have a square truss system built into their designs. This requires the stiker post and its runners to each corner of the platform. They then can have a very light beam set as the truss system, which works off the striker and the standing rigg working together, provides all the structural stiffness at a significantly lower weight penalty than having big overbuilt beams. Looking at the AC45 and 72 they are doing the same thing it appears to me.

#263453 - 09/10/13 05:12 AM Re: Front Beam [Re: Karl_Brogger]  
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bacho Offline
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Greenville SC
I've been told a striker and beam on an A wieghs less than a striker less beam. A triangle is a fantastic way to add strength.

#263616 - 09/11/13 01:46 PM Re: Front Beam [Re: bacho]  
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mini Offline
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mini  Offline
member

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Posts: 141
Originally Posted by bacho
I've been told a striker and beam on an A wieghs less than a striker less beam. A triangle is a fantastic way to add strength.

Efficiently reaching your goal. You do not think the AC and C class guys would place those very complicated strut systems on their rides if is was not more efficent.(better)

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