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Old 01-03-2008, 07:57   #1
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New purpose built compression beam installed

We have desigend and had extruded a purpose build compression beam for Our FastCats and will also make this available to other boat builders
The beam is 220 mm wide or 9 inches , has 2 track build in , is slightly curved on top and has a V on the bottom to break waves .
I have attached some pictures of the first one installed on the New FastCat 455 , the weight ( very important for us ) is 5.1 kilo per meter or 3.4 Lbs per foot or less than half the weight of the previously installed Boom Profile.
Greetings
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Old 01-03-2008, 10:23   #2
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Gideon,
Can I ask what may be a dumb question?..and it relates to what I see here. If a track was placed on the horizontal strut running port-starboard and the tack of an asymetrical was attached to a car, and ran to port for being on a port tack...would there be an advantage to getting the tack upwind for broad reaches? The track would have to be behind the forestay in order gybe the asymetrical. This is opposed to using a spinnaker pole with a typical spinnaker which would of course be faster but more difficult for someone with a limited crew.

On a 50 foot boat with a typical 25 foot beam, this would mean the tack would be roughly 12 feet to port from centerline on a port tack which would mean 12 more feet of exposure to the wind....see what I mean?

Basically what you would have is a traveler for the tack of the asymetrical so you can place the tack further forward and to weather giving it more exposure to the wind.

Another advantage is that you could run the tack down to leeward if you feel you are being a bit overpowered by your asymetrical....(provided this works in the first place.)

Would it make any sense to do this?

My second question is I see some stainless steel bolts attached to some aluminum castings. Are there any potential corrosion problems by doing this?

David
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Old 01-03-2008, 13:12   #3
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Quote:
Originally Posted by David M View Post
Gideon,
Can I ask what may be a dumb question?..and it relates to what I see here. If a track was placed on the horizontal strut running port-starboard and the tack of an asymetrical was attached to a car, and ran to port for being on a port tack...would there be an advantage to getting the tack upwind for broad reaches? The track would have to be behind the forestay in order gybe the asymetrical. This is opposed to using a spinnaker pole with a typical spinnaker which would of course be faster but more difficult for someone with a limited crew.

On a 50 foot boat with a typical 25 foot beam, this would mean the tack would be roughly 12 feet to port from centerline on a port tack which would mean 12 more feet of exposure to the wind....see what I mean?

Basically what you would have is a traveler for the tack of the asymetrical so you can place the tack further forward and to weather giving it more exposure to the wind.

Another advantage is that you could run the tack down to leeward if you feel you are being a bit overpowered by your asymetrical....(provided this works in the first place.)

Would it make any sense to do this?

My second question is I see some stainless steel bolts attached to some aluminum castings. Are there any potential corrosion problems by doing this?

David
Hello David

I think I understand what you are saying , we work it in a diffrent way , we have a removable bowsprit with a lenght of 7 feet to take the gennaker further forward and away from the mast and main sail to get more wind into it. What you are suggesting would also have advantages but you would not get the gennaker further forward just more to the windward side, We have worked on a movable bowsprit but the waterstays give a problem and our way of thinking is always , keep it simple otherwise it will break and is not reparable while out at sea.
The stainless bolts that you have correctly seen are in Vesconite sleeves and do not make direct contact with the aluminium.so there will not be any corrosion.This is off course the first reason to do this , the second is noise, metal on metal is always noisy so we try to prevent this wherever possible because a silent boat is also a comfortable boat.


Greetings

Gideon
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Old 02-03-2008, 01:29   #4
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Here is the drawing of the new compression beam attached
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File Type: pdf compressie beam 435.pdf (43.7 KB, 96 views)
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Old 03-03-2008, 00:27   #5
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Quote:
Originally Posted by David M View Post
Gideon,
Can I ask what may be a dumb question?..and it relates to what I see here. If a track was placed on the horizontal strut running port-starboard and the tack of an asymetrical was attached to a car, and ran to port for being on a port tack...would there be an advantage to getting the tack upwind for broad reaches? The track would have to be behind the forestay in order gybe the asymetrical. This is opposed to using a spinnaker pole with a typical spinnaker which would of course be faster but more difficult for someone with a limited crew.

On a 50 foot boat with a typical 25 foot beam, this would mean the tack would be roughly 12 feet to port from centerline on a port tack which would mean 12 more feet of exposure to the wind....see what I mean?

Basically what you would have is a traveler for the tack of the asymetrical so you can place the tack further forward and to weather giving it more exposure to the wind.

Another advantage is that you could run the tack down to leeward if you feel you are being a bit overpowered by your asymetrical....(provided this works in the first place.)

Would it make any sense to do this?


David
My current plan is to mount the prodder so it pivots horizontally, using a spectra bridle through a block, so I can move the tack of the screecher or spinnaker to windward or leeward as required. I think this would achieve what you are aiming for, in a simpler and more easily operated way.
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Old 03-03-2008, 02:21   #6
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Quote:
Originally Posted by 44'cruisingcat View Post
My current plan is to mount the prodder so it pivots horizontally, using a spectra bridle through a block, so I can move the tack of the screecher or spinnaker to windward or leeward as required. I think this would achieve what you are aiming for, in a simpler and more easily operated way.
This bridle set-up is the easiest and best way to go. You have to keep everything flexible, as the forces are so big, that even 12mm Dyneema stretches so that it becomes like a rod! That is my experience on a 35 ft/4.5 ton cat with a 70m2 Code O. With lighter sails like the gennaker, the forces will probably be lower, as I carry my Code O in 25 knots at 50 degrees relative, sometimes higher.

I found that fixing the prodder in one position, and pulling the sail tack to either bow is a better and easier solution than the movable prodder when using sails that don't furl.

I have gone back to wire waterstays, with shackles, as i damaged som 3" blocks (standard ones, not hi load)

I made an "horisontal seagull striker" to fit under the tramp, but behind the crossbeam to handle the forces there, as an alternative to using a compression beam like Gideon has made.

Hope this helps

regards

Alan
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