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Old 18-09-2008, 22:11   #1
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Spinnaker Prodder

The cat I am building has a prodder mounted to the front beam for carrying the spinnaker and screecher. It is close to 2.0m in length and constructed to hinge upwards to reduce the overall length of the boat when in a marina. The design calls for a composite construction including the tangs that connect to the hulls and for connection of the two sails. I am not happy with the concept and know others have had problems with the arrangement including the designer who has modified the design several times.
I am looking at changing the design and building the prodder out of an aluminium section but would be interested to hear from other cat owners on how their prodder is connected to the front beam and hulls. On my last cat (27 foot Simpson Backslash) I built an aluminium prodder and ended up breaking it twice where it joined the front beam, but I must admit some of the problem was more related to how we were racing the boat at the time and the loads exerted.
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Old 19-09-2008, 02:24   #2
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I went through around 5 versions before getting it right. I ended up using an 80 mm diameter carbon fibre tube with a 2-3 mm wall. The end fittings are in 316 stainless, and are just riveted on.

The forces working on the forebeam are enormous, so I reinforced the beam on the aft side with an "horisontal dolphin striker" Stays are 10 mm 19 strand wire, after playing around with different folding systems, these are now fixed length.

My prodder is about 1 metre.

I can post pics if that helps.

Regards

Alan
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Old 19-09-2008, 03:11   #3
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Selden Bow sprits

I was talking yesterday at the Southampton Boat Show about the exact same thing, Selden do a retractable gennaker bow sprit in either Aluminium or Carbon Fibre.
They look absolutely perfect ie 3 metres long etc.
I have scanned in the relative prices and at the bottom of the page their website address.
Hope this helps.

If you cant read the address it is www.seldenmast.com
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Old 19-09-2008, 05:11   #4
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I'd say an alloy tube section with thick enough walls should be pretty much bulletproof, although the Spirited has a composite forebeam, so it's likely preferable that the prodder breaks easier than the attachment points.

Instead of hinging upward, have you though about hinging it sideways? Some friends have their prodder set up this way, and it allows more versatility from their sails.

For running deep they can move the tack of the sail to windward, and for close reaching they move the tack to leeward. I've seen it in action and it works really well, I intend to copy it.

And it still allows you to shorten the boat.

How long have you been building? How far have you got with the boat? Any photo's? Maybe one day I can drop in for a look?
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Old 19-09-2008, 05:14   #5
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44C,
How have they set up the waterstays with this setup? I'd love to see a picture if possible..

thanks

Alan
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Old 19-09-2008, 05:22   #6
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They go through a block under the end of the prodder, sort of like a bridle. I meant to take some photo's before, and now they are off cruising North Queensland for a few months. When they get back I will.
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Old 19-09-2008, 06:02   #7
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Thanks,

Always nice to see how others sort things out...

Alan
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Old 19-09-2008, 10:37   #8
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44',

I'm picturing a single block at the end of the prodder with a continuous, non-adjustable spectra/dyneema waterstay running though it. Adjsutments would be made with the sidestays. Or are the waterstays themselves adjustable with control lines?
Sounds like having the adjustability is worth a couple more strings to pull.

Mike
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Old 19-09-2008, 12:54   #9
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My prodder attaches behind the trampoline to a spinnaker pole bayonet on a universal joint; it stands over the forward crossbeam and is held up by screecher halyard tension. While I am currently using fixed waterstays (whiskerstays) which mean a fixed position for my screecher tack, I am considering bringing the whisker stays back inside the prodder to allow me to shift the tack laterally. I will need a small winch to do do so and maintain halyard tension. A present fear is that the proximity of the furled screecher is fouling the airflow on the genoa, The boat points a bit higher when the screecher is down. It may improve tacking the screecher, a royal PITA.
My prodder is a 3" carbon shaft, 9 feet long. The whole assembly can be pulled in to reduce my LOA 3 feet, by slacking the halyard and releasing the bayonet. Pole, furler, lines and mount weigh 26 pounds. The sail weighs 64 pounds.
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Old 19-09-2008, 12:55   #10
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I tried the 2 adjustable waterstay setup, using standard Lewmar 3" blocks. these were deformed after an outing in 15 knots TWS using the Code 0, so I went back to fixed SS stays.

I didn't want to invest 3 x 200$ in fancy high load blocks, when 2 of them would be under water most of the time when sailing

The 12 mm Dyneema I used was totally stiff, so I had to throw it out. A gennaker would probably be a lower load, as it isn't used as close to the wind as the Code 0.

The angle between the prodder and the waterstay fixture points (seen in a fore/aft plane) will have a large influence on the size of the force as well IMO.

Alan
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Old 19-09-2008, 13:09   #11
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Quote:
Originally Posted by sandy daugherty View Post
My prodder attaches behind the trampoline to a spinnaker pole bayonet on a universal joint; it stands over the forward crossbeam and is held up by screecher halyard tension. While I am currently using fixed waterstays (whiskerstays) which mean a fixed position for my screecher tack, I am considering bringing the whisker stays back inside the prodder to allow me to shift the tack laterally. I will need a small winch to do do so and maintain halyard tension. A present fear is that the proximity of the furled screecher is fouling the airflow on the genoa, The boat points a bit higher when the screecher is down. It may improve tacking the screecher, a royal PITA.
My prodder is a 3" carbon shaft, 9 feet long. The whole assembly can be pulled in to reduce my LOA 3 feet, by slacking the halyard and releasing the bayonet. Pole, furler, lines and mount weigh 26 pounds. The sail weighs 64 pounds.
I once saw a picture of a boat with a setup a bit like yours Sandy, they had put a traveller track under the forebeam, and had a kind of "dolphin striker" on the prodder itself AFAIR. For a 3 ft extension it would probably work well, for a 6 ft/2 meter extension, I doubt that it would be enough unless the dolphin striker is really long.
A couple of lines for traveller control and you could do it from the safety of your cockpit.

I never use the jib with the Code 0 furled up, way too turbulence, but moving it to leeward sounds like a neat way of solving the problem.

Alan
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Old 19-09-2008, 13:57   #12
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Quote:
Originally Posted by mikereed100 View Post
44',

I'm picturing a single block at the end of the prodder with a continuous, non-adjustable spectra/dyneema waterstay running though it. Adjsutments would be made with the sidestays.

Mike
I'm pretty sure this is how he has done it. But I haven't really checked it out thoroughly yet.

I don't think the waterstays were adjustable, so when the prodder is swung to the side it would also tend to lift a little.
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Old 21-09-2008, 17:11   #13
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Thanks for the replys.
Nordic Cat - I would like to see some photos of your arrangement if possible.

44c - My preference was to swing the pole sideways as well, it saves trying to connect sails to a prodder that is 2.0m in the air. I had looked at one fixed kicker (waterstay) and one on a block and tackle that could be released to swing the pole to one side, but with two blocks it could go both ways which would improve downwind cruising.

The prodder will need to be self supporting to allow changing from a screecher to a spinnaker, i.e. drop the furled screecher on the deck and raise the spinnaker, this is how I did it on my last cat.

44c - I started construction 12 months ago, after work and weekends, and am well into the internal fit out and hope to start installation of engines in the next couple of weeks. I would be happy to show you progress and likewise would like to catch up with your project.
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Old 21-09-2008, 18:36   #14
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Originally Posted by spiritcat View Post
Thanks for the replys.
Nordic Cat - I would like to see some photos of your arrangement if possible.

44c - My preference was to swing the pole sideways as well, it saves trying to connect sails to a prodder that is 2.0m in the air. I had looked at one fixed kicker (waterstay) and one on a block and tackle that could be released to swing the pole to one side, but with two blocks it could go both ways which would improve downwind cruising.

The prodder will need to be self supporting to allow changing from a screecher to a spinnaker, i.e. drop the furled screecher on the deck and raise the spinnaker, this is how I did it on my last cat.

44c - I started construction 12 months ago, after work and weekends, and am well into the internal fit out and hope to start installation of engines in the next couple of weeks. I would be happy to show you progress and likewise would like to catch up with your project.
You can just run a permanent line from the striker to the prodder to hold it up when the halyard is off. You wouldn't sail all day like this, but it's OK for sail changing.

A friend who has a fixed prodder has his tack shackle on a short line through a block on the end of the prodder, so he can affix the tack from on the catwalk. He just hauls the tack back out and cleats it off. That could be another solution to the 2 metres up problem.
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Old 21-09-2008, 19:30   #15
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44c

I had both of these arrangements on my previous cat, prodder supported by the a line from the striker and the spinnaker tack through a block at the end of the prodder.

One of the problems I found was that the stricker is not designed to take loads for and aft but laterally across the beam, and as a result it damaged the connection to the beam. One alternative which I believe was mentioned in one of the responses was to have the prodder self supporting form a diamond strut running along the prodder to the hinge connection.

If you CarbonKopy from Hervey Bay, it had a self supporting prodder to carry its spinnaker - although it was a full on race boat.
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