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prod bobstay tube through the bow


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So couple years ago I recall reading a post about this. I think wild thing had some really good ideas. any one know how to find the old post or any one got the juice on how to do it?

 

I plan to put a carbon tube right through from one side to the other. I can access the inside easy so obviously taping it in will be easy and it will but up to the back of the stem/bow.

 

But how should i finish the outside of the hole. i was going to router a radius on the tube/ hole then try to tie it on with splayed out uni's that travel right through from one side to the other and put a cover patch over that and then when its set file, sand it up nice.

 

thoughts please?

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This might be of help but unfortunatey the pictures are missing - FNG can you help

 

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Best way to rig a prod...?

 

 

Apparition

PostPosted: Mon Jan 19, 2009 11:03 am Post subject: Best way to rig a prod...? Reply with quote

 

Apparition is going to get a gennaker (or two) soon.... this will of course necessitate adding a prod to the pointy end. Since these forums are full of budding hot-rodders I figured you lot could give me your thoughts on the best way to rig up a prod and any suggestion on who could design/fabricate/install it. (DIY is a possibility too).

 

Apparition is a Ross 35 that does more cruising than racing so the prod will either need to be easily removed or allow for easy access to the anchor well and the anchor roller. A 2m prod will allow for 100m2 (ish) fractional genni which might be a bit on the large side so I may go shorter and less area to make it easy to manage 2-handed. Actual length of the prod will be influenced by the complexity of the rigging required to support it.

 

Any thoughts, theories, designs, pictures welcome....

 

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fng

PostPosted: Mon Jan 19, 2009 6:22 pm Post subject: Reply with quote

 

somthing like this in alloy is the most cost effective

 

spy carbon prod 009.jpg

 

 

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fng

PostPosted: Mon Jan 19, 2009 6:24 pm Post subject: Reply with quote

 

hull mounts

 

spy carbon prod 001.jpg

 

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fng

PostPosted: Mon Jan 19, 2009 6:24 pm Post subject: Reply with quote

 

stem

 

spy carbon prod 002.jpg

 

 

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fng

PostPosted: Mon Jan 19, 2009 6:26 pm Post subject: Reply with quote

 

tack

 

spy carbon prod 003.jpg

 

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fng

PostPosted: Mon Jan 19, 2009 6:27 pm Post subject: Reply with quote

 

or you can go on deck or through the hull

 

C12 prod 005.jpg

 

 

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Apparition

PostPosted: Mon Jan 19, 2009 7:27 pm Post subject: Reply with quote

 

Hmmmm.... looks sexy in carbon Smile I like that idea since it avoids the requirement for the side stays. Looks like I wouldn't have to do anything with the anchor roller either. You reckon you could get that out to 1.2-1.5m without too much drama? What would it cost to put one together... ?

 

Through the hull is nice but I hear its pretty hard to keep the water out...?

 

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wal

PostPosted: Tue Jan 20, 2009 6:24 am Post subject: Reply with quote

 

'course you can alway incorporate the anchor roller into the prod to keep the anchor away from scratching the yot

_________________

Wal'

 

021 226 1196

 

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fng

PostPosted: Tue Jan 20, 2009 7:34 am Post subject: Reply with quote

If you have an anchor well the through hull option is easily sealed when the prod is extened. All you need is an inspection port where the prod goes through the anhor well bulkhead.

 

give me a call if you want to discuss any of this, or for the alloy contacts

Gary 021734298

leading edge boatbuilders

 

 

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Hi Skins, before I sugest laminates etc what size boat.

 

Typically I would layup a glass patch inside the bow where you want the hole about 150mm high and about 100mm onto each side of the hull, this would be similar to the hull inside skin laminate at the bow, and be staggerd.

I usually glue two tubes together to get enough wall thickness to allow a sanded radius for the bobstay.

Glue it in and glass over it again.

you could glue in a block and glass over that instead, wood on a smaller boat or solid glass on a larger.

post-234-14188717268.jpg

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Skinner if you are thinking of using Dynex for the stay I would reallt suggest going to a rod one as we started off with a Dynex one on the karma it just stretches to much changed to rod it is still lashed on at the bottom but its way better.

 

Cheers

 

Gappy

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Yeah agree on the rod - Gary P (I think) put a prod on the Spy and we had a Dynex bobstay (or similar)

 

We wound up putting the downhaul on it and winching it to deal with the creep. Prod was flexing a lot till we did that.

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Doesn't sound like Dynex or any other good dyneema was being used on either boat or if it was who undersized it?

 

No way a good dyneema should move enough to be a concern, if at all even noticeable.

 

It is being used very successfully by many boats.

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Possibly not pre-stretched KM but we have run numerous prods with Dyneema including my own right now. Never had a problem unless the prob is very long or the downhaul angle very shallow. Unless people are running big tight luffed sails but that is a different story.

 

Pretty sure Truxton already had a Dynex bobstay so its worked before?

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Chain-hoist between Camaro and Volvo is my patent pre-stretching device. Simple and works a treat.

 

Most of the creep would be in the splices rather than the Dynex? KM?

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All depends on whether it is dynex or another dyneema (Dynex is only a brand name knot a product in it's own right) and then what grade and then whether it's heat-set or knot, as to how much stretch, creep and other stuff will happen. You can easily get dyneema in 3 differing grades in NZ (Dynex branded have only 2, they are a bit old school now) and they will work quite differently when talking elongation. Saying just 'dynex' or 'dyneema' is like saying 'boat', there are many variations.

 

Yeap the splice/s will need compacting usually and if it's knot heat-set there could be a little left in the lay that could be taken out. Best to splice to roughly the right length but leave a tail out of one splice. Load the bugger up to around 50% of break load and hold for a while, overnite is good, longer won't hurt it, 15mins is a tad short. Once done tweak splice to length, fit to boat, load cold beers, go yachting. DO NOT load it to listed break load less 100kg, many listed break loads are knot achievable outside of the rope factory laboratory so you are likely to hurt yourself or something.

 

That is also the guts of the heat-set versions except they also apply heat which speeds things up and they cyclic load it a few times, which does increase it's strength a little. But for those who would like to apply heat at home, do it carefully as at 155 degrees odd dyneema starts turning bad and won't come back well.

 

Dynex Dux, Donaghys Ocean 12HS and Armare RoundlineHS are all heat set versions and available in NZ, as are their non-heat-set cuzzies. But heat-set doesn't like bending around blocks a lot, the heat-setting reduces it's flex fatigue resistance dramatically, which is why many big names don't heat-set theirs including Samson who use 50% of the world dyneema that is used in ropes. Great for straight lines though and was originally designed for fishing trawlers.

 

In NZ there is one manufacturer who uses lots of SK62, where everyone else has move on to SK75 and a few into SK90. The 2 bigger NZ rope names both use 75 and/or 90 depending on your wallet. Said same 3rd manufacturer I suspect has dumped the real McCoy and is now using Chineema i.e. a chinese knock-off. Got some, played with it, OK for low loads but very wobbly in break loads and always well below the real stuff.

 

Hence saying the Dynex stretches would tend to indicate one of 3 things. One being it isn't Dynex or one of the other ones like it or 2 it's a lower grade which is possible in NZ with many places knot knowing what they are actually selling or 3, someone just picked a size too small. I'm excluding the obvious, someone just made them too long ;)

 

Dynex is the best known as Hapmie dived into it big time with the North Sea fishing fleet and they have pretty damn good marketing so it didn't take long before the name became very commonly known. So a bit like Gladwrap (only a brand name) Dynex also became the product name. But Dynex and Dynex Dux are only 2 brand names for stuff many many others make from exactly the same material. The sad bit is Hampie did really carry on with it's work so is now behind most others but then again they sell shite loads into the fishing fleet so many they are just sticking to their knitting as they say.

 

But the comments about stretching don't really stack up if it was done right with the right gear. We have made some bits that are doing the same job on a couple of boats that would load the bobby way more then the 2 boats mentioned above. All are working perfectly fine. Yes we did pre-stretch then just to make sure measurements stayed where they were supposed to.

 

EE, knot creep just stretch. Creep or 'cold flow' using it's technical name is something else yet again. But with the bobbies in mind if it is creep causing the issue that would be a very good indication they just used a crap product. Average creep to be expected in a good dyneema line if loaded relatively highly, which would also be well above the manufacturers recommendations and most regulatory requirements, would be around 1.5 to 2% so in a 2mt bobstay only 40mm max. and it sounds as if the boats were seeing a lot more than that.

 

Oh and there are some outfits selling dyneema winch ropes that are really only polyprop. Had a boat get cunning and save a fortune by buying a pile of winch ropes for his boat. Most busted 1st use. Hello, you never thought why there was such a massive price difference ya dick!

 

We are supply a few sailmakers lots of dyneema for big A sails usually so making sure your bobbie is up to speed and can cope is getting a lot more important.

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