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PostPosted: Mon Aug 27, 2012 3:06 pm 
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Joined: Thu Aug 23, 2012 1:53 pm
Posts: 6
For a long distance trip, would a stainless sprocket shaft (vs the standard sprocket shaft) be worth the extra cost? Are the the teeth on a standard sprocket shaft (the teeth for the chain) steel or plastic?


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PostPosted: Mon Aug 27, 2012 8:39 pm 
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Joined: Sat Nov 12, 2005 10:46 pm
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Location: Escondido
It sounds like you are referring to the sprocket, rather than the sprocket shaft (which is already stainless).

IMO the current ("V2") sprockets and masts are superior to stainless sprockets. Although stainless cogs are bullet-proof, the chain/cable can skip a link if not kept at the correct tension. The current glass-filled nylon cogs are almost impervious to that problem. The newer cogs are wider and there is a "master" cog that locks the chain in (discernible in the picture below).

Cog wear is not much of an issue. In the picture below one of these sprockets is new; the other has over 800 miles on it. Can you tell the difference? I couldn't either.
Image

Stainless sprockets use cotter pins to mount the masts (rods that support the fins). These is simple to replace, but are subject to sudden breakage over time because the masts wobble slightly back and forth in their slot. Present threaded masts will not wobble or back out if properly installed and should be reliable for over 1000 miles unless they've had multiple major bends.

Finally, if you have an unforeseen problem, current parts are more likely to be on hand at our local dealer whereas the older parts would likely have to be ordered. 8)


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PostPosted: Sun Sep 02, 2012 6:59 pm 
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Joined: Sun Aug 12, 2007 5:17 pm
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Location: Auckland NZ
personally I prefer the stainless sprockets.

The reason is nothing to do with the strength of the teeth as the plastic ones are more than adequate for the job (have never had or heard of a failure of the teeth): I prefer them for the ease of repair of a broken fin mast.

With both types of plastic sprocket (the ones with a 'set screw' to hold the finmast in and the ones with screw-in finmasts) you will find that you need to loctite the components together. I.E. you need to loctite the set-screw in to avoid it backing out and you need to loctite the screw-in mast in to stop it backing out. Having done this, if a finmast snaps (the break invariably occurrng flush with the sprocket where the mast exits the sprocket hole) you will have a devil of a job getting the stub of the finmast out of the sprocket and your drive back in service; it can be done... usually... but not at sea. The typical solution is to replace the entire sprocket by withdrawing the drive's central shaft - but this is much more expensive than just replacing the broken mast and it is not a job that I would be undertaking 'in the field'.

By comparison, if using the stainless drive (where the finmasts are held in place by a split pin) replacing a broken mast is a breeze - just remove the split pin and the stub of the mast drops out. Installing a new mast is also easy and both jobs can be done on the water if necessary - I have been there (as long as you are careful not to drop things into the well of the boat & down the drive slot or overboard). The spares required are limited to a finmast and some split pins (the split pins can wear through so it is a good idea to carry spares but they are also light, cheap and improvisable).

As to the suggestion that masts are more likely to break in the stainless drives - this is not my experience. I have had breakages in both stainless and plastic (setscrew) sprockets and apparently on the basis of length of use and/or treatment rather than according to the type of drive.

Re availability of spares: the 'split pin' finmasts are the same partnumber as the 'set screw' masts - one end for split pin; the other for set screw. As to the likelihood that they will become unavailable - i suspect that there are enough stainless and set screw sprockets out there that Hobie will continue to carry the masts for some time to come - they really stand behind their products in my experience. I have 2 spare masts which I carry one on each boat together with some spare split pins and a minimal toolkit for maintenance/repair in the field. If I get a mast breakage I order a replacement mast and have not had time off the water yet.

So from a personal POV I would prefer to do a long trip with a stainless sprockets drive than a plastic sprocket drive - I would carry spare mast(s), split pins (number determined by length of trip), tools (other spares too but that's is another topic) and I would cultivate good relations with my local dealer.

It should also be said that finmast breakages are relatively rare, especially in the shorter masts, but they do occur especially after long hard pedalling and/or bashing/bending the masts.


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