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RS800 spreaders

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CurlyBen View Drop Down
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Post Options Post Options   Quote CurlyBen Quote  Post ReplyReply Direct Link To This Post Topic: RS800 spreaders
    Posted: 29 Jul 12 at 5:49pm
Right, I'm really scratching my head here.. After a couple of years where life really got in the way of sailing I'm trying to get my RS800 sorted out and back on the water. One of the jobs I needed to do was replacing the lower spreaders (Holt mast). I got the new ones from RS and cut them down to the same length as the old ones (on RS's advice, they were about 30mm too long as supplied) being careful to cut the outboard end so I didn't disturb the inboard end holes. Set them up according to the class rules and was happy.. until I sighted down the mast. The port spreader has significantly less deflection than the stbd (the stbd looks correct, as it's at pretty much the same angle as the upper spreader).
To try and sort the problem I've:
  • Taken out the spreaders and compared them. They're identical
  • Switched the spreaders round, the port spreader has less deflection both times round
  • Checked the bracket is even on the mast - about .2mm away from symmetrical about the mast track, so I don't think that's the problem
  • Tried to measure the spreader bracket - not very easy, but no difference I could make out side to side
which to me should mean that when the spreaders are in the same holes they should be at the same angle, but they're not! I'm a bit reluctant to start having the spreaders on different holes each side, but can't see what else I'm missing. I'll post some pics up when the rain's passed. In the mean time if there's anything obvious I should be checking, please say!
RS800 GBR848
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JimC View Drop Down
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 12 at 7:23pm
Make sure the mast cannot twist and is exactly straight. But .2mm probably multiplies into quite a bit at the end of a spreader. Probably the best thing to do is to check a bunch of other people's boats, because I bet none of them are exactly symmettrical...
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CurlyBen View Drop Down
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Post Options Post Options   Quote CurlyBen Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 12 at 7:24pm
Hopefully now with pictures...

Spreaders from top

Spreaders from bottom

Bracket

RS800 GBR848
Weston SC
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CurlyBen View Drop Down
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Post Options Post Options   Quote CurlyBen Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 12 at 7:37pm
Originally posted by JimC

Make sure the mast cannot twist and is exactly straight. But .2mm probably multiplies into quite a bit at the end of a spreader. Probably the best thing to do is to check a bunch of other people's boats, because I bet none of them are exactly symmettrical...
Thanks Jim - unfortunately I can't check other boats at the moment as I don't have a club! I can cope with a bit of asymmetry, but this looks too much to me. I might have to try and rig up some way to measure the angle from mast to spreader. Unfortunately there isn't a lot of wiggle room - not many positions the spreader can take, and the class rules state that a line stretched from shroud to shroud should measure 150mm +- 10mm, which is not much movement at the root. The newer masts have a fixed spreader, unfortunately I don't think it can be fitted to these masts.
RS800 GBR848
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JimC View Drop Down
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 12 at 10:25pm
Track wobbles about a bit too doesn't it... It almost looks to me as if the goosneck is even more out of line as if the whole spar has twisted, but I find it hard to imagine that's possible. Must admit when I do spreaders I drill the holes for the second one in place so as to get them entirely symettrical as I'm not a good enough fabricator to do exactly even spreader brackets.
Think in this case you're just going to have to take the best compromise and juggle positions as much as you can to get things as even as practical.
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CurlyBen View Drop Down
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Post Options Post Options   Quote CurlyBen Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 12 at 11:35pm
You've got me worried now - the mast has been broken at least once once (I think twice) before I bought it, once at the upper spreaders. I wonder if the repair wasn't lined up properly, as it doesn't look like a professional repair (RS told me it had just been repaired by Ashdown Marine when I bought it though, and I would have thought they would have noticed something like that). The track is a little snaky, though it's not to bad to hoist. Looks like I need to do some more measuring and see what's in the right place and what's not. The gooseneck could well have been refitted at some point, as it's on a plate rather than fixed straight to the mast.
If there's been a poor repair it might also explain why the mast wants to roll to port on the trestles - not normal instability, but a real roll.
RS800 GBR848
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Post Options Post Options   Quote dogslife Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 12 at 9:44am
Try putting the mast in the boat with the shrouds detached from the spreaders (set the same on both sides) and measure the distance from spreaders to shrouds. At the very least this should confirm whether the spreader bracket is out of true with the heel fitting.

Edited by dogslife - 30 Jul 12 at 9:44am
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Post Options Post Options   Quote Oatsandbeans Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 12 at 11:29am
I am a great fan of RS but I don't trust them to put spreader brackets on consistantly. I have got 2 rs500s and if you set them both up with the pins in the recomended holes you get different levels of prebend. So I don't bother too much about the actual pin holes I just set the prebend to what I want.
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JimC View Drop Down
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 12 at 12:39pm
Originally posted by Oatsandbeans

I don't trust them to put spreader brackets on consistantly.

I don't suppose any of the other manufacturers are any different. To my mind the risk for the OP is to get so psyched out by the state of his rig that boatspeed goes down the tubes, which is why it would be useful to look at other folks rigs and see how inconsistent they are too, so that you don't feel too badly about it...

Maybe its just incompetence on my part, but I find spreaders a royal pain in the neck to set up properly.
A few weeks back I had to alter the spreader system on an old Moth - the "spreader" is a single piece unit which meets both the shrouds and the forestay and pivots on the front of the mast. I swear it took me an hour of fiddling and remeasuring before I was happy that I had all four holes marked in the right places...
Not too much of that sort of thing can be going on if you want your new mass production boat to come in at a reasonable price. I'm sure they jig drill them at the factory, but even so...

Edited by JimC - 30 Jul 12 at 12:46pm
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CurlyBen View Drop Down
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Post Options Post Options   Quote CurlyBen Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 12 at 8:10pm
Just wrote a nice long post and the forum rejected it!

Did some measuring today - cut a slot in a board and marked up the spreader positions on it. 135 degrees between the lower spreaders and 120 between the uppers. The stbd spreaders are near enough parallel, and the port are at about 15 degrees to each other (I realise having upper and lower spreaders parallel isn't crucial, but it's a handy reference at the moment). Measuring the centre lines neither upper nor lower appear to be perpendicular to the track, but are twisted off centre in opposite directions. I'll do a bit more experimenting when I get time, but I don't really want to just change one of the spreaders until I really know where the problem is.

Does anyone know how a datum is established when setting up a new carbon mast? There's no decent reference.

Jim, I appreciate what you're saying about getting too worried about rig symmetry rather than boat speed, but even though I've not sailed the boat for a couple of years I do remember having much more difficulty going upwind on one tack than the other. It's part of the reason I wanted to spend some time on setting the boat up properly. I've not got much practice at set up unfortunately, as a lot of my sailing has either been in the boats my school owned or sailing school boats at centres I was working at. I've never really got to grips properly with a single boat before, so it's a bit of a learning experience.


Edited by CurlyBen - 30 Jul 12 at 8:11pm
RS800 GBR848
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