RS800 spreaders
Printed From: Yachts and Yachting Online
Category: Dinghy classes
Forum Name: Technique
Forum Discription: 'How to' section for dinghy questions and answers
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=9641
Printed Date: 27 Jun 25 at 8:33pm
Software Version: Web Wiz Forums 9.665y - http://www.webwizforums.com
Topic: RS800 spreaders
Posted By: CurlyBen
Subject: RS800 spreaders
Date Posted: 29 Jul 12 at 5:49pm
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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:
------------- RS800 GBR848 Weston SC |
Replies:
Posted By: JimC
Date 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... |
Posted By: CurlyBen
Date Posted: 29 Jul 12 at 7:24pm
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Hopefully now with pictures... Spreaders from top  Spreaders from bottom  Bracket  ------------- RS800 GBR848 Weston SC |
Posted By: CurlyBen
Date Posted: 29 Jul 12 at 7:37pm
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 Weston SC |
Posted By: JimC
Date Posted: 29 Jul 12 at 10:25pm
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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. |
Posted By: CurlyBen
Date Posted: 29 Jul 12 at 11:35pm
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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 Weston SC |
Posted By: dogslife
Date Posted: 30 Jul 12 at 9:44am
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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.
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Posted By: Oatsandbeans
Date 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. |
Posted By: JimC
Date Posted: 30 Jul 12 at 12:39pm
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... |
Posted By: CurlyBen
Date Posted: 30 Jul 12 at 8:10pm
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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.
------------- RS800 GBR848 Weston SC |
Posted By: JimC
Date Posted: 30 Jul 12 at 9:37pm
The way I do it? As recommended above I'd stick the mast in the boat without the shrouds attached to the spreaders. I'd then roll the boat on her side and work like that. The only trouble with working on the side is you need to put on a load of tension to avoid wire sag throwing you out. The first thing to look at is the relationship between the mast heel and everything else. If the mast heel/boom/majority of the track alignment is pretty good then (you're lucky!) and you have a datum. If not, well investigate. What can you move (if any) most easily of heel and gooseneck? Most likley mast heel. If you can rotate the mast heel and get a better alignment then do so, if not, well, put up with it. Now wind on up plenty of tension on the shrouds and measure the offsets to the spreaders. If you can take the measurements with the boat rolled on both sides so any sag balances itself out so much the better. Get the two sides as near as you can with available adjustment or whatever. Don't forget to check the mast is as vertical as it should be. I prefer lining up from the daggerboard case to measuring from the gunwhales - gunwhales might be different heights.. If you have a laser level or similar dig it out, its dead handy for this game. When the main spreaders are as near as possible symmetrical then repeat with the caps next. That's really about it. Allow at least a whole afternoon! But offsets from taut wire (or Laser) to spreader are the best thing to work with because you are effectively allowing for all the asymmetries there might be in the boat. |
Posted By: DaveT
Date Posted: 01 Aug 12 at 10:06pm
| tie a piece of string between your shroud plates, do the same between your spreader ends, they should all line up, simples |
Posted By: CurlyBen
Date Posted: 04 Aug 12 at 6:41pm
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Thanks for all the help and advice - I've just managed to get a new job which will be keeping me pretty busy for the next few weeks but when I've had a chance to get the boat on it's side I'll report back. Getting the boat out does mean disassembling the dog pen which might be interesting with the new pup! Cheers Ben
------------- RS800 GBR848 Weston SC |
Posted By: BarnsieB14768
Date Posted: 09 Aug 12 at 8:49am
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Morning. This is a common problem with double spreader plus time manufactured masts. Hence why it takes us so long to finish a multi spreader mast. Setup the lower spreaders as you normally would and the slowly adjust the cap spreaders so that they line up with the lowers. Hopefully you are only talking about rotating 1 - 2 hole movements, so should see minimal defection at the top of the mast. A chalk/laser line and front rivet attachment to each spreader bracket at point of manufacture would resolve this. |
Posted By: BarnsieB14768
Date Posted: 09 Aug 12 at 8:52am
| Forgot to mention to tie the lines between each spreader set as this will give you the best gauge for the alignment |