Oday 28 Standing Rigging question

May 24, 2011
139
Oday 28 Windmill Harbor Hilton Head, SC
There was a pro rigger in the marina a few weeks back up from the keys to do a big job on another boat and i stopped by to talk some.
Later that day he saw me up the mast and stopped over and looking / giggled at my rigging commented that it was very loose.
I asked him if he would have time to make the needed adjustment but he never got around to it.
So now i have been worried and reading about this issue and borrowed a tension tool.
I used a Harken pro tune digital tension gage.

I want to post my reading here for comments and suggestion due to the fact that i am not sure whats good or bad.
I am not a racer and the oday manual does not seem to provide this information.
I did not get a chance to read the backstay and do not know how to read the forestay since i have roller furling?
I understand there is a proccess when tweaking the cables somewhat....as far as which to do first i mean...

Baseline readings were

Port upper 352 lbs
Port lwr fwd 253 lbs
Port lwr aft 451 lbs

Starb uppr 343 lbs
Starb lwr fwd 319 lbs
Stard lwr aft 326 lbs

Thank in advance
 
Jan 27, 2008
3,045
ODay 35 Beaufort, NC
Not sure what you read but such different tensions on port versus starboard will probably put your mast out of column. My advice is to set the tension to start with based on the size of the wire and the recommended tension typically provided with the gauge literature. First make sure the mast is centered side to side in the boat by using a halyard to measure to a point equally distant from the bow on both sides of the boat. Then make sure the rake of the mast is correct to the amount recommended in the O'Day manual. Using a heavy weight on the mainsail halyard you should probably have about 6 inches of rake give or take a little. Now start to tighten the rigging about a half turn on each until you hit the tension numbers for your wire sizes. Fine tuning then requires going sailing. In about 12 knots of wind tack on one side, if the shrouds on the other side are hanging loose take them up a half turn. Tack to the other side, if they are loose tighten them a half turn. Repeat tacking and tightening until the shrouds stay tight in 12 knots of wind. Then lock them with cotter pins or seizing wire. In heavier winds the shrouds will be loose but that is an indication of a need to reduce sail by reefing. This is the method my research suggested, others may have different suggestions. My Loos gauge came with a chart on wire size versus rigging tension for I think a 15% of breaking strength free standing load on the wire. Here's a link to the chart.http://loosnaples.com/how-to-use-pt-series-tension-gauges
 
May 24, 2011
139
Oday 28 Windmill Harbor Hilton Head, SC
Thanks for that information, looks like from the link there that tension, (done via the steps given) on 7/32 size cable like mine should be close to 700 to 800 lbs.
Wow, that is alarming being that mine read so low. Adjusting to that setting has got me concerned that i would cause more surface cracks in the 31 year old deck,
I also read that headstay tension with roller furling are adjusted via the backstay?
 
Jan 27, 2008
3,045
ODay 35 Beaufort, NC
Your rigging loads should not be to the deck, the chain plates should be attached to your bulkheads and the lowers should be tied in to the hull with rods if the 28 is rigged like my 35? I had a Catalina 25 and the lowers on that boat were just to eye bolts through the deck. I think the 28 is likely more substantial than that method. Check some other boats in your marina if you are uncomfortable to get a feel for the tension. Pluck the rigging like a guitar string to see how taught it is and press on it to see how hard it is to deflect it. Your lowers should have a lower setting than your uppers since they are smaller diameter wire (true on my 35, I'm not sure of the 28). Regarding the headstay tension, think of the mast as pivoting fore and aft and as you tighten the aft stay the fore stay also gets tighter. There are different angles from the masthead to the chainplates so the tension on the headstay will be higher than the backstay based on simple vector mechanics. You can calculate the difference pretty easily using some trigonometry if you know the angles. It is similar to how a crane supports a load, the crane is in compression with the load pulling down on the head of the crane (this is your backstay) and the headstay or support cables holding the load up. Make sure when you set your rigging that you lay down on your back on the deck and sight up the sail track to make sure the mast is straight. You may need to tweak the lowers a bit to make sure it is straight. Do the same thing from the side to make sure it is straight fore and aft also. It should have a little bit of rake (not bend but the whole mast tilted just a little aft), like I said earlier check the manual for the amount, but probably around 6 inches.
Keep in mind the Loos tension chart is only about 15% of the breaking strength of the rigging. If your rigging is too loose your mast will seriously deflect when you are sailing and it can be dangerous, you will have terrible sail shape, unable to point, too much heel, poor initial stability, really bad weather helm, etc. and having a big bow in the mast could lead to breakage. Trust the Loos gauge tension numbers but make sure you know the size of your wire. As I noted I usually have to add tension from the Loos numbers when sailing at 12 knots of wind to keep the leeward shrouds from going slack. That chart gets you in the ballpark to get started with fine tuning. In no case should your lowers be tighter than your uppers as you noted in your initial readings.
 
May 17, 2004
5,032
Beneteau Oceanis 37 Havre de Grace
Your rigging loads should not be to the deck, the chain plates should be attached to your bulkheads and the lowers should be tied in to the hull with rods if the 28 is rigged like my 35? I had a Catalina 25 and the lowers on that boat were just to eye bolts through the deck. I think the 28 is likely more substantial than that.
On our 28 the uppers and aft lowers went to tie rods to the pan as you describe, but the forward lowers went to backing plates in the deck itself. I followed the guidance in the Selden tuning guide at http://www.riggingandsails.com/pdf/selden-tuning.pdf with good results.
 
May 24, 2011
139
Oday 28 Windmill Harbor Hilton Head, SC
Do i have to take the boom off to get a good measurement of aft mast rake?

The oday manual says the aft rake should be 7 inches aft at the goosneck.
 
May 17, 2004
5,032
Beneteau Oceanis 37 Havre de Grace
Do i have to take the boom off to get a good measurement of aft mast rake? The oday manual says the aft rake should be 7 inches aft at the goosneck.
I wouldn't guess that the boom would make any difference for the rake. You should make sure the sheet and vang are slack when measuring the rake and other tensions.
 
May 24, 2011
139
Oday 28 Windmill Harbor Hilton Head, SC
That selden document is very informative, however I have a keel step mast and all there steps about mast tuning is for deck step masts.
Did you notice that as well?
 
May 17, 2004
5,032
Beneteau Oceanis 37 Havre de Grace
That selden document is very informative, however I have a keel step mast and all there steps about mast tuning is for deck step masts. Did you notice that as well?
Yeah it's weird that they only talk about deck stepped mast tuning after having a section on keel stepped masts earlier in the paper. I figured that it likely didn't make much difference at least to the overall concepts, provided that you maintain the constant curvature that they talk about in the page on keel stepped masts.