I'm replacing the rod rigging on 44-04 Hatha, and wondering whether to go with the -17 rod at 17,500 lb min breaking strength, or go up to the -22 at 22,500 lbs
The -17 coincides with what is on the sail plan- 16,500 min breaking strength for head stay and back stay; 17,500 for shrouds. The -17 fittings use the .625" pin size as well, which is like what I have taken off the boat.
The reason I'm questioning this is that the -17 at 8.4 mm is significantly smaller than the 10.1 mm I'm replacing, which is probably original. Even the -22 is still a little under at 9.5 mm, and those fittings require .75" pins (19mm). I am not sure what size holes are in the chainplates, but I believe they are .625" as well.
Is the difference between the new and the old simply the result of 40 years of technology and should I just go with the minimum breaking strengths as shown on the sail plan? There are no world cruises planned in the near future.
Dear Tony
There are two aspects to consider for standing rigging - strength and stiffness. Strength is necessary for long life, and stiffness affects the amount the mast head falls off to leeward when on the wind.
If you could confirm the rig length - single spreader short or tall - some observations can be made in reference to your questions.
Kind regards
Lars
So far the plan is to use the the Navtec Nitronic rod with 550 turnbuckles, toggles, etc. Also Harken furler unless someone can make a compelling case for the Reckmann. The chainplates, Nautor toggles, and mast fittings all are for.625 pins, so at this point we are set up for the -17 rod
Dear Tony
Made some calculations with -17 rod as well as 10 mm 1x19 wire assuming that Hatha has normal stability.
Strengthwise both rod and wire are OK, the stated wire strength is slightly different depending on whether it is of European or US origin.
With a hydraulic backstay tensioner it is recommended that the headstay is one size bigger than the backstay, the geometry of the rig produces some 20% more load in the headstay. If the headstay pins are 0.625" Navtec have -22 small pin eyes with this dimension.
-22 shrouds are not needed for strength, but they would reduce rig deflections. Pin sizes would cause problems though.
Is your stemhead fitting aluminium or stainless?
Which backstay tensioner is it, and what loads do you use?
When heeled to 20 deg on the wind the rod rigging produces smaller deflections than the wire. Here below two diagrams showing what to expect if you do not pre-tension your rod rig, and what the difference is if you do.
In the first case the mast top deflects 0.58 m, in the second 0.24 m. These are estimated values, as the stiffness of the chainplates and mast step is a guess. The wire rig deflects some 18% more than these numbers.
If you count the number of turns on the rigging screws in connection with the pre-tensioning I would appreciate to get these numbers, they give hints of the total deflection.
Kind regards
Lars
Dear Tony
Made some calculations with -17 rod as well as 10 mm 1x19 wire assuming that Hatha has normal stability.
Strengthwise both rod and wire are OK, the stated wire strength is slightly different depending on whether it is of European or US origin.
With a hydraulic backstay tensioner it is recommended that the headstay is one size bigger than the backstay, the geometry of the rig produces some 20% more load in the headstay. If the headstay pins are 0.625" Navtec have -22 small pin eyes with this dimension.
-22 shrouds are not needed for strength, but they would reduce rig deflections. Pin sizes would cause problems though.
Is your stemhead fitting aluminium or stainless?
Which backstay tensioner is it, and what loads do you use?
When heeled to 20 deg on the wind the rod rigging produces smaller deflections than the wire. Here below two diagrams showing what to expect if you do not pre-tension your rod rig, and what the difference is if you do.
In the first case the mast top deflects 0.58 m, in the second 0.24 m. These are estimated values, as the stiffness of the chainplates and mast step is a guess. The wire rig deflects some 18% more than these numbers.
If you count the number of turns on the rigging screws in connection with the pre-tensioning I would appreciate to get these numbers, they give hints of the total deflection.
Kind regards
Lars
The small pin eyes should allow me to use the -22 headstay. I like that idea and will need to work out how the furler installs. We could easily do the same for the backstay, would there be any advantage?
Would there be any advantage to use -17 cap shrouds with -22 lower shrouds? I think the fittings could be worked out although I don't yet know how to fill the 1.625" space at the spreader tips. The -22 jaw is only 1.25" wide and the -17 is 1". I would think the fore and aft lowers would be -17 rod.
The stemhead fitting is aluminum, the backstay ram I believe is Navtec A 250-17, it is away for servicing. 3000- 3500 lbs seems to be about what pressures we have used, but it has been some time since we have been in service and I'm not sure I remember correctly.
I will definitely share with you the data from pre- tensioning the rig when we get to that point, but either my rigger or you will have to explain that process to me as I am unfamiliar with it.
Dear Tony
Increasing the backstay to -22 would result in somewhat reduced elongation, which is rather useless here, but weight and windage increases.
Using -22 V-1 with -17 D-2 would reduce the V-1 elongation by 3.3 mm, this reduces the earlier mentioned masthead deflection by 20 mm when not pre-tensioned, and by 8 mm when pre-tensioned. Further the two rod sizes need to be connected at the spreader end.
The big gap in the spreader ends suggests that there has been linkplates with eyes, but with the same size rod a spreader bend could be used. This needs a filler piece or equal to support the bend in the fork. At what distance is the spreader end pin from the mast wall at the spreader root?
The recommendation is to inspect the aluminum headstay chainplate carefully for cracks or deformation.
With a -17 backstay tensioner the recommended maximum pressure is 2.7 kpsi, over that very little is gained in headstay sag. This corresponds to a backstay tension of 5800 lbs.
Backstay tension should be released off the wind in conditions where there is risk of broaching. The rather long topmast above the top shroud attachment may make the top unstable sideways.
Instructions for pre-tensioning are found in the Maintenance Section of this website under Rigging Setting Up. Pls have a look and feel free to ask if you have questions
Kind regards
Lars
Thank you for the info, we will go with the -17 backstay.
Regarding the spreaders, the photo below shows what we had, with the large jaw being on the D-2. I can duplicate this with the -17 D-2 rod and jaw and the -22 V-1 with small pin eye. The toggle to the 5/8" chainplate pin at the bottom of -22 V-1 can also be accomplished. We would need (2) 5/16" spacers to fill the extra space at the spreader tips since the new jaw is much smaller. Sounds good?
Sorry I don't know the length of the spreaders, they are with the mast getting refurbished, but with this system it's not critical?
I can see no cracks in the aluminum at the headstay chainplate, but there is a large, flanged, stainless bushing through bolted there. I know I would never be able to get it off but there are no signs of corrosion or anything else I can see that gives me concern.
I have attached a photo showing deformation at the masthead headstay tang, any cause for concern or suggested repair here?
Dear Tony
Suggest that you also consider the terminals chosen the other way around, i.e. a -22 jaw on V-1, with a -17 standard eye on D-2. This would also have a thicker pin, which better can resist the bending loads caused by the 1.625" gap. Pin bending needs to be checked here.
According to catalog information a -17 eye does not fit into a -22 jaw, but the discrepancy is 0.01" so maybe tolerances allow it to go in?
Spreader length is of interest because the D-2 angle against the mast is likely to be less than 10 degrees, i.e. very narrow, this increases main span loads quickly.
The photo of the headstay lug shows some deformation, and it would be good to document the present situation accurately, and check regularly if it changes, or cracks appear. Welding should not be used near the hole, but if there is enough gap sideways between the lug and the toggle reinforcements could be considered.
In case you now use all rope halyards it is advisable to round off the edges of the halyard sheave side plates.
Kind regards
Lars
Yes this is an old thread, but Hatha sailed for the first time in many years last Easter Sunday and I remember I had promised to send you our pre tensioning info.
I opted to go with -17 rod for all the shrouds and backstay, and the -22 headstay. Regarding the excess space at the spreader ends, we welded in aluminum plate to close up the gap while they were still at the yard. The spreader length is 48", per plan.
The first day we put in 1 1/2 turns on the shrouds, in light conditions. A week or so later I added another 1/2 turn, again in light conditions, followed up most recently by another full turn, this time with the boat well powered up in 15-17 kts. So a total of 3 turns to date. Backstay tension in the heavier breeze seems good around 2500 lbs, as you recommended.
I could definitely see the mast column straighten thruout the process, especially in the beginning. We will go like this for a while and possibly add another 1/2 turn sometime in the future.
Thank you for your invaluable help, it feels great to be sailing again.
Dear Tony
Thank you for the information.
Good to hear that you are sailing again.
The number of turns you inform confirm that the deflections are smaller than expected, this is very good. Would appreciate to hear what the final turns are at the end of the season.
If you find it necessary to add turns now and then this indicates that the chainplate knees are slowly deforming, and need to be checked for damage, particularly at the inboard and lower ends where they connect to other structure.
Kind regards
Lars
