[Reefpoints]

Hello all, I believe I may have found yet another thing to fix!

I was in the process of re-attaching the masthead to the mast in preparation for wiring when I was struck by how weird my backstay arrangement is:

The wire terminates about a foot shy of the masthead where a pair of steel "tangs" (unless someone knows a better term) carry the load to the masthead. Please see the photos below

My concerns are:

1) Is this a safe and appropriate arrangement?

2) Is this likely how my SanJuan 28 was built, or is this probably someone else's aftermarket idea?

3) Should there be spacer at the upper clevis pin between the tangs

4) Is tying the topping lift to the lower clevis pin an acceptable method of attachment?

5) The lower clevis pin is small relative to the hole in the swaged end fitting - is that ever ok?

As always, thanks for your input!

 

[Faster]

Seems unnecessarily complicated, but assuming it's been there for some time it's probably adequately strong. It would 'look' better with that upper spacer but I don't think it's critical. Thicker would provide more peace of mind, I suppose.

We have a similar extension on our lower forestay attachment, but it's more robust - it's there to provide anchor clearance under the furler drum. Other than the backstay being too short I see no reason for that particular assembly.

The small pin/large hole may be more problematic over time.

If you suspect this setup is more than 15/20 yrs old it may be time for a new backstay anyway, at which point you can get rid of the extra bits.

 

[findrichard]

I would look carefully to see if there is any elongation in the holes where the pins are. If there is, either due wear or stretch I would have thicker ones fabricated before reassembly. The pin size as well as the holes in the tangs will need to match the swedge fitting.

 

[RichH]

There is the probability that these tangs are OK .... maybe.

I would suggest that a better place to have them is at the near the chain plate connection near the deck. Here's why:
You can constantly observe them .... for signs of fatigue such 'color change', cracking, etc. You need to go up the mast to observe in their present position.
That 'gunk' may be a form of 'rusting' or crevice corrosion accelerated by fatigue cracks .... looks funky / 'unhealthy'.

Id suggest moving them to the 'bottom' of the wire. Maybe replace them entirely with an extra long 'rigging screw' or multiple rigging screws/turnbuckles (at the bottom). Id remove them and check them for 'elongation' of the connection 'holes', inspected with (pocket) microscope for cracks, etc. etc.
If the backstay is well over 10 years of service (hard sailing), consider to entirely replace the entire backstay.

An engineering rule of thumb: if it looks 'funky', it probably is funky. I dont see much 'meat' to support those pins that connect to the mast head, nor the backstay proper and that can easily lead to 'ductile' failure .... elongation of the 'holes' and fracture of the material at right angles to the applied stress.

 

[christian.hess]

those thangs are extenders sold by many guys, harken, gaurhaur, hayn etc...seem they made the backstay too short and the tang had that size clevin pin and hole combo...

or it might be that the backstay was made oversize or they messed up the size on the top pin hole on the stay(seems that way in the pics) as the mast pin at the top looks like the same size as the bottom one...just longer.

if so at the least I would find out what pin sizes are correct top and bottom on your backstay for your model boat

if indeed its the pin that is undersize(or the backstay swage hole too big) the least you can do is bush the swage hole or sleeve the pin in the middle so it fits snug...

one size under if bushed will not give you trouble

the tangs do look thin but they are supposed to be half the thickness each side of what your chainplate thickness is...this is from searching some for my boat that I made extenders for in the end.

my plates where 1/4 inch so I used 2 1/8ths halves to extend the stays

i.e whats the thickness of your backstay plate?

lastly although a spacer is not needed or supplied with most tang extenders you can make one to make the tangs parallel so they linear pull is better...and stronger.

I think I have a pic of my extenders somewehere

they are made in brushed 304 stainless which was a mistake, I should of mirror polished mine like I did the plates.

btw most all tang and stay extenders I was looking for online were all made of 304 stainless...

not a close up but you can see they are installed on the aft lowers at the bottom like rich says always there for checking:

 

[RichH]

What is the approximate length of these tangs?

... you see this on a lot of raced boats using bolt-roped dacron mainsails which develop 'excessive weather helm' ... and the mast is raked forward to compensate for the weather helm .... and without considering faults that are developing in the mainsail.

The second question ... does your mainsail appear to be very baggy?

 

[Jeff_H]

My best guess is that the backstay was cut shorter so that one of both swages could be replaced at some point in the life of the boat. I completely agree with RichH that the plates should be at the deck and not at the masthead. I would also suggest getting a shorter clevis pin which should allow the loads to be transferred more evenly to both of the tangs. If there is room I would add a short tang hung on the clevis pin for the backstay eye and use that to hang your topping lift which should have a thimble where it attaches to a shackle on the tang. If there is insufficient room between the cheeks of that receive the backstay eye, then I would make a 'U' shaped tank that would hang on either end of the backstay clevis pin (you'll need a longer pin) and attach the topping lift to that.

Jeff

 

[Reefpoints]

Wow - a lot of great insight and advice from you all - thank you!

Faster,

I don't know how old the rig is, this my 3rd season with the boat. Everyone's advice is making me lean toward replacement at this point. At the very least, I'll probably replace the tangs with more robust ones.

findrichard,

There was no elongation of holes, but the upper clevis showed significant ruts where the tangs wore at it - I've replaced it.

christian.hess,

Thank you - having a rule of thumb for sizing makes all the difference. I'll measure my chainplate and see if these fit the bill; I think they are undersized though.

What is the approximate length of these tangs?

... you see this on a lot of raced boats using bolt-roped dacron mainsails which develop 'excessive weather helm' ... and the mast is raked forward to compensate for the weather helm .... and without considering faults that are developing in the mainsail.

The second question ... does your mainsail appear to be very baggy?

Great idea, if I do replace with thicker tangs, I'll move them to the bottom. the gunk was a thick tar-like substance that I thought my have been applied as an anti-chafe for the topping lift. I've just never seen or heard of such an approach.

I'm embarrassed to say that the main is very old (mid 90's), however the fabric still holds up to the "tear test" and I've squeezed a little more life out of them with frequent use of the cunningham so it doesn't seem too baggy..t is on my list of things to replace. I was going to replace 1 sail a year (last year asymmetric spin), this year genoa, next year main - maybe I should rethink the order..

JeffH,

Thank you for the great idea on a proper topping lift attachment.

 

[RichH]

snip ..

I'm embarrassed to say that the main is very old (mid 90's), however the fabric still holds up to the "tear test" and I've squeezed a little more life out of them with frequent use of the cunningham so it doesn't seem too baggy..t is on my list of things to replace. I was going to replace 1 sail a year (last year asymmetric spin), this year genoa, next year main - maybe I should rethink the order..

Why I asked the question was to probe for the 'reason' for the addition of 'tangs' to the upper backstay, as I see such on a lot of boats attempting to rake the mast forward and for all the WRONG reasons. This slow 'development of weather helm' can usually and simply be traced to changes (shrinkage) of a dacron sail's luff boltrope; and, instead of simple sail 'maintenance' the skipper will radically rake the mast forward to compensate for evolving sail shape changes.

Here's a link which should help you to evaluate such a situation ... and possibly lead to a reason to remove such vulnerable tangs, and perhaps lead you towards some easy and economical 'repair' of your mainsail and its SHAPE. See post #1 in the following: How to properly RAISE a woven dacron mainsail - SailboatOwners.com

 

[Reefpoints]

I just noticed in my boat manual that it specifies the shrouds and forestay wires to 7/32" size, but the backstay is spec'd at 3/16". Why would that be? Why should it be a size smaller?

Seems odd to me.

 

[christian.hess]

do you have a fractional rig? they tend to be ligher stayed if fractional or 7/8ths or even 3/4 rigs on some boats

not that uncommon

 

[Reefpoints]

do you have a fractional rig? they tend to be ligher stayed if fractional or 7/8ths or even 3/4 rigs on some boats

not that uncommon

Nope, a masthead rig.

 

[christian.hess]

Nope, a masthead rig.

now that you know the original sizes can you confirm that indeed the backstay is original size or slightly oversize and maybe the reason your pin is undersized for the swage?

 

[Alex W]

I just noticed in my boat manual that it specifies the shrouds and forestay wires to 7/32" size, but the backstay is spec'd at 3/16". Why would that be? Why should it be a size smaller?

Seems odd to me.

The backstay has a more obtuse angle to the mast and needs less tension to have the same ability to hold the mast in place. I've seen other boats do this too, the Newport 28 is one example:
http://capitalyachts.info//newport28/Owner's Manual - Newport 28.pdf

7/32" cap shrouds, 3/16" backstay.

The Yankee 30 uses different rigging sizes all over the place. Cap shrouds are 9/32", backstay is 7/32":
http://3.bp.blogspot.com/-Z3Co4aPHk...64OGjT8/s1600/1999+Yankee+30+sail+plan300.jpg

3/16" and 7/32" seem pretty small for a boat the size of a San Juan 28 or Newport 28. My not much heavier or larger rig Pearson 28-2 uses 1/4" rigging (but it also has a very different style of masthead rig with swept spreaders). However I wouldn't go changing rigging sizes on a whim, it requires being careful when tuning the rig because going to 15% or 20% of breaking strength on the shrouds is now a much higher tension than what it would have been on the original rigging.

 

[Reefpoints]

The backstay has a more obtuse angle to the mast and needs less tension to have the same ability to hold the mast in place. I've seen other boats do this too, the Newport 28 is one example:
http://capitalyachts.info//newport28/Owner's Manual - Newport 28.pdf

That makes a lot of sense - thank you!

 

[Reefpoints]

Thanks all for your help, I wanted to follow up:

I've decided to replace the backstay (and I won't be using tangs). Since I had already replaced my forestay (search my recent threads) and now the backstay - I decided to just go ahead and replace all the shrouds too.

I got a great deal on the 5 cables (2 uppers, 2 lowers, and backstay with new turnbuckles) from George Moose at Fawcett's in Annapolis. I think the price is good because he doesn't travel out to the boat; you just bring him the the old stays and fittings you want replaced and he measures and swages it. If your mast is already down for other work/reasons, this approach is a no-brainer.

 

[christian.hess]

cant argue that

another great place is rigging only...had them sent down here...made up the ends and called it a day

cheers

ps. keep the tangs...they are great for emergencies...also keep your old stuff wrapped and ready to use as spares...a few mechanical fittings make rigging work easy just in case