Elongated hole in stem head fitting

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rajjes

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I have finally removed the mast for re-rigging and was dismayed to find the hole in the stemhead fitting for the forestay considerably elongated with wear as per attached pic.

Stemhead.jpg

How serious is this? Should I repair, ignore or possibly widen the other smaller hole and use this instead?

Boat is an old Moody 36 with 8mm rigging.

Regards and all the best to all!

Duncan
 
It certainly doesn't look healthy. I would want to think through why the wear/distortion is occurring - was the old pin too small for instance? or the rigging too loose? I might be tempted to bolt a new small stainless plate through the old hole and attach the new rigging to a properly-sized hole in that.
 
Well the forestay pin is a standard 1/2" pin but is now very slack in the existing hole. The rigging could have been lacking in tension as well. I have had the boat for just a few months now and re-rigging was high on the priority list since the survey.

Going forward, my preferred option at the moment is to re-bore the other hole for 1/2" and use that with all new fittings including turnbuckles. Hopefully it will be as strong as new!




.
 
It is a question of area of metal left in the direction of pull. It this area is less than your 1/2 inch pin area then you will have a weak point. if the area is still greater than the pin then you could use it as is. It would be better with a larger pin so more surface area (blunter cut into metal). I do like garvellachs suggestion of side plates down to the lower hole or as you propose use the lower hole. good luck olewill
 
I would weld a doubler plate to both sides of the same thickness as the primary, extending down the plate as far as possible. Re-drill in the same position. The bearing stress on the pin will be a 1/2 of the original and the stress in the weld should be low enough to prevent fatigue.

I would check all the welds in the fitting for cracks.

Refit the forestay with the proper pin and toggle to prevent out of plane stresses.
 
Thanks to all for feedback.

Yes, there was a toggle on the forestay and apart from the distorted hole there aren't any cracks in the fitting or welds.

Will measure carefully the metal left vs the pin and take if from there. At least the stemhead plate is substantial!

All the best to all!
 
True. However the strange thing is that the pin was a snug fit in the toggle and it all seemed original. The attached pic shows what was visible before dismantling.

rrpin.jpg

It would seem that the stemhead hole was larger than the toggle pin from the start. .

Anyway, looking at this pic, I am becoming more convinced that widening the other hole to fit the 1/2" pin is the way to go.
 
rajjes said:
True. However the strange thing is that the pin was a snug fit in the toggle and it all seemed original. The attached pic shows what was visible before dismantling.

View attachment 38258

It would seem that the stemhead hole was larger than the toggle pin from the start. .

Anyway, looking at this pic, I am becoming more convinced that widening the other hole to fit the 1/2" pin is the way to go.
Click to expand...

Just make sure the hole isn't too deep into the fitting such that the toggle binds on the fitting. It will be hard to widen the hole neatly if you need to ensure the hole is closer to the edge of the fitting.
 
The minimum distance from the centre of the hole to any edge of the plate is 1.75 x the nominal diameter of the hole.

I suggest that the pin is fitted from the other direction as the anchor may shear the split pin.
 
penfold said:
I'd overbore it and get a sleeve made up to bring the diameter back down to 1/2".
Click to expand...
Not without making sure the metal around the original hole is sound. Stainless is notorious at giving way without warning because of fatigue or work hardening. I have had it happen on a 'repaired forestay fitting, thankfully without losing the mast. (It failed on a downwind run, and the jib halyard held it all in place until things could be sorted). Rebuild the fitting (i.e have the old plate cut off, and new fabricated and welded on) which will involve removing it from the boat. Also would be possible to have the hole built up by welding then re-drilled. the heat will resolve any fatigue problems. Again involves removing the fitting. Attempting to plate each side of the hole will mean a new wider toggle to accommodate the thickness of the plates, and will reduce the space available for the anchor chain to run, making the whole thing a bit unwieldy. In any case it will be difficult to get a secure fastening to it with making a botch of it.
 
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