Stem fitting hole elongated.

[island808]

So, my stem fitting (place where you pin the forestay ) has a slightly wallowed out hole. Probably had loose rigging at one point? The forestay was just about failed when i bought it.

I drilled it from 6mm (.235") to 1/4 inches. And its pretty round and my new 1/4"pin is tighter. But there's less metal left. Kind of bugs me.

Any thoughts?

I know, im always asking things... Thanks for your patience.

[Ormonddude]

You could replace it or take it to a welder and have him add some material, he will basically run a couple of beads over it.

[seahouse]

Good to ask. Of course without knowing the width and thickness of the material it's tough to give an exact answer (It's a simple matter of calculating the cross-sectional area reduction on both sides of the hole).

But- you've only opened the hole up a small amount (about 0.015” or 6%), so if the remaining metal is otherwise in good condition (no bends, no cracks, your hole drilling reasonably smoothe) suffice it to say you should have no worries. (Note that this does NOT necessarily mean that the connection has been weakened by 6%).

Island808 you are right to be aware that there could be unintended consequences, but based on the info you provided, needn't be concerned in this case.

[Catigale]

But- you've only opened the hole up a small amount (about 0.015” or 6%), so if the remaining metal is otherwise in good condition (no bends, no cracks, your hole drilling reasonably smoothe) suffice it to say you should have no worries. (Note that this does NOT necessarily mean that the connection has been weakened by 6%).

Over sizing a Clevis pin actually places point load on the forestay plate very quickly. A snug fit distributes the load on the circumference of the pin, a loose fit concentrates the load to a point.

The strength of the plate in compression, even with a small point loading , however, far exceeds that of both forestay and the forestay plate mount. Thus, its either going to rip off the boat or snap the forestay before failing in this manner.

[island808]

Maybe you could reword that? I dont eally follow.

My reasoning for drilling the hole out a couple hundredths was to round up the hole again. I understand that its not good to have a loose fitting pin.


I dont understand the compression jazz. And snapping the forestay?


I was a bit worried about welding. Soften up or make brittle the steel.

How do they even come off? If i read right, the large panhead screws in the bow are the anchors for the stem fitting. Doesnt look easy to do.

[tlgibson97]

If you don't have an access panel forward for the bow hatch then you will have to cut one to get to the back side of the bolts. I didn't even know I had one until I was crawling up in the v-berth. Once you have access it looks like a simple job. I would just replace it.

[RobertB]

But- you've only opened the hole up a small amount (about 0.015” or 6%), so if the remaining metal is otherwise in good condition (no bends, no cracks, your hole drilling reasonably smoothe) suffice it to say you should have no worries. (Note that this does NOT necessarily mean that the connection has been weakened by 6%).

Over sizing a Clevis pin actually places point load on the forestay plate very quickly. A snug fit distributes the load on the circumference of the pin, a loose fit concentrates the load to a point.

The strength of the plate in compression, even with a small point loading , however, far exceeds that of both forestay and the forestay plate mount. Thus, its either going to rip off the boat or snap the forestay before failing in this manner.

Cat, I wonder - do you realize that the only change here is going up one size of the clevis pin - not increasing any loads? Yes, the amount of material above the pin was decreased but by very little. I think this is a good approach until he want to disassemble the bow to get to the forestay plate to replace - but I cannot see any reason to hurry here.

[seahouse]

Over sizing a Clevis pin actually places point load on the forestay plate

I think Cat meant to type "clevis pin hole", instead of "clevis pin"; then the posting is clearer.

It's just to point out that a larger hole, without also using a larger pin, will increase the point load at the contact point between the two (but that was not done here). It also emphasizes that the consideration of the loss of strength for the changes made, due to compression at the point, are negligible when compared to the loss of strength due to tension at the now-smaller areas adjacent to the hole.

Seems we're all agreed that the modification itself should not result in any loss of strength at the joint worth losing sleep over.

[island808]

Ah, im pickin up what u layin. Down.

I would imagine most people have worn out holes... On their boat. The mast moves quite a bit... The jib loads and unloads...

[seahouse]

Yup. And case in point from previous thread(s)- this is one of those locations where insufficient rig tension will cause an increased rate of wear, not to mention shock loading, on the area of contact between the pin and the hole.

[Highlander]

Hmmm Stern fitting u r all missing something here would that not be a backstay on an X not a forestay . Just wondering

J

[island808]

Hmmm Stern fitting u r all missing something here would that not be a backstay on an X not a forestay . Just wondering

J

assume bad joke rather than quick reading?

[island808]

Think ill pull the boat and get a piece of stainless tacked on there. Looking at the big boy boats, that seems to be their construction. 1/4 inch stem with a 1/4 inch plate where it pins... Making it 1/2". Better design anyway. Right now, the pin can saw back and forth. If the thickness of the forestay stem was closer to the width of the forestay .... Thingy... The pin wouldnt be so free to move side to side. Might even pin easier. Maybe add 1/8 or 1/4 depending on the size needed. Could even rivet it i suppose... But a nice spot weld or end stitch would be stronger... Probably.