What are these screw things called

[thinwater]

Just three thoughts:

1. I've seen some very badly corroded aluminum rivets. The worst was used to attach a stainless internal backer for boom main sheet attachments and similar (not my boat). They all failed and the backer moved. Just as people worry that stainless will cause corrosion of the aluminum spar, if the aluminum touches a stainless part the rivet corrodes. So I will offer that aluminum rivets ONLY make sense when ALL of the connected parts are aluminum. Simple logic.

2. Seldon and all of the spar makers specify monel. I'm pretty sure they are the experts.

3. My early 80s beach cat is still held together with monel rivets. It's spent a lot of time on the beach. No problems with the rivets. I have drilled out and replaced a few when replacing hardware; the hole was always reusable.

I have also used a lot of stainless rivets. I've never noticed significant corrosion or any difference from monel, but it is accepted that monel is better.

 

[rgranger]

Now you have me wondering about the aluminum backing plates that most Hunter boats have embedded in the fiberglass deck that holds a lot of the deck hardware in place. Most of the bolts going into those backing plates are stainless.

 

[thinwater]

Now you have me wondering about the aluminum backing plates that most Hunter boats have embedded in the fiberglass deck that holds a lot of the deck hardware in place. Most of the bolts going into those backing plates are stainless.

It is a pretty safe bet that the bolts are seized beyond all non-destructive attempts at removal. A common problem. Most commonly people remove the old hardware, cut the bolts off flush, and drill new holes 1" away. You could hope you hit the plate and tap the hole, or you can install nuts.

 

[dlochner]

Do your engineering then.

https://en.wikipedia.org/wiki/Shear_stress

Stress versus Shearing force.

Titanium for the Win !!

Jim...

Jim, I didn't say anything about stress or force, I said strength or the ability (in this case) of the rivet to stand up to a force applied at a right angle to the axis of the rivet.

If you are going to criticize a comment, at least get the context correct.

 

[dLj]

Titanium for the Win !!

There is no magic bullet.

Titanium has benefits and limitations, just like all other materials.

dj

 

[rgranger]

It is a pretty safe bet that the bolts are seized beyond all non-destructive attempts at removal. A common problem. Most commonly people remove the old hardware, cut the bolts off flush, and drill new holes 1" away. You could hope you hit the plate and tap the hole, or you can install nuts.

Well that would make sense! Except that while trying to trace down a leak into my head compartment I rebeded all the stanchions and deck organizers and winches on my Hunter 26 and I had no trouble removing the stainless steel bolts and putting them back in. However I admit that seems counterintuitive.