Eye Bolt Strength

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Eye Bolt Strength

Postby Interim » Mon Dec 16, 2013 5:58 pm

I'm working toward flipping my hull (79 DS II) to do some repairs. I plan to drop the trailer tongue (raising the after section) and put saw horses under the transom. Then lifting the trailer tongue will rest the transom on the (properly shimmed) transom. We will then lift the bow on a line attached to the eye bolt. Once we pull the trailer out, we can lift the back and roll the hull over (pivoting on the line through the eye bolt) and gently place it upside down on supports.

Two questions:

1) can the eyebolt hold half the weight of the hull (assuming it is in good condition); and
2) are there faults in this plan I don't see?

Thanks.

--john
1979 DSII
Interim
 
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Re: Eye Bolt Strength

Postby Alan » Mon Dec 16, 2013 7:26 pm

That sounds like a good way to flip the boat, but...

If you're talking about the hardware that's used to pull the boat onto the trailer (also known as the bow hook), it may be corroded on the threaded ends, which are inside the bow tank where you can't see them. Mine looked good from the outside, but when I put an inspection port in the cuddy bulkhead, I found out that one of the nuts was pretty badly rusted.

An inspection port is a good idea, not just to inspect the hardware, but to inspect any flotation material that might be in there.
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Re: Eye Bolt Strength

Postby GreenLake » Mon Dec 16, 2013 7:48 pm

Why not use a sling under the front end of the boat? That's got to be safer than relying on the bolt.

When you load your boat on the trailer, the load on the bolt is tension along the axis. If you use the eye to raise the boat, the load will be sideways - depending on how firmly the eye mates with the surface, that would be either shear or bending load. Does it matter? Maybe not in this instance, but loading any fixture in a direction other than the design load is always something you should think about very carefully :)

Now, Alan's point about possible bolt failure. When I bought my DS, the bolt failed the second time I loaded the boat. It had an invisible crack that had corroded all the way. It was good for loading the boat once, then it failed. There was absolutely no indication of impending failure. Now, when you load a boat on the trailer, the worst that can happen is that it gets away from you and drifts. In your scenario, you are lifting the boat, and, in case of bolt failure, you are risking possibly severe damage - hence my recommendation to consider alternatives.

When using a sling, as an extra precaution, tie a line from near the bottom to some point on the boat further aft - just so the sling can't slide forward and slip off the bow.
~ green ~ lake ~ ~
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Re: Eye Bolt Strength

Postby Interim » Tue Dec 17, 2013 8:16 am

Excellent information. Thank you both.

My other idea is to rent a bobcat and suspend the boat from two slings, and roll it in the slings. I was accused of using this as an excuse to rent a bobcat, though.

Thanks for saving me a a bow hook, and possibly a deck!

--john
1979 DSII
Interim
 
Posts: 141
Joined: Mon Sep 30, 2013 8:40 am
Location: Nebraska

Re: Eye Bolt Strength

Postby jw » Tue Dec 17, 2013 10:02 am

We lifted "half the boat" on the bow eye on two different boats without incident. The eyes where is good condition and we had inspection ports. Although I'm not sure we looked at them that closely :D
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Re: Eye Bolt Strength

Postby GreenLake » Tue Dec 17, 2013 6:56 pm

I would be tempted to trust my replacement eye bolt as well, because it's been good for many years now, but the way the first one failed was as lesson. Inspection ports would not have mattered - the fracture occurred where the bolt was inside the bow layup. Just no way we would have been able to see anything. "When taking a risk, be mindful not only of its probability of occurrence but also the gravity of the outcome" -- something like that.
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