Ernie’s response to Dave about the metal to metal wear on the boom end castings is true in my opinion if the metal parts are working upon each other. In the picture shown with the eyebolt passing thru and secured to the casting hole moves the wear to the eye bolt and the carabiner. The cast aluminum is spared any abrasion by the fact that the eyebolt is transferring the wear point. The only question would be if the thickness of the casting can bear the off center load. In my opinion because of its thickness .
If the ring bolt is precisely sized to the hole, and the fastening nut is absolutely secure so that no movement can occur, and there is no corrosion occurring between the stainless and the aluminum, then I agree with Brian that Dave’s connection will work out. In the meantime, however, the carabiner will beat up the rest of the mast fitting.
If the connections aren’t perfect, then Ernie’s accurately describing the potential problems. In either case, he’s also on point about the primary thrust of the thread.
My feeling is that you cannot go wrong with a soft (Dyneema) connection to/through a hole in a CAST aluminum component (originally designed to be ultra strong, which it isn’t). The holes in the castings at the front and back of the boom are literally begging to be enlarged, misshapen and, ultimately, torn open by putting bolts, shackles, or anything metallic through them. Also,in this particular case, you get to use the unbeatable strength of the entire casting due to the Dyneema being wrapped around the casting. True, one day, even the Dyneema may fail but it’ll take years and you’ll bask in the peace that comes with knowing that you are not wrecking those darn holes in the castings themselves.
This design was fine when first introduced but, in time, we’ve all had failures due to its weak points.
This is life (and Nonsuchery). We discuss, we change, we improve, we learn. Several feet of Dyneema (that will support 10,000 lbs. +) costs $3.00. Well worth it. In this case, it allows one to lash items and provides unparalled flexibity. It allows you to sail with more confidence i.e. your shackles won’t bust and wreck your day. When I used to work in theatre production, we all knew that the theatre, in general, was held together by masking tape. IMHO, a sailboat (while not held together by Dyneema) can be vastly improved by the use of this this very strong and supple line in so many applications.
Using Dyneema allows you to GRIN !!! (Full disclosure - While I wish that I held some sort of financial interest in the “Dyneema Company”, sadly, I don’t.)
All of that said … I still get a BIG kick out of the differences in opinions and the sheer volume of good info and experience that shows up in these discussions. Brilliant.
When I got my boat a couple of year ago I found an eyebolt and nut plus shackle. The aluminum casting was pretty corroded to I removed everything and installed what’s in the pictures. Currently it’s two parts, one lashing to the clew and one bridle, I’ve been thinking that in the next iteration I might simplify it to just a single line that does both jobs. The bridle is essentially a loop with a “lover’s” knot.
There are many ways to do this and you certainly have found a perfect one. It’s all lashed, one way or the other, and the force is transmitted to the back of casting, not just that hole.
When I bought Sandpiper she had already had stainless steel mounting hardware installed on both ends of the boom so wear is not an issue for me. The clew was fastened with a twisted shackle which failed on my sea trial sail …… but I bought her anyway.
I now have a Dyneema lashing consisting of several loops secured by multiple half hitches and covered with tape to reduce sun exposure. I like the ability to change the length to suit bimini clearance or sail flatness.
