How to calculate load on bow eye (to size new one)?

BrentB":1k1sb1wl said:
Having a better part is ok but proper installation is important too.. It seems to me that one limitation is the hull thickness in area. Is it re inforced with fiberglass mat or just buildup of extra epoxy ? With a strong pull, the eye could pull out like a tooth.

I will definitely be reinforcing the bow in this area. In fact, this is one (more) reason for a new bow eye - longer legs to be able to go through some backing. Not sure exactly how I'm going to do it yet, but there are numerous ways that can work well, and I will figure that out once I'm "in there."

At one time I was involved in a project to install a bow towing/anchor eye on a largish power boat (ironic, given this thread :D). It was interesting following the loads along (because as you say, it's no good anchoring a strong piece to a weak substructure) and visualizing how to make it happen. A naval architect/engineer was involved, but we also had to figure out how this could work in the real world (installation access and procedure, etc.). In the end it turned out to be a combination of a tang (picture a chainplate, only parallel to the long axis of the boat), which carried most of the load to a reinforced bulkhead, and a plate much like shown above only larger (for looks, to have something to bed, and to carry some of the load to the skin).

Of course our small boats have smaller forces, but still everything has to "match up."

Back to the backing: I'll have to see how it looks once I'm in there again, but I'll probably do some combination of a few layers of biaxial cloth in the area, plus a fitted/epoxied backing block. Included will be making a flat/parallel surface on the after side for the washers/nuts to land on.
 
Back
Top