The design of new modern dead eyes for synthetics rigging. To be used on multihull rotating wing mast.

The designAt first, the idea comes from the old wooden dead eyes used on square rigged sailboat.If the part works when they use only rope rigging, the same kind of part should works on the new high tech synthetic line.So, I scaled down and adapted the old dead eyes to the new line diameter.I tried to make the smallest and lightest part possible. There were two dimensional constrains : the minimum radius around the part and the minimum radius for the lashing. For the ease of tightening the lashing, I needed to have the maximum number of lines.I finished with 4 hole staged in a 2 inches wide dead eyes. (over this number there was not enough material left)

At this stage of the design, I just made a basic static analysis showing that the part which was the most solicited was the part pined on the chain plate, and on the mast tang. The middle deadeye is far less solicited.I optimized the part by finite element analysis and I validated my work with a destructive testing on a testing machine (the result you see on the picture).

Note:the top part you see n the drawing is replaced by this one (one on each side)

The finite element analysis

I made different analysis on the different parts.On those analysis we could see the same results than in the static analysis

The destructive testingI tested the parts on a test setup ressembling as much as possible to the setup we could have on the boatAt first, I wasn’t thinking the part, at this stage of design could resist more than 10000 lbsf in traction, so I use a 1/4″ steel cable with 3 cable clips.

The part didn’t show any deformation and the clips slip. On the second test I added one more clip and this time the cable broke at a value over the fist one (see the graph)At the 3rd attempt, I have taken a 3/8 inch steel cable with 2 cable clips and this time again the clips slipped.On the fourth attempt, with one more clip, the bottom part sheared in the clevis pin hole (see the picture)That give me over 14000Lbs for this part.

The resulting partThat give me a better way to attach synthetic line to a mast and very light (The weight of one part is about 0.25 lbs), attractive and compact parts

The future

After the first prototype, I made a set of dead eyes (without the top) for Mr. Leneman. They where a lot nicer: CNC machined (the only way to go for the groove and the half ellipse lashing track), polished and anodized.