A comparison between Re-building a wooden block with a standard Harken Ball Bearing Sheave and as an alternative fitting a custom fabricated Harken sheave into an existing block:
Over the past three years we have restored many traditional blocks at Baltic Boat Works – some have come in for a complete re-built while others just needed an upgrade of the inner workings, so here is a little bit of comparative background information:
Usually the condition of a block when it comes to us dictates the direction we are taking – remember that a lot of the wooden blocks we see on classic yachts are in fact old (…”classic”), very often we are looking at Merriman Bros. blocks which are more than 50 years old and have seen a lot of service in harsh conditions. Often these old blocks need more than just a few coats of varnish, so we got into re-building these blocks; and as we are doing this we often slightly alter some dimensions and make everything fit to a standard Harken Ball Bearing sheave.
The majority of the cost when re-building a block is spent on labor and most of that on building the “wooden body” – even though this body has essentially nothing to do with managing the load that the block will see in service. All the load is entered thru the sheave, from there onto the axle and from the axle to the strap – the wooden body sees no load at all and is only there to cover the sheaves, sometimes guide the line and protect the environment.
Here are a few pictures from rebuilding blocks:
As an alternative to re-building the block completely, especially when we receive blocks which are in good working order with a solid wooden body and solid strapping, we like to take a different route:
All such a block needs is a modern ball bearing sheave with a high load capacity. Very often however the “off the shelve” ball bearings do not fit the existing block perfectly and in these cases we could either rebuilt a block as described above or design and order a custom ball bearing sheave made to the dimensions of the existing block. We are working with Harken which offers the service of building custom sheaves, it usually takes eight weeks for turn around, the custom sheaves are mechanically based on existing designs and therefore utilize proven and tested ball bearing construction.
The prices for custom sheaves vary greatly and mostly depend on
a. material used for the race (anodized AL vs. bronze)
b. size (OD & width)
c. number of sheaves ordered to one design (spreading design & CNC set-up cost)
The installation of a custom made sheave into an existing block however is pretty straight forward and usually only includes some cleaning of the block and axle, new fasteners for the axle plates and very minor adaptions of the wooden cheeks (if at all).
The high cost of the custom sheave is in most cases more than off-set by the “saving” on labor one would have to spend to re-built a block.
Pictures of a block good for custom sheave & Custom Sheave with Bronze Race (LUCIE):
