Selden sheave box specifications? Alternatives?

[JumbleDuck]

As it looks as if I am going to be at home for a couple of months, I may as well amuse myself by getting the Hunter 490 back into commission, The only significant work is on the keel lifting system: a winch on the front of the mast compression post pulls a 4mm wire rope which runs up the post from the winch, into a sheave box, through the post, through another sheave box and down to the keel.

The original design used Holt Allen HA5 sheave boxes or equivalent, but they are grossly insufficient for the load. As the keel weighs 250kg the total diagonal load on each sheave is around 350kg, which bends the axles. I have been looking for substitutes and see some promising things in the Seldèn dinghy range, particularly the High Load Jib Box 505-095-02m which looks like this

Unfortunately, I can't find proper specifications for this anywhere: I need dimensions and SWL. Can anyone help, or suggest an alternative? The Seldèn catalogue says "See p46 for sheave dimensions" but p46 is actually details of a jib furler.

 

[lw395]

350kg would be 'very' high load for a dinghy jib.
A lot of the more powerful dinghies have 2:1 jib halyards.

The 'axle' on a lot of sheave boxes is a length of ss tube. Could you replace that with solid bar?

 

[JumbleDuck]

350kg would be 'very' high load for a dinghy jib.
A lot of the more powerful dinghies have 2:1 jib halyards.

The 'axle' on a lot of sheave boxes is a length of ss tube. Could you replace that with solid bar?

Yes, it's a rather optimistic piece of design, and increasing the size of the sheave boxes means cutting away the compression post and weakening it. If that "high load" sheave box isn't up to it then others may be, if modified (solid axles as you suggest and/or metal sheaves) but I need the dimensions to start the ball rolling and I just can't find them.

 

[BabaYaga]

You might find something more useful in the keel boat range, see p. 22 of this:
https://www.seldenmast.com/files/1374069425/595-950-E.pdf

 

[JumbleDuck]

You might find something more useful in the keel boat range, see p. 22 of this:
https://www.seldenmast.com/files/1374069425/595-950-E.pdf

Thanks - some ofr the ones there look possible, but it's irritatingly short on specs. I shall investigate.

Today I had a nice chat with Duncan at SRS, my local Seldèn agents. He had nothing to suit, but suggested a Harken 302 which looks like the thing and is rated to 475kg .Might need a little bit of compression post reinforcement, though.