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FAQ: Backstay Tensioners


Has anyone installed a backstay tensioner on a C34? We're considering it, and I'd like to hear some informed opinions. 

Please Note:  Forestay and backstay too short
There is a problem with the rigging on our C34 MKII. The turnbuckle on the furler has about three threads showing on each end and the forestay is tight. The backstay has three shackles in series on each side and the turnbuckles are barely engaged. Our hull number is 1300.
Trident, 1996, kensail@swbell.net, Kenneth Morton

Yup, I installed one. It consisted of one of those tensioner plate assemblies, the kind with 5 sheaves between two stainless steel plates. The split backstay rides on the inside of the upper 4 sheaves, and the lowest (fifth) sheave is used for the tensioning tackle. The tensioning tackle was a 3:1 block/tackle arrangement, pulling on a 6 x 19 wire rope attached via nicropressed sleeves and thimbles. To provide for attachments points at the bottom end of the block and tackle, and for the far end of the wire rope, I replaced the clevis pins at the bottoms of the backstay with large D shackles, whose pins were equal to the diameter of the original clevis pins. Well, they weren't precisely 'equal', I had to slightly drill out the backstay fittings to clear the pins, but only a little bit. The block/tackle and far end of the wire rope attached to the D shackles with snap shackles, so I could pull the whole thing off quickly in case I needed an emergency block & tackle somewhere. It worked well, although it took a few shots of silicone spray on the sheaves to keep it from squeaking loudly when adjusted (Norm Bernstein).  

The back stay tensioner mentioned by Norm Bernstein is better suited for the 1991 and later C-34s.  Catalina made the split in the back stay much higher when they introduced the walk through transom.  On the earlier C-34s (without the walk through transom) the tensioner plate assembly with the five sheaves tends to pull the lower split back stay together creating a head bumping hazard when using the boarding ladder.       A number of us with the lower back stay split made our own using three wire blocks, 7 x 19 wire rope and a 4:1 block/tackle with a cam cleat.   This keeps the adjuster assembly as high as possible when not in use.  We attached tangs drilled out on one end to fit the clevis pins already securing the bottom of the back stay.  There was sufficient depth to accept the tangs with washers and cotter rings.   The block/tackle on one end and the wire rope easily attached to the tangs with quick links (Ron Hill, C34 National Association Technical Editor).

What are the recommended tensionings for the backstay adjuster? 

According to a May, 1990 article in Mainsheet, you should consider the following tensionings: 

Apparent Wind Backstay Pressure Heel (degrees) Main Genoa Trim at spreader
0-12 kt light 5-12 full 155% 6-8"
12-18 kt moderate 12-18 full 155% 6-10"
18-22 kt mod-heavy 15-20 reef 135% 8-12"
22-26 kt heavy 15-20 reef 120% 10-18"
26-30 kt heavy 15-20 reef 95%  -


Important: The opinions expressed here are those of the individual contributors to this page, and not those of the Catalina 34 National Association or Catalina Yachts, Inc. Additionally, this material has not been reviewed by Catalina Yachts, Inc. for technical accuracy. This page's maintainer cannot guarantee the accuracy of this information or the desirability of suggested modifications or upgrades. Please obtain assistance from a competent marine mechanic or boatyard prior to making any significant modifications to your vessel.   


Last modified by Phil Imhof, Wednesday, August 11, 2004 . Copyright 2001 by Catalina 34 International Association.  All rights reserved.