Some background information on the mast and boom on a CS34 sailboat.

The mast and boom on the CS34 was made by Isomat Inc. You will find the same mast on many different brands of boats including Bayfield, Beneteau, Pearson, … And the exact same mast and boom is used on the CS36 Traditional and CS36 Merlin1. Everyone I spoke with has told me something along the lines of “that’s one solid mast, you’ll never have a problem with it”.

There is a great source of information on Rig-Rite’s website with all of the parts for the CS34 rigging.

On our boat, everything is solid and working well. However, I took apart the boom to clean out the auto reef system and made some interesting discoveries. The following came from RigRite, and is very useful to understand the system inside the boom.

Isomat_AutoReef.html_txt_ISOMAT AUTO REEF SYSTEM

Mast and Rigging

The following diagrams came from the CS36 Traditional manual. I believe the CS34 is very similar. Although CS36t is keel stepped and CS34 is deck stepped.

Gooseneck and spreader


Mast Sling Location

Options for replacement parts

  1. – has lots of great info on their site but may not have stock of all the parts.
  2. Holland Marine – I’ve heard of them from the CSOA forum and several other CS owners. They have acquired a lot of the equipment and stock from CS. CSOA forum members have mentioned Peter as a good resource there.
  3. EB Spars – run by Evert Bastet in Hudson, Quebec. Liam Dixon mentioned in the CSOA forum that Evert provided many of the masts used by CS Yachts.
  4. SparCraft – It may be another option for finding replacement parts for your boat. I found some info online that they acquired the US Isomat company.

Isomat was based out of France. I haven’t been able to find much information about it. I did find the following government document saying a US location was acquired by Charleston Spar, Inc. sometime in 1998. This probably was just a US distributor.

Charleston Spar EPA letter snippet


1 I still need to confirm that it is the exact same NG-60 mast as the CS36. The CS34 is deck stepped and the CS36M and CS36T are keel stepped.