Isomat boom refurb

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walterg
Posts: 67
Joined: Tue Aug 30, 2016 6:48 am
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Isomat boom refurb

Post by walterg »

In anticipation of new sails this year I decided to go over my Isomat boom to clean up a few things:

- The outhaul did not work as smoothly as I would like
- Reefing lines (2 although I have 3 reef points on the old sail) didn't operate smoothly when raising and lowering the main
- Several of the machine head screws that attached the aluminum end caps to the boom were stripped and missing
- The sheaves looked old and I was considering replacing them

The first thing I found after I pulled the end caps off was.....nuts. Seems like some critter had made a home in my boom in the past and stored at least a dozen nuts in there. I vacuumed those out....hopefully that will be one less mysterious noise to keep me up at night.

The sheaves, which ride on a SS shaft pressed into the aluminum end caps, seemed to be in good enough shape to last a few more years. Everything for the Isomat boom looks like it is available from http://www.rigrite.com; but in my case I just gave them a good cleaning and McLube'd them. Likewise with the shuttle cars for the reefing lines.

The blocks for the outhaul were in good shape but instead of using a becket for the end of the outhaul line, the block used a stamped shackle that was too small and "pinched" the sheave so it didn't roll freely. I replaced that with a Ronstan block and since it was too easy to buy a new fiddle block at the same time, I replaced them both. Original blocks on the top, new ones below:
outhaul_2.jpg
outhaul_2.jpg (34.18 KiB) Viewed 2237 times
After that I straightened out the outhaul and reefing lines so there were no criss-crosses inside the boom. Lastly I drilled out the stripped threads in the end caps and installed some Heli-Coil inserts.
Walter Gotham
Salem MA USA
'87 Freedom 28-Mull #33 "Nova Vita"

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RadioZephyr
Posts: 259
Joined: Mon Jun 27, 2016 10:04 am
Location: Boston, MA

Re: Isomat boom refurb

Post by RadioZephyr »

Nice! I have a couple of modifications that I made to my Isomat boom that folks might find helpful:

1. Plug the hole where animals can get in. When I first took off the end caps on my boom, I discovered a bird's nest inside. I started looking for a solution, and was told to just put a sponge in the hole in the aft the end cap whenever I would be away from the boat. I considered it, but then I found that Rig Rite carries a plug that perfectly fits the opening (part #: NB32-2EP). I remember it was a bit pricy for what it is ($35 I think?), but I like a nice clean looking solution.
"Bird Nest Buster"
"Bird Nest Buster"
IMG_2137.jpeg (155.37 KiB) Viewed 2207 times
2. Add a pad eye for a permanently rigged preventer pennant. While I had the caps off, I decided to install a small pad eye in the channel on the underside of the boom at the aft end for a preventer. I think I had to grind a little bit off the side of the pad eye to make it fit in the channel, but after that it was simple enough to drill the holes, and then fasten it from the top down with truss head screws and nylock nuts on the exterior. I also added a new cleat to the underside of the boom, just forward of the one for the lazy jacks. Once it was all back together, I tied a piece of 9mm dyneema to the pad eye (I've since replaced the knot with a proper splice), and ran it forward to the new cleat. Now, whenever I need a preventer, I can just take it off the cleat and tie it to the bow cleat. Of course, the ideal way to do it is to run two lines forward to cleats on either side of the boom, so that you can just take whichever one is upwind. However, I didn't quite have the real estate for it, and I thought it might look a bit busy. It's not too much trouble to lead it around the main sheet when necessary, especially if you remember to do it beforehand!
Pad eye with preventer pennant attached.
Pad eye with preventer pennant attached.
IMG_3053 (1).jpeg (152.93 KiB) Viewed 2207 times
Josh
Sunset Spy
F38, Hull #152
Boston, MA

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