Boom shives

[Tomrob]

Hi, I’m replacing the shives on my Pearson 31 boom. I’ll be drilling out the rivets on each end and seeing what my next step will be. So does anyone have any experience suggestions or warnings?
I’m thinking there is a shive in the center of the boom. Does this slide out? There is no access hole in center of boom.
The reason I’m replacing the shives is because the reefing lines would jamb up this past summer.
Thanks Tom

[psk125]

Reefing lines should not jam up inside the boom because of a sheave there; there would be no reason for a sheave in the boom for reefing lines. The outhaul might lead through a tackle inside the boom, and the reefing lines might get tangled with that or with each other. Are the sheaves broken? You may simply need to re-lead the lines so they’re not fouled. If you drill out the rivets, watch out for the pins that the sheaves turn on. They may have bearings and be expensive to replace if lost.

[Cheechako]

I'm not sure the setup. Some booms have sheaves in the aft end for internal clew reefing lines and then internal sheaves at the forward end also. Plus jammers sometimes. Is that what you have? If so they should have one big pin... not rivets...? Or do you mean the rivets holding the end fittings in the boom?
More info...

[Tomrob]

Yes rivets holding the end fittings

[Cheechako]

OK. Well be prepared to find some corrosion between the fittings and the boom itself. Hopefully it wont be too bad. You also may have a tough time getting the end fittings out due to corrosion.
-I would clean it all up, make sure the sheaves turn well.
-You may never get the pins holding the sheaves out, hard to say.
-When re riveting, coat all fasteners with lanolin or another corrosion barrier.
-If the holes are too buggered up you can redrill bigger and rivet or tap threads and use machine screws.

Good luck!

[Tomrob]

Hi, I tried to attach a picture, not sure if you can open?
I guess my question is do I need to remove the tack and clew ends of the boom in order to replace the shives?

[psk125]

Are the sheaves not turning, or are the lines jamming? If the sheaves are turning, leave them alone and fix the misled lines. It looks like you have an Isomat mast with the “old style” fittings, according to Rig-Rite. If you do need to take the sheaves out, this guy seems to have worked out how to go about it:https://www.foghornlullaby.com/2019/...king-it-apart/

[Tomrob]

Thank you, exactly what I was looking for. Great link too.

[Frankly]

The picture is a very common Isomat boom end and cast fitting (condition looks really good). You can drill out the pop rivets to get good access or try to look through the lower hole.


A common set up was to have a shuttle block in the reefing line (never could understand why). Dig around you can find a diagram. Those shuttle blocks never turned freely so a number of years back, I just discarded mine and changed to single line reefing setup. Had to replace the fwd axel with a thru bolt to handle upward loads but really works better IMO.


Frankly