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If you have just acquired an old Laser/ILCA dinghy, this was the method of attaching the aft mainsheet block to the Laser/ILCA Boom...

Back in the factory, this was quick, low cost way to attach most of the Lasers/ILCA fittings.

However, pop rivets are renowned for 'stretching' and in areas of high load, such as the mainsheet block, the saddles holding the mainsheet blocks can unexpectedly fail (or rather the pop rivets).

In addition due to the different metals and the presence of salt water, corrosion can occur in the area of the fittings and the attachment points. Below are typical photos of a Laser/ILCA boom fitting showing what can happen:

This short article describes the procedure for bolting, namely the outhaul, and the two mainsheet block boom Laser/ILCA fittings. Suggest using 5mm diameter bolts as the existing holes (3/16' - 4.8mm) would have enlarged or corroded. 

Parts required:

Optional parts:

A replacement Laser/ILCA plastic boom plug: Holt HT91620 Replacement Upper Mast Top/Boom End Plug for Laser/Pico

Replacement Laser/ILCA mainsheet plastic blocks: ALLEN A.378 38MM SINGLE WITH BECKET - LASER/PICO REAR BOOM BLOCK



Tools required:

  • A flat bladed screw driver.
  • Drill and drill bit (use a 5mm diameter bit).
  • Centre punch.
  • Engineers hammer.
  • A length of Rooster whipping twine, and a split pin.
  • Spanner & mole wrench.
  • Hacksaw.
  • Pair of long nose pliers.


Drill out the 4 no. existing mainsheet pop rivets (see the related blog article below if you need help with that process) that attach the saddles to the boom. (Note on older Laser you may have a middle shaddle fitting, the one that 'holds' the mainsheet up between the two other blocks).

Punch out the rivets into the boom.

Now drill out the outhaul saddle rivets, and again punch out the rivet 'cores'.

Note: The end outhaul rivet is used to secure the plastic end of the boom. Remove the plastic end plug fitting using a large flat bladed screwdriver and a hammer then gently ease off all the way around.

Once the old fittings have been removed, the next step is to get the bolts in place for the fittings.

Attach a small split pin to the end of the whipping twine. Starting at the middle boom end fitting, insert the pin down one of the existing holes and allow it to drop out of the boom end.

Remove the split pin and then tie on the first 5mm bolt to the twine and pull back up the boom and through the first hole.

Now using a piece of tape hold the bolt in place as it protrudes through the existing hole. Repeat for the remaining hole.

The below photo shows the fitting removed, showing the 2 no. 4.8mm existing holes. Fit a replacement Allen Laser mainsheet blocks and end boom plug if required).

Remove the tape, and attach the existing saddle complete with washer, the mainsheet block and finally the loc nuts.

Now using as pair of 'mole grips' hold the excess bolt thread protruding out and tighten the nut up, then finish off with a suitable spanner.

Using a hacksaw remove the excess tread back to the top of the nut and file smooth as required.

Repeat for the end mainsheet block, however this time, the twine will not be required as you can hold the bolt in the hole via a pair of long nose pliers

The 3/16" (4.8mm) holes that held the existing saddle fitting.

Cut out with you hacksaw a suitable 'notch' in end of the plastic boom plug (to slot around fixings) and push/tap into end of the boom. (No other fixing of the end plastic plug is needed -  is quite a tight fit...)

Job done...

Update June 2022

Below are photos courtesy of Rooster customer Tom Flintham who has bolted up his Laser boom and used Hex Allen headed bolts.

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