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Mast length modified

Rob Hair

Active Member
I'm new to Lasers, although I've sailed for many years and got my start sailing in a similar sized boat - OK Dinghy.

I bought a used boat (1976) with sail number 555. I don't think the sail is original, because its in very good condition, so I don't know if that's really the right sail number and I can't find a hull number on the transom.

I rigged the boat completely last week and all seemed fine except that the tack (the hole for the Cunningham) seemed too low. The Cunningham hole came down as far as the pin for the boom, making it impossible to tension the luff of the sail. It appeared as though the mast was about 4 inches short (or the sail 4 inches long). After looking up the Laser class rules it became obvious that everything was the right length, but the plastic collar on the upper mast section that mates with the lower mast section had been moved by some past owner, making the upper mast section sit lower in the lower mast section by about 4 inches. The original hole for the rivet that fixes the collar is visible and I can even hear the part of the original (drilled out) rivet rolling around in the upper mast section.


Its a simple matter for me to move the plastic collar back to its original place (I have SS rivets and setting tool) and that's what I intend to do, but I wanted to see if anyone may know of some reason that I may want to leave it as it is. I can only guess that at some time in this boat's past someone used a slightly shorter sail.

Any idea why someone would have modified the mast in this way? It doesn't seem like it was shortened enough to fit a Radial or M rig.

Rob
 

49208

Tentmaker
May have been done in an attempt to stave off the inevitable mast break at the collar rivet. Sadly, it's the wrong way to go about it, as not only is the mast to short for the luff, but also falls outside of class rules (if you go to race)

The right way it to end for end the section (top end becomes the new bottom, and collar moved) If you discover that the section has already been end for ended, you can move the collar back down to the original location and re-rivet -or- get a new top section
 

Rob Hair

Active Member
Do the upper sections typically bend or crack? I didn't notice either, but I didn't check carefully either. I did note that when both pieces were put together the mast was straight. I'll check for damage around the old rivet hole area. Thanks!
 

Muzza

Member
Bend - yes. You can straighten a minor bend yourself.

Crack - yes around the rivet holes. The idea is to face the rivet holes aft, so that as the mast bends under sail, the rivet holes are compressed rather than stretched.
 

gouvernail

Super Opinionated and Always Correct
Bend - yes. You can straighten a minor bend yourself.

Crack - yes around the rivet holes. The idea is to face the rivet holes TO THE SIDE, so that as the mast bends under sail, the rivet holes are NEITHER compressed NOR stretched.
FIXED

When you rig, sight down the mast and if it appears to be bent place the inside of that bend to the front so it will self straighten.
Otherwise, simply try to alternate each time you rig. rivet left..rivet right..rivet left...

facing the rivet aft GUARANTEES your top section will eventually bend aft and as you CANNOT sail with the rivet in the front, the bent mast becomes useless.
 

laserxd

Member
The rivets on my mast collar broke over the summer and it temporarily had this problem, I did an end over end seems how the original holes might have fatigued causing the break. I wouldn't suggest re-using rivet holes on the mast, there is a good amount of force applied to the mast when sheeted in block to block and with vang on more than block to block, you don't want to risk it.
 
It may be that the rivet has corroded/sheared and the collar has slipped up the topmast, with the rivet head is still stuck in the plastic collar. That's what happened to me, and I bought a new sail before I found out!!
 

Rob Hair

Active Member
Good point and one that logically explains what could have happened. The boat is "up north" - I'll check it next time I'm at the cottage. Thanks!
 

Rob Hair

Active Member
It may be that the rivet has corroded/sheared and the collar has slipped up the topmast, with the rivet head is still stuck in the plastic collar. That's what happened to me, and I bought a new sail before I found out!!
I just got back up north (Port Austin at the tip of Michigan's Thumb) where I keep the boat and discovered that's exactly what happened to mine also. It seems my boat's previous owner was no mechanic - he tried to keep the collar from sliding further by wrapping the upper mast with tape.

The rivet hole looked fine and I installed a new rivet with the collar in its original position.

Thanks to all for the help.
 

Timb

New Member
About that rivet. SS is the wrong materal as it will react to the aluminum mast.
Monel metal is the type of rivet to use
Tim
 

torrid

Just sailing
About that rivet. SS is the wrong materal as it will react to the aluminum mast.
Monel metal is the type of rivet to use
Tim
I believe most of the spar fittings use SS rivets, especially the load bearing ones (like the gooseneck). I think the factory applies some sort of treatment to prefent corrosion.
 
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