Sunfish top mast cap replacement installation question

dougd

New Member
I was checking the rigging and while lowering the sail the mast cap pulled right out of the mast! It was missing a pin, and had a very loose fit. I ordered the replacement but not sure about the correct way to attach it. The new cap does not have pre-drilled holes. The mast has two sets of drilled holes that are slightly larger than the pins, suggesting this has been repaired/replaced before. Do these pins just get friction fit into a hole drilled in the cap? What would prevent this from pulling loose again? I appreciate any advice!

cap.jpg
 
For a good install, use some silicon sealant and two 1/8 in dia. pop rivets on either side of the mast head. I have never trusted the little stainless pins used to secure these caps. Be sure to silicon fill the hollow ends of the pop rivets to prevent leaking.

Alan Glos
Cazenovia, NY
 
Usually (!) the mast cap fits pretty tightly. One can also use a sealant to prevent the issue you encountered.
I've had three different mast caps on the 7 Sunfish I've bought. A new replacement was too big to fit. :oops: One had ribs (6? or 8?) and pins. One was a perfect fit with pins. I last used Shoo Goo and the pins.

If you're missing the stainless pins, you can cut replacement pins from the mandrels (the "nail" part) of pop-rivets.
 
"Do these pins just get friction fit into a hole drilled in the cap? What would prevent this from pulling loose again?"

Yes, the plastic cap is what holds the pin, not the mast. We drill a pilot hole one drill bit size smaller than the pin and tap the pin in with a hammer. Needle nose pliers help hold the pin until it gets started.

In the past if we had a saltwater boat with corrosion around the old pin hole on the mast, we drilled a fresh hole in the mast. But now that we are more versed in rivets, we'd follow Alan's advice.

IMG_2523.jpg


Can't remember where I got these photos, but the bottom of the mast must have a cap as well, to prevent damage to the mast step and keel. I applaud the vigor that must have been applied to do this much sailing and subsequent damage, but not the oversight on installing a mast base cap.

Mast tube damage.jpg


Mast base damage.jpg
 
Among other manufacturers, Hobie makes a Teflon disk to drop down their mast steps. In the event of a base-cap loss, a plastic cap from a jar can be trimmed to fit.
 
"Do these pins just get friction fit into a hole drilled in the cap? What would prevent this from pulling loose again?"

Yes, the plastic cap is what holds the pin, not the mast. We drill a pilot hole one drill bit size smaller than the pin and tap the pin in with a hammer. Needle nose pliers help hold the pin until it gets started.

In the past if we had a saltwater boat with corrosion around the old pin hole on the mast, we drilled a fresh hole in the mast. But now that we are more versed in rivets, we'd follow Alan's advice.

View attachment 53169

Can't remember where I got these photos, but the bottom of the mast must have a cap as well, to prevent damage to the mast step and keel. I applaud the vigor that must have been applied to do this much sailing and subsequent damage, but not the oversight on installing a mast base cap.

View attachment 53170

View attachment 53171

This damage can also occur if the boat is moored with the rig up. Wave action causes the mast to scrub the bottom of the pocket.

Definitely keep the bottom cap in good service but I like the idea of a sacrificial plastic disk in the bottom of the hole as well.
 

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