SF mast plugs

L

LAuman

Member
We have 3 relatively new S'fish masts (2003 and 2004 boats) and the bottom plugs are ripping out. One was lost, one was found in the bottom of the mast tube. They came out, leaving the single rivet in the mast, but with the rivet hole torn out of the plug. A ring of transparent silicone (with very poor adhesion) remains in the mast.
Incidentally, the oldest mast has a cork plug a few inches up into the tube. The newer one doesn't.
Didn't want to cut the bottom out of the hull mast tube. Put a brand-new mast in yesterday, and, after about 2 1/2 hours of sailing, the bottom plug is out about 3/32" on the side away from the single rivet. It appears to be on its way out, pivoting on the rivet.
Is this a common experience? What do folks do about it?
 
LAuman,

Not common in my experience. You are lifting the mast completely out of the mast step before tilting it? If not you could be catching the cap on the edge of the step and pulling it off. Don't cut the mast tube, just clean up the area where the plug makes contact on the inside. Reinforce the cap (ISAC Rule 3.5.8). Pull the old pin out from the inside using pliers. Place the mast cap back inplace (with a little 3M 4200 or 5200), with the old hole rotated away from the old pin. Install new pins (P/N 79513, about $6 for pkg of 10) in new holes on opposite sides (180 degrees apart) and you should no longer have problems. You can also use aluminum/aluminum pop rivets (1/8"D x 1/4"L) in place of the pins, they work, but look ugly. You may wrap the bottom of the mast (just above the cap) and where the mast contacts the top of the step (ISCA rule 3.5.7) with white electric tape (or other tapes mentioned in previous posts, do a search) until the mast is snug but turns/removes easily. Also check for a sharp edge in the mast step that could be catching the cap (sand it down if it is sharp). The cork is nothing to worry about, it can be removed with out problems (ISCA Rule 3.5.10). The rule references apply only if you are interested in racing. Good Luck
 
Thanks for the reply! :) The mast tube I referred to is the one in the hull connecting the deck to the outer hull. My concern with the mast that had completely lost the bottom plug was that the sharp end of the aluminum mast would cut into the fiberglass. None of these 3 masts have a "pin"; all 3 have (or had) a single pop rivet and the non-adhering silicone to secure the plug. . . and none of them held or are holding. They are all failing.
When we remove the masts, we lift them straight up. The fiberglass is smooth. There is no resistance or other evidence that we're catching on anything.
We use a clam cleat on the mast (ISCA 3.5.9) for the halyard and sometimes a "pseudo-vang" loop from the halyard fairlead on the deck over the gooseneck.
We ARE new to S'fish from sailing other boats, and we appreciate help from folks with experience. It is certainly weird that ALL of our masts have this problem. . . doubly so if no-one else does.
 
LAuman,

Sounds like you are doing things right. Your mast tube (deck to hull) is what I call the mast step. Vanguard may be cutting corners on installing the caps, using only 1 pop rivet. Both masts of mine (a '69 & "85) have two pins for each cap and I have not had any problems. The pins I refered to (P/N 79513) are small tapered pins with grooves (about 1/16" in diameter and 1/4" long) that are driven in a drilled hole slightly smaller than the larger end until it is flush with the outer surface of the mast and into the cup. The pop rivets (aluminum rivet/aluminum shaft(mandrel)) do the same job and may be easier to get and install. Just carefully drill the old rivets out and rotate the cap when re-installing. Minimum rivets to install would be 2 at 180 drgrees from each other. You may want to install 3 or 4. I always re-install the caps with 3M 4200 or 5200 Marine Adhesive Sealant and let it sit up for a week or more before using any item assembled with the sealer. The stuff is messy :( , so wear gloves, wipe up any excess (paper towels) and let sit. With no other penetrations and both ends and mast cleat area sealed with the sealant, your mast should be water tight. Like I suggested before, use some white (black gets yuckky :p ) electrical tape around the base and deck area and you should be good to go. If you have a groove in the bottom of the mast step from the mast, the common fix is to pour a little epoxy (about a 1/4") into the bottom and let it set up. While you have the rivet gun out (or pins), you may want to add some rivets/pins to the top cap also.
 
Another possibility is that the bottom of the mast step or the cap is so rough that friction is turning the mast cap causing it to come loose as the mast rotates back and fort while sailing. It's a long shot because I can't imagine why the step or cap would be that rough.

Fred
 
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