sunfish mast upgrades

this spring (and sadly now dragging well into the summer) I have spent some time working on repairs and upgrades to my Sunfish sailboat, and a little bit as well for the Super Porpoise sailboat (slowly trying to cross things off my parts list). here is a picture of the old system on my Sunfish (similar set up for the Super Porpoise):

last fall, I had bought a new mast lower base cap and mast top cap with the integrated fairlead from Torresen Marine, but I hadn’t had a chance to install them yet.  I went ahead and ordered another set of mast caps from The Sailboat Garage to upgrade my Super Porpoise mast at the same time.  I also order 2 horn cleats (a much cheaper nylon cleat can be found via Intensity Sails) to install on the mast – this new horn cleat will allow me to tie the halyard tight after I’ve raised the sail, and reduce the uplift forces on the fairlead on the Sunfish deck.  you still need to run the halyard through the fairlead, and tie it off to the horn cleat on the deck, though, as this will prevent the whole rig from slipping out if you capsize and “turtle” your boat.  I also ordered a couple tubes of 3M 4200 marine sealant from Intensity Sails, and bought a rivet gun on sale for $3 at Harbor Freight.

so here’s my installation gear (the table saw is not required… it just served as my workshop “table”):

I’m not sure if it was because of the age of my Sunfish, or if the mast has experienced some damage at the base after years of use (and abuse?), but it did not come with a mast base cap, and the new one I bought would not fit at all.  it almost seemed like maybe the base was necked down just slightly at the base causing the too tight fit.  I spent several random nights using a utility knife to slowly whittle small pieces of plastic off around the perimeter of the base cap, occasionally using sandpaper as well to smooth it out some.  finally, on the last day, I dug out a rough wood rasp, and that seemed to shave off pieces a little more easily and I could shape it a little better.  I also used a curved metal rasp to smooth out the inside of the mast base.  after all of that, I was finally able to get the mast base cap into the Sunfish mast.  the mast top cap also fit very snugly at the Sunfish mast, but wasn’t nearly as difficult to get it to fit.  thankfully, both of the caps fit quite easily into the Super Porpoise mast, without any shaping or sanding required. you’ll notice in the picture below that the Sunfish mast (on the left) still has the cork plug in it – these used to be factory installed to help with flotation (I think), but have since been discontinued as an option.  I just left it in, but did pull some that was in worse condition out of the bottom of the Super Porpoise mast.

the mast caps came with varying sizes of pop rivets, and it seemed only 1 pop rivet per cap.  the rivet gun I bought came with (4) sizes of (25) rivets each, so I opted to install the mast lower base caps with just the (1) supplied rivet each, but then used (2) of my own rivets per cap for the upper caps.  I smeared some 3M 4200 marine sealant around each of the caps prior to installing them, as well as a small dab of sealant on each pop rivet.

here are the mast lower base caps installed:

and here are the mast top caps with fairlead (the masts now have extra holes from the through-bolts used previously – I might try to fill the holes with JB Weld or some other epoxy to seal up the mast):

for the mast cleats, I installed them just below the limit allowed by the Sunfish Class (max height for the cleat is 48″ from the base of the mast).  I used the blue masking tape to mark off the 48″ limit.  I used the 3M 4200 sealant behind the cleat, and fastened it on with #10 stainless steel sheet metal screws – I had to pre-drill the mast with small pilot holes.

so, other than the mast caps not fitting nicely to start out with, this should normally be an easy repair, is relatively inexpensive, should last me for quite a long time, and will be a definite upgrade.  additionally, by adding the horn cleat, you reduce the uplift force on the deck, which should help.  also, since my mast didn’t have a lower base cap, my mast well is probably going to be more likely to have wear spots and potentially could have leaks as a results of the bare pipe wall applying load instead of the nice flat surface that the base cap provides.


13 Responses to “sunfish mast upgrades”

  1. 1 Peter July 8, 2011 at 8:56 am

    I have to do this exact same repair now. I was tightening the lock nut on my eye-bolt that holds the mast cap in place (old style mast cap), and the eye-bolt broke in half.



    • 2 my2fish July 8, 2011 at 11:54 am

      sunfish65, hope the repair goes well. it was a bit of a major pain to trim down the mast cap to get it to fit. my old-style eye-bolt had also enlarged the hole at the one end – I still haven’t figured out how to fix that part, since the plastic cap doesn’t go deep enough inside to go past it. maybe I’ll use JB Weld or something.


  2. 3 Jeff Kline May 26, 2013 at 3:21 pm

    Good post. I was given a Sunfish, so that tells you something right there, Yes, it is in bad shape. A pre-1972 model I am thinking, based on what I’ve read in blogs, etc. anyway, I’ve finally figured out the mast is broke, it’s almost a foot too small in length. My question: try and find an aluminum tube that fits the right dimensions and have it cut to 10 feet, and then install caps top and bottom or just try and order a mast from some online company. (Sunfish parts are hard to come by in Central Florida.) Trouble, of course, is watching the budget. But still, I want it right. So if it is best just to buy one I’ll just save my money until I can afford it. Thanks. enjoy your blog.


  3. 5 John October 19, 2014 at 11:42 pm

    The 48″ placement of the cleat is that measured from bottom of cleat or from were the screws are. Looks like in the pic it’s the edge of the cleat touching the tape at 48″. Also you did just use screws. That should be good enough. Thanks for any replies


    • 6 my2fish October 20, 2014 at 6:54 am

      John, I’m not sure how picky they are – I’d make sure the entire cleat is below the 48″ mark (measured from the bottom of the mast). I used screws, with a dab of 3M 4200 (or caulk would work) to help seal things up.


      • 7 John December 7, 2014 at 6:21 pm

        Thanks for reply. Yes when I looked at the pic again I see it is below the tape thank you I will try this. It’s not for racing just for pleasure sailng but thanks.


  4. 8 timothy hart October 4, 2015 at 10:42 am

    Thad you can rent an exhaust pipe expander from Autozone that you can slowly expand the end of the mast tubing where it is necked down and it will make assembly much easier. T.J.

    Liked by 1 person

  5. 10 Frank A Miller June 6, 2021 at 1:23 pm

    would filling the top part of the mast with expandable foam (unlike the original cork) aid in flotation?


    • 11 my2fish June 6, 2021 at 1:38 pm

      Frank, it might help some… the downside is that Great Stuff or similar foam is typically open-cell foam, so it’d eventually absorb water if your mast isn’t sealed. So I’d try to make sure your base and top cap are sealed as well. other option is to just tie a gallon jug to the top of the mast or upper boom to help prevent the Sunfish from turtling.


  1. 1 how to upgrade a used Sunfish sailboat [video] | my2fish: a blog about sunfish sailing Trackback on February 8, 2021 at 10:21 am

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