Tuesday, November 20, 2018

Reparing Renegade's mast: shrink wrapped glass sleeve.

I didn't take photos during the glass sleeve and shrink wrap steps because I didn't want epoxy all over my cell phone, but basically the supplier, Soller Composites, has an excellent web site including a video of the sleeve/shrink tubing process:

It all seemed straight forward and I liked the idea that the shrink tubing would give a bit of uniform pressure to the sleeve while the resin kicked off. Sort of like vacuum bagging without the tedium of monitoring of the vacuum system for leaks.   I was also hoping that the addition of shrink tubing would translate into minimum sanding.  One thing that was an immediate plus was that after applying the shrink tubing over the epoxied area, it was sealed off and I could move the spar inside the garage while the resin kicked without fear of epoxy dribbling on something stored under the long, ungainly mast in my cramped, cluttered garage.

I allowed the resin to cure for several days, due to the cool temps in the garage.  When I was initially working with the sleeve material and tubing I learned a couple of things right off the bat.  First, one needs to cut the sleeve material a bit longer than the length required in order to allow for the size of the "tube" one is attempting to cover.  The larger the tube the longer the excess needs to be--as the sleeve expands, it grows shorter.  This probably should have been intuitive but I'm a bit hard headed and not what one would call the intuitive type. 

The next thing I learned is that the glass sleeve material is difficult to cut cleanly even with sharp scissors.  The photo above shows my result after the resin kicked and after I had removed the shrink tubing. The ends of the sleeve show the fraying of the fiberglass sleeve left by my scissors.  In retrospect I think a rotary cutter with a fresh, sharp wheel, and with the sleeve on a cutting board might produce a cleaner result.  I have some sleeve material left over so I can experiment with that aspect.  Live and learn.   Due to the size of this wing mast (~3.0 inches) I used packing  tape rather than a zip tie to secure the glass sleeve while wetting out the glass and  pulling up the shrink tubing.  That seemed to work ok.
A close up of the repaired area.  One can see the original split in the wood in the upper right hand side of the mast.

This photo shows the repair after a light sanding to remove the mare's tails. During the shrinking process I managed to burn through the shrink tubing with my old heat gun (set on the lower of its two settings).  In hindsight, my wife's hair dryer, with lower heat output, might have been better at this task.

A close up of the repair showing some unevenness in the resin coating.  It may, in part, be due to me working on a 45 degree F day rather than a 70 degree F day.  I did add more shrink tube to the burn through areas of shrink tube but I think the localized heat from my gun caused the resin to kick faster in those areas and hence the blotches and voids seen here.
Turning the mast over, one can see the luff groove slot which needs to be reopened.

Here is the slot after a judicious pass with the plunge blade of my multi-tool followed by running sand paper through the groove.  The repair will required a second coat of  resin and a final sanding, but all in all I think the repair will salvage the mast, and as is the case in all new things, I now have a lot to think about before my next attempt at sleeving/shrink wrapping spars or tubes.

1 comment:

  1. Have you ever used 'peel ply'? You place it over a normal cloth / resin application. When the job has cured you peel or more like rip it off. It leaves a very smooth surface that requires minimal sanding. It also stops resin running and dripping. I used peel ply on a large overhead repair around the keel on my yacht 'Mariner' and the peel ply helped any resin defy gravity - amazing stuff.