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post #23 of Old 03-23-2009
Telstar 28
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You're really much better off doing this from the topside and removing the exterior skin for a lot of reasons.
  • First, trying to work in the confines of the v-berth will make your life hell. Also, any spills and such will need to be cleaned up immediately or you'll have a second real big project on your hands. You can setup scaffolding around the bow of the boat and get much of the work done from off the boat.
  • Second, trying to get the core material to laminate to the outer skin properly without vacuum bagging is much easier if gravity is on your side.
  • Third, getting the fiberglass to adhere and laminate to the core material is much easier if gravity is on your side.
  • Fourth, clean up will be much simpler, especially if you tent the front half of the boat and lay tarps down underneath it... cleaning up the interior is a royal PITA.
  • Fifth, the work will go a lot faster if you're working from the top down, rather than the bottom up. It will probably take you four-to-five times as long to do it from the inside as it does from the outside.
So here are my questions:
? Are we being impetuous and foolish to consider a substantial fibreglassing job in the wet Vancouver spring? If we have good heating and ventilation, will the high level of ambient air moisture be detrimental to the results, even if we are inside? Apart from the leaking pulpit, the boat is remarkably dry - there's no musty smell at all, no mold or general dampness.
If you have the boat well covered, it shouldn't be too much of an issue.
? How many poor fishies are we going to kill as we weren't intending on hauling? We have a shop vac and we're hoping to set up plastic sheeting to keep any sanding residue from escaping the forward hatch or into the salon.
You really need to do this with the boat out of the water. It will go a lot faster if the boat is on the hard, since you'll have better access to the boat.

? Where can we find balsa end-grain matting in the Vancouver area?
You can use end-grain balsa, Contour-Core, Airex foam or Divinylcell foam. Personally, I'd go with Divinylcell foam for this. Make any places you're going to be attaching hardware thick SOLID FIBERGLASS instead.

? How big a section can we do at one time? With gravity working against us, I'm concerned that when we're reattaching the core that the balsa will sag a bit, resulting in poor bonding to the outer layer of fibreglass, and again with the inner layer to the core.
Work from the outside... it is much easier, faster, safer.

? What on earth do I do about the forestay chainplate? Can it stay in? Can we simply cut closely around it, remove all core, and fill the edges with epoxy, and then glass around it? Or as we're using a polyester resin (I think) will this have adverse repurcussions attaching to the polyester resin, or in future repair work? This is on the assumption (possibly wrong) that its mount is dry. Ack!
The repair has to be strongly attached and bonded to where the forestay chainplate is... without better photos of the chainplate and bow, I can't say whether you need to remove it or not. Is the area beneath the chainplate cored or solid glass? If it is solid glass, you'll probably want to remove the chainplate, and then run the 12:1 taper for the outer laminate repair over that area so that the new fiberglass strongly connects to the chainplate base.

? What weight of glass will we need? How many layers will need to be applied? How many layers can do be done at once without heat buildup becoming an issue?
Cut out a small section of the rotten deck using a small hole saw, say 1" in diameter... that will give you an idea of how thick the laminate needs to be. You can glass probably about 1/4 thick at a time without heat being a major problem. Any thicker than that, there are other problems you'll run into IMHO.

? This is probably a ridiculous question, but should we avoid walking on the foredeck completely without the core and inner layer?
Ummm... YES, DO NOT WALK ON THE DECK until it is repaired.

Advice appreciated for this nervous newbie!
Finally, I would highly recommend that you use EPOXY RESIN for all of the repairs, and use bi-directional roving and cloth, instead of CSM for the repairs. The reason for this is very simple—strength.

Roving and cloth are far stronger than CSM, since the long continuous fibers in fiberglass create the strength in the laminate. CSM is all short strands, and great for building bulk, but doesn't really create strength.

Most of the bonding between the existing boat structure and a repair is dependent on secondary bonding characteristics—or the adhesive strength of the resin. Epoxy resin has far greater secondary bonding characteristics and is far more forgiving to use than vinylester or polyester resin. It is generally also stronger than either of the other two resins.

Any areas that overlap the repair and existing fiberglass should be ground and tapered to at least a 12:1 taper for the thickness of the glass there. If the glass is 1/4" thick, the ground tapered area should be at least 3" wide—12 x .25.

Any areas where you're going to be grinding fiberglass should be well washed with a strong dewaxer/degreaser. Interlux Fiberglass Prep Wash 202 is a good choice to use. I would recommend washing with TSP first then using the 202... the reason for washing it is simple, you don't want the grinder/sander embedding grease or wax in the ground areas, as that will compromise the repair's bond to the existing fiberglass and weaken the repair considerably.


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Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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