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Core Repairs and Stanchions

Question:
Encouraged by your enthusiasm for the design, I recently bought an early, demountable Dragonfly 25 but have a few issues I'd like your opinion on.

Quite a lot of the balsa core has taken on water and needs replacing and I'm wondering how to tackle that, and as I have 2 young kids, I was also thinking about putting lifelines on (per my wife's request), but was wondering how? I'm also considering access hatches for the amas as part of the project. It seems like a waste of space to not use them for fenders, docklines, sail covers, etc. The beauty of a demountable boat of this size is that I can get the amas into my garage to work on and so avoid long trips to a boatyard where I'd have to work under a tarp if it rains. Also would you have any suggestions for the blocking under the stanchions? I have some old growth cedar I could saturate in epoxy and use with a vertical orientation as is done with the balsa core.

Thanks, AZ

Answer:
Re the balsa, it's hard to advise you specifically without knowing where you are doing the repair. But in general, for a low-budget repair, I would open the skin from the outside (I would typically use a high speed grinder for surgically removing the old skin) after tapping around the area to identify the limit of the soft core. Then scrape out the old balsa and dry the area thoroughly with a hair dryer. I would then bond in new foam (Corecell™ or Klegcell®) and strap it over with temporary wood straps laid longitudinally to promote fairness, held in place with some good duct tape. On flat deck areas, I would typically use slightly thinner foam to allow for adding a 3‑mm ply over the foam, as this provides a flat, fair surface that better distributes future loads. If vacuum bagging is not practical for the location, you might (for the sides etc) want to use ply temporarily over the top (wrapped in plastic as a release film) to create a smooth fair surface about 116" below the final surface, while the epoxy cures. For the deck, then use two layers of 6‑oz FG cloth at least, oriented in somewhat different directions. On some occasions, I have actually been able to rebond the old glass deck surface back in place over the new foam! First grind off the underside of the removed part. Thickened gap-filling epoxy can then permit its refitting if one gets organized to press the panel down flush with the surrounding deck using temporary, exterior lengths of timber for surface alignment.

Once cured, you grind out the join (about 2" wide) almost to the foam and lay in 2‑3 layers of mat, with one finishing layer of cloth to relink the parts. You'll get to feel like a plastic surgeon ;-)
For small, less critical areas of delamination, I have had good success with a system of simply injecting slightly thickened epoxy into holes spaced about 1.5" (40 mm) apart.
Using a plastic injection syringe (available from a pharmacy - less needle), tests showed that I was able to rebond at least 80% of the delaminated surface, with pools of epoxy overlapping each other under the once-loose skin. I would drill the holes several days before the injections and push in warm air to speed the drying. See photo for repair that combined both methods.
(Interestingly, although I've been fooling with this for over 15 years, I see that the WEST System manual now shows something similar, so I'm pleased to see we're on the same track).

Also check where the akas sleeve into the amas. This connection can show cracks after a few season, so I would redo these using long tows of CF over the sleeve on the inboard edge, spreading out the long strands and fibres over the inner ama side and epoxying in place—a system I use on the W22.

While you're about it, also check the waterstays from end to end, particularly where the wire enters the end fittings. I would put 9‑10 mm wire and fittings up forward: less aft.

I would not use end grain cedar for deck stanchions, as it will split too easily. You'd need some good marine ply 12‑19 mm thick under stanchions but to be perfectly honest, I am not in favor of such things as they would not be reliable enough in my view. If you throw your weight against a stanchion with the leverage it provides, the pad will likely break out of your lightweight deck skin anyway so the security is false.

As far as hatches in the amas, you first have to accept that these will NOT be 100% watertight for very long so a little water will now enter. You should also avoid installing a hatch that is more than about 70‑75% of the deck width and even then, you'll need to add some longitudinal stiffening under the deck at each side of the hatch, to compensate for the lost deck strength. Take this stiffening at least a foot past the opening, too. Limit what you stow there anyway as you want to keep them buoyant (to stay light and responsive to its buoyancy) and also avoid any need to open them while at sea—when they should always be closed tight.

Hope this helps and good luck with the project

Mike


Re: Kids safety and Stanchions etc.

I know this goes beyond 'a construction issue', but perhaps these personal thoughts on kid safety on a small tri, will save you the construction work involved in fitting stanchions.

It depends on what sort of sailing or cruising you plan to do and where. I've sailed my D25X with young kids many times and the boat stays so flat and stable that I really don't consider it anything close to the risk of a heeling and lurching monohull. Motion acceleration is certainly quicker on a multihull, but the distance moved and heel angles are far less. Kids adapt quickly to this.

Personally, I'd prefer to 1) limit when to sail with young kids and 2) then use safety lines clipped to solid lifejacket straps (attached to a safe spot for lifting the full weight) capable of lifting at least 3 times the weight of the child. (The tether should be attached sufficiently inboard and be of such a length that the child cannot reach closer than about 12" from the edge of the boat, so eliminating any chance of going overboard.) Most kids 6 and over are far LESS likely to fall over than clumsy, unfit adults and personally, I found the risk very low anyway. Of course, one needs to practice MOB routines often and teach them to your crew, including your wife. Picking someone up from a small tri is quite different from the same exercise for a monohull. First, you need to respond quicker and turn back asap, as you can travel very quickly away from the spot. (A GPS with a MOB button can help here if immediately accessible). But once back in sight, it's relatively easy to circle the MOB with a trailing line and cushion that they can catch and haul themselves close. Lifting them over the side of the ama (without lifelines in the way) is then MUCH easier than hauling them up a monohull side. In fact, I had a drop down rope sling that made it possible to come aboard unassisted. Practicing is a must though as only then can you see what works best for each boat. I had both a loose buoyancy cushion to launch slightly upwind like a frisbee plus a reel of line with another cushion attached that I could immediately throw over the stern and with one crew watching the target while the helmsman tacked or gybed, fairly rapid pickups were possible. One can circle around and pick up, as for a waterskier. I would quite often lose a cap overboard when wind took it off and even single-handed, could tack or gybe around and pick it up over the side of an ama before it sank.

You also learn how to tack and put the boat into a hove-to state. You leave the jib cleated (though slightly eased off) but free the mainsail completely—then tack and leave the jib backed. The boat then makes only about 1 knot and gives time to think and plan the next step. The closest I EVER came to an actual accident with a youngster on board (after 20 years in small trimarans) was when the child was down in the cabin and I was hit with a vicious downdraft that put the boat at about 45 degrees and nearly flipped it. I learnt a lot that day, including the fact that with super high load like that on the mainsail, I was quite unable to release the main! Since then, I arranged an easy-to-release Spinlock cleat with a extension bonded on, that even a foot could release. The greatest risk to people and kids on board, are being hit with a gybing boom or getting caught up in a fast running jib sheet or fingers in a winch. The boat is so beamy and stable, that I never felt going overboard was the main risk. Kids were very safe on the windward tramp I felt and out of the way of the boom and ropes. Adding stanchions might even increase the hazards, as you'd certainly have to hop over them on a few occasions, as when docking and no doubt, they'd get in the way of (and probably foul) sheets for large foresails or spinnaker.

It's your call but those are my thoughts. Unless you have kids who are prone to accidents, do not like to follow instructions or very hyperactive, then I would first start sailing with them in moderate, steady conditions and see how the boat behaves before installing stanchions that give a false sense of security. But on a monohull ... yes sir ... I would indeed have stanchions!

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