Dinghy attachment to boat deck

You are right, get another installer.

What are your dinghy chocks made of?
Could you glass/epoxy them to the deck?

While it is never a good idea to allow, water intrusion into that core will not be an issue as it would only penetrate disturbed cells where the holes are and not spread further. If it were ever to freeze and expand it could cause delamination but your location makes that hopefully unlikely

Through bolting does tie both skins together and provide better holding strength but there still is an issue of point loading which should be addressed. The simplest way is a sleeve of aluminum or delrin that the bolt passes through to avoid crushing the core.

If you are trying for the "clean" look you could bury a plate of material inside the core that can be drilled and tapped. This will require some glasswork and fairing and also re-glassing over and beyond the insert to spread the load properly. It is more costly but by far the best way to fasten heavy loads into a core. I use that particluar brand of core material (and others) quite frequently so feel free to PM me and I would be happy to share more details.

I agree. Dig out a volume of FRP, add a thick piece of aluminum to be drilled & tapped at each attachment point, and cosmetically finish.

If you do follow the route of inserting a block or plate of metal to be tapped, I'd suggest stainless rather than aluminium. The chances are that the chocks would be attached with stainless bolts and the aluminium would rot really quickly in the presence of seawater.

I agree completely, while it is often done with tower mounting points, at best you'll need an impact driver to remove stainless bolts after a year or less, at worst, a drill to remove the heads and pray you'll have enough left to grab with vice-grips. I've used readily available G10 sheet (1/2" or thicker depending on load) with great results. Non-corrosive and bonds well with resins when prepped (sanded) properly.

I don't know the details of your situation but there are several possible options. While it would structurally be better to install the plate on the underside of the core, remembering to add-in crush proofing above the plate where core is left (if any), glassing overhead isn't a happy chore. You could dig down from the topside, insert the plate/crush proofing and re-glass and fair topsides. You HAVE to glass this out over a much larger area than the plate itself or you could pull the whole works out!

ALl this is based on the need for a smooth, hardware-free surface on the underside. If you have a false overhead in the ceiling below where you plan on mounting the plates, the job is much simpler! 5200 the plates where you want them, drill the holes oversized for the bolt inserts (crush-proofing) and glue them in. You can get some rubber mushroom caps to keep the water out when the dinghy is removed.

Bill

hard to say not knowing what kind of removable chock you're going to install.

I guess there is some kind of a flush plate for the chock to be attached to.

in any case, i would not screw the chock but thru bolt them. Screws in glass and foam core is a real lousy idea!!!

with closed cell foam core, you could get away with using 5200 aroudn the bolts but the right approach is to drill, remove some core, fill with resin/filler then drill again.

what is under the deck? if a headliner, it's work removing and install a backing plate. Alum would be fine if you are thru bolting.

if you don't' have any access under the deck, you could use SS. while they don't' spread the loads as well as a plate, most of the efforts are lateral and toggles will be fine.

again, it really depends on the type of chocks you're going to use.

Just make darn sure that the insert is designed so that the torque required to remove a corroded fastener (because it will corrode) does not cause it to rotate in the core and create a much more difficult situation.

reason i was asking was to figure out how are they removable. there should be some kind of thin, low profile plate on which the chocks are attached. I just hope they are no planning on having removable fasteners thru the decks which eventually is sure to lead to water intrusion.

as you just saw with what your installer was planning on doing, being reputable or recommended is not a guarantee of a job well done

one way to make it removable would be to have SS inserts in the deck, in which a male part latch in. similar with what you see with removable railing on swim platform. with the male part fitting in the recessed fitting on the deck, you can use D rings to strap down the tender to the deck, securing both the tender and also the chocks.

i don't' know i explained it right... imagine a drink holder and beer bottle sliding in... the beer bottle can't move sideways but the tender straps will hold it down in the hole.

that will result in a truly removable cradle with nothing to trip over on deck.

I built a cradle of out starboard for the waverunner we added to the boat i'm running and i'm looking into this to make sure the cradle doesn't slide around, yet leaves no brackets when removed.

Hi,

I would be very keen to know what those screws/bolts were attached to on the other side too.

I would also not be happy if I were the client and the guy doing the job didn't take enough care to clean the 5200 out of the screw slots very well if at all.

There is product called tef-gel that will keep the metal from corroding. It is pretty pricey at $20 for a small tube but well worth it.

There is a human condition that leads us to have faith in the spiritual powers and their physical incarnation in the form of potions and magic sauces.

When metallic components are forced to cohabit in the presence of saltwater, they will, as surely as headaches follow cheap liquor, stick, gall, and create bonds such as no marriage counselor would ever allude.

Sounds like you already started on the cheap liquor

No, still in the office where it feels like late Friday afternoon.