martin 'hoff

Sealing footstrap holes

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On the stern of a cat, the drill holes to fasten a footstrap are hard to seal

  • they're often drilled through a spot with foam
  • the footstrap ends are webbing; and the webbing gets in the damn way to caulk from outside
  • if caulking gets into the screw threads you may lock the nut once installed
  • access on the inside of the hull is maximally awkward

is there a way? 

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Drill the holes over sized. Fill with high density thickened epoxy. Either suck up the frustration of thrubolting or Drill and fit #12 self taping screws. Your weight on a couple of #12’s is insignificant if the hull location is decent.  Before installation take a countersink bit and make a 2mm deep countersink on the webbing side of the hull. This is where the waterproofing happens. Think about the sealant like an o-ring. You need only a little bit of sealant to make it watertight. Decks leak when people don’t do the countersink thing. 

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Don't drill hole  Make a glass or carbon padeye about 2" in diameter. Glue to skin.

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11 hours ago, Zonker said:

Don't drill hole  Make a glass or carbon padeye about 2" in diameter. Glue to skin.

If going with tapped padeyes, make sure the plate is well made, and the bottom layer (closest to boat) is tight-knit 0/90. Have had repeated issues with tapped padeyes with handles attached (on watertight bulkhead hatches) coming off due to bottom layer of carbon delaminating from the rest of the padeye.

 

HW

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11 hours ago, Max Rockatansky said:

Not sure I understand your post. A good friend has a top of the line DNA latest a-cat. I'm on a slightly more mundane Nacra 15 FCS.

 

On 10/17/2020 at 10:12 PM, Zonker said:

Don't drill hole  Make a glass or carbon padeye about 2" in diameter. Glue to skin.

I kind of like that idea, but when I've done it (with G10 offcuts actually) I ended up with a thick pad that had nasty borders – not nice on knees and toes.

Also, I probably overdid it because I wanted to embed a nut in there. You say a pad-eye that's strong/thick enough for self tapping? Any videos/howtos on getting something low profile and smooth? Looks are secondary, but sharp edges are truly unfriendly.

Also – keep in mind that some of the strap attachments are on a curved surface, so these pad-eye will be a bit of a custom job. Easy if I mask the area and build it up in-place.

 

On 10/17/2020 at 7:20 PM, CaptainAhab said:

Drill the holes over sized. Fill with high density thickened epoxy. Either suck up the frustration of thrubolting or Drill and fit #12 self taping screws. Your weight on a couple of #12’s is insignificant if the hull location is decent.  Before installation take a countersink bit and make a 2mm deep countersink on the webbing side of the hull. This is where the waterproofing happens. Think about the sealant like an o-ring. You need only a little bit of sealant to make it watertight. Decks leak when people don’t do the countersink thing.

Let's say I do the countersink. How do I get enough sealant in there, and not get gobs of it in the threads – so that I may one day remove it? Remember, there's a ~4 layer of webbing in the middle! That's the part that gets me.  

 

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You haven’t described the details. I’m imagining some webbing(a few layers) The fastener(screw or bolt) goes thru a washer, thru the webbing, a bit of sealant, and into the deck. Assembly the whole thing. Screw in or push in your fastener. Then pull it out a bit. Squirt the goop between the webbing and deck only around the fastener( fo not make a mess. The goop stays in the    Countersink. A little bit will get on the last threads. You should use a polysulfide sealant like 3M 101, life caulk or a lower strength polyeurethane made by Sika. Do not use 3M 5200. If you can’t get it out even if you gooped all of the threads, you used the wrong product. 

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